Comparative population genetic structure of the endangered southern brown bandicoot, Isoodon obesulus, in fragmented landscapes of Southern Australia

Genetic connectivity is a key factor for maintaining the persistence of populations in fragmented landscapes. In highly modified landscapes such us peri-urban areas, organisms' dispersal among fragmented habitat patches can be reduced due to the surrounding matrix, leading to subsequent decreased gene flow and increased potential extinction risk in isolated sub-populations. However, few studies have compared within species how dispersal/gene flow varies between regions and among different forms of matrix that might be encountered. In the current study, we investigated gene flow and dispersal in an endangered marsupial, the southern brown bandicoot (Isoodon obesulus) in a heavily modified peri-urban landscape in South Australia, Australia. We used 14 microsatellite markers to genotype 254 individuals which were sampled from 15 sites. Analyses revealed significant genetic structure. Our analyses also indicated that dispersal was mostly limited to neighbouring sites. Comparisons of these results with analyses of a different population of the same species revealed that gene flow/dispersal was more limited in this peri-urban landscape than in a pine plantation landscape approximately 400 km to the south-east. These findings increase our understanding of how the nature of fragmentation can lead to profound differences in levels of genetic connectivity among populations of the same species.You Li, Steven J.B. Cooper, Melanie L. Lancaster, Jasmin G. Packer, Susan M. Carthe

Invasive non-native plants retain native mammal communities in novel ecosystems.

Biological invasions are a major threat to native ecosystems globally, yet in some landscapes they can also have important positive effects on native biodiversity. For example, invasive non-native plants have the potential to act as ecological engineers in novel ecosystems by ‘creating’ habitat where it is otherwise lacking, thereby increasing the diversity and abundance of native fauna. Yet little is known of their net effect on population persistence. Understanding the impact of non-native plants on native fauna is becoming increasingly urgent for conservation management, particularly in degraded and novel ecosystems where the broad-scale removal of weeds could threaten native fauna populations and the ecological processes they contribute to. This thesis takes a local and global view to investigate the conservation conundrum of native fauna responses to non-native plants. It examines the effect of non-native blackberry on individual, population and community-level responses of small native mammals in native, hybrid and novel ecosystems before proposing a multi-scale framework to quantify the net effect of non-native plants on native fauna persistence. The research was undertaken in the Mount Lofty Ranges of South Australia, a biodiversity hotspot that is considered a ‘canary landscape’ for temperate woodlands. The environmental decline seen here is expected to follow similar trends elsewhere. Blackberry (Rubus anglocandicans) is a non-native and highly invasive environmental weed that has been reported to provide habitat for native birds and mammals in the study region. The research was conducted as a multi-species study of small mammal responses to blackberry, with a particular focus on the nationally endangered southern brown bandicoot (Isoodon obesulus). Small mammal communities were surveyed for 11 consecutive seasons across 13 sites (7,500 ha) that represented native, hybrid and blackberry-dominated novel ecosystems of the region. A mixed modelling approach was used to quantify the net effect of blackberry on fauna responses at multiple scales, including: individual (reproduction and physiology); population (abundance, adult female density, and recruitment); and community (species richness, diversity and interspecific competition). To the best of knowledge, this is the first study on the impact of non-native plants on the recruitment and population persistence of native mammals. Ten species of small mammals, including six native, were captured across 12,235 captures and 31,407 trap sessions. Blackberry was identified as an ecological engineer in blackberry-dominated novel ecosystems, where it retains diverse native mammal communities of yellow-footed antechinus (Antechinus flavipes; vulnerable), bush rat (Rattus fuscipes), brushtail possum (Trichosurus vulpecula; rare), short-beaked echidna (Tachyglossus aculeatus) and southern brown bandicoot (Isoodon obesulus; endangered). The abundance, density, dispersal and recruitment of bandicoots were also greatest in blackberry, with arthropod abundance and blackberry density the strongest positive predictors for recruitment of juveniles from source populations into the overall meta-population. The results confirm that non-native plants can act as ecosystem engineers in novel ecosystems and create critical habitat that supports mammal communities where they would otherwise become locally extinct. Interactions between non-native and native species are increasing worldwide, and quantifying these complex dynamics is essential in order to successfully tackle the conservation challenges of the future. The final chapter of the thesis responds to this challenge by critiquing the traditional and emerging methods used in the empirical study, and synthesizing these with existing frameworks on non-native – native interactions. The thesis concludes by proposing two conceptual frameworks to: (1) inform future quantitative assessments of native fauna responses to non-native plants, and (2) guide restoration to retain positive ecosystem processes while reducing those that are harmful. Thus the research contributes to native fauna conservation in fragmented landscapes via both primary data collection for multiple species at multiple scales, and by suggesting frameworks to improve the effectiveness of restoration by prioritizing actions where non-native plants provide habitat for native fauna in degraded ecosystems.Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 201

Pairwise <i>F</i>_<i>ST</i> values (below diagonal) and pairwise <i>D</i>_<i>EST</i> values (above diagonal) estimated for the 15 sites sampled for <i>I</i>. <i>obesulus</i> (following Sequential Bonferroni correction).

<p>Pairwise <i>F</i>_<i>ST</i> values (below diagonal) and pairwise <i>D</i>_<i>EST</i> values (above diagonal) estimated for the 15 sites sampled for <i>I</i>. <i>obesulus</i> (following Sequential Bonferroni correction).</p

Correlograms showing genetic correlation (r) as a function of distance (0.5 km distance classes).

<p>The 95% confidence intervals (dashed lines) were determined by 1 000 permutations. Error bars of each estimate of r bound the 95% confidence intervals were determined by 1 000 bootstraps. (a) Whole data set; (b) Males only (n = 140) and (c) Females only (n = 105).</p

Map of the location of three strongholds of <i>I</i>. <i>obesulus</i> in South Australia (SA), Australia (left hand side), with the box indicating the location of sites in the central Mount Lofty Ranges that were used in the current study.

<p>Cleared lands are represented in white and the borders of the national parks are represented in purple. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152850#pone.0152850.t001" target="_blank">Table 1</a> for full names of the sampled sites.</p

Results of migrants identified by STRUCTURE and GENECLASS analyses.

<p>Results of migrants identified by STRUCTURE and GENECLASS analyses.</p

Genetic structure of bandicoots from 15 sites.

<p>Proportional membership (<i>q</i>) of each bandicoot individual to a genetic cluster for the whole data set, identified by: (a) STRUCTURE, (b) TESS. Each vertical bar represents a bandicoot, and the length of each bar represents the probability of membership in each cluster (cluster 1 in yellow, cluster 2 in green, cluster 3 in red and cluster 4 in blue). Relevant parts of the STRUCTURE plot are also shown on the map for better visualisation of locality information.</p

Tall-statured grasses : a useful functional group for invasion science

Species in the grass family (Poaceae) have caused some of the most damaging invasions in natural ecosystems, but plants in this family are also among the most widely used by humans. Therefore, it is important to be able to predict their likelihood of naturalisation and impact. We explore whether plant height is of particular importance in determining naturalisation success and impact in Poaceae by comparing naturalisation of tallstatured grasses (TSGs; defined as grass species that maintain a self-supporting height of 2 m or greater) to non-TSGs using the Global Naturalised Alien Flora database. We review the competitive traits of TSGs and collate risk assessments conducted on TSGs. Of the c. 11,000 grass species globally, 929 qualify (c. 8.6%) as TSGs. 80.6% of TSGs are woody bamboos, with the remaining species scattered among 21 tribes in seven subfamilies. When all grass species were analysed, TSGs and non-TSGs did not differ significantly in the probability of naturalisation. However, when we analysed woody bamboos separately from the other grasses, the percentage of TSGs that have naturalised was 2–4 times greater than that of non-TSGs for both bamboos and non-bamboo groups. Our analyses suggest that woody bamboos should be analysed separately from other TSGs when considering naturalisation; within the C 2 mheight class they do not naturalise at the same rate as otherTSGs.Rapid growth rate and the capacity to accumulate biomass (a function of height) give many TSGs a competitive advantage and allow them to form monospecific stands, accumulate dense and deep litter mats, reduce light availability at ground level, and alter fire and nutrient-cycling regimes, thereby driving rapid ecosystemtransformation.While the height distribution in grasses is continuous (i.e. no obvious break is evident in heights), the 2 m designation for TSGs defines an important functional group in grasses that can improve predictive modelling for management and biosecurity.publishe

Moving Toward Global Strategies for Managing Invasive Alien Species

As human communities become increasingly interconnected through transport and trade, there has been a concomitant rise in both accidental and intentional species introductions, resulting in biological invasions. A warming global climate and the rapid movement of people and vessels across the globe have opened new air and sea routes, accelerated propagule pressure, and altered habitat disturbance regimes, all of which act synergistically to trigger and sustain invasions. The complexity and interconnectedness of biological invasions with commerce, culture, and human-mediated natural disturbances make prevention and management of invasive alien species (IAS) particularly challenging. Voluntary actions by single countries have proven to be insufficient in addressing biological invasions. Large gaps between science, management, and policy at various geopolitical scales still exist and necessitate an urgent need for more integrative approach across multiple scales and multiple stakeholder groups to bridge those gaps and reduce the impacts of biological invasions on biodiversity and human well-being. An evidence-based global strategy is therefore needed to predict, prevent, and manage the impacts of IAS. Here we define global strategies as frameworks for evidence-based visions, policy agreements, and commitments that address the patterns, mechanisms, and impact of biological invasions. Many existing global, regional, and thematic initiatives provide a strong foundation to inform a global IAS strategy. We propose five recommendations to progress these toward global strategies against biological invasions, including better standards and tools for long-term monitoring, techniques for evaluation of impacts across taxa and regions, modular regulatory frameworks that integrate incentives and compliance mechanisms with respect to diverse transcultural needs, biosecurity awareness and measures, and synergies with other conservation strategies. This proposed approach for IAS is inclusive, adaptive, and flexible and moves toward global strategies for better preventing and managing biological invasions. As existing research-policy-management networks mature and others emerge, the accelerating need for effective global strategies against biological invasions can finally be met

Tall-statured grasses: a useful functional group for invasion science

Species in the grass family (Poaceae) have caused some of the most damaging invasions in natural ecosystems, but plants in this family are also among the most widely used by humans. Therefore, it is important to be able to predict their likelihood of naturalisation and impact. We explore whether plant height is of particular importance in determining naturalisation success and impact in Poaceae by comparing naturalisation of tall-statured grasses (TSGs; defined as grass species that maintain a self-supporting height of 2 m or greater) to non-TSGs using the Global Naturalised Alien Flora database. We review the competitive traits of TSGs and collate risk assessments conducted on TSGs. Of the c. 11,000 grass species globally, 929 qualify (c. 8.6%) as TSGs. 80.6% of TSGs are woody bamboos, with the remaining species scattered among 21 tribes in seven subfamilies. When all grass species were analysed, TSGs and non-TSGs did not differ significantly in the probability of naturalisation. However, when we analysed woody bamboos separately from the other grasses, the percentage of TSGs that have naturalised was 2–4 times greater than that of non-TSGs for both bamboos and non-bamboo groups. Our analyses suggest that woody bamboos should be analysed separately from other TSGs when considering naturalisation; within the ≥ 2 m height class they do not naturalise at the same rate as other TSGs. Rapid growth rate and the capacity to accumulate biomass (a function of height) give many TSGs a competitive advantage and allow them to form monospecific stands, accumulate dense and deep litter mats, reduce light availability at ground level, and alter fire and nutrient-cycling regimes, thereby driving rapid ecosystem transformation. While the height distribution in grasses is continuous (i.e. no obvious break is evident in heights), the 2 m designation for TSGs defines an important functional group in grasses that can improve predictive modelling for management and biosecurity