Male and female contributions to behavioral isolation in darters as a function of genetic distance and color distance.

Rachel L Moran,Julian M Catchen,Rebecca C Fuller,Muchu Zhou

doi:10.1111/evo.13321

Abstract

Determining which reproductive isolating barriers arise first between geographically isolated lineages is critical to understanding allopatric speciation. We examined behavioral isolation among four recently diverged allopatric species in the orangethroat darter clade (Etheostoma: Ceasia). We also examined behavioral isolation between each Ceasia species and the sympatric rainbow darter Etheostoma caeruleum. We asked (1) is behavioral isolation present between allopatric Ceasia species, and how does this compare to behavioral isolation with E. caeruleum, (2) does male color distance and/or genetic distance predict behavioral isolation between species, and (3) what are the relative contributions of female choice, male choice, and male competition to behavioral isolation? We found that behavioral isolation, genetic differentiation, and male color pattern differentiation were present between allopatric Ceasia species. Males, but not females, discerned between conspecific and heterospecific mates. Males also directed more aggression toward conspecific rival males. The high levels of behavioral isolation among Ceasia species showed no obvious pattern with genetic distance or male color distance. However, when the E. caeruleum was included in the analysis, an association between male aggression and male color distance was apparent. We discuss the possibility that reinforcement between Ceasia and E. caeruleum is driving behavioral isolation among allopatric Ceasia species.

Highlights

Speciation requires the evolution of reproductive isolating barriers between taxa (Mayr 1995)
We visually examined the plots of behavioral isolation versus DST (Fig. 3) and behavioral isolation versus male color distance (Fig. 4) to determine whether any trends existed among the three Ceasia-Ceasia species comparisons and among the four
The same general pattern was observed for attacks, but focal males performed significantly more attacks toward conspecific than heterospecific Ceasia only in the E. fragi—E. burri—E. caeruleum species set

Summary

Introduction

Speciation requires the evolution of reproductive isolating barriers between taxa (Mayr 1995). Time since divergence, differences in ecology, reinforcement, and pronounced sexual selection via female mating preferences all favor enhanced reproductive isolation. We consider the other side of the coin and ask how reproductive isolation evolves in recently diverged allopatric taxa that occupy similar environmental niches, and that (as of yet) lack evidence of female mating preferences. Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution B E H AV IORALISOL AT IONIN DA RT E R S whether there is evidence that genetic distance (a surrogate for time since divergence) and/or sexual selection can account for the levels of reproductive isolation seen among allopatric taxa

Methods

Results

Conclusion