Abstracts (first author)

Talk 

Local adaptation drives latitudinal frequency clines for chromosomal inversions in Drosophila subobscura

Author(s): Pascual M, Calabria G, Dolgova O, Balanyà J, Santos M

Summary:

Climate change is already impacting the distribution and behavior of many species. Nonetheless, population genetic changes in response to global warming have been observed only for a few species. This is the case of Drosophila subobscura, a native Palearctic species that harbors a rich chromosomal inversion polymorphism with “warm climate” inversions increasing in frequency worldwide. However, the selective process that maintains inversions in populations is not clear yet. The two main hypotheses differ in how the genetic content of inversions varies along a geographical gradient; the local adaptation hypothesis states that an inversion will have the same genetic content in all populations, while the coadaptation model suggests that in each population the genetic content will be different. In order to elucidate which model is more suitable for D. subobscura, we have analyzed ten genes -six of them are candidates for thermal adaptation- located on the longest and inversion richest chromosome O of the species. The most frequent chromosome arrangements in two Spanish populations along a latitudinal gradient were analyzed. No within-inversion genetic differences were detected among populations, which suggest that the gene content along the gradient is rather constant for the various gene arrangements. Although gene flux between different inversions (either by gene conversion or double crossover) was detected, significant genetic differentiation among inversions for all genes mapped within the inverted fragments of the chromosome was found.



Abstracts (coauthor)

Thermal adaptation genes: inversions, gene flux and selection

Author(s): Mestres, F, Pegueroles C, Martí-Solano M, Pascual M

Summary:

The patterns of genome organization can be influenced by recombination, which is an important evolutionary force. In general, presence of recombination is advantageous, as demonstrated by the evolution of sex in most of the complex organisms. However, recombination can be disadvantageous in some situations, breaking some adaptive combinations of genes. In the present study, we have focused on the study of six thermal candidate genes (Pif1A, Abi, Sqd, Yrt, Atpα and Fmr1) located across the O chromosome of D. subobscura, in relation to three adaptive arrangements (O3+4+1, O3+4+7 and O3+4) collected at Barcelona (Eastern Mediterranean) and Mt. Parnes, Greece (Eastern Mediterranean). Significant genetic differentiation using FST values was found between genes located within inversions (O1 and O7), which is consistent with reduced recombination between inversions. More strikingly, the significant genetic differentiation encountered for the Atpα gene, which is located outside these inversions, is due to fixed nonsynonymous changes between arrangement, and signs of positive selection were detected for the O3+4+7 arrangement. Selective sweeps associated to O1 and O7 inversions were dated in 0.04 and 0.06 Myr, respectively. The similarity of the ATPα protein sequences of O3+4 with that of D. madeirensis may reflect historic events. However, similarity at the protein level between O3+4+1 and O3+4+7 arrangements for the Atpα gene could be the consequence of independent substitutions arisen in the two lineages due to adaptation to similar environmental conditions.

Summary:

Social dominance is important for the reproductive success of males in many species. In fish with external fertilization, it is not as apparent which traits are necessary to become dominant or territorial and what benefits the socially dominant individual. In the black-faced blenny (Tripterygion delaisi) during the reproductive season, some males change color and invest in nest making and defense, whereas sneaker males do not change color and ‘sneak’ reproductions when females lay their eggs. Using RNAseq, we profiled differential gene expression between the brains of territorial males, sneaker males, and females to study the molecular signatures of male dimorphism. Despite several studies reporting high levels of genetic differentiation between sexes, we found that more genes were differentially expressed between the two male phenotypes than between males and females. This suggests that phenotypic plasticity is a more important factor in differential gene expression than sexual dimorphism during the reproductive period. For the dominant male, expression was higher in genes mainly related to cytoskeletal rearrangement indicating the drastic change in behavior and phenotype. We also identified novel genes which are differentially expressed in the brain tissue between the two male mating types in Tripterygion delaisi, which can be further investigated in other fish species with similar mating tactics.

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Chairman: Octávio S. Paulo
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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

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