Comparison of Mediterranean and North Atlantic populations using DEB models

Loggerhead turtles that nest in the Mediterranean sea are geographically and genetically distinct from the North Atlantic (NA) other populations of loggerhead turtles. The individuals belonging to the Mediterranean population, even though belonging to the same species, are consistently (at birth, puberty, and ultimate size) smaller than their conspecifics of the North Atlantic population. Because of their geographical and genetic isolation, the smaller size could be a result of environmental and/or physiological characteristics. The aim of this study was to study the morphological (size) and physiological (metabolism, growth, reproduction) traits of the Mediterranean loggerhead turtles, and to compare the studied traits with those of the North Atlantic loggerhead turtles. The research and comparison were performed in two steps: First, an analysis of size (length and weight) data of the individuals from the two populations was performed. Information gained by this approach was limited to empirical observations, and gave only limited insight into the possible drivers and mechanisms for observed size differences. Second, a mechanistic modeling approach was used to study the physiology of the Mediterranean loggerhead turtles, and thus obtain insights into the possible metabolic responses of the Mediterranean loggerhead turtles to their environment. An energy model based on the Dynamic Energy Budget (DEB) theory was developed for the Mediterranean loggerhead turtle population, and was then compared to the previously developed DEB model for the North Atlantic loggerhead turtle population. Results suggest that the Mediterranean loggerhead turtles have physiologically adapted to the higher salinity and lower food availability of the Mediterranean sea. The physiological condition indices (expected to be smaller for the Mediterranean loggerhead turtles due to lower food availability) are similar between the populations, but markedly different between life events (hatching and nesting) within a population. Parameter values and model predictions specific to the Mediterranean population suggest faster growth and earlier maturation at smaller sizes compared to their North Atlantic relatives. This is consistent with the pattern that has been observed previously, but in this study is linked to physiological adaptations, some of which are empirically very hard to detect, such as