Matthew P. Hill

Niche overlap of congeneric invaders supports a single-species hypothesis and provides insight into future invasion risk: implications for global management of the Bactrocera dorsalis complex.

Background The invasive fruit fly, Bactrocera invadens, has expanded its range rapidly over the past 10 years. Here we aimed to determine if the recent range expansion of Bactrocera invadens into southern Africa can be better understood through niche exploration tools, ecological niche models (ENMs), and through incorporating information about Bactrocera dorsalis s.s., a putative conspecific species from Asia. We test for niche overlap of environmental variables between Bactrocera invadens and Bactrocera dorsalis s.s. as well as two other putative conspecific species, Bactrocera philippinensis and B. papayae. We examine overlap and similarity in the geographical expression of each species’ realised niche through reciprocal distribution models between Africa and Asia. We explore different geographical backgrounds, environmental variables and model complexity with multiple and single Bactrocera species hypotheses in an attempt to predict the recent range expansion of B. invadens into northern parts of South Africa. Principal Findings Bactrocera invadens has a high degree of niche overlap with B. dorsalis s.s. (and B. philippinensis and B. papayae). Ecological niche models built for Bactrocera dorsalis s.s. have high transferability to describe the range of B. invadens, and B. invadens is able to project to the core range of B. dorsalis s.s. The ENMs of both Bactrocera dorsalis and B. dorsalis combined with B. philipenesis and B. papayae have significantly higher predictive ability to capture the distribution points in South Africa than for B. invadens alone. Conclusions/Significance Consistent with other studies proposing these Bactrocera species as conspecific, niche similarity and overlap between these species is high. Considering these other Bactrocera dorsalis complex species simultaneously better describes the range expansion and invasion potential of B. invadens in South Africa. We suggest that these species should be considered the same–at least functionally–and global quarantine and management strategies applied equally to these Bactrocera species.

Functional responses can unify invasion ecology.

We contend that invasion ecology requires a universal, measurable trait of species and their interactions with resources that predicts key elements of invasibility and ecological impact; here, we advocate that functional responses can help achieve this across taxonomic and trophic groups, among habitats and contexts, and can hence help unify disparate research interests in invasion ecology.

Drivers, impacts, mechanisms and adaptation in insect invasions

Charles Darwin and other researchers in the nineteenth century made important contributions to the knowledge of invasive species. It is, however, only in the last half century, and especially over the last three decades, that researchers have attempted to collate theories and concepts to forge a predictive understanding of the processes that mediate invasiveness of introduced species, and invasibility of recipient ecosystems (Richardson 2011a). Invasion ecology has subsequently grown to becomeone of themost vibrant sub-disciplines of ecology. Biological aspects were the focus in early studies of biological invasions. More recently, as invasive species have become more widespread and their impacts on biodiversity, ecosystem functioning and human health have increased, more attention is being given to themany human dimensions of invasions and to ways of slowing or preventing new invasions and mitigating the negative effects of current invasions (Richardson 2011b). Although there are interesting and important invasive species from all taxonomic groups, certain groups have been studied more systematically than others, at least as reflected in the invasion literature (Pyšek et al. 2008). For example, plants have been disproportionally well studied, and many of the most prominent hypotheses and theories in invasion ecology were derived from studies of plants (Pyšek et al. 2006; Catford et al. 2009). Although many ‘‘poster child’’ examples of animal invasions have been well explored, the total number of detailed studies of invasive animals and the overall understanding of invasions in many animal groups has lagged behind that of plants. This is also true for insects; although they are the most diverse class of animals, invasive insect species are underrepresented in the literature on such aspects as the ecological impacts of invasions (Kenis et al. 2009). In tracing the history of study of invasive insects, it is not surprising that much of the early work focussed on species of agricultural and economic importance (Pyšek et al. 2008; Kenis et al. 2009; Sutherst 2014). Many invasive pest species of insects have thus received considerable research attention, although not always in the context of what is now considered ‘‘invasion science’’. The Hessian fly,Mayetiola destructor, a pest of cereal crops, provides a clear example of how components of what is now known as invasion science came together in ca. 1780, long before the formalisation of the discipline of ecology. Pauly (2002) describes how Guest editors: Matthew P. Hill, Susana Clusella-Trullas, John S. Terblanche & David M. Richardson / Insect Invasions

Distribution of cryptic blue oat mite species in Australia: current and future climate conditions

1 Invertebrate pests, such as blue oat mites Penthaleus spp., cause significant economic damage to agricultural crops in Australia. Climate is a major driver of invertebrate species distributions and climate change is expected to shift pest assemblages and pest prevalence across Australia. At this stage, little is known of how individual species will respond to climate change. 2 We have mapped the current distribution for each of the three pest Penthaleus spp. in Australia and built ecological niche models for each species using the correlative modelling software, maxent. Predictor variables useful for describing the climate space of each species were determined and the models were projected into a range of future climate change scenarios to assess how climate change may alter species‐specific distribution patterns in Australia. 3 The distributions of the three cryptic Penthaleus spp. are best described with different sets of climatic variables. Suitable climate space for all species decreases under the climate change scenarios investigated in the present study. The models also indicate that the assemblage of Penthaleus spp. is likely to change across Australia, particularly in Western Australia, South Australia and Victoria. 4 These results show the distributions of the three Penthaleus spp. are correlated with different climatic variables, and that regional control of mite pests is likely to change in the future. A further understanding of ecological and physiological processes that may influence the distribution and pest status of mites is required.

Drosophila as models to understand the adaptive process during invasion

The last few decades have seen a growing number of species invasions globally, including many insect species. In drosophilids, there are several examples of successful invasions, i.e. Zaprionus indianus and Drosophila subobscura some decades ago, but the most recent and prominent example is the invasion of Europe and North America by the pest species, Drosophila suzukii. During the invasive process, species often encounter diverse environmental conditions that they must respond to, either through rapid genetic adaptive shifts or phenotypic plasticity, or by some combination of both. Consequently, invasive species constitute powerful models for investigating various questions related to the adaptive processes that underpin successful invasions. In this paper, we highlight how Drosophila have been and remain a valuable model group for understanding these underlying adaptive processes, and how they enable insight into key questions in invasion biology, including how quickly adaptive responses can occur when species are faced with new environmental conditions.

Divergent thermal specialisation of two South African entomopathogenic nematodes.

Thermal physiology of entomopathogenic nematodes (EPN) is a critical aspect of field performance and fitness. Thermal limits for survival and activity, and the ability of these limits to adjust (i.e., show phenotypic flexibility) depending on recent thermal history, are generally poorly established, especially for non-model nematode species. Here we report the acute thermal limits for survival, and the thermal acclimation-related plasticity thereof for two key endemic South African EPN species, Steinernema yirgalemense and Heterorhabditis zealandica. Results including LT50 indicate S. yirgalemense (LT50 = 40.8 ± 0.3 °C) has greater high temperature tolerance than H. zealandica (LT50 = 36.7 ± 0.2 °C), but S. yirgalemense (LT50 = −2.4 ± 0 °C) has poorer low temperature tolerance in comparison to H. zealandica (LT50 = −9.7 ± 0.3 °C), suggesting these two EPN species occupy divergent thermal niches to one another. Acclimation had both negative and positive effects on temperature stress survival of both species, although the overall variation meant that many of these effects were non-significant. There was no indication of a consistent loss of plasticity with improved basal thermal tolerance for either species at upper lethal temperatures. At lower temperatures measured for H. zealandica, the 5 °C acclimation lowered survival until below −12.5 °C, where after it increased survival. Such results indicate that the thermal niche breadth of EPN species can differ significantly depending on recent thermal conditions, and should be characterized across a broad range of species to understand the evolution of thermal limits to performance and survival in this group.

A simple route to full structural analysis of biophosphates and their application to materials discovery.

An integrated suite of synthesis and characterisation techniques that includes synchrotron-based single crystal, powder X-ray diffraction, nuclear magnetic resonance and electron diffraction have been employed to uncover two new distinct structures in the Ca(x)Ba(2-x)P(2)O(7) polymorphic phosphate system. These materials have particular relevance for their application as both biomaterials and phosphors. Calcium barium pyrophosphate, CaBaP(2)O(7), was shown by a combination of spectroscopic and diffraction techniques to have two polymorphs distinct in structure from all of the five previously reported polymorphs of Ca, Sr and Ba pyrophosphate. A high temperature polymorph HT-CaBaP(2)O(7) prepared at 1200 °C is orthorhombic, of space group P(212121) with a = 13.0494 Å, b = 8.9677 Å, c = 5.5444 Å. A low temperature polymorph LT-CaBaP(2)O(7), prepared below 1000 °C, is monoclinic with space group P2(1)/c and dimensions a = 12.065 Å, b = 10.582 Å, c = 9.515 Å, β = 94.609°.

Fictional responses from Vonesh et al.

Vonesh et al. (2017) in their critique of Dick et al. (2017) erect a straw man with their thought experiment; they look for reasons why comparative functional response (CFR) might fail, when CFR clearly and repeatedly succeeds.