Genetic evidence for female host-specific races of the common cuckoo

Abstract

The common cuckoo Cuculus canorus is divided into host-specific races (gentes). Females of each race lay a distinctive egg type that tends to match the host's eggs, for instance, brown and spotted for meadow pipit hosts or plain blue for redstart hosts. The puzzle is how these gentes remain distinct. Here, we provide genetic evidence that gentes are restricted to female lineages, with cross mating by males maintaining the common cuckoo genetically as one species. We show that there is differentiation between gentes in maternally inherited mitochondrial DNA, but not in microsatellite loci of nuclear DNA. This supports recent behavioural evidence that female, but not male, common cuckoos specialize on a particular host, and is consistent with the possibility that genes affecting cuckoo egg type are located on the female-specific W sex chromosome. Our results also support the ideas that common cuckoos often switched hosts during evolution, and that some gentes may have multiple, independent origins, due to colonization by separate ancestral lineages.

Coevolution is linked with phenotypic diversification but not speciation in avian brood parasites

“…Our findings highlight the importance of using novel methods and phylogenies to re-evaluate previous findings, and further suggest that the number of subspecies is not necessarily correlated with the actual rates of speciation of a lineage. Although coevolution between brood parasites and their hosts may select for genetic divergence of brood parasites into female host races [38,39], or subspecies [19], this does not necessarily lead to accelerated rates of speciation. Speciation of host races may be constrained by incomplete assortative mating, as has been proposed for the common cuckoo [39] and the greater honeyguide [18].…”

Inheritance and variation in eggshell patterning in the great tit Parus major

“…In the common cuckoo, which parasitizes several species, interspeci¢c variation in host egg patterns has selected for a series of host-speci¢c lines of female cuckoo or gentes, whose eggs mimic those of that gens' host species (Wylie 1981). This suggests that gene loci for egg pattern lie on the femalespeci¢c W chromosome, with little or no contribution from the male line (Punnett 1933;Jensen 1966;Collias 1993;Gibbs et al 2000).…”

Indirect estimates of breeding and natal philopatry in an obligate avian brood parasite

“…These distances are similar in magnitude to the range of natal dispersal by migratory continental passerines near Ithaca and at other temperate study sites (Winkler et al 2005;Hoover and Reetz 2006) and are also similar to the geographic distance sampled in a previous analysis of avian spatial genetic structure, which detected significant decreases in relative relatedness at the scale of 1-10 km (*0.1 per 1 km; Woxvold et al 2006). We, therefore, suggest that, to address the biological relevance of the remaining alternative explanations regarding (1) versus (4) for our patterns reported here in Cowbirds, future work should combine (a) genetic analyses of both nuclear and mitochondrial markers to examine sex-specific patterns of dispersal (Marchetti et al 1998;Gibbs et al 2000;Daniel et al 2007) with (b) direct observations of the movements of identifiable brood parasite chicks of known sex (Tonra et al 2008). These latter methods will likely be a combination of mixing approaches of classical banding and resighting methods (Nice 1937;Smith and Arcese 1994;Anderson et al 2005) and recent technological developments in the individual tracking of small animals through long-life radio transmitters, satellite trackers, pit tags, geolocators, and long-distance transponders (Wikelski et al 2007;Stutchbury et al 2009).…”