Aspects of the population dynamics of Lochmaea suturalis Thompson.,(Coleoptera: Chrysomelidae; sub-family: Galerucinae), the heather beetle : a combined laboratory and modelling approach

Abstract

This thesis describes a series of laboratory and field experiments that quantify the population dynamics of the heather beetle (Lochmaea suturalis Thomson), in relation to temperature and its host plant heather (Calluna vulgaris (L. ) Hull). The sex ratio, fecundity, egg laying threshold temperature, emergence threshold temperature, life stage development periods, and life stage mortalities were investigated. It was shown that the life stages were significantly dependent on temperature, whilst it was shown that there was no significant relationship between larval growth and Calluna vulgaris plants sourced from the study sites. The results of the population dynamics experiments were incorporated into a temperature driven, cohort based, and daily looped, stochastic population dynamics computer model. The temperature component of the model was derived from temperature data collected from nine moorland sites, at different altitudes, where there was shown to be a significant relationship between temperature and altitude. The population dynamics model was run for a fifty year period with a population of I million beetles at seven temperature regimes and five different altitudes. The model predicted that as daily mean temperatures rose, so there was a greater chance of increasing populations and that as altitude increases, so the chance of increasing populations decreases. At a predicted daily mean temperature rise of 2-3'C there was evidence of considerable population increases at lower altitudes, and with a daily mean temperature rise of 4-6'C the beetle population exhibited persistent, large, fluctuating populations in the region of three to sixty fold increases at all modelled altitudes over a number of years. An uncertainty and sensitivity analysis of the model was undertaken utilising a Latin Hypercube Swnpling regime, where it was shown that fecundity, egg mortality and pupal mortality were the most important life history variables in i contributing to the model output imprecision. The thesis discussesth eser esults in the light of predicted climate change and their use as an aid to moorland and heathland managers.