2016-12-23T18:52:10

Morphological systematics makes it clear that many non-volant animal groups have undergone extensive transmarine dispersal with subsequent radiation in new, often island, areas. However, details of such events are often lacking. Here we use partial DNA sequences derived from the mitochondrial cytochrome b and 12S rRNA genes (up to 684 and 320 bp, respectively) to trace migration and speciation in Tarentola geckos, a primarily North African clade which has invaded many of the warmer islands in the North Atlantic Ocean. There were four main invasions of archipelagos presumably by rafting. (i) The subgenus Neotarentola reached Cuba up to 23 million years (Myr) ago, apparently via the North Equatorial current, a journey of at least 6000 km. (ii) The subgenus Tarentola invaded the eastern Canary Islands relatively recently covering a minimum of 120 km. (iii) The subgenus Makariogecko got to Gran Canaria and the western Canary Islands 7^17.5 Myr ago, either directly from the mainland or via the Selvages or the archipelago of Madeira, an excursion of 200^1200 km. (iv) A single species of Makariogecko from Gomera or Tenerife in the western Canaries made the 1400 km journey to the Cape Verde Islands up to 7 Myr ago by way of the south-running Canary current. Many journeys have also occurred within archipelagos, a minimum of ¢ve taking place in the Canaries and perhaps 16 in the Cape Verde Islands. Occupation of the Cape Verde archipelago ¢rst involved an island in the northern group, perhaps Sa¬ o Nicolau, with subsequent spread to its close neighbours. The eastern and southern islands were colonized from these northern islands, at least two invasions widely separated in time being involved. While there are just three allopatric species of Makariogecko in the Canaries, the single invader of the Cape Verde Islands radiated into ¢ve, most of the islands being inhabited by two of these which di¡er in size. While size di¡erence may possibly be a product of character displacement in the northern islands, taxa of di¡erent sizes reached the southern islands independently.

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The scincid lizards of the Cape Verde islands comprise the extinct endemic giant Macroscincus coctei and at least ¢ve species of Mabuya, one of which, Mabuya vaillanti, also had populations with large body size. Phylogenetic analysis based on DNA sequences derived from the mitochondrial cytochrome b, cytochrome oxidase I and 12S rRNA genes (711, 498 and 378 base pairs (bp), respectively) corroborates morphological evidence that these species constitute a clade and that Macroscincus is unrelated to very large skinks in other areas. The relationships are ((M. vaillanti and Mabuya delalandii) (Mabuya spinalis and Macroscincus coctei (Mabuya fogoensis nicolauensis (Mabuya fogoensis antaoensis and Mabuya stangeri)))). The Cape Verde archipelago was colonized from West Africa, probably in the Late Miocene or Early Pliocene period. The north-eastern islands were probably occupied ¢rst, after which the ancestor of M. vaillanti and M. delalandii may have originated on Boavista, the ancestor of the latter species arriving on Santiago or Fogo later. The M. fogoensis^M. stangeri clade colonized the islands of Branco, Razo, Santa Luzia and Sa¬ o Vicente from Sa¬ o Nicolau and reached Santo Anta¬ o after this. Colonization of these northeastern islands was slow, perhaps because the recipient islands had not developed earlier or because colonization cut across the path of the Canary Current and the Northeast Trade Winds, the main dispersing agents in the region. Rapid extension of range into the southwestern islands occurred later in M. spinalis and then in M. vaillanti and M. delalandii. The long apparent delay between the origin of these species and their southwestern dispersal may have been because there were earlier colonizations of the southern islands which excluded later ones until the earlier inhabitants were exterminated by volcanic or climatic events. The evolution of large size in Macroscincus occurred in the northwestern islands and was paralleled in the eastern and southern islands by populations of M. vaillanti. Both cases of size increase in Cape Verde skinks were accompanied by the development of herbivory.