(WCUB) The effects of temperature and habitat on temporal variartion in the diversity and abundance of Lepidopteran larvae in temperate woodlands

The deciduous tree to Lepidopteran larvae to insectivorous bird food chain is frequently utilised to study the effects of climate change on phenological mismatch. Yet, despite the larvae of Lepidoptera occupying a central position in the food webs of temperate forests, the factors influencing their phenology and abundance within the environment are poorly understood.
Temperature is known to affect rates of larval development in Lepidoptera both continually during feeding and as a cue for the onset of certain life history stages, though how this varies inter- and intra-specifically is unknown. Food-plant identity can also affect rates of development, mortality, adult morphology, and selection on phenology in polyphagous species. Therefore, both temperature and habitat are likely to be major factors in influencing variation in the temporal abundance of Lepidopteran larvae during spring in temperate woodlands.
To predict how climate-induced changes in mismatch vary among woodland habitats it is necessary to understand (1) how the development and phenology of Lepidopteran larvae are affected by temperature, and (2) how these species interact with their food-plants and the consequences of changing habitat and floral communities.
This project aims to identify the temperature cues which trigger stages in larval development (egg hatching), the nature of the plastic response of larvae to temperature, and the contribution of local adaptation to geographical variation in this response. In addition, it will examine how larval diversity and abundance varies with food-plant species, how fitness differs across food-plants in polyphagous species, and the nature of larval phenological synchronisation with food-plants at a site.
This project will employ data collected since 2014 from the Scottish blue tit transect, a set of 40 sites extending 200km northwards from Edinburgh. At each site tree phenology is monitored during spring to record stages of bud burst and caterpillars are collected from a sample of trees. Statistical modelling techniques will be utilised to identify temperature cues for larval development and its influence on temporal variation in abundance, particularly the occurrence of the spring peak. Focus will be placed on 10 caterpillar species most strongly represented in the diet of blue tits. Furthermore, a selection of these species will be reared under laboratory conditions to determine the contribution of genetic divergence to geographical variation in the plastic response to temperature. This project will also combine statistical modelling and experimental rearing of larvae to determine how the abundance and diversity of Lepidopteran larvae varies across food-plants in woodland communities. Further rearing experiments under laboratory conditions will be conducted to determine how larval fitness varies across different food-plants in polyphagous species and with increasing leaf age. Finally, experimental rearing of individuals will be combined with field observations and transect data to determine the underlying adaptive basis of the plastic response (e.g. in egg hatch date) to temperature, and how this relates to the phenology of the food-plant species. Experimental results will be used to inform the modelling process, and the combination of modelling and experimental approaches will generate robust conclusions.