Michael D. Craig

Bushcricket spermatophores vary in accord with sperm competition and parental investment theory

Sperm competition theory predicts that males will vary the number of sperm ejaculated according to the intensity of competition expected over the fertilization of eggs. Parental investment theory predicts that the magnitude of male investment in offspring should be associated with confidence of paternity. The spermatophores of some bushcrickets serve the dual functions of delivering sperm and providing the female with a nutritious meal that appears to function as parental investment. We show how male Requena verticalis increase the number of sperm in the ampulla of the spermatophore and reduce the amount of spermatophylax material when mating with females with whom they have a low confidence of paternity. These changes in spermatophore morphology are in accord with theories of sperm competition and parental investment.

Advances in restoration ecology: rising to the challenges of the coming decades

Simultaneous environmental changes challenge biodiversity persistence and human wellbeing. The science and practice of restoration ecology, in collaboration with other disciplines, can contribute to overcoming these challenges. This endeavor requires a solid conceptual foundation based in empirical research which confronts, tests and influences theoretical developments. We review conceptual developments in restoration ecology over the last 30 years. We frame our review in the context of changing restoration goals which reflect increased societal awareness of the scale of environmental degradation and the recognition that inter-disciplinary approaches are needed to tackle environmental problems. Restoration ecology now encompasses facilitative interactions and network dynamics, trophic cascades, and above- and below ground linkages. It operates in a non-equilibrium, alternative states framework, at the landscape scale, and in response to changing environmental, economic and social conditions. Progress has been marked by conceptual advances in the fields of trait-environment relationships, community assembly, and understanding the links between biodiversity and ecosystem functioning. Conceptual and practical advances have been enhanced by applying evolving technologies, including treatments to increase seed germination and overcome recruitment bottlenecks, high throughput DNA sequencing to elucidate soil community structure and function, and advances in satellite technology and GPS tracking to monitor habitat use. The synthesis of these technologies with systematic reviews of context dependencies in restoration success, model based analyses and consideration of complex socio-ecological systems will allow generalizations to inform evidence based interventions. Ongoing challenges include setting realistic, socially acceptable goals for restoration under changing environmental conditions, and prioritizing actions in an increasingly space-competitive world. Ethical questions also surround the use of genetically modified material, translocations, taxon substitutions, and de-extinction, in restoration ecology. Addressing these issues, as the Ecological Society of America looks to its next century, will require current and future generations of researchers and practitioners, including economists, engineers, philosophers, landscape architects, social scientists and restoration ecologists, to work together with communities and governments to rise to the environmental challenges of the coming decades.

Contribution of genetics to ecological restoration

Ecological restoration of degraded ecosystems has emerged as a critical tool in the fight to reverse and ameliorate the current loss of biodiversity and ecosystem services. Approaches derived from different genetic disciplines are extending the theoretical and applied frameworks on which ecological restoration is based. We performed a search of scientific articles and identified 160 articles that employed a genetic approach within a restoration context to shed light on the links between genetics and restoration. These articles were then classified on whether they examined association between genetics and fitness or the application of genetics in demographic studies, and on the way the studies informed restoration practice. Although genetic research in restoration is rapidly growing, we found that studies could make better use of the extensive toolbox developed by applied fields in genetics. Overall, 41% of reviewed studies used genetic information to evaluate or monitor restoration, and 59% provided genetic information to guide prerestoration decision‐making processes. Reviewed studies suggest that restoration practitioners often overlook the importance of including genetic aspects within their restoration goals. Even though there is a genetic basis influencing the provision of ecosystem services, few studies explored this relationship. We provide a view of research gaps, future directions and challenges in the genetics of restoration.

Short-term logging and burning impacts on species richness, abundance and community structure of birds in open eucalypt forest in Western Australia

In 1985 new silvicultural prescriptions for managing jarrah (Eucalyptus marginata) forest in south-west Western Australia came into operation. The most extreme logging treatment (gap release) involved removal of most of the overstorey from patches no larger than 10 ha, followed by a regeneration fire. In the other logging treatment (shelterwood), less wood was removed from a larger area, also followed by a fire. This study examined the impact of these disturbances on the avifauna by monitoring species richness and abundance of birds one year before logging, one year before burning, and for five years after burning. Although 68 bird species were recorded during the seven years of the study, 29 of these were detected fewer than 15 times. Of the other 39 bird species recorded, only two (Gerygone fusca and Acanthiza apicalis) showed a statistically significant treatment effect over time on their abundance. The abundance of G. fusca initially declined in the disturbed treatments and by Year 7 of the study (5 years post-fire) in the gap-release treatment had not recovered its original abundance. A. apicalis increased its abundance in both shelterwood and gap-release treatments. By Year 7, both species in the logged treatments had abundances similar to those in the unlogged treatments. Total abundance of all species varied little across treatments. Species richness was highest by Year 7 in the shelterwood and lowest in the gap-release treatment. In some years community structure varied more at the external-reference sites (not recently logged or burnt) than at the gap-release sites. In particular, there was little overlap in community structure in the external-reference treatment between the first and final years, whereas the pre-logging and final year in the gap-release treatment showed a high degree of overlap. These differences are suggestive of overriding short-term annual variation in broad-scale factors rather than local factors. Yearly variation in rainfall and temperature was documented; during low rainfall periods, populations of foliage arthropods may have been reduced.

Does habitat structure influence capture probabilities? A study of reptiles in a eucalypt forest

Pitfall traps are commonly used to examine differences in reptile communities among habitat types and disturbance regimes that differ in structure. However, capture rates and probabilities may be influenced by habitat structure, which invalidates comparisons of relative abundance among habitat types. To assess whether pitfall traps provide accurate reflections of density and whether habitat structure affects capture probabilities, we trapped at six sites in various jarrah-forest habitat types in south-western Australia, then intensively searched 150-m2 total-removal plots around each pitfall grid to obtain absolute densities of reptiles. Pitfall captures were significantly correlated with numbers on total-removal plots for Hemiergis initialis and Lerista distinguenda, indicating that pitfall traps provided accurate reflections of density for these species. Capture probabilities of H. initialis and L. distinguenda and all reptiles combined showed no significant correlations with any structural variables, indicating that capture probabilities were consistent across sites. We conclude that trapping provided accurate estimates of relative abundance for some species and that capture probabilities were not influenced by vegetation structure. Because many studies use trapping to estimate abundances among habitat types, we encourage researchers to investigate how vegetation structure influences capture probabilities, so that general patterns can be determined; we also suggest improvements for any future studies.

Evaluation of the impact of time of day, weather, vegetation density and bird movements on outcomes of area searches for birds in eucalypt forests of south-western Australia

We assessed the influence of sampling biases on estimates of absolute density. Using area searches for birds on 1-ha plots, we showed that time of day, weather and vegetation density (logged v. unlogged forest) had no significant impact on the detection rates of birds. As a consequence these environmental variables did not affect estimates of total bird density or species richness. Amount of cloud cover was positively correlated with abundance of three species (white-browed scrubwren, inland thornbill and white-naped honeyeater) but negatively correlated with counts of the western gerygone. Radio-tracking of western yellow robins showed that about half of all birds present on a plot were detected during area searches. However, robins moved over an area twice as large as the plot searched. These errors compensate to give an accurate estimate of density for this species. Collectively, these results indicate that area searches give a reliable estimate of density in both logged and unlogged eucalypt forest.

Ecology of the western bearded dragon (Pogona minor) in unmined forest and forest restored after bauxite mining in south-west Western Australia

Forest areas restored after mining typically take decades, or longer, before they resemble the original vegetation community. Understanding how fauna succession varies with plant succession requires detailed knowledge of an animal’s ecology. Knowledge of an animal’s ecology can also be used to predict faunal responses to management manipulations and enable techniques to be developed that accelerate the return of fauna to restored sites. We radio-tracked western bearded dragons (Pogona minor) in a mix of unmined forest sites and sites restored after bauxite mining, in the jarrah forest of south-west Western Australia, to determine critical resources and important microhabitats for dragons. Dragons were generalists – utilising a range of microhabitats – and adaptable, adjusting their microhabitat use depending on availability. Individuals also differed significantly in their microhabitat use and did not appear to have a defined home range. We concluded that the species would rapidly recolonise restored sites and that no modifications to current restoration practices were required to accelerate their return. Prescribed burning of restored areas could negatively affect this species but the effect would be short-term (<2 years). The approach used in this study could be used to develop management prescriptions that accelerate the return of late-successional species to restored sites.

How many mature microhabitats does a slow-recolonising reptile require? Implications for restoration of bauxite minesites in south-western Australia

If we are to accelerate the recolonisation of restored areas by slow-recolonising species, we must provide suitable microhabitats at appropriate densities. Previous research in south-western Australia has shown that Napoleon’s skink (Egernia napoleonis) rarely recolonises restored areas. We trapped Napoleon’s skink in restoration and unmined forest to confirm the species was late successional. We also radio-tracked six skinks in unmined forest, to determine types and characteristics of used microhabitats, and estimated home ranges to determine required microhabitat densities, with the aim of accelerating skink recolonisation of restored areas. All tracked skinks used logs and hollow-bearing trees. Used logs were larger, and used trees were larger and taller than random samples, probably because large logs and trees were more likely to contain cracks and hollows that provide a refuge from predators. Extrapolations from home-range estimates indicated that a minimum of four logs ha–1 are required in restored areas to facilitate recolonisation by skinks, with skink densities likely to increase with log densities. Our study demonstrated that not all fauna will naturally recolonise restored areas and management of these areas is required to provide suitable habitat for late-successional species. Our approach could potentially be applied to other ecosystems or species.

The importance of grasstrees (Xanthorrhoea preissii) as habitat for mardo (Antechinus flavipes leucogaster) during post-fire recovery

Grasstrees (Xanthorrhoea) are an important structural component of many Australian ecosystems and also an important resource for many fauna species. Grasstrees have distinctive morphologies, with a crown of long thin leaves and skirts, the latter of which are accumulated dead leaves; both are incinerated by fire. This study determined the morphological features of Xanthorrhoea preissii, which change in response to fire from 6 months to 21 years post-burn. In addition, using radio-telemetry and spool-tracking, we determined that grasstrees are utilised as foraging and nesting resources for mardos (Antechinus flavipes leucogaster (Gray, 1841), Marsupialia: Dasyuridae). Recently burnt grasstrees (6 months post-burn) appeared not to be used by mardos at all. We found few mardos in these recently burnt sites, and the one individual we managed to track for 126 m utilised only a single grasstree: a 2-m-tall multiple-crowned grasstree that had escaped the fire was used as a nest site. For sites 5 years post-burn, mardos selectively utilised grasstrees with larger crown areas and those with a greater number of crowns compared with a random sample of available trees. At the 14-year post-burn sites, mardos still demonstrated some selection for grasstrees, although no specific single feature could be determined as most significant. We recorded humidity and temperature buffering effects in association with post-burn accumulation of grasstree skirt material and found that even dead grasstree ‘logs’ were an important resource for nests. We conclude that mardos utilise both live and dead grasstrees for foraging and nest sites, possibly owing to the availability of dense cover, a buffered microclimate, and potentially also food resources. Fire-management policies that promote habitat heterogeneity and retain several intact-skirted grasstrees within the landscape are likely to benefit mardos.

Movement patterns by Egernia napoleonis following reintroduction into restored jarrah forest

Context The value of animal reintroduction as a conservation tool is debated. This is largely because the limited quantity of research that has been conducted on animal reintroductions has shown varying degrees of success in establishing new populations. The reasons why some reintroductions are successful, whereas others are not, are often not clear. Aims The present research aims to determine whether reptile reintroduction into restored mine pits is a potential management technique for managing and conserving reptile populations within a mined landscape. Methods Twelve Napoleons skinks were trapped then fitted with 0.9-g transmitters. Half were reintroduced into 5-year-old restored mine pits and the other half into unmined forest. Bodyweights, movement patterns and macro-habitat selection were recorded weekly during November and then monthly until March. Key results Skinks reintroduced into restored sites quickly moved into unmined forest. Both groups of skinks moved large distances, but those reintroduced into restored sites travelled further than did control skinks and took longer to reduce their distances travelled, showing possible stress as a result of release into unsuitable habitat. Eventually, almost all skinks found suitable habitat in unmined forest and settled into these areas while continuing to gain weight. Conclusions Reintroduction was an ineffective technique for facilitating colonisation of restored minesites by Napoleons skink. Lack of suitable micro-habitats within restoration areas, such as ground logs and coarse, woody debris piles, is likely limiting the use of these areas by Napoleons skinks and is likely to be the cause of their failure to remain or settle in restored sites after reintroduction. Implications Determining the habitat requirements of skinks and replicating this in restoration sites would seem the more appropriate management option than is reintroduction, and this may be the case for other reptiles and habitat specialists.