Low genetic and morphological differentiation between an introduced population of dunnocks in New Zealand and an ancestral population in England

Abstract

Species invasions and exotic species introductions can be considered as 'unplanned experiments', which help us to understand the evolution of organisms. In this study, we investigated whether an exotic bird species, the dunnock (Prunella modularis), has diverged genetically and morphologically from its native source population (Cambridge, England) after introduction into a new environment (Dunedin, South Island of New Zealand; exotic population). We used a set of microsatellite markers and three morphological traits to quantify the divergence between these two populations. We quantified neutral genotypic differentiation between the populations, and also used an individual-based Bayesian clustering method to assess genetic structure. We compared morphological divergence using univariate and principal components analyses. We found that individuals from the Dun edin population are genetically distinct from the Cambridge population, but levels of differentiation are very low. Overall within-population levels of genetic diversity are low compared to other bird species, and effective population sizes are small; indicating that the native population probably has a historically low level of genetic diversity, and that the introduced population retained most of that diversity after its introduction into New Zealand. We found little evidence of morphological divergence, and the evolutionary rate of change in these traits is below the average for other taxa. Our study adds support to the growing literature showing that invasive species maintain most of their initial genetic diversity after multiple founder events, even when population size is severely reduced. Moreover, our morphological data indicate slow evolutionary rates in species introduced to similar habitats.

Breeding Biology and Variable Mating System of a Population of Introduced Dunnocks (Prunella modularis) in New Zealand

“…Data from a dunnock population in Southern New Zealand suggest little genetic and morphological divergence from a native population in England [23].…”

Population differentiation and behavioural association of the two ‘personality’ genesDRD4andSERTin dunnocks (Prunella modularis)

“…In the UK and NZ, dunnocks can often be found in public parks, gardens and cultivated areas, in which they defend small territories all year round (Davies ; Santos et al . ).…”

“…Although dunnocks of these two populations show only low genetic (measured by microsatellites) and morphological differentiation (Santos et al . ), differences in behaviour are readily detectable. For instance, dunnocks in Cambridge are unobtrusive and mostly seen foraging in dense vegetation (Davies ; N. E. Langmore, personal communication cited in Cockburn ), whereas dunnocks in Dunedin are conspicuous and preferentially forage on open lawns (B. Holtmann & C. E. Lara, personal observations).…”

Conflict and cooperation over sex: the consequences of social and genetic polyandry for reproductive success in dunnocks

“…At this study site, current effective population size has been estimated at 54 breeding individuals (Santos et al . ). We collected data for this study between July 2009 and January 2012, comprising three breeding seasons: 2009–2010, 2010–2011 and 2011–2012.…”

“…Given the low genetic diversity of dunnock populations in general (Santos et al . ), inbreeding is likely to have negative fitness consequences. Furthermore, somewhat restricted dispersal in our population (Santos & Nakagawa ; pers.…”