Bruce L. Webber

Opinion: Is CRISPR-based gene drive a biocontrol silver bullet or global conservation threat?

Scientists have recognized the potential for applying gene drive technologies to the control of invasive species for several years (1, 2), yet debate about the application of gene drive has been primarily restricted to mosquitoes (3). Recent developments in clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 technology have restarted discussions of using gene drive for invasive species control (4).

A standardized set of metrics to assess and monitor tree invasions

Abstract Scientists, managers, and policy-makers need functional and effective metrics to improve our understanding and management of biological invasions. Such metrics would help to assess progress towards management goals, increase compatibility across administrative borders, and facilitate comparisons between invasions. Here we outline key characteristics of tree invasions (status, abundance, spatial extent, and impact), discuss how each of these characteristics changes with time, and examine potential metrics to describe and monitor them. We recommend quantifying tree invasions using six metrics: (a) current status in the region; (b) potential status; (c) the number of foci requiring management; (d) area of occupancy (AOO) (i.e. compressed canopy area or net infestation); (e) extent of occurrence (EOO) (i.e. range size or gross infestation); and (f) observations of current and potential impact. We discuss how each metric can be parameterised (e.g. we include a practical method for classifying the current stage of invasion for trees following Blackburn’s unified framework for biological invasions); their potential management value (e.g. EOO provides an indication of the area over which management is needed); and how they can be used in concert (e.g. combining AOO and EOO can provide insights into invasion dynamics; and we use potential status and threat together to develop a simple risk analysis tool). Based on these metrics, we propose a standardized template for reporting tree invasions that we hope will facilitate cross-species and inter-regional comparisons. While we feel this represents a valuable step towards standardized reporting, there is an urgent need to develop more consistent metrics for impact and threat, and for many specific purposes additional metrics are still needed (e.g. detectability is required to assess the feasibility of eradication).

Comment on “Climatic Niche Shifts Are Rare Among Terrestrial Plant Invaders”

Petitpierre et al. (Reports, 16 March 2012, p. 1344) conclude that niche shifts are rare for terrestrial plant invaders and that this justifies the use of correlative modeling to project species geographic ranges for biological invasions and climate change. We draw attention to the limitations of their conceptual assumptions and the importance of niche shifts excluded from their analyses.

Cassowary frugivory, seed defleshing and fruit fly infestation influence the transition from seed to seedling in the rare Australian rainforest tree, Ryparosa sp. nov. 1 (Achariaceae)

The rare Australian rainforest tree Ryparosa sp. nov. 1 aff. javanica (sensu Webber & Curtis, BW-017; Achariaceae) has large fleshy fruits that undergo a distinctive colour change during ripening. Fruit seem highly suited to frugivore interactions with large ground-dwelling avian or marsupial frugivores, a role primarily filled by the endangered cassowary. We found that fruits had chemical defence traits that closely paralleled morphological ripening signals. Young fruit seeds had amongst the highest concentrations of plant tissue cyanogens ever recorded (some in excess of 12 mg g-1 dw), yet the flesh of ripe fruits had negligible cyanogen defence. A seed treatment trial found that cassowary gut passage significantly improved germination from 4% to 92%, and we were not able to replicate this result with simulated treatments. While high levels of fruit fly larval infestation accounted for reduced seed viability, this predation was apparently reduced by cassowary gut passage. Post-germination seedling traits such as haustorial cryptocotylar cotyledons and epigeal germination may increase the chance of survival for establishing seedlings. We conclude that the range of traits seen in Ryparosa recruitment is particularly suited to interactions with frugivores and survival in a rainforest ecosystem.

Translocation or bust! A new acclimatization agenda for the 21st century?

There is little doubt that the species most at risk of extinction from rapid climate change are short-range endemics facing insurmountable dispersal barriers to potentially suitable alternative regions. Thomas [1] proposes that the only hope of avoiding extinction for these species is to undertake planned translocations. He argues that the benefits of translocation will outweigh the associated risks where translocations take place within the same broad geographic area and where the recipient areas lack local endemics [1].

Agricultural Weed Research: A Critique and Two Proposals

Abstract Two broad aims drive weed science research: improved management and improved understanding of weed biology and ecology. In recent years, agricultural weed research addressing these two aims has effectively split into separate subdisciplines despite repeated calls for greater integration. Although some excellent work is being done, agricultural weed research has developed a very high level of repetitiveness, a preponderance of purely descriptive studies, and has failed to clearly articulate novel hypotheses linked to established bodies of ecological and evolutionary theory. In contrast, invasive plant research attracts a diverse cadre of nonweed scientists using invasions to explore broader and more integrated biological questions grounded in theory. We propose that although studies focused on weed management remain vitally important, agricultural weed research would benefit from deeper theoretical justification, a broader vision, and increased collaboration across diverse disciplines. To initiate change in this direction, we call for more emphasis on interdisciplinary training for weed scientists, and for focused workshops and working groups to develop specific areas of research and promote interactions among weed scientists and with the wider scientific community.

Morphological analysis and a resolution of the Ryparosa javanica species complex (Achariaceae) from Malesian and Australian tropical rainforests

A study of morphological variation in Ryparosa javanica (Blume) Kurz ex Koord. & Valeton sensu lato (Achariaceae; Flacourtiaceae pro parte) was undertaken after distinct differences were observed between Australian and Bornean populations. The confusing taxonomic history of R. javanica is first summarised. Phenetic techniques of agglomerative classification and ordination were used to analyse herbarium and field-collected specimens. Distinct groupings based on vegetative characters were supported by reproductive traits, plant architecture, ant–plant associations and geographical discontinuities. This work demonstrates that the current circumscription of R. javanica is a complex of at least nine species: R. javanica sensu stricto now confined to Sumatra, Java and Bali; three species that warrant reinstatement: R. amplifolia (K.Sch.) Mildbr. from New Guinea, R. kurzii King from the Andaman and Nicobar Islands and R. wrayi King from southern Myanmar and Thailand, the Malay Peninsula and northern Sumatra; and five new species described as R. maculata B.L.Webber from eastern New Guinea, R. anterides B.L.Webber from eastern Borneo, R. milleri B.L.Webber from New Guinea, R. maycockii B.L.Webber from western Borneo and R. kurrangii B.L.Webber from northern Australia. A key to the species and commonly mistaken taxa is provided.

Logging increases the functional and phylogenetic dispersion of understorey plant communities in tropical lowland rain forest

Summary Logging is a major driver of tropical forest degradation, with severe impacts on plant richness and composition. Rarely have these effects been considered in terms of their impact on the functional and phylogenetic diversity of understorey plant communities, despite the direct relevance to community reassembly trajectories. Here, we test the effects of logging on functional traits and evolutionary relatedness, over and above effects that can be explained by changes in species richness alone. We hypothesised that strong environmental filtering will result in more clustered (under-dispersed) functional and phylogenetic structures within communities as logging intensity increases. We surveyed understorey plant communities at 180 locations across a logging intensity gradient from primary to repeatedly logged tropical lowland rain forest in Sabah, Malaysia. For the 691 recorded plant taxa, we generated a phylogeny to assess plot-level phylogenetic relatedness. We quantified 10 plant traits known to respond to disturbance and affect ecosystem functioning, and tested the influence of logging on functional and phylogenetic structure. We found no significant effect of forest canopy loss or road configuration on species richness. By contrast, both functional dispersion and phylogenetic dispersion (net relatedness index) showed strong gradients from clustered towards more randomly assembled communities at higher logging intensity, independent of variation in species richness. Moreover, there was a significant nonlinear shift in the trait dispersion relationship above a logging intensity threshold of c. 65% canopy loss (±17% CL). All functional traits showed significant phylogenetic signals, suggesting broad concordance between functional and phylogenetic dispersion, at least below the logging intensity threshold. Synthesis. We found a strong logging signal in the functional and phylogenetic structure of understorey plant communities, over and above species richness, but this effect was opposite to that predicted. Logging increased, rather than decreased, functional and phylogenetic dispersion in understorey plant communities. This effect was particularly pronounced for functional response traits, which directly link disturbance with plant community reassembly. Our study provides novel insights into the way logging affects understorey plant communities in tropical rain forest and highlights the importance of trait-based approaches to improve our understanding of the broad range of logging-associated impacts.

Leucopodoptera eumundii, a new genus and species of katydid from the tropical rainforests of North Queensland, Australia (Orthoptera: Tettigoniidae: Phaneropterinae: Holochlorini)

Abstract A new katydid from the tropical rainforests of northern Australia, Leucopodoptera eumundii gen. et sp. nov., is described. Morphological examination, scanning electron microscopy imaging and cytological preparations were used to establish defining characteristics. Principal taxonomic characters include the stridulatory file of the male and the ovipositor of the female. Laboratory and field-based observations give insight into the distribution, ecology and life-history of the species.

Human-mediated introduction of Livistona palms into central Australia: Conservation and management implications

Molecular phylogenies and their application to biogeographic questions, as illustrated by Kondo et al. [[1][1]] in their study of Livistona palms in Australia, are providing unprecedented insight into speciation and the historical movement of taxa around the world [[2][2]]. While such studies often