Genetic structure of populations of the threatened eastern massasauga rattlesnake, Sistrurus c. catenatus: evidence from microsatellite DNA markers

Abstract

Throughout its distribution in North America, the threatened eastern massasauga rattlesnake (Sistrurus c. catenatus) persists in a series of habitat-isolated disjunct populations of varying size. Here, we use six microsatellite DNA loci to generate information on the degree of genetic differentiation between, and the levels of inbreeding within populations to understand how evolutionary processes operate in these populations and aid the development of conservation plans for this species. Samples were collected from 199 individuals from five populations in Ontario, New York and Ohio. Our results show that all sampled populations: (i) differ significantly in allele frequencies even though some populations are < 50 km apart, and may contain genetically distinct subpopulations < 2 km apart; (ii) have an average of 23% of alleles that are population specific; and (iii) have significant FIS values (mean overall FIS = 0.194) probably due to a combination of Wahlund effects resulting from fine-scale genetic differentiation within populations and the presence of null alleles. Our results imply that massasauga populations may be genetically structured on an extremely fine scale even within continuous populations, possibly due to limited dispersal. Additional information is needed to determine if dispersal and mating behaviour within populations can account for this structure and whether the observed differentiation is due to random processes such as drift or to local adaptation. From a conservation perspective, our results imply that these massasauga populations should be managed as demographically independent units and that each has high conservation value in terms of containing unique genetic variation.

Microsatellite genotyping from faeces of Lontra longicaudis from southern Brazil

“…Measures of genetic differentiation (I= 0.890; F ST = 0.059) showed that there was a moderate degree of population division between the Taim and the Vargas site. Similar and lower values of F ST , which showed significant population division, were also found in other species (see HARTL & CLARK, 1989;GIBBS et al, 1997;ESCORZA-TREVIÑO & DIZON, 2000;TRUJILLO et al, 2004;WURFF et al, 2005). A homogeneity χ 2 test confirmed the population division of L. longicaudis (P< 0.001; α'= 0.01) after a Bonferroni correction for multiple testing (RICE, 1988), and the Lut457 (χ 2 = 24.27; P< 0.001) and Lut715 e Hardy-Weinberg equilibrium; *significant at the level of α'= α/5 = 0.01 after Bonferroni correction for multiple tests (RICE, 1988) Genotyping at more than one locus was possible only in 81.5% of the scored samples, from which 37% were evaluated for more than three loci.…”

Microsatellite Markers to Determine Population Genetic Structure in the Golden Anchovy, Coilia dussumieri

“…Deviation from Hardy-Weinberg is usually attributed to null alleles (Gopalakrishnan et al 2004;Garcia de Leon et al 1995), selection (Garcia de Leon et al 1995), grouping of gene pools (Walhund effect; Gibbs et al 1997), inbreeding or nonrandom mating (Beaumont and Hoare 2003). Nine of the ten primer pairs in C. dussumieri indicated positive F IS values in different populations.…”

Behavioral and life history responses of eastern massasauga rattlesnakes (Sistrurus catenatus catenatus) to human disturbance

“…Similarly, human disturbance could affect the survival and dispersal of neonates, which in turn could affect population age and genetic structure and viability. Thus, it is interesting in this regard that the massasauga rattlesnake population in Killbear Provincial Park shows significant genetic structure over distances <2 km, indicating very restricted gene flow (Gibbs et al 1997). Whether human disturbance has contributed to this phenomenon is unknown, but the fact that the snakes respond to disturbance by restricting their movement makes this a possibility worth investigating.…”