Genetic structure among remnant populations of a migratory passerine, the Northern Wheatear Oenanthe oenanthe

Abstract

Continuous animal populations often become fragmented due to anthropogenic habitat alterations. These small, fragmented populations are fragile due to demographic and genetic factors, whereas immigration can enhance their long‐term viability. Previously, we showed that high philopatry affected the local dynamics of three small and remnant subpopulations of Northern Wheatears in The Netherlands. Here, we show that these three populations together with an additional larger population in the European lowlands are highly genetically differentiated based on 22 microsatellite markers. In contrast, we found no evidence for differentiation using two mitochondrial DNA markers. An IMa2 analysis indicates that gene flow has occurred regularly among our sampled populations. As immigration of colour‐ringed birds among our sampled populations is rare at best, our results suggest that the populations have recently become isolated from one another. Low dispersal rates in highly mobile birds may occur when suitable habitat becomes highly fragmented, and will accentuate stochastic demographic processes and inbreeding, both reducing population viability. As dispersal rates are low among populations of Northern Wheatears in The Netherlands, there is only a small probability of recolonization of habitat patches where populations have become locally extinct.

Parallel plumage colour evolution and introgressive hybridization in wheatears

“…The possible extent of philopatry in wheatears remains unclear. On one hand, adult Cyprus wheatears only rarely change habitats between breeding seasons (Xenophontos & Cresswell, ), and some populations of northern wheatear ( O. oenanthe )—a species belonging to the same clade within Oenanthe (Aliabadian et al., )—are rather philopatric (van Oosten, Mueller, Ottenburghs, Both, & Kempenaers, ). On the other hand, estimates of average breeding and natal dispersal distances of the latter species are only slightly lower than ones of species such as pied flycatcher ( Ficedula hypoleuca ) and barn owl ( Tyto alba ; Paradis, Baillie, Sutherland, & Gregory, ) that display very shallow intraspecific population structures even at continental scales (Burri et al., , ; Lehtonen et al., ).…”

Hatching failure and accumulation of organic pollutants through the terrestrial food web of a declining songbird in Western Europe

“…In The Netherlands, monitoring over six years revealed consistently high hatching failure of eggs in one of the remnant populations situated in a coastal nature reserve where on average 20% of eggs failed to hatch. However, despite the small population size and low population growth, genetic variation (heterozygosity) is still high in this population (Van Oosten et al, 2016), suggesting that inbreeding alone is not likely the main cause of the observed high hatching failure. Although the extent to which heterozygosity, based on markers and as proxy for individual inbreeding coefficients (rather than pedigree-based estimates inbreeding coefficients), is debated (Chapman et al, 2009;Szulkin et al, 2010;Taylor et al, 2010), it seems likely that other factors may be involved in the decreased hatchability of the eggs.…”

“…The correlation between heterozygosity in certain markers and fitness of an individual is often weak (Chapman et al, 2009;Szulkin et al, 2010). This could mean that fitness of Dutch Northern Wheatears may still be low, despite the relatively high heterozygosity values (Van Oosten et al, 2016). Inbreeding may be suspected because of small contemporary population size and because exchange of colour-ringed individuals between populations is rare (Van Oosten et al, 2015).…”

Locally adapted migration strategies? Comparing routes and timing of northern wheatears from alpine and lowland European populations

“…Both findings suggest that the migration routes and timing of Alpine populations is less the result of an expansion from the ancestral refuge population during the last glacial period, but rather an adaptation to the cooler climate at high elevation. The similarity in timing of migration between populations at high altitude and high latitude is another example of how the local environment might have strong selective power in this species, leading to homologous adaptations which make disentangling the evolutionary relationships between populations all the more challenging (van Oosten et al 2016, Wang et al 2020).…”