conservation.arizona.edu - round-tailed ground squirrels

Munroe, K.E., and J.L. Koprowski. 2011. Sociality, Bateman’s gradients and the polygynandrous genetic mating system of round-tailed ground squirrels (Xerospermophilus tereticaudus). Behavioral Ecology and Sociobiology. 65: 1811-1824.

thackerk1 — Tue, 23 Jul 2019 23:45:01 +0000

Authors

Karen E. Munroe

John L. Koprowski

Historically, most mammals have been classified as polygynous; although recent molecular evidence suggests that many mammals may be polygynandrous, particularly the ground-dwelling sciurids. We genotyped 351 round-tailed ground squirrels (Xerospermophilus tereticaudus) using seven microsatellite loci to determine paternity in 31 litters from 2004 to 2007. Polygyny was evident in all years except in 2007, when the population size was reduced. Multiple paternity occurred in the majority of litters (55%) with 2.5±0.26 sires/litter (n=31). Forty-nine percent of resident males (n = 114) sired offspring, and of males that sired offspring (n=56) 27% sired young in multiple litters in a single breeding season. Litter size was positively correlated with the number of sires. Through an indirect analysis of paternity, we found 21 litters (68%) with an average relatedness of 0.5 or less. Males had a greater opportunity for sexual selection (Is = 1.60) than females (Is = 0.40); Bateman’s gradient was also greater in males (1.07 ± 0.04, n = 56) than females (0.82 ± 0.08, n = 31). The mating system in round-tailed ground squirrels defined through genetic analyses and Bateman’s gradients is polygynandrous compared to the previously suggested polygynous mating system as established by behavioral observations and fits within the predictions of the ground squirrel sociality models. Upon evaluating the predictions of the sociality models among sciurid species, we found a negative relationship between the level of sociality with litter size and the average percentage of multiple paternity within a litter. Thus, recent genetic information and reclassification of mating systems support the predictions of the ground-dwelling squirrel sociality models.

Additional Information

Sociality, Bateman’s gradients, and the polygynandrous genetic mating system of round-tailed ground squirrels (Xerospermophilus

Date of publication:

2011

Topics

round-tailed ground squirrels

sociality

Arizona

polygynandry

multiple paternity

microsatellites

parentage analysis

Munroe, K.E., and J.L. Koprowski. 2012. Presence of copulatory plugs in round-tailed ground squirrels (Xerospermophilus tereticaudus). Southwestern Naturalist. 57: 208-210.

thackerk1 — Tue, 23 Jul 2019 23:43:38 +0000

Authors

Karen E. Munroe

John L. Koprowski

Sperm competition, where sperm from more than one male competes to fertilize eggs within the reproductive tract of a female, is prevalent in mammals. In rodents, this competition often has led to copulatory plugs, a passive defense against further sperm competition. Copulatory plugs have been reported in many species of sciurids; however, not in round-tailed ground squirrels (Xerospermophilus tereticaudus). Here we report two observations of copulatory plugs in round-tailed ground squirrels and suggest they represent an indirect form of mate guarding in affording males a chance to seek additional mating opportunities as seen in other species of rodents.

Additional Information

COPULATORY PLUGS OF ROUND-TAILED GROUND SQUIRRELS (XEROSPERMOPHILUS TERETICAUDUS)

Date of publication:

2012

Topics

round-tailed ground squirrels

copulatory plugs

Munroe, K. E., and J. L. Koprowski. 2014. Levels of social behaviors and genetic structure in a population of round-tailed ground squirrels (Xerospermophilus tereticaudus). Behavioral Ecology and Sociobiology 68:629-638.

thackerk1 — Tue, 23 Jul 2019 23:41:49 +0000

Authors

Karen E. Munroe

John L. Koprowski

Ground-dwelling sciurids exhibit a continuum of sociality and several models predict levels of sociality within this taxon. Models of ground squirrel sociality predict round- tailed ground squirrels (Xerospermophilus tereticaudus) to be solitary; however, previous behavioral studies suggest round-tailed ground squirrels have a matrilineal social structure. To resolve this discrepancy, we combined behavioral observations with genetic analyses of population structure. We assessed levels of agonistic and amicable behaviors combined with fine-scale population genetic structure of round-tailed ground squirrels in a multi-year study in AZ. Only 45 agonistic and 40 amicable interactions were observed between adults in over 137 h of observations. Overall rates of agonistic or amicable interactions between adults were low (≤0.69/h), with no relationship between relatedness of individuals and rates of either amicable or agonistic interactions. Interactions between juvenile littermates were predominantly amicable. Population substructure was not evident with Bayesian analyses, global or pairwise FST values; average relatedness among females was not different from males. However, in 2006, the year after a population reduction through targeted animal elimination, a population bottleneck was detected within at least five of seven loci. Contrary to previous behavioral studies, this population of round-tailed ground squirrels, although aggregated spatially, did not exhibit high levels of social behavior nor subpopulation genetic structure. Analyses of the genetic relationships and sociality along a continuum, particularly within aggregates of individuals, may lead to insights into the origin and maintenance of social behaviors by elucidating the mechanisms by which aggregates with intermediate social levels are formed and maintained.

Additional Information

Levels of social behaviors and genetic structure in a population of round-tailed ground squirrels (Xerospermophilus tereticaudus

Date of publication:

2014

Topics

round-tailed ground squirrels

Arizona

bottleneck

sociality

microsatellites

sciuridae