Myophily in the critically endangered umbelliferous plant Ostericum palustre Besser (Apiaceae)

Abstract

Globally, many plant species face human-induced habitat loss and an associated reduction in population size and vitality. Their survival is often possible only when appropriate conservation measures are taken that address the biology and ecology of these species, including their reproduction, often the most vulnerable stage in the life history of the organism. Unfortunately, little is known about these aspects of the biology of many listed plant species. For 3 years, we studied the pollination biology of the critically endangered plant species Ostericum palustre Besser (Apiaceae), one that is listed in the Bern Convention and Annex II of the EU Flora–Fauna Directive. Flowers of this taxon were visited by over 81 species of anthophilous insects derived from 5 taxonomic orders, indicating the presence of a generalised pollination system. However, detailed analyses of the frequency of insect visits, pollen loads and insect behaviour on inflorescences suggest that the plant is chiefly pollinated by large Dipterans, predominantly large Syrphid flies and Muscoid flies, that together are often responsible for over 90 % of total pollinations. Occasionally, wasps (Vespidae) may also be involved in the pollination of this species. With respect to the pollination system of O. palustre, our results indicate that this is a classic example of myophily, and generally, this species can be regarded as a functional specialist, but like many other members of Apiaceae, it is a typical “bet-hedger”. This strategy may probably increase the plant’s reproductive success in a range of habitat conditions, suggesting that the pollination system is unlikely to be the cause of rarity in this species.