Detecting slow introgression of invasive alleles in an extensively restocked game bird

Abstract

Interbreeding of two species in the wild implies introgression of alleles from one species into the other only when admixed individuals survive and successfully backcross with the parental species. Consequently, estimating the proportion of first generation hybrids in a population may not inform about the evolutionary impact of hybridization. Samples obtained over a long time span may offer a more accurate view of the spreading of introgressed alleles in a species' gene pool. Common quail (Coturnix coturnix) populations in Europe have been restocked extensively with farm quails of hybrid origin (crosses with Japanese quails, C. japonica). We genetically monitored a common quail population over 15 years to investigate whether genetic introgression is occurring and used simulations to investigate our power to detect it. Our results revealed that some introgression has occurred, but we did not observe a significant increase over time in the proportion of admixed individuals. However, simulations showed that the degree of admixture may be larger than anticipated due to the limited power of analyses over a short time span, and that observed data was compatible with a low rate of introgression, probably resulting from reduced fitness of admixed individuals. Simulations predicted this could result in extensive admixture in the near future.

Hibridación entre la codorniz común (Coturnix coturnix) y la codorniz de granja: estado de un problema de conservación

“…Forty-two mtDNA haplotypes were identified among the studied samples (GenBank accession numbers: KP797932 to KP797972), 13 of which matched shorter, previously described haplotypes (Fumihito et al, 1996;Barilani et al, 2005;Sanchez-Donoso et al, 2014), while 29 haplotypes did not match any previously described haplotype. The low quality of one of the sequences forced us to exclude it from the phylogenetic tree (Fig.…”

“…Since previous analyses showed that farm-reared quail have Japanese mtDNA haplotypes (Barilani et al, 2005;Amaral et al, 2007;Sanchez-Donoso et al, 2014), the three wintering individuals detected with a Japanese quail mtDNA haplotype and a farm-like genotype probably represent individuals raised in farms and released for hunting. Our results suggest that farm quail used for restocking experience marked mortality after their release, since they do not form a significant part of the migratory or wintering population.…”

“…The presence of both the common quail nuclear genome and Japanese quail mitochondrial DNA in the same individual indicates introgression. Such individuals are the result of an old cross between a farm female [with domestic Japanese quail mtDNA (Barilani et al, 2005;Amaral et al, 2007;Sanchez-Donoso et al, 2014)] and a wild common quail male whose female descendants had been repeatedly backcrossing with common quail males to the point that the nuclear DNA of the offspring became indistinguishable from that of common quail. Thus, although most domestic Japanese quail and their hybrids do not show migratory restlessness (Derégnaucourt, 2000;Derégnaucourt et al, 2005aDerégnaucourt et al, , 2000b, the offspring of old crosses with farm individuals could become part of the migrant population.…”

Admixture between released and wild game birds: a changing genetic landscape in European mallards (Anas platyrhynchos)

“…We argue that these are the result of hybridization in the wild rather than being individuals already admixed at release (cf. Sanchez-Donoso et al 2014). The main argument for this is that no admixed individuals were found in the Czech farmed population, although they could be found in the Czech wild group.…”

Diet of released captive-bred North-African houbara bustards

“…Up to date, researches on the heritability of traits in the houbara captive breeding focussed on reproductive traits (Chargé et al 2013); however, more researches are needed regarding other phenotypes associated to the fitness of released individuals, as for example, their foraging behaviour or digestive ability. Nonetheless, the risk of introgression of maladaptive/deleterious allele in the wild is often low as fitness of such released animals is expected to be low and their contribution to the effective population is likely to be insignificant (Araki et al 2007;Casas et al 2012;Ford 2002;Puigcerver et al 2014;Sanchez-Donoso et al 2014). Despite globally encouraging results, the "cost of release" (Tavecchia et al 2009) might remain important especially under harsh environmental conditions , and most of mortality events occur in the 15 days after the release (ECWP unpublished data).…”