Polygamy slows down population divergence in shorebirds

Abstract

Sexual selection may act as a promotor of speciation since divergent mate choice and competition for mates can rapidly lead to reproductive isolation. Alternatively, sexual selection may also retard speciation since polygamous individuals can access additional mates by increased breeding dispersal. High breeding dispersal should hence increase gene flow and reduce diversification in polygamous species. Here, we test how polygamy predicts diversification in shorebirds using genetic differentiation and subspecies richness as proxies for population divergence. Examining microsatellite data from 79 populations in 10 plover species (Genus: Charadrius) we found that polygamous species display significantly less genetic structure and weaker isolation‐by‐distance effects than monogamous species. Consistent with this result, a comparative analysis including 136 shorebird species showed significantly fewer subspecies for polygamous than for monogamous species. By contrast, migratory behavior neither predicted genetic differentiation nor subspecies richness. Taken together, our results suggest that dispersal associated with polygamy may facilitate gene flow and limit population divergence. Therefore, intense sexual selection, as occurs in polygamous species, may act as a brake rather than an engine of speciation in shorebirds. We discuss alternative explanations for these results and call for further studies to understand the relationships between sexual selection, dispersal, and diversification.

Latitudinal variation in biophysical characteristics of avian eggshells to cope with differential effects of solar radiation

“…The Kentish plover, as other polygamous plovers, exhibits low genetic structure and weak isolation‐by‐distance (D'Urban Jackson et al., ; Küpper et al., ; Oyler‐McCance, St. John, Kysela, & Knopf, ; Vidal, Hernández, Luis, & Domínguez, ). Despite gene flow, there may be geographic phenotypic divergence in response to changes in local conditions (Bech et al., ; Ritcher‐Boix, Teplitsky, Rogell, & Laurila, ), which may explain why eggshell spotting patterns are site‐specific.…”

Genetic isolation in an endemic African habitat specialist

“…For example, the Kittlitz's Plover exhibits high population connectivity and genetic homogeneity across Africa and its range overlaps that of the Chestnut‐banded Plover (D'Urban Jackson et al . 2017). We suggest that behavioural factors such as habitat specialization and mating behaviour may be responsible for maintaining isolation between Chestnut‐banded Plovers in southern and eastern Africa, and that unlike other Charadrius plovers, these behaviours may lead to non‐oceanic barriers restricting dispersal in this species.…”

“…2005) and therefore likely to exhibit a high degree of philopatry (Saalfeld & Lanctot 2015, D'Urban Jackson et al . 2017). This behaviour is in contrast to the behaviour of sequentially polygamous plovers, in which one parent deserts their brood shortly after hatching to remate, sometimes in a new location, leaving their partner to provide care for the offspring (Küpper et al .…”

“…Overall, greater genetic structure has been identified among monogamous than polygamous plover populations (D'Urban Jackson et al . 2017) and this may contribute to the lack of genetic mixing between populations of the Chestnut‐banded Plover.…”

“…2012, D'Urban Jackson et al . 2017). Patterns of phenotypic and genetic differentiation do not necessarily match, making subspecies and species delineation in this taxonomic group often challenging (Rheindt et al .…”