The Evolution and Conservation Ecology of the Lundy Cabbage and Its Beetles

Uniquely in Britain, Lundy Island in the Bristol Channel has an endemic plant, ~undy cabbage (Coincya wrighlii (Brassicaceae)), supporting endemic plant-feeding beetles. The specific status of Psyl/iodes /uridipennis (Chrysomelidae) is generally accepted, but the taxonomic status of the ot~er two beetle taxa is unclear. Psylliodes napi on Lundy are all brachypterous and considered to be broader in body than their mainland counterparts, while the widespread weevil Ceutorhynchus contractus (Curculionidae) has a unique pale form on Lundy (c. contractus f. pal/ipes) as well as individuals of normal colouration. The research described here aimed to clarify the taxonomic status of these beetles and to investigate their evolutionary history. Morphometric and molecular approaches were used to investigate the level of divergence of the Lundy beetles from their closest mainland relatives. P. /uridipennis appears to have only recently diverged from P. marcidus, possibly as a result of isolation on Lundy, but morphological, behavioural and colour characters support its specific status. Multiple divergent mitochondrial gene copies were found in individuals of P. marcidus and P. /uridipennis; heteroplasmy and nuclear pseudogenes are discussed as possible explanations.. No genetic or morphological differentiation was detected between P. napi from Lundy and mainland Britain, and brachyptery was found to be common throughout Britain, suggesting that Lundy specimens are not exceptional. Both colour morphs of what. is currently recognised as C. contractus on Lundy (together with a population from northwest Spain) were genetically and morphologically distinct from other European C. contractus, and may represent an undescribed species. Endemic species merit a high conservation priority. Factors influencing the population dynamics of Coincya wrightii were studied using a 13-year dataset. A combination of previous year flowering plant numbers, rabbit densities and rainfall is implicated in driving the dramatic fluctuations in numbers of the plant and consequently the abundance of the endemic beetles it hosts.EThOS - Electronic Theses Online ServiceGBUnited Kingdo