Two primary patterns of body size variation have been recorded in ectotherms in relation to latitudinal/altitudinal shifts. In some, body size increases with increasing latitude/altitude whereas, in others, body size decreases with increasing latitude/altitude. This clinal variation is generally assumed to be caused by local adaptation to environmental conditions however the selective variable(s) (temperature, humidity, diet quality, etc.) is still heavily debated. Here we investigate geographic variation in body size of dark and pale color morphs of males of the bush-cricket Isophya rizeensis collected from 15 locations along an elevation gradient ranging from 350 to 2 500 m. Using an information theoretical approach we evaluate the relative support of four different hypotheses (the temperature size rule, the moisture gradient hypothesis, the seasonal constraint hypothesis, and the primary productivity hypothesis) explaining body size variation along the altitudinal gradient. Body size variation in pale color morphs showed a curvilinear relationship with altitude while dark color morphs showed no variation in body size. Body size variation in pale color morphs was highly correlated with precipitation and temperature seasonality values thus giving strong support for the moisture gradient and seasonal constraint hypothesis. Our results reinforce the importance of gradients in humidity and seasonality over temperature in the creation of altitudinal body size clines and the role of selection for resistance to stress factors in the establishment of these clines. Whether a body size cline is observed or not might also depend on the phenotypic properties of the individuals, like coloration.

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Despite its amazing biodiversity, the Eastern Mediterranean remains a highly understudied region especially when compared to the Western Mediterranean. Scarcity of such studies restrict our understanding of the processes shaping diversity across the entire Mediterranean.To this end we used a combination of molecular markers and presence/absence data from all species of the Eastern Mediterrranean genus Ricotia collected across its full geographic range to determine historical, ecological and evolutionary factors responsible for lineage-specific diversification in this genus. Network analysis based on nuclear ribosomal and chloroplast DNA revealed high genetic structure within all lineages and phylogenetic reconstructions based on the multispecies coalescent showed that within lineage diversification corresponded to the onset of the Mediterranean climate. Reconstruction of ancestral histories indicate the genus originated within Anatolia and slowly spread across the Eastern Mediterranean and Levant using the Taurus mountains. Ecological niche models based on climatic and environmental variables suggest local populations did not go through any major distributional shifts and have persisted in present day habitats since the LGM. Furthermore, niche differentiation tests revealed significant niche differences between closely related species and showed the main variables predicting species limits to be different for each species. Our results give crucial information on the patterns and processes shaping diversity in the Eastern Mediterranean and show the main factor promoting diversification to be local environmental dynamics and ecological specialization and not large scale latitudinal movements as often reported for southern Europe. By determining regional and global patterns of diversification in an eastern Mediterranean genus we further our understanding of the major trends influencing plant diversity in the Mediterranean basin as a whole.

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