The Lichen Genus Sticta (Lobariaceae, Peltigerales) in East African Montane Ecosystems

The lichen flora of Africa is still poorly known. In many parts of the tropics, recent studies utilizing DNA methods have revealed extraordinary diversity among various groups of lichenized fungi, including the genus Sticta. In this study, East African Sticta species and their ecology are reviewed using the genetic barcoding marker nuITS and morphological characters. The studied regions represent montane areas in Kenya and Tanzania, including the Taita Hills and Mt. Kilimanjaro, which belong to the Eastern Afromontane biodiversity hotspot. Altogether 14 Sticta species are confirmed from the study region, including the previously reported S. fuliginosa, S. sublimbata, S. tomentosa, and S. umbilicariiformis. Sticta andina, S. ciliata, S. duplolimbata, S. fuliginoides, and S. marginalis are reported as new to Kenya and/or Tanzania. Sticta afromontana, S. aspratilis, S. cellulosa, S. cyanocaperata, and S. munda, are described as new to science. The abundance of new diversity detected and the number of taxa represented by only few specimens show that more comprehensive sampling of the region may be needed to reveal the true diversity of Sticta in East Africa. More generally, our results highlight the need for further taxonomic studies of lichenized fungi in the region.


Introduction
Tropical mountains, and especially their forests, are hot spots of biodiversity and endemism [1][2][3][4]. In East Africa, montane regions, such as the ancient Eastern Arc Mountains which range from southern Tanzania to Kenya, and the much younger volcanic mountains, such as Mt. Kilimanjaro in Tanzania and Mt. Elgon at the border of Kenya and Uganda, are surrounded by vast stretches of arid woodlands and savannas [5,6]. Still, especially the humid upper windward slopes of these mountains have provided refuge for the montane rainforests already for millions of years [6,7]. During this time, climatic induced fluctuations in the areal extent and isolation of moist montane forests have generated remarkably high levels of diversity and local endemism [1,3,6,8,9] in what is now known as the Eastern Afromontane biodiversity hotspot [10,11].
In this study, we review Sticta species and their ecology in the montane regions of Kenya and Tanzania using the barcoding nuITS genetic marker and provide a wealth of new information on their diversity and ecology.

Study Locations and Sampling
Specimens were collected from four mountain regions in East Africa, including the dormant volcano Mt. Kilimanjaro in Tanzania, the Taita Hills, and Mt. Kasigau, which represent the northeastern end of the Eastern Arc Mountain Range in Kenya, and Mt. Elgon at the border of Kenya and Uganda. All the mountains are less than 400 km from the equator and separated from each other by wide semiarid plains with a tropical climate with two distinct rainy seasons.
The high Mt. Kilimanjaro (5895 m) supports a wide range of natural vegetation types from natural savanna to alpine Helichrysum heath, in addition to which human activity has produced a variety of additional habitat types. The sampling in the Kilimanjaro region was done in 2016-2017 along five replicate transects on the southern and southeastern slopes of the mountain. The 65 sampling plots represent the following 13 natural and disturbed ecosystems, with 5 replicate plots in each ecosystem type: natural savanna and maize fields (800-1100 masl), lower montane forests, traditional Chagga home gardens, commercial coffee farms, and grasslands (1100-2000 masl), montane Ocotea forest and selectively logged Ocotea forest (2100-2800 masl), upper montane Podocarpus forest and secondary forest dominated by Erica excelsa as a result of repeated forest fires (2800-3100 masl), subalpine Erica trimera forest and fire disturbed E. trimera forest/shrubbery (3500-4000 masl), and alpine Helichrysum heath (4000-4650 masl). For a more detailed description of the sampled environments on Mt. Kilimanjaro, see [13,34]. On each plot, lichen specimens were collected from a 5 × 20 m central plot and along two 50 m transects. Additionally, also a larger 20 × 50 m plot was sampled for branches that had dropped from the canopy.
The Taita Hills consists of three mountain massifs: Dabida, Mbololo, and Sagalla. While the potential natural vegetation on the moist upper slopes consists of evergreen Ocotea forest, long-lasting and intensive human influence has fragmented the indigenous forest into small and often heavily disturbed, isolated patches [35][36][37]. The sampling of lichens in the Taita Hills took place during several field trips mainly in 2009-2011, encompassing all the main remaining forest fragments: On the Dabida massif, fragments of indigenous montane forest mainly occur on the highest peaks and ridges, including Ngangao (120 ha), Chawia (86 ha), Yale (16 ha), Fururu (8 ha), Macha (3 ha), Mwachora (2 ha), Vuria (<1 ha), and Shomoto Hill (<0.2 ha) [36,38]. Mt. Sagalla in the southeast harbors a small indigenous forest patch of 2 ha surrounded by plantation forest, while

Results
Of the studied 373 Sticta specimens, a good quality ITS sequence was obtained from 233 specimens. ITS variant information for each sequenced lichen specimen is listed in Table A1.

Phylogenetic Analyses of the Specimens
The Bayesian analysis of the nuITS region of the genus Sticta revealed that several of the morphologically identified species included representatives of more than one phylogenetic lineage ( Figure S1).

Specimens with Soredia or Pustules
Based on the previous literature from the region [12], the sorediate specimens were identified as either S. sublimbata or S. limbata. All specimens with soredia that were collected from the lower to middle montane forest zones formed a well-supported (PP = 1) clade together with S. sublimbata specimens from Réunion and Japan ( Figure 1). However, the sorediate-pustular specimens from higher elevation habitats did not group together with S. limbata, but were closely related to a previously sequenced S. umbilicariiformis specimen from Rwanda ( Figure 2).  Figure S1A,B). The colored polygons (rectangle, triangle) in the tree show the distribution of the ITS variants in the studied regions and ecosystem types: On Mt. Kilimanjaro, the different habitats are indicated by color and grid; the width of the rectangle indicate the number of sample plots in which the taxon was present in each ecosystem type (square = 1). In the Taita Hills, each triangle indicates presence in one forest fragment and on Mt. Kasigau in one sampling transect. The grey boxes show the total abundance and distribution of the species, also including the data from unsequenced specimens. Stronger support (PP > 0.9) for a clade is indicated with a thicker branch. The scale refers to nucleotide substitutions per site.  Figure S1A,B). The colored polygons (rectangle, triangle) in the tree show the distribution of the ITS variants in the studied regions and ecosystem types: On Mt. Kilimanjaro, the different habitats are indicated by color and grid; the width of the rectangle indicate the number of sample plots in which the taxon was present in each ecosystem type (square = 1). In the Taita Hills, each triangle indicates presence in one forest fragment and on Mt. Kasigau in one sampling transect. The grey boxes show the total abundance and distribution of the species, also including the data from unsequenced specimens. Stronger support (PP > 0.9) for a clade is indicated with a thicker branch. The scale refers to nucleotide substitutions per site. Our specimens identified as S. fuliginosa, based on the previous literature from the region [12], fell into six different clades ( Figure S1). These include three previously described species of the Sticta fuliginosa morphodeme, i.e., S. ciliata, S. fuliginoides (Figure 3), and S. fuliginosa ( Figure 2). Additionally, four specimens (Sticta sp. B) representing two different ITS variants formed a well-supported (PP = 0.995) clade with one sequence obtained from a specimen from Rwanda identified as S. ciliata, forming a sister clade to S. parvilobata, a recently described species [23] from Puerto Rico ( Figure 3). Additionally, three specimens (Sticta sp. A) were closely related to S. catharinae, another recently described species [22] from Bolivia ( Figure 3). Nineteen specimens (S. aspratilis), mostly rep- Figure 2. Phylogeny of the Sticta umbilicariiformis-fuliginosa group based on the nuITS region. The colored polygons (rectangle or triangle) in the tree show the distribution of the ITS variants in the studied regions and ecosystem types: On Mt. Kilimanjaro, the different habitats are indicated by color and grid; the width of the rectangle indicate the number of sample plots in which the taxon was present in each ecosystem type (square = 1). In the Taita Hills, each triangle indicates presence in one forest fragment and on Mt. Kasigau in one sampling transect. The grey boxes show the total abundance and distribution of the species, also including the data from unsequenced specimens. The proportions of different structures (pustules, isidia, or just apothecia) among the specimens with specific ITS variants are indicated with pie charts for the new species and S. umbilicariiformis. Stronger support (PP > 0.9) for a clade is indicated with a thicker branch. The scale refers to nucleotide substitutions per site.

Fertile Specimens without Symbiotic Propagules
Three frequently fertile Sticta species that lack symbiotic propagules had previously been reported from the region, i.e., S. ambavillaria, S. kunthii, and S. tomentosa [12,26], and specimens resembling the descriptions of all these taxa were also present in our material. All specimens matching the description of S. tomentosa fell into a well-supported (PP = 1) clade, which mainly consists of S. tomentosa specimens from Colombia and Hawaii ( Figure 1). All other specimens belonged to the S. umbilicariiformis-fuliginosa group ( Figure 2). In the additional analysis, six specimens formed a well-supported (PP = 0.992) clade (S. munda); however, many morphologically similar specimens, i.e., fertile with pubescent or nodulous apothecial margins and with smooth, scrobiculate, foveolate to pitted upper surface, were mainly placed in the poorly resolved S. umbilicariiformis group, with some specimens in the well-supported (PP = 1) S. aspratilis clade.

Specimens with Laminal Isidia (Sticta fuliginosa Morphodeme)
Our specimens identified as S. fuliginosa, based on the previous literature from the region [12], fell into six different clades ( Figure S1). These include three previously described species of the Sticta fuliginosa morphodeme, i.e., S. ciliata, S. fuliginoides (Figure 3), and S. fuliginosa ( Figure 2). Additionally, four specimens (Sticta sp. B) representing two different ITS variants formed a well-supported (PP = 0.995) clade with one sequence obtained from a specimen from Rwanda identified as S. ciliata, forming a sister clade to S. parvilobata, a recently described species [23] from Puerto Rico ( Figure 3). Additionally, three specimens (Sticta sp. A) were closely related to S. catharinae, another recently described species [22] from Bolivia ( Figure 3). Nineteen specimens (S. aspratilis), mostly representing the S. fuliginosa morphodeme, but also including some fertile specimens without isidia, formed a well-supported (PP = 1) clade within the S. umbilicariiformis-fuliginosa group ( Figure 2).   Figure S1C). The colored polygons (rectangle, triangle) in the tree show the distribution of the ITS variants in the studied regions and ecosystem types: On Mt. Kilimanjaro, the different habitats are indicated by color and grid; the width of the rectangle indicate the number of sample plots in which the taxon was present in each ecosystem type (square = 1). In the Taita Hills, each triangle indicates presence in one forest fragment. The grey boxes show the total abundance and distribution of the species, also including the data from unsequenced specimens. Stronger support (PP > 0.9) for a clade is indicated with a thicker branch. The scale refers to nucleotide substitutions per site.

Specimens of the Sticta weigelii Morphodeme
The specimens belonging to the Sticta weigelii morphodeme, i.e., with cylindrical or flattened marginal isidia and often also with elongate lobes, were split into several different clades ( Figure S1). The specimens with cylindrical isidia fell into a clade with specimens identified as S. weigelii from different parts of the world; however, the smaller clade consisting of specimens identified as S. weigelii s. str. [58] only includes GenBank se-  Figure S1C). The colored polygons (rectangle, triangle) in the tree show the distribution of the ITS variants in the studied regions and ecosystem types: On Mt. Kilimanjaro, the different habitats are indicated by color and grid; the width of the rectangle indicate the number of sample plots in which the taxon was present in each ecosystem type (square = 1). In the Taita Hills, each triangle indicates presence in one forest fragment. The grey boxes show the total abundance and distribution of the species, also including the data from unsequenced specimens. Stronger support (PP > 0.9) for a clade is indicated with a thicker branch. The scale refers to nucleotide substitutions per site.

Specimens of the Sticta weigelii Morphodeme
The specimens belonging to the Sticta weigelii morphodeme, i.e., with cylindrical or flattened marginal isidia and often also with elongate lobes, were split into several different clades ( Figure S1). The specimens with cylindrical isidia fell into a clade with specimens identified as S. weigelii from different parts of the world; however, the smaller clade consisting of specimens identified as S. weigelii s. str. [58] only includes GenBank sequences from the Neotropics (Figure 4). The specimens belonging to the Sticta weigelii morphodeme, i.e., with cylindrical or flattened marginal isidia and often also with elongate lobes, were split into several different clades ( Figure S1). The specimens with cylindrical isidia fell into a clade with specimens identified as S. weigelii from different parts of the world; however, the smaller clade consisting of specimens identified as S. weigelii s. str. [58] only includes GenBank sequences from the Neotropics (Figure 4).  Figure S1D,E). The colored polygons (rectangle, triangle) in the tree show the distribution of the ITS variants in the studied regions and ecosystem types: On Mt. Kilimanjaro, the different habitats are indicated by color and grid; the width of the rectangle indicate the number of sample plots in which the taxon was present in each ecosystem type (square = 1). In the Taita Hills, each triangle indicates presence in one forest fragment. The grey boxes show the total abundance and distribution of the species, including also the data from unsequenced specimens. Stronger support (PP > 0.9) for a clade is indicated with a thicker branch. The scale refers to nucleotide substitutions per site.  Figure S1D,E). The colored polygons (rectangle, triangle) in the tree show the distribution of the ITS variants in the studied regions and ecosystem types: On Mt. Kilimanjaro, the different habitats are indicated by and grid; the width of the rectangle indicate the number of sample plots in which the taxon was present in each ecosystem type (square = 1). In the Taita Hills, each triangle indicates presence in one forest fragment. The grey boxes show the total abundance and distribution of the species, including also the data from unsequenced specimens. Stronger support (PP > 0.9) for a clade is indicated with a thicker branch. The scale refers to nucleotide substitutions per site. Specimens with at least some flattened isidia were divided into three different clades. The majority fell within the S. umbilicariiformis-fuliginosa group and formed a clade (PP = 0.665) closely related to S. munda, S. umbilicariiformis, and S. aspratilis ( Figure 2). One specimen was placed into a well-supported (PP = 0.992) clade comprised mainly of S. andina specimens (Figure 4), and four specimens (S. cyanocaperata) grouped together with S. caperata from Réunion and Madagascar ( Figure 5).  Figure S1F). The colored polygons (rectangle, triangle) in the tree show the distribution of the ITS variants in the studied regions and ecosystem types: On Mt. Kilimanjaro, the different habitats are indicated by color and grid; the width of the rectangle indicate the number of sample plots in which the taxon was present in each ecosystem type (square = 1). In the Taita Hills, each triangle indicates presence in one forest fragment and on Mt. Kasigau in one sampling transect. The grey boxes show the total abundance and distribution of the species, also including the data from unsequenced specimens. Stronger support (PP > 0.9) for a clade is indicated with a thicker branch. The scale refers to nucleotide substitutions per site.

Specimens with Marginal Isidia
Previously, two additional species with marginal isidia have been reported from the region, including S. cyphellulata and S. orbicularis [12]. Of the remaining marginally isidiate specimens, 18 clearly stipitate specimens formed a well-supported group with S. marginalis specimens from Réunion and Madagascar ( Figure 5), and 22 formed a well-supported (PP = 1) group with S. duplolimbata specimens from other parts of the world (Figure 4). Additionally, specimens with cylindrical, mainly marginal isidia, but with an otherwise unique appearance (S. cellulosa), formed their own clade (PP = 0.868) among several recently described species mainly from the Neotropics (Figure 4). Additionally, two small and poorly developed specimens (Sticta sp. D) grouped (PP = 0.765) together with S. isid- Figure 5. Clades with Sticta marginalis, Sticta sp. 2, and Sticta cyanocaperata in the Bayesian tree of the genus Sticta based on the nuITS marker region ( Figure S1F). The colored polygons (rectangle,triangle) in the tree show the distribution of the ITS variants in the studied regions and ecosystem types: On Mt. Kilimanjaro, the different habitats are indicated by color and grid; the width of the rectangle indicate the number of sample plots in which the taxon was present in each ecosystem type (square = 1). In the Taita Hills, each triangle indicates presence in one forest fragment and on Mt. Kasigau in one sampling transect. The grey boxes show the total abundance and distribution of the species, also including the data from unsequenced specimens. Stronger support (PP > 0.9) for a clade is indicated with a thicker branch. The scale refers to nucleotide substitutions per site.

Specimens with Marginal Isidia
Previously, two additional species with marginal isidia have been reported from the region, including S. cyphellulata and S. orbicularis [12]. Of the remaining marginally isidiate specimens, 18 clearly stipitate specimens formed a well-supported group with S. marginalis specimens from Réunion and Madagascar ( Figure 5), and 22 formed a well-supported (PP = 1) group with S. duplolimbata specimens from other parts of the world ( Figure 4). Additionally, specimens with cylindrical, mainly marginal isidia, but with an otherwise unique appearance (S. cellulosa), formed their own clade (PP = 0.868) among several recently described species mainly from the Neotropics (Figure 4). Additionally, two small and poorly developed specimens (Sticta sp. D) grouped (PP = 0.765) together with S. isidioimpressula but with a relatively long branch ( Figure 4).

Sticta with Green Algae
Previously, two Sticta species with a green algal photobiont have been reported from East Africa: Sticta dichotoma and S. papyracea/variabilis [12]. Only four such specimens were collected by us, all resembling the description of S. papyracea. However, in the phylogenetic analysis, the sequenced specimens did not group together with S. variabilis or S. dichotoma, but formed a clade (PP = 0.854) with some specimens from Madagascar ( Figure 5), identified as "Sticta sp. 2" by Simon et al. [25].
Ecology and distribution: Sticta afromontana is common, abundant and often fertile in the upper montane forest zone and present from lower montane forests to the ericaceous zone (1800-3510 masl) but has not been collected outside forest habitats. Sticta afromontana is particularly common on Mt. Kilimanjaro, where often the most abundant Sticta species, but also found in some Taita Hills forests. Epiphytic on tree trunks, branches, shrubs, and climbers. So far, only known from Tanzania and Kenya.
Selected specimens examined: Tanzania  Etymology: Sticta afromontana is one of the most common Sticta species in the studied afromontane region.
Ecology and distribution: Sticta afromontana is common, abundant and often fertile in the upper montane forest zone and present from lower montane forests to the ericaceous zone (1800-3510 masl) but has not been collected outside forest habitats. Sticta afromontana is particularly common on Mt. Kilimanjaro, where often the most abundant Sticta species, but also found in some Taita Hills forests. Epiphytic on tree trunks, branches, shrubs, and climbers. So far, only known from Tanzania and Kenya. Notes: Sticta afromontana can be distinguished from other Sticta species in the region by its flattened marginal isidia and lack of K reaction (strong and immediate yellow in S. andina), presence of moniliform secondary hyphae (not present in S. cyanocaperata), and usually cream to light brown lower surface and primary tomentum (usually dark brown in S. andina and S. cyanocaperata). Sticta xanthotropa, previously reported from East Africa, has a thin and fragile thallus (robust in S. afromontana), shorter ascospores (24-36 µm), and different substrate ecology (grows on rocks and soil) [32] than S. afromontana. A detailed description of S. andina is provided in [21]. Only one specimen of S. andina was identified from our material. It has a cyanobacterial main photobiont (Nostoc) and is characterized by flattened marginal isidia, yellowish-brown upper surface and dark brown lower surface with dark, short primary tomentum, and moniliform secondary tomentum. Chemistry: K+ yellow, C−, Pd−.
Morphologically, S. andina most resembles S. cyanocaperata; however, it can be easily identified based on the immediate, bright yellow K+ reaction in the medulla (S. andina is the only K+ species in our region). Sticta cyanocaperata also lacks the moniliform secondary tomentum present in S. andina.
Ecology and distribution: In other parts of the world (Columbia, Hawaii, Azores), S. andina has been reported to grow epiphytically in humid montane forests and in montane heathlands [21]. Our single specimen was collected from a moist montane forest on Vuria Mountain in the Taita Hills, and it shared an identical ITS sequence with a specimen previously collected from Hawaii (MT132671).
Ecology and distribution: Sticta aspratilis is relatively common, but not very abundant in any habitat type. It has a wide elevational range on Mt. Kilimanjaro, the Taita Hills, and Mt. Elgon, extending from lower montane forests to the subalpine zone (1450-3720 masl). In addition to primary forests, it has also been collected from disturbed habitats. Epiphytic, mainly on canopy branches, but also on tree trunks at more open sites, occasionally also on soil in the subalpine zone. So far, S. aspratilis is only known from Kenya and Tanzania.
Selected specimens examined: Tanzania Notes: Sticta aspratilis most closely resembles S. fuliginosa which, however, usually lacks the moniliform secondary tomentum that characteristically covers the lower surface of S. aspratilis. Fertile specimens may resemble S. kunthii, previously reported from East Africa, and fertile specimens of S. umbilicariiformis. However, the upper surface of S. kunthii is marbled with maculae and papillate [32], while S. umbilicariiformis usually has longer ascospores (33-40 µm) than S. aspratilis. ITS barcoding marker accession (GenBank): OP999548 (holotype). Description: Thallus irregular, 150-300 µm thick, attached to substrate from the lower side of thallus. Lobes loosely adnate to ascending, elongate or rarely palmate, up to 3 cm wide and 4 cm long, branching polytomous, margins entire to sinuose, usually abundantly isidiate. Upper surface middle to dark brown or occasionally lighter yellow-brown, moderately glossy, smooth to foveolate centrally, with a scrobiculate pattern of isidiate ridges and hollows, at least submarginally, but occasionally spreading over a large part of the upper surface. Upper cortex paraplectenchymatous, 30-50 µm and 3-5 cell layers thick, cells up to 15 µm in diam., the first layer of cells often smaller and brownish in color. Photobiont Nostoc. Photobiont layer 20-70 µm thick, with Nostoc cells approximately 9 µm in diam. Medulla 50-180 µm thick, with hyphae 2-4 µm wide. Cilia not present. Isidia abundantly present and congested, marginal, submarginal, and on the laminal scrobiculate ridges, dark brown to almost black, glossy, cylindrical to coralloid, occasionally present also on the lower surface where grey. Lower surface dark brown, occasionally lighter towards margins, smooth, thickly and densely tomentose throughout. Lower cortex paraplectenchymatous, brown, 25-70 µm and 3-5 cell layers thick, with cells 6-14 (20) µm in diam. Primary tomentum dark brown to almost black, composed of agglutinated hyphae. Secondary tomentum arachnoid, pale, composed of moniliform assemblages. Rhizines often present in small, scattered groups, clearly longer than tomentum, fasciculate, squarrose, dark brown and often with white tips. Cyphellae 13-50/cm 2 , cupuliform with a round pore and raised margins, larger may be more irregular and slightly urceolate, pore size very variable, up to 2.3 mm in diam.; cyphellar membrane cream-colored to slightly brown or yellow, 15-25 µm thick, composed of rounded, epapillose cells 5-12 µm in diam. Apothecia or pycnidia not seen. Chemistry: K−, C−, Pd−. Mycobank # MB847045 Species of Sticta lichenized with a cyanobacterium and characterized by its thick, brown lobes and tomentum, and the scrobiculate, isidiate ridges on the upper surface present at least near the margins. ITS barcoding marker accession (GenBank): OP999548 (holotype). Description: Thallus irregular, 150-300 µm thick, attached to substrate from the lower side of thallus. Lobes loosely adnate to ascending, elongate or rarely palmate, up to 3 cm wide and 4 cm long, branching polytomous, margins entire to sinuose, usually abundantly isidiate. Upper surface middle to dark brown or occasionally lighter yellow-brown, moderately glossy, smooth to foveolate centrally, with a scrobiculate pattern of isidiate Etymology: The specific epithet refers to the characteristic reticulate pattern of the upper thallus surface.
Ecology and distribution: Sticta cellulosa seems to be rare and is found mainly in the subalpine zone on Mt. Kilimanjaro (2990-3520 masl). It occurs in primary and secondary Notes: Well-developed specimens are easy to distinguish from other Sticta species based on their robust, often dark brown appearance, the isidiate scrobiculation at least along lobe margins, and thick dark brown tomentum of the lower surface. Poorly developed specimens may resemble other isidiate species with yellowish-brown upper surface, but can be distinguished on the basis of submarginal, cylindrical isidia.
3.2.6. Sticta ciliata Tayl. (Figure 10a) Sticta ciliata has a cyanobacterial main photobiont (Nostoc) and rounded lobes with laminal isidia. A detailed description of S. ciliata is provided in [20]. In our region, the two sequenced specimens of S. ciliata have small, approximately 1-2 cm wide and 0.5-1.5 cm long, loosely adnate, rounded, obovate lobes with abundant, laminal isidia on the grey upper surface. The lobes are revolute making them convex. The lower surface is pale with a tomentose base, but with the tomentum becoming scarce or absent towards the margins, and with flat, variably sized cyphellae. Lobe margins are often ciliate. Chemistry: K−, C−, Pd−.
In our region, four other species with laminal isidia are present: Sticta aspratilis, S. fuliginoides, S. fuliginosa, and Sticta sp. B. Our S. ciliata specimens are rather few and poorly developed, but Magain and Sérusiaux [20] describe their diagnostic characters: Fresh specimens of S. ciliata have delicate and usually ciliate thallus margins, especially in young thalli, and abundant tiny papillae over the cells of the cyphellar membrane, however, the regeneration lobules of all other isidiate species can also have marginal cilia, and the fine anatomy of cyphellae can only be studied from fresh and well-preserved material. In our material, S. fuliginosa and S. aspratilis usually have larger thalli with a tomentose lower surface and cupuliform to slightly urceolate cyphellae. Sticta fuliginoides has a funnelshaped base and usually occurs on higher elevations than S. ciliata. Sticta sp. B closely resembles S. ciliata in morphology and occurs in similar habitats. However, the material presently available is too scarce to allow a detailed morphological analysis to compare the two species.
Ecology and distribution: In other parts of the world, S. ciliata is known from Europe, Macaronesia, and possibly Colombia, where it grows as an epiphyte on tree trunks and on bryophytes, especially in well-preserved, humid forests [20]. The two confirmed specimens in our material were collected from moist montane forest, one from the Sagalla Mountain in the Taita Hills and one from the lower montane forest of Mt. Kilimanjaro. Both specimens were growing epiphytically on tree trunks. Sticta sp. B seems to be widely distributed in East Africa and has been collected from Kenya, Tanzania, and Rwanda, from similar moist lower to middle montane forests as S. ciliata.
Macaronesia, and possibly Colombia, where it grows as an epiphyte on tree trunks and on bryophytes, especially in well-preserved, humid forests [20]. The two confirmed specimens in our material were collected from moist montane forest, one from the Sagalla Mountain in the Taita Hills and one from the lower montane forest of Mt. Kilimanjaro. Both specimens were growing epiphytically on tree trunks. Sticta sp. B seems to be widely distributed in East Africa and has been collected from Kenya, Tanzania, and Rwanda, from similar moist lower to middle montane forests as S. ciliata.  Description: Thallus rosetteform, (140)200-470 µm thick with thickenings on the lower side clearly visible in the cross-section, closely adnate centrally, loosely adnate marginally. Lobes elongate, polytomously branching, up to 5.5 cm long and 2 cm wide; margins often crisped, with darker, mostly flattened isidia, occasionally also with phyllidia. Upper surface is usually fawn to yellowish brown, occasionally light grey wavy to slightly Notes: In shady habitats, S. cyanocaperata may have a rather different appearance in having a light grey upper surface, thin thallus, few isidia, and poorly developed lower side tomentum. However, such specimens can still be identified on the basis of the characteristic lower side ridges and lack of moniliform secondary tomentum. The closely related S. caperata most commonly has a green algal primary photobiont. The cyanomorph of S. caperata reported from Réunion [25] differs from S. cyanocaperata in having a marbled upper surface. Sticta xanthotropa, previously reported from East Africa [12], is distinguished for example based on the pale cream-colored to yellowish lower surface [32]. The most closely resembling species in the region with similar flattened marginal isidia and yellowbrown upper surface is S. andina which can be recognized due to the instant and strong K+ yellow reaction of the medulla.

Sticta duplolimbata (Hue) Vain. (Figure 10b)
Sticta duplolimbata has a cyanobacterial main photobiont (Nostoc) and marginal isidia. A detailed description of the species is provided in [59]. In our region, the species is characterized by loosely adnate, elongate, and most often light grey lobes with rounded apices, dark, mainly marginal cylindrical to coralloid isidia, and dark marginal cilia which, however, are not always present. The lower side is abundantly tomentose, with tomentum reaching the lobe margins, and usually pale but sometimes even dark brown. Cyphellae are conspicuous, raised, and distinctly urceolate with a small opening. Chemistry: K−, C−, Pd−.
Sticta duplolimbata is easy to distinguish from the other Sticta species in our region, especially by the dark cilia usually present at the rounded lobe apices and distinct, urceolate cyphellae. Galloway [59] mentions that S. duplolimbata has "lobes arising from short stalk"; however, this is not visible in most of our specimens, which are usually attached to their substrate by the tomentum of the central parts of the lower surface.
Ecology and distribution: In other parts of the world, S. duplolimbata is mainly known from the Western Pacific region [59]. Abundant on tree trunks, climbers, and canopy branches in lower and middle montane forests on Mt. Kilimanjaro, with fewer specimens from upper montane forests, Chagga home gardens, and moist montane forests of the Taita Hills (1800-3060 masl).
3.2.9. Sticta fuliginoides Magain and Sérus. (Figure 10c) Sticta fuliginoides has a cyanobacterial main photobiont (Nostoc) and obovate lobes with laminal isidia. A detailed description of the species is provided in [20]. In our region, S. fuliginoides is characterized by the obovate lobes, ascending from a single attachment point. The lobes are usually up to 2.5 cm in diam and have a funnel-like base. The upper surface is grey, brown or yellowish-brown, smooth to strongly reticulate especially in ageing thalli, and with dark, mainly laminal, cylindrical to coralloid isidia, often developing into stalked lobules. The lower surface is white or beige, with abundant tomentum near the attachment point, but often etomentose towards the margins. Cyphellae are variable in size, usually urceolate and dome-like and raised especially towards the thallus margin, and if cupuliform, with a distinctly raised margin. Chemistry: K−, C−, Pd−.
Poorly developed thalli and/or specimens collected from suboptimal habitats may often have only one obovate-palmate ascending lobe with laminal isidia, and a mostly etomentose lower surface with pronounced cyphellae. In well-developed thalli, the ascending lobes usually have a funnel-shaped base quite distinct from those of other Sticta species with laminal isidia. Based on our phylogenetic analysis, three specimens, closely resembling S. fuliginoides in overall morphology, represent an additional undescribed taxon Sticta sp. A (Figure 3). However, the material presently at hand is insufficient for properly assessing the morphological characteristics of that species.
Ecology and distribution: In other parts of the world (Europe, Macaronesia, North America, Colombia) S. fuliginoides grows on mossy trees and rocks in humid forests and parks [20]. In our region it is an abundant epiphyte on tree trunks, canopy branches, and climbers, especially in upper montane forests on Mt. Kilimanjaro, but occurring in middle montane to subalpine habitats as well (2470-3520 masl).

3.2.10.
Sticta fuliginosa (Hoffm.) Ach. (Figure 10d,e) Sticta fuliginosa has a cyanobacterial main photobiont (Nostoc) and laminal isidia. A detailed description of the species and a discussion of differences between S. fuliginosa, S. ciliata, and S. fuliginoides are provided in [20]. In our region, S. fuliginosa is characterized by rounded palmate-obovate lobes, usually up to 5 cm in diam., with an uneven, most often greyish-brown upper surface and darker laminal isidia. The lower surface is pale with cupuliform to slightly urceolate cyphellae, and with a pale primary tomentum, but usually without a moniliform secondary tomentum. Chemistry: K−, C−, Pd−.
Of the other species with laminal isidia in our region, S. fuliginosa mostly resembles S. aspratilis which, however, has a well-developed arachnoid secondary tomentum on the lower surface, often making also the primary tomentum appear "furry". Small thalli of S. fuliginosa often have dark brown, rounded lobes with ciliate and occasionally revolute margins very similar to those of S. ciliata agg. Sticta ciliata is usually much smaller and according to Magain and Sérusiaux [20], fresh specimens of S. ciliata and S. fuliginoides both have abundant papillae on the cells of cyphellar membrane, which do not occur in S. fuliginosa.
Ecology and distribution: Sticta fuliginosa is believed to be widely distributed in both hemispheres [20,60]. In our region, it is common in the Taita Hills forests and occurs on Mt. Kasigau. On Mt. Kilimanjaro it is common especially on canopy branches in middle montane forests but is also found in the lower montane to upper montane zones, including the Chagga home gardens (1840-2880 masl).

Sticta marginalis Bory (Figure 10f-h)
Sticta marginalis has a cyanobacterial main photobiont (Nostoc) and marginal isidia that often develop into stalked lobules. Thallus lobes are clearly stipitate, palmate, and ascending from a single attachment point. The upper surface is smooth, usually light grey with a yellow tinge. Isidia are dark, mainly marginal, cylindrical to coralloid, and often develop into characteristic stalked lobules especially in ageing thalli. Lower surface is light to dark brown, often with some yellow coloring, usually without tomentum or with a limited amount of short velvety hair; cyphellae are small and flat. Apothecia are not present in our material, but in the description of S. marginalis from Réunion, the apothecia are described submarginal and the ascospores brown, 1-3-septate, 40-48 × 8 µm [61]. Chemistry: K−, C−, Pd−. Sticta marginalis is very characteristic looking and easily distinguished from the other Sticta species in the region based on the stipitate, palmate, ascending lobes with isidiate-lobulate margins, mostly naked lower surface, and flat cyphellae.
Ecology and distribution: In other parts of the world, Sticta marginalis is known from its type location Réunion and from Madagascar [61][62][63]. In our region, S. marginalis often grows as an epiphyte on tree trunks, but occasionally also on decaying wood and rock. It is common in moist lower and middle montane forests of Mt. Kilimanjaro, the Taita Hills, and Mt. Kasigau (1450-2470 masl).
3.2.13. Sticta sublimbata (J. Steiner) Swinscow and Krog (Figure 13a,b) Sticta sublimbata has a cyanobacterial main photobiont (Nostoc) and marginal soralia. A detailed description of East African material is provided in [12]. The rosetteform thallus has adnate or loosely adnate, elongate more or less linear and narrow (usually < 1 cm wide) lobes with rounded apices that are often also revolute when dry. The upper surface is usually light leather brown to grey but may also be dark brown. The lower surface is light to dark brown, and usually has scarce, short tomentum, but also densely tomentose forms are quite common. Cyphellae are white with open, raised margins. Marginal linear soralia are almost always present and produce farinose to granular soredia, and sometimes also form aggregates resembling isidia. Apothecia not seen. Chemistry: K−, C−, Pd−.
In our region, S. sublimbata is the only sorediate species in lower montane forests and woodland below 2500 masl. Sticta umbilicariiformis, which is common in the upper montane and subalpine zones, can occasionally appear sorediate, but usually has much thicker and wider (several centimeters wide) lobes and an abundantly tomentose lower surface.
Ecology and distribution: In addition to Africa, S. sublimbata is known from Australia, New Zealand, and southern South America [59]. In our region, S. sublimbata is an abundant and common epiphyte especially on tree trunks, but it also grows among bryophytes on cliffs and other rock surfaces. Sticta sublimbata is especially common in the lower montane forests of the Taita Hills, but also occurs on Mt. Kasigau and Mt. Kilimanjaro, mainly below 2000 masl. It may even benefit from human activity as it seems most abundant in moderately disturbed habitats. Ecology and distribution: Sticta tomentosa is a pantropical species found especially in undisturbed, middle to high elevation rainforest habitats [60]. In our region, S. tomentosa 3.2.14. Sticta tomentosa (Sw.) Ach. (Figure 13c,d) Sticta tomentosa has a cyanobacterial main photobiont (Nostoc) and palmate lobes without symbiotic propagules, but usually with apothecia. A detailed description of S. tomentosa is provided in [66] and, based on East African material, in [12]. Our material of S. tomentosa have light grey, palmate lobes ascending clearly from one attachment point, and with tufts of hairs projecting from the lobe margins. The lower surface is white with abundant white tomentum and has prominent, dome-like cyphellae. Sticta tomentosa does not produce isidia, soredia nor phyllidia, but is almost always fertile. The apothecia are mainly submarginal with long white hairs on the margins. Ascospores are fusiform, colorless, 3-septate, 39-50 × 7-11 µm (30-50 × 6-10 µm in [12]). Chemistry: K−, C−, Pd−.
Sticta tomentosa is the only species in the studied lower montane forests that is commonly fertile and does not produce any type of symbiotic propagules. Easily distinguished from other fertile species in the region based on the thick white hairs on apothecial margin. The apothecial margins of other species are pubescent at most, and this feature is usually only seen in specimens collected from high-elevation habitats. Furthermore, the three-septate ascospores of S. tomentosa are larger than those of any other species in the region. The ascospores in the type specimen of S. tomentosa were measured to be 27.5-33.5(−36) × 5.5-8.5 µm [66], which is considerably less than in our material. Previously, also Swinscow and Krog [12] reported a relatively large ascospore size (30-40(50) × 6-10 um) from East Africa.
Ecology and distribution: Sticta tomentosa is a pantropical species found especially in undisturbed, middle to high elevation rainforest habitats [60]. In our region, S. tomentosa is not very common and grows as an epiphyte on tree trunks. It can occasionally be locally abundant in lower montane forests, and also occurs in middle and upper montane forests (1650-3060 masl) in the Taita Hills and on Mt. Kilimanjaro.

Sticta umbilicariiformis
Hochst. ex Flot. (Figure 13e-g) Sticta umbilicariiformis has a cyanobacterial main photobiont (Nostoc) and typically many marginal pustules which can sometimes make it appear sorediate. Thalli of S. umbilicariiformis are often quite large with thick (usually 200-350 µm), wavy to foveolate, loosely adnate to ascending lobes 3-5 cm long and 2-4 cm wide. The upper surface is greyish brown with congested marginal, and often also laminal pustules that may occasionally appear sorediate. The lower surface is cream colored or, more rarely, brown, and thickly tomentose. Primary tomentum has brown and agglutinated stems and squarrose, white tips. Secondary tomentum is white and arachnoid, composed of moniliform assemblages. Cyphellae are slightly urceolate with a relatively wide opening (up to 1 mm in diam.) and raised margins, the pore is often surrounded by a darker ring.
Also fertile specimens of S. umbilicariiformis are common and usually lack symbiotic propagules. The thallus lobes of palmate fertile specimens are often thinner than the lobes of pustulate specimens and vary from wavy to strongly foveolate. Apothecia are submarginal and laminal, up to 2(3) mm wide, with brown disks and, occasionally, pubescent margins patterned with brown nodules. Ascospores are colorless, fusiform, 1-septate, 31-40 × 6.5-8 µm. Chemistry: K−, C−, Pd−. Pustular thalli of S. umbilicariiformis are easily distinguished from other species in the region merely based on their habit. The only vaguely similar species is S. sublimbata which, however, produces true marginal soralia, has adnate and narrow lobes, and mainly occurs below 2000 masl. The characters that help to distinguish fertile specimens of S. umbilicariiformis from fertile specimens of S. aspratilis and S. munda are described under those species.
Ecology and distribution: Sticta umbilicariiformis is presently confirmed only from East Africa, but might have a much wider distribution reaching North America and Australia [20]. In our region, S. umbilicariiformis is common and abundant in the upper montane and subalpine zones on Mt. Kilimanjaro, and also occurs in middle montane zone (between 2540-3800 masl). It is by far the most abundant Sticta species in the subalpine zone, and was also collected from the Erica zone on Mt. Elgon. In the upper montane forest, S. umbilicariiformis mainly grows epiphytically on tree trunks and branches, in the subalpine zone also on rock and soil among bryophytes.
Notes: The phylogeny within the S. umbilicariiformis clade remains poorly resolved even in the more detailed analysis (Figure 2). Almost all pustular specimens represent the same ITS variant (umbilicariiformis1), closely related to a sequence from Rwanda (KT281697). The other ITS variants (umbilicariiformis2-5) are mainly from specimens without pustules, but which often have apothecia. The type specimen of S. umbilicariiformis (H-Nyl 33835; originally described in [67], lectotype designated in [20]) has both pustules and apothecia on the same thallus and the only fertile specimen of S. umbilicariiformis in our material that also has pustules belongs to ITS variant group umbilicariiformis4.

Discussion
A total of 19 Sticta species, including five species new to science, were found from the studied mountains in Kenya and Tanzania, and at least five other new species remain

Discussion
A total of 19 Sticta species, including five species new to science, were found from the studied mountains in Kenya and Tanzania, and at least five other new species remain to be described pending more material. Of these species, only S. fuliginosa, S. sublimbata, S. tomentosa, and S. umbilicariiformis were known to be present in Kenya and/or Tanzania based on previous reports [12,20,[28][29][30][31]. Sticta ciliata and S. duplolimbata had been previously reported from Rwanda [20] and are now confirmed to also occur in Kenya and Tanzania. Additionally, S. marginalis and S. fuliginoides are here reported as new for Kenya and Tanzania, and S. andina as new for Kenya.
Five species were described as new to science: Sticta afromontana, S. aspratilis, S. cellulosa, S. cyanocaperata, and S. munda, the three last mentioned of which have so far only been collected from Mt. Kilimanjaro. Additionally, five putative species, Sticta sp. A in the Sticta fuliginoides aggregate, Sticta sp. B in the Sticta ciliata aggregate, Sticta sp. C in the Sticta weigelii aggregate, Sticta sp. D, and Sticta sp. 2 were well resolved in the phylogenetic tree, but are not yet described due to insufficient material. In contrast to previous reports, it seems unlikely that S. ambavillaria, S. cyphellulata, S. limbata, S. kunthii, S. orbicularis, S. papyracea/variabilis, S. weigelii, or S. xanthotropa would occur in East Africa, as specimens with similar thallus morphologies are here shown to represent other species. Our study confirms the presence of 14 Sticta species in Kenya and 17 in Tanzania. Additionally, S. dichotoma and Sticta sp. 2 are expected to occur in Tanzania based on previous observations [12,28,30], raising the current total number of Sticta species in Tanzania to 19. A short synopsis of all Sticta species reported from East Africa is provided in Table 1.
Several previous studies have demonstrated that many of the "traditional" Sticta species, such as S. fuliginosa and S. weigelii, include taxa that belong to several different evolutionary lineages [19][20][21]68]. The previously reported S. fuliginosa is accompanied by several other taxa with laminal isidia also in East Africa: Sticta ciliata, S. fuliginoides, S. aspratilis, Sticta sp. B, and Sticta sp. A. Of these, S. fuliginoides and Sticta sp. A belong to the same large clade (Figure 3), are morphologically quite similar, and occur in similar habitats. The same applies to S. ciliata and Sticta sp. B. This suggests that there may still be significant undetected diversity hiding under the name S. fuliginosa, both in East Africa and globally.
Several Sticta species belonging to the S. weigelii morphodeme, i.e., those with elongate lobes and marginal isidia [21], were found from our region: Sticta andina, S. afromontana, S. cyanocaperata, and Sticta sp. C. Most of these have flattened isidia, but the isidia of Sticta sp. C are cylindrical, resembling those of S. weigelii s. str. [58,69]. However, Sticta sp. C does not have a color reaction with K, in contrast to the K+ yellow of S. weigelii s. str. [69], giving further support to our phylogenetic analysis, which indicated that S. weigelii s. str. has not been collected from East Africa. This supports the notion that S. weigelii s. str. may be restricted to the Neotropics [21,58]. In East Africa, Sticta specimens with flattened marginal isidia have previously been assigned to S. xanthotropa [12], a species that also mainly occurs in the Americas [32]. However, our results indicate that none of the East African species with flattened isidia actually represent S. xanthotropa: Sticta andina has a strong K+ yellow color reaction, while S. xanthotropa is K− [32]; Sticta afromontana has a robust thallus, while S. xanthotropa is described as "papery thin", and the spores of S. afromontana are larger than those of S. xanthotropa [32]; Sticta cyanocaperata has a very dark lower surface, while it is pale in S. xanthotropa [32]. Furthermore, all the aforementioned species are mainly epiphytic, while S. xanthotropa has been reported to mainly grow on rocks and soil [32,70].
The group of species that have previously been reported from East Africa, but the presence of which we were not able to confirm include S. cyphellulata, S. orbicularis, S. limbata, S. ambavillaria and S. kunthii [12,[26][27][28]30]. Our specimens morphologically matching the previous reports of S. orbicularis and S. cyphellulata were assigned to S. marginalis and S. duplolimbata, while the previously reported S. limbata represents S. umbilicariiformis, as already suggested by Magain and Sérusiaux [20]. Sticta ambavillaria and S. kunthii are both fertile species devoid of symbiotic propagules, and the previous reports from East Africa likely refer to S. munda and/or fertile specimens of S. aspratilis or S. umbilicariiformis. Based on our phylogenetic analyses, a specimen of S. ambavillaria (JQ735978) from Réunion from where the species was described [63], does not group with any of the East African specimens. Furthermore, already Swinscow and Krog [12] reported that the ascospores of East African specimens were shorter than what has been described from the type of S. ambavillaria [33]. Sticta kunthii was described from Peru and appears to have a mainly neotropical distribution [32,33]. It has been reported only once from East Africa, from an upper montane forest on Mt. Kenya. The specimen(s) were described to have "a thallus surface with numerous depressions, sometimes appearing almost pitted, a pale lower tomentum with medium-sized cyphellae, and apothecia with short marginal hairs" [26], which corresponds well with some fertile specimens of S. aspratilis and S. umbilicariiformis. However, the apothecia of these species are submarginal or laminal while those of S. kunthii are mainly marginal [32,33]. Furthermore, the apothecial margins of S. kunthii are distinctly hairy with long bundles of silky, white hairs [33], while those of East African specimens have only velvety stubble. No sequences have as yet been published from S. kunthii, but Moncada et al. [19] placed the species within the S. kunthii clade based on morphological evidence; in our material the only taxon belonging to that clade is the isidiate Sticta sp. D.
Sticta dichotoma and S. papyracea/variabilis are the only two species with green algae as the main photobiont previously reported to occur in East Africa, both from Tanzania where they are said to be rare [12,28,30]. While we did not find any specimens matching the description of S. dichotoma, the species may well be present in montane forests of Tanzania [12,28,30]. Our four Sticta specimens with a green algal photobiont all have marginal phyllidia, and thus correspond morphologically with S. papyracea [12]. Sticta papyracea and the synonymous S. variabilis were both originally described from Réunion [33,71]. However, in the phylogenetic analysis our specimens did not group together with S. variabilis from Réunion ( Figure 5), but instead formed a clade with specimens of "Sticta sp. 2" by Simon et al. [25] collected from Madagascar. This putative species was described to have a green algal photobiont, elongated and dichotomously branching lobes, and apothecia, but lack lobules and phyllidia [25]. Hence, it seems quite possible, that our specimens represent yet another undescribed species. However, more collections are needed before definite conclusions can be made.
In the regions examined, the diversity of Sticta species was highest in indigenous moist forests of the middle montane zone. Two other Peltigeralean lichen genera, Leptogium and Peltigera, exhibited slightly different diversity patterns, with the highest diversity of Leptogium species recorded from moist lower montane forests and that of Peltigera species from the upper montane zone [13,17]. In comparison to the approximately 20 species of Sticta present in the study region, the genus Leptogium is much more diverse with possibly over 70 species in the region [13], while only 8 species of Peltigera have so far been collected from Mt. Kilimanjaro [17]. When comparing the natural and disturbed habitat types on Mt. Kilimanjaro, the number of Sticta species was usually at least slightly lower in disturbed habitats. Similar patterns has previously been reported also for Leptogium and Peltigera [13,17]. Even while the effects and degree of disturbance varied considerably between different habitat types, all the disturbed habitats tended to be at least slightly more open, and often considerably so, than the unaltered habitat types [34], with probable effects to illumination conditions, temperature, and humidity. A similar trend of decreasing lichen species diversity with increasing habitat disturbance has been observed also in previous studies [72][73][74]. Especially shade-adapted cyanolichens are easily negatively affected by disturbance, and these effects on total species diversity are not necessarily compensated by a concurrent increase in the number of heliophytic species [72]. Sticta aspratilis sp. nov. K*, T* Lower montane to subalpine zones.
Sticta cellulosa sp. nov. T* Rare in upper montane and subalpine zones.
Sticta ciliata K*, T* Rare in lower montane forest zone.
Sticta cyphellulata -Not found in this study.
Sticta fuliginosa K, T, R Common in lower and middle montane forests.
Sticta munda sp. nov. T* Rare in middle and upper montane forests.
Previously reported as S. weigelii var. xanthotropa. The reports may represent other species with marginal flattened isidia. [12] Sticta sp. A T* Rare in middle and upper montane forests. Sticta fuliginoides agg.
Sticta sp. B K*, T*, R Rare in lower and middle montane forests.
Sticta sp. C K* Low elevation and lower montane habitats.
Sticta sp. D T* Rare in middle and upper montane forests.
Presence in Tanzania based on previous reports of S. papyracea [12,30].
* New record for the region.

Conclusions
At least 20 species of Sticta have now been confirmed to occur in East Africa, which is almost double to that known before. Only four of the presently accepted species are identified under the same species names that have been used in previous studies from the region, highlighting the general need of taxonomic revisions of lichenized fungi in Africa. The overall diversity of Sticta in East Africa is substantially higher than previously known, but seems to be lower than what has recently been recorded from some mountain regions in the Neotropics. Interestingly, even though our collections originated in relatively few mountain regions of Kenya and Tanzania, we still managed to collect specimens corresponding to almost all morphological species previously reported from East Africa. Both the relatively high number of novel taxa detected, and the percentage of species represented by only a few specimens and/or found from single localities, indicates that more comprehensive sampling will undoubtedly reveal further diversity in the genus Sticta in East Africa.