Does time since introduction influence enemy release of an invasive weed?

Release from natural enemies is considered to potentially play an important role in the initial establishment and success of introduced plants. With time, the species richness of herbivores using non-native plants may increase [species-time relationship (STR)]. We investigated whether enemy release may be limited to the early stages of invasion. Substituting space for time, we sampled invertebrates and measured leaf damage on the invasive species Senecio madagascariensis Poir. at multiple sites, north and south of the introduction site. Invertebrate communities were collected from plants in the field, and reared from collected plant tissue. We also sampled invertebrates and damage on the native congener Senecio pinnatifolius var. pinnatifolius A. Rich. This species served as a control to account for environmental factors that may vary along the latitudinal gradient and as a comparison for evaluating the enemy release hypothesis (ERH). In contrast to predictions of the ERH, greater damage and herbivore abundances and richness were found on the introduced species S. madagascariensis than on the native S. pinnatifolius. Supporting the STR, total invertebrates (including herbivores) decreased in abundance, richness and Shannon diversity from the point of introduction to the invasion fronts of S. madagascariensis. Leaf damage showed the opposite trend, with highest damage levels at the invasion fronts. Reared herbivore loads (as opposed to external collections) were greater on the invader at the point of introduction than on sites further from this region. These results suggest there is a complex relationship between the invader and invertebrate community response over time. S. madagascariensis may be undergoing rapid changes at its invasion fronts in response to environmental and herbivore pressure.

Antifungal activity in thrips soldiers suggests a dual role for this caste.

The social insect soldier is perhaps the most widely known caste, because it often exhibits spectacular weapons, such as highly enlarged jaws or reinforced appendages, which are used to defend the colony against enemies ranging in size from wasps to anteaters. We examined the function of the enlarged forelimbs of soldiers (both male and female) of the eusocial, gall-inhabiting insect Kladothrips intermedius, and discovered that they have little impact on their ability to repel the specialized invading thrips Koptothrips species. While the efficacy of the enlarged forelimb appears equivocal, we show that soldiers secrete strong antifungal compounds capable of controlling the specialized insect fungal pathogen, Cordyceps bassiana. Our data suggest that these thrips soldiers have evolved in response to selection by both macro- and micro-organisms. While it is unknown whether specialized fungal pathogens have been major selective agents in the evolution of the soldier caste in general, they were probably present when sociality first evolved and may have been the primordial enemies of social insects.

Conservation prioritization can resolve the flagship species conundrum.

Conservation strategies based on charismatic flagship species, such as tigers, lions, and elephants, successfully attract funding from individuals and corporate donors. However, critics of this species-focused approach argue it wastes resources and often does not benefit broader biodiversity. If true, then the best way of raising conservation funds excludes the best way of spending it. Here we show that this conundrum can be resolved, and that the flagship species approach does not impede cost-effective conservation. Through a tailored prioritization approach, we identify places containing flagship species while also maximizing global biodiversity representation (based on 19,616 terrestrial and freshwater species). We then compare these results to scenarios that only maximized biodiversity representation, and demonstrate that our flagship-based approach achieves 79-89% of our objective. This provides strong evidence that prudently selected flagships can both raise funds for conservation and help target where these resources are best spent to conserve biodiversity.

The cladistic basis for the phylogenetic diversity (PD) measure links evolutionary features to environmental gradients and supports broad applications of microbial ecology's "phylogenetic beta diversity" framework.

The PD measure of phylogenetic diversity interprets branch lengths cladistically to make inferences about feature diversity. PD calculations extend conventional species-level ecological indices to the features level. The "phylogenetic beta diversity" framework developed by microbial ecologists calculates PD-dissimilarities between community localities. Interpretation of these PD-dissimilarities at the feature level explains the framework's success in producing ordinations revealing environmental gradients. An example gradients space using PD-dissimilarities illustrates how evolutionary features form unimodal response patterns to gradients. This features model supports new application of existing species-level methods that are robust to unimodal responses, plus novel applications relating to climate change, commercial products discovery, and community assembly.

Measuring continuous compositional change using decline and decay in zeta diversity.

Incidence, or compositional, matrices are generated for a broad range of research applications in biology. Zeta diversity provides a common currency and conceptual framework that links incidence-based metrics with multiple patterns of interest in biology, ecology, and biodiversity science. It quantifies the variation in species (or OTU) composition of multiple assemblages (or cases) in space or time, to capture the contribution of the full suite of narrow, intermediate, and wide-ranging species to biotic heterogeneity. Here we provide a conceptual framework for the application and interpretation of patterns of continuous change in compositional diversity using zeta diversity. This includes consideration of the survey design context, and the multiple ways in which zeta diversity decline and decay can be used to examine and test turnover in the identity of elements across space and time. We introduce the zeta ratio-based retention rate curve to quantify rates of compositional change. We illustrate these applications using 11 empirical data sets from a broad range of taxa, scales, and levels of biological organization-from DNA molecules and microbes to communities and interaction networks-including one of the original data sets used to express compositional change and distance decay in ecology. We show (1) how different sample selection schemes used during the calculation of compositional change are appropriate for different data types and questions, (2) how higher orders of zeta may in some cases better detect shifts and transitions, and (3) the relative roles of rare vs. common species in driving patterns of compositional change. By exploring the application of zeta diversity decline and decay, including the retention rate, across this broad range of contexts, we demonstrate its application for understanding continuous turnover in biological systems.

Systematic conservation planning for groundwater ecosystems using phylogenetic diversity.

Aquifer ecosystems provide a range of important services including clean drinking water. These ecosystems, which are largely inaccessible to humans, comprise a distinct invertebrate fauna (stygofauna), which is characterized by narrow distributions, high levels of endemism and cryptic species. Although being under enormous anthropogenic pressure, aquifers have rarely been included in conservation planning because of the general lack of knowledge of species diversity and distribution. Here we use molecular sequence data and phylogenetic diversity as surrogates for stygofauna diversity in aquifers of New South Wales, Australia. We demonstrate how to incorporate these data as conservation features in the systematic conservation planning software Marxan. We designated each branch of the phylogenetic tree as a conservation feature, with the branch length as a surrogate for the number of distinct characters represented by each branch. Two molecular markers (nuclear 18S ribosomal DNA and mitochondrial cytochrome oxidase subunit I) were used to evaluate how marker variability and the resulting tree topology affected the site-selection process. We found that the sites containing the deepest phylogenetic branches were deemed the most irreplaceable by Marxan. By integrating phylogenetic data, we provide a method for including taxonomically undescribed groundwater fauna in systematic conservation planning.

Continental-scale assessment of risk to the Australian odonata from climate change.

Climate change is expected to have substantial impacts on the composition of freshwater communities, and many species are threatened by the loss of climatically suitable habitat. In this study we identify Australian Odonata (dragonflies and damselflies) vulnerable to the effects of climate change on the basis of exposure, sensitivity and pressure to disperse in the future. We used an ensemble of species distribution models to predict the distribution of 270 (85%) species of Australian Odonata, continent-wide at the subcatchment scale, and for both current and future climates using two emissions scenarios each for 2055 and 2085. Exposure was scored according to the departure of temperature, precipitation and hydrology from current conditions. Sensitivity accounted for change in the area and suitability of projected climatic habitat, and pressure to disperse combined measurements of average habitat shifts and the loss experienced with lower dispersal rates. Streams and rivers important to future conservation efforts were identified based on the sensitivity-weighted sum of habitat suitability for the most vulnerable species. The overall extent of suitable habitat declined for 56-69% of the species modelled by 2085 depending on emissions scenario. The proportion of species at risk across all components (exposure, sensitivity, pressure to disperse) varied between 7 and 17% from 2055 to 2085 and a further 3-17% of species were also projected to be at high risk due to declines that did not require range shifts. If dispersal to Tasmania was limited, many south-eastern species are at significantly increased risk. Conservation efforts will need to focus on creating and preserving freshwater refugia as part of a broader conservation strategy that improves connectivity and promotes adaptive range shifts. The significant predicted shifts in suitable habitat could potentially exceed the dispersal capacity of Odonata and highlights the challenge faced by other freshwater species.

The mean and variance of phylogenetic diversity under rarefaction.

Phylogenetic diversity (PD) depends on sampling depth, which complicates the comparison of PD between samples of different depth. One approach to dealing with differing sample depth for a given diversity statistic is to rarefy, which means to take a random subset of a given size of the original sample. Exact analytical formulae for the mean and variance of species richness under rarefaction have existed for some time but no such solution exists for PD.We have derived exact formulae for the mean and variance of PD under rarefaction. We confirm that these formulae are correct by comparing exact solution mean and variance to that calculated by repeated random (Monte Carlo) subsampling of a dataset of stem counts of woody shrubs of Toohey Forest, Queensland, Australia. We also demonstrate the application of the method using two examples: identifying hotspots of mammalian diversity in Australasian ecoregions, and characterising the human vaginal microbiome.There is a very high degree of correspondence between the analytical and random subsampling methods for calculating mean and variance of PD under rarefaction, although the Monte Carlo method requires a large number of random draws to converge on the exact solution for the variance.Rarefaction of mammalian PD of ecoregions in Australasia to a common standard of 25 species reveals very different rank orderings of ecoregions, indicating quite different hotspots of diversity than those obtained for unrarefied PD. The application of these methods to the vaginal microbiome shows that a classical score used to quantify bacterial vaginosis is correlated with the shape of the rarefaction curve.The analytical formulae for the mean and variance of PD under rarefaction are both exact and more efficient than repeated subsampling. Rarefaction of PD allows for many applications where comparisons of samples of different depth is required.

The use of invertebrates to detect small-scale habitat heterogeneity and its application to restoration practices.

Recent conceptual and technological solutions to biodiversity assessment allow large numbers of invertebrate specimens to be processed rapidly and provide researchers and practitioners with a unique tool for characterizing habitats. One application of these advances is the ability to detect and monitor small-scale habitat heterogeneity and so provide a measure of ecosystem restoration. This case study presents a test of the efficacy of using invertebrates to assess and monitor ecological restoration following bush regeneration. Eight contiguous habitat patches within a suburb of northern Sydney, Australia, were selected to represent areas that had undergone different bush regeneration techniques. A nearby and relatively undisturbed area of bushland was also sampled. A total of 57,806 ground-active invertebrate specimens from 35 different orders were collected in pitfall traps. 1,246 ant (Formicidae) specimens were further sorted into 46 ant morphospecies from 20 genera. Analyses of the three taxonomic data sets, including two different data transformations, demonstrated that: (i) invertebrate communities successfully characterized different sites, providing a high degree of differentiation among sites; (ii) ordinations of the sites allowed visual assessment of the impact of each management technique on the habitat relative to undisturbed habitats; and (iii) characterization of sites could be achieved using abundance classes or binary counts of ant morphospecies, representing potential cost and time savings. The project duration was a total of three person weeks and cost less than US$3,000 (1999 prices) to complete. Measurement of invertebrate assemblages will provide a tool for both rapid assessment of management decisions and a means by which to implement adaptive management and restoration.