First steps in a project integrating phylogeny, climate,geological history and dispersion dynamics, to explain the phylogeography of the genus Batrachoseps

Abstract

The slender salamanders genus, Batrachoseps (Plethodontidae), is the most speciose groupof caudate amphibians in the western nearctic zone. All clades and even species within these groupsshow a marked phylogeographic structure, although there is often a discrepancy between mtDNAand nDNA (allozymes) datasets. Batrachoseps species are morphologically cryptic and ecologicallyvery similar. Slender salamander species do not merge when a parapatry occurs and sympatry islimited especially within clades, so that they seem to replace each other spatially. Several elementsgive insight about the diversification processes of this genus and the non-adaptive radiationhypothesis, where non-ecological speciation occurs, seems likely. To all appearances isolationperiods following fragmentation could have have been amply long to create a divergence, greatenough to prevent populations from merging and efficiently hybridizing. However the non-adaptivehypothesis has not been studied yet from an environmental niche point of view. Methods frominvasive species niche studies are adapted and ordination techniques are used in order to compareand illustrate the environmental niches of slender salamanders based on several climatic variables.Through these comparisons, predictions made by the non-adaptive hypothesis are tested with anincreasing complexity and rigor in the methodology. The biological significance of theseenvironmental niche metrics and tests is discussed within a conceptual context and hypothesesabout the reasons why our first hypothesis could be true while leading to our results are formulated.Finally an experimental ecology perspective is given and the integration of this study in a widerproject is highlighted