Genetic variation and structuring in the threatened koala populations of Southeast Queensland

Abstract

Habitat fragmentation can act to cause reproductive isolation between conspecifics and undermine species' persistence, though most studies have reported the genetic condition of populations that have already declined to a very small size. We examined genetic diversity within the vulnerable, declining koala (Phascolarctos cinereus) population in Southeast Queensland, Australia to determine the genetic impact of ongoing threatening processes. Five hundred and twelve koalas from ten Southeast Queensland Local Government Areas on the mainland and one island were genotyped at six polymorphic microsatellite loci. Based on Bayesian cluster analysis incorporating spatial data, the regional koala population was subdivided into six clusters, with location of major roads and rivers appearing to be consistent with being barriers to gene flow. The distribution of mtDNA control region haplotypes identified distinct coastal and inland clades suggesting that historically there was gene flow between koalas along the coast (though little interchange between coastal and inland animals). In contrast, koalas from the Koala Coast (Brisbane City, Logan City and Redland Shire) were shown by microsatellite analysis to be genetically distinct from adjacent areas. It is likely, therefore, that more recent reductions in population size and restricted gene flow through urbanisation have contributed to the genetic differentiation of koalas in the Koala Coast region.

Ecology and movement of urban koalas adjacent to linear infrastructure in coastal south-east Queensland

“…Recently, an important role has been suggested for disease in the decline of koala populations, with chlamydial infection being implicated as the primary cause of disease (Timms 2005;Markey et al 2007;Higgins 2008). Exacerbation of the disease may be attributed to the koala retrovirus (Tarlinton et al 2005) and stress from habitat clearing and other anthropogenic impacts (Weigler et al 1988;Lee et al 2010;Brearley et al 2013). In addition to these threats, urban koalas face increased mortality from dog attacks and vehicle collisions (Smith and Smith 1990;Melzer et al 2000;Stratford et al 2000;Dique et al 2003b;McAlpine et al 2006).…”

“…In south-east Queensland the urban and rural areas of Redland City, the southern section of Brisbane City, and eastern portion of Logan City form a region known as the 'Koala Coast' because it has historically supported a large koala population that is genetically distinct from other koala populations in south-east Queensland (Lee et al 2010). The Koala Coast is experiencing rapid human population growth and development (Queensland Government 2005), which has created concern for the long-term viability of the koala population.…”

Home range areas of koalas in an urban area of north-east New South Wales

“…Fencing may have limited application in Lismore where driveways occur at regular intervals. Furthermore, movement across roads is required to enable population processes to continue (Lee et al 2010). Current research has documented relatively little use of road underpasses and overpasses by koalas (see AMBS 2011), suggesting that further investigation of crossing structure design is needed.…”

MHC class II diversity of koala (Phascolarctos cinereus) populations across their range

“…Koala populations from Queensland and New South Wales (NSW) have also not experienced any systematic translocation and, relative to their southern counterparts, have high microsatellite diversity (Houlden et al, 1996). Although many northern populations are genetically distinct, as identified in south-east Queensland and north-east NSW (Lee et al, 2009(Lee et al, , 2012, this may be attributed to anthropogenic-related fragmentation and decline in many of these populations (Melzer et al, 2000;Gordon et al, 2006;Lunney et al, 2009). Northern populations were therefore listed as 'vulnerable' in early 2012 under the Australian federal Environment Protection and Biodiversity Conservation (EPBC) Act 1999.…”