Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Exploring and modeling fluctuating asymmetry and morphology in diverese taxa under sharp microclimatic divegence at the "Evolution Canyons" microsites, "Mount Carmel" and upper Galilee

Auteur : Raz, Shmuel

Etablissement de soutenance : Haïfa University

Grade : Doctor of Philosophy (PhD) 2011

Résumé partiel
Organisms maximize a diverse set of functions to survive in various stressful environments. Thus, they adaptively customize their survival mechanisms to live under the widest possible spectrum of local abiotic and biotic conditions. This spectrum, however, is defined and changes among taxons (i.e., a certain temperature will be optimal to one species and lethal to a different species) and usually optimal in the center of the distribution range of a given population and degrades toward the edge of the distribution range (Parsons, 2005). When a given developmental trajectory deviates from the homeostatic buffer zone, this typically results in stress. Fluctuating Asymmetry (FA- symmetrically distributed deviations about the mean of zero) is a measure of the ability of an individual or population to buffer disruptive effects of developmental noise during growth (i.e., developmental stability) and is the only direct measure of stress at the population level. On the other hand, decreased growth is simultaneously a direct indicator of stress (i.e., stress may dissipate energy away from growth) and a likely adaptive modification to cope with stress. There is, however, a controversy regarding the effect of stress on FA. In some studies, FA increases under environmental biotic and abiotic stress. Conversely, FA does not increase under stress in other studies. The reasons for these inconsistencies may be the following : (i) variability among environments and difficulties in presuming the intensity of stress, (ii) variability among species and their traits in response to biotic and abiotic conditions, (iii) False positive and false negative results and (iv) inadequate use of methodology. Hence, a study based on multiple diverse taxa inhabiting a specific environment with defined stressors and analyzed using similar methodology, is desirable and may, at least partially, resolve the above mentioned inconsistencies among the studies of FA.

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