Even today's broadest taxonomic groups originated in the distant past as diversifications of single species, the progeny of which then proceeded along their own evolutionary paths. While these ancient diversifications will never be observed directly, patterns and processes leading to radiations of taxa that exist today can be studied. Thus, in order to truly understand how the tree of life came to be, ways to analyze genome-wide data at lower taxonomic levels must be found. The research will address this goal by integrating new, high throughput sequencing technologies with modern evolutionary analyses. The potential of this method will be explored by applying it to a difficult problem - the resolution of systematic relationships and patterns of morphological evolution in New World representatives of the bat genus Myotis. However, while the focus of this work is a single bat genus, the method will be broadly applicable to any taxonomic group in which retrotransposons (self-amplifying, neutral genetic elements in the genome) have been active during the radiation of interest.
The methods to be developed have great potential in providing markers that are variable enough to resolve rapid radiations, while also being straightforward to analyze. Moreover, because this methodology is expected to be relatively inexpensive, it is anticipated that it will prove appealing to small labs that focus on resolving relationships among closely related species. The integration of multiple subdisciplines of Biology is often discussed but rarely realized. This project represents a unique attempt to integrate modern computational biological tools using genome level data and well established morphometric analyses. This project will contribute to the infrastructure of science by amassing tissue, skin and skeletal material that will fill gaps in terms of members of the genus Myotis and nontarget taxa. These materials will be deposited in a public repository (Museum of Natural History, LSU) and will be available in perpetuity to the scientific community. Finally, education and outreach to the local communities will be based on the investigation of a charismatic taxonomic group and will improve research and education in two traditionally underdeveloped states.
The objectives of this collaborative study were to develop a new set of phylogenetic markers used to reconstruct the evolutionary history of organisms based on mobile elements and to use a resultant phylogeny based on these markers to examine the convergent evolution and patterns of secondary sexual dimorphism in an important group of New World bats. Myotis bats form the second most species rich genus of mammals and represent around 100 species. The morphological uniformity of these bats is remarkable although recent molecular phylogenetic studies have suggested that within the morphological bounds of this genus there have been numerous cases of convergent evolution. In fact, one interesting aspect of this group is that traditionally they were taxonomically categorized into groups based on three different morphologies. These recent molecular studies have demonstrated that these three different morphologies have evolved independently on most continents. Morphological groups are due to phenotypic convergence on the different continents of the world. We examined patterns of sexual dimorphism in this group and work to more precisely estimate the chain of events leading to convergence are ongoing. While considerable species-specific variation exists, Myotis in general exhibit sexual dimorphism whereby females are larger than males. Sexual dimorphism is more pronounced in external characteristics such as mass and forearm length than in cranial elements. Variation in degree of sexual dimorphism is not related to phylogeny. In other words closely related species do not tend to exhibit similar degrees of sexual dimorphism. A common pattern in nature is Rensch's Rule whereby degree of sexual dimorphism changes allometrically with body size. Myotis does not exhibit Rensch's Rule. Patterns of dimorphism are likely best explained by the "big mother" hypothesis in which increased size in females allows them to invest more energy into production of offspring. In bats in particular, larger females allow them to better meet aerodynamic challenges when carrying a large fetus or newborn. This research involved collaboration among Mississippi State University and Texas Tech. It also involved collaboration with 10 of the largest museum collections in North America (Royal Ontario Museum, Museum of Texas Tech, Museum of Southwestern Biology, Museum of University of Kansas, Smithsonian Institution, American Museum of Natural History, Sam Noble Museum, Louisiana Museum of Natural History, Field Museum of Natural History and the Biodiversity Center of Texas A&M University). International collaborators were Fundacion Moises Bertoni and the Secretary of the Environment, Republic of Paraguay. This research trained two graduate students and 10 undergraduate students, with 90% from groups underrepresented in the STEM fields.
