Dynamic patterns of fitness and diversity of coevolving hosts and parasitoids within a metacommunity

Background/Question/Methods

Many natural populations are characterized by clinal patterns of adaptation – both to the abiotic and the biotic environment. These patterns are of particular interest when populations are embedded within a metacommunity that occurs along an environmental gradient. However, it is unclear how gene flow among communities, interactions between organisms, and environmental gradients interact to drive such clines.  We addressed this question by directly manipulating dispersal and resource input in an experimental metacommunity containing a microbial parasitoid, the bacteriophage T3, and its host, the bacterium Escherichia coli.

Results/Conclusions

We observed that adaptation of parasitoids increased on hosts originating from lower resource communities in the absence of gene flow. However, adaptation decreased along the same resource gradient with experimentally-imposed gene flow of the host and parasitoid. This occurred despite relatively low rates of gene flow. We then determined the diversity of both the host and parasitoid along the resource gradient at the beginning and end of the experiment. Patterns of diversity differed among environments and changed over time, but the direction of these changes differed between the host and parasitoid. Our results demonstrate that patterns of both fitness and diversity resulting from coevolutionary interactions within a metacommunity can be highly dynamic across space and time.