Species-specific responses to landscape fragmentation: implications for management strategies

Habitat fragmentation affects the integrity of many species, but little is known about species-specific sensitivity to fragmentation. Here, we compared the genetic structure of four freshwater fish species differing in their body size (Leuciscus cephalus; Leuciscus leuciscus; Gobio gobio and Phoxinus phoxinus) between a fragmented and a continuous landscape. We tested if, overall, fragmentation affected the genetic structure of these fish species, and if these species differed in their sensitivity to fragmentation. Fragmentation negatively affected the genetic structure of these species. Indeed, irrespective of the species identity, allelic richness and heterozygosity were lower, and population divergence was higher in the fragmented than in the continuous landscape. This response to fragmentation was highly species-specific, with the smallest fish species (P. phoxinus) being slightly affected by fragmentation. On the contrary, fish species of intermediate body size (L. leuciscus and G. gobio) were highly affected, whereas the largest fish species (L. cephalus) was intermediately affected by fragmentation. We discuss the relative role of dispersal ability and effective population size on the responses to fragmentation we report here. The weirs studied here are of considerable historical importance. We therefore conclude that restoration programmes will need to consider both this societal context and the biological characteristics of the species sharing this ecosyste

Genetic admixture between captive-bred and wild individuals affects patterns of dispersal in a brown trout (Salmo trutta) population

Genetic admixture between captive-bred and wild individuals has been demonstrated to affect many individual traits, although little is known about its potential influence on dispersal, an important trait governing the eco-evolutionary dynamics of populations. Here, we quantified and described the spatial distribution of genetic admixture in a brown trout (Salmo trutta) population from a small watershed that was stocked until 1999, and then tested whether or not individual dispersal parameters were related to admixture between wild and captive-bred fish. We genotyped 715 fish at 17 microsatellite loci sampled from both the mainstream and all populated tributaries, as well as 48 fish from the hatchery used to stock the study area. First, we used Bayesian clustering to infer local genetic structure and to quantify genetic admixture. We inferred first generation migrants to identify dispersal events and test which features (genetic admixture, sex and body length) affected dispersal parameters (i.e. probability to disperse, distance of dispersal and direction of the dispersal event). We identified two genetic clusters in the river basin, corresponding to wild fish on the one hand and to fish derived from the captive strain on the other hand, allowing us to define an individual gradient of admixture. Individuals with a strong assignment to the captive strain occurred almost exclusively in some tributaries, and were more likely to disperse towards a tributary than towards a site of the mainstream. Furthermore, dispersal probability increased as the probability of assignment to the captive strain increased, and individuals with an intermediate level of admixture exhibited the lowest dispersal distances. These findings show that various dispersal parameters may be biased by admixture with captive-bred genotypes, and that management policies should take into account the differential spread of captive-bred individuals in wild populations

Dynamique de la relation interspécifique : gardon (rutilus rutilus(L.))-ligule (ligula intestinalis(L.))

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

"Vicious circles" and disease spread : elements of discussion

International audienc

Evidence for host variation in parasite tolerance in a wild fish population

International audienceHosts can protect themselves against parasites by actively reducing parasites burden (i.e. resistance) or by limiting the damages caused by parasites (i.e. tolerance). Disentangling between tolerance and resistance is important for predicting the evolutionary outcomes of host-parasite interaction. Dace (Leuciscus leuciscus) are often parasitized by the ectoparasite Tracheliastes polycolpus which feeds on (and destroys) fins, reducing thus the host's condition. We tested the hypothesis that genetically-based variation in ectoparasite tolerance exists in a wild dace population. We found that moderately heterozygous dace, which are less resistant than highly heterozygous or homozygous dace, tolerated better the effect imposed by T. polycolpus for a given parasite burden. However, tolerance also varied upon environmental conditions, suggesting that genetic and environmentally-based variation exists for both resistance and tolerance in this natural host-parasite system. Moreover, a negative genetic correlation may exist between tolerance and resistance, and hence several evolutionary outcomes are possible in this interacting system

Data from: "De novo assembly transcriptome for the rostrum dace (Leuciscus burdigalensis, Cyprinidae: fish) naturally infected by a copepod ectoparasite" in Genomic Resources Notes accepted 1 December 2014 to 31 January 2015

The emergence of pathogens represents substantial threats to public health, livestock, domesticated animals, and biodiversity. How wild populations respond to emerging pathogens has generated a lot of interest in the last two decades. With the recent advent of high-throughput sequencing technologies it is now possible to develop large transcriptomic resources for non-model organisms, hence allowing new research avenues on the immune responses of hosts from a large taxonomic spectra. We here focused on a wild population of the rostrum dace (Leuciscus burgiladensis) that is infected by Tracheliastes polycolpus, an emerging freshwater ectoparasite copepod. We used next generation Illumina sequencing technology to sequence the transcriptome of eight L. burdigalensis adult individuals collected in natura from the same sampling site. Four individuals were non-infected and four individuals were infected by T. polycolpus. We specifically focused on the spleen, the head kidney and epithelial cells and mucus from the fins, three tissues known to be involved in the immune response of fish. We used the Trinity methodology to reconstruct a de novo full-length transcriptome for L. burdigalensis. The resulting transcriptome will serve as an important broad-scale genomic resource for further studying the response of local population of L. burdigalensis to T. polycolpus pressures

Catch‐related and genetic outcome of adult northern pike Esox lucius stocking in a large river system

International audienceGenetic introgression from stocked adult northern pike Esox lucius to a wild self‐recruiting population was detected in a large river system and some stocked E. lucius survived up to two spawning seasons and dispersed over several kilometres in the river. Moreover, the catch rate of stocked E. lucius by anglers was low (9.6%), hence suggesting that the efficiency of stocking activity is questionable

Host dispersal as the driver of parasite genetic structure: a paradigm lost?

International audienceUnderstanding traits influencing the distribution of genetic diversity has major ecological and evo-lutionary implications for host–parasite interactions. The genetic structure of parasites is expectedto conform to that of their hosts, because host dispersal is generally assumed to drive parasite dis-persal. Here, we used a meta-analysis to test this paradigm and determine whether traits relatedto host dispersal correctly predict the spatial co-distribution of host and parasite genetic variation.We compiled data from empirical work on local adaptation and host–parasite population geneticstructure from a wide range of taxonomic groups. We found that genetic differentiation was sig-nificantly lower in parasites than in hosts, suggesting that dispersal may often be higher for para-sites. A significant correlation in the pairwise genetic differentiation of hosts and parasites wasevident, but surprisingly weak. These results were largely explained by parasite reproductive mode,the proportion of free-living stages in the parasite life cycle and the geographical extent of thestudy; variables related to host dispersal were poor predictors of genetic patterns. Our results donot dispel the paradigm that parasite population genetic structure depends on host dispersal.Rather, we highlight that alternative factors are also important in driving the co-distribution ofhost and parasite genetic variation

Data from: Evolutionary processes driving spatial patterns of intra-specific genetic diversity in river ecosystems

Describing, understanding and predicting the spatial distribution of genetic diversity is a central issue in biological sciences. In river landscapes, it is generally predicted that neutral genetic diversity should increase downstream, but there have been few attempts to test and validate this assumption across taxonomic groups. Moreover, it is still unclear what are the evolutionary processes that may generate this apparent spatial pattern of diversity. Here, we quantitatively synthesized published results from diverse taxa living in river ecosystems, and we performed a meta-analysis to show that a downstream increase in intraspecific genetic diversity (DIGD) actually constitutes a general spatial pattern of biodiversity that is repeatable across taxa. We further demonstrated that DIGD was stronger for strictly waterborne dispersing than for overland dispersing species. However, for a restricted data set focusing on fishes, there was no evidence that DIGD was related to particular species traits. We then searched for general processes underlying DIGD by simulating genetic data in dendritic-like river systems. Simulations revealed that the three processes we considered (downstream-biased dispersal, increase in habitat availability downstream and upstream-directed colonization) might generate DIGD. Using random forest models, we identified from simulations a set of highly informative summary statistics allowing discriminating among the processes causing DIGD. Finally, combining these discriminant statistics and approximate Bayesian computations on a set of twelve empirical case studies, we hypothesized that DIGD were most likely due to the interaction of two of these three processes and that contrary to expectation, they were not solely caused by downstream-biased dispersal

Scripts for simulating data under the eight models

This file contains the .est and .par input files used for simulating the genetic datasets used in this article. There are eight different couples of .est/.par files, each of them being associated to one of the eight models presented in the article. The event at 40,000 generations before present (i.e. all genes in the network were send back to an unique deme at this date, considering a backwards in time timeframe), was used to uniformize coalescence times across simulations and models. Please, check the readme file for additional guidance