Comparative phylogeography of Floreana’s lizards supports Galápagos
Pleistocene paleogeographical model and informs conservation management
decisions
Abstract
Terrestrial squamate reptiles from the Galápagos archipelago have
limited gene flow among islands, providing an opportunity to test
paleogeographic models. Previous work suggests that Pleistocene
glaciations had a strong influence on the evolution of Galápagos’
land-locked vertebrates, such as lizards and snakes, by allowing
dispersal and contact among populations from different islands or islets
through land connections. One prediction of this model is that extant
populations, despite being isolated at present, are genetically similar
due to recent (Pleistocene) gene flow. Here we test this prediction with
a simple comparative phylogeographic analysis of two sympatric lizards
from Floreana island and surrounding islets. Based on two mitochondrial
genes, we show that Floreana lava lizards (Microlophus grayii) and
leaf-toed geckos (Phyllodactylus baurii) from Floreana Island are very
similar genetically to conspecifics from Champion, an islet in the
Floreana group that was connected to Floreana during Pleistocene glacial
maxima. Moreover, they are significantly less similar to conspecifics
from Gardner, an islet in the Floreana group that was not in contact
with Floreana during Pleistocene glacial maxima. Thus, our results
support the idea of Pleistocene glaciation-driven contact among
populations from different islands in the Floreana cluster with no
identifiable subsequent dispersal. These results also show that Floreana
and Champion populations are part of the same evolutionary significant
unit for both species, which might be at risk due to an upcoming
invasive mammal eradication program in Floreana. Therefore, Champion
represents a reasonable source for potential reintroductions of both
lava lizards and leaf-toed geckos into Floreana.