The paramo includes all natural and semi-natural ecosystems located above the natural montane tree line in the northern Andes [1
]. Nevertheless, few isolated paramos exist, apart from the main cordilleras and are called extra-Andean paramos. The most adequate examples are located in Ecuador and cover the mountain tops of the Sumaco and Sangay volcanoes in the Amazon basin [4
], as well as the Kutuku and El Condor Cordillera [5
]. To date, only basic research has been conducted on these isolated paramos, even though they constitute a priority candidate for ecological and conservation efforts [7
]. Generally, the largest distribution of the paramo is in the tropical mountains of Central and South America. Nonetheless, it is also present in certain areas within East Africa, Hawaii and Malaysia [9
]. Chronologically, the paramo is constituted by tropical, temperate and cosmopolitan elements [11
]. In addition, the evolutionary history of the paramo demonstrates that the origins of the present flora depend dominantly on elements from the northern continent more than own elements and southern hemisphere [12
The Andean paramo is distributed in the high mountains of Venezuela, Colombia, Ecuador and northern Peru, where its flora contributes an important percentage of the regional biodiversity [13
]. Currently, it is considered that the paramo is a strategic ecosystem in terms of environmental and landscape services, of which the most important are water production and regulation, as well as carbon storage [17
]. In Ecuador, the paramo covers approximately five percent of the national territory and hosts about 1500 vascular plant species [19
], with an endemism rate estimated of about 60% at species level [1
]. It is considered as a fragile ecosystem, where the main threats are mainly fire, grazing, and Andean crops, among other minor causes [20
Several studies have considered the ecosystem and its flora, trying to fit it into a regular classification system [24
]. Its crossed flora and ecotones indicate a variety of local floristic features leading the classification of the vegetation of the paramo to advance significantly, particularly in Ecuador [1
]. The denominations by their physiognomy (shrub, herbaceous), by type of climate (wet, dry) and/or plant associations [35
], resulted in several types of paramo, such as the sub-paramo, where dense and shrubby vegetation dominates [36
]. The mid paramo is considered a transition zone between the tree line and the open paramo, being of moist dense shrubland and glasslands vegetation [1
]. The super paramo is characterized by sparse and discontinuous vegetation, with predominantly lichens, mosses and small herbs and shrubs, often belonging to the Asteraceae family, such as Senecio
There is a severe lack of knowledge about the phytogeography on the extra-Andean paramo. Studies of the paramo of Costa Rica to Peru, where twelve genera have been described, originated from the Savannas [41
]. In the study of the flora of Avila (Eastern Cordillera of Colombia), some 18 genera (15%) have been encountered [42
], which originated from the Savannah [43
]. Other studies of the phytogeography of the flora of the Podocarpus National Park in southern Ecuador indicated that very humid climate and regional isolation are considered as key factors in the current geographic distribution of the 187 genera of the paramo [44
]. There are 40 genera in common with the puna (21%), and three other types of floristic geographical components, such as tropical (55%), temperate (38%) and cosmopolitan (7%).
In Ecuador, isolated paramos outside the eastern to western ranges of the Andes are physiognomically different from the paramos encountered on the ridges of both mountain ranges, which have been developed upon volcanic ash deposits and lava flows. Unfortunately, there are so far no studies in the isolated paramos of the Sumaco and Sangay volcanoes, most probably due to particular adverse weather conditions and accessibility [45
], except for a single exploratory expedition which took place in 1979 [27
]. Nonetheless, a recent study on Sumaco paramos has revealed new species records, and clarified the endemism as well as the plant communities [4
The current study represents pioneering research on the ecology of extra Andean paramos, focusing on the Sumanco volcano. Hereby, we most likely count a lack of anthropogenic intervention, possibly presenting its own floristic evolution and with different types of paramo. There are so far no floristic records of the native taxa of these sites, leading undoubtedly to the first register of the flora and the ecologically identification of existing plant formations in the altitudinal gradient of the Sumaco volcano. Therefore, the main goal of our study has been to fully characterize the given flora (taxonomical diversity), vegetation (life forms) and the chorological aspects of the paramo belt on the Sumaco volcano.
3.1. Plant Diversity
The paramo plant diversity on the Sumaco volcano is represented by 68 species of terrestrial vascular plants, belonging to 54 genera and 31 families. The vegetation covers between 95–100% of the substrate and the height of the main vegetation strata reach 0.5–2 m. The predominant life forms of the Sumaco Volcano plants are erect shrubs, erect herbs, tussocks, just a few cushions, and various types of rosettes characteristic of the paramos. The most diverse families were Asteraceae with eleven species (14.9% of the total determined species), Orchidaceae with seven species (10.4%), followed by Cyperaceae, Dryopteridaceae, Ericaceae, Lycopodiaceae and Poaceae with four species, each representing 6% of the total species. At genus level, the dominant ones were Elaphoglossum, Epidendrum and Huperzia with four species each, followed by Carex with three species, and Agrostis, Blechnum, Elleanthus, Grammitys, Miconia and Stellis with two species, whereas all other genera only presented one species. The SDI values (2.6 ± 0.1) did not show significant differences along the altitudinal gradients (χ2 = 0.87, p = 0.34), and neither did the other environmental variables.
3.2. Species Assemblages and Floristic Groups along Gradient
Following the NMDS analysis, the plots were grouped within two preliminary “communities” or floristic groups (Figure 2
), the first group (G I) including the plots of the lowest altitude classes, while the second group (G II) accounted for the plots located in the highest altitude classes. The stress values that the cluster reached when reducing the dimensionality of the model are acceptable (stress = 0.12). There are further factors other than the altitude, which is the most influential variable that determines the clustering of plots (Table 1
, Figure 3
). The growth habit also determines the affinity of the plots, being the greater presence of herbaceous species in the plots of the first two gradients that influence its grouping, while the greater number of shrub species in the plots located in the higher gradients, is the factor that determines the separation in the groups. Temperature is not relevant in the grouping.
In the community GII (3300–3504 m a.s.l.), 39 species and 31 genera were determined, Orchidaceae being the most diverse family, with nine species, followed by Asteraceae and Ericaceae with four species each, and Dryopteridaceae, Cyperaceae and Poaceae with two species each. This gradient develops at an intermediate altitude of the volcano and it presents a dense vegetation of herbaceous and shrubby type, with a range of plant cover of 100%. The height of the herbaceous layer is of about 0.15–2 m and the shrub layer is around 0.30–2.50 m. This strip is very well delimited. The arboreal stratum decreases its size, increasing the altitude and bushes scattered among the “pajonal” next to small grasses. The species with the highest percentage of coverage belonging to the dominant families throughout the sampled area were: Elleanthus aurantiacus (20%) for Orchidaceae; Elaphoglossum dendricolum (20%) for Dryopteridaceae; Cortaderia nitida (75%) for Poaceae; Pernettya prostrata (15%) and Disterigma codonanthum (15%) for Ericaceae; and Monticalia andicola (5%) for Asteraceae.
In the community GI (3585–3778 m a.s.l.), 42 species and 34 genera were determined. Asteraceae is the most diverse family with seven species, followed by Orchidaceae with five species, and Cyperaceae, and Poaceae with three species each. The species with the highest coverage are Monticalia andicola (25%), Diplostephium rupestre (25%), Pernettya prostrata (25%), Huperzia hystrix (5%) and Blechnum cordatum (5%). This community has been encountered in the upper cone, on a rounded crest, and it has low herbaceous, as well as shrubby vegetation of around 0.15–1 m in height. The “pajonal” is a variable where there are low, dry and humid “pajonales” grasslands. In most of the sites, they are covered by a great variety of mosses.
3.3. Life Forms and Species Turnover
In the communities of the two gradients, the dominant lifeforms of the species were the erect herbs (39 species of the 68 registered, 59%), the bunchgrass (10 species 14.5%) and the prostrate herbs (4 species 5.8%). There are so far no records of cushion plants at the first community. However, at the next community, just one species is present (1.4%). The “rosettes”, in general, are acaulescent, with six species (8.7%), two basal (2.8%) and four stem rosettes (5.8%) (Figure 4
The lifeforms that indicate a significant difference in frequency between gradients are the cushions (Table 2
, Figure 5
), the basal rosettes, and the stem rosettes, which are more frequently in community II at higher altitudes. The rest of the lifeforms lack the presentation of significant differences throughout the two communities.
The turnover species among the gradients is the main reason why the plots are grouped. The gradients are floristically different. Distribution and abundance are characteristics that respond to its spatial distribution pattern, and to other factors that we have not been classified so far. The difference between gradients is evident and the SIMPER analysis indicates the calculated values for each of the gradients. The gradients III–IV are the most dissimilar (84.8%), while the least dissimilar are the gradients I–II (54.1%). The values of dissimilarity between the I–III gradients are also high (77.9%) and the dissimilarity values between the III–IV gradients (67.7%) confirm the floristic separation of the first two gradients in a floristic group and the other two gradients, forming another floristic group. Table 3
lists the five species responsible for the floristic dissimilarity in each gradient, as well as the average values of abundance of each of them in each gradient and a cumulative value of the percentage that represent each one of them.
3.4. Plant Geography
Of the total 54 genera recorded, 44.5% belong to the tropical component, followed by temperate with 33.3%, and cosmopolitan with 22.2%. The neotropical montane element has the highest number of species with 15, followed by Austral-Antarctic with ten species. Similarly, with ten and seven species are wide temperate and cosmopolitan, respectively, and this declined to five and four species for the paramo-puna and paramo, respectively (Figure 6
Correlating the migration on extra-Andean paramo, at the same latitude in the paramos of the cordillera real (Antisana Ecological Reserve, UTM code 17MRV24, VegParamo 2018), there are 13 species and 5 genera in common with the Sumaco Volcano, most of them being erect herbs. Although there is also a considerable amount of tussocks that occur in both paramos, Xenophyllum humile
(Kunth) VA Funk, is the only rosette shared on both sites [85
]. Further, west within the same Reserve Antisana (UTM code 17MRV14, VegParamo 2018), only four species and seven genera are present in both sites. Likewise, in the area of Aloag—Machachi (UTM code 17MQV64), we only found two species and one genus in common with the species recorded in the Sumaco volcano.
On the Sumaco volcano isolated paramo, the vegetation is mountain-characteristic and as elevation increases, the vegetation physiognomy gradually changes from shrubby to grasslands and finally patchy to bare substrate where the most recent eruptions occured. Although the flora of the isolated Amazonian volcanoes has been poorly studied, apparently the influence of altitude exerts the same effect on the paramo of the mountain range, as well as the volcanoes. An altitudinal gradient in the mountain range central discriminates the super-paramo (at higher altitudes), with the lower ranges dominated by Poaceae and possibly with lower paramos (mid paramo), dominated by bushes (Ericaceae) and herbs (ferns and lycopodium). This is something that occurs in the Sumaco volcano, since the rosettes and cushion typical of the super-paramo are present in the highest gradient. The presence of these species determines the structure of the so-called super paramo. Plant diversity can also be influenced by altitude.
The isolated paramos of the Sumaco volcano are in a good state of conservation, with a range of pioneer plant cover of 95% to 100%. There are significant differences in the number of individuals, life forms and diversity, with respect to the altitudinal gradient. Marked differences were found within each strip, which is possibly a product of the presence of microhabitats caused by the interaction of the edaphic—environmental variables of the different altitudes in which they were sampled. The intact conservation of this ecosystem is due to the distance, rough terrain and difficult access to the summit.