Rapid Evolutionary Responses to Global Change  

Dr. Carol Eunmi LEE
Department of Integrative Biology  

University of Wisconsin, Madison

430 Lincoln Drive, Birge Hall
University of Wisconsin
Madison, WI 53706

Office:  (608) 262-2675
Lab:  (608) 262-9225


     Ecological Genetics and Functional Mechanics of Zebra and Quagga Mussel Invasions

The zebra mussel Dreissena polymorpha ranks among the most destructive invaders in North America, with economic impacts in the billions of dollars. This species was first reported in 1988 in Lake St. Clair (Hebert et al. 1989), and has subsequently spread rapidly throughout interconnected waterways. However, while the zebra mussel appears to be a successful early colonizer, the quagga mussel D. bugensis ultimately dominates (Mills et al. 1999; Jarvis et al. 2000). For example, quagga mussels have largely displaced zebra mussels in much of the Great Lakes, despite slower growth rates (MacIsaac 1994). Reasons for the displacement had been poorly understood.

Our phylogeographic results suggest that invasive populations from both zebra and quagga mussels originated from brackishwaters of the Black and Caspian Sea region (Gelembiuk et al. 2006; May et al. 2006). However, the original native habitats of the two species were largely non-overlapping, occupying differing salinities (Rosenberg and Ludyanskiy 1994; Spidle et al. 1995). Thus, current invasions in both Europe and North America are exposing the two species to novel evolutionary forces and challenges due to their recent competitive interactions.

While zebra mussels are generally restricted to shallow rocky habitats, quagga mussels possess distinct morphotypes that inhabit both shallow rocky and deep sedimentary habitats. We hypothesized that shell and byssal thread morphology might affect the ability of the two species to colonize habitats that differ in substrate type and hydrodynamic flow. Thus, we examined relationships between variation in shell shape, biomechanical constraints on shape, and habitat utilization in both species.

We found that (1) morphological differences between shallow and deep quagga mussel populations are the result of phenotypic plasticity rather than genetic differentiation (Peyer et al. 2010), (2) biomechanical forces, imposed by substrate type or fluid flow, affect mussel morphotypes that are beneficial in different habitats (Peyer et al. 2009; Peyer et al. 2011), and (3) mussel morphology affects mussel function, such as locomotion and the ability to utilize particular habitat types (Peyer et al. 2009; Peyer et al. 2011).

Thus, the range of habitats that each species could occupy is influenced by their morphology. For instance, we found that the distinct morphotypes of quagga mussels confer functional advantages on differing substrates. Hence, the presence of distinct morphotypes in quagga mussels might bestow the ability to colonize a greater diversity of habitat types, and might contribute to the tendency of quagga mussels to ultimately gain numerical supremacy over zebra mussels. Our study of functional morphology, which integrates molecular genetics, quantitative genetics, and biomechanics, has provided insights into how organismal function could affect the extent of range expansions and condition-specific competition between invading species.

Sample Publications:

Gelembiuk GW, GE May, CE Lee.  2006.  Phylogeography and systematics of zebra mussels and related species. Molecular Ecology.  15:1021-1031.

May GE, GW Gelembiuk, V Panov, M Orlova, CE Lee.  2006.  Molecular ecology of zebra mussel invasions. Molecular Ecology.  15:1033-1050.

Peyer SM, AJ McCarthy, CE Lee. 2009. Zebra mussels anchor faster and tighter than quagga mussels in flow. Journal of Experimental Biology. 212:2027-2036.

Peyer SM, JC Hermanson, CE Lee.  2010.  Developmental plasticity of shell morphology in quagga mussels from shallow and deep water habitats of the Great Lakes. Journal of Experimental Biology. 213:2602-2609.

Peyer SM, JC Hermanson, CE Lee.  2011.  Effects of shell morphology on mechanics of zebra and quagga mussel locomotion. Journal of Experimental Biology. 214:2226-2236.