Spartanburg, United States
Spartanburg, United States

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Levine B.A.,University of Arkansas | Smith C.F.,Wofford College | Smith C.F.,The Copperhead Institute | Schuett G.W.,The Copperhead Institute | And 6 more authors.
Biological Journal of the Linnean Society | Year: 2015

Assessment of sexual selection in organisms with cryptic life histories is challenging, although accurate parentage assignments using genotypic markers, combined with behavioural observations and a method to account for open population bias, allow for robust estimation of metrics. In the present study, we employed 22 tetranucleotide microsatellite DNA loci to interpret mating and reproductive success in a population of Copperhead (Viperidae, Agkistrodon contortrix) in Connecticut, USA. We sampled DNA from 114 adults (56 males, 58 females) and 137 neonates from known mothers to quantify Bateman gradients (βss), as well as sex-specific opportunities for selection (I) and sexual selection (Is). We also estimated selection on male size [snout-to-vent length (SVL)], a trait important for successful combat and subsequent copulations. Estimates of male I and Is differed significantly from those of females when estimated with four different methods and only males had a significant Bateman gradient. As predicted, male reproductive success was positively correlated with increasing SVL. These results contrast with those derived in another study investigating the same population but based solely on observational data and without correction for open population bias. We thus argue that molecular approaches to quantifying reproductive success and strength of sexual selection provide more accurate results than do behavioural observations alone. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 436-445.

Schuett G.W.,Georgia State University | Schuett G.W.,The Copperhead Institute | Repp R.A.,National Optical Astronomy Observatory | Amarello M.,Arizona State University | And 2 more authors.
Journal of Zoology | Year: 2013

For various reasons, reduction or cessation of feeding (anorexia) can occur in either sex during periods of reproduction among vertebrates, from cichlids to elephant seals. Anorexia is commonly associated with gestation in snakes. Using radiotelemetry, we investigated the feeding and spatial ecology of a live-bearing viperid snake, the western diamond-backed rattlesnakes (Crotalus atrox). Specifically, from 2001 to 2010, we determined the feeding frequency and home range size of adult females (n = 27) during the active season (March-October) in a population from the Sonoran Desert of Arizona. We addressed a central hypothesis: Do hunting and feeding occur throughout pregnancy? Also, we tested a corollary hypothesis: Does pregnancy influence home range size? We documented hunting and feeding from March to October and during pregnancy (June to mid-September). Feeding frequency was significantly greater in late pregnancy, a result that is in sharp contrast to most other large-bodied vipers. Furthermore, home range sizes in gestating subjects did not differ from those in nonreproductive years. Births occurred from mid-August to mid-September and mean litter size was 3.4. Frequent feeding in C. atrox during gestation unquestionably provides energy and nutrients to the mother, which is likely important for survival, but such food consumption does not imply that nutrients are used by the fetuses. There is, however, recent evidence in other snakes, including a pitviper, that amino acids are transferred to fetuses. Feeding during pregnancy in C. atrox may be important for both income and capital mode reproduction. Hunting and feeding throughout gestation might be accomplished by having relatively small litters not burdened by a body cavity filled with fetuses. Reduction in litter size may thus be a life-history (fecundity) trade-off that permits females to survive and maintain pregnancy in regions where drought and high temperatures are often extreme and chronic. © 2012 The Zoological Society of London.

Booth W.,University of Tulsa | Booth W.,The Copperhead Institute | Schuett G.W.,The Copperhead Institute | Schuett G.W.,Georgia State University | And 6 more authors.
Biological Journal of the Linnean Society | Year: 2014

In vertebrates, facultative parthenogenesis (i.e. asexual reproduction by a sexually reproducing species) has been documented in four diverse taxonomic groups, namely sharks, birds, lizards, and snakes. With a single exception, the mode is terminal fusion automixis, where the second polar body fuses with the nucleus of the gamete, restoring diploidy and triggering cell division. The deviating case involves a report of a captive Burmese python (Python bivittatus), a giant Asiatic species common in zoological gardens and the pet trade. Although terminal fusion automixis produces half-clones of the mother, under this unique case in P.bivittatus, the foetuses were reported as full clones. This conclusion is an apparent anomaly with respect to the mechanism of facultative parthenogenesis reported in all other snakes. In the present study, using genotyping methods, we analyze facultative parthenogenesis in two other species of pythonids and report results that challenge the abovementioned conclusions regarding clonality. Specifically, we report new findings comparable to those reported in other primitive snakes (namely boids), which support the hypothesis of terminal fusion automixis as the mode of facultative parthenogenesis. Furthermore, in light of our new data, we re-examine the previous report of facultative parthenogenesis in the Burmese python and suggest an intriguing alternative explanation for the earlier findings.© 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 461-468.

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