... Keywords copulatory plugs; sperm competition; inbreeding avoidance. CorrespondenceJennifer C.... more ... Keywords copulatory plugs; sperm competition; inbreeding avoidance. CorrespondenceJennifer C. McCreight, Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA. Email: jmccreig@uw.edu Editor: Robert Knell ...
The collared peccary (Pecari tajacu) is a social species that recently has expanded its historica... more The collared peccary (Pecari tajacu) is a social species that recently has expanded its historical range, yet little is known of its dispersal behavior at the population or biogeographic level. We used autosomal and cytoplasmic markers to assess whether the genetic variation among 4 populations in Texas retains a signal of historically recent founding events. Genetic differentiation based on mitochondrial DNA (mtDNA) haplotype frequencies (F ST) among these 4 populations was substantial. The mtDNA haplotype mismatch distributions indicate that P. tajacu recently has expanded its range across Texas; however, microsatellite-based standard analyses of molecular variance (AMOVAs) and pairwise F ST estimates indicated little variation among populations, suggesting that dispersal is accomplished primarily by males. We also tested the alternative power of mtDNA haplotype or microsatellite genotype distribution patterns to detect a sex bias in instantaneous short-distance dispersal. Sex-specific hierarchical AMOVAs of mtDNA haplotype distributions (based on data from the most genetically diverse population) yielded significantly larger female-specific fixation index values compared to males, indicating a male instantaneous dispersal bias; however, variation in microsatellite frequency distribution was not partitioned in a sex-specific manner. Also, when sex-specific pairwise F ST /(1 2 F ST) among herds was regressed against the log of the distance between each pair of herds, we found no significant effect of distance for either sex and no sex-specific difference using other microsatellite-based analyses (mean sex-specific relatedness, r, or F ST). We conclude that sampling scale limits microsatellite-based methods of detecting instantaneous dispersal sex bias, especially when gene flow is substantial and microsatellite polymorphism is modest (,20 alleles/locus). These results indicate that mtDNA can be used to infer instantaneous dispersal behavior for both sexes in cases where microsatellites have proven insufficient.
INTRODUCTION Marler [1965, 1967, 19681 suggested that habitat differences influence both the moda... more INTRODUCTION Marler [1965, 1967, 19681 suggested that habitat differences influence both the modality of choice for communication and the expected complexity of signal reper-toires. Signal frequency, sound source height, and time of day all have since been shown to ...
Two opposing hypotheses concerning determinants of mangabey (Cercocebus albigena) ranging pattern... more Two opposing hypotheses concerning determinants of mangabey (Cercocebus albigena) ranging patterns have been advocated. One hypothesis suggests that ranging patterns of mangabeys are largely a response to fruit availability, while the other hypothesis advocates that concerns of fruit availability are supplemented or overridden by concerns of fecal contamination and that the risk of parasite infection, especially during dry weather, determines their pattern of range use. In this 9 month study of mangabeys in the Kanyawara study area of Kibale National Park, mangabeys moved longer distances during the wet season than during the dry season. There were no seasonal differences in group spread, number of 50 by 50 m quadrats used, or in quadrat overlap between sequential sample periods. Intensity of quadrat use was closely related to the number of fruiting trees/lianas in the quadrats, irrespective of season. These findings are consistent with the hypothesis that fruit availability is a main factor influencing mangabey ranging patterns. The results are not consistent with the hypothesis that mangabey ranging patterns largely reflect differential seasonal risk of parasite infection. Am.
Genes of the major histocompatibility complex (MHC) are exceptionally polymorphic due to the comb... more Genes of the major histocompatibility complex (MHC) are exceptionally polymorphic due to the combined effects of natural and sexual selection. Most research in wild populations has focused on the second exon of a single class II locus (DRB), but complete gene sequences can provide an illuminating backdrop for studies of intragenic selection, recombination, and organization. To this end, we characterized class II loci in the banner-tailed kangaroo rat (Dipodomys spectabilis). Seven DRB-like sequences (provisionally named MhcDisp-DRB*01 through *07) were isolated from spleen cDNA and most likely comprise ≥5 loci; this multiformity is quite unlike the situation in muroid rodents such as Mus, Rattus, and Peromyscus. In silico translation revealed the presence of important structural residues for glycosylation sites, salt bonds, and CD4+ T-cell recognition. Amino-acid distances varied widely among the seven sequences (2-34%). Nuclear DNA sequences from the Disp-DRB*07 locus (∼10 kb) revealed a conventional exon/intron structure as well as a number of microsatellites and short interspersed nuclear elements (B4, Alu, and IDL-Geo subfamilies). Rates of nucleotide substitution at Disp-DRB*07 are similar in both exons and introns (π=0.015 and 0.012, respectively), which suggests relaxed selection and may indicate that this locus is an expressed pseudogene. Finally, we performed BLASTn searches against Dipodomys ordii genomic sequences (unassembled reads) and find 90-97% nucleotide similarity between the two kangaroo rat species. Collectively, these data suggest that class II diversity in heteromyid rodents is based on polylocism and departs from the muroid architecture.
Single-sample methods of bottleneck detection are now routine analyses in studies of wild populat... more Single-sample methods of bottleneck detection are now routine analyses in studies of wild populations and conservation genetics. Three common approaches to bottleneck detection are the heterozygosity excess, mode-shift, and M-ratio tests. Empirical groundtruthing of these methods is difficult, but their performances are critical for the accurate reconstruction of population demography. We use two banner-tailed kangaroo rat (Dipodomys spectabilis) populations from southeastern Arizona (USA) that are known to have experienced recent demographic reductions to search for genetic bottleneck signals with eight microsatellite loci. Over eight total sample-years, neither population showed a genetic bottleneck signature. M-ratios in both populations were large, stable, and never fell below a critical significance value (M c). The mode shift test did not detect any distortion of allele frequencies, and tests of heterozygosity excess were not significant in postbottleneck samples when we used standard microsatellite mutation models. The genetic effects of bottlenecks like those experienced by our study populations should be strongly influenced by rates of mutation and migration. We used genetic parentage data to estimate a relatively high mutation rate in D. spectabilis (0.0081 mutants/generation/locus), but mutation alone is unlikely to explain the temporal distribution of rare alleles that we observed. Migration (gene flow) is a more likely explanation, despite prior mark-recapture analysis that estimated very low rates of interpopulation dispersal. We interpret our kangaroo rat data in light of the broader literature and conclude that in natural populations connected by dispersal, demographic bottlenecks may prove difficult to detect using molecular genetic data.
Dispersal by young mammals away from their natal site is generally thought to reduce inbreeding, ... more Dispersal by young mammals away from their natal site is generally thought to reduce inbreeding, with its attendant negative fitness consequences. Genetic data from the dwarf mongoose, a pack-living carnivore common in African savannas, indicate that there are exceptions to this generalization. In dwarf mongoose populations in the Serengeti National Park, Tanzania, breeding pairs are commonly related, and close inbreeding has no measurable effect on offspring production or adult survival. Inbreeding occurs because average relatedness among potential mates within a pack is high, because mating patterns within the pack are random with respect to the relatedness of mates, and because dispersal does little to decrease the relatedness among mates. Young females are more likely to leave a pack when the dominant male is a close relative but are relatively infrequent dispersers. Young males emigrate at random with respect to the relatedness of die dominant female and tend to disperse to packs that contain genetically similar individuals.
Summary Ranging patterns, feeding activity, and time budgets of a group of gray-cheeked mangabeys... more Summary Ranging patterns, feeding activity, and time budgets of a group of gray-cheeked mangabeys in the Kibale Forest, western Uganda, were studied in May-June 1971 and from March 1972 to April 1973. Locations and activities of individuals in a fifteen-member group of this arboreal primate were systematically recorded at half-hourly intervals during continuous following of the group. Phenological data were concurrently collected for eleven species of intensively used trees. Mangabeys are primarily frugivores, although leaves and flowers of some species are eaten and substantial time was devoted to insect foraging. Although a typical twice-yearly alternation of wet and dry periods exists in this forest, strongly seasonal trends are the exception in the following aspects of mangabey behaviour: (1) extent and location of areas used, (2) distance moved daily, (3) percentage of time spent feeding or moving, (4) percentage of time spent feeding on different food types. An explanation may be provided by the phenological data, which indicate that many species of tree used by mangabeys fruit either asynchronously and nonseasonally or synchronously but at very long and possibly irregular intervals. Thus mangabeys are faced with foods which fluctuate widely in availability, particularly within a small area, but which are not seasonal in their fluctuations.
Summary Bushbuck density, activity cycles, and ranging patterns on the Mweya Peninsula have been ... more Summary Bushbuck density, activity cycles, and ranging patterns on the Mweya Peninsula have been determined by continuous observation of individually recognizable animals. Individuals were followed for periods of 2 to 12 h, and observations were continued at night with the aid of a Starlight Scope image intensifier. The density of this population of bushbuck is very high compared to those reported using more standard censusing techniques. Home range size is larger (15-3-35-2 ha) for adult and subadult males than for females and immatures. Sex ratios show a preponderance of adult females, as has been reported for other populations. Contrary to most published accounts, these bushbuck are no more active at night than during the day; rather, they exhibit cycles of activity with a periodicity of 2–5 h. A crepuscular peak of movement is, however, apparent. Examination of individual home ranges and of ranging patterns indicates that this crepuscular activity peak is connected with a complete disjunction of areas utilized at night and during the day. Bushbuck move out of thickets into patches of grassland at dusk, returning to thickets before dawn. Other differences between nocturnal and diurnal activity include an increase in the relative amount of grazing at night. Possible reasons for these phenomena, in particular the probable role of predation, are discussed.
... PETER M. WASER, STEVEN N. AUSTAD,* AND BRIAN KEANE Department of Biological Sciences, Purdue ... more ... PETER M. WASER, STEVEN N. AUSTAD,* AND BRIAN KEANE Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907 Submitted May 24, 1985; Revised ... Father-daughter inbreeding should be more common than mother-son inbreed-ing. ...
Spool-and-line tracking is an innovative and inexpensive way to record the movements of small mam... more Spool-and-line tracking is an innovative and inexpensive way to record the movements of small mammals in a variety of habitats, and could have important applications for conservation related studies. However, the potential negative effects of the method have not been investigated. We document the effects of spool-and-line tracking on short-term change in body mass, recapture, and survival probability of banner-tailed kangaroo rats, Dipodomys spectabilis, in southeastern Arizona. We attached spools to D. spectabilis adults of both sexes during 3 y of varying environmental conditions, with total sample sizes of 90 experimental and 81 control animals. We did not attach spools to females in late pregnancy, and, to avoid entanglement, we did not attach spools to kangaroo rats located within 25 m of each other on the same night. We found no significant negative effects of spool attachment on body mass, survival, or recapture probability in either sex in any year.
Proceedings of the Royal Society B: Biological Sciences, 2012
Metapopulation ecology has historically been rich in theory, yet analytical approaches for inferr... more Metapopulation ecology has historically been rich in theory, yet analytical approaches for inferring demographic relationships among local populations have been few. We show how reverse-time multi-state capture-recapture models can be used to estimate the importance of local recruitment and interpopulation dispersal to metapopulation growth. We use 'contribution metrics' to infer demographic connectedness among eight local populations of banner-tailed kangaroo rats, to assess their demographic closure, and to investigate sources of variation in these contributions. Using a 7 year dataset, we show that: (i) local populations are relatively independent demographically, and contributions to local population growth via dispersal within the system decline with distance; (ii) growth contributions via local survival and recruitment are greater for adults than juveniles, while contributions involving dispersal are greater for juveniles; (iii) central populations rely more on local recruitment and survival than peripheral populations; (iv) contributions involving dispersal are not clearly related to overall metapopulation density; and (v) estimated contributions from outside the system are unexpectedly large. Our analytical framework can classify metapopulations on a continuum between demographic independence and panmixia, detect hidden population growth contributions, and make inference about other population linkage forms, including rescue effects and source-sink structures. Finally, we discuss differences between demographic and genetic population linkage patterns for our system.
... Keywords copulatory plugs; sperm competition; inbreeding avoidance. CorrespondenceJennifer C.... more ... Keywords copulatory plugs; sperm competition; inbreeding avoidance. CorrespondenceJennifer C. McCreight, Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA. Email: jmccreig@uw.edu Editor: Robert Knell ...
The collared peccary (Pecari tajacu) is a social species that recently has expanded its historica... more The collared peccary (Pecari tajacu) is a social species that recently has expanded its historical range, yet little is known of its dispersal behavior at the population or biogeographic level. We used autosomal and cytoplasmic markers to assess whether the genetic variation among 4 populations in Texas retains a signal of historically recent founding events. Genetic differentiation based on mitochondrial DNA (mtDNA) haplotype frequencies (F ST) among these 4 populations was substantial. The mtDNA haplotype mismatch distributions indicate that P. tajacu recently has expanded its range across Texas; however, microsatellite-based standard analyses of molecular variance (AMOVAs) and pairwise F ST estimates indicated little variation among populations, suggesting that dispersal is accomplished primarily by males. We also tested the alternative power of mtDNA haplotype or microsatellite genotype distribution patterns to detect a sex bias in instantaneous short-distance dispersal. Sex-specific hierarchical AMOVAs of mtDNA haplotype distributions (based on data from the most genetically diverse population) yielded significantly larger female-specific fixation index values compared to males, indicating a male instantaneous dispersal bias; however, variation in microsatellite frequency distribution was not partitioned in a sex-specific manner. Also, when sex-specific pairwise F ST /(1 2 F ST) among herds was regressed against the log of the distance between each pair of herds, we found no significant effect of distance for either sex and no sex-specific difference using other microsatellite-based analyses (mean sex-specific relatedness, r, or F ST). We conclude that sampling scale limits microsatellite-based methods of detecting instantaneous dispersal sex bias, especially when gene flow is substantial and microsatellite polymorphism is modest (,20 alleles/locus). These results indicate that mtDNA can be used to infer instantaneous dispersal behavior for both sexes in cases where microsatellites have proven insufficient.
INTRODUCTION Marler [1965, 1967, 19681 suggested that habitat differences influence both the moda... more INTRODUCTION Marler [1965, 1967, 19681 suggested that habitat differences influence both the modality of choice for communication and the expected complexity of signal reper-toires. Signal frequency, sound source height, and time of day all have since been shown to ...
Two opposing hypotheses concerning determinants of mangabey (Cercocebus albigena) ranging pattern... more Two opposing hypotheses concerning determinants of mangabey (Cercocebus albigena) ranging patterns have been advocated. One hypothesis suggests that ranging patterns of mangabeys are largely a response to fruit availability, while the other hypothesis advocates that concerns of fruit availability are supplemented or overridden by concerns of fecal contamination and that the risk of parasite infection, especially during dry weather, determines their pattern of range use. In this 9 month study of mangabeys in the Kanyawara study area of Kibale National Park, mangabeys moved longer distances during the wet season than during the dry season. There were no seasonal differences in group spread, number of 50 by 50 m quadrats used, or in quadrat overlap between sequential sample periods. Intensity of quadrat use was closely related to the number of fruiting trees/lianas in the quadrats, irrespective of season. These findings are consistent with the hypothesis that fruit availability is a main factor influencing mangabey ranging patterns. The results are not consistent with the hypothesis that mangabey ranging patterns largely reflect differential seasonal risk of parasite infection. Am.
Genes of the major histocompatibility complex (MHC) are exceptionally polymorphic due to the comb... more Genes of the major histocompatibility complex (MHC) are exceptionally polymorphic due to the combined effects of natural and sexual selection. Most research in wild populations has focused on the second exon of a single class II locus (DRB), but complete gene sequences can provide an illuminating backdrop for studies of intragenic selection, recombination, and organization. To this end, we characterized class II loci in the banner-tailed kangaroo rat (Dipodomys spectabilis). Seven DRB-like sequences (provisionally named MhcDisp-DRB*01 through *07) were isolated from spleen cDNA and most likely comprise ≥5 loci; this multiformity is quite unlike the situation in muroid rodents such as Mus, Rattus, and Peromyscus. In silico translation revealed the presence of important structural residues for glycosylation sites, salt bonds, and CD4+ T-cell recognition. Amino-acid distances varied widely among the seven sequences (2-34%). Nuclear DNA sequences from the Disp-DRB*07 locus (∼10 kb) revealed a conventional exon/intron structure as well as a number of microsatellites and short interspersed nuclear elements (B4, Alu, and IDL-Geo subfamilies). Rates of nucleotide substitution at Disp-DRB*07 are similar in both exons and introns (π=0.015 and 0.012, respectively), which suggests relaxed selection and may indicate that this locus is an expressed pseudogene. Finally, we performed BLASTn searches against Dipodomys ordii genomic sequences (unassembled reads) and find 90-97% nucleotide similarity between the two kangaroo rat species. Collectively, these data suggest that class II diversity in heteromyid rodents is based on polylocism and departs from the muroid architecture.
Single-sample methods of bottleneck detection are now routine analyses in studies of wild populat... more Single-sample methods of bottleneck detection are now routine analyses in studies of wild populations and conservation genetics. Three common approaches to bottleneck detection are the heterozygosity excess, mode-shift, and M-ratio tests. Empirical groundtruthing of these methods is difficult, but their performances are critical for the accurate reconstruction of population demography. We use two banner-tailed kangaroo rat (Dipodomys spectabilis) populations from southeastern Arizona (USA) that are known to have experienced recent demographic reductions to search for genetic bottleneck signals with eight microsatellite loci. Over eight total sample-years, neither population showed a genetic bottleneck signature. M-ratios in both populations were large, stable, and never fell below a critical significance value (M c). The mode shift test did not detect any distortion of allele frequencies, and tests of heterozygosity excess were not significant in postbottleneck samples when we used standard microsatellite mutation models. The genetic effects of bottlenecks like those experienced by our study populations should be strongly influenced by rates of mutation and migration. We used genetic parentage data to estimate a relatively high mutation rate in D. spectabilis (0.0081 mutants/generation/locus), but mutation alone is unlikely to explain the temporal distribution of rare alleles that we observed. Migration (gene flow) is a more likely explanation, despite prior mark-recapture analysis that estimated very low rates of interpopulation dispersal. We interpret our kangaroo rat data in light of the broader literature and conclude that in natural populations connected by dispersal, demographic bottlenecks may prove difficult to detect using molecular genetic data.
Dispersal by young mammals away from their natal site is generally thought to reduce inbreeding, ... more Dispersal by young mammals away from their natal site is generally thought to reduce inbreeding, with its attendant negative fitness consequences. Genetic data from the dwarf mongoose, a pack-living carnivore common in African savannas, indicate that there are exceptions to this generalization. In dwarf mongoose populations in the Serengeti National Park, Tanzania, breeding pairs are commonly related, and close inbreeding has no measurable effect on offspring production or adult survival. Inbreeding occurs because average relatedness among potential mates within a pack is high, because mating patterns within the pack are random with respect to the relatedness of mates, and because dispersal does little to decrease the relatedness among mates. Young females are more likely to leave a pack when the dominant male is a close relative but are relatively infrequent dispersers. Young males emigrate at random with respect to the relatedness of die dominant female and tend to disperse to packs that contain genetically similar individuals.
Summary Ranging patterns, feeding activity, and time budgets of a group of gray-cheeked mangabeys... more Summary Ranging patterns, feeding activity, and time budgets of a group of gray-cheeked mangabeys in the Kibale Forest, western Uganda, were studied in May-June 1971 and from March 1972 to April 1973. Locations and activities of individuals in a fifteen-member group of this arboreal primate were systematically recorded at half-hourly intervals during continuous following of the group. Phenological data were concurrently collected for eleven species of intensively used trees. Mangabeys are primarily frugivores, although leaves and flowers of some species are eaten and substantial time was devoted to insect foraging. Although a typical twice-yearly alternation of wet and dry periods exists in this forest, strongly seasonal trends are the exception in the following aspects of mangabey behaviour: (1) extent and location of areas used, (2) distance moved daily, (3) percentage of time spent feeding or moving, (4) percentage of time spent feeding on different food types. An explanation may be provided by the phenological data, which indicate that many species of tree used by mangabeys fruit either asynchronously and nonseasonally or synchronously but at very long and possibly irregular intervals. Thus mangabeys are faced with foods which fluctuate widely in availability, particularly within a small area, but which are not seasonal in their fluctuations.
Summary Bushbuck density, activity cycles, and ranging patterns on the Mweya Peninsula have been ... more Summary Bushbuck density, activity cycles, and ranging patterns on the Mweya Peninsula have been determined by continuous observation of individually recognizable animals. Individuals were followed for periods of 2 to 12 h, and observations were continued at night with the aid of a Starlight Scope image intensifier. The density of this population of bushbuck is very high compared to those reported using more standard censusing techniques. Home range size is larger (15-3-35-2 ha) for adult and subadult males than for females and immatures. Sex ratios show a preponderance of adult females, as has been reported for other populations. Contrary to most published accounts, these bushbuck are no more active at night than during the day; rather, they exhibit cycles of activity with a periodicity of 2–5 h. A crepuscular peak of movement is, however, apparent. Examination of individual home ranges and of ranging patterns indicates that this crepuscular activity peak is connected with a complete disjunction of areas utilized at night and during the day. Bushbuck move out of thickets into patches of grassland at dusk, returning to thickets before dawn. Other differences between nocturnal and diurnal activity include an increase in the relative amount of grazing at night. Possible reasons for these phenomena, in particular the probable role of predation, are discussed.
... PETER M. WASER, STEVEN N. AUSTAD,* AND BRIAN KEANE Department of Biological Sciences, Purdue ... more ... PETER M. WASER, STEVEN N. AUSTAD,* AND BRIAN KEANE Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907 Submitted May 24, 1985; Revised ... Father-daughter inbreeding should be more common than mother-son inbreed-ing. ...
Spool-and-line tracking is an innovative and inexpensive way to record the movements of small mam... more Spool-and-line tracking is an innovative and inexpensive way to record the movements of small mammals in a variety of habitats, and could have important applications for conservation related studies. However, the potential negative effects of the method have not been investigated. We document the effects of spool-and-line tracking on short-term change in body mass, recapture, and survival probability of banner-tailed kangaroo rats, Dipodomys spectabilis, in southeastern Arizona. We attached spools to D. spectabilis adults of both sexes during 3 y of varying environmental conditions, with total sample sizes of 90 experimental and 81 control animals. We did not attach spools to females in late pregnancy, and, to avoid entanglement, we did not attach spools to kangaroo rats located within 25 m of each other on the same night. We found no significant negative effects of spool attachment on body mass, survival, or recapture probability in either sex in any year.
Proceedings of the Royal Society B: Biological Sciences, 2012
Metapopulation ecology has historically been rich in theory, yet analytical approaches for inferr... more Metapopulation ecology has historically been rich in theory, yet analytical approaches for inferring demographic relationships among local populations have been few. We show how reverse-time multi-state capture-recapture models can be used to estimate the importance of local recruitment and interpopulation dispersal to metapopulation growth. We use 'contribution metrics' to infer demographic connectedness among eight local populations of banner-tailed kangaroo rats, to assess their demographic closure, and to investigate sources of variation in these contributions. Using a 7 year dataset, we show that: (i) local populations are relatively independent demographically, and contributions to local population growth via dispersal within the system decline with distance; (ii) growth contributions via local survival and recruitment are greater for adults than juveniles, while contributions involving dispersal are greater for juveniles; (iii) central populations rely more on local recruitment and survival than peripheral populations; (iv) contributions involving dispersal are not clearly related to overall metapopulation density; and (v) estimated contributions from outside the system are unexpectedly large. Our analytical framework can classify metapopulations on a continuum between demographic independence and panmixia, detect hidden population growth contributions, and make inference about other population linkage forms, including rescue effects and source-sink structures. Finally, we discuss differences between demographic and genetic population linkage patterns for our system.
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