Abstracts (first author)

Talk 

Eco-evolutionary dynamics and the evolution of sex

Author(s): Becks L

Summary:

The evolution of sexual reproduction is one of the most important and controversial problems in evolutionary biology because sexual reproduction is almost universal while its inherent costs have made its maintenance difficult to explain. Major hypotheses on the evolution of sex predict sex to be advantageous when the environment changes frequently over time. Recurrent change can occur as a result of eco-evolutionary feedback dynamics but has not been considered in the context of the evolution of sex. An eco-evolutionary feedback loop occurs when environmental change causes natural selection in a population within a few generations, and the resulting trait evolution then modifies the environment, causing further selection and evolution, and so on. An example for this eco-evolutionary feedback comes from a predator-prey system where the algal prey evolves a defence against predation when grazing by rotifer is intense, and loses the defence, but gains competitive ability when the predators (rotifers) are scarce and prey are abundant. I present experimental results showing that the rate of sex evolved to higher rates in the rotifer when eco-evolutionary feedback dynamics occur. In contrast, the rate of sex evolved to lower rates in control populations where the trait evolution in the algae and thus the eco-evolutionary feedback was prohibited. Thus the changes driven by the interplay of ecological and evolutionary change on one time scale can provide conditions allowing for a more globally relevant explanation for the evolution of sex.



Abstracts (coauthor)

Summary:

Understanding the evolutionary advantage of sexual reproduction, as well as its maintenance and widespread occurrence, remain key areas of focus within evolutionary biology. Given the associated costs of sex, including the break-down of potentially beneficial genetic associations via recombination and the time-consuming process of finding a suitable mate, the fundamental question “why sex?” persists. Despite this, complete asexuality in the eukaryotic kingdom is rare and a substantial number of species rely on sex as the sole mode of reproduction. Previous studies have shown sex to confer an advantage in populations exposed to novel environments or intense selective stressors, as recombination can increase genetic variation, thereby facilitating increased rates of adaptation. Asexual populations may reproduce faster, but must then rely on standing genetic variation, which may be very low, and/or novel mutations to supply variation necessary for adaptation, which may happen slowly or not at all. Theoretical models based on these ideas require empirical validation; an effective research framework to study such evolutionary processes in real time would be to combine experimental evolution with ecogenomic analyses as a way to test for adaptive evolution and link phenotype with genotype for ecologically-relevant traits. The purpose of this project is to carry out such a study by using the predator-prey model system of rotifers, Brachionus calyciflorus, and unicellular green alga, Chlamydomonas reinhardtii, to test for adaptive evolutionary responses to rotifer predation in both sexual and asexual lines of alga. Through the use of next-generation sequencing technology and bioinformatics, we aim to better understand the underlying genetic basis of adaptive traits, with respect to defense, in C. reinhardtii. In turn, these results may help to elucidate the evolutionary consequences of sexual versus asexual reproduction, and we can better answer, “Why sex?”

Summary:

It is known that rapid evolutionary processes can play a critical role in host-parasite interactions. Growing evidence suggests that rapid evolutionary change can influences species interactions and thus population dynamics. Here we present results from an experiment with freshwater algal-virus systems, where we examine the role of evolution on host-parasite dynamics for dozens of generations. We followed population dynamics in long-term chemostat experiments, where Chlorella variabilis populations were infected with Chloroviruses. Additional time shift experiments allowed distinguishing the evolution of new genotypes from phenotypic responses to infections. We found that high virus densities selected for resistant host genotypes but that the resistance comes at a cost of reduced competitive abilities. The trade-off between resistance and reduced competitive abilities resulted then in the coexistence of multiple host genotypes and ultimately in the stabilization of the host-parasite dynamics. Thus rapid evolution of host-resistance not only altered the population dynamics but also the maintenance of different genotypes in the host population. Our results underline the importance of rapid evolutionary change for species interactions and population dynamics even on ecological time scales.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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