Highly variable reproductive isolation among pairs ofCatostomusspecies

Abstract

Hybridization between diverged taxa tests the strength of reproductive isolation, and can therefore reveal mechanisms of reproductive isolation. However, it remains unclear how consistent reproductive isolation is across species’ ranges, and to what extent reproductive isolation might remain polymorphic as species diverge. To address these questions, we compared outcomes of hybridization across species pairs of Catostomus fishes in three rivers in the Upper Colorado River basin, where an introduced species, C. commersoni, hybridizes with at least two native species, C. discobolus and C. lattipinis. We observed substantial heterogeneity in outcomes of hybridization, both between species pairs and across geographically separate rivers within each species pair. We also observed hybridization of additional related species with our focal species, suggesting that reproductive isolation in this group involves interactions of multiple evolutionary and ecological factors. These findings suggest that a better understanding of the determinants of variation in reproductive isolation is needed, and that studies of reproductive isolation in hybrids should consider how the dynamics and mechanisms of reproductive isolation vary over ecological space and over evolutionary time. Our results also have implications for the conservation and management of native catostomids in the Colorado River basin. Heterogeneity in outcomes of hybridization suggests that the threat posed by hybridization and genetic introgression to the persistence of native species likely varies with extent of reproductive isolation, both across rivers and across species pairs.

Full Issue

“…Although we found differences in the aggressive behavior between Red-naped and Red-breasted sapsuckers, with Red-naped having significantly higher levels of acoustic aggression compared to Redbreasted, these differences were not consistent with our predictions, thus species interactions are unlikely to contribute to hybrid zone movement. Our findings also highlight the independence of different hybrid systems, with heterogeneity in the outcome of hybridization in different parts of the ranges of species (Seneviratne et al 2012, Mandeville et al 2015, Grossen et al 2016). …”

What, if anything, are hybrids: enduring truths and challenges associated with population structure and gene flow

“…; Mandeville et al. ). Somewhat similarly, categorical treatment of ancestry in hybrids leads to overlapping expectations for and q in , , and individuals, but analysis of their allelic states shows that individuals differ genetically from early generations (PCA in Fig.…”

“…; Mandeville et al. ). For both applied and basic evolutionary biology, this variability in outcomes means that it can be difficult to formulate categorical statements about the composition, importance, and likely conservation threats of hybrids.…”

“…; Mandeville et al. ). Additionally, we have learned more about models and approaches that can be used to describe patterns of variation in hybrids (Patterson et al.…”

Hybrid dynamics in a species group of swallowtail butterflies

“…Despite growing understanding of hybrid zone dynamics, however, the complexity of such zones of genomic recombination precludes straightforward identification and classification of hybrid individuals in nature (e.g. Lowe et al ., and references therein , Mandeville et al ., ).…”