A bimodal pollination system enhances reproductive potential of translocated populations of an endangered grassland succulent

Abstract

A major concern during the translocation of higher plant species is related to habitat suitability and the availability of pollination services. Should these not meet the requirements of the plant, then successful reproduction and establishment cannot occur. We studied an endangered succulent, Frithia humilis, which had previously been translocated to typical and atypical habitats, to assess the occurrence of potential pollinators at these sites. Insects visiting F. humilis flowers and showing signs of pollen were captured, preserved and studied using a scanning electron microscope. Pollen of F. humilis was searched for. Abundance and diversity patterns of these pollen carriers across edaphic habitats of translocated populations were compared with those in a natural occurring population. Pollination success of guilds was compared amongst translocated F. humilis populations by considering the number of seedlings in a new season. Across F. humilis populations, Hymenopteran species had the largest pollen loads, making this a Melittophilous pollination system, typical for the Aizoaceae. Additionally, Anemophilous syndrome was described for translocation sites which provide reserve pollinators. Fruit formation was more favourable in suitable edaphic habitat on Ecca sandstones. Presence of seedlings at both translocation sites was indicative of successful pollination events of the self-incompatible species, but recruitment was proportionally higher in suitable habitat. Habitat suitability, in the case of this threatened species, is more of a limiting factor than pollination services after a translocation event.

Conservation implications: Translocations are fast becoming an attractive alternative for developers. This study cautions that the presence of pollinators and successful reproduction in translocated populations are only effective if the populations were translocated to an ideal habitat.