Tracey Russell

Plant phylogeny as a surrogate for turnover in beetle assemblages

The ability to extrapolate from the known to the unknown is essential if we are to use the turnover of overall biodiversity, as opposed to a few well-known groups, to inform conservation planning. We investigated the usefulness of using evolutionary relationships of plants as a surrogate for the turnover of their associated beetle assemblages. If plant traits that are important to insects are phylogenetically conserved, it follows that there will be a positive relationship between insect faunal dissimilarity and plant evolutionary distance. We collected beetles using pyrethrum knock-down methods from 40 plant species belonging to four plant families in the Sydney region of Eastern Australia. We developed a novel approach for estimating variance in the dissimilarity of beetle assemblages, as explained by plant phylogeny, by using phylogenetic eigenvectors as explanatory variables in a distance-based redundancy analysis. We found a highly significant relationship between faunal dissimilarity and plant evolutionary distance for the entire beetle assemblage, the herbivorous component, and the non-herbivorous component, indicating that beetles generally showed some preference for particular plant clades as habitat, regardless of feeding guild. When comparing observed dissimilarities with those predicted from 40 jack-knife replicates of a Generalised Dissimilarity Model, we were often able to predict beetle turnover from plant phylogenetic relationships, although the reliability of this result was highly variable. Nevertheless, the broad response of beetle assemblages to plant evolutionary relatedness indicates real potential for plant phylogenetic pattern to act as a useful surrogate for insect biodiversity, especially when supplemented with other environmental correlates.

High possum mortality on urban roads: implications for the population viability of the common brushtail and the common ringtail possum

Animal–vehicle collisions impact wildlife populations and in the northern suburbs of Sydney, both the common brushtail possum (Trichosurus vulpecula) and the common ringtail possum (Pseudocheirus peregrinus) are killed in large numbers. Over a two-year period almost 600 road-killed possums were observed from 217 road surveys covering over 7800 km, equating to 5.45 possums per week over the 36-km study area. Surveys were conducted along roads where the environment ranged from low-rise suburban to continuous sclerophyll forest. Significantly more ringtail possums were observed as road-kill, outnumbering brushtail possums by almost three to one. No sex bias was found amongst road-killed ringtail possums; however, seasonal trends and weight fluctuations were significant, with both males and females being at their lowest weights during the autumn breeding season. For brushtail possums a bias towards young males was observed. Sex and weight of road-killed brushtail possums were comparable to live-trap data from a previous study in the same location. In areas of such high possum mortality, wildlife managers may need to take action to mitigate possum road-kill.

Age of road-killed common brushtail possums (Trichosurus vulpecula) and common ringtail possums (Pseudocheirus peregrinus) in an urban environment

Road-associated mortality has been identified as having major ecological effects on small, fragmented and declining populations. Both the common brushtail possum (Trichosurus vulpecula) and common ringtail possum (Pseudocheirus peregrinus) appear to be in decline in some regions across their natural ranges. Urban populations may be an exception; however, little is known of their population ecology. This study investigates age trends in a subset of road-killed brushtail and ringtail possums collected along eight northern Sydney roads between March 2004 and March 2006. From a total of 591 recorded road-killed possums, 86 were collected for use in this study (36 brushtails, 50 ringtails). Age was estimated using tooth wear patterns on cleaned skulls. Both species showed trends associated with age, and younger possums of both species were more likely to be killed on roads than older animals. Male-biased dispersal of subadult possums is considered a major contributing factor to the over-representation of young brushtail possums in this road-kill sample.

The incidence of road-killed possums in the Ku-ring-gai area of Sydney

Abstract. The spatial and temporal incidence of possum mortality on roads was monitored in Sydney’s northern suburbs over a two-year period. In total, 217 road surveys were completed, equating to over 17 000 km travelled. Almost 600 possums were observed as road-kill, with common ringtail possums (Pseudocheirus peregrinus) encountered in 87% of surveys and almost three times as often as common brushtail possums (Trichosurus vulpecula) (encountered in 52% of surveys). Roads were classified into three categories based on adjacent landscape attributes, with the road-side environment ranging from suburban housing to continuous sclerophyll forest. Clusters, or ‘hot spots’, for possum road-kill were identified using GIS. Most possum fatalities, and five out of six hot spots, occurred along roads at the bush–urban interface, suggesting high possum movement rates and/or abundance at these sites. Continuous canopy across the road was available along only 4% of the roads surveyed, forcing these arboreal marsupials to cross roads via electricity wires or at ground level, making them vulnerable to collision with vehicles. In an attempt to mitigate the possum road toll, two rope tunnel bridges were erected at canopy level above the most consistent hot spot. Subsequent monitoring of the roads was undertaken for 10 months after erection of the canopy bridge and road-kill numbers declined significantly at the site of the bridges, but also at adjacent sites throughout the study area.

Suburban attitudes towards the common brushtail possum Trichosurus vulpecula and the common ringtail possum Pseudocheirus peregrinus in the northern suburbs of Sydney

Community based urban wildlife surveys are a two way exchange of information. They allow the researcher to gain information on urban wildlife living, or travelling through, private property that would normally remain inaccessible, whilst simultaneously informing the participants of current research and conservation initiatives. In Sydneys northern suburbs, 600 residences were surveyed on their attitudes to urban possums, with a return rate of 33 %. The majority of respondents were accepting of these animals on their properties and showed an enthusiasm to learn more on living peaceably with possums. A minority were found to have a high level of conflict with these animals. The relatively high proportion of respondents who admitted to removing possums from their properties (20 % of respondents), shows the extent to which human - possum interactions reach a point where peaceable coexistence is no longer possible. Despite this, when informed of a conservation initiative in the area to mitigate possum road-ki...

Oncogenesis as a selective force: adaptive evolution in the face of a transmissible cancer

Similar to parasites, malignant cells exploit the host for energy, resources and protection, thereby impairing host health and fitness. Although cancer is widespread in the animal kingdom, its impact on life history traits and strategies have rarely been documented. Devil facial tumour disease (DFTD), a transmissible cancer, afflicting Tasmanian devils (Sarcophilus harrisii), provides an ideal model system to monitor the impact of cancer on host life-history, and to elucidate the evolutionary arms-race between malignant cells and their hosts. Here we provide an overview of parasite-induced host life history (LH) adaptations, then both phenotypic plasticity of LH responses and changes in allele frequencies that affect LH traits of Tasmanian devils in response to DFTD are discussed. We conclude that akin to parasites, cancer can directly and indirectly affect devil LH traits and trigger host evolutionary responses. Consequently, it is important to consider oncogenic processes as a selective force in wildlife.

Allocating sex in road-killed possums using PCR

Road-killed animals are a readily available but often overlooked source of specimens and data. Determining the sex of road-killed possums is often difficult due to the severe damage carcasses sustain on impact with vehicles. Consequently, valuable information is lost. To assess the potential application of genetic techniques to address this problem, tissue biopsies (n = 47) taken from road-killed possums were sexed via PCR, through the simultaneous use of W- (G6PD) and Y-linked (SRY) primers. Comparisons with animals of known sex were used to validate the accuracy of this method, with 100% (n = 19) of samples correctly identified in a blind test. This methodology can provide researchers with valuable, additional data for road-kill studies where assigning sex in the field is not possible.

Brushtail possums: do present law, policy and management approaches meet the needs of this species in all its contexts?

Abstract. Brushtail possums (Trichosurus vulpecula) have been variously described as endangered, pests, prized native wildlife and, recently, as a potential meat export. This article reports information on the increasing decline of the brushtail possum and on attitudes towards these animals. The ‘fit’ between values and attitudes and prevailing governance arrangements is assessed. While the range of this animal is certainly shrinking, areas do exist where the brushtail possum is present at high or very high densities. It is in these areas of high possum density (some urban areas and certain agricultural regions) that conflicts arise, both over the ‘identity’ of the brushtail possum and as to what would be appropriate management. It is argued that although brushtail possums enjoy significant legal protection, these provisions are treated as a nuisance to be circumvented by many residents in areas where possums are in high abundance. Existing policies on possum management somewhat unhelpfully focus attention on situations where possums are overabundant, thus overshadowing situations where active management of declining possum populations would be appropriate.

Genetic diversity, inbreeding and cancer

Genetic diversity is essential for adaptive capacities, providing organisms with the potential of successfully responding to intrinsic and extrinsic challenges. Although a clear reciprocal link between genetic diversity and resistance to parasites and pathogens has been established across taxa, the impact of loss of genetic diversity by inbreeding on the emergence and progression of non-communicable diseases, such as cancer, has been overlooked. Here we provide an overview of such associations and show that low genetic diversity and inbreeding associate with an increased risk of cancer in both humans and animals. Cancer being a multifaceted disease, loss of genetic diversity can directly (via accumulation of oncogenic homozygous mutations) and indirectly (via increased susceptibility to oncogenic pathogens) impact abnormal cell emergence and escape of immune surveillance. The observed link between reduced genetic diversity and cancer in wildlife may further imperil the long-term survival of numerous endangered species, highlighting the need to consider the impact of cancer in conservation biology. Finally, the somewhat incongruent data originating from human studies suggest that the association between genetic diversity and cancer development is multifactorial and may be tumour specific. Further studies are therefore crucial in order to elucidate the underpinnings of the interactions between genetic diversity, inbreeding and cancer.

MHC diversity and female age underpin reproductive success in an Australian icon; the Tasmanian devil

Devil Facial Tumour Disease (DFTD), a highly contagious cancer, has decimated Tasmanian devil (Sarcophilus harrisii) numbers in the wild. To ensure its long-term survival, a captive breeding program was implemented but has not been as successful as envisaged at its launch in 2005. We therefore investigated the reproductive success of 65 captive devil pair combinations, of which 35 produced offspring (successful pairs) whereas the remaining 30 pairs, despite being observed mating, produced no offspring (unsuccessful pairs). The devils were screened at six MHC Class I-linked microsatellite loci. Our analyses revealed that younger females had a higher probability of being successful than older females. In the successful pairs we also observed a higher difference in total number of heterozygous loci, i.e. when one devil had a high total number of heterozygous loci, its partner had low numbers. Our results therefore suggest that devil reproductive success is subject to disruptive MHC selection, which to our knowledge has never been recorded in any vertebrate. In order to enhance the success of the captive breeding program the results from the present study show the importance of using young (2-year old) females as well as subjecting the devils to MHC genotyping.