Coexistence of the social types: genetic population structure in the ant Formica exsecta

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.     

Population genetic structure and male-biased dispersal in the queenless ant Diacamma cyaneiventre

In this study we investigated the population genetic structure of the queenless ant Diacamma cyaneiventre. This species, lacking winged queens, is likely to have a restricted female dispersal. We used both mitochondrial and microsatellite markers to assess the consequence of such restricted female dispersal at three geographical scales: within a given locality (< 1 km), between localities within a given region (< 10 km) and between regions (> 36 km). Within a locality, a strong population structure was observed for mitochondrial DNA (mtDNA) whereas weak or nonexistent population genetic structure was observed for the microsatellites (around 5% of the value for mtDNA). Male gene flow was estimated to be about 20-30 times higher than female gene flow at this scale. At a larger spatial scale, very strong genetic differentiation for both markers was observed between localities - even within a single region. Female dispersal is nonexistent at these scales and male dispersal is very restricted, especially between regions. The phylogeographical structure of the mtDNA haplotypes as well as the very low genetic diversity of mtDNA within localities indicate that new sites are colonized by a single migration event from adjacent localities, followed by successive colony fissions. These patterns of genetic variability and differentiation agree with what is theoretically expected when colonization events are kin-structured and when, following colonization, dispersion is mainly performed by males.     

The genetic population structure of the ant Plagiolepis xene-implications for genetic vulnerability of obligate social parasites

Obligatory social parasites, such as ant species that need colonies of other ant species for reproduction, are rare and many of them are classified as vulnerable. This is especially the case with highly adapted permanent inquilines that are specialised on one or a few host species. Their rarity may be due to reduced dispersal abilities, as a result of reduced body size, altered wing morphology, and curtailed nuptial flight, eventually leading to inbreeding. Furthermore, the host populations may differ in their ability to resist the parasite, yet the conditions of successful parasite invasion are largely unknown. Here we investigated the population structure of the inquiline ant Plagiolepis xene and its host P. pygmaea, using microsatellite data. Genetic differentiation, inbreeding, the effective population size and nest kin structure were analysed. We found that populations of P. xene are established by a single or at most a few individuals, and that the populations were genetically highly differentiated. However, within individual host populations the parasite is able to maintain panmixia, although data on the host suggests that the local distribution of the parasite also follows patterns of substructuring in the host population. Altogether our results suggest that inquiline parasite populations are genetically highly vulnerable.     

Mosaic structure of native ant supercolonies

According to the inclusive fitness theory, some degree of positive relatedness is required for the evolution and maintenance of altruism. However, ant colonies are sometimes large interconnected networks of nests, which are genetically homogenous entities, causing a putative problem for the theory. We studied spatial structure and genetic relatedness in two supercolonies of the ant Formica exsecta, using nuclear and mitochondrial markers. We show that there may be multiple pathways to supercolonial social organization leading to different spatial genetic structures. One supercolony formed a genetically homogenous population dominated by a single mtDNA haplotype, as expected if founded by a small number of colonizers, followed by nest propagation by budding and domination of the habitat patch. The other supercolony had several haplotypes, and the spatial genetic structure was a mosaic of nuclear and mitochondrial clusters. Genetic diversity probably originated from long‐range dispersal, and the mosaic population structure is likely a result of stochastic short‐range dispersal of individuals. Such a mosaic spatial structure is apparently discordant with the current knowledge about the integrity of ant colonies. Relatedness was low in both populations when estimated among nestmates, but increased significantly when estimated among individuals sharing the same genetic cluster or haplogroup. The latter association indicates the important historical role of queen dispersal in the determination of the spatial genetic structure.     

Hierarchical analysis of population genetic structure in the monogynous ant Cataglyphis cursor using microsatellite and mitochondrial DNA markers

Despite having winged queens, female dispersal in the monogynous ant Cataglyphis cursor is likely to be restricted because colonies reproduce by fission. We investigated the pattern of population genetic structure of this species using eight microsatellite markers and a mitochondrial DNA (mtDNA) sequence, in order to examine the extent of female and nuclear gene flow in two types of habitat. Sampling was carried out at a large spatial scale (16 sites from 2.5 to 120 km apart) as well as at a fine spatial scale (two 4.5-km transects, one in each habitat type). The strong spatial clustering of mtDNA observed at the fine spatial scale strongly supported a restricted effective female dispersal. In agreement, patterns of the mtDNA haplotypes observed at large and fine spatial scales suggested that new sites are colonized by nearby sites. Isolation by distance and significant nuclear genetic structure have been detected at all the spatial scales investigated. The level of local genetic differentiation for mitochondrial marker was 15 times higher than for the nuclear markers, suggesting differences in dispersal pattern between the two sexes. However, male gene flow was not sufficient to prevent significant nuclear genetic differentiation even at short distances (500 m). Isolation-by-distance patterns differed between the two habitat types, with a linear decrease of genetic similarities with distance observed only in the more continuous of the two habitats. Finally, despite these low dispersal capacities and the potential use of parthenogenesis to produce new queens, no signs of reduction of nuclear genetic diversity was detected in C. cursor populations.     

Possible female philopatry of the smooth hammerhead shark Sphyrna zygaena revealed by genetic structure patterns

We assessed the spatial pattern of genetic structure of smooth hammerhead shark Sphyrna zygaena in 10 localities from the Northern Mexican Pacific. A total of 35 haplotypes were identified in 129 sequences of the mtDNA control region. The results showed slight but significant genetic structure among localities (Φ_ST = 0.044, P < 0.001). In addition, the localities with highest number of juveniles were genetically different (Φ_ST = 0.058, P < 0.024), which may be representative of nursery areas. The genetic differentiation pattern can be associated to female philopatry and preference for particular birthing sites. Finally, historical demography shows that S. zygaena populations present a recent demographic expansion that occurred during glacial events in the late Pleistocene to early Holocene.     

Reduced genetic variation and strong genetic population structure in the freshwater killifish Valencia letourneuxi (Valenciidae) based on nuclear and mitochondrial markers

The genetic variation of the critically endangered Corfu killifish (Valencia letourneuxi), an endemic freshwater fish species of the western Balkans, was assessed for nine populations sampled in eight water systems in western continental Greece, the Peloponnese and the Ionian Island of Corfu, using mitochondrial and microsatellite markers. The analyses were based on data from three mtDNA regions (D‐loop, COI and 16S rRNA sequences) and 14 microsatellite loci. Samples from the congeneric species Valencia hispanica and the phylogenetically closely related species Aphanius fasciatus were also used in the study as outgroups. Both the mitochondrial and the microsatellite analyses revealed three distinct population groupings associated with the geographical distribution of the populations: one southern group occupying rivers draining to the Patraikos Gulf, the second one including the populations flowing into the Amvrakikos Gulf and the third, more northern group, including the other populations from rivers in Corfu Island and Epirus flowing into the Ionian Sea. Within these groupings there is limited genetic differentiation between populations; in addition, there is reduced intrapopulation genetic variation, evidenced by low heterozygosity values, number of alleles and haplotype diversity. In terms of taxonomic implications and appropriate management actions for conservation, our data suggest that the major population groups should be regarded at least as three distinct conservation units (CUs), with translocation and restocking actions to take place only within the geographical range of the CU concerned. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 334–349.     

Fine-scale population genetic structure in a fission-fusion society

Nonrandom patterns of mating and dispersal create fine-scale genetic structure in natural populations — especially of social mammals — with important evolutionary and conservation genetic consequences. Such structure is well-characterized for typical mammalian societies; that is, societies where social group composition is stable, dispersal is male-biased, and males form permanent breeding associations in just one or a few social groups over the course of their lives. However, genetic structure is not well understood for social mammals that differ from this pattern, including elephants. In elephant societies, social groups fission and fuse, and males never form permanent breeding associations with female groups. Here, we combine 33 years of behavioural observations with genetic information for 545 African elephants ( Loxodonta africana ), to investigate how mating and dispersal behaviours structure genetic variation between social groups and across age classes. We found that, like most social mammals, female matrilocality in elephants creates co-ancestry within core social groups and significant genetic differentiation between groups (Φ_ST = 0.058). However, unlike typical social mammals, male elephants do not bias reproduction towards a limited subset of social groups, and instead breed randomly across the population. As a result, reproductively dominant males mediate gene flow between core groups, which creates cohorts of similar-aged paternal relatives across the population. Because poaching tends to eliminate the oldest elephants from populations, illegal hunting and poaching are likely to erode fine-scale genetic structure. We discuss our results and their evolutionary and conservation genetic implications in the context of other social mammals.     

The socially parasitic ant Polyergus mexicanus has host‐associated genetic population structure and related neighbouring colonies

The genetic structure of populations can be both a cause and a consequence of ecological interactions. For parasites, genetic structure may be a consequence of preferences for host species or of mating behaviour. Conversely, genetic structure can influence where conspecific interactions among parasites lay on a spectrum from cooperation to conflict. We used microsatellite loci to characterize the genetic structure of a population of the socially parasitic dulotic (aka “slave‐making”) ant (Polyergus mexicanus), which is known for its host‐specificity and conspecific aggression. First, we assessed whether the pattern of host species use by the parasite has influenced parasite population structure. We found that host species use was correlated with subpopulation structure, but this correlation was imperfect: some subpopulations used one host species nearly exclusively, while others used several. Second, we examined the viscosity of the parasite population by measuring the relatedness of pairs of neighbouring parasitic ant colonies at varying distances from each other. Although natural history observations of local dispersal by queens suggested the potential for viscosity, there was no strong correlation between relatedness and distance between colonies. However, 35% of colonies had a closely related neighbouring colony, indicating that kinship could potentially affect the nature of some interactions between colonies of this social parasite. Our findings confirm that ecological forces like host species selection can shape the genetic structure of parasite populations, and that such genetic structure has the potential to influence parasite‐parasite interactions in social parasites via inclusive fitness.     

云南中华按蚊的遗传变异和种群结构

为了掌握云南省各地中华按蚊种群间的遗传变异和种群结构特征,测序并分析了采自云南9个样本点5个种群组的89头中华按蚊的线粒体COII基因。结果表明这些中华按蚊种群的COII基因序列平均单倍型多样性指数和核苷酸多样性指数分别为h=0.933,π=0.00406,共有51个变异位点,占分析的739个碱基总数的6.9%;定义了39个单倍型,有2个频率最高的单倍型H1和H9,分别占个体序列数的20.2%和12.4%;系统发育分析表明单倍型与地理位置没有明显的对应关系,单倍型网络图显示大部分单倍型分布没有明显的亲缘地理格局,主要以单倍型H1、H9、H4、H33和H2为中心呈星状分布,但元江和元阳构成的种群组(YU)单倍型存在明显地域分布特征;AMOVA结果表明种群组间遗传变异为12.58%,达到显著水平(P=0.04888),地理种群组间具有明显种群遗传结构。不同地区两两种群组间的Fst值和Nm值显示大部分种群组间存在基因交流,没有形成明显的遗传分化,但YU种群组和其他种群组间缺乏明显的基因交流,这主要是因为哀牢山的阻隔,使云南东西部形成两种不同的气候,产生了明显的遗传分化;歧点分布图显示为明显单峰分布,中性检测结果均为显著负值,说明云南省的中华按蚊种群在近期经历过复杂的种群扩张事件。掌握中华按蚊遗传多样性及分化特征,对中华按蚊及疟疾控制具有重要的作用。     

Large-scale population genetics of the mountain ant Proformica longiseta (Hymenoptera: Formicidae)

Proformica longiseta Collingwood is an endemic ant found in southeastern Spain that inhabits high mountains and is widespread within an altitude range. We have studied the population genetics and biogeography of 14 populations of P. longiseta throughout its distribution using microsatellites and mitochondrial data. Populations are strongly structured for both markers and show isolation by distance, which together with the absence of intra-population variation in mitochondrial DNA suggest strong female philopatry and limited male dispersal. In spite of this, no recent bottlenecks or inbreeding were detected. Finally, we report on a population currently located where it did not exist 14 years ago, above the usual altitudinal limit known for the species, which may be due to recent colonization enhanced by global warming.     

Allozyme variation and population genetic structure of Betula alnoides from Guangxi,China

Allozyme variation and population genetic structure of Betula alnoides Buch. Ham. ex D. Don in 11 natural populations from Guangxi Zhuang Autonomous Region, China, were investigated by starch gel electrophoresis. Variation at 15 loci from 10 enzyme systems was analyzed. Allozyme analysis revealed a high level of genetic variation in this species, with percentage of polymorphic loci (P _p ), the average number of alleles per locus (A _p ), and the expected heterozygosity (H _ep ) being 55.2%, 2.0, and 0.204, respectively, which exceeds the average level among out-crossing wind-pollinated woody species at the population level. At the species level, P _s , A _s , and H _es were 60.0%, 2.67, and 0.206, respectively.The observed heterozygosity (H _op ) was higher than H _ep , indicating the existence of natural selection against homozygotes. The negative fixation index (F = –0.216) implied a significant excess of heterozygosity at the population level. Among-population differentiation (F _ST ) accounted for 4.0% of the total variation. No significant correlation was detected between the genetic distance and geographic distance among populations. Extensive gene flow was inferred, based on the allozyme data )N _m = 6.000 from F _ST , N _m = 5.605 from the private allele method). The results demonstrated that the fragmentation status of B. alnoides had no remarkable effects on the population genetic structure of this species. Some populations are recommended for both in situ genetic conservation and germplasm collection for breeding programs.     

Very low genetic variability in the Indian queenless ant Diacamma indicum

Abstract We developed microsatellite markers and combined them with mitochondrial markers to analyse the population genetic structure of the queenless ant Diacamma indicum. This species, lacking winged queens, is likely to have a restricted female dispersal but exhibits various life history traits suggesting higher dispersal abilities than the other Diacamma species. Only 4 of 11 microsatellites were polymorphic and only 1 had more than 4 alleles over 166 individuals originating from 7 populations from the south of India. Only one mitochondrial DNA (mtDNA) haplotype was detected throughout India (including one population in the north) and Sri Lanka. Such a level of polymorphism is particularly low compared with other Diacamma species having much smaller ranges in the south of India. A strong genetic differentiation was observed between populations separated by more than a few kilometres. We also analysed the genetic differentiation between the Indian populations and two populations from the Japanese island of Okinawa, which are morphologically similar and might belong to the same species. The genetic differentiation was high for both markers, suggesting an absence of ongoing gene flow between these populations.     

基于线粒体COI基因分析钩手水母的群体遗传结构

钩手水母(Gonionemus vertens)为大西洋和太平洋广布种, 是我国习见的有毒水母种类之一。本文对采自黄渤海海域4个地理群体的104个钩手水母线粒体COI基因序列进行扩增, 并结合GenBank上其他182个钩手水母同源序列进行序列变异分析。在286个基因序列中共检测出52个多态位点, 定义了14种单倍型。总群体的单倍型多样性和核苷酸多样性分别为0.743 ± 0.012和1.046% ± 0.097%, 与其他几种大型水母相比, 钩手水母总群体的遗传多样性处于较高水平。AMOVA结果显示, 60.17%的分子变异源于群组间, 13.37%的分子变异源于群体内, 26.46%的分子变异源于组内群体间, 群组间、群体内和组内群体间的遗传分化均极显著。F_st值统计检验表明, 中国厦门群体与乐亭、东营、烟台、大连群体间存在显著的遗传分化, 大连与东营、烟台群体间也存在显著的遗传分化。系统分析结果显示, 钩手水母群体间存在2个明显的单倍型谱系分支。不同的钩手水母地理群体间具有复杂的遗传模式, 钩手水母复杂的生活史、扩散能力、地理隔离和海流分布可能是影响钩手水母遗传结构的重要因素。     

Phylogeography and population genetic structure of the European roe deer in Switzerland following recent recolonization

In the early 1800s, the European roe deer (Capreolus capreolus) was probably extirpated from Switzerland, due to overhunting and deforestation. After a federal law was enacted in 1875 to protect lactating females and young, and limiting the hunting season, the roe deer successfully recovered and recolonized Switzerland. In this study, we use mitochondrial DNA and nuclear DNA markers to investigate the recolonization and assess contemporary genetic structure in relation to broad topographic features, in order to understand underlying ecological processes, inform future roe deer management strategies, and explore the opportunity for development of forensic traceability tools. The results concerning the recolonization origin support natural, multidirectional immigration from neighboring countries. We further demonstrate that there is evidence of weak genetic differentiation within Switzerland among topographic regions. Finally, we conclude that the genetic data support the recognition of a single roe deer management unit within Switzerland, within which there is a potential for broad‐scale geographic origin assignment using nuclear markers to support law enforcement.     

Mating frequency and genetic structure of the Argentine ant Linepithema humile

The nest and population genetic structures of the Argentine ant, Linepithema humile were investigated using eight microsatellite loci. Genotypes of the sperm from spermathecae of 87 queens were consistent with all queens being singly inseminated. The probability of a double mating remaining undetected was low (0.012) suggesting that no queens or only a very low proportion mate multiply. The relatedness between the queens and their mates was negative (R = -0.164 +/- 0.044) and significantly different to zero (P = 0.020). However, the high negative relatedness value was caused by a significant allele frequency difference between the sexes at a single locus (Lhum-28). When this locus was removed from the analyses, the relatedness was not significantly different from zero (R = 0.013 +/- 0.050, P = 0.812). Analysis of 10 nests revealed that the genetic differentiation among nests was weak (FST = 0.003) and not distinguishable from zero (P = 0.468). Similarly, the overall relatedness among nestmate females was not significantly different from zero (R = 0.007 +/- 0.018, P = 0.706). These results are consistent with the lack of distinct nest boundaries and the large number of queens per nest in the population studied. Although mating takes place inside the nest, the inbreeding coefficient was close to zero (F = 0.007 +/- 0.025, P = 0.786). Overall, these data indicate substantial local gene flow mediated by movement of reproductives among colonies.     

Seasonal dynamics of population genetic structure in cryptic taxa of the Pellioditis marina complex (Nematoda: Rhabditida)

The distribution patterns and genetic structure of the Pellioditis marina species complex in Belgium and The Netherlands were compared between four consecutive seasons. Different types of habitats (coast, estuary, semi-estuary and lake) with different degrees of connectivity were sampled. In addition, each habitat type was characterised by either temporal or permanent algal deposits. We screened 426 bp of the mitochondrial cytochrome oxidase c (COI) gene with the single-strand conformation polymorphism (SSCP) method in 1615 individuals of Pellioditis marina. The 51 haplotypes were divided into four (sympatric) lineages, with divergences ranging from 0.25 to 10.6%. Our results show that the lineages have different temporal dynamics, which may be linked to abiotic factors. Analysis of Molecular Variance (AMOVA) indicated a significant structuring in the PmI lineage, which correlated with habitat characteristics and which changed over time (Mantel, r = 0.51; p = 0.126). Intrapopulational diversity was similar in all locations, and temporal changes in haplotype frequencies were not higher in temporary than in permanent algal deposits. Instead, the results of the temporal survey indicated that (some) P. marina populations are characterised by a metapopulation structure. It is emphasized that a complete and correct interpretation of processes causing genetic structuring within species and of the genetic structure itself can only be done when analyses are performed at several time points.     

Genetic variation and population structure in the endangered greater horseshoe bat Rhinolophus ferrumequinum

Following a dramatic decline last century, the British population of the endangered greater horseshoe bat Rhinolophus ferrumequinum is highly fragmented. To examine the consequences of fragmentation and limited dispersal on patterns of genetic structure and variation, we used microsatellite markers to screen bats from around 50% of the known maternity colonies in Britain, and two areas from continental Europe. Analyses revealed that Welsh and English colonies were genetically isolated. This, and lower variability in Britain than north France, may result from either genetic drift, or the species' colonization history. Gene flow among most neighbouring colonies was not generally restricted, with one exception. These findings have important implications for the ongoing conservation management of this species.     

Genetic diversity and population structure of wolverine (Gulo gulo) populations at the southern edge of their current distribution in North America with implications for genetic viability

The current range of wolverines (Gulo gulo) within the lower 48 states includes small, remnant populations in Idaho, Washington, Wyoming and Montana. The size and trend of each of these populations and connectivity to adjacent populations in the contiguous United States and Canada are poorly understood. In this study, levels of genetic diversity and population genetic structure were examined in three states (Idaho, Wyoming, and Montana) and two Canadian provinces (Alberta and British Columbia) using both mitochondrial (mtDNA) and nuclear microsatellite DNA. Restricted levels of gene flow were detected among these populations with mitochondrial and nuclear DNA and our observations suggest a pattern of male-mediated gene flow. Populations in the United States appear to be receiving migrants from Canada, however, substantial genetic differentiation suggests that gene flow may not be high enough to prevent genetic drift. Our analyses suggest that at least 400 breeding pairs or 1–2 effective migrants per generation would be needed to ensure genetic viability in the long-term for each of the populations in the United States. Significant matrilineal structuring and restricted female gene flow indicates that demographic viability will depend upon the movement of female wolverines into new territories. Results from this study provide guidelines for conservation and management and indicate the need for more ecological data.     

Microgeographic genetic structure and intraspecific parasitism in the ant Leptothorax nylanderi

1. Genetic colony structure of the small central European ant Leptothorax nylanderi is affected strongly by ecological constraints such as nest site availability and intraspecific social parasitism. 2. Although L. nylanderi is generally monogynous and monandrous, more than a quarter of all nests collected in a dense population near Würzburg, Germany, contained several matrilines. As shown by microsatellite analysis, the average nest‐mate relatedness in these nests was 0.20. Genetically heterogeneous nests arise from nest take‐over by alien colonies or founding queens, a result of severe competition for nest sites. 3. In summer, more than one‐third of all colonies inhabited several nest sites at a time. Polydomy appears to be rather limited, with two or three nests belonging to a single polydomous colony. 4. Queens appear to dominate male production; only a small fraction (8%) of males was definitively not progeny of the queen present but might have been worker progeny or offspring of another queen. 5. Strong evidence for heterozygote deficiency was found and a total of nine diploid males was discovered in two colonies. These findings suggest deviation from random mating through small, localised nuptial flights.