Evolution of predator dispersal in relation to spatio-temporal prey dynamics : how not to get stuck in the wrong place!

Peer reviewedPublisher PD

The rate of beneficial mutations surfing on the wave of a range expansion

Many theoretical and experimental studies suggest that range expansions can have severe consequences for the gene pool of the expanding population. Due to strongly enhanced genetic drift at the advancing frontier, neutral and weakly deleterious mutations can reach large frequencies in the newly colonized regions, as if they were surfing the front of the range expansion. These findings raise the question of how frequently beneficial mutations successfully surf at shifting range margins, thereby promoting adaptation towards a range-expansion phenotype. Here, we use individual-based simulations to study the surfing statistics of recurrent beneficial mutations on wave-like range expansions in linear habitats. We show that the rate of surfing depends on two strongly antagonistic factors, the probability of surfing given the spatial location of a novel mutation and the rate of occurrence of mutations at that location. The surfing probability strongly increases towards the tip of the wave. Novel mutations are unlikely to surf unless they enjoy a spatial head start compared to the bulk of the population. The needed head start is shown to be proportional to the inverse fitness of the mutant type, and only weakly dependent on the carrying capacity. The second factor is the mutation occurrence which strongly decreases towards the tip of the wave. Thus, most successful mutations arise at an intermediate position in the front of the wave. We present an analytic theory for the tradeoff between these factors that allows to predict how frequently substitutions by beneficial mutations occur at invasion fronts. We find that small amounts of genetic drift increase the fixation rate of beneficial mutations at the advancing front, and thus could be important for adaptation during species invasions.Comment: 21 pages, 7 figures; to appear in PLoS Computational Biolog

Cafer Bater'den suluboya sergi

Taha Toros Arşivi, Dosya No: 97-Cafer Bate

Human-induced hybridization among congeneric endemic plants on Tenerife, Canary Islands

Endemic genera on oceanic islands often evolved striking morphological and ecological differences among species, with weak postzygotic reproductive isolation. Human activities can lead to increased connectivity and can thereby promote secondary contact and hybridization between previously isolated species. We studied this phenomenon in three species of the genus Pericallis (Asteraceae) on Tenerife, Canary Islands. A total of 53 populations was sampled, including morphologically uniform as well as mixed populations containing morphologically diverse individuals. All plants were analyzed both genetically using AFLP markers and morphometrically. As expected, morphological analysis clearly separated the plants from the uniform populations in three clusters, with distinguishing characters corresponding to those used in species identification. The three species were also grouped into distinct genetic clusters in a structure analysis, although no private alleles were observed. Adding the mixed population data to the analyses provided evidence for extensive hybridization among species, predominantly between P. cruenta and P. echinata, and between P. cruenta and P. tussilaginis, and morphological and genetic signals were congruent. The mixed populations were geographically located in between the uniform populations and were found in road verges significantly more often than the uniform populations. The observed distribution strongly suggests that hybridization between originally isolated species is recent, promoted by secondary contact due to human disturbance and the construction of roads

Sex ratio rather than population size affects genetic diversity in Antennaria dioica

Rosche C, Schrieber K, Lachmuth S, et al. Sex ratio rather than population size affects genetic diversity in Antennaria dioica. PLANT BIOLOGY. 2018;20(4):789-796.Habitat fragmentation and small population size can lead to genetic erosion in threatened plant populations. Classical theory implies that dioecy can counteract genetic erosion as it decreases the magnitude of inbreeding and genetic drift due to obligate outcrossing. However, in small populations, sex ratios may be strongly male- or female-biased, leading to substantial reductions in effective population size. This may theoretically result in a unimodal relationship between sex ratios and genetic diversity; yet, empirical studies on this relationship are scarce. Using AFLP markers, we studied genetic diversity, structure and differentiation in 14 highly fragmented Antennaria dioica populations from the Central European lowlands. Our analyses focused on the relationship between sex ratio, population size and genetic diversity. Although most populations were small (mean: 35.5 patches), genetic diversity was moderately high. We found evidence for isolation-by-distance, but overall differentiation of the populations was rather weak. Females dominated 11 populations, which overall resulted in a slightly female-biased sex ratio (61.5%). There was no significant relationship between population size and genetic diversity. The proportion of females was not unimodally but positively linearly related to genetic diversity. The high genetic diversity and low genetic differentiation suggest that A.dioica has been widely distributed in the Central European lowlands in the past, while fragmentation occurred only in the last decades. Sex ratio has more immediate consequences on genetic diversity than population size. An increasing proportion of females can increase genetic diversity in dioecious plants, probably due to a higher amount of sexual reproduction

Rapid Plant Invasion in Distinct Climates Involves Different Sources of Phenotypic Variation

When exotic species spread over novel environments, their phenotype will depend on a combination of different processes, including phenotypic plasticity (PP), local adaptation (LA), environmental maternal effects (EME) and genetic drift (GD). Few attempts have been made to simultaneously address the importance of those processes in plant invasion. The present study uses the well-documented invasion history of Senecio inaequidens (Asteraceae) in southern France, where it was introduced at a single wool-processing site. It gradually invaded the Mediterranean coast and the Pyrenean Mountains, which have noticeably different climates. We used seeds from Pyrenean and Mediterranean populations, as well as populations from the first introduction area, to explore the phenotypic variation related to climatic variation. A reciprocal sowing experiment was performed with gardens under Mediterranean and Pyrenean climates. We analyzed climatic phenotypic variation in germination, growth, reproduction, leaf physiology and survival. Genetic structure in the studied invasion area was characterized using AFLP. We found consistent genetic differentiation in growth traits but no home-site advantage, so weak support for LA to climate. In contrast, genetic differentiation showed a relationship with colonization history. PP in response to climate was observed for most traits, and it played an important role in leaf trait variation. EME mediated by seed mass influenced all but leaf traits in a Pyrenean climate. Heavier, earlier-germinating seeds produced larger individuals that produced more flower heads throughout the growing season. However, in the Mediterranean garden, seed mass only influenced the germination rate. The results show that phenotypic variation in response to climate depends on various ecological and evolutionary processes associated with geographical zone and life history traits. Seeing the relative importance of EME and GD, we argue that a “local adaptation vs. phenotypic plasticity” approach is therefore not sufficient to fully understand what shapes phenotypic variation and genetic architecture of invasive populations