Correspondence between sexual isolation and allozyme differentiation: a test in the salamander Desmognathus ochrophaeus.

Abstract

Ethological reproductive isolation and genetic divergence across 26 protein loci were measured among populations of the salamander Desmognathus ochrophaeus in the southern Appalachian Mountains. Levels of ethological isolation varied from none to complete and were statistically significant for all but two pairings between populations inhabiting different mountain ranges. When geographic and genetic distances were treated as independent variables in multiple correlation analyses, they accounted for about halfthe variance in levels of ethological isolation. When genetic distance is held constant, the remaining relationship between ethological isolation and geographic distance is still statistically significant. When geographic distance is held constant, the remaining relationship between genetic distance and levels of ethological isolation is nonsignificant, as is the relationship between geographic distance and genetic distance when ethological isolation is held constant. Ethological isolation and genetic divergence evidently both reflect the gradual divergence of allopatric populations, but genetic distance is a poor predictor of ethological isolation in these salamanders.

Coupling, Reinforcement, and Speciation

“…However, it is also important to study weaker overall barriers-or even to compare populations with no known barrier a priori-in order to document the pattern of origin of individual barrier effects and, especially, to ask whether initial stages of divergence often include noncoincident barrier effects, as in the Ostrinia example mentioned above. Some studies have examined the increase in barrier effects with geographic (e.g., Tilley et al 1990) or ecological (Nosil et al 2009) distance, or in preplanned comparisons that reflect population history (Tregenza et al 2000). Crosses between populations sometimes reveal unexpected and strong barrier effects (e.g., Jennings et al 2014).…”

Patterns of Reproductive Isolation in Three Angiosperm Genera

“…Three apparently common patterns are of particular interest here. First, analyses of the relationship between reproductive isolation and genetic distance in animal systems (Coyne andOrr 1989, 1997;Tilley et al 1990;Gleason and Ritchie 1998;Sasa et al 1998;Presgraves 2002;Mendelson 2003) have indicated that the magnitude of reproductive isolation between species pairs is generally positively associated with genetic distance, and therefore presumably with time since species divergence. Although classical plant studies have demonstrated the general association between reproductive isolation and differentiation in other-often quanti-tative-genetic traits (Clausen and Hiesey 1958;Levin 1978;Vickery 1978), the direct association between genetic distance and reproductive isolation has not been systematically examined in plant taxa.…”

Nested biological variation and speciation

“…Geographic variation in the sexual behaviour of the dusky salamander, Desmognathus ochrophaeus, and associated patterns of reproductive isolation across populations have been particularly well-studied (Houck et al 1985(Houck et al , 1988Verrell & Arnold 1989;Tilley et al 1990). The dusky salamander is distributed across mountaintops of the eastern United States from New York to northern Georgia.…”

“…Populations of the dusky salamander also exhibit a complete range of ethological compatibilities, ranging from full compatibility to complete incompatibility (Houck et al 1988;Verrell & Arnold 1989;Tilley et al 1990). A survey in which levels of ethological isolation between populations from 11 southern Appalachian sites (31 crosses total) were interpreted in the context of genetic di¡erentiation (26 protein loci) and geographic distance, demonstrated that geographic distance was the best predictor of the degree of reproductive isolation.…”

“…The ethological basis of mating failure in heterotypic matings usually involved a failure of the male to initiate courtship or a failure later in the courtship sequence (Verrell & Arnold 1989). Unlike the case for the lacustrine pairs of stickleback, there is little to suggest that natural selection has contributed substantially to the divergence in D. ochrophaeus (Tilley et al 1990;Verrell & Arnold 1989;P. A. Verrell, personal communication).…”