Biology subjects

Kass, J. M.

Publications and source records attributed to Kass, J. M..

8 recordsLinked to original sources

bioRxiv2026

Response diversity inconsistently predicts functional robustness to simulated zooplankton extinctions

1Ecosystem functioning can be maintained in species-rich communities even under fairly severe perturbations. This is because communities with high richness include variation both in species functional roles (functional diversity) and in their responses to environmental changes (response diversity). Response diversity has been proposed as a key mechanism underpinning the stabilising role of biodiversity in variable environments. However, less understood is the role of response diversity in stabilising communities against perturbations and thus preserving ecosystem function. Here, we employ community data from 76 reservoirs across the broad latitudinal gradient of the Japanese archipelago to show that zooplankton assemblages with higher variability in responses to environmental variables can retain functional diversity as species are removed, but that the result depends on the variable examined. We combine empirically derived occurrence data for 47 zooplankton species with biotic and abiotic variables in a joint species distribution model to derive species-specific environmental responses, then measure response diversity to environmental axes including fish community structure and water temperature. We also measure functional trait diversity of zooplankton assemblages and simulate sequential species extinctions, capturing the extinction thresholds beyond which half the functional diversity is lost. Finally, we combine these data streams to show that response diversity can predict higher functional robustness in zooplankton assemblages, but not consistently. The role of response diversity in predicting functional robustness was contingent on the specific metric and environmental variable considered. We found that a balance of positive and negative species responses to water temperature was a significant predictor of robustness, though other metrics and environmental variables mainly yielded non-significant relationships. Overall, we show that response diversity can confer stability to perturbations such as species extinctions, and we demonstrate the utility of species distribution models for measuring response diversity, overcoming mechanistic data limitations and expanding the toolkit available for studying response diversity in natural systems.

ecology↗

bioRxiv2026

Human land-use change drives co-occurrence of ecologically similar avian aerial insectivores in Southeast Asia

AimHuman land-use change contributes to biodiversity declines, but also creates new niches that facilitate novel biotic interactions. These interactions can reshape ecological communities and ecosystem function, yet remain poorly understood. Swiftlets and swallows in Southeast Asia present a classic example: coexistence is facilitated by fine-scale diet partitioning, with population sizes historically limited by available nesting substrates. However, several species now nest on manmade structures, particularly "nest farms" built to harvest edible swiftlet nests. We evaluated whether land-use change, especially the spread of nest farms, is leading to breakdowns in niche partitioning and increased competition among six sympatric swiftlets and swallows. LocationNorthern Borneo MethodsWe calculated geographic niche overlap using species distribution models (SDMs) with different environmental predictors, hypothesizing greater overlap when land-use variables were included. We then implemented joint species distribution models (JSDMs) to partition shared environmental responses from potential biotic interactions, predicting that competition would emerge as negative residual correlations. We used sightings from citizen-science datasets and structured surveys to evaluate the influence of climate, land-use, nest farms, morphology, and foraging behavior on species occurrences. ResultsSDMs that included land-use variables showed high niche overlap, suggesting that human activity homogenizes niches. The optimal JSDM, based on structured survey data, identified distance to nest farms as the strongest predictor of occurrence for all species, with species showing both positive and negative responses. Morphology and behavior had small effects, and residual correlations were weak, indicating limited unexplained biotic interactions. Main conclusionsHuman activity, through the creation of artificial nesting sites, broadly drives co-occurrence of swallows and swiftlets across our study region. These effects appear to operate primarily through environmental filtering rather than direct competition. Our findings reveal substantial and complex impacts of land-use change and anthropogenic nest sites on the distribution and composition of aerial insectivore communities.

ecology↗

bioRxiv2024

Environmental rather than spatial factors determine trait-based community structure: a case study with zooplankton

Ecological community structure, which has traditionally been described in terms of taxonomic units, is driven by a combination of dispersal and environmental filters. Traits have recently been recognized as alternative units for quantifying community parameters, but they may have important differences with taxonomic units. For example, as taxon-based community structures are determined by the identities of individual species, they may be more limited by species dispersal constraints, whereas trait-based community structures may be more regulated by environmental conditions because functional traits should have stronger linkages to habitat types rather than their specific locations. This suggests that the relative importance of dispersal and environmental filters may vary depending on the units employed to define community structure, yet how the contributions of these filters compare remains unclear. Zooplankton in lakes and reservoirs are an ideal system for examining the relative importance of these filters as they have moderate dispersal ability and inhabit communities in isolated habitats. In this study, we examined zooplankton assemblages in 87 artificial reservoirs throughout the Japanese archipelago to test the hypothesis that environmental filters play a more dominant role in determining trait-based community structures than taxon-based structures. To describe trait-based communities, we categorized zooplankton taxa into 12 functional groups using ecologically meaningful traits, including body size, feeding habits and mode, and population growth rate. We then examined the effects of both spatial configuration (reflecting dispersal filters) and environmental variables such as reservoir size and depth, trophic conditions, and fish assemblages for taxon- and trait-based community structures. Although variation in the taxon-based structure was explained equally well by spatial and environmental variables, variation in the trait-based structure explained by environmental variables was nearly twice that of spatial variables. These results support the idea that environmental filters play a more central role in determining trait-based community structures, and show that the relative importance of spatial and environmental filters changes with the way we define community structure. Open research statementAll the data used in this study was obtained from disclosed sources including the Database of Dams in Japan (http://mudam.nilim.go.jp/home) for the location and watershed areas; the Japan Dam Foundation (http://damnet.or.jp/) for the dam specification data; and the River Environmental Database (Red: http://www.nilim.go.jp/lab/fbg/ksnkankyo/index.html) for water chemistry, fish, and zooplankton. Data obtained from local reports of the national reservoir management office, Japan, can be provided by the authors upon request. All analyses were conducted in the R programming language and all functions used in the present study originate from existing packages.

ecology↗

bioRxiv2023

Breakdown in seasonal dynamics of ant communities with land-cover change

Concerns about widespread human-induced declines in insect populations are mounting, yet little is known about how land-use change modifies the dynamics of insect communities, particularly in understudied biomes. Here, we examine how the seasonal patterns of ant activity--key drivers of terrestrial ecosystem functioning--vary with human-induced land cover change on a subtropical island landscape. Using trap captures sampled biweekly from a biodiversity monitoring network covering Okinawa Island, Japan, we processed 1.2 million individuals and reconstructed activity patterns within and across habitat types. Forest communities exhibited greater variability than those in more developed areas. Using time-series decomposition to deconstruct this pattern, we found that ant communities at sites with greater human development exhibited diminished seasonality, reduced synchrony, and higher stochasticity compared to those at sites with greater forest cover. Our results cannot be explained by variation in either regional or in situ temperature patterns, or by differences in species richness or composition among sites. We conclude that the breakdown of natural seasonal patterns of functionally key insect communities may comprise an important and underappreciated consequence of global environmental change that must be better understood across Earths biomes.

ecology↗

bioRxiv2022

Incorporating sampling bias into permutation tests for niche and distribution models

Randomization tests are often used with species niche and distribution models to estimate model performance, test hypotheses, and measure methodological biases. Many of these tests involve building null models representing the hypothesis that there is no association between the species occurrences and the environmental predictors, then comparing the empirical model to null distributions built from these models. These null models are commonly based on points randomly selected with a uniform probability from the study area. However, spatial sampling bias, a near-universal feature of the occurrence data used to build niche and distribution models, results in a non-uniform probability of observing species in different areas even when species occurrences are unrelated to environmental predictors. Failing to account for this bias in randomization tests results in null distributions that do not accurately represent the null hypothesis, potentially leading to incorrect conclusions. In this study, we use simulations to demonstrate that uniform sampling in randomization tests can lead to unacceptable rates of type I error and poor estimates of methodological bias when spatial sampling bias is present in the occurrence data. We present a new method that incorporates a bias estimate into replicate simulations for these randomization tests, and show that this adjustment can reduce type I error rates to an acceptable level.

ecology↗

bioRxiv2022

New distribution data and phylogenetic approach reveal bioregionalization of the western Palearctic ants

AimBiogeographic regionalization has fascinated biogeographers and ecologists for centuries and is endued with new vitality by evolutionary perspectives. However, progress is scant for most insect groups due to shortfalls in distribution and phylogenetic information, namely Wallacean and Darwinian shortfalls respectively. Here, we used the western Palearctic ants as the case to tackle these shortfalls and test their biogeographic structure through novel distribution data and phylogenetic approaches. LocationWestern Palearctic realm. TaxonAnts (Formicidae). MethodsFirstly, we developed a refined database integrating the occurrences of 747 ant species across 207 regions of the western Palearctic realm, based on newly expert-validated records derived from the existing global ant biodiversity informatics. Using range estimates for these species derived from polygons and species distribution modelling, we produced species assemblages in 50 x 50 km grid cells. We calculated taxonomic and phylogenetic turnover of ant assemblages, performing hierarchical clustering analysis using the Simpson dissimilarity index to delineate biogeographic structure. ResultsAt both the regional list- and grid assemblage-levels, the Mediterranean has higher turnover and more biogeographic regions than northern Europe, both taxonomically and phylogenetically. Delineations based on grid assemblages detected more detailed biogeographic transitions, while those based on regional lists showed stronger insularity in biogeographic structure. The phylogenetic regionalization suggested closer but varied affinities between assemblages in comparison to the taxonomic approach. Main conclusionsHere, we integrated expert-validated regional lists, species distribution modelling, and a recent phylogeny to tackle Wallacean and Darwinian shortfalls for an important insect group by developing a next-generation map of biogeographic regionalization for the western Palearctic ants. The results of this study suggest strong constraints from geographic barriers and potential effects of climatic history on ant distributions and evolutionary history, and also provide baseline spatial information for future investigations of regional insect distributions.

zoology↗

bioRxiv2022

Global determinants of the distribution of insect genetic diversity

Understanding global patterns of genetic diversity (GD) is essential for describing, monitoring, and preserving life on Earth. To date, efforts to map macrogenetic patterns have been restricted to vertebrates, which comprise only a small fraction of Earths biodiversity. Here, we construct the first global map of predicted insect mitochondrial (COI) GD, derived from publicly available data. We calculate the mitochondrial GD mean (GDM) and evenness (GDE) of insect assemblages across the globe, identify their environmental correlates, and make predictions of mitochondrial GD levels in unsampled areas based on environmental data. Using the largest single-locus genetic dataset yet assembled, we find that mitochondrial GDE follows a quadratic latitudinal gradient peaking in the subtropics. Both mitochondrial GDM and GDE positively correlate with seasonally hot temperatures, as well as climate stability since the last glacial maximum. Our models explain 27.9% and 24.0% of the observed variation in mitochondrial GDM and GDE in insects, respectively, making an important step towards understanding global biodiversity patterns in the most diverse animal taxon.

evolutionary biology↗

bioRxiv2020

Ecological niche models as hypothesis generators of functional genetic differentiation and potential local adaptation in a Mediterranean alpine ecosystem

Geographically disparate populations within a species range may show important differences including variation in ecological, demographic, genetic and phenotypic characteristics. Based on the Center-Periphery Hypothesis, it is often assumed that environmental conditions are optimal in the geographic center of the range and stressful or suboptimal at the periphery, implying ecological marginality is concordant with geographic periphery. But this assumption has been challenged as geographical and ecological gradients are not necessarily concordant. The conservation value of populations inhabiting environmentally marginal areas is still under debate and is closely related with their evolutionary potential. Strong selective pressures caused by stressful conditions may generate novel adaptations in marginal areas, conferring these populations distinct evolutionary potential. But populations inhabiting marginal areas may also show reductions in neutral and adaptive genetic diversity via drift and inbreeding. In this work we explore the potential of ecological niche models (ENMs) to identify environmentally optimal and marginal areas, as well as the principal putative selective pressures likely to act. To do so, we built a carefully parameterized ENM of Silene ciliata, a dominant plant species of Mediterranean alpine habitats. Complementarily, we selected wild populations inhabiting contrasting environmental conditions and carried out common garden experiments to detect genetic differentiation among populations associated with functional traits. With the resulting information, we tested whether environmentally marginal populations defined by the ENM had genetically differentiated phenotypes that are potentially adaptive and, thus, of conservation value. We found genetically based phenotypic differentiation of phenological traits between populations inhabiting areas identified by the ENM as marginal and optimal, as well as between populations with different habitat suitability values. Results supported ENMs as powerful tools for determining environmental marginality and identifying selection pressures, and thus also as hypothesis generators for divergent selection. Furthermore, genetically based phenotypic differentiation found underlines the potential adaptive value of populations inhabiting marginal areas. The approach developed here provides a theoretically justified and practical way to study adaptive processes and provide insights about the conservation value of marginal populations.

evolutionary biology↗