Genetic differentiation ofAgrostis capillarisin a grassland system with stable heterogeneity due to terricolous ants

Abstract

SummaryWe examined whether two different grassland microhabitats forming a stable mosaic (anthills and surrounding grassland) are colonized by different genotypes of a common grass,Agrostis capillaris, and thus maintain genetic variation in the species.The potential of individualAgrostisgenotypes, coming from different microhabitats, to withstand burial by ants was examined under experimental burial conditions. The same genotypes were then planted into these microhabitats in a reciprocal fashion to test whether their performance differs according to their source microhabitat. Isozymes were used to identify genet diversities and mean genet sizes at the microhabitats. They were also used to determine whether there is any indication that different genets occupy each of these microhabitats.The burial experiment showed a high genetic variation between clones, both in overall performance (mean over both environments) and in their plastic response to burial. Variation in the way individual clones respond differently to changes in their environment was observed. In contrast to the response in the burial experiment, no clone–origin interaction was found in the transplant experiment. The performance of all plants on the anthills was significantly lower than on other habitats.Isozyme analyses showed that the number of genets (per ramet sampled) on anthills is significantly lower than in the surrounding grassland. It also indicated a partial separation of genets into these microhabitats compared with homogeneous grassland conditions.The harsh environment of anthills therefore acts as a filter for the total pool ofAgrostisgenets in the grassland, with only the fastest growing clones able to survive under these conditions. AsAgrostisis capable of extensive clonal growth, it is able to cross microhabitats given sufficient time. Isozyme data showed that the contribution from generative reproduction is very low. Such a system indicates some ‘genet sorting’ through vegetative growth instead of genetic differentiation.