Edaphic ecotypic divergence in Senecio vulgaris and the evolutionary potential of predominantly self-fertilising species

Abstract

ABSTRACT Background There is continued interest in ecotypic divergence because it is informative of local adaptation and can be an important step in speciation. Aim To investigate ecotypic divergence in a predominantly self-fertilising species, Senecio vulgaris, in response to variation in soil nitrogen (N) and phosphorus (P) concentrations. Methods Responses to increased N and P were compared among populations sampled from sand dune, bird sanctuary and garden habitats, containing soils of low, high and intermediate fertility, respectively. Responses were measured in terms of growth, with capitulum production and days to seed set recorded in some experiments. Results Population differences in response to increased N and P were detected and linked to differences in soil fertility among habitats. Thus, the sand dune population exhibited the lowest growth response to increased N and P concentrations, while a bird sanctuary population showed the greatest response to increased N supplied as either NaNO3, NH4NO3 or urea. Genetic variation in response to increased N was present in both of these populations. Conclusions The results indicate the presence of edaphic ecotypes in S. vulgaris, providing further evidence that questions the premise that self-fertilisation limits adaptation to environmental change and thus is an evolutionary dead-end.