Limited Population Structure, Genetic Drift and Bottlenecks Characterise an Endangered Bird Species in a Dynamic, Fire-Prone Ecosystem

Abstract

Fire is a major disturbance process in many ecosystems world-wide, resulting in spatially and temporally dynamic landscapes. For populations occupying such environments, fire-induced landscape change is likely to influence population processes, and genetic patterns and structure among populations. The Mallee Emu-wren Stipiturus mallee is an endangered passerine whose global distribution is confined to fire-prone, semi-arid mallee shrublands in south-eastern Australia. This species, with poor capacity for dispersal, has undergone a precipitous reduction in distribution and numbers in recent decades. We used genetic analyses of 11 length-variable, nuclear loci to examine population structure and processes within this species, across its global range. Populations of the Mallee Emu-wren exhibited a low to moderate level of genetic diversity, and evidence of bottlenecks and genetic drift. Bayesian clustering methods revealed weak genetic population structure across the species' range. The direct effects of large fires, together with associated changes in the spatial and temporal patterns of suitable habitat, have the potential to cause population bottlenecks, serial local extinctions and subsequent recolonisation, all of which may interact to erode and homogenise genetic diversity in this species. Movement among temporally and spatially shifting habitat, appears to maintain long-term genetic connectivity. A plausible explanation for the observed genetic patterns is that, following extensive fires, recolonisation exceeds in-situ survival as the primary driver of population recovery in this species. These findings suggest that dynamic, fire-dominated landscapes can drive genetic homogenisation of populations of species with low-mobility and specialised habitat that otherwise would be expected to show strongly structured populations. Such effects must be considered when formulating management actions to conserve species in fire-prone systems.

Life history influences how fire affects genetic diversity in two lizard species

“…Maintenance of gene flow through dispersal in fireprone ecosystems may be an adaptation to temporally dynamic habitats (Pierson et al 2010;Brown et al 2013;Pereoglou et al 2013). Fire mosaics did not appear to form dispersal barriers in either of our study species, supporting this suggestion.…”

“…; Brown et al . ). For example, in early successional species, limited genetic structure at large spatial scales suggests that high dispersal rates allow rapid colonization of recently burnt habitats (Pereoglou et al .…”

“…Other factors that may influence gene flow, such as population density (Konvicka et al 2012), topography (Cushman et al 2006) and geographical distance (Wright 1943), can be incorporated into landscape genetics analyses, with fire mosaics, to understand the factors influencing genetic structure . This approach has shown how fire influences genetic diversity and spatial genetic structure of some animal species (Spear & Storfer 2010;Schrey et al 2011a;Brown et al 2013). For example, in early successional species, limited genetic structure at large spatial scales suggests that high dispersal rates allow rapid colonization of recently burnt habitats (Pereoglou et al 2013;Pierson et al 2013).…”

Witnessing extinction: Population genetics of the last European Rollers ( Coracias garrulus ) in Austria and a first phylogeographic analysis of the species across its distribution range

“…We therefore assume that they were present in the Austrian population also before 2014 but were not passed on to offspring until then; either because their carriers only reproduced in later years or because the alleles were present in heterozygous individuals and only the other allele was passed on before 2014/15. While not as low as predicted, heterozygosity in Austrian European Rollers is comparable to values found in endangered bird species (Brown, Harrisson, Clarke, Bennett, & Sunnucks, ; Hughes, ). Compared to the Hungarian/Serbian population, heterozygosity in 2005 and 2007 (disregarding the latest numbers from 2014/15, see above) was ca.…”

Identifying the location of fire refuges in wet forest ecosystems

“…Fire refuges may be especially important for fauna that are dependent on mature vegetation features, such as tree hollows for nesting or denning (Banks et al 2011b). The likelihood of a location acting as a refuge will depend on individual species characteristics, such as competitive behavior and dispersal ability (Brown et al 2013). Fire refuges may ensure that ecosystem functions provided by species remain in the landscape (Nugent et al 2014).…”