The effects of defaunation on plants’ capacity to track climate change

Seed dispersal in decline Most plant species depend on animals to disperse their seeds, but this vital function is threatened by the declines in animal populations, limiting the potential for plants to adapt to climate change by shifting their ranges. Using data from more than 400 networks of seed dispersal interactions, Fricke et al . quantified the changes in seed disposal function brought about globally by defaunation. Their analyses indicate that past defaunation has severely reduced long-distance seed dispersal, cutting by more than half the number of seeds dispersed far enough to track climate change. In addition, their approach enables the prediction of seed dispersal interactions using species traits and an estimation of how these interactions translate into ecosystem functioning, thus informing ecological forecasting and the consequences of animal declines. —AMS

Short-lived species move uphill faster under climate change

Climate change is pushing species ranges and abundances towards the poles and mountain tops. Although many studies have documented local altitudinal shifts, knowledge of general patterns at a large spatial scale, such as a whole mountain range, is scarce. From a conservation perspective, studying altitudinal shifts in wildlife is relevant because mountain regions often represent biodiversity hotspots and are among the most vulnerable ecosystems. Here, we examine whether altitudinal shifts in birds’ abundances have occurred in the Scandinavian mountains over 13 years, and assess whether such shifts are related to species’ traits. Using abundance data, we show a clear pattern of uphill shift in the mean altitude of bird abundance across the Scandinavian mountains, with an average speed of 0.9 m per year. Out of 76 species, 7 shifted significantly their abundance uphill. Altitudinal shift was strongly related to species’ longevity: short-lived species showed more pronounced uphill shifts in abundance than long-lived species. The observed abundance shifts suggest that uphill shifts are not only driven by a small number of individuals at the range boundaries, but the overall bird abundances are on the move. Overall, the results underscore the wide-ranging impact of climate change and the potential vulnerability of species with slow life histories, as they appear less able to timely respond to rapidly changing climatic conditions.

effects of extensive grazing on the vegetation of a landscape-scale restoration site

The Wicken Fen Vision (Cambridgeshire, UK) is a landscape-scale habitat restoration project that uses process-driven, open-ended approaches to develop habitats on highly degraded and drained peat soils of former intensive arable land. The project land is extensively grazed with herds of free-roaming, minimally managed herds of Highland cattle and Konik horses. In one 119 ha area, seven 25m x 25 m grazing exclosures were erected and vascular plant species were recorded from 2007 to 2017. Plant species data were analysed to (1) compare changes in plant species composition and diversity in grazed and ungrazed areas; (2) use plant species traits and plant-environment associations to explore the nature of changes in plant composition; (3) use remote sensing to explore changes in vegetation structure; (4) examine the influence of land use histories on grazing outcomes in different parts of the site.There was a clear divergence through time between grazed and ungrazed areas, attributed to significantly greater canopy height, Ellenberg L (Light) and Ellenberg N (fertility) values within the exclosures. Species richness was significantly higher in grazed compared with ungrazed areas and species assemblages separated through the study period. After ten years, extensive free-roaming grazing has had significant impacts on vegetation structure and species richness but effects varied across the study site because of differing historical land use.

dynamAedes: a unified modelling framework for invasive Aedes mosquitoes

Mosquito species belonging to the genus Aedes have attracted the interest of scientists and public health officers for their invasive species traits and efficient capacity of transmitting viruses affecting humans. Some of these species were brought outside their native range by human activities such as trade and tourism, and colonised new regions thanks to a unique combination of eco-physiological traits. Considering mosquito physiological and behavioural traits to understand and predict the spatial and temporal population dynamics is thus a crucial step to develop strategies to mitigate the local densities of invasive Aedes populations. Here, we synthesised the life cycle of four invasive Aedes species (Ae. aegypti, Ae. albopictus, Ae. japonicus and Ae. koreicus) in a single multi-scale stochastic modelling framework which we coded in the R package dynamAedes. We designed a stage-based and time-discrete stochastic model driven by temperature, photo-period and inter-specific larval competition that can be applied to three different spatial scales: punctual, local and regional. These spatial scales consider different degrees of spatial complexity and data availability, by accounting for both active and passive dispersal of mosquito species as well as for the heterogeneity of the input temperature data. Our overarching aim was to provide a flexible, open-source and user-friendly tool rooted in the most updated knowledge on species biology which could be applied to the management of invasive Aedes populations as well as for more theoretical ecological inquiries.

Assessing the impact of fire on spider abundance through a global comparative analysis

Fire is an important ecological disturbance; however, in many regions fire regimes are changing due to anthropogenic factors. Understanding the responses of species and ecosystem to fire can help to develop predictive models and inform fire management decisions. Despite their massive diversity and abundance, relatively little is known about the impacts of fire on invertebrates. Spiders are a diverse and ubiquitous group, with variation in ecological, behavioural and life history traits, and can offer important insights into the impacts of fire on invertebrates and whether these depend on environmental factors, phylogenetic history, or species traits. We conducted phylogenetic comparative analyses of published data from studies investigating the impacts of fire on spiders. We investigated whether fire affects family level abundance and whether this effect depends on ecologically relevant traits or site-specific factors (vegetation, latitude, fire type, time since fire). We found that time since fire had a significant effect on the abundance of some spider families (Lycosidae, Linyphiidae, Agelenidae), and within forest vegetation types. There was no relationship between family level traits and response to fire, suggesting that a trait-based approach does not increase predictive power in this group at this taxonomic level. Overall, it is difficult to make broad generalisations about the impacts of fire on spider abundance due to variation in site- and fire-specific factors. We did, however, find evidence that short fire intervals may be a threat to some spider families, and in forest ecosystems, where abundance initially decreased after fire, which may have important implications for fire management strategies. Finally, we show that analyses of published data can be used to detect broad scale ecological patterns and provide an alternative to traditional meta-analytical approaches.

Ecological constraints and trait conservatism drive functional and phylogenetic structure of amphibians larvae assemblages in the Atlantic Forest

Investigate how ecological and/or evolutionary factors could affect the structure of ecological communities is a central demand in ecology. In order to better understand that we assessed phylogenetic and functional structure of 33 tadpole communities in the Atlantic Forest coastal plains of Southeastern Brazil. We tested the assumption that phylogenetic conservatism drive tadpole traits. We identified 32 communities with positive values of phylogenetic structure, with 18 of those being significantly clustered. Twelve of 33 communities showed aggregated functional structure. Trait diversity was skewed towards the root, indicating phylogenetic trait conservatism and evolutionary factors as important drivers of tadpoles community structure. Six out of 11 environmental variables were selected in the best explanatory model of phylogenetic structure. Water conductivity, external and internal diversity of vegetation structure, canopy cover, and dissolved oxygen were negatively related with phylogenetic clustering, whereas presence of potential fish predators was positively related. Four of those environmental variables and area were also included in the best explanatory model of functional structure. All variables represent factors related to performance, survivorship, and distribution of anuran communities. From the 12 functionally structured communities, 10 were also phylogenetically structured. Thus, environmental factors may be acting as filters, interacting with phylogenetically conserved species traits, and driving linage occurrence in tadpole communities. Our study provides evidence that phylogenetic and functional structure in vertebrates are a result of interacting ecological and evolutionary agents, resulting in structured anuran assemblages.

Good Things Come in Larger Packages: Size Matters for Adult Fruit-Feeding Butterfly Dispersal and Larval Diet Breadth

Introduction: In animals, body size is correlated with many aspects of natural history, such as life span, abundance, dispersal capacity and diet breadth. However, contrasting trends have been reported for the relationship between body size and these ecological traits. Methods: Fruit-feeding butterflies were used to investigate whether body size is correlated with species abundance, dispersal, permanence, and larval diet breadth in a Neotropical savanna in Brazil (Cerrado). We used Blomberg’s K and Phylogenetic Generalized Least Squares models (PGLS) to measure phylogenetic signal strength in species traits and to estimate size–dispersal–diet breadth associations, while also taking shared ancestry into account. Results: 539 individuals from 27 species were captured, and 190 individuals were recaptured, representing a 35% recapture rate. We found body size to be negatively associated with butterfly abundance, and positively associated with dispersal level, distance traveled, number of traps visited, individual permanence, and diet breadth. These results indicate that larger butterflies are more likely to disperse over longer distances. Moreover, larger butterflies have more generalized larval diets, based on the number of host plant families, genera, and phylogenetic diversity of the host plants they consume as larvae. Smaller butterflies rely on fewer resources, which is reflected in their higher survival in small patches and may explain their lower dispersal ability and higher diet specialization. Nevertheless, lower dispersal ability may, if not compensated by large population sizes, threaten small-bodied species inhabiting environments, such as the Cerrado, which have intense deforestation rates. Conclusions: Body size is positively associated with dispersal and diet breadth for the fruit-feeding butterflies collected in this study.

Species Traits Drive Long-Term Population Trends of Common Breeding Birds in Northern Italy

Long-term population trends are considerable sources of information to set wildlife conservation priorities and to evaluate the performance of management actions. In addition, trends observed in functional groups (e.g., trophic guilds) can provide the foundation to test specific hypotheses about the drivers of the observed population dynamics. The aims of this study were to assess population trends of breeding birds in Lombardy (N Italy) from 1992 to 2019 and to explore the relationships between trends and species sharing similar ecological and life history traits. Trends were quantified and tested for significance by weighted linear regression models and using yearly population indices (median and 95% confidence interval) predicted through generalized additive models. Results showed that 45% of the species increased, 24% decreased, and 31% showed non-significant trends. Life history traits analyses revealed a general decrease of migrants, of species with short incubation period and of species with high annual fecundity. Ecological traits analyses showed that plant-eaters and species feeding on invertebrates, farmland birds, and ground-nesters declined, while woodland birds increased. Further studies should focus on investigation of the relationship between long-term trends and species traits at large spatial scales, and on quantifying the effects of specific drivers across multiple functional groups.