Historically low mitochondrial DNA diversity in koalas (Phascolarctos cinereus)

Kyriakos Tsangaras,Alfred L Roca,Yasuko Ishida,Alex D Greenwood,Kristofer M Helgen,María C Ávila-Arcos

doi:10.1186/1471-2156-13-92

Abstract

BackgroundThe koala (Phascolarctos cinereus) is an arboreal marsupial that was historically widespread across eastern Australia until the end of the 19th century when it suffered a steep population decline. Hunting for the fur trade, habitat conversion, and disease contributed to a precipitous reduction in koala population size during the late 1800s and early 1900s. To examine the effects of these reductions in population size on koala genetic diversity, we sequenced part of the hypervariable region of mitochondrial DNA (mtDNA) in koala museum specimens collected in the 19th and 20th centuries, hypothesizing that the historical samples would exhibit greater genetic diversity.ResultsThe mtDNA haplotypes present in historical museum samples were identical to haplotypes found in modern koala populations, and no novel haplotypes were detected. Rarefaction analyses suggested that the mtDNA genetic diversity present in the museum samples was similar to that of modern koalas.ConclusionsLow mtDNA diversity may have been present in koala populations prior to recent population declines. When considering management strategies, low genetic diversity of the mtDNA hypervariable region may not indicate recent inbreeding or founder events but may reflect an older historical pattern for koalas.

Highlights

The koala (Phascolarctos cinereus) is an arboreal marsupial that was historically widespread across eastern Australia until the end of the 19th century when it suffered a steep population decline
Sixteen of twentynine samples amplified for mitochondrial DNA (mtDNA); these ranged in year of collection from the late 1800s to the 1980s
Koalas appear to have been characterized by low mtDNA diversity for at least the last 120 years

Summary

Introduction

The koala (Phascolarctos cinereus) is an arboreal marsupial that was historically widespread across eastern Australia until the end of the 19th century when it suffered a steep population decline. Hunting for the fur trade, habitat conversion, and disease contributed to a precipitous reduction in koala population size during the late 1800s and early 1900s. The first live specimen was secured and brought to Sydney in 1803, and very few detailed accounts of the animal appeared in the decade that followed It was not until 1816, nearly three decades after the arrival of Britain’s First Fleet to Botany Bay, that the koala was studied in sufficient detail to be given its original scientific name, Lipurus cinereus [1]. By the 1930s, from the combined effects of hunting, habitat conversion, and disease, koala populations had been extirpated across much of southern Australia and were greatly diminished in the northern range of the species [2,3]

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