Metapopulation structure, population trends, and status of Florida Grasshopper Sparrows

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Abstract:

ABSTRACT. 

The federally Endangered Florida Grasshopper Sparrow (FGSP, Ammodramus savannarum floridanus) is endemic to dry prairie habitat in central Florida and is currently only found at three public management areas (Avon Park Air Force Range, APAFR; Kissimmee Prairie Preserve State Park, KPPSP; and Three Lakes Wildlife Management Area, TLWMA). We analyzed long-term (1991–2008) point-count data to compare population trends of FGSPs at these management areas to determine if they function as independent populations by using Spearman's rank correlation to test for independence between annual trends. We also examined banding and resighting data to infer metapopulation structure. Populations fluctuated across years at all three sites, declining significantly at APAFR (rs=−0.89, P < 0.001, N= 13) and KPPSP (rs=−0.78, P= 0.004, N= 11) and remaining stable at TLWMA (rs= 0.19, P= 0.46, N= 17). Population trends among the three management areas appeared independent (absolute value of rs≤ 0.50, P≥ 0.12). Previous studies indicated that sparrows in the three areas were not genetically differentiated, and two cases of dispersal between APAFR and KPPSP have been documented. However, dispersal rates among areas appear to be too low to influence demographic dynamics within individual areas. Within APAFR, FGSPs are aggregated into three spatially distinct habitat patches previously considered separate populations, but dispersal among these patches is more frequent than previously reported and population trends among these patches are correlated (rs≥ 0.91, P < 0.001). These patterns suggest that a single metapopulation of FGSPs exists consisting of three distinct populations (APAFR, KPPSP, and TLWMA), and the spatially distinct aggregations at APAFR constitute a single population using several habitat patches. The population at APAFR is at risk of extirpation, and immediate action is needed if that population is to recover. Taking broader metapopulation dynamics into account will be useful for guiding management efforts aimed at conserving the FGSP in the broader central Florida landscape.

Keywords: Ammodramus savannarum floridanus; Florida dry prairie; dispersal; endangered species; population monitoring

Document Type: Research Article

DOI: http://dx.doi.org/10.1111/j.1557-9263.2010.00282.x

Affiliations: 1: Archbold Biological Station, Avian Ecology Lab, P.O. Box 2057, Lake Placid, Florida 33862, USA 2: Florida Fish and Wildlife Conservation Commission, 1105 SW Williston Road, Gainesville, Florida 32601, USA 3: Florida Fish and Wildlife Conservation Commission, Three Lakes Wildlife Management Area, 1231 Prairie Lakes Road, Kenansville, Florida 34739, USA 4: Florida Department of Environmental Protection, Division of Recreation and Parks, Kissimmee Prairie Preserve State Park, 33104 NW 192nd Avenue, Okeechobee, Florida 34972, USA

Publication date: September 1, 2010

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