7 Genetic Structure and Diversity Patterns in Adjacent P0pulations: Arrhenatherum elatius (L_.) Beauv.

摘要: Selective forces, neutral events, and breeding system combined with population size and history of taxa, represent essential factors modulating genetic diversity. The idea that high levels of genetic diversity are positively related with a spade-temporally heterogenous and uncertain environment is well supported by comparative data on both plant and animal species (Nevo, 1978; Maynard-Smith, 1978; Hamrick er al., 1979). It seems that a frequent, perhaps the most common, reaction to disturbance in the natural genetic system is to increase the diversity in different directions, especially by modifying the breeding system. In Hymns vulgart's, for example, the highest proportions of male—sterile individuals (obligate'outcrossing plants) are found in disturbed environments (V aldeyron er al., 1973; Gouyon and Vernet, 1982; Gouyon et al., 1983). In Dactylis glomemta, a popula-tion recently introduced by migration into a …