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SEX-BIASED PARASITISM AND THE REPRODUCTIVE COSTS OF PARASITES IN A SOCIAL AFRICAN GROUND SQUIRREL
Title
SEX-BIASED PARASITISM AND THE REPRODUCTIVE COSTS OF PARASITES IN A SOCIAL AFRICAN GROUND SQUIRREL.
Creator
Hillegass, Melissa, Waterman, Jane, University of Central Florida
Abstract / Description
Vertebrate males frequently carry higher numbers of parasites than females. This bias in parasite loads could be a consequence of sexual selection. Grouping species are also assumed to be afflicted with larger numbers of parasites than solitary animals and associated costs of this parasitism could vary with group size or structure. I examined sex-biased parasitism and the influence of group size on parasite loads in Cape ground squirrels (Xerus inauris), a highly social species that occurs in...
Show moreVertebrate males frequently carry higher numbers of parasites than females. This bias in parasite loads could be a consequence of sexual selection. Grouping species are also assumed to be afflicted with larger numbers of parasites than solitary animals and associated costs of this parasitism could vary with group size or structure. I examined sex-biased parasitism and the influence of group size on parasite loads in Cape ground squirrels (Xerus inauris), a highly social species that occurs in the arid regions of southern Africa. Males carried three times as many ectoparasites as females, but females harbored nearly three times more endoparasites than males. Amount of time spent (per hour) autogrooming was similar between males and females, but amount time spent allogrooming by adult female was over eleven times that of adult males. Longer allogrooming of group members could be decreasing the numbers of ectoparasites of group members and ultimately the group. Males infrequently give or receive allogrooming and travel in very large home ranges, potentially increasing their exposure to ectoparasites. However, movement throughout a large home range may result in males foraging in areas with lower densities of fecal pellets, which could explain the lower endoparasite loads observed in males. When I considered the age class of group members, female age classes were similarly parasitized but male age classes were not. Sub-adult males carried similar ectoparasite loads to adult males and similar endoparasite loads to adult females. This result is of particular interest because sub-adult males are becoming scrotal but typically remain in the group until adulthood. Sexual selection does appear to influence parasite loads in this species, and parasite removal or avoidance potentially mitigates individual parasite loads and their associated costs. Parasites can be detrimental to the health, longevity, and reproduction of their hosts, but these costs are rarely quantified. I removed ectoparasites and endoparasites from Cape ground squirrels for three months and evaluated changes in female body mass, reproduction, burrow use, and grooming in response to parasite removal. Female body mass did not increase with parasite removal, but reproductive success (per capita offspring raised to emergence) increased nearly four-fold, while allogrooming by treated females decreased. Since breeding is highest in the late winter dry season when fewer resources are available, the impact of parasites may be highest during this season. Lactation and gestation are the most physiological stressful processes that females undergo, and the dramatic increase in reproductive success in treated females suggests that these females are able to allocate more resources to reproduction than females afflicted with parasites. These results suggest that studies investigating reproduction and fecundity must consider the vulnerability of the host to parasite infection and the potential impact on reproductive success.
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Date Issued
2007
Identifier
CFE0001958, ucf:47455
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001958
THE INFLUENCE OF SEXUAL SELECTION ON BEHAVIORAL AND PHYSIOLOGICAL MECHANISMS UNDERLYING REPRODUCTIVE SUCCESS IN MALE CAPE GROUND SQUIRRELS (XERUS INAURIS)
Title
THE INFLUENCE OF SEXUAL SELECTION ON BEHAVIORAL AND PHYSIOLOGICAL MECHANISMS UNDERLYING REPRODUCTIVE SUCCESS IN MALE CAPE GROUND SQUIRRELS (XERUS INAURIS).
Creator
Manjerovic, Mary, Waterman, Jane, University of Central Florida
Abstract / Description
Sexual selection is considered a powerful evolutionary force responsible for the enormous diversity found in reproductive morphology, physiology, and behavior. I addressed questions related to selection in the Cape ground squirrel (Xerus inauris), a species characterized as highly social and promiscuous. These attributes often are responsible for variance in male reproductive success and as such, sexual selection theory predicts increased opportunity for sexual selection. I confirm that the...
Show moreSexual selection is considered a powerful evolutionary force responsible for the enormous diversity found in reproductive morphology, physiology, and behavior. I addressed questions related to selection in the Cape ground squirrel (Xerus inauris), a species characterized as highly social and promiscuous. These attributes often are responsible for variance in male reproductive success and as such, sexual selection theory predicts increased opportunity for sexual selection. I confirm that the predominant mechanism underlying genital evolution and competition for paternity in X. inauris is sperm competition. I find evidence that investment in sperm competition is costly and may reflect immunocompetence. I quantify reproductive success as it relates to alternative male tactics and female resource distribution. I find that male X. inauris alternative reproductive tactics differ within and across populations most likely due to differences in female resource distribution. In areas where females are evenly distributed, dispersed males encounter more estrous females, and therefore have increased breeding opportunities. However, the decision to remain natal does not preclude reproduction. I determine that these tactics are most likely conditional with equal fitness payoffs. Males, regardless of tactic, invest more in post-copulatory competition (e.g. sperm competition, copulatory plugs) than males within a population with a clustered distribution of breeding females. In the latter area, males form dominance hierarchies that affect copulatory success and lead to greater skews in reproduction among males. Both sites have evidence of a highly skewed variance in reproduction and intense sexual selective pressure. My results suggest these populations have increased opportunities for selection but that different mechanisms of intrasexual competition may result in rapid evolutionary change within this species.
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Date Issued
2010
Identifier
CFE0003400, ucf:48402
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003400
Reproductive life history and signal evolution in a multi-species assemblage of electric fish
Title
Reproductive life history and signal evolution in a multi-species assemblage of electric fish.
Creator
Waddell, Joseph, Crampton, William, Fedorka, Kenneth, Quintana-Ascencio, Pedro, Stoddard, Philip, University of Central Florida
Abstract / Description
Animals that co-occur in sympatry with multiple closely-related species use reproductive mate attraction signals not only to assess the quality of a potential conspecific mate (sexual selection), but also to discriminate conspecifics from heterospecifics (species recognition). However, the extent to which sexual selection and species recognition may interact, or even conflict, is poorly known. Neotropical electric fish offer unrivaled opportunities for understanding this problem. They...
Show moreAnimals that co-occur in sympatry with multiple closely-related species use reproductive mate attraction signals not only to assess the quality of a potential conspecific mate (sexual selection), but also to discriminate conspecifics from heterospecifics (species recognition). However, the extent to which sexual selection and species recognition may interact, or even conflict, is poorly known. Neotropical electric fish offer unrivaled opportunities for understanding this problem. They generate simple, stereotyped mate attraction signals that are easy to record and quantify, and that are well-understood from the neurobiological perspective. Additionally, they live in electrically-crowded environments, where multiple congeners live and reproduce in close proximity. This dissertation reports an investigation of electric signal diversity and reproductive life history in a nine-species assemblage of the electric fish genus Brachyhypopomus from the upper Amazon. A year-long quantitative sampling program yielded a library of electric signal recordings from (>)3,000 individuals and an accompanying collection of preserved specimens from which suites of informative life history traits were measured. These data were used to understand basic reproductive biology, and to describe sexually dimorphic and interspecific diversity in electric signals. By integrating approaches from ecology, physiology, and evolutionary biology, novel perspectives are provided on: 1. how sexual selection and species recognition interact to shape signal diversity and the occupation of signal space in multi-species animal communities; 2. how extreme seasonal variation in Amazonian ecosystems influences trade-offs in the allocation of reproductive resources (-) including mate attraction signals, and; 3. how environmental variation shapes general life-history traits in a diverse tropical animal assemblage.
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Date Issued
2017
Identifier
CFE0006925, ucf:51689
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006925