Biology subjects

Moles, A. T.

Publications and source records attributed to Moles, A. T..

3 recordsLinked to original sources

bioRxiv2023

How strong is enemy release? A systematic compilation across taxa and approaches.

The enemy release hypothesis posits that introduced species escape some of their predators, pathogens and parasites when they move to a new range. We used a systematic review to compile data from 691 quantifications of enemy release spanning plants, animals and algae in aquatic and terrestrial systems worldwide. Data from 311 biogeographic contrasts (between home and new range) revealed that on average, a species experience only 30% as much enemy pressure in their introduced range as they experience in their native range. In contrast, data from 380 community contrasts (between native and introduced species) revealed that introduced species experience on average 57% of the enemy pressure that their native congeners endure. Interestingly, one third (36%) of contrasts showed higher, rather than lower, enemy pressure on the introduced population. Enemy release was consistently strong in contrasts of the diversity of enemies, intermediate in contrasts comparing enemy damage, and not significant in contrasts of host fitness, suggesting that while introduced populations are attacked by fewer enemies, this does not always result in higher fitness. We also found that enemy release was higher in molluscs and fish but lower in insects and algae, indicating that certain taxa may be favoured by enemy release. We hope that an improved understanding of the extent to which introduced species are released from enemy pressures will help managers to identify good opportunities for biocontrol, and to understand the factors likely to be affecting the success of invasive species.

ecology↗

bioRxiv2023

Does urbanization lead to parallel demographic shifts across the world in a cosmopolitan plant?

Urbanization is occurring globally, leading to dramatic environmental changes that are altering the ecology and evolution of species. In particular, the expansion of human infrastructure and the loss and fragmentation of natural habitats in cities is predicted to increase genetic drift and reduce gene flow by reducing the size and connectivity of populations. Alternatively, the "urban facilitation model" suggests that some species will have greater gene flow into and within cities leading to higher diversity and lower differentiation in urban populations. These alternative hypotheses have not been contrasted across multiple cities. Here, we used the genomic data from the Global Urban Evolution project (GLUE), to study the effects of urbanization on non-adaptive evolutionary processes of white clover (Trifolium repens) at a global scale. We found that white clover populations presented high genetic diversity and no evidence of a reduction in Ne linked to urbanization. On the contrary, we found that urban populations were less likely to experience a recent decrease in effective population size than rural ones. In addition, we found little genetic structure among populations both globally and between urban and rural populations, which showed extensive gene flow between habitats. Interestingly, white clover displayed overall higher gene flow within urban areas than within rural habitats. Our study provides one of the largest comprehensive tests of demographic effects of urbanization and our results contrast the common perception that heavily altered and fragmented urban environments will reduce the effective population size and genetic diversity of populations and contribute to their isolation.

evolutionary biology↗

bioRxiv2018

Untangling direct species associations from mediator species effects with graphical models

Ecologists often investigate co-occurrence patterns in multi-species data in order to gain insight into the ecological causes of observed co-occurrences. Apart from direct associations between two species, two species may co-occur because they both respond in similar ways to environmental variables, or due to the presence of other (mediator) species.\n\nA wide variety of methods are now available for modelling how environmental filtering drives species distributions. In contrast, methods for studying other causes of co-occurence are much more limited. \"Graphical\" methods, which can be used to study how mediator species impact co-occurrence patterns, have recently been proposed for use in ecology. However, available methods are limited to presence/absence data and methods assuming multivariate normality, which is problematic when analysing abundances.\n\nWe propose Gaussian copula graphical models (GCGMs) for studying the effect of mediator species on co-occurence patterns. GCGMs are a flexible type of graphical model which naturally accommodates all data types - binary (presence/absence), counts, as well as ordinal data and biomass, in a unified framework. Simulations for count data demonstrate that GCGMs are better able to distinguish effects of mediator species from direct associations than using existing methods designed for multivariate normal data.\n\nWe apply GCGMs to counts of hunting spiders, in order to visualise associations between species. We then analyze abundance data of New Zealand native forest cover (on an ordinal scale) to show how GCGMs can be used analyze large and complex datasets. In these data, we were able to reproduce known species relationships as well as generate new ecological hypotheses about species associations.

ecology↗