Positive selection in development and growth rate regulation genes involved in species divergence of the genus Radix.
BACKGROUND
Life history traits like developmental time, age and size at maturity are directly related to fitness in all organisms and play a major role in adaptive evolution and speciation processes. Comparative genomic or transcriptomic approaches to identify positively selected genes involved in species divergence can help to generate hypotheses on the driving forces behind speciation. Here we use a bottom-up approach to investigate this hypothesis by comparative analysis of orthologous transcripts of four closely related European Radix species.


RESULTS
Snails of the genus Radix occupy species specific distribution ranges with distinct climatic niches, indicating a potential for natural selection driven speciation based on ecological niche differentiation. We then inferred phylogenetic relationships among the four Radix species based on whole mt-genomes plus 23 nuclear loci. Three different tests to infer selection and changes in amino acid properties yielded a total of 134 genes with signatures of positive selection. The majority of these genes belonged to the functional gene ontology categories "reproduction" and "genitalia" with an overrepresentation of the functions "development" and "growth rate".


CONCLUSIONS
We show here that Radix species divergence may be primarily enforced by selection on life history traits such as (larval-) development and growth rate. We thus hypothesise that life history differences may confer advantages under the according climate regimes, e.g., species occupying warmer and dryer habitats might have a fitness advantage with fast developing susceptible life stages, which are more tolerant to habitat desiccation.
Molecular Ecology Group, Senckenberg Biodiversity and Climate Research Centre (BiK-F), Georg-Voigt-Str. 14-16, Frankfurt am Main, 60325, Germany. barbara.feldmeyer@senckenberg.de.|Evolutionary Biology, Johannes Gutenberg University Mainz, Müllerweg 6, Mainz, 55099, Germany. barbara.feldmeyer@senckenberg.de.
Barbara
B
Feldmeyer
Molecular Ecology Group, Senckenberg Biodiversity and Climate Research Centre (BiK-F), Georg-Voigt-Str. 14-16, Frankfurt am Main, 60325, Germany. greshake@bio.uni-frankfurt.de.|Applied Bioinformatics Group, Institute of Cell Biology and Neuroscience, Goethe University Frankfurt, Maxvon-Laue Str. 13, Frankfurt am Main, 60438, Germany. greshake@bio.uni-frankfurt.de.
Bastian
B
Greshake
Molecular Ecology Group, Senckenberg Biodiversity and Climate Research Centre (BiK-F), Georg-Voigt-Str. 14-16, Frankfurt am Main, 60325, Germany. elifunke@gmx.de.
Elisabeth
E
Funke
Applied Bioinformatics Group, Institute of Cell Biology and Neuroscience, Goethe University Frankfurt, Maxvon-Laue Str. 13, Frankfurt am Main, 60438, Germany. ebersberger@bio.uni-frankfurt.de.
Ingo
I
Ebersberger
Molecular Ecology Group, Senckenberg Biodiversity and Climate Research Centre (BiK-F), Georg-Voigt-Str. 14-16, Frankfurt am Main, 60325, Germany. Pfenninger@bio.uni-frankfurt.de.
Markus
M
Pfenninger
D000818:Animals; D005075:Biological Evolution; D002980:Climate; D017753:Ecosystem; D005060:Europe; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D010802:Phylogeny; D012641:Selection, Genetic; D012908:Snails / Q000145:classification* / Q000235:genetics* / Q000254:growth & development; D013045:Species Specificity