Organisms and populations may respond to environmental variation in ecological and/or evolutionary time. To understand these responses, I and my students are currently pursuing projects within three broad areas:
1 The physiological, ecological and evolutionary dynamics of resource allocation. Allocation of resources is the crucial step connecting foraging and life history traits such as reproduction, survival, storage and growth. As an additional complication in Lepidoptera, females use male nuptial gifts (spermatophores) for maintenance and egg production, linking the allocation budgets of the two sexes. Changes in resource allocation in response to environmental variation thus affect the evolution of life history strategies and mating systems. These in turn determine population dynamics and limits to a species’ range through effects on individual fitness.
(a) Funded by NSF, we are using Speyeria mormonia to examine how life history traits of reproduction, survival and metabolic rate, along with morphological variation, respond to food and flight stresses. Experimental lab results are connected to responses to environmental variation in the wild and to trait senescence in the wild. The work also tests the theory of nutrient allocation as the basis for life history trade-offs.
(b) What is the structure and function of the gut microbial community in Lepidoptera? Are they nutritional symbionts? We are examining a set of tropical butterflies to answer this question.
(c) We continue to explore the role of "mud-puddling" in the foraging biology of butterflies.
2 Invasion dynamics.
Our focus is on the ecological and evolutionary response of native species to introduced species. Non-native species invading a local community can intrude into coevolved interactions among native species, sometimes disrupting those relationships. We are using the native butterfly/ non-native host system of Pieris napi macdunnoughii / Thlaspi arvense to explore the ecological and evolutionary impacts of such events. Female P. n. macdunnoughii recognize T. arvense as a potential larval host and oviposit on it; however, resulting early instar larvae cannot develop on the plant, as the plant is apparently distasteful. Both European and North American T. arvense are readily eaten by European P. n. napi (Boggs & Wiklund, mss). Oviposition preference is affected by both environmental and sex-linked genetic factors (Boggs et al., mss). No detectable genetic variation for larval survival is present, although hybridization studies with European P. napi indicate that the trait is under autosomal genetic control (Boggs & Wiklund, mss).
Using spatially explicit modelling, we are examining how the spatial distribution of native and non-native hosts affects the ecological and evolutionary dynamics of the butterfly population.
3. Ecology, evolution and genomics of small populations.
We are using an introduced butterfly population of Euphydryas gillettii in Colorado to address various questions in ecology and evolution. The population stayed at low numbers for over twenty-five generations after translocation, then underwent a population explosion followed by changes in population size of orders of magnitude from year to year (Boggs et al. 2006). Additionally, the population has been completely isolated since its introduction, constituting a "Drosophila bottle population genetics experiment" in the wild. We recently discovered a discrete second population.
(a) Using long-term demographic and weather data for the population, we are constructing a model examining the role of climate in controlling the population size, and climate change in affecting the population outbreak. In addition, we are collecting data collection on populations in the native range, in order to ask whether changes in vital rates reflect changes in the environment or in the genetics of the inbred introduced population.
(b) Using genomic approaches, we are taking advantage of the known demography of the introduced population to ask how much of the genome is subject to balancing selection. We also plan to examine balancing selection over the developmental trajectory. As part of this work, we are constructing a scaffold genome for this non-model organism.