Over the past few decades a lot of research focused on invasive exotic plants that were moved outside their distributional range, and demonstrated the dramatic effects of such invaders on local communities. Likewise, translocation within the distributional range, for example in the context of restoration ecology, introduces non-local plant genotypes in communities of local plants and their coevolved fauna. A major concern is that introduced plant genotypes that are maladapted to local conditions hybridize with locally adapted conspecifics, decreasing mean population fitness. Both local adaptation and local maladaptation of plants in relation to their antagonists have however been demonstrated, depending on the mechanism involved. Evidence is growing that intraspecific genetic variation in plants can be a key determinant of the composition of invertebrate communities. Few studies have however investigated the effect of plant genotype on the invertebrate community as a whole. In a field experiment we tested the effect of genotype of the dune grass Ammophila arenaria on the colonization by naturally occurring invertebrates throughout the growing season. Ten replicate plants of six genotypes were grown for a year in the lab, then transplanted to the field according to a randomized design and the presence of invertebrates was monitored weekly. One population of the local genotype, three other genotypes of the local subspecies and two genotypes of a foreign subspecies were used, with difference between genotypes reflecting geographical distance between populations. The effect of plant genetic population, date and position within the experimental plot on the proportion of colonized plants was determined for a set of invertebrate species.
Results/Conclusions
A number of generalist herbivores and detritivores showed strong responses towards plant genotype. They colonized a higher proportion of local and closely related plants than of foreign plants, and were least found on plants belonging to the other subspecies. One specialist herbivore however was able to colonize the large majority of plants, including all genotypes. It seems therefore that in this study system plants are locally maladapted to their herbivores and that the effect of plant genotype on the invertebrate community extends further than the guild of herbivores alone. The observation that a suite of taxonomically diverse species preferentially colonized the local plant genotypes implies that introduced plants might support a substantially reduced invertebrate diversity.
