Dinas, Wollaston, 1867

Skuhrovec, JiĜí & Batelka, Jan, 2014, Taxonomy of the Cape Verde endemic weevil genus Dinas (Coleoptera: Curculionidae: Entiminae). Part I: Description of a new subgenus, and two new species from São Nicolau Island, Acta Entomologica Musei Nationalis Pragae 54 (1), pp. 315-336 : 330-332

Biogeography of Dinas

Distribution of the genus. In addition to the taxonomic studies of the genus Dinas , only four papers with simple faunistic notes have been published. Few specimens of D. angustula were reported from Santo Antão by ALLUAUD (1936) and GEISTHARDT (1982), two short series of D. elliptipennis Wollaston, 1867 were reported from Fogo by FRANZ (1987) and GEISTHARDT (1982), and ¿ve specimens of D. sitonaeformis were recorded from São Nicolau by GEIST- HARDT (1982). Much controversy was introduced to the distribution of Dinas by incorrect identi¿cations by ALVES (1973). She published new records from Fogo, Maio and Santiago, but those from Santiago she incorrectly associated with D. punctipennis Roudier, 1957 and with D. elliptipennis , as was already pointed out by GEISTHARDT (1995). She also mistakenly proposed possible synonymy of D. micans and D. viridisquamea Roudier, 1957 (although with a question mark) with D. elliptipennis . Those apparent identi¿cation errors were, irrespective of the refusing statement in GEISTHARDT (1995), adopted by ARECHAVALETA et al. (2005). So far we know, all species of Dinas are single-island endemics ( Table 2.) ( Fig. 5A ).

The Northern Chain is characterized by a higher number of single-island endemics per all islands (i.e. 2–4 per island), in comparison with those of the Southern Chain, where only one single-island endemic is known per each island (with the exception of Sal, where Dinas , like Tarentola Gray, 1825 (Vertebrata: Squamata ), is absent because of a lack of suitable habitat ( VASCONCELOS et al. 2010, 2012)). We can only speculate about the mode of dispersal of flightless Dinas between islands or island chains, but we have to consider that, for example, Dracaena trees were much more abundant before the arrival of the ¿rst human settlers and therefore there was a good chance for beetles to attach themselves to some drifting wood. Higher diversity of Dinas in islands of the Northern Chain may also be positively influenced by the short distance between São Nicolau and Desertas (about 17 km) and between São Vicente and Santo Antão (about 15 km). Connection of São Vicente with all three Desertas, which are separated from each other by ocean depths of less than 50 m ( ARNOLD et al. 2008, CUNHA et al. 2008), is to be expected at least during the Pleistocene glacial periods Mindel (- 75 m, 440.000–320.000), Riss (- 100 m, 180.000–120.000) and Würm (- 90 m, 70.000 –10.000).

Distribution of Dinas (s. str.). Both species of the nominate subgenus Dinas are distributed exclusively on the islands of the Northern Chain ( Fig. 5A ). This might be a sampling artifact, but this is unlikely as this corresponds with biogeographic data available for some other native Cape Verde organisms. Three endemic and flightless genera of Opatrini ( Coleoptera : Tenebrionidae ) are also distributed exclusively either within the Northern Chain ( Trichopodus , the unique record, given by ALVES (1973) with a question mark, from Santiago is apparently a misidenti¿cation), or within the Southern Chain ( Melanocoma and Platyprocnemis Español & Lindberg, 1963) ( ARECHAVALETA et al. 2005). Totally different species composition between the Northern and Southern Chain is also characteristic in the speciose radiation of the flightless tenebrionid genus Oxycara Solier, 1835 (occurrence of O. compacta (Motschulsky, 1845) in São Nicolau is a misinterpretation of a record given by GEISTHARDT (1982), who only compared his unidenti¿ed specimen from São Nicolau with O. compacta from Santiago) ( ARECHAVALETA et al. 2005). Even some excellent bird fliers like the kestrel, Falco tinnunculus Linnaeus, 1758 , have in Cape Verde two endemic subspecies distributed accordingly to these two geological units ( HILLE et al. 2003). It is hypothesized that the barrier responsible for such a strong genetic difference between both island chains is the northeastern trade winds, which impede effective gene flow between populations ( HILLE et al. 2003). In some terrestrial vertebrates these trade winds allow only unique ‘one way’ colonization events from the northerly situated islands towards the south ( VASCONCELOS et al. 2010).

Distribution of Dinas in São Nicolau ( Fig. 5B ). Dinas strakai sp. nov. and D. afonsoi sp. nov. were collected from the locality belonging geologically to the Former Eastern Island of São Nicolau, while D. sitonaeformis and D. angusticeps are known only from localities situated on the area of the Former Western Island. This distributional pattern corresponds with the presence of two different species of Tarentola geckos in São Nicolau, where one is restricted to the western part of the island and one only lives easterly of the Morro Bràs formation. Allopatric speciation of these two Tarentola species native to São Nicolau is expected ( VASCONCELOS et al. 2010, 2012). It should in this case, however, be investigated if the presence of two species of Microspina subgen. nov. in the Former Western Island is a result of two independent colonization events or if the species evolved from a common ancestor in São Nicolau. A possibility also exist that one of the three São Nicolau species of Microspina subgen. nov. will be discovered on the opposite part of the island, and may reveal itself as a species evolved and spread in São Nicolau after uni¿cation of both former islands.

Figures

Fig. 5. The map of Cape Verde Islands: A – distribution of Dinas in the Cape Verde Islands: white square – Dinas (s. str.); black circle – northern linage of Dinas (Microspina); and black square – southern lineage of Dinas (Microspina). B – distribution of Dinas in São Nicolau: white square – Dinas (s. str.) strakai sp. nov.; white circle – Dinas (Microspina) afonsoi sp. nov.; black and white circle – Dinas (Microspina) angusticeps Roudier, 1957; and black circle – Dinas (Microspina) sitonaeformis Wollaston, 1867.