FOOD AND FLOODS: FOUR OBSERVATIONS ON ASPECTS OF THE BIOLOGY OF THE ENDANGERED TANSY BEETLE, CHRYSOLINA GRAMINIS (L.) (COLEOPTERA: CHRYSOMELIDAE) AND THEIR IMPLICATIONS FOR CONSERVATION

摘要

Understanding key features of the biology of a species are required for the development of successful conservation strategies. The endangered tansy beetle Chrysolina graminis (L.) is currently known from just three populations in two areas of Britain- the vicinity of York and the East Anglian Fens - where the food plants are almost entirely different. In the wild, York beetles feed almost exclusively on tansy Tanacetum vulgare L. whereas water mint Mentha aquatica L. and gypsywort Lycopus europaeusL. are among a small range of plants eaten by beetles in the Fens. Observations were made on (1) egg-batch size, (2) egg-hatching success and (3) overwintering survival of tansy beetles from York when fed on either water mint or gypsywort. Egg-batch sizewas significantly smaller on water mint than on tansy (control). Egg hatching success was not significantly different between beetles on gypsywort and tansy but overwintering success of adults was markedly worse on gypsywort, at least partly because ofa phenological mismatch between the emergence of beetles and the sprouting of this food plant in spring. The second generation of beetles on water mint failed to lay any viable eggs. The data suggest that the Yorkshire Ouse population may not be well adapted to two of the food plants used by Fenland beetles. The final observation (4) was of the ability of egg batches laid on tansy leaves to survive inundation for up to six days. No eggs were viable after four days under water suggesting a vulnerabilityto spring and early summer floods. These results, together with other information, imply that there might be significant differences in the biology of the two populations, with conservation implications.