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1.
We studied genetic differentiation between two social forms (M-type: single queen, independent nest founding; P-type: multiple queens, dependent nest founding, building of colonial networks) of the ant Formica truncorum in a locality where the social types characterize two sympatric populations. The genetic results indicate restricted gene flow between the social forms. Female gene flow between the forms appears to be absent as they did not share mitochondrial haplotypes. Significant nuclear differentiation and the distribution of private alleles suggest that male gene flow between the forms is weak. However, the assignment analysis indicates some gene flow with P males mating with M females. The results have potentially important implications concerning social evolution within the forms but they need to be confirmed in other localities before they can be generalized. The colonies in the M-type population have earlier been shown to produce split sex ratios, depending on the mating frequency of the queens. The inferred gene flow from the P to the M type means that the split sex ratio is partly suboptimal, possibly because the P populations are not long-lived enough to influence the behavioural decisions in the M colonies.  相似文献   

2.
    
The breeding system of social organisms affects many important aspects of social life. Some species vary greatly in the number of breeders per group, but the mechanisms and selective pressures contributing to the maintenance of this polymorphism in social structure remain poorly understood. Here, we take advantage of a genetic dataset that spans 15 years to investigate the dynamics of colony queen number within a socially polymorphic ant species. Our study population of Formica selysi has single‐ and multiple‐queen colonies. We found that the social structure of this species is somewhat flexible: on average, each year 3.2% of the single‐queen colonies became polygynous, and conversely 1.4% of the multiple‐queen colonies became monogynous. The annualized queen replacement rates were 10.3% and 11.9% for single‐ and multiple‐queen colonies, respectively. New queens were often but not always related to previous colony members. At the population level, the social polymorphism appeared stable. There was no genetic differentiation between single‐ and multiple‐queen colonies at eight microsatellite loci, suggesting ongoing gene flow between social forms. Overall, the regular and bidirectional changes in queen number indicate that social structure is a labile trait in F. selysi, with neither form being favored within a time‐frame of 15 years.  相似文献   

3.
    
The ant Formica exsecta has two types of colonies that exist in sympatry but usually as separate subpopulations: colonies with simple social organization and single queens (M type) or colonial networks with multiple queens (P type). We used both nuclear (DNA microsatellites) and mitochondrial markers to study the transition between the social types, and the contribution of males and females in gene flow within and between the types. Our results showed that the social types had different spatial genetic structures. The M subpopulations formed a fairly uniform population, whereas the P subpopulations were, on average, more differentiated from each other than from the nearby M subpopulations and could have been locally established from the M-type colonies, followed by philopatric behavior and restricted emigration of females. Thus, the relationship between the two social types resembles that of source (M type) and sink (P type) populations. The comparison of mitochondrial (phiST) and nuclear (FST) differentiation indicates that the dispersal rate of males is four to five times larger than that of females both among the P-type subpopulations and between the social types. Our results suggest that evolution toward complex social organization can have an important effect on genetic population structure through changes in dispersal behavior associated with different sociogenetic organizations.  相似文献   

4.
    
The major subspecies group of the great tit, Parus major , has experienced demographic and spatial expansions during the last century in several sites at the edges of its distribution range. These expansions, although temporarily very even, have resulted in dissimilar patterns of molecular diversity. Populations locating at regions of contact to other subspecies groups (in Amur, Kirghizia–Kazakhstan, and Iran) show divergence from central population by nuclear and mitochondrial markers. In Amur, gene flow from minor group could be detected based on the existence of private minor alleles in the major population. In Kirghizia and Kazakhstan, the bokharensis and major groups share almost all the microsatellite alleles detected though frequencies differ. In Iran, three geographically close populations are distinct according to the mitochondrial sequences but also indications of present or recent admixture is detected. Populations, which have expanded to regions previously unoccupied by the species (northern UK and Finland), show divergence only by one of the markers. The variability in molecular differentiation may be due to dissimilar expansions, depending on whether the colonized regions have previously been occupied by another subspecies or not, on the amount of colonizing birds, and on the amount of past and present gene flow.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 201–210.  相似文献   

5.
Uncertainty over the role of shifts in social behavior in the process of speciation in social insects has stimulated interest in determining the extent of gene flow between conspecific populations differing in colony social organization. Allele and genotype frequencies at 12 neutral polymorphic protein markers, as well as the numbers of alleles at the sex-determining locus (loci), are shown here to be consistent with significant ongoing gene flow between two geographically adjacent populations of Solenopsis invicta that differ in colony queen number. Data from a thirteenth protein marker that is under strong differential selection in the two social forms confirm that such gene flow occurs. Data from this selected locus, combined with knowledge of the reproductive biology of the two social forms, further suggest that interform gene flow is largely unidirectional and mediated through males only. This unusual pattern of gene flow results from the influence of the unique social enviroments of the two forms on the behavior of workers and on the reproductive physiology of sexuals.  相似文献   

6.
We employ a battery of 33 polymorphic microsatellite loci to describe geographical population structure of the mangrove killifish (Kryptolebias marmoratus), the only vertebrate species known to have a mixed-mating system of selfing and outcrossing. Significant population genetic structure was detected at spatial scales ranging from tens to hundreds of kilometres in Florida, Belize, and the Bahamas. The wealth of genotypic information, coupled with the highly inbred nature of most killifish lineages due to predominant selfing, also permitted treatments of individual fish as units of analysis. Genetic clustering algorithms, neighbour-joining trees, factorial correspondence, and related methods all earmarked particular killifish specimens as products of recent outcross events that could often be provisionally linked to specific migration events. Although mutation is the ultimate source of genetic diversity in K. marmoratus, our data indicate that interlocality dispersal and outcross-mediated genetic recombination (and probably genetic drift also) play key proximate roles in the local 'clonal' dynamics of this species.  相似文献   

7.
    
Among tuco-tucos, Ctenomys rionegrensis is especially amenable to the study of the forces driving population differentiation because of the restricted geographic range it occupies in Uruguay. Within this limited area, the Rio Negro tuco-tuco is limited to sandy soils. It nonetheless exhibits remarkable variation in pelage color, including melanic, agouti, and dark-backed individuals. Two hypotheses have been put forth to explain this pattern: (1) local differentiation and fixation of alternative pelage types by genetic drift under limited gene flow; or (2) fixation by natural selection that may take place even in the presence of gene flow. A previous allozyme study rejected the genetic drift hypothesis on the basis of high inferred levels of migration. New estimates of gene flow from microsatellites and mitochondrial cytochrome b sequences were obtained for C. rionegrensis populations to further test these hypotheses. Much lower levels of gene flow were estimated with these more sensitive markers. Microsatellite-based estimates of gene flow are close to zero and may come closest to estimating current levels of migration. A lack of equilibrium between migration and genetic drift is also strongly suggested by the absence of an isolation-by-distance pattern found in all three genetic datasets. The microsatellite genotype data show that the species is strongly structured geographically, with subpopulations constituting distinct genetic entities. If current levels of gene flow are very low, as indicated by the new data, the local fixation of alternative alleles, including those responsible for pelage color polymorphism, is possible by drift alone. A scenario is thus proposed in which the species expanded in the recent past from a more restricted geographic range and has subsequently differentiated in near isolation, with genetic drift possibly playing a primary role in overall genetic differentiation. The local fixation of pelage color types could also be due to drift, but selection on this trait cannot be ruled out without direct analysis.  相似文献   

8.
9.
    
The termite Mastotermes darwiniensis is the sole extant member of its family and occupies the basal position in the phylogeny of the eusocial order Isoptera. In this study, we investigated the micro- and macrogeographic genetic structure of M. darwiniensis in its native range in Australia. A total of 1591 workers were sampled from 136 infested trees in 24 locales. Each locale was separated by 2-350 km, and these locales were found within two broader geographic regions approximately 1500 km apart. The multilocus genotypes of all termites were assayed at six polymorphic microsatellite loci. The genetic data indicated that colonies typically fed on multiple trees within locales and extended over linear distances of up to 320 m. Single colonies were frequently headed by multiple reproductives. Workers were highly related (r = 0.40) and substantially inbred (f = 0.10). Thus, M. darwiniensis colonies are characterized by the input of alleles from multiple reproductives, which sometimes engage in consanguineous matings. Our analyses of population genetic structure above the level of the colony indicated that locales and regions were significantly differentiated (theta(locale) = 0.50, theta(region) = 0.37). Moreover, locales showed a pattern of genetic isolation by distance within regions. Thus, M. darwiniensis populations display restricted gene flow over moderate geographic distances. We suggest that the genetic patterns displayed by M. darwiniensis result primarily from selective pressures acting to maintain high relatedness among colonymates while allowing colonies to grow rapidly and dominate local habitats.  相似文献   

10.
Using the ant-derived probe (pMY7), we performed DNA fingerprinting in monogynous and polygynous sibling ant speciesCamponotus nawai andCamponotus yamaokai. In monogynousC. nawai, band-sharing probabilities were low between unrelated individuals (mean 0.09), but those and relatedness estimates were consistently high between workers of the same nest (mean 0.85 and 0.74–0.83, respectively), suggesting that the queen mated once and nestmate workers are super-sisters. It also suggested monoandry: that is, that all nestmate workers shared most of the bands which were considered to have derived from a male. In polygynousC. yamaokai, band-sharing probabilities were low between queens of different populations (mean 0.13), moderate between queens of different nests in the same population (mean 0.25), but very high between queens of the same nest (within-nest means were 0.84–0.96). These results suggest that nestmate queens are genetically closely related with each other. Relatedness estimates between colony members sometimes reached 1. This might result from successive intranidal mating (inbreeding or large Wahlund effect) and adoption of new queens into the natal nests.  相似文献   

11.
Matriline and the predominant social tasks performed by workers are correlated in the functionally polygynous ponerine ant Gnamptogenys striatula. This result favors the idea that polygyny might have been secondarily selected and maintained in ants because it provided more genetic variability and, thus, more potential variation in the regulation of the division of labor within mutualistic societies. As in previous studies on ants, nepotism could not be demonstrated. Because of the relatively small number of individuals per colony, these ponerine ants constitute a valuable model for exploring how polyethism is determined in insect societies.  相似文献   

12.
Evolutionary theories of ageing predict that life span increases with decreasing extrinsic mortality, and life span variation among queens in ant species seems to corroborate this prediction: queens, which are the only reproductive in a colony, live much longer than queens in multi-queen colonies. The latter often inhabit ephemeral nest sites and accordingly are assumed to experience a higher mortality risk. Yet, all prior studies compared queens from different single- and multi-queen species. Here, we demonstrate an effect of queen number on longevity and fecundity within a single, socially plastic species, where queens experience the similar level of extrinsic mortality. Queens from single- and two-queen colonies had significantly longer lifespan and higher fecundity than queens living in associations of eight queens. As queens also differ neither in morphology nor the mode of colony foundation, our study shows that the social environment itself strongly affects ageing rate.  相似文献   

13.
Analyses of the evolution of colony queen number in eusocial insects have generally been conducted without specific reference to phylogenetic relationships, leading to incomplete evolutionary explanations for this key attribute of social organization. Consideration of queen number in a phylogenetic context in the highly eusocial Hymenoptera reveals that its evolution has been very conservative in the bees but that it is a highly labile character in most ants. The wasps appear intermediate in this respect, with some large and widespread clades characterized by little or no phylogenetic variability in queen number. This hierarchy of phylogenetic lability suggests that while ant populations may often be responsive to selection on colony queen number linked with local ecology, bees and wasps appear less responsive in this regard, with a significant element of phylogenetic conservatism involved in the expression of this social trait in the latter two groups.  相似文献   

14.
    
Relatedness increases the likelihood of cooperation within colonies of social insects. Polygyny, the coexistence of numerous reproductive females (queens) in a colony, is common in mature colonies of the termite Macrotermes michaelseni. In this species, polygyny results from pleometrosis and from several female alates that jointly found a new colony. To explain this phenomenon, it was suggested that only related females cooperate and survive during maturation of colonies. Using multilocus fingerprints as well as microsatellites, we showed that nestmate queens in mature colonies are unrelated. Furthermore, we found that all nestmate queens contributed to the production of steriles. Even in mature colonies, several matrilines of steriles coexist within a colony. Although genetic diversity within colonies may increase the likelihood of conflicts, high genetic diversity may be important for foraging, colony growth, and resistance to disease and parasites.  相似文献   

15.
The genetic structure of nine colonies of the water vole, Arvicola terrestris , in one area of NE Scotland was studied. Non-destructive samples from 478 individuals (mostly immature animals) were typed for 12 microsatellites. Cases of Hardy-Weinberg disequilibrium were frequent within all colonies. The five colonies in the inland part of the study area also showed frequent cases of linkage disequilibrium. All colonies showed high levels of genetic diversity (unbiased H = 0.52-0.74). All five colonies sampled in successive years showed significant annual changes in genetic composition. All colonies showed genetic differentiation from each other, whether measured by average 6, pairwise 9 or pairwise Nei's genetic distance. The spatial pattern of genetic differentiation was consistent with either a stepping-stone model over the whole study area or an island model within the coastal and inland parts and an intervening barrier to gene flow. The study suggested that the genetic structure of colonies of A. terrestris often departs from the equilibrium states assumed by traditional mefhods for the study of gene flow, and that a parentage-based approach would be fruitful.  相似文献   

16.
    
We studied population genetic variation and structure in the fire ant Solenopsis invicta using nuclear genotypic and mitochondrial DNA (mtDNA) sequence data obtained from samples collected throughout its native range. Geographic populations are strongly differentiated at both genomes, with such structure more pronounced in Brazil than in Argentina. Higher-level regional structure is evident from the occurrence of isolation-by-distance patterns among populations, the recognition of clusters of genetically similar, geographically adjacent populations by ordination analysis, and the detection of an mtDNA discontinuity between Argentina and Brazil coinciding with a previously identified landform of biogeographical relevance. Multiple lines of evidence from both genomes suggest that the ancestors of the ants we studied resembled extant northern Argentine S. invicta , and that existing Brazilian populations were established more recently by serial long-distance colonizations and/or range expansions. The most compelling evidence for this is the corresponding increase in F K (a measure of divergence from a hypothetical ancestor) and decrease in genetic diversity with distance from the Corrientes population in northern Argentina. Relatively deep sequence divergence among several mtDNA clades, coupled with geographical partitioning of many of them, suggests prolonged occupation of South America by S. invicta in more-or-less isolated regional populations. Such populations appear, in some cases, to have come into secondary contact without regaining the capacity to freely interbreed. We conclude that nominal S. invicta in its native range comprises multiple entities that are sufficiently genetically isolated and diverged to have embarked on independent evolutionary paths.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 541–560.  相似文献   

17.
Phylogeographic structure of the eastern pine processionary moth Thaumetopoea wilkinsoni was explored in this study by means of nested clade phylogeographic analyses of COI and COII sequences of mitochondrial DNA and Bayesian estimates of divergence times. Intraspecific relationships were inferred and hypotheses tested to understand historical spread patterns and spatial distribution of genetic variation. Analyses revealed that all T. wilkinsoni sequences were structured in three clades, which were associated with two major biogeographic events, the colonization of the island of Cyprus and the separation of southwestern and southeastern Anatolia during the Pleistocene. Genetic variation in populations of T. wilkinsoni was also investigated using amplified fragment length polymorphisms and four microsatellite loci. Contrasting nuclear with mitochondrial data revealed recurrent gene flow between Cyprus and the mainland, related to the long-distance male dispersal. In addition, a reduction in genetic variability was observed at both mitochondrial and nuclear markers at the expanding boundary of the range, consistent with a recent origin of these populations, founded by few individuals expanding from nearby localities. In contrast, several populations fixed for one single mitochondrial haplotype showed no reduction in nuclear variability, a pattern that can be explained by recurrent male gene flow or selective sweeps at the mitochondrial level. The use of both mitochondrial and nuclear markers was essential in understanding the spread patterns and the population genetic structure of T. wilkinsoni, and is recommended to study colonizing species characterized by sex-biased dispersal.  相似文献   

18.
We present primer sequences for eight polymorphic microsatellite loci for the formicine ant Anoplolepis gracilipes, a serious pest species in South‐East Asia and Pacific islands and still spreading on all continents. Microsatellite loci were isolated with a highly efficient method of enrichment. The number of alleles ranged from two to 19 with an observed heterozygosity ranging from 0.842 to 1.0. The markers were designed for a sociogenetic study as well as for population genetics.  相似文献   

19.
Introduced species offer unique opportunities to study evolution in new environments, and some provide opportunities for understanding the mechanisms underlying macroecological patterns. We sought to determine how introduction history impacted genetic diversity and differentiation of the house sparrow (Passer domesticus), one of the most broadly distributed bird species. We screened eight microsatellite loci in 316 individuals from 16 locations in the native and introduced ranges. Significant population structure occurred between native than introduced house sparrows. Introduced house sparrows were distinguished into one North American group and a highly differentiated Kenyan group. Genetic differentiation estimates identified a high magnitude of differentiation between Kenya and all other populations, but demonstrated that European and North American samples were differentiated too. Our results support previous claims that introduced North American populations likely had few source populations, and indicate house sparrows established populations after introduction. Genetic diversity also differed among native, introduced North American, and Kenyan populations with Kenyan birds being least diverse. In some cases, house sparrow populations appeared to maintain or recover genetic diversity relatively rapidly after range expansion (<50 years; Mexico and Panama), but in others (Kenya) the effect of introduction persisted over the same period. In both native and introduced populations, genetic diversity exhibited large-scale geographic patterns, increasing towards the equator. Such patterns of genetic diversity are concordant with two previously described models of genetic diversity, the latitudinal model and the species diversity model.  相似文献   

20.
  总被引:9,自引:0,他引:9  
Abstract.— We examined genetic variation at 21 polymorphic allozyme loci, 15 nuclear DNA loci, and mitochondrial DNA in four spawning populations of sockeye salmon ( Oncorhynchus nerka ) from Cook Inlet, Alaska, to test for differences in the patterns of divergence among different types of markers. We were specifically interested in testing the suggestion that natural selection at allozyme loci compromises the effectiveness of these markers for describing the amount and patterns of gene flow among populations. We found concordance among markers in the amount of genetic variation within and among populations, with the striking exception of one allozyme locus ( sAH ), which exhibited more than three times the amount of among-population differentiation as other loci. A consideration of reports of discordance between allozymes and other loci indicates that these differences usually result from one or two exceptional loci. We conclude that it is important to examine many loci when estimating genetic differentiation to infer historical amounts of gene flow and patterns of genetic exchange among populations. It is less important whether those loci are allozymes or nuclear DNA markers.  相似文献   

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