Considering alternative life history modes and genetic divergence in conservation: a case study of the Oklahoma salamander

Alternative life history strategies can provide important variation for the long-term persistence of a lineage. However, conservation of such lineages can be complicated because each life history mode may have different habitat requirements and may be vulnerable to different environmental perturbations. The Oklahoma salamander (Eurycea tynerensis) is endemic to the Ozark Plateau of North America, and has two discrete life history modes, biphasic (metamorphic) and aquatic (paedomorphic). Until recently, these modes were considered separate species and conservation attention focused only on paedomorphic populations. We perform phylogenetic analyses of the mitochondrial gene cytochrome b (Cytb) and nuclear gene proopiomelanocortin (POMC) to assess patterns of historical isolation in E. tynerensis, and test whether life history mode is randomly distributed with respect to the phylogeny and geography. We find three divergent Cytb lineages and significant shifts in POMC allele frequencies between the eastern, western, and southwestern portions of the distribution. Life history mode varies extensively, but paedomorphosis is largely restricted to the widespread western clade. Therefore, the two most divergent and narrowly distributed clades (southwestern and eastern) were previously overlooked due to their metamorphic life history. Paedomorphosis has allowed E. tynerensis to drastically increase its niche breadth and distribution size. Nevertheless, metamorphosis is also an important attribute, and metamorphic populations are the ultimate source for paedomorphic evolution. Preservation of divergent genetic lineages, and regions that include adjacent habitat for both life history modes, may be the most effective way to maintain historical and adaptive variation and provide gateways for ongoing life history evolution.