The impact of habitat fragmentation on genetic structure of the Japanese sika deer (<Emphasis Type="Italic">Cervus nippon</Emphasis>) in southern Kantoh,revealed by mitochondrial D-loop sequences

In southern Kantoh, Japanese sika deer (Cervus nippon) are distributed discontinuously due to large urban areas and developed road networks. To assess the impact of habitat fragmentation on sika deer subpopulations, we examined mitochondrial D-loop sequences from 435 individuals throughout southern Kantoh. About 13 haplotypes were detected, and their distributions revealed spatial genetic structure. Significant genetic differentiation was observed among seven of eight subpopulations. We found no significant correlation between pairwise F _ST and geographical distance among subpopulations. Genetic diversity indices suggested that seven of eight subpopulations had probably experienced population bottlenecks in the recent past. Therefore, and in the light of the results of a nested clade analysis of these haplotypes, we conclude that recent fluctuations in population size and the interruption of gene flow due to past and present habitat fragmentation have played major roles influencing the spatial genetic structure of the sika deer population. This is the first evidence of spatial genetic population structure in the highly fragmented sika deer population in Honshu, Japan.     

Gene flow and spatio-temporal genetic variation among sympatric populations of Tetranychus kanzawai (Acari: Tetranychidae) occurring on different host plants, as estimated by microsatellite gene diversity

We investigated spatio-temporal genetic variation in allele frequency and estimated gene flow among sympatric populations of Tetranychus kanzawai on different host plants by the use of microsatellite markers. In the analysis of spatial genetic variation, no isolation by distance was detected among the populations. Gene flow between populations on Hydrangea macrophylla and those on other host plants was relatively restricted, whereas the populations on Akebia quinata and Clerodendrum trichotomum were almost panmictic. Our study on temporal genetic variation showed (1) that population differentiation was slightly reduced during the period from April to May owing to frequent gene flow among populations; and (2) that population differentiation was greatly enhanced from May to October because of bottleneck effects. Genetic differentiation among T. kanzawai populations was caused by the effect of host plants rather than by the effect of geographic distance among populations, suggesting possibility of sympatric host race formation in this species.This revised version was published online in May 2005 with a corrected cover date.     

FINE-SCALE GENETIC STRUCTURE AND SOCIAL ORGANIZATION IN FEMALE WHITE-TAILED DEER

Abstract: Social behavior of white-tailed deer (Odocoileus virginianus) can have important management implications. The formation of matrilineal social groups among female deer has been documented and management strategies have been proposed based on this well-developed social structure. Using radiocollared (n = 17) and hunter or vehicle-killed (n = 21) does, we examined spatial and genetic structure in white-tailed deer on a 7,000-ha portion of the Savannah River Site in the upper Coastal Plain of South Carolina, USA. We used 14 microsatellite DNA loci to calculate pairwise relatedness among individual deer and to assign doe pairs to putative relationship categories. Linear distance and genetic relatedness were weakly correlated (r = −0.08, P = 0.058). Relationship categories differed in mean spatial distance, but only 60% of first-degree-related doe pairs (full sibling or mother-offspring pairs) and 38% of second-degree-related doe pairs (half sibling, grandmother-granddaughter pairs) were members of the same social group based on spatial association. Heavy hunting pressure in this population has created a young age structure among does, where the average age is <2.5 years, and <4% of does are >4.5 years old. This—combined with potentially elevated dispersal among young does—could limit the formation of persistent, cohesive social groups. Our results question the universal applicability of recently proposed models of spatial and genetic structuring in white-tailed deer, particularly in areas with differing harvest histories.     

Evolutionary aspects of the metapopulation dynamics of Biomphalaria pfeifferi,the intermediate host of Schistosoma mansoni

Combining genetic and demographic data is a powerful approach to study adaptation process and evolutionary forces acting in natural populations. We focus on the freshwater snail Biomphalaria pfeifferi, the intermediate host of Schistosoma mansoni. Twenty‐one populations sampled in the south of Madagascar were genotyped at six microsatellite loci. Demographic parameters and parasitic prevalence were estimated monthly over the year preceding the genetic sampling. Our results indicate that populations experience recurrent bottlenecks and size fluctuations, which strongly depresses the genetic diversity within population. The recolonization of depleted sites involves genetically differentiated immigrants. We detected frequent migration events along rivers and rare migration events between watersheds. This explains the high level of differentiation observed among populations. The negative regression observed between the prevalence of S. mansoni and the genetic diversity of B. pfeifferi populations indicates that host consanguinity may affect prevalence through the genetic mechanisms involved in resistance. Coevolutionary outcomes are also influenced by the relative migration rates of snails and flukes, but the parasite local adaptation may be prevented by rare long distance dispersal in snails and the phylogeographical patterns of colonization of both hosts and snails.     

Contrasting effects of habitat discontinuity on three closely related fungivorous beetle species with diverging host‐use patterns and dispersal ability

Understanding how landscape structure influences biodiversity patterns and ecological processes are essential in ecological research and conservation practices. Forest discontinuity is a primary driver affecting the population persistence and genetic structure of forest‐dwelling species. However, the actual impacts on populations are highly species‐specific. In this study, we tested whether dispersal capability and host specialization are associated with susceptibility to forest discontinuity using three closely related, sympatric fungivorous ciid beetle species (two host specialists, Octotemnus assimilis and O. crassus; one host generalist, O. kawanabei). Landscape genetic analyses and the estimation of effective migration surfaces (EEMS) method consistently demonstrated contrasting differences in the relationships between genetic structure and configuration of forest land cover. Octotemnus assimilis, one of the specialists with a presumably higher dispersal capability due to lower wing loading, lacked a definite spatial genetic structure in our study landscape. The remaining two species showed clear spatial genetic structure, but the results of landscape genetic analyses differed between the two species: while landscape resistance appeared to describe the spatial genetic structure of the specialist O. crassus, genetic differentiation of the generalist O. kawanabei was explained by geographic distance alone. This finding is consistent with the prediction that nonforest areas act more strongly as barriers between specialist populations. Our results suggest that differences in host range can influence the species‐specific resistance to habitat discontinuity among closely related species inhabiting the same landscape.     

Temporal shifts of DNA‐microsatellite allele profiles in roe deer (Capreolus capreolus L.) within three decades

DNA‐microsatellite polymorphism (four loci) was studied in 56 male roe deer (Capreolus capreolus) from a 900‐ha hunting territory in the Vosges du Nord Mountains (France), culled over 34 years (1956–1990). Changed allele frequencies at two loci within this period, and increased allelic diversity, were traced to a phase of reduced population density and subsequent immigration. Decadic population samples collected within 900‐ha were distinguished by higher genetic variability measures than were certain geographical samples across Central Europe (4–900 km). On average, the decadic cohorts were distinguished by a gene diversity index of G_ST = 0.0286, and a genetic distance of D = 0.0938, which reflect 54% (G_ST) and 69% (D) of the respective geographic (350 km) differentiation indices of roe deer in Central Europe. The importance of demography and population ecology effects for microevolution in a large mammal is demonstrated, as is the risk of artefact by composing population samples of deer over several years. Population genetic screening should cover various demes of roe deer from the same general region, and be based on many unlinked polymorphic loci, to minimize the distorting effects of genetic dynamics at the small spatial scale.     

东北虎豹国家公园梅花鹿的空间遗传格局及其影响因素

东北梅花鹿是东北虎豹国家公园主要的大型食草动物之一,是东北虎豹的主要猎物,对针阔混交林群落的维持有关键的作用,探究其遗传多样性及空间遗传格局对东北梅花鹿的保护以及国家公园生态系统的健康至关重要。在国家公园珲春保护区内,通过非损伤方法获得遗传样本,利用微卫星标记,研究该梅花鹿种群的空间遗传格局及其影响因素。结果表明：本研究区梅花鹿种群平均期望杂合度为0.721,遗传多样性较为丰富。有限的扩散能力常常导致种群在遗传距离上具有显著的空间自相关模式,本研究区梅花鹿种群在0-1km距离等级内在遗传距离上具有显著的空间自相关现象,据此可推测,该地区梅花鹿扩散距离为1km左右。STRUCTURE分析表明,珲春地区梅花鹿种群不存在明显的遗传分化。各种空间变量可以显著影响物种的遗传分化。本研究选取海拔、坡度、坡向、地表起伏率、人类干扰5个变量,研究其对梅花鹿种群遗传结构的影响,这5个变量多被认为与大中型哺乳动物扩散阻碍相关。依据5个变量建立了336个阻力模型,并进行偏曼特尔检验。其中,依据海拔、坡向、地表起伏率、人类干扰假设建立的246个阻力模型与遗传距离之间的关系并不显著,综合所有变量的15个生境适宜性模型阻力模型与遗传距离的关系也都不显著。在依据坡度假设建构的75个阻力模型中,只有1个模型与遗传距离有显著的正相关关系,该模型同时也是在控制空间自相关影响后,在所有模型中与遗传距离相关性最高的模型。根据该模型推测,最适宜梅花鹿扩散的坡度为10°,梅花鹿可能倾向于利用缓坡进行扩散。结果对东北虎豹国家公园梅花鹿种群的保护具有重要意义。     

Population structure and landscape genetics in the endangered subterranean rodent Ctenomys porteousi

In order to devise adequate conservation and management strategies for endangered species, it is important to incorporate a reliable understanding of its spatial population structure, detecting the existence of demographic partitions throughout its geographical range and characterizing the distribution of its genetic diversity. Moreover, in species that occupy fragmented habitats it is essential to know how landscape characteristics may affect the genetic connectivity among populations. In this study we use eight microsatellite markers to analyze population structure and gene flow patterns in the complete geographic range of the endangered rodent Ctenomys porteousi. Also, we use landscape genetics approaches to evaluate the effects of landscape configuration on the genetic connectivity among populations. In spite of geographical proximity of the sampling sites (8–27 km between the nearest sites) and the absence of marked barriers to individual movement, strong population structure and low values of gene flow were observed. Genetic differentiation among sampling sites was consistent with a simple model of isolation by distance, where peripheral areas showed higher population differentiation than those sites located in the central area of the species’ distribution. Landscape genetics analysis suggested that habitat fragmentation at regional level has affected the distribution of genetic variation among populations. The distance of sampling sites to areas of the landscape having higher habitat connectivity was the environmental factor most strongly related to population genetic structure. In general, our results indicate strong genetic structure in C. porteousi, even at a small spatial scale, and suggest that habitat fragmentation could increase the population differentiation.     

Postglacial colonization history reflects in the genetic structure of natural populations of Festuca rubra in Europe

We conducted a large‐scale population genetic survey of genetic diversity of the host grass Festuca rubra s.l., which fitness can be highly dependent on its symbiotic fungus Epichloë festucae, to evaluate genetic variation and population structure across the European range. The 27 studied populations have previously been found to differ in frequencies of occurrence of the symbiotic fungus E. festucae and ploidy levels. As predicted, we found decreased genetic diversity in previously glaciated areas in comparison with nonglaciated regions and discovered three major maternal genetic groups: southern, northeastern, and northwestern Europe. Interestingly, host populations from Greenland were genetically similar to those from the Faroe Islands and Iceland, suggesting gene flow also between those areas. The level of variation among populations within regions is evidently highly dependent on the postglacial colonization history, in particular on the number of independent long‐distance seed colonization events. Yet, also anthropogenic effects may have affected the population structure in F. rubra. We did not observe higher fungal infection rates in grass populations with lower levels of genetic variability. In fact, the fungal infection rates of E. festucae in relation to genetic variability of the host populations varied widely among geographical areas, which indicate differences in population histories due to colonization events and possible costs of systemic fungi in harsh environmental conditions. We found that the plants of different ploidy levels are genetically closely related within geographic areas indicating independent formation of polyploids in different maternal lineages.     

GENETIC CONSEQUENCES OF SEED DISPERSAL IN THREE SYMPATRIC FOREST HERBS. I. HIERARCHICAL POPULATION-GENETIC STRUCTURE

To examine the effects of seed dispersal on spatial genetic structure, we compare three sympatric species of forest herbs in the family Apiaceae whose fruits differ widely in morphological adaptations for animal-attached dispersal. Cryptotaenia canadensis has smooth fruits that are gravity dispersed, whereas Osmorhiza claytonii and Sanicula odorata fruits have appendages that facilitate their attachment to animals. The relative seed-dispersal ability among species, measured as their ability to remain attached to mammal fur, is ranked Sanicula > Osmorhiza > Cryptotaenia. We use a nested hierarchical sampling design to analyze genetic structure at spatial scales ranging from a few meters to hundreds of kilometers. Genetic differentiation among population subdivisions, estimated by average genetic distance and hierarchical F-statistics, has an inverse relationship with dispersal ability such that Cryptotaenia > Osmorhiza > Sanicula. In each species, genetic differentiation increases with distance among population subdivisions. Stochastic variation in gene flow, arising from seed dispersal by attachment to animals, may partly explain the weak relationship between pairwise spatial and genetic distance among populations and heterogeneity in estimates of single locus F-statistics. A hierarchical island model of gene flow is invoked to describe the effects of seed dispersal on population genetic structure. Seed dispersal is the predominant factor affecting variation in gene flow among these ecologically similar, taxonomically related species.     

Spatial structure of genetic variation and primary succession in the pioneer tree species Antirhea borbonica on La Réunion

In habitats where colonization and extinction are recurrent, the distribution of gene frequencies among patches of suitable habitat may reflect the age structure of different populations. In this study, we quantify population genetic structure for a pioneer tree species, Antirhea borbonica, in a chrono-sequence of primary succession on the lava flows of the Piton de La Fournaise volcano (La Réunion). Using microsatellite loci and amplified fragment length polymorphism (AFLP) markers, we quantified genetic variation within and among populations for early- and late-succession populations in a landscape where extinction and recolonization are recurrent (the ‘Grand Brûlé’) and for late-succession populations in a more stable landscape. This study produced three main results. First, we detected no evidence that founder events increase genetic differentiation among colonizing populations; F_ST values among early- and among late-succession populations were similar. Second, we found no evidence for isolation by distance; genetic distance was not correlated with spatial distance within and among populations. Third, F_IS values are consistently high in all populations, despite the fact that A. borbonica populations are functionally close to dioecy and thus expected to have an outcrossing mating system. Multiple colonization events from different sources may limit differentiation among young populations and spatial isolation may enhance differentiation among late-succession populations. Ecological processes acting during colonization may create the conditions for spatial aggregation within pioneer populations, and thus contribute to the high F_IS values.     

MAINTENANCE OF ECOLOGICALLY SIGNIFICANT GENETIC VARIATION IN THE TIGER SWALLOWTAIL BUTTERFLY THROUGH DIFFERENTIAL SELECTION AND GENE FLOW

Differential selection in a heterogeneous environment is thought to promote the maintenance of ecologically significant genetic variation. Variation is maintained when selection is counterbalanced by the homogenizing effects of gene flow and random mating. In this study, we examine the relative importance of differential selection and gene flow in maintaining genetic variation in Papilio glaucus. Differential selection on traits contributing to successful use of host plants (oviposition preference and larval performance) was assessed by comparing the responses of southern Ohio, north central Georgia, and southern Florida populations of P. glaucus to three hosts: Liriodendron tulipifera, Magnolia virginiana, and Prunus serotina. Gene flow among populations was estimated using allozyme frequencies from nine polymorphic loci. Significant genetic differentiation was observed among populations for both oviposition preference and larval performance. This differentiation was interpreted to be the result of selection acting on Florida P. glaucus for enhanced use of Magnolia, the prevalent host in Florida. In contrast, no evidence of population differentiation was revealed by allozyme frequencies. F_ST-values were very small and Nm, an estimate of the relative strengths of gene flow and genetic drift, was large, indicating that genetic exchange among P. glaucus populations is relatively unrestricted. The contrasting patterns of spatial differentiation for host-use traits and lack of differentiation for electrophoretically detectable variation implies that differential selection among populations will be counterbalanced by gene flow, thereby maintaining genetic variation for host-use traits.     

Seascape genetics of the stalked kelp Pterygophora californica and comparative population genetics in the Santa Barbara Channel

We conducted a population genetic analysis of the stalked kelp, Pterygophora californica, in the Santa Barbara Channel, California, USA. The results were compared with previous work on the genetic differentiation of giant kelp, Macrocystis pyrifera, in the same region. These two sympatric kelps not only share many life history and dispersal characteristics but also differ in that dislodged P. californica does not produce floating rafts with buoyant fertile sporophytes, commonly observed for M. pyrifera. We used a comparative population genetic approach with these two species to test the hypothesis that the ability to produce floating rafts increases the genetic connectivity among kelp patches in the Santa Barbara Channel. We quantified the association of habitat continuity and oceanographic distance with the genetic differentiation observed in stalked kelp, like previously conducted for giant kelp. We compared both overall (across all patches) and pairwise (between patches) genetic differentiation. We found that oceanographic transit time, habitat continuity, and geographic distance were all associated with genetic connectivity in P. californica, supporting similar previous findings for M. pyrifera. Controlling for differences in heterozygosity between kelp species using Jost's D_EST, we showed that global differentiation and pairwise differentiation were similar among patches between the two kelp species, indicating that they have similar dispersal capabilities despite their differences in rafting ability. These results suggest that rafting sporophytes do not play a significant role in effective dispersal of M. pyrifera at ecologically relevant spatial and temporal scales.     

Range‐wide analysis of genetic structure in a widespread,highly mobile species (Odocoileus hemionus) reveals the importance of historical biogeography

Highly mobile species that thrive in a wide range of habitats are expected to show little genetic differentiation across their range. A limited but growing number of studies have revealed that patterns of broad‐scale genetic differentiation can and do emerge in vagile, continuously distributed species. However, these patterns are complex and often shaped by both historical and ecological factors. Comprehensive surveys of genetic variation at a broad scale and at high resolution are useful for detecting cryptic spatial genetic structure and for investigating the relative roles of historical and ecological processes in structuring widespread, highly mobile species. In this study, we analysed 10 microsatellite loci from over 1900 samples collected across the full range of mule deer (Odocoileus hemionus), one of the most widely distributed and abundant of all large mammal species in North America. Through both individual‐ and population‐based analyses, we found evidence for three main genetic lineages, one corresponding to the ‘mule deer’ morphological type and two to the ‘black‐tailed deer’ type. Historical biogeographic events likely are the primary drivers of genetic divergence in this species; boundaries of the three lineages correspond well with predictions based on Pleistocene glacial cycles, and substructure within each lineage demonstrates island vicariance. However, across large geographic areas, including the entire mule deer lineage, we found that genetic variation fit an isolation‐by‐distance pattern rather than discrete clusters. A lack of genetic structure across wide geographic areas of the continental west indicates that ecological processes have not resulted in restrictions to gene flow sufficient for spatial genetic structure to emerge. Our results have important implications for our understanding of evolutionary mechanisms of divergence, as well as for taxonomy, conservation and management.     

Estimation of dispersal distances of the obligately plant‐associated ant Crematogaster decamera

1. In obligate symbioses with horizontal transmission, the population dynamics of the partner organisms are highly interdependent. Host population size limits symbiont number, and distribution of partners is restricted by the presence and thus dispersal abilities of their respective partner. The Crematogaster decamera–Macaranga hypoleuca ant–plant symbiosis is obligate for both partners. Host survival depends on colonisation by its ant partner while foundress queens require hosts for colony establishment. 2. An experimental approach and population genetic analyses were combined to estimate dispersal distances of foundresses in their natural habitat in a Bornean primary rainforest. 3. Colonisation frequency was significantly negatively correlated with distance to potential reproductive colonies. Results were similar for seedlings at natural densities as well as for seedlings brought out in the area experimentally. Population genetic analysis revealed significant population differentiation with an F_ST of 0.041 among foundresses (n = 157) located at maximum 2280 m apart. In genetic spatial autocorrelation, genotypes of foundresses were significantly more similar than expected at random below 550 m and less similar above 620 m. Direct estimation of dispersal distances by pedigree analysis yielded an average dispersal distance of 468 m (maximum 1103 m). 4. For ants that disperse on the wing, genetic differentiation at such small spatial scales is unusual. The specific nesting requirements of the queens and the necessity for queens to find a host quickly could lead to colonisation of the first suitable seedling encountered, promoting short dispersal distances. Nonetheless, dispersal distances of C. decamera queens may vary with habitat or host spatial distribution.     

GENETIC FINGERPRINT-INFERRED POPULATION SUBDIVISION AND SPATIAL GENETIC TESTS FOR ISOLATION BY DISTANCE AND ADAPTATION IN THE COASTAL PLANT LIMONIUM CAROLINIANUM

This paper examines two wild populations of Limonium carolinianum for population genetic subdivision and spatial patterns of genetic variation in an attempt to simultaneously test for both the action of local adaptation to tidal gradients and isolation by distance (IBD). A VNTR (variable number of tandem repeats) genetic “fingerprinting” marker was used to infer relatedness among mapped plants in two populations. Band sharing within and between populations estimated F'_ST, an approximate measure of F_ST. Regression models were used to analyze the relationship between band sharing and spatial separation in tidal elevation and horizontal distance, as well as the relationship of fecundity differences with band sharing and spatial distance. Populations differed in band size frequency distributions and mean number of bands per profile and, therefore, likely differed in effective population size. F'_ST was estimated at 0.0678 and was significantly greater than F'_ST among randomly constructed subpopulations. Band sharing decreased 0.13% per meter in one population but showed no significant relation to distance in the other. In the population with significant IBD band sharing increased with increasingly different tidal elevation, contrary to an adaptive hypothesis, possibly due to directional gene flow or drift. Deme sizes were approximately 25 meters and greater than 100 meters, spanning larger areas than the entire environmental gradient. Fecundity differences were not associated with spatial parameters or band sharing. Unequal potential maternal fecundity measured as variance in number of seeds per maternal family was a significant source of genetic sampling variance. The VNTR marker employed is capable of detecting adaptation as identity by descent in ecological time and is an appropriate method for estimating the net evolutionary fate of polygenic traits. The results show that the net balance between selection along an environmental gradient and the effects of IBD and unequal maternal fecundity favor genetic differentiation by random processes in populations of Limonium.     

Genetic diversity, gene flow and drift in Bavarian red deer populations (Cervus elaphus)

The red deer (Cervus elaphus) populationof Bavaria in Southern Germany was severelyreduced during the 19th century due toover-hunting. The species has since recoveredwithin designated areas. Subsequent habitatfragmentation presumably has changed thegenetic structure of Bavarian red deer.In order to assess the genetic diversity, weanalysed samples obtained from nine differentBavarian and two adjacent (Thueringen andCzech-Republic) red deer populations,genotyping 19 microsatellite loci. Our analysesrevealed moderate and significant differencesin diversity. Referring to assignment tests,the genetic differentiation of Bavarian reddeer was sufficient to assign an individual'sorigin to the correct population at an averageof 91.6%. The correlation of genetic andgeographic distance matrices revealed noevidence for isolation by distance. Thecoalescent model analysis suggests that thegenetic structure used to be characterized by adrift–gene flow equilibrium and is nowinfluenced by drift and disruption of the geneflow. Only three of the examined populationsshowed a probability of less than 10% that twogenes within these populations share a commonancestor (F _IS-value). Twopopulations had high F _IS values,indicating the influence of drift.Additionally, the intrapopulation indicesrevealed a low variability in thesepopulations. The estimated effective populationsizes (N _e) were generally in thesame range as the actual population sizes. Theinbreeding rates, based on the estimated N _e, and the inbreeding coefficientssuggested that the Bavarian red deerpopulations are in a stable state.     

Landscape genetic structure of Scirpus mariqueter reveals a putatively adaptive differentiation under strong gene flow in estuaries

Estuarine organisms grow in highly heterogeneous habitats, and their genetic differentiation is driven by selective and neutral processes as well as population colonization history. However, the relative importance of the processes that underlie genetic structure is still puzzling. Scirpus mariqueter is a perennial grass almost limited in the Changjiang River estuary and its adjacent Qiantang River estuary. Here, using amplified fragment length polymorphism (AFLP), a moderate‐high level of genetic differentiation among populations (range F_ST: 0.0310–0.3325) was showed despite large ongoing dispersal. FLOCK assigned all individuals to 13 clusters and revealed a complex genetic structure. Some genetic clusters were limited in peripheries compared with very mixing constitution in center populations, suggesting local adaptation was more likely to occur in peripheral populations. 21 candidate outliers under positive selection were detected, and further, the differentiation patterns correlated with geographic distance, salinity difference, and colonization history were analyzed with or without the outliers. Combined results of AMOVA and IBD based on different dataset, it was found that the effects of geographic distance and population colonization history on isolation seemed to be promoted by divergent selection. However, none‐liner IBE pattern indicates the effects of salinity were overwhelmed by spatial distance or other ecological processes in certain areas and also suggests that salinity was not the only selective factor driving population differentiation. These results together indicate that geographic distance, salinity difference, and colonization history co‐contributed in shaping the genetic structure of S. mariqueter and that their relative importance was correlated with spatial scale and environment gradient.     

Population differentiation or species formation across the Indian and the Pacific Oceans? An example from the brooding marine hydrozoan Macrorhynchia phoenicea

Assessing population connectivity is necessary to construct effective marine protected areas. This connectivity depends, among other parameters, inherently on species dispersal capacities. Isolation by distance (IBD ) is one of the main modes of differentiation in marine species, above all in species presenting low dispersal abilities. This study reports the genetic structuring in the tropical hydrozoan Macrorhynchia phoenicea α (sensu Postaire et al ., 2016a), a brooding species, from 30 sampling sites in the Western Indian Ocean and the Tropical Southwestern Pacific, using 15 microsatellite loci. At the local scale, genet dispersal relied on asexual propagation at short distance, which was not found at larger scales. Considering one representative per clone, significant positive F _IS values (from ?0.327*** to 0.411***) were found within almost all sites. Gene flow was extremely low at all spatial scales, among sites within islands (<10 km distance) and among islands (100 to >11,000 km distance), with significant pairwise F _ST values (from 0.035*** to 0.645***). A general pattern of IBD was found at the Indo‐Pacific scale, but also within ecoregions in the Western Indian Ocean province. Clustering and network analyses identified each island as a potential independent population, while analysis of molecular variance indicated that population genetic differentiation was significant at small (within island) and intermediate (among islands within province) spatial scales. As shown by this species, a brooding life cycle might be corollary of the high population differentiation found in some coastal marine species, thwarting regular dispersal at distances more than a few kilometers and probably leading to high cryptic diversity, each island housing independent evolutionary lineages.     

草履蚧不同寄主和地理种群遗传分化的RAPD分析

应用随机扩增多态性DNA(RAPD)技术对草履蚧保定、石家庄、邯郸16个不同寄主地理种群遗传多样性和种群分化进行研究,结果显示4个RAPD引物共扩增出41个多态性位点,多态位点比率为100%。遗传距离指数在0.701—0.4360,平均为0.2395。其中以邯郸枫杨和邯郸垂丝海棠为寄主的草履蚧种群遗传距离最小(0.0701);以石家庄紫叶李和邯郸木槿为寄主的种群遗传距离最大(0.4360)。遗传一致度系数在0.6466—0.9290。说明草履蚧不同种群遗传多样性丰富并存在遗传差异。聚类分析结果表明草履蚧种群遗传多样性同时受到寄主和地理因素的双重影响,且不同寄主草履蚧种群已产生明显的遗传分化。