Aim: We developed a new method to design objective, risk-based surveillance systems for non-indigenous species of invertebrates, vertebrates and plants, which might be introduced to a natural area ...through an industrial project; here, we provide the invertebrate case study. The method addresses issues common to complex surveillance design problems: a statistical standard (e.g. power); information gaps; multiple targets of unclear identity; a large surveillance area of heterogeneous risk of invasion; integrating multiple sources of surveillance data; optimizing for cost. Location: Barrow Island, Western Australia. Methods: We mapped the surveillance area for risk to target surveillance activities. An expert group identified a set of exemplar species and identified and characterized a set of detection methods for each, such that all potential invaders would be detected. We devised multi-element surveillance systems to detect each exemplar to the design power (0.8), then integrated them to a single system that was optimized for cost. Results: The surveillance system was deployed on the island to specification over 1 year, then reviewed for redesign in a second period. Main conclusions: The new method provided practical, risk-based surveillance system designs that met application requirements and overcame complex issues common to many surveillance applications. A review of experiences from surveillance in the first year led to practical improvements and design efficiencies.
Entomologist Jonathan Majer is a world pioneer in using ants as indicators of restoration success. With hundreds of published works to his name (and five species of ants named after him), he reflects ...in this interview on his undimming passion for learning and teaching about invertebrates – a group of animals that can include up to 95% of faunal species in a reference community.
Introduction
An assessment of whether rehabilitated mine sites have resulted in natural or novel ecosystems requires monitoring over considerable periods of time or the use of space-for-time ...substitution (chronosequence) approaches.
Methods
To provide an assessment of ecosystem recovery in areas mined for bauxite in 1975, the ant fauna of one area planted with
Eucalyptus resinifera
, one seeded with mixed native species, one topsoiled but unrestored, and a forest reference was subjected to a ‘long-term’ study by sampling monthly and latterly annually between 1976 and 1989 using pitfall traps. These plots were resampled in 2012. A companion ‘short-term’ chronosequence study was performed in 1979 in 28 bauxite mines of various ages and restored by a range of different methods, plus three forest references. In order to examine the assertion that the observed differences between restored areas and forest references will lessen with time, sampling using comparable methods was repeated in 2012 in seven of the original plots, representing progressive advances in rehabilitation technology: planted pines; planted eastern states eucalypts; planted native eucalypts; planted eucalypts over seeded understorey; and planted eucalypts on fresh, double-stripped topsoil, plus two forest reference sites.
Results
Ant and other invertebrate richness in the long-term study was initially superior in the seeded plot, with little difference between the planted and unplanted plots. It was concluded that although composition of the ant fauna had converged on that of the forest over the 14-year period, differences still persisted. The 2012 resampling revealed that ant species richness and composition had deteriorated in the seeded plot, while values in the unplanted plot, which now supported naturally colonised trees and an understorey, had increased. Differences between all rehabilitated plots and forest still persisted.
As with the long-term study, the rate of fauna return and the type of ants present in the short-term study plots differed with the method of rehabilitation used, and, in 1979, no plots had converged on the forest in terms of the ant assemblage. By 2012 ant richness increased, and more so with each advance in rehabilitation technology, except for seeding, in which the understorey had collapsed. Double-stripping of topsoil resulted in the greatest improvements in ant species richness, although none of the areas had converged on the forest reference areas in terms of assemblage composition or ant functional group profiles. Furthermore, assemblage composition in the forest had changed over time, possibly due to reductions in rainfall, which further complicates rehabilitation objectives.
Conclusions
It is concluded that although rehabilitation can achieve its objective of restoring diversity, the original assemblage has still not been achieved after 37 years, suggesting that a degree of novelty has been introduced into these older-style rehabilitated areas. The company’s current rehabilitation practices reflect multiple advances in their approach, lending optimism that current restoration may achieve something close to the original ecosystem, an outcome that can only be verified by extended studies like the one described here.
Like most ecosystems of the world, tropical dry forests of the central coast of the Gulf of Mexico are inadequately preserved. Given that reserve expansion is unlikely, it is imperative that the ...conservation capacity of the matrix surrounding reserves is enhanced. Here, we examine the habitat value of isolated pasture trees and patches of secondary regrowth in terms of their terrestrial and arboreal ant assemblages in both a wet and dry season. These simplified wooded systems increase species densities within the agricultural matrix and provide habitat for some forest ant species. Estimated species richness of arboreal ants was particularly low on isolated trees, highlighting an important limitation. This was not the case for terrestrial ants, which were particularly species rich under isolated trees. We also found that the inter-site variations in species densities and similarity to the forest ant assemblage for terrestrial and arboreal strata were not correlated, suggesting that responses to restoration may not be as uniform as often thought. This has important implications for the use of indicator taxa in suggesting the response of other taxa. In terms of species composition, neither secondary regrowth nor isolated trees were appropriate replacements for forest fragments, even though the studied forest fragments were small (13–32ha). The ant assemblages did not exhibit a seasonal change in composition. However, season influenced the contrast between habitats, with isolated trees being more distinct from pasture, and regrowth more closely resembling forests, during the wet season. Microclimatic variables indicate that the forests were least affected by the tropical dry season, and this may contribute to their characteristic fauna. We conclude that even small forest patches make a unique contribution to landscape conservation and that, where reserves are limited, conscientious management of the landscape matrix may provide some species with sufficient new habitat to survive outside of reserve systems. These conclusions are influenced by both season and strata studied.
Models of nature are implicitly influenced by the scale of observation of the processes on which they are founded. The continuum model and the hierarchical patch-based model are two alternate ...approaches for the spatial modelling of fauna distribution. The continuum model aggregates continuous approximations to individual landscape characteristics, whereas the hierarchical patch-based model constructs a hierarchy in which classifications of landscape characteristics describe an interconnected series of patches. We propose the hierarchical patch-based theory for models of population distributions and landscapes in which the spatial patterns can be effectively represented by mosaics at the variety of levels within the set of individual process models. Given that observations are typically made as points or pixels, and that discrete boundaries exist in both natural and human-modified landscapes, we suggest that the hierarchical patch-based method has many applications in conservation and management.
This study represents part of a broader investigation into novel seed broadcasting methodologies as a means to optimize rehabilitation techniques following sand mining. Specifically, the study ...investigated the use of polymer seed coatings, time of sowing application, and in situ raking of the topsoil to optimize seedling recruitment to site. For polymer seed coatings, an ex situ trial was undertaken to evaluate seed coating effects on seedling emergence. Results demonstrated that seed coatings did not significantly inhibit maximum emergence percentage of 10 Banksia woodland species (out of 11 evaluated), but coated seeds from four species were on average 2–6 days slower to emerge than noncoated seeds. Seed coatings were found to have a greater effect in situ, with more coated seeds emerging than noncoated seeds. Topsoil raking (following seed sowing) and time of sowing were found to have the greatest impact on seedling emergence, with higher emergence following topsoil raking (5‐ to 90‐fold increase) and sowing in May (late autumn) (1.4‐ to 12‐fold increase) rather than in July (mid‐winter). The implications for mining rehabilitation are discussed, and areas for further research are considered.
Models of nature are implicitly influenced by the scale of observation of the processes on which they are founded. The continuum model and the hierarchical patch-based model are two alternate ...approaches for the spatial modelling of fauna distribution. The continuum model aggregates continuous approximations to individual landscape characteristics, whereas the hierarchical patch- based model constructs a hierarchy in which classifications of landscape characteristics describe an interconnected series of patches. We propose the hierarchical patch-based theory for models of population distributions and landscapes in which the spatial patterns can be effectively represented by mosaics at the variety of levels within the set of individual process models. Given that observations are typically made as points or pixels, and that discrete boundaries exist in both natural and human-modified landscapes, we suggest that the hierarchical patch-based method has many applications in conservation and management.
We examine the relative importance of seed dispersal mode in determining the range size and range placement in 524 species from six focal plant families (Agavaceae, Euphorbiaceae, Malvacaeae, ...Sapindaceae, Proteaceae and Fabaceae (Acacia)). Western Australia. Taxa were categorized by dispersal mode and life-form and their distributions modelled using maxent. Geographical range size was compared amongst dispersal mode, life-form and biome using phylogenetically independent contrasts. Geographical range placement was considered in a similar manner. Range size did not vary with dispersal mode (ant versus wind and vertebrate dispersal) or life-form, and instead varied primarily as a function of the biogeographical region in which a species was found. Range placement, however, did vary among dispersal modes, with the consequence that diversity of wind- and ant-dispersed plants increased with latitude while the diversity of vertebrate-dispersed plants was more evenly distributed. For the taxa studied, range sizes were a function of the biogeographical region in which species were found. Although differences in range size may exist among species differing in dispersal modes, they are likely to be far smaller than differences among species from different biogeographical regions. The trait most likely to affect species geographical range size, and hence rarity and risks associated with other threats, may simply be the geographical region in which that species has evolved.
All known ant species from a small Western Australian island were subjected to DNA barcoding of the CO1 gene, with a view to using the database to identify ants by Next Generation Sequencing in ...subsequent, routine surveys. A further aim was to evaluate whether the data could be used to see if any new species had arrived on the island since the total fauna had been inventoried. Of the 125 unique ant species then known from the island, 72 were successfully barcoded. Those that were refractory to amplification were largely the result of sample age and/or contamination. Following this base-line barcoding, ants were sampled from 14 regular sampling sites and ant sequences were obtained from the bulked ‘metagenomic soup’. Prior to doing this, a parataxonomist had identified all ant species in the samples and returned them to the ‘soup’. Successful identification for each site varied from 38% (Sites 12 and 27) to 100% of species (Site 10). Comparison of the number of species recovered with the number of sequences obtained from each sample showed a positive correlation between the two variables. When a site had >1,000 sequences, the average recovery rate was 79%, which is in contrast to the lowest four recovery rates (Site samples 12, 22, 26 and 27), which had fewer than 440 amplicon sequences. The ability to detect individuals that occur at low frequencies is also important. We analysed each site individually to determine if a species was detected and how that related to the proportion of individuals in the pooled sample. Where a species was present at <4% of the total sample, it was only detected 10% of the time, indicating that adequate sequencing depth is critical to species recovery. We conclude that this technique was only partially successful in replacing conventional taxonomy and that it could have limited ability to detect incursions unless the new arrival is abundant. Current barcoding is no longer limited to the CO1 gene and other genes are characterised for identification of intractable groups where CO1 does not provide appropriate levels of resolution.
Isolated trees possess an arthropod assemblage different to that found in woodland trees. While isolated trees become an increasingly dominant part of many landscapes, with ‘off reserve’ habitat ...conservation potential, we know little about the drivers of their assemblage structure. While sampling bimonthly for 12 months in the seasonally dry tropics of Mexico, we characterized the ant species most likely to occupy isolated trees in comparison to small woody patches (‘matorral’; 0.13–0.74
ha), and examined the influence of environmental variables on the respective ant assemblages at both canopy and ground level. Isolated trees possessed a predictable ant assemblage: when compared to the woodland patches, isolated trees were characterised by a lack of specialised arboreal species and an increase in generalised terrestrial species reaching the canopy. Arboreal woodland ant species were as affected by tree isolation as the terrestrial woodland ant fauna. Ant assemblages at isolated trees correlated with a series of microenvironmental (microclimate and biophysical) variables, but this was not the case for the ant assemblages in woodlands. This suggests that at very small habitat sizes (e.g., isolated trees), microenvironment influences assemblage composition by favouring more environmentally tolerant or opportunistic species. Although we were unable to identify alternative variables (e.g., patch area, connectivity) which correlated with assemblage composition in larger habitat patches, it appears that in such patches, local microenvironment is less closely associated with assemblage structure, and variables such as patch and landscape configuration become increasingly important. In a practical sense, micro-habitat restoration aimed at augmentation of vegetation surrounding isolated trees may therefore be an effective means of increasing matrix habitat quality and increasing the partitioning of the arboreal and terrestrial faunas, thereby conserving a broader range of species. More generally, movement of matrix species into habitat patches appears to apply universally over a range of scales and taxa, and provides a distinct contrast to the predictions based on the Theory of Island Biogeography.
Isoliert stehende Bäume beherbergen eine Arthropodengemeinschaft, die sich von der auf Bäumen in Wäldern unterscheidet. Während isolierte Bäume ein zunehmend bedeutendes Element in vielen Landschaften mit Potential für den Nicht-Reservat-Habitatschutz haben, wissen wir wenig über die Steuerfaktoren für ihre Gemeinschaftsstruktur. Durch einjährige Sammeltätigkeit in den saisonalen trockenen Tropen von Mexiko charakterisierten wir die Ameisenarten, die mit größter Wahrscheinlichkeit isolierte Bäume verglichen mit kleinen Gehölzen (Matorral; 0.13–0.74
ha) besiedeln würden, und wir untersuchten den Einfluß von Umweltfaktoren auf die jeweilige Ameisengemeinschaft am Boden und in der Kronenschicht. Isolierte Bäume besaßen eine vorhersagbare Ameisengemeinschaft: Verglichen mit den Gehölzen waren isolierte Bäume durch das Fehlen spezialisierter Baumarten charakterisiert, sowie durch eine Zunahme von generalistischen Bodenarten in der Baumkrone. Die Baumameisen der Gehölze waren genauso von der Baumisolation betroffen wie die gehölztypischen Bodenameisen. Die Ameisengemeinschaften der isolierten Bäume waren mit einer Reihe von mikroklimatischen und biopysikalischen Faktoren korrelliert, nicht jedoch die Ameisengemeinschaften der Gehölze. Dies legt nahe, daß bei sehr geringen Habitatgrößen (z.B. isolierte Bäume) kleinräumige Umwelteinflüsse die Zusammensetzung der Gemeinschaft beeinflussen, indem umwelttolerante oder opportunistische Arten begünstigt werden. Obwohl es uns nicht gelang, alternative Faktoren (z.B. Gehölzfläche, Konnektivität) zu identifizieren, die mit der Gemeinschaftsstruktur in größeren Habitatflecken korrelliert gewesen wären, scheint es, daß in solchen Habitaten die kleinräumigen Umweltbedingungen weniger eng mit der Gemeinschaftsstruktur verknüpft sind und daß Faktoren wie Habitat- und Landschaftskonfiguration an Bedeutung gewinnen. In der Praxis könnte dies bedeuten, daß die Vermehrung der die isolierten Bäume umgebenden Vegetation ein probates Mittel sein könnte, die Qualität der Habitatmatrix zu erhöhen und den Anteil der arborealen und terrestrischen Faunenelemente zu steigern, wodurch ein breiteres Spektrum von Arten geschützt würde. Generell scheint das Eindringen von Matrixarten in Habitatflecken über ein breites Spektrum von Skalen und Arten verbreitet zu sein, und dies stellt einen klaren Widerspruch zu den Vorhersagen der Theorie der Inselbiogeographie dar.
PDF
