Hydrophobicity patterns and biological adaptation: an exemplary case from fish hemoglobins

The dissection of phylogenetic and environmental components in biological evolution is one of the main themes of general biology. Here we propose an approach to this theme relying upon the comparison between a phylogenetic oriented metrics spanning the hemoglobin beta chains of different fishes and a more physiologically oriented metrics defining the same sequences in terms of the dynamical features of their hydrophobic distributions. By analyzing the set of sequences more similar to the Gadus morhua (Atlantic cod) hemoglobin beta chain, we were able to give a proof of concept of the possibility to discriminate the phylogenetic and environmental (evolutive convergence) components by the comparative analysis of the Clustal W (phylogenetics first) and Recurrence Quantification Analysis (physiology first) metrics in which the sequences were embedded. The use of a molecular system like hemoglobin playing a crucial role in fishes adaptation to environmental cues allowed us to span different levels of biological variability by means of the same paradigm. Starting from the reconstruction of the general taxonomy of vertebrate groups we went down to the exploitation of the peculiar role played by Met55Val and Lys62Ala polymorphisms in the beta1 hemoglobin chain of the Atlantic cod able to influence the geographical distribution of its various stocks.