Conservation genetics of the central newt (Notophthalmus viridescens) in Iowa: the importance of a biogeographic framework

In light of global declines in amphibian populations, genetic data have become increasingly important for understanding population structure and for revealing hidden diversity. At the species level, Notophthalmus viridescens is an IUCN species of “least concern”, but the subspecies N. v. louisianensis (central newt) is listed as “threatened” in Iowa, a state on the western periphery of the species range. Genetic data were collected from 282 N. v. louisianensis from 14 sites in Iowa. Sequences from 1,054 nucleotides of mitochondrial DNA from Iowa newts revealed unexpected diversity in the form of two major haplotype groups that are not sister clades, with southern Iowa N. v. louisianensis being more closely related to N. v. piaropicola (peninsula newt) from Florida than to consubspecifics in Iowa. Sequence differentiation indicates that the two lineages of newts present in Iowa diverged near the beginning of the Pleistocene. Northern and southern Iowa haplotypes were found together at one site, indicating an opportunity for hybridization near Remington’s biogeographic suture zone 1, a hotspot for hybridization in other species. Three microsatellite loci provided additional evidence for distinctness of northern and southern Iowa newt populations. This study highlights the relevance of historical biogeography to conservation, as management strategies for N. v. louisianensis in Iowa must reflect previously unrecognized diversity in this species. Nuclear and mitochondrial data indicate genetic isolation of nearby populations on the same drainage, and field data suggest the decline of one study population, emphasizing the need for identification and protection of newt breeding sites in Iowa.