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Research Interests

The video playing within this page gives you an picture of how my current research interests and my teaching of undergraduates intersect (Film by Alan Fisher; portion of "Aquatic Invasives" by Texas Parks and Wildlife).

My research interests all center on the importance of trophic interactions within shallow water bodies, particularly direct and indirect relationships between invertebrates and macrophytes. On the larger scale, I want to know how these interactions influence shifts in community structure and ecosystem function.


In addition to lab alumni and current students, collaborators on applesnail research include Mariana Meerhoff (email) and colleagues in Uruguay, Mark Kramer (email) at Armand Bayou Nature Center and Ken Hayes (email) and colleagues in Hawaii (for molecular IDs).

Some past and current research questions include:

1. How does the basic fecundity of Pomacea insularum in Texas compare with fecundity of native Pomacea canaliculata in Uruguay or other invasive exotic populations of this species?

2. What factors influence oviposition behavior of female applesnails and what implications might this research offer for management of this exotic species?

3. What sensory cues do snails rely on to detect predators and what predators potentially control populations in native and exotic habitats?


My graduate and postdoctoral work focused on the role that Daphnia (a small crustacean) play in shallow lake systems. In particular, I have investigated how these pelagic invertebrates interact with littoral macrophytes when avoiding predation through diel horizontal migration. Upon arriving at Southwestern, a student (Becca Marfurt Fordham) brought to me a rather large and intellectually enticing invertebrate, i.e. an applesnail. Since 2004, I have focused my efforts on investigating the ecology and life history of this invasive exotic mollusk. Fortunately, doing my Ph.D. with David Lodge at the University of Notre Dame, gave me some insights into how to approach this research, even I never thought I would became a "snail biologist!"

If you want to know more....read further about "A Tale of Two Snails..." In 2000, a new molluscan invader established reproducing populations in Houston, Texas, within a large urban wildlife refuge (i.e. 2500-acre Armand Bayou Nature Center). This snail was like nothing biologists had ever seen before. Adults have the capacity to reach 150-g in weight, lay thousands of eggs in one clutch and aestivate through short drought periods. Brilliantly-colored pink egg clutches, which females lay above the water, quickly sprouted up everywhere.

Economic and ecological concerns flared immediately after this new invader became known as a ‘channeled applesnail’ with a reputation of global invasion and negative impacts on rice fields. Texas Parks and Wildlife Department moved swiftly to list these new invaders as prohibited and identified them as ‘Pomacea canaliculata’ (Howells & Smith 2002) or ‘golden applesnails (GAS)’(Joshi & Sebastian 2006). Neck and Schultz (1992) provided the first evidence of large applesnails in Texas, but no establishment occurred until 1999-2000 (Howells 2001). In May of 2005, invasive applesnails established in Everglades National Park, where they might compete with the only native applesnail found in North America, Pomacea paludosa. Any threats to P. paludosa attract attention because of its role as food for a federally endangered kite, Rostrhamus sociabilis (Skip Snow, USFWS, personal communication). As confirmed introductions of snails increased and ecology of these snails began to garner more interest, phylogenetic studies (Rawlings et al. 2007) of globally distributed populations of applesnails were occurring at the University of Hawaii by Robert Cowie & Ken Hayes and at Florida International University by Tim Collins and Tim Rawlings. In 2004-2005, researchers in Texas identified exotic snails as part of the ‘canaliculata’ complex.

In December of 2005, Brandon Boland and I traveled to Uruguay to work in a true, native population of P. canaliculata. Further scientific and genetic clarity recently arrived in May 2006. Although originally suggested to be P. canaliculata, the Texas species has been confirmed as Pomacea insularum, although this information has not yet reached the management community (Rawlings et al. 2007). Both species find their origins in South America and fall within ‘the complex’ but diverge in mitochondrial DNA by ~9% compared to intraspecific variation of 2-3% (Hayes, personal communication). Native P. canaliculata occur throughout Uruguay and Argentina. Known native populations of P. insularum only occur in Brazil and overlapping ranges with P. canaliculata have not been discovered, although museum connections indicate P. insularum has been found in Uruguay (Olazarri 1984).


 

 


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