Estimation of the congruence between morphogenetic and molecular-genetic modules of gray voles Microtus S.L. variability along a climatic gradient

Abstract

Background. The exponential growth of research concerning a role of morphological modularity and integration in evolution has taking place from the beginning of the century. It was especially noted that inter-level integration should manifest itself, first of all, in the congruent variability of the modules of different structural levels. We analyzed congruence between the interspecific variability of the first lower molar (m1) masticatory surface and the mtDNA Cytb gene in ten species of the gray voles Microtus s.l. from the point of view of the modular organization. Materials and methods. In total, 5306 pairs of chewing surface contours of vole molar m1 were investigated. Thirty one different morphotypes and 187 their different combinations are identified: 30 symmetric and 157 asymmetric. 576 sequences of the Cytb mtDNA gene from the GenBank database are used. Climatic data are taken from the website Climate:Date.org. Data are processed using a DJ-method. The morphogenetic matrix of Euclidean distances between species is obtained from the frequencies of m1 morphotypes co-occurrence from the right and left sides of the lower jaw, and the molecular-genetic one from the frequencies of synonymous codon substitutions. The algorithm is realized in the Jacobi 4 package. Results. A high correlation (r = 0.847) between the first principal component of the molecular-genetic distance matrix and second principal component of the morphogenetic one is found. From the standpoint of the modular organization of the phenotype, the principal components of these matrices are treated as variability modules. The molecular-genetic module is caused by change of frequencies of the codons ACC and GCA along geo-climatic gradient, and morphogenetic one various aspects of the m1 asymmetry. Conclusions. The proposed approach allowed to identify two congruently varying modules from different trait systems of the studied species along the geo-climatic gradient.