Multiple Paternity and Breeding System in the Gopher Tortoise, Gopherus polyphemus

Department of Biology, University of South Florida, SCA 110, 4202 East Fowler Avenue, Tampa, FL 33620, USA.
Journal of Heredity (Impact Factor: 2.09). 03/2006; 97(2):150-7. DOI: 10.1093/jhered/esj017
Source: PubMed


Little is known about the reproductive behaviors and the actual outcomes of mating attempts in the gopher tortoise (Gopherus polyphemus). We examined the mating system and reproductive behaviors of a population of gopher tortoises in central Florida. Using
microsatellite markers, we assigned fathers to the offspring of seven clutches and determined that multiple fathers were present
in two of the seven clutches examined. We found that gopher tortoises exhibited a promiscuous mating system with larger males
fertilizing the majority of clutches. The advantage of larger males over smaller males in fertilizing females may be a result
of larger males winning access to females in aggressive bouts with other males or larger males may be more attractive to females.
Clutches produced by larger females tended to be sired by a single male, whereas clutches of smaller females tended to be
sired by multiple males.

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Available from: Henry Mushinsky, Apr 07, 2014
    • "Here, we evaluate population viability indirectly by examining the rates of behavioral interactions of tortoises at burrows occupied by females. One such rate, the rate at which males attempt to copulate with females, measures important aspects of reproduction that may affect opportunities for multiple paternity within clutches (Moon et al., 2006), fertility of females (Boglioli et al., 2003), or mating system (Tuberville et al., 2011). Because tortoises in low-density populations are widely dispersed, their mating opportunities may depend upon the ability of male tortoises to recall the location of burrows occupied by potential mates. "
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    ABSTRACT: Patterns of burrow size, tortoise size, home range size and overlap, movement distances, and mating rates were compared among six sites that differed in density of Gopher Tortoises. Burrow sizes differed among sites because tortoise size distributions differed among sites, but this was due principally to the unusually small size of animals on the Conecuh National Forest. A linear relationship between tortoise density and burrow density was documented from the six sites, suggesting that tortoises, on average, created 2.5 burrows per site or that the burrow-to-tortoise conversion factor for our sites was 0.40. The average distance from a burrow to its nearest three neighbors was greater for low-density sites than for high-density sites, indicating that animals probably were more isolated from each other on sites with low tortoise densities. Tortoise home ranges were larger in males than females, a feature documented in other studies of tortoise movements. Home range sizes were greatest for densities of approximately 0.4 tortoises/ha and decreased in size above and below this density. This suggests that animals moved to visit close neighbors in areas of high density, expanded movements to maintain contact with neighbors that became more widely dispersed as density decreased, and then restricted movements to a few close neighbors as density reached extremely low levels. Home range overlap increased linearly with increasing density, suggesting that opportunities for social interactions decreased with decreasing density. When tortoises moved between burrows, males moved longer distances than females and tortoises of both sexes moved shorter distances on high-density sites than did tortoises on low-density sites, suggesting greater movement costs for males than females and for tortoises on low-density sites. Males traveled up to 500 m to visit female burrows, but most movements were < 80 m. Median movement distances of males to visit females were negatively correlated with burrow density, suggesting that cost of male movements to find mates increased as population density decreased. Based upon patterns of 95% confidence limits, rates of mountings of female tortoises approached zero when females occupied burrows approximately 200 m from neighboring burrows. If burrows were uniformly distributed 200 m apart, then reproductive failure would be a statistically supportable outcome at a density of 0.3 burrows/ha (0.12 tortoises/ha). These values are similar to the values of 0.4 tortoises/ha (1.0 burrows/ha) that our data suggest is the density at which social structure associated with movements within home ranges are altered.
    No preview · Article · Dec 2012 · Herpetological Monographs
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    • "Parentage analysis of offspring from recently translocated gopher tortoises would provide valuable insight into the factors affecting mating success during the settling phase of reintroductions. Paternity data reported by Moon et al. (2006) for a naturallyoccurring population provide a basis of comparison for our results from the translocated population on St. Catherines Island, but additional parentage studies of both naturally-occurring and translocated tortoise populations are needed to fully characterize the potential factors influencing the mating system of translocated populations. Additionally, multi-year studies could reveal how mating system dynamics and individual reproductive success vary from year to year, by addressing the following questions: Do individual females consistently produce either singly-or multiplysired clutches? "
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    ABSTRACT: Population manipulations such as translocation are becoming increasingly important tools in the management of rare and declining species. Evaluating the effectiveness of such manipulations requires comprehensive monitoring of population processes, including dispersal, survivorship, and reproduction. We investigated the mating system of a translocated population of gopher tortoises (Gopherus polyphemus) established through multiple releases, which occurred primarily during 1987–1994. During 2006–2007, we sampled and genotyped 27 candidate males (candidate sires), 34 candidate females (candidate dams), and 121 offspring from 19 clutches at five polymorphic microsatellite loci to determine the relative frequency of multiple paternity and to estimate individual reproductive success. Multiple paternity was detected in 57% of clutches genotyped, and females of single-sire clutches and females of multiple-sire clutches were of similar size. Reproductive success varied among male tortoises, and successful sires were significantly larger than males to which no offspring were attributed. Among successful sires, previously established males sired a disproportionate number of the offspring sampled, despite being significantly smaller than subsequently released males. The high variance in individual reproductive success and the apparent reproductive advantage associated with prior residence observed in this gopher tortoise population has important implications for the design of future translocation projects.
    Full-text · Article · Jan 2011 · Biological Conservation
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    • "Little is known about the mating system of radiated tortoises, but it might actually be best described as both polygynous and polyandrous; both males and females court repeatedly over a breeding season, often with different partners (Leuteritz and Ravolanaivo 2005). Furthermore, multiple paternity is frequent in tortoises (e.g., Pearse and Avise 2001; Johnston et al. 2006; Moon et al. 2006), and females can store sperm and utilize it several years later to fertilize eggs (Kuchling 1999; Pearse and Avise 2001), creating a system where sperm competition and female choice might be as important as intramale competition in sexual selection. Even females that mate only once in a season could effectively be polyandrous because of longterm sperm storage (temporal polyandry). "
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    ABSTRACT: Dispersal is a major force in shaping the genetic structure and dynamics of species; thus, its understanding is critical in formulating appropriate conservation strategies. In many species, sexes do not face the same evolutionary pressures, and consequently dispersal is often asymmetrical between males and females. This is well documented in birds and mammals but has seldom been investigated in other taxa, including reptiles and, more specifically, nonmarine chelonians. In these species, nest-site fidelity observations are frequent but still remain to be associated with natal homing. Here, we tested for sex-biased dispersal in the radiated tortoise (Astrochelys radiata) from southern Madagascar. Using data from 13 microsatellite markers, we investigated patterns of relatedness between sexes in 2 populations. All Mantel tests indicated significant isolation by distance at the individual level in females but not in males. Furthermore, spatial autocorrelation analyses and 2 analytical approaches designed to assess general trends in sex-specific dispersal also supported male-biased dispersal. On the other hand, comparisons of overall genetic structure among sampling sites did not provide conclusive support for greater philopatry in females, but these tests may have low statistical power because of methodological and biological constraints. Radiated tortoises appear to be both polyandrous and polygynous, and evolutionary processes that may lead to a sex bias in dispersal are discussed with respect to tortoise breeding biology. Female natal homing is hypothesized as a key trait explaining greater female philopatry in A. radiata. These findings highlight the necessity of additional research on natal homing in tortoises, a behavioral trait with direct implications for conservation.
    Full-text · Article · Mar 2010 · The Journal of heredity
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