Fragmentation and grassland plants: individual and transgenerational effects

Abstract

Understanding how individuals respond to habitat discontinuities could provide a first step in the large-scale evaluation of their responses to habitat fragmentation. Our objective was to evaluate habitat fragmentation effects on individual and population parameters of two native species of the Pampas grassland (Senecio pampeanus and Margyricarpus pinnatus). Both species grow in vegetation remnants surrounded by pine afforestation in the coastal dunes of the southern Pampas (Argentina). Plants reproductive aspects and offspring fitness were examined, and the influence of environmental maternal effects was analyzed through a common garden experiment. Individuals of S. pampeanus growing in smaller fragments produced fewer heads and fewer fruits per head than those associated with the continuous grassland and with larger fragments. However, M. pinnatus did not exhibit any difference in flower and fruit production with respect to fragment size. The seeds that came from the smallest fragments took longer to germinate for the two species, and in the case of M. pinnatus they also showed reductions in percent germination. We found evidence for influence of the maternal environment on percent germination and in seedling establishment time of M. pinnatus. Our results provide clues about the effects of fragmentation on plant reproduction, with consequences for the offspring, and also show that species respond differently according to their biological characteristics. Furthermore, the results obtained contribute to the understanding of mechanisms by which the subdivision of natural environments affects the persistence of populations and alters the structure of plant communities.