Abstracts (first author)
Crab osmoregulation and habitat diversification: does salinity drive physiological evolution?PDF
The colonization of fresh water and dry land reflects physiological transformations that govern water and ion movements between the body fluids and surrounding medium, axiomatically linking osmoregulatory physiology and habitat diversification. Since monophyletic groups store biological information retrievable by adding a phylogenetic component to comparative studies, we examine the evolutionary history of osmoregulation in fiddler crabs (Brachyura, Uca). For each osmoregulatory trait examined, we evaluate: (i) phylogenetic pattern, expressed by the relationship between trait variation and phylogeny, employing an autocorrelation analysis using Moran's I coefficient; (ii) the best evolutionary fitting-model, testing Brownian motion (pure random evolution) and Ornstein-Uhlenbeck (random evolution under stabilizing selection) processes; (iii) the ancestral states, to suggest the transformational series, by squared-change parsimony analyses; and (iv) we test the hypothesis of osmoregulatory evolution associated with salinity using phylogenetic regressions. The traits disclosed suggest a directional or piecewise pattern of change over time, revealing strong phylogenetic structuring: for the first pattern, the significant and positive phylogenetic signal among closely related species, particularly at the species level, falls off with phylogenetic distance; for the second pattern, there is a linear change between significant positive and negative phylogenetic signal with phylogenetic distance, showing strong physiological plasticity. The evolution of most osmoregulatory traits follows the Ornstein-Uhlenbeck model: there is significant, strong stabilizing selection that constrains the osmoregulatory history, forcing each trait toward a central value of variation. At more inclusive levels, osmoregulatory ability and salinity are associated, demonstrating a role for both salinity and shared inheritance in driving the evolution of osmoregulatory physiology in fiddler crabs.