Genetic Variation of Grassland Species Across an Altitude Gradient
Hahn, T., Kettle, C.J., Ghazoul, J., Frei, E.R., Matter, P. and Pluess, A.R. 2012. Patterns of genetic variation across altitude in three plant species of semi-dry grasslands. PLoS ONE 7: e41608.
The basis for this ominous conclusion, as Hahn et al. describe it, derives from the fact that "habitat suitability typically decreases at the upper edge of the altitudinal range where population size might decline," plus the observation that "in small populations genetic diversity is often reduced and inbreeding may increase (Lynch et al., 1995; Young et al., 1996)," with the result that "low genetic diversity and high inbreeding potentially cause loss of fitness due to fixation of deleterious alleles and inbreeding depression (Ouborg et al., 1991; Lynch et al., 1995; Young et al., 2002), which could affect future population persistence."
Questioning the generality of this suite of speculations, Hahn et al. investigated patterns of population genetic variation in three common plants of semi-dry grasslands - Briza media, a wind-pollinated grass, and Trifolium montanum and Ranunculus bulbosus, both of which are insect-pollinated herbs - at upper peripheral and lower more central altitudes in the Swiss Alps using the amplified fragment length polymorphism (AFLP) technique.
In doing so, the six Swiss scientists determined that contrary to what many have supposed, altitude has not affected genetic diversity in the grassland species they studied. In fact, they say that their study indicates that "populations at the upper periphery are not genetically depauperate or isolated," and that they thus may be "important populations for migration under climate change."
Hahn et al. conclude that what they call the "potentially pre-adapted genes" of the three plant species they studied might well "spread easily across altitudes," which would help to prevent their local extinction in a potentially warming world of the future.
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