Amphibian phylogeography: a model for understanding historical aspects of species distributions

Abstract

Phylogeographic analysis has become a major tool for investigating historical aspects of biogeography and population genetic structure. Anuran amphibians are particularly informative subjects for phylogeographic research on account of their global distribution, high degree of population genetic structure and ease of sampling. Studies on all the world's inhabited continents have demonstrated the nature and locations of refugia, including the Gulf Coast in North America and the Mediterranean peninsulas in Europe during the Pleistocene glaciations; the importance of vicariance events such as the uplift of the Andes in shaping modern distributions; and colonization routes in temperate zones during postglacial climatic amelioration. Features identified as important to amphibian biogeography, notably mountain ranges, large rivers such as the Amazon and climatic fluctuations, are common to many other taxa. New analytical methods based on coalescent, Bayesian and likelihood approaches permit more rigorous hypothesis testing than has hitherto been possible and offer the prospect of even more detailed insights into species and population history in future work.

Radiation of the polymorphic Little Devil poison frog (Oophaga sylvatica) in Ecuador

“…Those populations are geographically distant from each other, ranging from 20 km between Simón Bolívar and Puerto Quito to as much as 190 km between Quingüe and La Maná, have low but significant F ST values from ddRAD data (Appendix S2, Table S5), and are genetically well differentiated on the DAPC analysis. As amphibians usually have low dispersal abilities (Zeisset & Beebee, 2008) and Dendrobatidae, like most frogs, are not known to be migratory species, the low levels of differentiation observed with the mitochondrial markers are unlikely to have occurred as a result of gene flow. In addition, this low genetic variation combined with high phenotypic diversity among geographically distant population suggests that the southern cluster likely had a rapid radiation occurring within the last 2.1–2.5 Ma (Santos et al., 2009).…”

During the reign of frogs and toads

“…The island of Madagascar was attached to Africa until approximately 150 million years ago, and the Mascarene ridged frog is one of the few species found in both places. Zeisset and Beebee (2008) highlight the fact that several Madagascar ridged frog haplotypes are absent from Africa, suggesting the natural colonization of Madagascar by transoceanic dispersal after its separation from Africa, but long before humans arrived.…”

“…Zeisset and Beebee (2008) find, rather unexpectedly, that Pleistocene (less than 1.8 million years ago) refugia in the Pacific northwest appear to have been forested river valleys within the cold mountain zones for tailed frogs and a host of other cold-tolerant species, including plants, mammals and reptiles.…”

“…Advances in analytical methods combine the low individual mobility and global (except Antarctica) distribution of anurans to make them excellent systems for testing speciation hypotheses and inferring population histories. In a recent issue of Heredity, Zeisset and Beebee (2008) reviewed how molecular markers provided insights into how late tertiary and quaternary (within the past 65 million years) conditions influenced biogeographical processes affecting anurans. They focused on the contrast between the northern temperate and the tropical/ southern temperate zones.…”

“…Various hypotheses for the biogeographical patterns observed are still debated: the influence of the Amazonian rivers; the effects of tectonic movements and sea level fluctuations; refugia during the proposed Pleistocene arid cycles and competitive interactions between species during Pleistocene cool periods. Zeisset and Beebee (2008) suggest that there may be a primary distinction between the more recent quaternary events (such as temperature fluctuation) acting on upland anurans, for example, harlequin toads, and earlier paleogeographic events, such as the Andean uplift and marine incursions that altered the direction of the Amazon, having a greater influence on lowland species, that is, poison frogs. Several recent studies have determined that the lineage divergence across several animal groups in the geologically complex Amazon Basin is best understood by the combination of two or more of these hypotheses (Aleixo, 2004;Noonan and Wray, 2006;Conn and Mirabello, 2007).…”