Trajectòries evolutives de caracters relacionats amb l'eficàcia biològica

How fast can evolution occur in nature? Are evolutionary trajectories predictable or contingent? Answers to these questions are not only fundamental from an academic point of view, but will also shed light on the more practical and acute problem of forescasting the evolutionary responses of natural populations to the current greenhouse-induced increase in world temperatures. Recently introduced species that quickly colonize large geographic areas provide natural experiments that allow us to explore the dynamics and predictability of evolution. A suitable model systems is the historically Paleartic species Drosophila subobscura, which was accidentally introduced into both North and South America about two decades ago. The first studies of possible rapid and predictable evolution focused on chromosomal inversions, and it became quite clear that parallel latitudinal clines to the long-standing ones in original European populations rapidly developed within about seven years (or approximately 35 generations). More recently latitudinal clinal variation in wing size and shape has also evolved in colonizing populations rapidly developed within about seven years (or approximately 35 generations). More recently, latitudinal clinal variation in wing size and shape has also evolved in colonizing populations. While the size is also consistent to that found in original populations (and globally in other Drosophila species), different parts of the wing have evolved in North America and Europe. Overall, the results suggest that fast evolution can indeed occur on a continental scale, and that 'chance and necessity" are simultaneously playing their roles in the process of adaptation. However, an ultimate understanding of the environmental factors and the underlying genetic details involved in the evolutionary responses will only come from carefully conducted experiments in laboratory populations