Wednesday, July 13, 2016

Biodiversity and evolution

Pseudomonas fluorescens, bacterial species used
There is a growing awareness that biodiversity not only drives ecosystem services but also affects evolutionary dynamics. However, different theories predict contrasting outcomes on when do evolutionary processes occur within a context of competition. We tested whether functional diversity can explain diversification patterns.

Past studies on ecosystem changes showed both increase and decrease of the net number of new species evolving. In other words evolution can slow down as the result of increased competition for existing niches or the same competition can actually cause adaptive radiation. 

In a new study colleagues from France and Germany explored the evolutionary dynamics of a bacterial species growing in communities with varying levels of biodiversity especially looking at the effects of higher biodiversity. The controlled environment and experimental conditions allowed them to probe into the potential reasons for the contrasting results of prior research.

They found that higher biodiversity stimulates the evolution of species especially under resource constraints:

High functional diversity reduced the fitness of the focal species and, at the same time, fostered its diversification. This pattern was linked to resource competition: High diversity increased competition on a portion of the resources while leaving most underexploited. The evolved phenotypes of the focal species showed a better use of underexploited resources, albeit at a cost of lower overall growth rates. 

The study shows that extinctions not only have an effect to current ecosystem functions but also slow down evolutionary diversification. The authors also believe that as a consequence of the nested structure and compartmentalization of many food webs, higher functional diversity fosters the evolution of new species even at high species richness.

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