Data from: Exclusion of introduced deer increases size and seed production success in an island-endemic plant species

The presence of extra-local invaders, such as the southern California mule
deer (Odocoileus hemionus) on Santa Catalina Island, may contribute to
more selective and insidious effects within the unique ecosystems that
have evolved in their absence. Studies at the species level may detect
effects not noticed in broader, community level vegetation monitoring or
help tease apart differences in the level of effect among the various
ecological components of an invaded system. In this initial study, we
measured the impacts of herbivory by mule deer, a species native to
analogous habitats on the adjacent mainland, on size and seed production
success for Crocanthemum greenei (island rush-rose), a federally listed
sub-shrub that is not present on mainland California. We found deer
exclusion resulted in an overall increase in stem measurement of 18.8 cm.
Exclosure populations exhibited complete seed production success, whereas
control populations showed significantly reduced success and exhibited
complete failure within 58% of populations. These results show that the
introduced mule deer on Santa Catalina Island are negatively affecting a
federally threatened plant species. This strongly implies that the current
deer management strategy is insufficient, if one of its goals is
biodiversity and endemic species conservation.