On the polymorphism of cyanogenesis in Lotus corniculatus L.

Abstract

SUMMARYEcological studies on the cyanogenic form of Lotus corniculatus L. on the high dunes of West Holland do not support the hypothesis that grazing by rabbits is an important factor in the maintenance of the dine.

On the polymorphism of cyanogenesis in Lotus corniculatus L. IX. Selective herbivory in natural populations at Porthdafarch, Anglesey

“…Leaf feeding insects appear to be infrequent on both the cliff and mound and most of the leaf damage at Porthdafarch was attributable to feeding by molluscs. The difference in damage levels between the two areas is nonetheless smaller than might have been predicted from the considerably higher density of molluscs recorded previously on the mound (Ellis et a!., 1977). This may reflect the increased relative palatability of the predominantly acyanogenic cliff population.…”

“…Leaf 1959and 1975(Ellis et a!., 1977, but the cliff has retained a lower proportion of cyanogenic individuals. Within each site there is considerable variation between the proportions of cyanogenic plants recorded on different sampling dates.…”

“…coast of Holy Island, Anglesey (Grid Reference SH 234 799) and has been described and illustrated by Ellis et al (1977). There are three clearly defined areas, termed the cliff, the hollow and the mound, with the cliff separated from the mound by a distance of approximately 150 metres.…”

“…In 1979 the plants on the cliff and mound were sampled at intervals of at least one metre by removing a flower umbel and its associated leafy stem. The areas sampled on the cliff and the mound were essentially the same as those previously sampled (Ellis et a!., 1977). The sampling method used has been described earlier (Jones, 1977) although it should be emphasised that the sampling points were distributed throughout each area.…”

“…Because this dine appeared to have been stable for several years and the two inland sites had essentially the same proportions of cyanogenic plants, in spite of being topographically very different, Ellis et a!., (1977) sought those environmental factors common to the inland sites by which they differed from the cliff site. They determined that the distribution of molluscs known to graze the acyanogenic form preferentially (Jones, 1966, Crawford-Sidebotham, 1972, together with "exposure" to wind and salt spray from the sea, were the principal factors involved.…”