TEMPORAL ISOLATION IN A PIERID BUTTERFLY
The pine white butterfly, Neophasia menapia, is a Pierid species found throughout western north America. Typically univoltine, with one generation per year, in California two locations have been discovered where two periods of adult flight occur. As part of my masters I carried out both morphological and population genetic analyses into the two flight populations. In a continuation of this work I am investigating the underlying mechanistic causes of changes in diapause.
In collaboration with:
Art Shapiro, UC Davies
POPULATION GENOMICS OF A TROPHICALLY POLYMORPHIC CICHLID
Herichthys minckleyi is a species of cichlid endemic to the Cuatro Ciénegas basin in northern Mexico. The species is trophically polymorphic, with two morphotypes; papilliform and molarifom. Papilliform individuals have much smaller, needle-like teeth and feed on detritus while molariform individuals have larger molar-like teeth and feed primarily on snails. In order to understand the evolution and maintenance of these two morphotypes we carried out a population genomics approach to investigate genetic differentiation both between morphotypes and between localities within the valley. Preliminary results suggest that there is ongoing gene flow between the two morphotypes. Future work will explore the underlying genetic architecture of jaw morphology using a genome wide association study.
In collaboration with:
Darrin Hulsey, University of Konstanz
EXPLORATION OF THE FITNESS LANDSCAPE OF CHEMICAL SEQUESTRATION
In many specialist herbivorous insects, chemical defense is acquired through sequestration of toxic compounds from plants. Sequestration may affect fitness in two ways: it can increase fitness through defense from predators but it can also be associated with tradeoffs that decrease fitness (i.e. increased development time or reduced energy reserves). The balance of these fitness consequences are typically related to the amount of toxin that is sequestered. Many chemically defended insects advertise their toxicity through aposematic (warning) coloration and gregarious feeding is thought to enhance aposematism. In some cases, however, early instar stages are not aposmatically colored, and it is at this stage where caterpillars most often densely aggregate. In this study we investigate the ecological and evolutionary interactions between group size and toxicity on survival of early instar larvae in a model system for chemical sequestration, the pipevine swallowtail butterfly, Battus philenor. We use a theoretical model to explore the evolutionary consequences of larval toxicity, group size and predator encounter rate. We have been testing the model’s predictions by manipulating caterpillar toxicity using artificial diets and then manipulating group size in the field. We then monitor survivorship under conditions of low and high natural predator densities (variable across years). The advantage of agreggative feeding appears to be strongly influenced by predator densities, and toxicity enhanced per capita survivorship in groups under high predator densities.