Jones P.C.,Northern Illinois University |
King R.B.,Northern Illinois University |
Bailey R.L.,Michigan State University |
Bieser N.D.,Indiana University - Purdue University Fort Wayne |
And 31 more authors.
Journal of Wildlife Management | Year: 2012
Decisions affecting wildlife management and conservation policy of imperiled species are often aided by population models. Reliable population models require accurate estimates of vital rates and an understanding of how vital rates vary geographically. The eastern massasauga (Sistrurus catenatus catenatus) is a rattlesnake species found in the Great Lakes region of North America. Populations of the eastern massasauga are fragmented and only a few areas harbor multiple, sizable populations. Eastern massasauga research has typically focused on single populations or local metapopulations but results suggest that demographic parameters vary geographically. We used 21 radiotelemetry datasets comprising 499 telemetered snakes from 16 distinct locations throughout the range of the eastern massasauga to characterize geographic patterns of adult survival using the known-fate model in Program MARK. Annual adult survival ranged from 0.35 to 0.95 (mean = 0.67) and increased along a southwest to northeast geographic axis. Further analysis of 6 datasets indicated no consistent difference in survival between males and females. Our results provide a better understanding of the relationship between survivorship and geography for the eastern massasauga and suggest that such variation should be incorporated into population models as well as local and regional management plans. © 2012 The Wildlife Society. Copyright © The Wildlife Society, 2012.
Richter S.C.,Eastern Kentucky University |
Jackson J.A.,Eastern Kentucky University |
Hinderliter M.,Camp Shelby Field Office |
Epperson D.,Southern Illinois University at Edwardsville |
And 2 more authors.
Herpetologica | Year: 2011
We conducted a genetic study of the largest cluster of US federally threatened Gopher Tortoise (Gopherus polyphemus) colonies. Our objectives were to (1) identify genetic variation within and among colonies across the landscape; (2) determine which factors are important in affecting genetic variation, including land use, habitat quality, and population size; and (3) determine whether genetic partitioning among populations exists and how this relates to (a) geographic distance between sites, (b) Gopher Tortoise natural history and spatial ecology, and (c) land-use history. We studied genetic variability of nine microsatellite DNA loci for 340 adult tortoises from 34 colonies separated by 1.345.1 km across a 56,000-ha military installation. Overall genetic variation was low across the landscape and within colonies. Observed heterozygosity (HO) of tortoise colonies was 49% and allelic richness was 52% of that found in populations located in the eastern portion of the species distribution where habitat is naturally more continuous. Our single colony with highest genetic variation had HO that was 57% and allelic richness that was 60% of eastern colonies. Genetic variation was greatest in sites with suitable habitat. We found weak to no genetic structure across the 45-km landscape (FST â€Š=â€Š 0.031; DST â€Š=â€Š 0.006) and evidence for only one genetic group (K). Although landscape reconfiguration to create sites for military activity has redistributed tortoise colonies and home ranges, we concluded that weak population structure is natural across our study area. Comparison to similar results from a cluster of connected eastern colonies suggests this is a general characteristic of tortoises across large, continuous landscapes and that populations are composed of multiple colonies across the landscape and are naturally large in spatial extent. To alleviate the tortoisehuman land use conflict on Camp Shelby, Mississippi, USA and to ensure these created areas continue to benefit tortoises in the long term, maintenance of forest habitat surrounding these created open areas is required. We recommend managing tortoises at Camp Shelby as one unit. © 2011 The Herpetologists' League, Inc.
Yager L.Y.,Camp Shelby Field Office |
Miller D.L.,University of West Florida |
Jones J.,Mississippi State University
Invasive Plant Science and Management | Year: 2011
Cogongrass invades forests through rhizomatous growth and wind-dispersed seeds. Increased density and abundance of woody vegetation along forest edges may strengthen biotic resistance to invasion by creating a vegetative barrier to dispersal, growth, or establishment of cogongrass. We evaluated differences in dispersal of cogongrass spikelets experimentally released from road edges into tallgrass-dominated and shrub-encroached longleaf pine forests (Pinus palustris). Average maximum dispersal distances were greater in the pine-tallgrass forest (17.3 m) compared to the pine-shrub forest association (9.4 m). Spikelets were more likely to be intercepted by vegetation in pine-shrub forests compared to pine-tallgrass forests. Results suggest that dense woody vegetation along forest edges will slow spread from wind-dispersed cogongrass seeds. © Weed Science Society of America 2011.