Current Research and Research Interests

M.S. Thesis:

Differential reproductive effort and gene expression in the life histories of Mastocarpus papillatus

Geographic parthenogenesis is a common spatial distribution pattern of sexual organisms and their closely related asexual counterparts, with asexuals found in more extreme environments (e.g., toward the poles). Despite being taxonomically widespread, the processes that maintain this pattern have remained relatively unaddressed. However, in light of widespread ecosystem degradation, understanding these processes is especially important. Our current understanding suggests that environmental change favors sexuality, asexuality is found in persistently stressful conditions and that this pattern is overlaid on present-time ecological interactions. Therefore, it is particularly germane to address these questions in an effort to assess how stress and change are manifested in the ecology of the intertidal zone.
     Perhaps one of the limitations to testing processes that underlie spatial patterning in life cycle variation is the necessity of finding a model organism that is small, accessible, displays a broad geographic range, and exhibits a diverse life history. Intertidal seaweeds, such as the red macroalga Mastocarpus papillatus, are ideal subjects for exploring these processes as they exhibit the above characteristics and all life histories can be cultured in the laboratory. Sexual and asexual variants are sympatric throughout the range, but the probability of finding an asexual gametophyte is greater at northern latitudes. One hypothetical driver of this pattern is suggested to be the result of differential spore production. In order to address this, I will examine spore production by quantifying reproductive effort of sexual and asexual females and crustose tetrasporophytes. Further, these results will be united with an analysis of differential gene expression using a standard cDNA (complementary) subtraction protocol. I will quantify expression differences between sexual and asexual variants and between tetrasporophytes (crusts) and gametophytes (uprights). The different genes will be compared to existing databases to see if they are linked to the life history variants, such as differences in reproductive mode or in morphology. However, any genetic differences are potentially compelling.
Understanding differential reproductive effort and gene expression will aid in our understanding of the maintenance of geographic parthenogenesis. Further, the use of models is particularly relevant for questions addressing the consequences of ecosystem degradation. Mastocarpus is a practical choice as it is an abundant primary producer and has a variety of free-living life cycle types. This presents us with the unique opportunity to explore the effects of environmental change on intertidal ecology.