“FINCHES” ARE AZOREAN SNAILS António M. De Frias Martins
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AÇOREANA, 2011, Suplemento 7: 209-228 WHEN THE GALÁPAGOS “FINCHES” ARE AZOREAN SNAILS António M. de Frias Martins CIBIO-Açores, Centre for Research in Biodiversity and Genetic Resources, Department of Biology, University of the Azores, 9501-801 Ponta Delgada, São Miguel, Azores, Portugal e-mail: [email protected] ABSTRACT On his way home, towards the end of the historic voyage of H.M.S. Beagle, Charles Darwin stopped by the Azores. He subsequently wrote a detailed report on the people and their life style, but had nothing to say about the archipelago’s fauna and flora, except that everything reminded him of England. Yet, if Darwin was to return now, he would find evidence of evolution, mostly in the terrestrial molluscs. Of the 101 described species of land and fresh- water molluscs in the Azores (halophilic species excluded), 47 are endemic, and there is strong evidence for 28 additional species, not yet described. This wealth of endemism is distributed throughout the nine islands of the archipelago in patterns closely related to the age and the volcanic activity of each one. Examples are given of distributional patterns of endemic taxa, namely of the Oxychilidae and Enidae. Reference is made to the on-going research testing the speciation patterns seen in Drouetia in relation to the theory of punctuated equilibrium, as well as to the variability of Napaeus pruninus and reticulate evolution. RESUMO A caminho de casa, mesmo no fim da histórica viagem do Beagle, Darwin parou nos Açores. Escreveu um relatório pormenorizado sobre as gentes e sua maneira de viver, mas nada teve a dizer sobre a fauna e a flora local, excepto que lhe lembravam a sua velha Inglaterra. No entanto, se Darwin voltasse agora, poderia muito bem encontrar evidência de evolução, sobretudo nos moluscos terrestres. Das 101 espécies de moluscos terrestres e de água-doce descritas (exceptuando-se as espécies halófilas), 47 são endémicas, e há evidência forte para 28 espécies adicionais, ainda não descritas. Esta riqueza de endemismos distribui-se pelas nove ilhas em padrões PPaginação_21.inddaginação_21.indd 209209 119-01-20129-01-2012 111:52:051:52:05 210AÇOREANA 2011, Suplemento 7: 209-228 estreitamente relacionados com a idade e a actividade vulcânica de cada ilha. São dados exemplos de padrões de distribuição de taxa endémicos, nomeadamente dos Oxychilidae e dos Enidae. Faz-se referência à investigação em curso associando os padrões de especiação em Drouetia e a teoria do equilíbrio pontuado, bem como a variabilidade de Napaeus pruninus e a evolução reticulada. OCEANIC ISLANDS AND did not bring any revelation of ENDEMISM: THE EXAMPLE striking endemism; instead, it OF THE AZOREAN reminded him of England: MALACOFAUNA “The rocks are covered in some parts by a thick brushwood about volution has been histori- three feet high, and in others by Ecally linked to islands, not heath, fern, and short pasture: because they are the only places a few broken down old stone where it happens but because walls completed the resemblance they are more or less contained with the mountains of Wales. I environments, suitable for in- saw, moreover, some old English depth studies. They are test friends amongst the insects; and tubes of evolution. Darwin of birds, the starling, water- (1859: 105) thought so when wagtail, chaffi nch, and blackbird.” searching for answers to unravel (Darwin, 1839: 369). the origin of species: The evidence missed by “If we turn to nature to Darwin – the land snails – was test the truth of these remarks, hiding beneath the fallen leafs of and look at any small isolated the remnants of the laurisilva. area, such as an oceanic island, The Azorean malacofauna, although the number of species contrary to that of Madeira, was inhabiting it is small, […] yet unknown at the time Darwin of these species a very large sailed aboard the Beagle. The proportion are endemic, - that is, first Azorean endemic mollusc, have been produced there, and Bulimus [=Napaeus] pruninus, nowhere else in the world.” was described by Augustus A. Yet, when Darwin landed on Gould in 1848. It was only in the Azores twenty three years 1860 that Arthur Morelet pro- previously, the fauna and flora he duced the first extensive work had an opportunity to examine on the Azorean land snails. Of PPaginação_21.inddaginação_21.indd 210210 119-01-20129-01-2012 111:52:061:52:06 MARTINS: WHEN THE “FINCHES” ARE SNAILS 211 the 69 species recorded, 32 were supratidal prosobranchs exclud- considered endemic. Backhuys ed), the count will be about 129 (1975) compiled the second ma- species of which 75 are endemic, jor list of the Azorean terres- thus raising the percentage en- trial malacofauna and, though demism to ~58%. If introduced raising the count to 99 species, species are excluded (those of which 39 were endemic, he thought to have arrived after the clearly stated: 15th century, the beginning of the “The present paper does not islands’ human colonization), mark the end of the road, but then the percentage of endemics rather it marks the starting would rise to ~79%, thus provid- point for further research. Many ing a more realistic scenario for problems remain to be solved the pattern of land snail evolu- and many new and interesting tion expressed in the islands. facts will be discovered in the A closer look at Figure 1 re- future” (p. 5). veals various biogeographic pat- The last count based on pub- terns and one peculiar situation. lished records and preliminary The terrestrial mollusc species lists fixed the total number at 114 of the Central Group of islands species, of which 49 are endem- (Terceira, Graciosa, São Jorge, ic. If the halophilic Ellobiidae Pico and Faial) clump very obvi- and supra-tidal Assimineidae ously in that they share most of and Truncatellidae are exclud- their endemics, thus refl ecting ed, there are 101 species, 47 of their geographical closeness. A which are endemic (Cunha et al., similar situation may be inferred 2010). Current research, how- for the Western Group (Flores ever, points to an even greater and Corvo). The oddity appears number of endemics awaiting in the Eastern Group, where description and when they are Santa Maria has the least number would lead to a consequent re- of shared endemics but exhibits arrangement of taxonomic and the greatest percentage of island biogeographical affinities (Table endemics. Being by far the oldest 1 and Figure 1; see also Martins, island (8 Ma), Santa Maria was 2005). When the land and fresh- expected to have a high percent- water malacofauna of the Azores age of island endemics. Similarly, is updated with these descrip- it was expected to constitute the tions (halophilic ellobiids and colonization source for the re- PPaginação_21.inddaginação_21.indd 211211 119-01-20129-01-2012 111:52:061:52:06 212AÇOREANA 2011, Suplemento 7: 209-228 maining islands. However, the Maria as the main focus for the evidence presented in Figure 1, colonization of the remaining corroborated by the morpho- islands of the archipelago, thus logical and anatomical affi nities requiring additional explanation of Drouetia (Figure 6), leads to a for the subsequent colonization re-assessment of the role of Santa of the other ones. TABLE 1. Distribution of the land and freshwater molluscs of the Azores, including species under description (halophilic ellobiids and supratidal prosobranchs not included). E, endemic (Azores); e, undescribed; I, introduced; M, endemic (Macaronesian); N, native. Cor, Corvo; Fai, Faial; Flo, Flores; Gra, Graciosa; Pic, Pico; Sjo, São Jorge; Sma, Santa Maria; Smg, São Miguel; Ter, Terceira. Species E/e N I Cor Flo Fai Pic Sjo Gra Ter Smg Sma Pisidium casertanum x xxx xxx Hydrocena gu a M xxxxxxxxx Craspedopoma hespericum E E E EEE Galba truncatula xxx Lymnaea peregra xx Physella acuta x xxx Helisoma trivolvis xx Ferrissia fragilis xxxx Deroceras caruanae xxxxxxx xx Deroceras laeve x xxx xx Deroceras reticulatum xxxxxxxxxx Arion distinctus x xxx x Arion intermedius x xxxxx xxx Arion cf. fl agellus x xxxxxxxx Balea heydeni x xxxxxxxxx Balea nitida EEE Cochlicopa lubrica x xxxxxxxxx Cachlicopa lubricella x xxxxxxxx Discus rotundatus x xxxxxxxxx Helicodiscus parallelus xx Helicodiscus syngleyanus xx x Toltecia pusilla x xxxxx xx Napaeus alabastrinus EEE Napaeus atlanticus [=forbesianus] E EEEEE Napaeus delibutus E EEEEEE Napaeus hartungi E E Napaeus pruninus E E Napaeus tremulans E E Napaeus vulgaris E E Napaeus sp. a eee Napaeus sp. b eeee Napaeus sp. c e e Euconulus fulvus x xxxxxxxxx Cecilioides acicula xxx Helix aspersa xxxxxxxxxx Oestophora barbula xxxxxxxxxx Oestophora lusitanica xx Otala lactea x xxx PPaginação_21.inddaginação_21.indd 212212 119-01-20129-01-2012 111:52:061:52:06 MARTINS: WHEN THE “FINCHES” ARE SNAILS 213 Species E/e N I Cor Flo Fai Pic Sjo Gra Ter Smg Sma Theba pisana xxxxxxxxxx Candidula intersecta xxx Caracollina lenticula xxxxxx Cernuella virgata xx Cochlicella barbara x xxxxxxxxx Helicella apicina xxx Heterostoma paupercula Mxxxx Leptaxis azorica E E Leptaxis caldeirarum E E Leptaxis drouetiana Exx Leptaxis minor E E Leptaxis sanctaemariae E E Leptaxis simia [=erubescens] Mxx Leptaxis terceirana EEE Leptaxis sp. eee Microxeromagna armillata M xxxxxxxxx Moreletina horripila E EEE EE Moreletina obruta E E Moreletina vespertina E EEE E Moreletina sp. a ee Moreletina sp. b eee ?Moreletina sp. a e e ?Moreletina sp. b e e ?Moreletina sp. c e e Lehmannia valentiana xxxxxxxxxx Limacus fl avus xxxxxxxxxx Limax maximus xxxxxxxxxx Milax gagates xxxxxxxxxx Punctum azoricum E EEEEEEEEE Lauria anconostoma x xxxxxxxxx Lauria