Integrative approach revealed contrasting pattern of spatial structuring within urban and rural biotypes of Culex pipiens

Population structure of pests is an important issue when designing management strategies to optimize control measures. In this study, we investigated a spatial pattern of genetic and phenotypic variation within seven urban and within six rural populations of Culex pipiens from Vojvodina Province (Serbia) incorporating landscape genetic methods (using allozyme data) and wing size and shape (using geometric morphometric approach). Comparing rural samples, no strong genetic groupings of individuals were detected. Nevertheless, traditional approaches where individuals are pre‐assigned to populations, including F statistics and amova (analysis of molecular variance), revealed low, but significant genetic differentiation among samples. Similarly, phenotypic data (wing size and shape) indicated some level of heterogeneity among rural samples. Contrary to genetic homogeneity found within rural biotype, the individual‐based structuring characterized urban biotype. Geneland revealed the presence of two genetic clusters within urban group which is in concordance with F_ST and amova results. These results showed that sample from Novi Sad (NS) is a distinct genetic unit, which has been likely resulted in intensive insecticide use over several decades. Furthermore, phenotypic differentiation supported the existence of spatial structuring. Therefore, complementary use of molecular markers and phenotypic traits may be a powerful tool for revealing hidden spatial diversity within Cx. pipiens.     

Genetic and phenotypic variation in a colourful treefrog across five geographic barriers

Aim Understanding the patterns and processes underlying phenotype in a polytypic species provides key insights into microevolutionary mechanisms of diversification. The red‐eyed treefrog, Agalychnis callidryas, exhibits strong regional differentiation in colour pattern, corresponding to five admixed mitochondrial DNA clades. We evaluated spatial diversity patterns across multiple, putative barriers to examine the fine‐scale processes that mediate phenotypic divergence between some regions while maintaining homogeneity between others. Location We examined patterns of phenotypic diversification among 17 sites that span five putative biogeographic barriers in lower Central America (Costa Rica and Panama). Methods We tested the extent to which genetic distance (F_ST) derived from six multilocus nuclear genotypes covaried with measures of phenotypic distance (leg coloration) within and between biogeographic regions. We used linear regression analyses to determine the role of geographic and genetic factors in structuring spatial patterns of phenotypic diversity. Results The factors that best explained patterns of phenotypic diversity varied among biogeographic regions. We identified one geographic barrier that impeded gene exchange and resulted in concordant phenotypic divergence across the Continental Divide, isolating Caribbean and Pacific populations. Across Caribbean Costa Rican populations, one barrier structured phenotypic but not genetic diversity patterns, indicating a role for selection. In other regions, the putative barriers had no determining effect on either genetic or leg colour structure. Main conclusions The processes mediating the distribution and diversification of colour pattern in this polytypic, wide‐ranging treefrog varied among biogeographic regions. Spatially varying selection combined with the isolating effects of geographic factors probably resulted in the patchy distribution of colour diversity across Costa Rican and Panamanian populations.     

Geographical variation in wing polymorphism of the waterstrider Aquarius najas (Heteroptera,Gerridae)

The waterstrider Aquarius najas is wingless in Northern Europe, while winged individuals occur frequently in Central and Southern Europe. To test if the latitudinal difference is genetically controlled, we collected mature individuals from 10 different populations and raised their offspring in ‘common garden’ laboratory conditions. Half of these populations were from southern and the other half from central Finland. Daylength and temperature do influence wing development among other species of waterstriders, and thus we maintained a similar short daylength and warm conditions for all populations. These conditions should be favourable for wing development in general. Among laboratory-bred individuals several winged individuals appeared, and their proportion varied between populations. The relative frequency of winged individuals was highest in the southern populations. Thus, apart from phenotypic plasticity there seems to be some genetic control over the occurrence of wings, and the latitudinal trend coincides with the direction in natural populations over a larger European scale. Overwinter survival in our laboratory conditions was higher among the wingless individuals. The survival cost may explain why the proportion of winged individuals was lower in the northern populations with more extreme overwintering conditions than in the southern ones.     

Regional and local spatial genetic structure of Siberian primrose populations in Northern Europe

We have investigated the local and regional scale genetic structure of Siberian primrose (Primula nutans) populations in Northern Europe. The genetic diversity and structure of fifteen populations sampled from the Bothnian Bay in Finland, the Barents Sea in Norway and the White Sea in Russia were assessed using eleven microsatellite markers. We investigated the distribution of genetic variation within and between populations, and studied the local genetic structure using spatial autocorrelation analysis. We found very low genetic and allelic diversity in the Bothnian Bay and Barents Sea populations, and only slightly higher in the White Sea population. The level of genetic differentiation between the regions was very high, whereas differentiation between the populations within the regions was moderate. We found no spatial structuring of populations in any region suggesting efficient dispersal on a local scale. Clonal reproduction seemed to have no effect on genetic structure.     

Temporal patterns of genetic and phenotypic variation in the epidemiologically important drone fly, Eristalis tenax

Eristalis tenax L. (Diptera: Syrphidae) is commonly known as the drone fly (adult) or rat‐tailed maggot (immature). Both adults and immature stages are identified as potential mechanical vectors of mycobacterial pathogens, and early‐stage maggots cause accidental myiasis. We compared four samples from Mount Fru?ka Gora, Serbia, with the aim of obtaining insights into the temporal variations and sexual dimorphism in the species. This integrative approach was based on allozyme loci, morphometric wing parameters (shape and size) and abdominal colour patterns. Consistent sexual dimorphism was observed, indicating that male specimens had lighter abdomens and smaller and narrower wings than females. The distribution of genetic diversity at polymorphic loci indicated genetic divergence among collection dates. Landmark‐based geometric morphometrics revealed, contrary to the lack of divergence in wing size, significant wing shape variation throughout the year. In addition, temporal changes in the frequencies of the abdominal patterns observed are likely to relate to the biology of the species and ecological factors in the locality. Hence, the present study expands our knowledge of the genetic diversity and phenotypic plasticity of E. tenax. The quantification of such variability represents a step towards the evaluation of the adaptive potential of this species of medical and epidemiological importance.     

Transcontinental migratory connectivity predicts parasite prevalence in breeding populations of the European barn swallow

Parasites exert a major impact on the eco‐evolutionary dynamics of their hosts and the associated biotic environment. Migration constitutes an effective means for long‐distance invasions of vector‐borne parasites and promotes their rapid spread. Yet, ecological and spatial information on population‐specific host–parasite connectivity is essentially lacking. Here, we address this question in a system consisting of a transcontinental migrant species, the European barn swallow (Hirundo rustica) which serves as a vector for avian endoparasites in the genera Plasmodium, Haemoproteus and Leucocytozoon. Using feather stable isotope ratios as geographically informative markers, we first assessed migratory connectivity in the host: Northern European breeding populations predominantly overwintered in dry, savannah‐like habitats in Southern Africa, whereas Southern European populations were associated with wetland habitats in Western Central Africa. Wintering areas of swallows breeding in Central Europe indicated a migratory divide with both migratory programmes occurring within the same breeding population. Subsequent genetic screens of parasites in the breeding populations revealed a link between the host's migratory programme and its parasitic repertoire: controlling for effects of local breeding location, prevalence of Africa‐transmitted Plasmodium lineages was significantly higher in individuals overwintering in the moist habitats of Western Central Africa, even among sympatrically breeding individuals with different overwintering locations. For the rarer Haemoproteus parasites, prevalence was best explained by breeding location alone, whereas no clear pattern emerged for the least abundant parasite Leucocytozoon. These results have implications for our understanding of spatio‐temporal host–parasite dynamics in migratory species and the spread of avian borne diseases.     

Surprising diversity in the Pannonian populations of Marsh Fritillary (Euphydryas aurinia,Lepidoptera: Nymphalidae): Morphometric and molecular aspects

Since genetic variation is the basis of evolutionary potential of a species, its structure needs to be understood. Thus, the aim of this study was to analyze and contrast the structure of genetic and phenotypic variation in the Euphydryas aurinia populations of southeastern central Europe. Genetic variation was studied by two types of molecular genetic markers: mtDNA COI sequences and allozymes. As the great hiatus in the European distribution of E. aurinia is located in the central part of the Carpathian Basin, we expected that the populations East and West to this gap would be highly differentiated. Populations of Central Transdanubia actually represent the easternmost margin of the West European distribution of E. aurinia. In view of the peripheral position of these populations, we supposed to find some genetic sign of local adaptation, as a consequence of diversifying selection and an increased level of fluctuating asymmetry as a result of environmental stress. The analyses of the molecular genetic markers revealed a basic East–West differentiation among the populations of southeastern central Europe which was further structured in the western part of the study area. The results suggested that the genetic differentiation between the two western regions is probably the consequence of diversifying selection. The pattern of phenotypic differentiation among the western populations, however, was different. A geographic cline was revealed (decreasing wing size) toward the eastern margin of the distribution in parallel with increasing fluctuating asymmetry. The conservation inferences of the results are considered.     

Seasonal wing colour plasticity varies dramatically between buckeye butterfly populations in different climatic zones

1. In the present study, how seasonal wing colour plasticity in buckeye butterflies (Junonia coenia Hübner) differs between populations in different climatic regions, and whether these differences are explained by regional environmental differences or reflect genetic divergences in plasticity is addressed. 2. Using museum specimen data, it is shown that buckeye wing colour variation is much greater in populations from the humid and subtropical climates of the eastern U.S.A. than in populations from the desert and mediterranean climates of the western U.S.A. 3. Museum specimen data further show that wing colour in eastern populations is strongly correlated with seasonal variation in day length and temperature, whereas wing colour in western populations is only weakly associated with these cues. 4. Controlled incubator experiments comparing Southern California and North Carolina populations suggest that regional differences in wing pattern variation are attributable to dramatically increased robustness to environmental variation in western populations. 5. Together these experiments show that while phenotypic variation can be influenced by environmental cues, the range of this variation can genetically diverge between populations in different regions.     

Genetic and phenotypic variation in central and northern European populations of Aedes (Aedimorphus) vexans (Meigen, 1830) (Diptera,Culicidae)

The floodwater mosquito Aedes vexans can be a massive nuisance in the flood plain areas of mainland Europe, and is the vector of Tahyna virus and a potential vector of Dirofilaria immitis. This epidemiologically important species forms three subspecies worldwide, of which Aedes vexans arabiensis has a wide distribution in Europe and Africa. We quantified the genetic and phenotypic variation in Ae. vexans arabiensis in populations from Sweden (northern Europe), Hungary, and Serbia (central Europe). A landscape genetics approach (F_ST, STRUCTURE, BAPS, GENELAND) revealed significant differentiation between northern and southern populations. Similar to genetic data, wing geometric morphometrics revealed two different clusters, one made by Swedish populations, while another included Hungarian and Serbian populations. Moreover, integrated genetic and morphometric data from the spatial analysis suggested groupings of populations into three clusters, one of which was from Swedish and Hungarian populations. Data on spatial analysis regarding an intermediate status of the Hungarian population was supported by observed Isolation‐by‐Distance patterns. Furthermore, a low proportion of interpopulation vs intrapopulation variance revealed by AMOVA and low‐to‐moderate F_ST values on a broader geographical scale indicate a continuous between‐population exchange of individuals, including considerable gene flow on the regional scale, are likely to be responsible for the maintenance of the observed population similarity in Aе. vexans. We discussed data considering population structure in the light of vector control strategies of the mosquito from public health importance.     

Short‐distance migration of Wrynecks Jynx torquilla from Central European populations

European Wrynecks Jynx torquilla torquilla have generally been considered to be long‐distance Palaearctic–African migrants that spend the non‐breeding season in Sahelian Africa, where they have been reported regularly. Results from tracking individual birds showed that Wrynecks from two Central European populations migrated only relatively short distances to the Iberian Peninsula and northwestern Africa (c. 1500 km and 3000 km, respectively), compared with a minimum distance of about 4500 km to Sahelian Africa. Additionally, differences in wing lengths of populations from Central and Northern Europe support the idea of leap‐frog migration, populations from Northern Europe being long‐distance migrants with a non‐breeding distribution in Sahelian Africa.     

Y chromosome haplotype distribution of brown bears (Ursus arctos) in Northern Europe provides insight into population history and recovery

High‐resolution, male‐inherited Y‐chromosomal markers are a useful tool for population genetic analyses of wildlife species, but to date have only been applied in this context to relatively few species besides humans. Using nine Y‐chromosomal STRs and three Y‐chromosomal single nucleotide polymorphism markers (Y‐SNPs), we studied whether male gene flow was important for the recent recovery of the brown bear (Ursus arctos) in Northern Europe, where the species declined dramatically in numbers and geographical distribution during the last centuries but is expanding now. We found 36 haplotypes in 443 male extant brown bears from Sweden, Norway, Finland and northwestern Russia. In 14 individuals from southern Norway from 1780 to 1920, we found two Y chromosome haplotypes present in the extant population as well as four Y chromosome haplotypes not present among the modern samples. Our results suggested major differences in genetic connectivity, diversity and structure between the eastern and the western populations in Northern Europe. In the west, our results indicated that the recovered population originated from only four male lineages, displaying pronounced spatial structuring suggestive of large‐scale population size increase under limited male gene flow within the western subpopulation. In the east, we found a contrasting pattern, with high haplotype diversity and admixture. This first population genetic analysis of male brown bears shows conclusively that male gene flow was not the main force of population recovery.     

Testing evolutionary hypotheses for phenotypic divergence using landscape genetics

Understanding the evolutionary causes of phenotypic variation among populations has long been a central theme in evolutionary biology. Several factors can influence phenotypic divergence, including geographic isolation, genetic drift, divergent natural or sexual selection, and phenotypic plasticity. But the relative importance of these factors in generating phenotypic divergence in nature is still a tantalizing and unresolved problem in evolutionary biology. The origin and maintenance of phenotypic divergence is also at the root of many ongoing debates in evolutionary biology, such as the extent to which gene flow constrains adaptive divergence ( Garant et al. 2007 ) and the relative importance of genetic drift, natural selection, and sexual selection in initiating reproductive isolation and speciation ( Coyne & Orr 2004 ). In this issue, Wang & Summers (2010) test the causes of one of the most fantastic examples of phenotypic divergence in nature: colour pattern divergence among populations of the strawberry poison frog (Dendrobates pumilio) in Panama and Costa Rica ( Fig. 1 ). This study provides a beautiful example of the use of the emerging field of landscape genetics to differentiate among hypotheses for phenotypic divergence. Using landscape genetic analyses, Wang & Summers were able to reject the hypotheses that colour pattern divergence is due to isolation‐by‐distance (IBD) or landscape resistance. Instead, the hypothesis left standing is that colour divergence is due to divergent selection, in turn driving reproductive isolation among populations with different colour morphs. More generally, this study provides a wonderful example of how the emerging field of landscape genetics, which has primarily been applied to questions in conservation and ecology, now plays an essential role in evolutionary research.

Figure 1 Open in figure viewer PowerPoint Divergent colour morphs observed among populations of the strawberry poison frog, Dendrobates pumilio. Frogs are from San Cristobal (upper left), Cerro Brujo (upper right), Bastimentos (lower right), and Agua (lower left).     

Cryptic genetic and wing pattern diversity in a mimetic Heliconius butterfly

Despite rampant colour pattern diversity in South America, Heliconius erato exhibits a ‘postman’ wing pattern throughout most of Central America. We examined genetic variation across the range of H. erato, including dense sampling in Central America, and discovered a deep genetic break, centred on the mountain range that runs through Costa Rica. This break is characterized by a novel mitochondrial lineage, which is nearly fixed in northern Central America, that branches basal to all previously described mitochondrial diversity in the species. Strong genetic differentiation also appears in Z‐linked and autosomal markers, and it is further associated with a distinct, but subtle, shift in wing pattern phenotype. Comparison of clines in wing phenotype, mtDNA and nuclear markers indicate they are all centred on the mountains dividing Costa Rica, but that cline width differs among data sets. Phylogeographical analyses, accounting for this new diversity, rewrite our understanding of mimicry evolution in this system. For instance, these results suggest that H. erato originated west of the Andes, perhaps in Central America, and as many as 1 million years before its co‐mimic, H. melpomene. Overall our data indicate that neutral genetic markers and colour pattern loci are congruent and converge on the same hypothesis—H. erato originated in northwest South America or Central America with a ‘postman’ phenotype and then radiated into the wealth of colour patterns present today.     

Discordant patterns of evolutionary differentiation in two Neotropical treefrogs

Comparative studies of codistributed taxa test the degree to which historical processes have shaped contemporary population structure. Discordant patterns of lineage divergence among taxa indicate that species differ in their response to common historical processes. The complex geologic landscape of the Isthmus of Central America provides an ideal setting to test the effects of vicariance and other biogeographic factors on population history. We compared divergence patterns between two codistributed Neotropical frogs ( Dendropsophus ebraccatus and Agalychnis callidryas ) that exhibit colour pattern polymorphisms among populations, and found significant differences between them in phenotypic and genetic divergence among populations. Colour pattern in D. ebraccatus did not vary with genetic or geographic distance, while colour pattern co-varied with patterns of gene flow in A. callidryas . In addition, we detected significant species differences in the phylogenetic history of populations, gene flow among them, and the extent to which historical diversification and recent gene flow have been restricted by five biogeographic barriers in Costa Rica and Panama. We inferred that alternate microevolutionary processes explain the unique patterns of diversification in each taxon. Our study underscores how differences in selective regimes and species-typical ecological and life-history traits maintain spatial patterns of diversification.     

Genetic structuring in Andean landlocked populations of Galaxias maculatus: effects of biogeographic history

Aim To test whether the genetic diversity of diadromous and landlocked populations of the small puyen Galaxias maculatus (known as jollytail in Australia and inanga in New Zealand) follow the same structuring patterns observed for migratory and non‐migratory species of the genus Galaxias. This work also aimed to test whether the genetic structuring of a group of populations could be predicted from differences in the geomorphologic history of the region they inhabit. Location Eight landlocked populations were sampled from cold‐temperate lakes in north‐western Patagonia. The study area could be split latitudinally into two sectors that differed in their geomorphology, each of them hosting four populations. The southern sector shows evidence of a higher degree of glacial coverage, and the lakes are probably remnants of a big proglacial palaeolake. Lakes in the northern sector, on the other hand, suggest no common origin. Results Significant genetic structuring was found among the studied populations (Θ = 0.188), being the highest value reported to date for the species. Significant correlation was found between genetic diversity and lake area and perimeter. Diversity also showed a slight latitudinal variation suggesting the presence of genetically distinct groups of populations. The comparison of populations from the two geographical sectors showed that those from the north had a higher diversity, more private alleles and strong structuring, while those from the south were less diverse and much more homogeneous. Main conclusions Non‐migratory populations of G. maculatus show much higher values of genetic structuring than those reported for diadromous populations. This follows the pattern seen when comparing migratory and non‐migratory species of Galaxias. This agrees with population genetics theory which predicts that restricted gene flow would result in greater among‐population divergence. Also, differences between northern and southern populations agreed with what was predicted by the geomorphologic history of the study area. During the Last Glacial Maximum ice cover in that region may have reduced the habitat of G. maculatus to a refuge with an impoverished gene pool. When the ice receded, leaving a great proglacial lake, that former population expanded and became fragmented after water levels descended. This resulted in present day lakes harbouring homogeneous populations with reduced diversity. The northern sector, in contrast, was less affected by glaciers, resulting in more geomorphologically stable lakes holding genetically diverse populations.     

Genetic variability of fragmented stands of pedunculate oak (Quercus robur) in Finland

The genetic structure of 33 natural Quercus robur stands in Finland was studied using 13 allozyme loci to analyze the effects of fragmentation in a wind-pollinated tree species. The present fragmented and discontinuous distribution of oak is a result of both short-term human impact and long-term climatic and geological change, including post-glacial land uplift. In accordance with general expectations, genetic diversity in small populations was lower than that in large populations, and differentiation among small populations was higher than that among large populations. Heterozygote deficiency was more pronounced in large populations, which is proposed to be a Wahlund effect created by either spatial sub-structuring or the existence of synchronized flowering lineages. Also genetic differentiation was higher and diversity lower in Finland than the estimates reported for Central Europe. There were differences in the genetic structure on sites of different geological age. We suggest that on most geologically old sites drift has a prominent effect whereas on younger sites also founder effects may be important.     

The recolonization of Europe by brown bears Ursus arctos Linnaeus, 1758 after the Last Glacial Maximum

1. At the end of the Last Glacial Maximum brown bears Ursus arctos recolonized the glacial landscape of Central and Northern Europe faster than all other carnivorous mammal species of the Holocene fauna. Ursus arctos was recorded in Northern Europe from the beginning of the Late-Glacial. The recolonization of northern Central Europe may have taken place directly after the maximum glaciation. The distribution of the brown bear was restricted to glacial refugia only during the Last Glacial Maximum, for probably no more than 10 000 years. 2. Genetic analyses have suggested three glacial refugia for the brown bear: the Iberian Peninsula, the Italian Peninsula and the Balkans. Subfossil records of Ursus arctos from north-western Moldova as well as reconstructed environmental conditions during the Last Glacial Maximum in this area suggest to us a fourth glacial refuge for the brown bear. Because of its connection to the Carpathians, we designate this as the ‘Carpathian refuge’. 3. Due to the low genetic distance between brown bears of northern Norway, Finland, Estonia, north-eastern Russia and the northern Carpathians (the so-called eastern lineage), the Carpathians were considered the geographical origin of the recolonization of these regions. During the recolonization of northern Europe the brown bear probably reached these areas rapidly from the putative Carpathian refuge.     

Genetic constraints on wing pattern variation in Lycaeides butterflies: A case study on mapping complex,multifaceted traits in structured populations

Patterns of phenotypic variation within and among species can be shaped and constrained by trait genetic architecture. This is particularly true for complex traits, such as butterfly wing patterns, that consist of multiple elements. Understanding the genetics of complex trait variation across species boundaries is difficult, as it necessitates mapping in structured populations and can involve many loci with small or variable phenotypic effects. Here, we investigate the genetic architecture of complex wing pattern variation in Lycaeides butterflies as a case study of mapping multivariate traits in wild populations that include multiple nominal species or groups. We identify conserved modules of integrated wing pattern elements within populations and species. We show that trait covariances within modules have a genetic basis and thus represent genetic constraints that can channel evolution. Consistent with this, we find evidence that evolutionary changes in wing patterns among populations and species occur in the directions of genetic covariances within these groups. Thus, we show that genetic constraints affect patterns of biological diversity (wing pattern) in Lycaeides, and we provide an analytical template for similar work in other systems.     

Hybridization and transgressive exploration of colour pattern and wing morphology in Heliconius butterflies

Hybridization can generate novel phenotypes distinct from those of parental lineages, a phenomenon known as transgressive trait variation. Transgressive phenotypes might negatively or positively affect hybrid fitness, and increase available variation. Closely related species of Heliconius butterflies regularly produce hybrids in nature, and hybridization is thought to play a role in the diversification of novel wing colour patterns despite strong stabilizing selection due to interspecific mimicry. Here, we studied wing phenotypes in first‐ and second‐generation hybrids produced by controlled crosses between either two co‐mimetic species of Heliconius or between two nonmimetic species. We quantified wing size, shape and colour pattern variation and asked whether hybrids displayed transgressive wing phenotypes. Discrete traits underlain by major‐effect loci, such as the presence or absence of colour patches, generate novel phenotypes. For quantitative traits, such as wing shape or subtle colour pattern characters, hybrids only exceed the parental range in specific dimensions of the morphological space. Overall, our study addresses some of the challenges in defining and measuring phenotypic transgression for multivariate traits and our data suggest that the extent to which transgressive trait variation in hybrids contributes to phenotypic diversity depends on the complexity and the genetic architecture of the traits.     

Multiple-scaled spatial genetic structures of <Emphasis Type="Italic">Fraxinus mandshurica</Emphasis> over a riparian–mountain landscape in Northeast China

Landscape genetics increasingly focuses on the way in which landscape features cause the fragmentation of lineages of terrestrial organisms. However, landscape features can also provide functional connectivity or corridors, enhancing the dispersal of plant populations, particularly the case in riparian habitat. Unfortunately, recent research in tree genetics has paid little attention to this role. To examine the possible effects of landscape connectivity on the current population genetic distribution of Fraxinus mandshurica and to provide insights into conserving the local genetic diversity for this endangered tree species, we used nine nuclear microsatellite loci to examine the spatial genetic structure of F. mandshurica at multiple-scales over a riparian–mountain landscape in Northeast China. F-statistics indicated that the magnitude of among-population genetic differentiation was significantly higher between the riparian and mountain habitats than within the riparian habitat. Spatial analysis of molecular variance and principal coordinate analysis consistently revealed that this species exhibited a clear landscape genetic structure between the riparian and mountain habitats, despite no significant isolation by distance pattern being identified by the Mantel test. Spatial autocorrelation analysis further demonstrated significant, positive fine-scale spatial genetic structure among individuals over short distances (<80 m) in each mountain population. Conversely, no spatial genetic structures were identified within and among the riparian populations. Overall, the results suggest that seed dispersal is very low among mountain populations; however seed transport is probably enhanced by a secondary phase of hydrochory (water-dispersal) among riparian populations during flooding. Despite this, there was no significant accumulation of genetic diversity in downstream populations along the main channel. This result suggests that hydrochory is not sufficient to produce a clear unidirectional gene flow along the water course, although it may impede the development of spatial genetic structuring within and among riparian populations.