Eastward from Africa: palaeocurrent-mediated chameleon dispersal to the Seychelles islands

Abstract

Madagascar and the Seychelles are Gondwanan remnants currently isolated in the Indian Ocean. In the Late Cretaceous, these islands were joined with India to form the Indigascar landmass, which itself then split into its three component parts around the start of the Tertiary. This history is reflected in the biota of the Seychelles, which appears to contain examples of both vicariance- and dispersal-mediated divergence from Malagasy or Indian sister taxa. One lineage for which this has been assumed but never thoroughly tested is the Seychellean tiger chameleon, a species assigned to the otherwise Madagascar-endemic genus Calumma . We present a multi-locus phylogenetic study of chameleons, and find that the Seychellean species is actually the sister taxon of a southern African clade and requires accomodation in its own genus as Archaius tigris . Divergence dating and biogeographic analyses indicate an origin by transoceanic dispersal from Africa to the Seychelles in the Eocene–Oligocene, providing, to our knowledge, the first such well-documented example and supporting novel palaeocurrent reconstructions.

Large-scale phylogeny of chameleons suggests African origins and Eocene diversification

“…All analyses strongly supported the Malagasy leaf chameleon genus Brookesia as the sister group to a large clade comprising all other chameleon genera, consistent with other recent studies that have incorporated nuclear DNA data [29,30,55].…”

“…Given these considerations, an African origin for chameleons is not only plausible, but is also consistent with the fossil record, present day distributions and oceanographic processes. Indeed, dated phylogenetic analyses using multiple markers and complete generic-level taxon sampling strongly suggest an Eocene out-of-Africa dispersal of one chameleon genus to the Seychelles [29], rather than the out-of-Madagascar dispersal previously proposed [14].…”

“…The initial divergence of Chamaeleonidae into the Malagasy genus Brookesia and a clade composed of all other genera is supported in most molecular phylogenetic analyses to date [15,29,30]. However, relationships among the remaining chameleon genera still lack a well-supported phylogenetic hypothesis, possibly owing to a lack of extensive taxon sampling and inclusion of too few markers, or possibly because a rapid initial radiation caused a 'true' polytomy [14,15,[29][30][31].…”

“…However, relationships among the remaining chameleon genera still lack a well-supported phylogenetic hypothesis, possibly owing to a lack of extensive taxon sampling and inclusion of too few markers, or possibly because a rapid initial radiation caused a 'true' polytomy [14,15,[29][30][31]. Analyses with extensive taxon sampling are limited to single genera [30,[32][33][34][35], and these have usually recovered Oligocene/ Miocene origins for genera.…”

No longer single! Description of female Calumma vatosoa (Squamata, Chamaeleonidae) including a review of the species and its systematic position

“…Of the currently described 202 chameleon species, 86 species belong to the four Malagasy genera Brookesia Gray, 1865, Calumma Gray, 1865, Furcifer Fitzinger, 1843, and Palleon Glaw, Hawlitschek & Ruthensteiner, 2013, and all but two Comorian species of Furcifer are endemic to Madagascar (Glaw 2015). Although the Seychelles chameleon, Archaius tigris (Kuhl, 1820), was included in the genus Calumma until recently, Townsend et al (2011) demonstrated that it represents a different African lineage and that Calumma is endemic to Madagascar. The Malagasy chameleons were relatively intensively studied in the past (Brygoo 1971(Brygoo , 1978, but still many new species are regularly dis-the type locality (Forêt de Tsararano).…”