Biología de la polinización de erysimum endémicos de la alta montaña de sierra nevada: introgresión y extinción silenciosa

Abstract

The main goal of this project was exploring the effect of endemicity in the interaction between plants and their pollinators, and the consequences for the reproduction and genetic diversity and structure. We studied the interaction with pollinators in four co-generic species, two endemic to the Sierra Nevada National Park (Erysimum baeticum baeticumy E. nevadense) and two of wide distribution (E. mediohispanicum y E. popovii). We found that the diversity, identity and abundance of the pollinator assemblages did not differ between endemic and no endemic plants. In all cases, they were visited by a extremely high number (more than 100 spp) of generalist pollinators. Similary, in all cases the pollinator assemblages were composed of efficient and non efficient pollen vectors. The four studies species were also characterized for having spatially varying pollinator assemblages. As a consequence of this variation in pollinators, we observed a significant spatial genetic structure in all studied species. Phylogenetic analysis shows that the four wallflower species co-ocurring in Sierra Nevada belong to different linages within the genus Erysimum. Some if these species, however, can hybridize easily, and they suffer low outbreeding depression. This phenomenon entails the possibility of genetic introgression and the genetic extinction of the endemic species as a consequence of the genetic invasion by the widely-distributed species. Finally, we found that the four species had their seed production limited by an adequate transfer of pollen grain (pollen limitation). In all cases, this pollen limitation was associated to the decrease in pollinator abundance and diversity, and to the absence of high efficient pollen vectors. In conclusion, the outcomes obtained in this project suggest that a efficient strategy of protecting the populations of the endemic wallflowers in the Sierra Nevada National Park requires the concomitant protection and managing of the populations of those mutualist insects that enhance the reproduction of the plants.