Research Interests

My primary research interest focuses on reconstructing caenogastropod phylogeny, particularly that of columbellid neogastropods. I am specifically interested in using the phylogenies to investigate evolutionary patterns in key character suites. For instance, my published columbellid phylogeny in Invertebrate Biology (1999) is used in that paper to investigate the evolution of gut characters associated with herbivory, as well as to suggest certain taxonomic corrections. Much more work will be necessary to understand the patterns of diversification within Columbellidae.

I am currently embarking into molecular phylogenetics and biogeography, with two projects. The first is a study of phylogeographic patterns in benthic marine organisms of the Hawaiian Islands. Marine organisms in Hawaii are generally considered to be panmictic throughout the islands. This is however likely not be true for species with little or no dispersal ability, and the degree of gene flow occurring between benthic marine populations is an important consideration for establishing conservation strategies.This project seeks to identify common patterns of gene flow throughout the islands, as well as the degree of gene flow between the Hawaiian Islands and nominally conspecific populations in other areas of the Pacific. At present we are focusing on investigating population structure in various species of benthic marine snails with differing modes of larval development, using mitochondrial gene sequences.

The second project will use columbellid phylogenies to investigate the evolution of small body size. Columbellids are a highly diverse group of small species (many of 10 to 20 mm shell length), but  within the family there are one or more clades of species (mostly in the tropical west Pacific) that reach no more than 4 mm in shell length, for instance the adult Seminella pictured at left. A question that few researchers have been able to address is how gastropod anatomy changes in the evolution of taxa with very small adult sizes. Small body size can be achieved through one or both of two evolutionary shifts: miniaturization (downsizing the entire anatomical plan), or loss or reduction of body parts (often resulting in paedomorphosis). Columbellids are known to display reduction in size or total absence of some organs, and also vary in somatic cell sizes in some organs.  Resolving the predominant evolutionary changes that have occurred in the evolution of small columbellids will illustrate how this process may in fact have occurred in the origins of many major molluscan taxa, as well as other animal groups.

I have also done research on gastropod reproductive anatomy and development (deMaintenon 2001a, 2001b, deMaintenon & Mikkelsen 2001). The objectives of this work are to investigate the redominance of heterochronic processes in gastropod evolution, and at the same time identify homologies in the gastropod reproductive system. In the last decade, interest has increased tremendously in evolutionary developmental biology. At the same time, great progress has been made in reconstructing gastropod phylogeny, much of it using molecular data. This project unites these two areas, by investigating the evolution of gastropod organogenetic patterns. The reproductive system in molluscs is a mosaic system constructed of both ectodermal and mesodermal tissues, and it develops late in ontogeny from two or more independent primordia. Through investigation of reproductive tract development in a phylogenetic context, the nature of evolutionary changes in organ system development can be identified, and hypotheses tested regarding the frequency of paedomorphic changes in gastropod evolution. Investigation of organ system development is also tremendously informative for suggesting homologies in reproductive anatomy (often considered intractable by systematists), which then can then be used in phylogenetic research.