53-7 Countergradient variation in growth of spotted gar from different latitudes, with implications for conservation

Thursday, September 16, 2010: 10:20 AM
304 (Convention Center)
Solomon R. David , School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI
Richard Kik IV , Belle Isle Zoological Society
Michael J. Wiley, PhD , School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI
Edward S. Rutherford, PhD , NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI
James S. Diana, PhD , Fish Ecology, University of MIchigan School of Natural Resources and Environment, Ann Arbor, MI
The spotted gar (Lepisosteus oculatus) is one of seven extant members of the family Lepisosteidae and ranges from the southern Great Lakes region to the Gulf Coast.  The spotted gar has a disjoint distribution and is more common in the Mississippi River basin than the Great Lakes Region.  The Great Lakes basin population (peripheral) is poorly studied and may exhibit different life history traits from the Mississippi River basin population (core).  We hypothesized that the peripheral population of spotted gars exhibited a faster growth rate and capacity for growth than those from the core population due to countergradient variation, which compensates for shorter length of growing season at higher latitudes.  We reared young of the year spotted gars from both populations (N=60) in a common garden environment for 160 days to test for countergradient variation in growth.  Individual fish were fed ad libitum and weighed and measured weekly to estimate growth.  Results indicated gars from the peripheral population grew significantly larger and faster than those from core the population, suggesting countergradient variation in growth.  DNA and morphometric analyses suggested increased divergence between peripheral and core populations, providing a strong basis for further conservation efforts.  
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