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1.
By using both mitochondrial and nuclear multiloci markers, we explored population genetic structure, gene flow and sex-specific dispersal of frillneck lizards ( Chlamydosaurus kingii ) sampled at three locations, separated by 10 to 50 km, in a homogenous savannah woodland in tropical Australia. Apart from a recombinant lizard, the mitochondrial analyses revealed two nonoverlapping haplotypes/populations, while the nuclear markers showed that the frillneck lizards represented three separate clusters/populations. Due to the small population size of the mtDNA, fixation may occur via founder effects and/or drift. We therefore suggest that either of these two processes, or a combination of the two, are the most likely causes of the discordant results obtained from the mitochondrial and the nuclear markers. In contrast to the nonoverlapping mitochondrial haplotypes, in 12 out of 74 lizards, mixed nuclear genotypes were observed, hence revealing a limited nuclear gene flow. Although gene flow should ultimately result in a blending of the populations, we propose that the distinct nuclear population structure is maintained by frequent fires resulting in local bottlenecks, and concomitant spatial separation of the frillneck lizard populations. Limited mark–recapture data and the difference in distribution of the mitochondrial and nuclear markers suggest that the mixed nuclear genotypes were caused by juvenile male-biased dispersal.  相似文献   

2.
Sex-biased dispersal is an almost ubiquitous feature of mammalian life history, but the evolutionary causes behind these patterns still require much clarification. A quarter of a century since the publication of seminal papers describing general patterns of sex-biased dispersal in both mammals and birds, we review the advances in our theoretical understanding of the evolutionary causes of sex-biased dispersal, and those in statistical genetics that enable us to test hypotheses and measure dispersal in natural populations. We use mammalian examples to illustrate patterns and proximate causes of sex-biased dispersal, because by far the most data are available and because they exhibit an enormous diversity in terms of dispersal strategy, mating and social systems. Recent studies using molecular markers have helped to confirm that sex-biased dispersal is widespread among mammals and varies widely in direction and intensity, but there is a great need to bridge the gap between genetic information, observational data and theory. A review of mammalian data indicates that the relationship between direction of sex-bias and mating system is not a simple one. The role of social systems emerges as a key factor in determining intensity and direction of dispersal bias, but there is still need for a theoretical framework that can account for the complex interactions between inbreeding avoidance, kin competition and cooperation to explain the impressive diversity of patterns.  相似文献   

3.
4.
Despite being important models in ecological, evolutionary and conservation biology research, very little is known about the dispersal in anuran amphibians, and juvenile dispersal in particular. Using microsatellite data, we assessed signatures of sex-biased migration in the common frog (Rana temporaria) in Scandinavia. Significant heterozygosity deficiency (FIS) and lower assignment value (mAIc) among females suggest that dispersal in R. temporaria is female biased. Also variance of assignment (vAIc), estimated separately for the two sexes, was consistent with this inference, although the difference was not statistically significant. Possible proximate and ultimate explanations for female-biased dispersal in amphibians are discussed.  相似文献   

5.
We use the assignment technique and a new approach, the 'novel allele technique', to detect sex-biased dispersal in great reed warblers Acrocephalus arundinaceus. The data set consisted of immigrants and philopatric birds in a semi-isolated population in Sweden scored at 21 microsatellite loci. Fourteen cohorts were represented of which the four earliest were used to define a reference population. Female immigrants had lower assignment probability than males (i.e. were less likely to have been sampled in the reference population), and carried the majority of 'novel alleles' (i.e. alleles observed in the population for the first time). The difference in number of novel alleles between sexes was caused by a strong over-representation of females among the few individuals that carried several novel alleles, and there was a tendency for a corresponding female bias among individuals with low assignment probabilities. Immigrant males had similar or lower reproductive success than females. These results lead us to conclude that important interregional gene flow in great reed warblers depends on relatively few dispersing females, and that the novel allele technique may be a useful complement to the assignment technique when evaluating dispersal patterns from temporally structured data.  相似文献   

6.
7.
Greater prairie-chickens (Tympanuchus cupido pinnatus) were once found throughout the tallgrass prairie of midwestern North America but over the last century these prairies have been lost or fragmented by human land use. As a consequence, many current populations of prairie-chickens have become isolated and small. This fragmentation of populations is expected to lead to reductions in genetic variation as a result of random genetic drift and a decrease in gene flow. As expected, we found that genetic variation at both microsatellite DNA and mitochondrial DNA (mtDNA) markers was reduced in smaller populations, particularly in Wisconsin. There was relatively little range-wide geographical structure (FST) when we examined mtDNA haplotypes but there was a significant positive relationship between genetic (FST) and geographical distance (isolation by distance). In contrast, microsatellite DNA loci revealed significant geographical structure (FST) and a weak effect of isolation by distance throughout the range. These patterns were much stronger when populations with reduced levels of genetic variability (Wisconsin) were removed from the analyses. This suggests that the effects of genetic drift were stronger than gene flow at microsatellite loci, whereas these forces were in range-wide equilibrium at mtDNA markers. These differences between the two molecular markers may be explained by a larger effective population size (Ne) for mtDNA, which is expected in species such as prairie-chickens that have female-biased dispersal and high levels of polygyny. Our results suggest that historic populations of prairie-chickens were once interconnected by gene flow but current populations are now isolated. Thus, maintaining gene flow may be important for the long-term persistence of prairie-chicken populations.  相似文献   

8.
Genetic population structure and dispersal in Atlantic Island caddisflies   总被引:2,自引:0,他引:2  
SUMMARY 1. Population genetic structure of Wormaldia tagananana, a caddis with a narrow geographic range and endemic to the Canary Islands, was investigated by studying allozyme variation at 11 putative loci in five of the eight extant populations on Tenerife and La Gomera. Genetic variability, population structure and gene flow were compared with those reported previously in more widespread Trichoptera, particularly Canarian populations of the non-endemic limnephilid Mesophylax aspersus, to examine the hypothesis that the Wormaldia , with its restricted range, would exhibit relatively little genetic variability and gene flow.
2. Despite it being a narrow-range island endemic, genetic variability in populations of W. tagananana is broadly similar to values reported for more widespread caddis.
3. Significant genetic population structure was observed in W. tagananana (overall F ST = 0.387), greater than that seen in M. aspersus and amongst the highest reported for lotic caddis to date. Several site- and island-specific alleles were reported, providing further evidence for the relative isolation of individual Wormaldia populations.
4. Significant deviations from Hardy–Weinberg equilibrium were found in four of five populations (overall F IS = 0.675). This could result from within-locality population substructuring, or offspring within a reach being the product of a limited number of matings.
5. This genetic evidence supports the hypothesis that the restricted range of W. tagananana is, at least in part, because of limited dispersal ability.  相似文献   

9.
The genetic structure of a group or population of organisms can profoundly influence the potential for inbreeding and, through this, can affect both dispersal strategies and mating systems. We used estimates of genetic relatedness as well as likelihood-based methods to reconstruct social group composition and examine sex biases in dispersal in a Costa Rican population of white-throated magpie-jays ( Calocitta formosa , Swainson 1827), one of the few birds suggested to have female-biased natal philopatry. We found that females within groups were more closely related than males, which is consistent with observational data indicating that males disperse upon maturity, whereas females tend to remain in their natal territories and act as helpers. In addition, males were generally unrelated to one another within groups, suggesting that males do not disperse with or towards relatives. Finally, within social groups, female helpers were less related to male than female breeders, suggesting greater male turnover within groups. This last result indicates that within the natal group, female offspring have more opportunities than males to mate with nonrelatives, which might help to explain the unusual pattern of female-biased philopatry and male-biased dispersal in this system. We suggest that the novel approach adopted here is likely to be particularly useful for short-term studies or those conducted on rare or difficult-to-observe species, as it allows one to establish general patterns of philopatry and genetic structure without the need for long-term monitoring of identifiable individuals.  相似文献   

10.
Short amplicon primers were redesigned for 17 microsatellite loci developed in St. Vincent's Amazon and six loci developed in blue-and-yellow macaw and tested using six species of Neotropical parrot. Polymorphism was observed at 12 loci in blue-and-yellow macaw, 10 in red-and-green macaw, 11 in scarlet macaw, 10 in chestnut-fronted macaw, 11 in red-bellied macaw and 16 in mealy parrot. Number of alleles per locus ranged from two to 23 and expected heterozygosity ranged from 0.05 to 0.95. The resulting multiplexed loci will be useful in evaluating genetic diversity, genetic structure and mating system in Neotropical parrots.  相似文献   

11.
In order to detect sex-biased dispersal in the red-billed quelea Quelea quelea in southern Africa, we used the assignment index technique to determine the probability that individuals originated from the population in which they were sampled. This is the first time that this multilocus genetic test has been used in a bird species and is informative despite evidence that the population under study exhibits little genetic structure. There was a pattern of male-biased dispersal, the first example in a passerine, and the first time that evidence of a sex-biased pattern of dispersal has been shown for queleas.  相似文献   

12.
This study describes 12 microsatellite loci identified in the African grey parrot Psittacus erithacus. Eleven were polymorphic, with observed heterozygosities 42–94% (average 68) and exclusion powers of PE1 = 0.996 and PE2 = 0.999. Microsatellites have previously been developed for a number of other parrots but showed limited cross‐species polymorphism. Here high levels of cross‐species amplification were observed: 71% of 32 Psittacines (22 genera). At least seven loci, 58%, were polymorphic in other African parrots as well as Neotropical and Australasian parrots, which diverged from the African parrots c30.6 and over 41.4 million years ago, respectively.  相似文献   

13.
Nonrandom dispersal has been recently advanced as a mechanism promoting fine-scale genetic differentiation in resident populations, yet how this applies to species with high rates of dispersal is still unclear. Using a migratory species considered a classical example of male-biased dispersal (the greater snow goose, Chen caerulescens atlantica ), we documented a temporally stable fine-scale genetic clustering between spatially distinct rearing sites (5–30 km apart), where family aggregates shortly after hatching. Such genetic differentiation can only arise if, in both sexes, dispersal is restricted and nonrandom, a surprising result considering that pairing occurs among mixed flocks of birds more than 3000 km away from the breeding grounds. Fine-scale genetic structure may thus occur even in migratory species with high gene flow. We further show that looking for genetic structure based on nesting sites only may be misleading. Genetically distinct individuals that segregated into different rearing sites were in fact spatially mixed during nesting. These findings provide new, scale-dependent links between genetic structure, pairing, and dispersal and show the importance of sampling different stages of the breeding cycle in order to detect a spatial genetic structure.  相似文献   

14.
Dispersal in birds and mammals tends to be female-biased in monogamous species and male-biased in polygamous species. However results for other taxa, most notably fish, are equivocal. We employed molecular markers and physical tags to test the hypothesis that Atlantic salmon, a promiscuous species with intense male-male competition for access to females, displays male-biased dispersal. We found significant variation in sex ratios and in asymmetric gene flow between neighbouring salmon populations, but little or no evidence for sex-biased dispersal. We show that conditions favouring male dispersal will often be offset by those favouring female dispersal, and that spatial and temporal variation in sex ratios within a metapopulation may favour the dispersal of different sexes in source and sink habitats. Thus, our results reconcile previous discrepancies on salmonid dispersal and highlight the need to consider metapopulation dynamics and sex ratios in the study of natal dispersal of highly fecund species.  相似文献   

15.
Twenty-two polymorphic microsatellite loci were characterized in the Cape parrot, Poicephalus robustus. Nineteen loci were newly isolated from two Cape parrot genomic libraries, and three loci isolated from other parrot species. Loci were characterized in 40 unrelated captive Cape parrots held by aviculturalists. The loci displayed between two and 24 alleles, with the observed heterozygosities ranging between 0.10 and 0.94. This locus set is suitable for identifying clarifying parentage (parentage exclusion probabilities of PE1 = 0.0004 and PE2 = 0.000001). Candidate parents for any Cape parrot individual can now be genotyped to distinguish between individuals, which are truly captive bred and those suspected of being wild-caught birds. Cross-species analysis found up to 31 loci to be polymorphic across 24 additional parrot species tested.  相似文献   

16.
For captive breeding to play a significant role in conservation, ex situ populations must be scientifically managed to meet objective goals for retaining representative genetic variation. Imperfect genealogical information requires fundamental assumptions to be made that may bias downstream measures of genetic importance, upon which management decisions are based. The impacts of such assumptions are most pronounced within breeding programmes characterized by a high proportion of individuals of unknown ancestry, as exemplified by the large captive population of the St Vincent parrot (Amazona guildingii). The degree to which microsatellite-based estimates of relatedness may improve upon the assumptions of conventional pedigree-based management was investigated using genotypic data collected at eight microsatellite loci and two marker-based relatedness estimators. The measure, rxyLR, was found to explain the highest amount of variation in true relatedness. Integration of pairwise estimates of founder relatedness with studbook data transformed current understanding of the relatedness structure of the A. guildingii population from two subgroups characterized by a high and low degree of relatedness, respectively, to a situation where all 72 individuals are prioritized for breeding according to their estimated mean kinships. Furthermore, the discovery of opposing, directional bias exhibited by rxyLR and rxyQG in assigning dyads to a given relationship category suggests that an approach that utilizes a combination of pairwise relatedness estimators may provide the most genetic information for balancing the dual considerations of maximizing gene diversity and minimizing inbreeding in developing breeding recommendations.  相似文献   

17.
Mitochondrial DNA (mtDNA) control-region sequences and microsatellite loci length polymorphisms were used to estimate phylogeographical patterns (historical patterns underlying contemporary distribution), intraspecific population structure and gender-biased dispersal of Phocoenoides dalli dalli across its entire range. One-hundred and thirteen animals from several geographical strata were sequenced over 379 bp of mtDNA, resulting in 58 mtDNA haplotypes. Analysis using F(ST) values (based on haplotype frequencies) and phi(ST) values (based on frequencies and genetic distances between haplotypes) yielded statistically significant separation (bootstrap values P < 0.05) among most of the stocks currently used for management purposes. A minimum spanning network of haplotypes showed two very distinctive clusters, differentially occupied by western and eastern populations, with some common widespread haplotypes. This suggests some degree of phyletic radiation from west to east, superimposed on gene flow. Highly male-biased migration was detected for several population comparisons. Nuclear microsatellite DNA markers (119 individuals and six loci) provided additional support for population subdivision and gender-biased dispersal detected in the mtDNA sequences. Analysis using F(ST) values (based on allelic frequencies) yielded statistically significant separation between some, but not all, populations distinguished by mtDNA analysis. R(ST) values (based on frequencies of and genetic distance between alleles) showed no statistically significant subdivision. Again, highly male-biased dispersal was detected for all population comparisons, suggesting, together with morphological and reproductive data, the existence of sexual selection. Our molecular results argue for nine distinct dalli-type populations that should be treated as separate units for management purposes.  相似文献   

18.
19.
Many marine species have vastly different capacities for dispersal during larval, juvenile and adult life stages, and this has the potential to complicate the identification of population boundaries and the implementation of effective management strategies such as marine protected areas. Genetic studies of population structure and dispersal rarely disentangle these differences and usually provide only lifetime-averaged information that can be considered by managers. We address this limitation by combining age-specific autocorrelation analysis of microsatellite genotypes, hydrodynamic modelling and genetic simulations to reveal changes in the extent of dispersal during the lifetime of a marine fish. We focus on an exploited coral reef species, Lethrinus nebulosus, which has a circum-tropical distribution and is a key component of a multispecies fishery in northwestern Australia. Conventional population genetic analyses revealed extensive gene flow in this species over vast distances (up to 1,500 km). Yet, when realistic adult dispersal behaviours were modelled, they could not account for these observations, implying adult dispersal does not dominate gene flow. Instead, hydrodynamic modelling showed that larval L. nebulosus are likely to be transported hundreds of kilometres, easily accounting for the observed gene flow. Despite the vast scale of larval transport, juvenile L. nebulosus exhibited fine-scale genetic autocorrelation, which declined with age. This implies both larval cohesion and extremely limited juvenile dispersal prior to maturity. The multidisciplinary approach adopted in this study provides a uniquely comprehensive insight into spatial processes in this marine fish.  相似文献   

20.
The genetic structure and demography of local populations is tightly linked to the rate and scale of dispersal. Dispersal parameters are notoriously difficult to determine in the field, and remain often completely unknown for smaller organisms. In this study, we investigate spatial and temporal genetic structure in relation to dispersal patterns among local populations of the probably most abundant European mammals, the common vole (Microtus arvalis). Voles were studied in six natural populations at distances of 0.4-2.5 km in three different seasons (fall, spring, summer) corresponding to different life-history stages. Field observations provided no direct evidence for movements of individuals between populations. The analysis of 10 microsatellite markers revealed a persistent overall genetic structure among populations of 2.9%, 2.5% and 3% FST in the respective season. Pairwise comparisons showed that even the closest populations were significantly differentiated from each other in each season, but there was no evidence for temporal differentiation within populations or isolation by distance among populations. Despite significant genetic structure, assignment analyses identified a relatively high proportion of individuals as being immigrants for the population where they were captured. The immigration rate was not significantly lower for females than for males. We suggest that a generally low and sex-dependent effective dispersal rate as the consequence of only few immigrants reproducing successfully in the new populations together with the social structure within populations may explain the maintenance of genetic differentiation among populations despite migration.  相似文献   

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