A Comparison of the Pollination Ecology of Arum Maculatum and Arum Italicum in England

Abstract

Britain is considered to have two native species of Arum; the common Lords & Ladies, A. maculatum L., and the Rare Lords and Ladies, A. italicum Miller subsp. neglectum F. Towns. Currently A. italicum subsp. neglectum occurs only as thinly scattered populations spread across southern England and the Channel Islands. This study investigates whether part of the reason for the rarity of A. italicum subsp. neglectum in Britain is because it has different pollinator requirements to that of its very common close relative, A. maculatum. Results indicate that although the inflorescence odour composition of the two species are different, they attract similar suites of insects. Most insects caught by the plants were female Psychoda phalaenoides L., but both A. maculatum and A. italicum subsp. neglectum also caught substantial numbers of females of another species of midge, Smittia pratorum Goetghebuer. Both P. phalaenoides and S. pratorum were found to carry Arum pollen between plants but S. pratorum generally carried much smaller pollen loads than P. phalaenoides. The main pollinator of Arum italicum subsp. italicum Miller was also found to be P. phalaenoides. In conclusion, as female P. phalaenoides are readily available throughout the flowering period of A. maculatum and A. italicum, pollinator limitation is unlikely to be a reason for the rarity of A. italicum subsp. neglectum in Britain.