Unexpected persistence on habitat islands: genetic signatures reveal dispersal of a eucalypt‐dependent marsupial through a hostile pine matrix

Abstract

Several factors contribute to the extinction of populations in fragmented habitat but key ones include habitat loss and disruptions to connectivity. Aspects of the ecology of greater gliders (Petauroides volans), along with observations of their response to native forest clearance at a site in southeastern Australia, lead to the prediction in the 1960s that the species would not persist in the replacement exotic pine plantation. However, 35 years later, the species was observed in many remnant native vegetation patches retained within the plantation boundary, albeit at a lower occupancy rate than at matched continuous forest control sites. To determine the role of patch connectivity in persistence of P. volans in remnants, we employed 12 microsatellite markers to genotype individuals from 11 remnants, three contemporary nearby continuous native eucalypt forest sites and a sample collected during native vegetation clearance at the site in the 1960s. Patch samples retained substantially more genetic diversity than expected under an isolation model, suggesting that patches have experienced some immigration. Five putative patch immigrants--two from sampled sites 1- and 7-km distant, and three from unresolved or unsampled localities--were identified via genetic parentage and population assignment analyses. Patch populations displayed varying levels of admixture in Bayesian genetic structure analyses, with the oldest and most geographically isolated ones showing the least admixture, suggesting they have experienced relatively little immigration. Evidence of at least some immigration into patches may explain why P. volans has persisted contrary to expectation in heavily fragmented habitat.

Roadside connectivity does not increase reptile abundance or richness in a fragmented mallee landscape

“…Alternatively, some common reptiles may have been able to move through the agricultural matrix in numbers sufficient to maintain populations in farmland fragments, regardless of whether or not there was connection to roadside swales. The detailed spatial arrangement and corridor connections of remnants in the farmland may therefore be of less importance for reptile community composition than the total distance from the conservation park (Hoehn et al 2007;Taylor et al 2007). Direct connection of dunes to swale remnants in farmland did, however, increase species richness in the Hincks region, although it was not obvious what regional effects could have been responsible for this pattern.…”

Petauroides volans (Diprotodontia: Pseudocheiridae)

“…Divergence of Petauroides and Pseudocheirus occurred about 36 million years ago, and divergence of Petauroides and Hemibelideus about 18 million years ago (Springer et al 1992). Genetic analysis of metapopulation structure in fragmented landscapes has been used to examine the response of P. volans to disturbance (see Taylor et al 2002Taylor et al , 2007.…”

Genetic consequences of forest fragmentation by agricultural land in an arboreal marsupial

“…Although we did not find a direct relationship between the degree of patch isolation and the number of migrants in a patch, we did observe a correlation between patch isolation and genetic diversity, i.e., patches with greater minimum distances to their closest neighbour had lower allelic richness and heterozygosity than those with a nearby neighbour. A loss of genetic diversity resulting from forest fragmentation has also been observed in common hamsters, Cricetus cricetus, greater gliders, Petoroides volans, and bats, Dermanura watsoni (Taylor et al 2007;La Haye et al 2012;Ripperger et al 2013).…”

“…To this end, there have been a number of studies documenting the presence and abundance of native mammals in forests fragmented by pine plantations and agricultural land (e.g., Lindenmayer et al 1999Lindenmayer et al , 2000Wayne et al 2006;McAlpine et al 2006) and more recently, a focus on the genetic consequences of forest fragmentation using highly variable genetic markers (e.g., Banks et al 2005;Taylor et al 2007).…”