The behavioural ecology of the island fox (<i>Urocyon littoralis</i>)

Roemer, Gary W.; Smith, Deborah A.; Garcelon, David K.; Wayne, Robert K.

doi:10.1017/s0952836901001066

Cited by 127 publications

(150 citation statements)

References 63 publications

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“…Cervus elaphus; Clutton-Brock et al 1982) or when individuals within a group are dispersed while foraging, so that breeding females are frequently out of sight of resident males (e.g. Urocyon littoralis; Roemer et al 2001;Clutton-Brock & Isvaran 2006).…”

Section: Discussion (A) Variation In Egpmentioning

confidence: 99%

Ecological correlates of extra-group paternity in mammals

2006

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Extra-group paternity (EGP) can form an important part of the mating system in birds and mammals. However, our present understanding of its extent and ecology comes primarily from birds. Here, we use data from 26 species and phylogenetic comparative methods to explore interspecific variation in EGP in mammals and test prominent ecological hypotheses for this variation. We found extensive EGP (46% of species showed more than 20% EGP), indicating that EGP is likely to play an important role in the mating system and the dynamics of sexual selection in mammals. Variation in EGP was most closely correlated with the length of the mating season. As the length of the mating season increased, EGP declined, suggesting that it is increasingly difficult for males to monopolize their social mates when mating seasons are short and overlap among females in oestrus is likely to be high. EGP was secondarily correlated with the number of females in a breeding group, consistent with the idea that as female clustering increases, males are less able to monopolize individual females. Finally, EGP was not related to social mating system, suggesting that the opportunities for the extra-group fertilizations and the payoffs involved do not consistently vary with social mating system.

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Section: Discussion (A) Variation In Egpmentioning

confidence: 99%

Ecological correlates of extra-group paternity in mammals

2006

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“…Island foxes have tested positive for canine pathogens (11), and a recent canine distemper epidemic has decimated the Santa Catalina Island population (12). Further, because the island fox avoids mating with close kin and discriminates between kin and non-kin in territorial encounters (13), monomorphism at the MHC may influence the selectivity of mate choice and the degree of territoriality. To determine whether MHC variation has been maintained by natural selection despite the intense genetic drift implied by the genetic monomorphism of neutral genetic markers, we assess genetic variability at two class II MHC genes (DRB and DQB) and three class II MHC-linked microsatellite loci.…”

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confidence: 99%

High MHC diversity maintained by balancing selection in an otherwise genetically monomorphic mammal

Aguilar

Roemer

Debenham

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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The San Nicolas Island fox (Urocyon littoralis dickeyi) is genetically the most monomorphic sexually reproducing animal population yet reported and has no variation in hypervariable genetic markers. Such low levels of variation imply lower resistance to pathogens, reduced fitness, and problems in distinguishing kin from non-kin. In vertebrates, the MHC contains genes that influence disease resistance and kin recognition and may be under intense balancing selection in some populations. Hence, genetic variation at the MHC might persist despite the extreme monomorphism shown by neutral markers. We examine variation of five loci within the MHC of San Nicolas Island foxes and find remarkably high levels of variation. Further, we show by simulation that genetic monomorphism at neutral loci and high MHC variation could arise only through an extreme population bottleneck of <10 individuals, Ϸ10 -20 generations ago, accompanied by unprecedented selection coefficients of >0.5 on MHC loci. These results support the importance of balancing selection as a mechanism to maintain variation in natural populations and expose the difficulty of using neutral markers as surrogates for variation in fitness-related loci.T he island fox (Urocyon littoralis) is an endemic North American canid that inhabits six of the eight Channel Islands off the coast of southern California (Fig. 1). As suggested by the archeological record and molecular genetic data, foxes colonized the three northern Channel Islands (San Miguel, Santa Rosa, and Santa Cruz) Ϸ16,000 years ago and, subsequently, were transported by Native Americans to the three southern Channel Islands (San Nicolas, Santa Catalina, and San Clemente) 800 to 4,300 years ago (1-4) ( Fig. 1). Effective population size varies with island area and ranges from Ͻ200 to Ϸ1,000 individuals (Table 1). Levels of genetic variation reflect population size and colonization history, with the San Nicolas Island population having the second smallest effective population size and a recent colonization history (4) ( Fig. 1 and Table 1). No variation has been discovered for any of four independent genetic marker classes in the San Nicolas Island population, including supposedly neutral hypervariable microsatellite loci (5) and multilocus fingerprints (2), for which the probability of genetic identity is commonly Ͻ1 in several million (6). Recently, because of dramatic declines, populations on the three Northern Islands and Santa Catalina Island have been proposed for listing under the U.S. Endangered Species Act (7).The MHC contains the most variable set of coding genes in vertebrates, with as many as 349 alleles described for a single locus (8) and heterozygosity values that generally exceed those predicted by neutrality (9). Class I and II MHC molecules are responsible for the presentation to T cells of intracellular (endogenous) and extracellular (exogenous) peptides, respectively (10). High levels of heterozygosity at the MHC may be maintained by balancing selection through pathogen-mediated selection, ...

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“…Given the August flight time (near the end of the dry season in California), this is likely a reflection of environmental B neighborhood size for medium height NDVI model. C average home range of island fox (Roemer et al 2001). D maximum documented foraging distance of island scrub-jay (Atwood 1980).…”

Section: The Importance Of Environmental Conditionsmentioning

confidence: 99%

“…The average home range of the island fox has been reported as 55 ha (or a circle with radius 418 m; Fig. 5c), but it varies from 15 to 87 ha (219-526 m radius; Roemer et al 2001). Berries are a common part of its diet (Crooks and Van Vuren 1995), and like other fox species, it marks its territory with scat, making the island fox an important dispersal agent for fruiting plants.…”

Section: Spatial Autocorrelationmentioning

confidence: 99%

Linking vegetation patterns to environmental gradients and human impacts in a mediterranean-type island ecosystem

2014

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Vegetation patterns at the landscape scale are shaped by myriad processes and historical events, and understanding the relative importance of these processes aids in predicting current and future plant distributions. To quantify the influence of different environmental and anthropogenic patterns on observed vegetation patterns, we used simultaneous autoregressive modeling to analyze data collected by the Carnegie Airborne Observatory over Santa Cruz Island (SCI; California, USA). SCI is a large continental island, and its limited suite of species and well documented land use history allowed us to consider many potential determinants of vegetation patterns, such as topography, substrate, and historical grazing intensity. As a metric of vegetation heterogeneity, we used the normalized difference vegetation index (NDVI) stratified into three vegetation height classes using LiDAR (short, medium, and tall). In the SAR models topography and substrate type were important controls, together explaining 8-15 % of the total variation in NDVI, but historical grazing and spatial autocorrelation were also key components of the models, together explaining 17-21 % of the variation in NDVI. Optimal spatial autocorrelation distances in the short and medium height vegetation models (600-700 m) were similar to the home range sizes of two crucial seed dispersers on the island-the island fox (Urocyon littoralis santacruzae) and the island scrub-jay (Aphelocoma insularis)-suggesting that these animals may be important drivers of the island's vegetation patterns. This study highlights the importance of dynamic processes like dispersal limitation and disturbance history in determining presentday vegetation patterns.

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The behavioural ecology of the island fox (Urocyon littoralis)

Cited by 127 publications

References 63 publications

Ecological correlates of extra-group paternity in mammals

Ecological correlates of extra-group paternity in mammals

High MHC diversity maintained by balancing selection in an otherwise genetically monomorphic mammal

Linking vegetation patterns to environmental gradients and human impacts in a mediterranean-type island ecosystem

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