Orthologous genes identified by transcriptome sequencing in the spider genus Stegodyphus

<p>Abstract</p> <p>Background</p> <p>The evolution of sociality in spiders involves a transition from an outcrossing to a highly inbreeding mating system, a shift to a female biased sex ratio, and an increase in the reproductive skew among individuals. Taken together, these features are expected to result in a strong reduction in the effective population size. Such a decline in effective population size is expected to affect population genetic and molecular evolutionary processes, resulting in reduced genetic diversity and relaxed selective constraint across the genome. In the genus <it>Stegodyphus</it>, permanent sociality and regular inbreeding has evolved independently three times from periodic-social (outcrossing) ancestors. This genus is therefore an ideal model for comparative studies of the molecular evolutionary and population genetic consequences of the transition to a regularly inbreeding mating system. However, no genetic resources are available for this genus.</p> <p>Results</p> <p>We present the analysis of high throughput transcriptome sequencing of three <it>Stegodyphus </it>species. Two of these are periodic-social (<it>Stegodyphus lineatus </it>and <it>S.tentoriicola</it>) and one is permanently social (<it>S. mimosarum</it>). From non-normalized cDNA libraries, we obtained on average 7,000 putative uni-genes for each species. Three-way orthology, as predicted from reciprocal BLAST, identified 1,792 genes that could be used for cross-species comparison. Open reading frames (ORFs) could be deduced from 1,345 of the three-way alignments. Preliminary molecular analyses suggest a five- to ten-fold reduction in heterozygosity in the social <it>S. mimosarum </it>compared with the periodic-social species. Furthermore, an increased ratio of non-synonymous to synonymous polymorphisms in the social species indicated relaxed efficiency of selection. However, there was no sign of relaxed selection on the phylogenetic branch leading to <it>S. mimosarum</it>.</p> <p>Conclusions</p> <p>The 1,792 three-way ortholog genes identified in this study provide a unique resource for comparative studies of the eco-genomics, population genetics and molecular evolution of repeated evolution of inbreeding sociality within the <it>Stegodyphus </it>genu<it>s</it>. Preliminary analyses support theoretical expectations of depleted heterozygosity and relaxed selection in the social inbreeding species. Relaxed selection could not be detected in the <it>S. mimosarum </it>lineage, suggesting that there has been a recent transition to sociality in this species.</p

Selection at Work in Self-Incompatible Arabidopsis lyrata: Mating Patterns in a Natural Population

Identification and characterization of the self-incompatibility genes in Brassicaceae species now allow typing of self-incompatibility haplotypes in natural populations. In this study we sampled and mapped all 88 individuals in a small population of Arabidopsis lyrata from Iceland. The self-incompatibility haplotypes at the SRK gene were typed for all the plants and some of their progeny and used to investigate the realized mating patterns in the population. The observed frequencies of haplotypes were found to change considerably from the parent generation to the offspring generation around their deterministic equilibria as determined from the known dominance relations among haplotypes. We provide direct evidence that the incompatibility system discriminates against matings among adjacent individuals. Multiple paternity is very common, causing mate availability among progeny of a single mother to be much larger than expected for single paternity

BE Newsletter Issue #12 December 2014

Inside this issue: Editorial – Ronny Billen Playing XBOX@CTF3 – Jose Luis Navarro Quirante & Frank Tecker, BE-OP-PS/CTF3 Independence for Controls – Stefan Lüders, IT-DI-CSO The Smooth Upgrades Working Group – Vito Baggiolini, BE-CO, Leader of the SUWG A Cryogenic Beam Current Monitor for Low-Energy Antiproton Facilities – Miguel Abreu Fernandes, BE-BI-PI Les EIS : Vous connaissez ? – Anne Funken, BE-ASR-SU Safety Column – Safety Unit Life in BE – Juan F. Esteban Müller, BE-RF-BR Responsibility changes & Newsletter contact

Journal of the National Cancer Institute : JNCI

<div><p>The evolutionary history of widespread and specialized species is likely to cause a different genetic architecture of key ecological traits in the two species groups. This may affect how these two groups respond to inbreeding. Here we investigate inbreeding effects in traits related to performance in 5 widespread and 5 tropical restricted species of <i>Drosophila</i> with the aim of testing whether the two species groups suffered differently from inbreeding depression. The traits investigated were egg-to-adult viability, developmental time and resistance to heat, cold and desiccation. Our results showed that levels of inbreeding depression were species and trait specific and did not differ between the species groups for stress resistance traits. However, for the life history traits developmental time and egg-to adult viability, more inbreeding depression was observed in the tropical species. The results reported suggest that for life history traits tropical species of <i>Drosophila</i> will suffer more from inbreeding depression than widespread species in case of increases in the rate of inbreeding e.g. due to declines in population sizes.</p> </div

Average inbreeding depression for the 10 species based on a) average inbreeding depression of the two investigated life history traits for each species (± SE) and b) average inbreeding depression of the four investigated stress resistance traits for each

<p>Black bars are tropical species and grey bars are widespread species. Horizontal black lines represent averages for the tropical and widespread species. The species are: <i>D. bipectinata</i> (bipect), <i>D. birchii</i> (birc), <i>D. bunnanda</i> (bunn), <i>D. hydei</i> (hydei), <i>D. melanogaster</i> (mel), <i>D. pseudoananassae</i> (ps), <i>D. repleta</i> (rep), <i>D. serrata</i> (ser), <i>D. simulans</i> (sim) and <i>D. sulfurigaster</i> (sulf). Symbols: ‘T’ = ‘tropical’ and ‘W’ = ‘widespread’.</p

Inbreeding depression for each of 6 traits (± SE) (a: ‘Developmental time’, b: ‘Egg-to-adult viability’, c: ‘Heat knock down resistance’, d: ‘Chill coma recovery time’, e: ‘Critical thermal minimum (CTmin)’, f: ‘Desiccation resistance’).

<p>Data are split into 4 groups: tropical females (TF), tropical males (TM), widespread females (WF) and widespread males (WM). Horisontal lines represent averages for each of the 4 groups (TF, TM, WF, WM). The species are: <i>D. bipectinata</i> (bipect), <i>D. birchii</i> (birc), <i>D. bunnanda</i> (bunn), <i>D. hydei</i> (hydei), <i>D. melanogaster</i> (mel), <i>D. pseudoananassae</i> (ps), <i>D. repleta</i> (rep), <i>D. serrata</i> (ser), <i>D. simulans</i> (sim) and <i>D. sulfurigaster</i> (sulf). See ‘<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051176#s2" target="_blank">Materials and methods</a>’ for a description of each assay.</p