The changing nature of rock-wallaby (Petrogale) research 1980 - 2010

Abstract

Members of the endemicAustralianmacropodid genusPetrogale (rock-wallabies) have been of enduring scientific interest since the first species (brush-tailed rock-wallaby, Petrogale penicillata) was described in 1825 (Gray 1825). Although J. E. Gray initially placed penicillata in the genusKangurus (later Macropus), in 1837, recognising its many unique features, he made it the type species for a new genus Petrogale (Gray 1837). For the first 160 years the scientific investigation of rockwallabies was dominated by taxonomy and in this age of exploration at least 23 rock-wallaby species/subspecies were discovered anddescribed (Eldridge 1997a).However, taxonomic stability has been slow to emerge, with the number of recognised species oscillating between four and 11 for well over a century (Fig. 1). In fact, it is only in the last 10 years that the beginnings of a consensus has been established, with 16 species recognised (Fig. 1). This large number of species makes rock-wallabies one of themost successful groupsof extantmacropodids, representing 26% (16 of 61) of recent species (Eldridge 2010). Rock-wallabies are also of interest because, despite being relatively recently derived (Campeau-Peloquin et al. 2001; Meredith et al. 2008), they possess a unique suite of morphological, ecological and behavioural adaptations that have enabled them to colonise rocky habitat across mainlandAustralia (Eldridge 2008). They now inhabit a remarkable diversity of environments ranging from tropical to temperate and arid to mesic, but are not found in Tasmania (Eldridge 2008). Their naturally patchy distribution and seemingly highly mutable genomes (Eldridge and Johnston 1993) appear to have combined to produce an array of chromosomal diversity that is remarkable not just within marsupials but also amongst vertebrates (Eldridge and Metcalfe 2006). This diversity has made rock-wallabies an internationally recognised model for the study of chromosome evolution and speciation (Sharman et al. 1990; Eldridge and Close 1993; King 1995). They have also emerged as influential models in the study of population biology (Spencer et al. 1998; Eldridge et al. 2001a; Hazlitt et al. 2004; Delean et al. 2009), conservation biology (Eldridge et al. 1999) and wildlife management (Kinnear et al. 1988, 2002). Several rock-wallaby species have been the focus of longrunning conservation efforts (Lim et al. 1987; Eldridge et al. 2004; Kinnear et al. 2010). The three southern Australian species (brush-tailed, black-footed (P. lateralis) and yellow-footed (P. xanthopus) rock-wallabies) have all declined significantly in range and abundance in the last 150 years and are listed as ‘Vulnerable’ under the Federal Environment Protection and BiodiversityConservationAct 1999. Theonly other rock-wallaby species listed federally is the highly localised Proserpine rockwallaby (P. persephone) from central coastal Queensland, which is ‘Endangered’. Three other species (monjon (P. burbidgei), Cape York rock-wallaby (P. coenensis) and Sharman’s rockwallaby (P. sharmani)), all from northern Australia, are listed by the IUCN as ‘Near Threatened’, while the nabarlek (P. concinna) is regarded as ‘Data Deficient’ (IUCN 2010). For all these reasons, interest in and knowledge of rockwallaby continues to expand rapidly. An ISI Web of Knowledge (www.wokinfo.com) search on 25 June 2010 revealed 248 rock-wallaby papers: 15 published in the period 1965–79, 89 in 1980–95 and 144 in the last 15 years (1996–2010). In the last 30 years research output has been dominated (51%: Fig. 2) by just four species (brush-tailed, black-footed, yellow footed and allied (P. assimilis) rock-wallabies), most likely reflecting their accessibility and proximity to major urban centres (and therefore universities), as well as the three southern species being of long-standing conservation concern.While output on the three temperate-zone species has continued to increase (Fig. 2), 16