The Ladybird Beetles (Coleoptera: Coccinellidae) of La Palma

Simple Summary The ladybird beetle fauna of the Canary Islands is quite specific due to the presence of a number of species that do not occur anywhere else (the so-called endemic species). However, many ladybirds recorded in the archipelago are relatively recent arrivals from various parts of the world, as shown by our previous surveys carried out in several of the Canary Islands, including Fuerteventura, Lanzarote, Gran Canaria, and El Hierro. In this paper, we analyze the ladybird fauna of La Palma, one of the western islands of the archipelago, based on our field survey and already published data. The survey resulted in the recording of 26 species, seven of which had not previously been recorded on La Palma, and two of these seven had not been recorded on any of the Canary Islands. Combining our data and literature reports gives a figure of at least 35 ladybird species recorded to date on La Palma. This is fewer than on the central islands of the Canary archipelago (Gran Canaria and Tenerife), but more than on the other four islands (Fuerteventura, Lanzarote, La Gomera, and El Hierro). This study confirms previous observations that the Canary Islands are often colonized by exotic ladybird species. Abstract This paper provides new data on the ladybird beetles (Coccinellidae) of La Palma, one of the western islands of the Canarian archipelago. The field survey of 54 study sites resulted in recording 2494 ladybird individuals belonging to 26 species. Seven of the species recorded were new to La Palma, including two, Harmonia quadripunctata (Pontoppidan) and Nephus reunioni (Fürsch), which were not registered so far on any of the Canary Islands. Novius conicollis (Korschefsky) is synonymized with N. cruentatus (Mulsant). Taking our survey and literature reports into account, a total of at least 35 species of Coccinellidae have so far been recorded on La Palma. This richness in species is lower compared to that of the central islands of the Canarian archipelago, Gran Canaria (42 species) and Tenerife (41 species), but higher than that of the remaining four islands (between 22 and 27 species). The detection of two alien species new to La Palma, Nephaspis bicolor Gordon and Nephus reunioni (Fürsch), confirms earlier observations that colonization of the Canary Islands by ladybird species of exotic origins seems to be a frequent phenomenon.


Introduction
There are over 6000 species of Coccinellidae globally of which about 55 species were reported to occur on the Canary Islands [1][2][3][4]. A significant proportion of them are Canarian or Macaronesian endemics, but many species currently occurring on the Canaries are nonindigenous to this archipelago [3,5]. Some, such as Olla v-nigrum (Mulsant), Nephaspis bicolor Gordon, Pharoscymnus flexibilis (Mulsant), and Cheilomenes propinqua (Mulsant), have become established there only in recent years [2][3][4]6], indicating a high rate of colonization and a need to monitor the changes in the Canarian ladybird fauna.

Materials and Methods
The Canary Islands lie in the northeast Atlantic Ocean near the African coast and are part of the Mediterranean Basin biodiversity hotspot [17]. La Palma is the northwesternmost island, and the most distant from the African mainland. This volcanic island has a relatively small area (706 km 2 ) and reaches a maximum elevation of 2426 m.a.s.l. at Roque de los Muchachos. The mild subtropical Atlantic climate of the island is strongly influenced by humid trade winds that transport moisture from the northeast. As a result, the northern to eastern areas experience relatively stable humid conditions, while the western to southern regions are characterized by low and infrequent precipitation [18]. The vegetation of La Palma includes a wide range of habitats, such as laurisilva and Pinus canariensis forests, coastal habitats, and various kinds of scrub vegetation. In farmland areas, plants of agricultural interest are abundant, and in anthropogenic habitats, decorative plants sustained with irrigation are cultivated ( Figure 1).
Ladybirds were recorded at 54 sites on La Palma (Table 1) using standard collecting methods, such as a beating tray, a sweeping net, or through direct observation. Although some of the caught ladybird individuals were released after their identification, each individual was noted. The majority of specimens were recorded by J. Romanowski and P. Ceryngier between 16 and 21 June 2021. Some material collected earlier, in 2013, 2014, 2018, and 2019, by A. Machado, T. Staněk, and J. Krátký was also used in this study. The voucher specimens are stored in the insect collection in the Institute of Biological Sciences, Cardinal Stefan Wyszyński University in Warsaw, and in the private collections of Jaroslav Větrovec. Species identification was based on morphological and anatomical features, including the form of reproductive organs (see [4,5,14,16]), and individuals collected in the larval and pupae stages were reared into adults in the laboratory. Habitus images were taken using a Leica MZ 16 stereo microscope with an IC 3D digital camera attached. The photographs of the genitalia were taken using an Olympus DP23 digital camera attached to an Olympus BX43F compound microscope. Final images were produced using Helicon Focus 5.0 × 64 and Adobe Photoshop CS6 software. The systematic arrangement of Coccinellidae used in this study follows Che et al. [19]. enced by humid trade winds that transport moisture from the northeast. As a result, the northern to eastern areas experience relatively stable humid conditions, while the western to southern regions are characterized by low and infrequent precipitation [18]. The vegetation of La Palma includes a wide range of habitats, such as laurisilva and Pinus canariensis forests, coastal habitats, and various kinds of scrub vegetation. In farmland areas, plants of agricultural interest are abundant, and in anthropogenic habitats, decorative plants sustained with irrigation are cultivated ( Figure 1).

Results
Altogether, 2494 ladybird individuals (2390 adults, 88 larvae, and 16 pupae) belonging to 26 species (including one species identified to the genus level) were recorded in this study. Detailed data on all the recorded species are provided below. Morphological and anatomical details of several species of special interest are photographed.
Distribution: This species has been widely used as a biocontrol agent in various parts of the world. It is thought to occur natively in Colombia, Mexico, southern California (USA), and on the island of Trinidad [20]. In the Canary Islands, it was previously recorded on La Palma, La Gomera, Tenerife, Gran Canaria, Fuerteventura, and Lanzarote [4]. Distribution: This is an endemic Macaronesian species, reported to be on all main islands of the Canary Islands [1,15] as well as Madeira [11]. Distribution: This species is widespread in the Holarctic, and was also introduced to Australia, New Zealand, Africa, and South America [21][22][23]. In the Canary Islands, it has been found on La Palma, La Gomera, and Tenerife [1].

Stethorus wollastoni
Remarks: Specimens of A. bipunctata collected in this study represent several color forms, including f. typica, sexpustulata, quadrimaculata, and fasciatopunctata. The lattermost is mainly known from the Middle East and central Asia [24,25]. Its presence on La Palma may, therefore, indicate the source of the Canarian population of A. bipunctata. Distribution: This is a Palaearctic species [23], not previously recorded on the Canary Islands.
Distribution: This species is widely distributed in the Palaearctic [23] and in many regions outside of its native range, such as South and North America, Africa, India, Australia, New Zealand, and even the remote Easter Island in the Pacific [26][27][28][29][30]. It is common on all islands of the Canary archipelago [1]. Distribution: This is a Palaearctic species [23], recorded in the Canary archipelago on La Gomera [1], and recently also on Gran Canaria [4] and El Hierro [16]. Distribution: This is a species mainly found in central and southern Europe [23]. It is reported on the Canary Islands either as N. cruentatus or N. conicollis, on El Hierro [1,32], La Palma [1,33,34], Tenerife [1,35], and Gran Canaria [1,4]. Distribution: This is an endemic Canarian species, reported to be on Gran Canaria [33], Tenerife [35], and El Hierro [16]. It is new to La Palma.  Korschefsky, 1935 Material examined: From Las Caletas II: 17.III.2018, one ex. was collected (adult female); from Puerto de Puntagorda: 18.III.2018, one ex. was collected.

Novius canariensis
Distribution: This is an endemic Canarian species, reported to be on Gran Canaria [33], Tenerife [35], and El Hierro [16]. It is new to La Palma.  Remarks: N. cruentatus is a specialized predator of Palaeococcus fuscipennis (Burmeister), a giant scale (Hemiptera: Monophlebidae) associated with several pine species [36][37][38]. In the Canary Islands, N. cruentatus is usually found on Pinus canariensis ( [4,34], this study). Korschefsky [33] considered the specimens collected on La Palma as representing a separate species, different from N. cruentatus and placed them in a newly described species, N. conicollis. However, examination of male genitalia in specimens collected in this study revealed no difference between them and the European specimens of N. cruentatus, and therefore we here synonymize Novius conicollis Korschefsky, 1935  islands of the archipelago, El Hierro, La Palma, and Tenerife, and in 2015 it was found to be well established on Tenerife [2]. Our present record indicates that this species has also been established on La Palma.   Distribution: Until recently, this species was considered to be endemic to the Canary Islands, but new data showed its presence in continental Spain, Algeria, and Cape Verde [40]. It is found on all islands of the Canary archipelago [1,[14][15][16]. Distribution. This species is endemic to the Mascarene Island of Réunion [41]. In Macaronesia, it was previously reported in the Azores and Madeira [11], but not on the Canary Islands. Distribution: This species is widely distributed in the Mediterranean Basin and the Middle East [23]. It is previously recorded on all islands of the Canary archipelago except La Palma [1,14,15].
Remarks: We are unable to determine the species affiliation of this single female. The genus is represented in the Canary archipelago by one species: Diomus gillerforsi Fürsch, recorded on La Palma and Tenerife [1,42]. Distribution: This species is a well-known biocontrol agent of Australian origin, established in many warmer regions worldwide [43]. It has been recorded on all seven islands of the Canary archipelago [1,14,15].
Material examined: From Santa Cruz: 21.VI.2021, one ex. was collected (female) from a palm tree.
Remarks: We are unable to determine the species affiliation of this single female. The genus is represented in the Canary archipelago by one species: Diomus gillerforsi Fürsch, recorded on La Palma and Tenerife [1,42].  Distribution: This species is widely distributed in Europe and North Africa and is also reported to occur in the Asiatic part of Turkey [23]. It is found on all the Canary Islands [1]. Distribution: This is an Australian species, introduced in many regions of the world as a biocontrol agent [48]. It is found on all islands of the Canary archipelago [1,49].

Discussion
Prior to this study, 28 ladybird species were reported to occur on La Palma (Table 2). We failed to find 10 of them but found seven species not previously reported as occurring on this island, including two (Harmonia quadripunctata and Nephus reunioni) that are new to the whole Canary archipelago. Another species recorded by us, Nephaspis bicolor, was released several years ago on La Palma [2] but had not been found as established there prior to this study. We also collected a single female of the Diomus sp. whose species affiliation could not be determined, but whose spermatheca is different from that of the Mediterranean and Middle Eastern D. rubidus (Motschulsky). Perhaps this female belongs to D. gillerforsi Fürsch, a species described on the basis of one male collected on Tenerife [42]. To solve this problem, more material representing both sexes is needed.  Altogether, the literature reports and our data indicate the occurrence of 35-36 species of Coccinellidae on La Palma. This is fewer than those reported so far on Gran Canaria (42 species) and Tenerife (41 species) [4], but clearly more than on Fuerteventura (27 species), La Gomera (24 species) [1,49], Lanzarote (23 species) [15], and El Hierro (22 species) [16].
Of the species recorded in this study as new to La Palma, one, N. canariensis, is considered to be endemic to the Canary Islands [4]; four, H. quadripunctata, M. octodecimguttata, S. nubilus, and P. nigripennis, occur both on the Canary Islands and the neighboring regions of North Africa and Europe [23]; and two, N. bicolor and N. reunioni, are alien species, native to the remote islands of Trinidad (Lesser Antilles in the Atlantic Ocean) and Réunion (Mascarenes in the Indian Ocean), respectively [39,41].
The La Palma population of N. bicolor is almost certainly derived from individuals introduced to the Canary Islands for biocontrol of whiteflies (Hemiptera: Aleyrodidae). As reported by Rizza Hernández and Hernández Suárez [2], between 2005 and 2010, N. bicolor imported from Trinidad was released at several sites on the islands of La Palma, El Hierro, and Tenerife, and in 2015, abundant, established populations were recorded on Tenerife. On La Palma, a total of only 36 individuals were released in Puerto Naos on the western coast of the island in 2008 and 2009. After about 12 years, we found this ladybird in Santa Cruz, on the opposite (eastern) coast. The distance between these two localities is not great in a straight line (less than 20 km) but, as the island is baffled meridionally by a steep mountain chain, the direct spread of the beetle from west to east may have been impeded. We, therefore, suppose that N. bicolor has dispersed along the coastal areas of La Palma or arrived there from Tenerife.
Nephus reunioni was introduced in the 1970s and 1980s to some Mediterranean countries and the former USSR as a biocontrol agent against mealybugs (Hemiptera: Pseudococcidae), and subsequently established in Albania, France, Greece, Italy, Portugal, and Spain [61]. Later, its occurrence in the Azores and Madeira was documented [11,62].
In addition to the two species mentioned above, five other alien species have been recorded on La Palma. Four of them, American Delphastus catalinae and Australian Novius cardinalis, Cryptolaemus montrouzieri, and Rhyzobius lophanthae were found in this study, but we did not manage to collect the fifth species, American Olla v-nigrum. Most of these alien ladybirds are specialized predators of whiteflies (N. bicolor, D. catalinae) or scale insects (N. reunioni, N. cardinalis, C. montrouzieri, and R. lophanthae), but O. v-nigrum is a generalist predator, most often preying on aphids and psyllids, with a high potential invasiveness [5]. To date, it has become established on many oceanic islands and archipelagos in the Pacific and Indian Oceans (Easter Island, Hawaii, Midway, Guam, Tahiti, New Caledonia, Japan, and Réunion) [63][64][65], and has recently started to spread in Macaronesia. On the Canary Islands, O. v-nigrum has been observed since 2014, first on Tenerife and La Palma and then on Lanzarote and Gran Canaria [4,15,66]. In 2020, it was also recorded in Madeira [5].
Another generalist predator, the Asiatic Harmonia axyridis (Pallas), can also be expected to make an imminent appearance on La Palma and other islands in the Canary archipelago. Specimens of this well-known, now nearly cosmopolitan invasive species [67] were already recorded on Tenerife in 2003 and 2004 [49,68] and recently in 2022 [69]. H. axyridis could not establish, despite its deliberate introductions in the Azores between 1988 and 1995 [70], and the first findings of a reproducing population of H. axyridis in Macaronesia have been reported from Funchal (Madeira) in 2019 and 2020 [5,11].