Restructuring of Skull Modularity Pattern in Evolution Within Myotis myotis-Myotis blythii Species Group (Vespertilionidae, Chiroptera, Mammalia)

Studies of differences in modularity and integration among the related species can provide important information on their evolution. We argue that evolutionary changes in the modularity patterns might be adaptations. We studied a set of 30 craniometric measurements of bats from the Myotis myotis - Myotis blythii species group (Vespertilionidae, Chiroptera, Mammalia): M. m. myotis, M. b. oxygnathus, M. b. omari, M. b. blythii, and M. b. altaicus. Besides, M. dasycneme that is phylogenetically, morphologically, and ecologically rather distant from this group was studied for comparison. We use innovative approach based on the network community detection to analyze covariance structures of these OTUs and test an array of modularity hypotheses for each OTU. We show that covariance structures of M. m. myotis, M. b. oxygnathus, M. b. omari, and M. b. blythii are more similar to each other, while M. b. altaicus and M. dasycneme structures are more different from one another and from other OTUs. The skull modularity decreases with the increasing skull size in the studied OTUs; this pattern is in good agreement with the hypothesis of skull integration increase in evolution of M. myotis-M. blythii species group with increasing size that makes it possible to prey on large hard-shelled insects. The studied OTUs demonstrate both the effect of the covariance structure on evolutionary change and the restructuring of the covariance structure in evolution by selection.