Summary1. An important problem encountered by ecologists in species distribution modelling (SDM) and in multivariate analysis is that of understanding why environmental responses differ across species, and how differences are mediated by functional traits. 2. We describe a simple, generic approach to this problem -the core idea being to fit a predictive model for species abundance (or presence/absence) as a function of environmental variables, species traits and their interaction. 3. We show that this method can be understood as a model-based approach to the fourth-corner problem -the problem of studying the environment-trait association using matrices of abundance or presence/absence data across species, environmental data across sites and trait data across species. The matrix of environment-trait interaction coefficients is the fourth corner. 4. We illustrate that compared with existing approaches to the fourth-corner problem, the proposed model-based approach has advantages in interpretability and its capacity to perform model selection and make predictions. 5. To illustrate the method we used a generalized linear model with a LASSO penalty, fitted to data sets from four different studies requiring different models, illustrating the flexibility of the proposed approach. 6. Predictive performance of the model is compared with that of fitting SDMs separately to each species, and in each case, it is shown that the trait model, despite being much simpler, had comparable predictive performance, even significantly outperforming separate SDMs in some cases.
To understand how researchers are tackling globally important issues, it is crucial to identify whether current research is comprehensive enough to make substantive predictions about general responses. We examined how research on climate change affecting insects is being assessed, what factors are being tested and the localities of studies, from 1703 papers published between 1985 and August 2012. Most published research (64%) is generated from Europe and North America and being dedicated to core data analysis, with 29% of the studies analysed dedicated to Lepidoptera and 22% Diptera: which are well above their contribution to the currently identified insect species richness (estimated at 13% and 17% respectively). Research publications on Coleoptera fall well short of their proportional contribution (19% of publications but 39% of insect species identified), and to a lesser extent so do Hemiptera, and Hymenoptera. Species specific responses to changes in temperature by assessing distribution/range shifts or changes in abundance were the most commonly used methods of assessing the impact of climate change on insects. Research on insects and climate change to date is dominated by manuscripts assessing butterflies in Europe, insects of economic and/or environmental concern in forestry, agriculture, and model organisms. The research on understanding how insects will respond to a rapidly changing climate is still in its infancy, but the current trends of publications give a good basis for how we are attempting to assess insect responses. In particular, there is a crucial need for broader studies of ecological, behavioural, physiological and life history responses to be addressed across a greater range of geographic locations, particularly Asia, Africa and Australasia, and in areas of high human population growth and habitat modification. It is still too early in our understanding of taxa responses to climate change to know if charismatic taxa, such as butterflies, or disease vectors, including Diptera, can be used as keystone taxa to generalise other insect responses to climate change. This is critical as the basic biology of most species is still poorly known, and dominant, well studied taxa may show variable responses to climate change across their distribution due to regional biotic and abiotic influences. Indeed identifying if insect responses to climate change can be generalised using phylogeny, functional traits, or functional groups, or will populations and species exhibit idiosyncratic responses, should be a key priority for future research.
Species traits may provide a short-cut to predicting generalities in species turnover in response to environmental change, particularly for poorly known taxa. We ask if morphological traits of assemblages respond predictably to macrohabitats across a large scale. Ant assemblages were collected at nine paired pasture and remnant sites from within three areas along a 300 km distance. We measured ten functional morphological traits for replicate individuals of each species. We used a fourth corner model to test associations between microhabitat variables, macrohabitats (pastures and remnants) and traits. In addition, we tested the phylogenetic independence of traits, to determine if responses were likely to be due to filtering by morphology or phylogeny. Nine of ten traits were predicted by macrohabitat and the majority of these traits were independent of phylogeny. Surprisingly, microhabitat variables were not associated with morphological traits. Traits which were associated with macrohabitats were involved in locomotion, feeding behaviour and sensory ability. Ants in remnants had more maxillary palp segments, longer scapes and wider eyes, while having shorter femurs, smaller apical mandibular teeth and shorter Weber’s lengths. A clear relationship between traits and macrohabitats across a large scale suggests that species are filtered by coarse environmental differences. In contrast to the findings of previous studies, fine-scale filtering of morphological traits was not apparent. If such generalities in morphological trait responses to habitat hold across even larger scales, traits may prove critical in predicting the response of species assemblages to global change.
The redlegged earth mite, Halotydeus destructor (Tucker) (Acari: Penthaleidae), is an important pest of pastures, broad-acre crops, and vegetables across southern Australia. Populations of H. destructor in Western Australia have been known to be resistant to pyrethroid and organophosphorus pesticides since 2006 and 2014, respectively. Resistant populations are currently widespread across Western Australia’s southern growing region but have, until now, remained undetected in the large south-eastern Australian range of H. destructor, despite ongoing resistance screening since 2006. Following reports of a field control failure in the Upper South East district in South Australia in 2016, resistance testing determined this South Australian population was resistant to pyrethroid and organophosphorus pesticides. The levels of resistance discovered were similar to resistant H. destructor populations in Western Australia, which are associated with chemical control failures. This work confirms for the first-time that pesticide resistant populations of H. destructor are no longer isolated to Western Australia.
BACKGROUND: By modelling species-environment relationships of pest species, it is possible to understand potential limits to their distributions when they invade new regions, and their likely continued spread. The European earwig, Forficula auricularia, is a non-native invasive species in Australia that has been in the country for over 170 years. However, in the last few decades it has invaded new areas. Unlike in other countries, F. auricularia is a pest species of grains production in Australia. In this study we detail the Australian distribution of this species, adding new samples focussed around grain growing regions. Using this information we build global species distribution models for F. auricularia to better understand speciesenvironment relationships. RESULTS:Our models indicated that the distribution of F. auricularia is strongly associated with temperate through to semi-arid environments, a high winter rainfall and pronounced temperature seasonality. We identified regions that hold suitable, but as yet vacant, niche space for Australian populations, suggesting further potential for range expansion. Beyond climate, an 1 index describing human influence on the landscape was important to understand the distribution limits of this pest. We identified regions where there was suitable climate space, but which F. auricularia has not occupied likely due to low levels of human impact. CONCLUSION:Modelling the global distribution of a non-native pest species aided understanding of the regional distribution limits within Australia and highlighted the usefulness of human impact measures for modelling globally invasive insect species.
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