Biodiversity - Week 5

Climate change will surely have effects on biomes, as well as species. Simulations have told us that we should expect loss of tundra, boreal dieback, and forest expansion. With climate change, we would also expect species range shifts towards the poles or higher altitudes. Analyses conducted by Parmesan and Yohe using previous studies showed that out of the 434 species studied, 80% shifted in the expected direction. Analyses on phenologies were conducted for 677 species, of which 87% shifted in the direction expected. Parmesan and Yohe concludes concludes that there is high confidence that climate change is not going to affect living systems in the future, but that it is already affecting living systems.
So how should conservation reserve designs be formulated? It is suggested that the areas being preserved should be bigger rather than smaller, intact rather than fragmented, close to each other rather than isolated from each other, clumped rather than linear, round rather than flat, and there should be corridors connecting the areas. What Hampe and Petit suggests in their rear edge article is to the contrary, however.
Hampe and Petit suggests that because the rear edge is actually more stable and has the highest level of both gamma and beta diversity, it would be beneficial, in terms of preserving biodiversity, to preserve these "pockets" of stable populations. What they are suggesting is that preserving fragmented areas is better than intact with stable rear edge populations because of the high level of between population diversity. In this special case, losing one population is not as critical because within-population diversity is low, therefore the risk of losing biodiversity is spread over a wide range of populations, thus adding stability. What is troubling about what this reading suggests is that it implies a strong criteria to which species would have to meet in order to be this special type and a dependency on the geography. What is also questionable is whether this theory still holds with the change in climate in the opposite direction as the past. Will this be the pattern observed regardless to whether the change is in the warming trend or cooling trend.
While Hampe and Petite's article argued against the center-periphery hypothesis, which predicts that marginal populations are genetically less diverse and therefore more prone to extinction than those from the center, Webb et al.'s findings with upland vs bog red spruce population supports the hypothesis. They discovered that upland populations were of more recent colonization, as opposed to the wetlands which spanned a broader range of ages, suggesting a higher level of diversity among the trees in the wetland.