English Journal

Snake co-occurrence patterns are best explained by habitat and hypothesized effects of interspecific interactions.

Steen DA, McClure CJ, Brock JC, Craig Rudolph D, Pierce JB, Lee JR, Jeffrey Humphries W, Gregory BB, Sutton WB, Smith LL, Baxley DL, Stevenson DJ, Guyer C.Author information Joseph W. Jones Ecological Research Center, 3988 Jones Center Drive, Newton, GA, 39870, USA; Department of Biological Sciences, Auburn University, Auburn, AL, 36849, USA.AbstractSnakes often occur in species-rich assemblages, and sympatry is thought to be facilitated primarily by low diet overlap, not interspecific interactions. We selected, a priori, three species pairs consisting of species that are morphologically and taxonomically similar and may therefore be likely to engage in interspecific, consumptive competition. We then examined a large-scale database of snake detection/nondetection data and used occupancy modelling to determine whether these species occur together more or less frequently than expected by chance while accounting for variation in detection probability among species and incorporating important habitat categories in the models. For some snakes, we obtained evidence that the probabilities that habitat patches are used are influenced by the presence of potentially competing congeneric species. Specifically, timber rattlesnakes (Crotalus horridus) were less likely than expected by chance to use areas that also contained eastern diamond-backed rattlesnakes (Crotalus adamanteus) when the proportion of evergreen forest was relatively high. Otherwise, they occurred together more often than expected by chance. Complex relationships were revealed between habitat use, detection probabilities and occupancy probabilities of North American racers (Coluber constrictor) and coachwhips (Coluber flagellum) that indicated the probability of competitive exclusion increased with increasing area of grassland habitat, although there was some model uncertainty. Cornsnakes (Pantherophis guttatus or Pantherophis slowinskii) and ratsnakes (Pantherophis alleghaniensis, Pantherophis spiloides, or Pantherophis obsoletus) exhibited differences in habitat selection, but we obtained no evidence that patterns of use for this species pair were influenced by current interspecific interactions. Overall, our results are consistent with the hypothesis that competitive interactions influence snake assemblage composition; the strength of these effects was affected by landscape-scale habitat features. Furthermore, we suggest that current interspecific interactions may influence snake occupancy, challenging the paradigm that contemporary patterns of snake co-occurrence are largely a function of diet partitioning that arose over evolutionary time.
The Journal of animal ecology.J Anim Ecol.2014 Jan;83(1):286-95. doi: 10.1111/1365-2656.12121. Epub 2013 Sep 2.
Snakes often occur in species-rich assemblages, and sympatry is thought to be facilitated primarily by low diet overlap, not interspecific interactions. We selected, a priori, three species pairs consisting of species that are morphologically and taxonomically similar and may therefore be likely to
PMID 23998642

Determinants and repeatability of the specific dynamic response of the corn snake, Pantherophis guttatus.

Crocker-Buta S1, Secor SM2.Author information 1Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487-0344, USA.2Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487-0344, USA. Electronic address: ssecor@biology.as.ua.edu.AbstractIngesting, digesting, absorbing, and assimilating a meal are all energy consuming processes that accumulate to form the specific dynamic action (SDA) of the meal. Sensitive to digestive demand, SDA is theoretically fixed to a given meal size and type. In this study, we explore the effects of digestive demand by altering relative meal size on the postprandial metabolic profile and SDA of the corn snake, Pantherophis guttatus. We also examined the effects of body temperature on the SDA response while controlling for meal size and type and assessed whether these responses are highly repeatable under the same conditions. Additionally, the effects of body mass on SDA were investigated by feeding snakes of the same relative and absolute meal size. With increases in digestive demand (meals from 5% to 45% of body mass), P. guttatus responded with incremental increases in the postprandial peak in oxygen consumption (V˙ O2), the duration of the significantly elevated V˙ O2, and SDA. Body temperature had an observable impact on the postprandial metabolic profile, decreasing the duration and increasing the peak V˙ O2, however, body temperature did not significantly alter SDA. Regardless of temperature, and hence duration, snakes expended the same amount of energy in digesting a given meal. This was additionally borne out when testing the individual repeatability of the SDA response, individual P. guttatus exhibited nearly identical postprandial responses to the same meal. Over a 90-fold range in body mass, and fed meals equaling 25% of body mass, P. guttatus exhibited an isometric relationship between SDA and body mass. When fed a set 10-gram meal, snakes regardless of body size expended the same amount of energy on digestion and assimilation. Characteristically, P. guttatus experience a rapid postprandial increase in metabolic rate that peaks and gradually descends to prefeeding levels. The magnitude of that response (quantified as SDA) varies as a function of digestive demand (i.e., meal size); however, when demand is fixed, SDA is constant regardless of body temperature and body size.
Comparative biochemistry and physiology. Part A, Molecular & integrative physiology.Comp Biochem Physiol A Mol Integr Physiol.2013 Dec 17. pii: S1095-6433(13)00295-X. doi: 10.1016/j.cbpa.2013.12.008. [Epub ahead of print]
Ingesting, digesting, absorbing, and assimilating a meal are all energy consuming processes that accumulate to form the specific dynamic action (SDA) of the meal. Sensitive to digestive demand, SDA is theoretically fixed to a given meal size and type. In this study, we explore the effects of digesti
PMID 24361263

The standing pool of genomic structural variation in a natural population of Mimulus guttatus.

Flagel LE, Willis JH, Vision TJ.Author information Department of Biology, Duke University, Durham, NC, USA.AbstractMajor unresolved questions in evolutionary genetics include determining the contributions of different mutational sources to the total pool of genetic variation in a species, and understanding how these different forms of genetic variation interact with natural selection. Recent work has shown that structural variants (insertions, deletions, inversions and transpositions) are a major source of genetic variation, often out-numbering single nucleotide variants in terms of total bases affected. Despite the near ubiquity of structural variants, major questions about their interaction with natural selection remain. For example, how does the allele frequency spectrum of structural variants differ when compared to single nucleotide variants? How often do structural variants affect genes, and what are the consequences? To begin to address these questions, we have systematically identified and characterized a large set submicroscopic insertion and deletion (indel) variants (between 1 kb to 200 kb in length) among ten individuals from a single natural population of the plant species Mimulus guttatus. After extensive computational filtering, we focused on a set of 4,142 high-confidence indels that showed an experimental validation rate of 73%. All but one of these indels were < 200 kb. While the largest were generally at lower frequencies in the population, a surprising number of large indels are at intermediate frequencies. While indels overlapping with genes were much rarer than expected by chance, nearly 600 genes were affected by an indel. NBS-LRR defense response genes were the most enriched among the gene families affected. Most indels associated with genes were rare and appeared to be under purifying selection, though we do find four high-frequency derived insertion alleles that show signatures of recent positive selection.
Genome biology and evolution.Genome Biol Evol.2013 Dec 12. [Epub ahead of print]
Major unresolved questions in evolutionary genetics include determining the contributions of different mutational sources to the total pool of genetic variation in a species, and understanding how these different forms of genetic variation interact with natural selection. Recent work has shown that
PMID 24336482