Biology subjects

Dahirel, M.

Publications and source records attributed to Dahirel, M..

5 recordsLinked to original sources

bioRxiv2018

Dispersers are more likely to follow mucus trails in the land snail Cornu aspersum

Dispersal, i.e. movement leading to gene flow, is a fundamental although costly life history trait. The use of indirect social information may help mitigate these costs, yet in many cases little is known about the proximate sources of such information, and how dispersers and residents may differ in their information use. Land gastropods, which have a high cost of movement and obligatorily leave information potentially exploitable by conspecifics during movement (through mucus trails), are a good model to investigate links between dispersal costs and information use. We used Y-mazes to see whether dispersers and residents differed in their trail-following propensity, in the snail Cornu aspersum. Dispersers followed mucus trails more frequently than expected by chance, contrary to non-dispersers. Ignoring dispersal status during tests would lead to falsely conclude to no trail-following for the majority of ecologically realistic scenarios. Trail following by dispersers may reduce dispersal costs by reducing energy expenditure and helping snails find existing patches. Finally, we point that ignoring the potential for collective dispersal provided by trail-following abilities may lead to wrong inferences on the demographic and genetic consequences of dispersal.

ecology↗

bioRxiv2017

Cobwebbing in the city: urbanization-driven shifts in body-size dependent behaviours are decoupled from body size in an orb-web spider

O_LIIn animals, behavioural responses may play an important role in determining population persistence in the face of environmental changes. Body size is a key trait central to many life history traits and behaviours. While behaviours are typically assumed to be highly plastic, size correlations may impose constraints on their adaptive value when size itself is subject to environmental changes.\nC_LIO_LIUrbanization is an important human-induced rapid environmental change that imposes multiple selection pressures on both body size and (size-constrained) behaviour. How these combine to shape behavioural responses of urban-dwelling species is unclear.\nC_LIO_LIUsing web-building, an easily quantifiable behaviour linked to body size, and the garden spider Araneus diadematus as a model, we disentangle direct behavioural responses to urbanization and body size constraints across a network of 63 selected populations differing in urbanization intensity at two spatial scales.\nC_LIO_LISpiders were smaller in highly urbanized sites (local scale only), in line with expectations based on reduced prey biomass availability and the Urban Heat Island effect. The use of multivariate mixed modelling reveals that although web traits and body size are correlated within populations, behavioural responses to urbanization do not appear to be constrained by size: there is no evidence of size-web correlations among populations or among landscapes. Spiders thus altered different components of their web-building behaviours independently in response to urbanization: mesh width and web surface decreased independently with urbanization at the local scale, while web surface also increased with urbanization at the landscape scale. These responses are expected to compensate, at least in part, for reduced prey biomass availability.\nC_LIO_LIOur results demonstrate that responses in typically size-dependent behaviours may be decoupled from size changes, thereby allowing fitness maximisation in novel environments. The spatial scale of the behavioural responses to urbanization suggest contributions of both genetic adaptation and plasticity. Although fecundity decreased with local-scale urbanization, Araneus diadematus abundances were remarkably similar across urbanization gradients; behavioural responses thus appear overall successful at the population level.\nC_LI

ecology↗

bioRxiv2017

Bottom-up and top-down control of dispersal across major organismal groups: a coordinated distributed experiment

Organisms rarely experience a homogeneous environment. Rather, ecological and evolutionary dynamics unfold in spatially structured and fragmented landscapes, with dispersal as the central process linking these dynamics across spatial scales. Because dispersal is a multi-causal and highly plastic life-history trait, finding general drivers that are of importance across species is challenging but highly relevant for ecological forecasting.\n\nWe here tested whether two fundamental ecological forces and main determinants of local population dynamics, top-down and bottom-up control, generally explain dispersal in spatially structured communities. In a coordinated distributed experiment spanning a wide range of actively dispersing organisms, from protozoa to vertebrates, we show that bottom-up control, that is resource limitation, consistently increased dispersal. While top-down control, that is predation risk, was an equally important dispersal driver as bottom-up control, its effect depended on prey and predator space use and whether dispersal occurred on land, in water or in the air: species that routinely use more space than their predators showed increased dispersal in response to predation, specifically in aquatic environments. After establishing these general causes of dispersal, we used a metacommunity model to show that bottom-up and top-down control of dispersal has important consequences for local population fluctuations as well as cascading effects on regional metacommunity dynamics. Context-dependent dispersal reduced local population fluctuations and desynchronized dynamics between communities, two effects that increase population and community stability.\n\nOur study provides unprecedented insights into the generality of the positive resource dependency of dispersal as well as a robust experimental test of current theory predicting that predator-induced dispersal is modulated by prey and predator space use. Our experimental and theoretical work highlights the critical importance of the multi-causal nature of dispersal as well as its cascading effects on regional community dynamics, which are specifically relevant to ecological forecasting.

ecology↗

bioRxiv2017

Kin competition as driver of range expansions

With ongoing global change, life is continuously forced to move to novel areas, which leads to dynamically changing species ranges. As dispersal is central to range dynamics, factors promoting fast and distant dispersal are key to understanding and predicting species ranges. During range expansions, genetic variation is depleted at the expanding front. Such conditions should reduce evolutionary potential, while increasing kin competition. Organisms able to recognise relatives may be able to assess increased levels of relatedness at expanding range margins and to increase their dispersal in a plastic manner. Using individual-based simulations and experimental range expansions of a spider mite, we demonstrate that plastic responses to kin structure can be at least as important as evolution in driving range expansion speed. Because recognition of kin or kind is increasingly documented across the tree of life, we anticipate it to be a highly important but neglected driver of range expansions.

ecology↗

bioRxiv2017

Individual boldness is life stage-dependent and linked to dispersal in a hermaphrodite land snail

Both individual variation in dispersal tendency and animal personalities have been shown to be widespread in nature. They are often associated in personality-dependent dispersal, and both have major but underappreciated consequences for ecological and evolutionary dynamics. In addition, personalities are not stable over time and changes can appear through ontogeny, leading to life stage-dependent behaviours. We investigated relationships between dispersal, life stage and boldness in an invertebrate with between- and within-life stages variation in dispersal tendency, the land snail Cornu aspersum. Latency to exit the shell following a simulated attack was repeatable, indicating boldness is a personality trait in Cornu aspersum. Subadults were bolder and more dispersive than adults. Dispersers were bolder than non-dispersers, independently of boldness changes between life stages. We discuss how these results can be explained in relation with life history strategies in this hermaphrodite species, in particular risk management in the context of reproductive investment.

ecology↗