Conclusions générales

Mon doctorat a contribué à la compréhension des mécanismes écologiques responsables de la capacité des organismes à s'adapter à leur milieu. Bien entendu, les interactions montrées à la Figure 1 ne représentent qu’un sous-ensemble des relations possibles entre l’environnement, les forces évolutives et l’ajustement des populations face à des changements environnementaux. De nombreux questionnements persistent, qui représentent autant d’éléments potentiels de recherches futures nous permettant d’améliorer notre compréhension des dynamiques évo-évolutives au sein de ce système d ’étude. Par exemple, le signal apparent de divergence adaptative entre populations de chêne blanc et de chêne vert en Corse pourrait être confirmé par des tests de comparaison des niveaux de différenciation génétique adaptative

(Qst) et des Fst obtenus à l'aide de marqueurs moléculaires neutres, des valeurs de Qst

supérieures au Fstindiquant une divergence adaptative des populations sur les traits (Merilà et

Cmokrak, 2001). De telles analyses nous permettraient de déterminer de façon plus formelle si la structure de populations observée en Corse est le résultat de pressions de sélection divergentes, ou simplement des effets de la dérive génique. De plus, dans un environnement hétérogène tel que celui retrouvé en Corse, tant la présence de flux génique et que de pressions de sélection divergentes peuvent favoriser l’évolution de la plasticité phénotypique (Crispo et

al., 2008). Il serait intéressant d ’approfondir l’étude des mécanismes affectant la présence et la

magnitude de la plasticité phénotypique, par exemple en déterminant la présence de sélection sur la plasticité, ainsi que la relation entre l’environnement et ces pressions de sélection, et ce sur un plus large éventail de traits phénotypiques d’intérêt.

Également, en continuité à mon projet de doctorat, une exploration plus poussée des facteurs causaux de la variabilité interindividuelle des patrons de plasticité au sein des populations de D-Rouvière et E-Muro pourrait infirmer ou confirmer notre hypothèse de spécialisation des individus sur différents types de ressources. Des analyses d'isotopes stables, par exemple, pourraient révéler si les mésanges au sein de ces populations se spécialisent sur des ressources alimentaires différentes (i.e. Hobson et Clark, 1992), ou sont nés au sein d'habitats différents (Hobson et a l, 2004). Aussi, des développements récents et en cours dans le domaine de la

génomique offriraient l’opportunité de déterminer quels gènes sont responsables de la variabilité phénotypique observée, apportant ainsi une compréhension plus fine des mécanismes contribuant à l’adaptation des populations en milieu naturel (van Bers et al.

2012).

De façon plus générale, le domaine de la biologie évolutive bénéficierait de la conduite d'un plus grand nombre d'études effectuées sur plusieurs populations d'une même espèce dans des habitats hétérogènes. En effet, bien que l'étude de la plasticité phénotypique et du potentiel adaptatif des populations soit intéressante en soi, la grande étendue de la variabilité de ces patrons en milieu naturel rend difficile la généralisation des résultats obtenus sur une seule population. La réplication de ces études sur plusieurs populations permet d'avoir une compréhension encore plus globale de l'étendue de la variabilité du potentiel adaptatif des populations en milieu naturel. De plus, une attention particulière devrait être apportée à la quantification des paramètres écologiques des populations sur lesquelles sont effectuées des études en biologie évolutive, afin d'améliorer notre compréhension des effets de l'environnement sur l'évolution des populations. Finalement, bien que nous ayons vu que l'environnement affecte la capacité des populations à répondre aux changements de leur environnement, ce dernier peut être rétroactivement affecté par les réponses plastiques et génétiques des populations (Pelletier et al., 2009). L'exploration de ces dynamiques éco- évolutives nous permettrait de mieux comprendre les mécanismes qui génèrent et maintiennent la grande diversité du monde qui nous entoure.

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