Restricted Gene Flow Research Articles

Multiple paternally inherited chloroplast capture events associated with Taxus speciation in the Hengduan Mountains

Mountainous regions provide a multitude of habitats and opportunities for complex speciation scenarios. Hybridization leading to chloroplast capture, which can be revealed by incongruent phylogenetic trees, is one possible outcome.Four allopatric Taxus lineages (three species and an undescribed lineage) from the Hengduan Mountains, southwest China, exhibit conflicting phylogenetic relationships between nuclear and chloroplast phylogenies. Here, we use multi-omic data at the population level to investigate their historical speciation processes.Population genomic analysis based on ddRAD-seq data revealed limited contemporary inter-specific gene flow involving only populations located close to another species.In a historical context, chloroplast and nuclear data (transcriptome) consistently showed conflicting phylogenetic relationships for T. florinii and the Emei type lineage. ILS and chloroplast recombination were excluded as possible causes, and transcriptome and ddRAD-seq data revealed an absence of the mosaic nuclear genomes that characterize hybrid origin scenarios.Therefore, T. florinii appears to have originated when a lineage of T. florinii captured the T. chinensis plastid type, whereas plastid introgression in the opposite direction generated the Emei Type. All four species have distinct ecological niche based on community investigations and ecological niche analyses.We propose that the origins of both species represent very rare examples of chloroplast capture events despite the paternal cpDNA inheritance of gymnosperms. Specifically, allopatrically and/or ecologically diverged parental species experienced a rare secondary contact, subsequent hybridization and reciprocal chloroplast capture, generating two new lineages, each of which acquired a unique ecological niche. These events might have been triggered by orogenic activities of the Hengduan Mountains and an intensification of the Asian monsoon in the late Miocene, and may represent a scenario more common in these mountains than presently known.

The genetic structuring in pollinating wasps of Ficus hispida in continental Asia.

The interaction between figs and fig wasps provides a striking example of obligate brood site pollination mutualism. Monoecious figs, constituting independent radiations in each tropical biome, are present in significant proportions worldwide, but in continental Asia, dioecious figs have diverged into various niches, making the region's assemblage remarkably diverse. However, the reproductive success of figs and fig wasps largely depends on the fig wasp dispersal process. Monoecious fig pollinators in continental Asian tropical rain forests exhibit high gene flow of the plant, while many dioecious fig pollinators have a more restricted gene flow. However, there are limited studies on the genetic structure of dioecious Ficus pollinators that pollinate figs with intermediate gene flow. Here, we used molecular methods to investigate the genetic structure of pollinating wasps of the widely distributed dioecious Ficus hispida in China and Southeast Asia. Sequence data from two gene regions were used: the mitochondrial protein-coding gene cytochrome c oxidase subunit I (COI) and the nuclear 28S genes. Both molecular and morphological results support two fig wasp species at our sampling sites. Our findings suggest that for widely sympatric Ficus species in continental Asia, monoecious figs presenting long gene glow have the fewest fig wasp species, followed by dioecious figs presenting intermediate gene flow, and dioecious figs presenting local gene flow have the most fig wasp species.

Genomic analysis reveals complex population structure within the smooth newt, Lissotriton vulgaris, in Central Europe.

Species with wide-range distributions usually display high genetic variation. This variation can be partly explained by historical lineages that were temporally isolated from each other and are back into secondary reproductive contact, and partly by local adaptations. The smooth newt (Lissotriton vulgaris) is one of the most widely distributed amphibians species across Eurasia and forms a species complex with a partially overlapping distribution and morphology. In the present study, we explored the population genomic structure of smooth newt lineages in the Carpathian Basin (CB) relying on single-nucleotide polymorphisms. Our dataset included new and previously published data to study the secondary contact zone between lineages in the CB and also tested for the barrier effect of rivers to gene flow between these lineages. We confirmed the presence of the South L. v. vulgaris Lineage distributed in Transdanubia and we provided new distribution records of L. v. ampelensis inhabiting the eastern territories of the CB. High genetic diversity of smooth newts was observed, especially in the North Hungarian Mountains and at the interfluves of the main rivers in the South with four distinct lineages of L. v. vulgaris and one lineage of L. v. ampelensis showing a low level of admixture with the spatially closest L. v. vulgaris lineage. Moreover, admixture detected at the interfluve of the main rivers (i.e. Danube and Tisza) suggested a secondary contact zone in the area. Finally, we found that the river Danube has a very weak effect on population divergence, while the river Tisza is a geographical barrier limiting gene flow between smooth newt lineages. As the range boundaries of L. v. vulgaris and L. v. ampelensis in the CB coincide with the river Tisza, our study underpins the influence of rivers in lineage diversification.

Novel insights into symbiont population structure: Globe-trotting avian feather mites contradict the specialist-generalist variation hypothesis.

Researchers often examine symbiont host specificity as a species-level pattern, but it can also be key to understanding processes occurring at the population level, which are not as well understood. The specialist-generalist variation hypothesis (SGVH) attempts to explain how host specificity influences population-level processes, stating that single-host symbionts (specialists) exhibit stronger population genetic structure than multi-host symbionts (generalists) because of fewer opportunities for dispersal and more restricted gene flow between populations. However, this hypothesis has not been tested in systems with highly mobile hosts, in which population connectivity may vary temporally and spatially. To address this gap, we tested the SGVH on proctophyllodid feather mites found on migratory warblers (family Parulidae) with contrasting host specificities, Amerodectes protonotaria (a host specialist of Protonotaria citrea) and A. ischyros (a host generalist of 17 parulid species). We used a pooled-sequencing approach and a novel workflow to analyse genetic variants obtained from whole genome data. Both mite species exhibited fairly weak population structure overall, and contrary to predictions of the SGVH, the generalist was more strongly structured than the specialist. These results may suggest that specialists disperse more freely among conspecifics, whereas generalists sort according to geography. Furthermore, our results may reflect an unexpected period for mite transmission - during the nonbreeding season of migratory hosts - as mite population structure more closely reflects the distributions of hosts during the nonbreeding season. Our findings alter our current understanding of feather mite biology and highlight the potential for studies to explore factors driving symbiont diversification at multiple evolutionary scales.

Limited population genetic structure in the littoral gastropod Nerita tessellata (Neritimorpha, Neritidae) suggests high dispersal across the Caribbean Sea

The Caribbean Sea is characterized by an incredible biodiversity, including several endemic mollusk species, most of which have larval dispersal as their main mechanism of gene flow. It is known that the present-day population structure of a species reflects the combination of oceanographic currents, life-history traits, and historical events. Nerita tessellata is a common gastropod species in coastal, rocky, and exposed shores across the Caribbean Sea; however, little is known about the mechanisms that have shaped its distribution. Here, we tested potential barriers to gene flow and the associated genetic structure of N. tessellata in 12 populations across the Caribbean using digest restriction-site associated DNA sequencing (ddRAD-seq). Likewise, we evaluated demographic history and migration patterns through two coalescence approaches using Approximate Bayesian Computation (ABC) combined with supervised machine learning. The global analysis, based on 26,421 single nucleotide polymorphism (SNP) markers derived from ddRAD-seq, revealed low nucleotide diversity with high levels of gene flow and a lack of significant population differentiation within the survey area, indicating that N. tessellata is panmictic across the Caribbean Sea. Our results reveal that a pattern of north to south movement along Caribbean currents could potentially explain the limited genetic structure and high gene flow among N. tessellata populations. The scenarios simulated with ABC showed a constant effective population size for the ancestral population. Additionally, the four populations tested experienced demographic expansions that date to the Pleistocene. An extended pelagic larval stage could explain the large-scale genetic uniformity of this species across its distribution. Our findings contribute to understanding genetic diversity and population structure in a common gastropod within the Caribbean Sea.

Combining RADseq and contact zone analysis to decipher cryptic diversification in reptiles: Insights from the Spiny‐footed Lizard (Reptilia, Lacertidae)

AbstractUncertainties on species taxonomy and distribution are major factors hampering efficient conservation planning in the current context of biodiversity erosion, even concerning widespread and abundant species in relatively well‐studied regions. Species delimitation have long been based on phylogenetic analyses of a small number of standard markers, but accurate lineage identification through this approach can be hampered by incomplete lineage sorting, introgression or isolation by distance. In that context, analyses of introgression patterns at secondary contact zones offer an interesting alternative by allowing a direct estimation of reproductive isolation, especially when using genome‐wide markers. Here, we investigated a contact zone between two genetic groups of the Spiny‐footed Lizard Acanthodactylus erythrurus (Schinz, 1833) in Morocco, whose status as separate lineages remained disputed in previous multilocus studies. Based on thousands of genome‐wide markers obtained through a RADseq approach, we confirmed that they represent distinct evolutionary lineages. Furthermore, the transition at their contact zone was very steep, with spatially restricted gene flow, highlighting levels of reproductive isolation consistent with species‐level lineages. Our study further illustrates the power of RADseq‐based studies of contact zones to understand cryptic diversity in non‐model organisms.

Unity in diversity: morphological and genetic variability, integrative systematics, and phylogeography of the widespread nudibranch mollusc Onchidoris muricata

Onchidoris muricata (Gastropoda: Nudibranchia: Onchidorididae) is a well-known nudibranch species, which has a wide amphiboreal range confirmed by molecular data. However, O. muricata shows a high degree of variation in external morphology among distant populations, which may indicate the presence of cryptic diversity within this species. There are also two closely related species with an unconfirmed taxonomic status, which were recently described from the northwestern Pacific based on morphological data. In this paper we study the taxonomic status and population structure of O. muricata based on an integrative approach combining morphological and molecular data and using O. muricata as a model we explore issues of boreal marine fauna connectivity and glaciation-driven isolation. The external morphology, spicule composition, and features of the buccal armature and the reproductive system were studied using light microscopy, scanning electron microscopy and mCT scan technology. The molecular study included various population genetic analyses as well as divergence time estimation and ancestral area reconstruction analyses. Onchidoris muricata represents a true amphiboreal species, which shows a high degree of heterogeneity in morphological characters, especially in the radular morphology and in features of the reproductive system. Our new data question the validity of the North-West Pacific species O. macropompa and O. pavli as the morphology of both these species fall within the phenotypic diversity of O. muricata. Although our sampling does not include the type localities of these two species, the observed morphological variability in O. muricata and the lack of molecular data for the North Pacific species O. macropompa and O. pavli suggest the latter two species are in fact part of O. muricata morphological diversity. Phylogeographic analyses indicate a genetic separation of the North Pacific and North Atlantic-Arctic populations of O. muricata, suggesting restricted gene flow between these areas. We show that this divergence may be a result of glacial cycles during the late Pleistocene, which were a key factor in the reduction of gene flow across the Arctic Ocean. Our molecular results also suggest that the White Sea population experienced a bottleneck event during the last Glacial Maximum.

Neutral genetic diversity follows a latitudinal gradient in the endangered plant Arnica montana L.: a range-wide study

Arnica montana is a clonal, self-incompatible herb of economic and intrinsic ecological value which is declining in large parts of its range. With the employment of microsatellite markers, we characterized the population structure and distribution of genetic diversity of 40 populations of A. montana sampled throughout Europe. We detected a clear geographical pattern of isolation and strong population structure, indicating limited gene flow. We also observed a negative latitudinal gradient in genetic diversity. Such patterns can be explained by paleo-historical colonization routes following the last glacial maximum, with regions characterized by higher genetic diversity corresponding to former glacial refugia. We recommend the implementation of conservation measures such as assisted gene flow in the populations characterized by low genetic diversity under consideration of the observed population structure. For the populations where high levels of genetic diversity are still retained, we recommend the maintenance of suitable habitat conditions. Our study emphasises the importance of conducting large-scale population genetic studies that consider postglacial recolonization history when planning active conservation measures such as assisted gene flow.

Heterogeneous microgeographic genetic structure of the common cockle (Cerastoderma edule) in the Northeast Atlantic Ocean: biogeographic barriers and environmental factors.

Knowledge of genetic structure at the finest level is essential for the conservation of genetic resources. Despite no visible barriers limiting gene flow, significant genetic structure has been shown in marine species. The common cockle (Cerastoderma edule) is a bivalve of great commercial and ecological value inhabiting the Northeast Atlantic Ocean. Previous population genomics studies demonstrated significant structure both across the Northeast Atlantic, but also within small geographic areas, highlighting the need to investigate fine-scale structuring. Here, we analysed two geographic areas that could represent opposite models of structure for the species: (1) the SW British Isles region, highly fragmented due to biogeographic barriers, and (2) Galicia (NW Spain), a putative homogeneous region. A total of 9250 SNPs genotyped by 2b-RAD on 599 individuals from 22 natural beds were used for the analysis. The entire SNP dataset mostly confirmed previous observations related to genetic diversity and differentiation; however, neutral and divergent SNP outlier datasets enabled disentangling physical barriers from abiotic environmental factors structuring both regions. While Galicia showed a homogeneous structure, the SW British Isles region was split into four reliable genetic regions related to oceanographic features and abiotic factors, such as sea surface salinity and temperature. The information gathered supports specific management policies of cockle resources in SW British and Galician regions also considering their particular socio-economic characteristics; further, these new data will be added to those recently reported in the Northeast Atlantic to define sustainable management actions across the whole distribution range of the species.

Limitation of gene flow by distance in the common yellow jasmine (Chrysojasminum fruticans, Oleaceae): implications for the study of its mating strategies

Abstract The common yellow jasmine (Chrysojasminum fruticans, Oleaceae) is a distylous shrub occurring in the wild in south-western Europe and the Mediterranean Basin. Little is known about the genetics of its populations and such information would be necessary to investigate its spread and mating strategies. Here, the organization of its genetic diversity was investigated among and between 13 populations from southern France, including a 35-year-old experimental plot (‘CEFE’, CNRS Montpellier). Markers (microsatellites and indels) were developed to screen polymorphisms in nuclear, chloroplast, and mitochondrial genomes. Low linkage disequilibrium was observed between chloroplast and mitochondrial haplotypes probably resulting from paternal leaks in their inheritance as reported in other species of tribe Jasmineae. Yet, analyses of 36 progenies issued from parents with distinct chloroplast and/or mitochondrial DNA haplotypes only revealed a maternal contribution. Natural populations of C. fruticans are moderately to highly differentiated at the regional scale with a strong isolation-by-distance pattern detected on nuclear data, indicating limited gene flow. An isolated site (‘Moulis’), located on the marginal distribution area, was remarkably genetically depauperate and highly differentiated from other populations. Further studies on the variation of mating strategies in C. fruticans should consider populations with contrasting patterns of genetic diversity. The artificial ‘CEFE’ population also offers opportunities for experiments in a closed system.

High-coverage genome of the Tyrolean Iceman reveals unusually high Anatolian farmer ancestry

The Tyrolean Iceman is known as one of the oldest human glacier mummies, directly dated to 3350-3120 calibrated BCE. A previously published low-coverage genome provided novel insights into European prehistory, despite high present-day DNA contamination. Here, we generate a high-coverage genome with low contamination (15.3×) to gain further insights into the genetic history and phenotype of this individual. Contrary to previous studies, we found no detectable Steppe-related ancestry in the Iceman. Instead, he retained the highest Anatolian-farmer-related ancestry among contemporaneous European populations, indicating a rather isolated Alpine population with limited gene flow from hunter-gatherer-ancestry-related populations. Phenotypic analysis revealed that the Iceman likely had darker skin than present-day Europeans and carried risk alleles associated with male-pattern baldness, type 2 diabetes, and obesity-related metabolic syndrome. These results corroborate phenotypic observations of the preserved mummified body, such as high pigmentation of his skin and the absence of hair on his head.

Limited genetic changes observed during in situ and ex situ conservation in Nordic populations of red clover (Trifolium pratense).

In situ and ex situ conservation are the two main approaches for preserving genetic diversity. The advantages and disadvantages of the two approaches have been discussed but their genetic effects have not been fully evaluated. In this study we investigate the effects of the two conservation approaches on genetic diversity in red clover. Seed samples collected from wild populations in Sweden and Norway in 1980, their subsequent generations created during seed regeneration at the gene bank and samples recollected from the same location as the original samples, were analyzed with microsatellite markers, alongside reference samples from cultivars. Overall, there was a differentiation between cultivars and the wild material and between wild material from Sweden and Norway. In general, the original collections clustered together with the later generations of the same accession in the gene bank, and with the recollected samples from the same location, and the level of diversity remained the same among samples of the same accession. Limited gene flow from cultivated varieties to the wild populations was detected; however, some wild individuals are likely to be escapees or affected by gene flow. In conclusion, there were examples of genetic changes within individual accessions both in situ and ex situ, as is also to be expected in any living population. However, we observed only limited genetic changes in both in situ and ex situ conservation over the generations included in this study and with the relatively large populations used in the ex situ conservation in the gene bank at NordGen.

Can flowers help to disentangle the Vriesea oligantha complex (Bromeliaceae: Tillandsioideae)? Taxonomic implications and contributions to the floral anatomy and biology of Stigmatodon

Abstract The Vriesea oligantha complex comprises Vriesea lancifolia, Vriesea oligantha, and Vriesea pseudoligantha, which were recently transferred to Stigmatodon. Such species exhibit strong morphological convergence to live in rocky fields, which makes difficult their identification in the wild or in herbarium specimens. In a previous work, leaf characters helped in the species delimitation and evidenced a new taxon. Considering that morphology, anatomy, and aspects of floral biology can contribute to better define species limits and to indicate potential pollinators, individuals from nine populations of V. oligantha complex were comparatively studied. The typical V. oligantha is mainly distinguished by tubular flowers, with simple petal appendages and diurnal anthesis. The remaining individuals studied from different populations exhibit campanulate corollas, with denticulate petal appendages and nocturnal anthesis, not allowing for the separation of V. lancifolia, V. pseudoligantha, and a fourth taxon. Floral anatomy is less variable than the external morphology, with little contribution to the species delimitation; however, it is helpful in the circumscription of Stigmatodon. The infralocular septal nectaries and the floral features provide evidence that the main pollinators of campanulate and tubular flowers are bats and hummingbirds, respectively. Specific pollinator guilds in combination with fragmented populations may explain the limited gene flow amongst populations.

Phylogeography and molecular diversity of two highly abundant Themisto amphipod species in a rapidly changing Arctic Ocean.

Rapid warming in the Arctic is drastically impacting marine ecosystems, affecting species communities and food-web structure. Pelagic Themisto amphipods are a major component of the Arctic zooplankton community and represent a key link between secondary producers and marine vertebrates at higher trophic levels. Two co-existing species dominate in the region: the larger Themisto libellula, considered a true polar species and the smaller Themisto abyssorum, a sub-Arctic, boreal-Atlantic species. Recent changes in abundance and distribution ranges have been detected in both species, likely due to the Atlantification of the Arctic. The ecology and genetic structure of these species are understudied, despite their high biomass and importance in the food web. For both species, we assessed genetic diversity, patterns of spatial genetic structure and demographic history using samples from the Greenland shelf, Fram Strait and Svalbard. This was achieved by analysing variation on the mitochondrial cytochrome c oxidase subunit 1 gene (mtCOI). The results revealed contrasting levels of mtCOI diversity: low levels in T. libellula and high levels in T. abyssorum. A lack of spatial genetic structure and a high degree of genetic connectivity were detected in both species in the study region. These patterns of diversity are potentially linked to the impacts of the Last Glacial Maximum. T. libellula populations may have been isolated in glacial refugia, undergoing gene flow restriction and vicariant effects, followed by a population expansion after deglaciation. Whereas T. abyssorum likely maintained a stable, widely distributed metapopulation further south, explaining the high diversity and connectivity. This study provides new data on the phylogeography of two ecologically important species, which can contribute to predicting how zooplankton communities and food-web structure will manifest in the rapidly changing Arctic.

Genetic diversity and population structure of Vernonia amygdalina Del. in Uganda based on genome wide markers.

Determining the extent and distribution of genetic diversity is an essential component of plant breeding. In the present study, we explored the genetic diversity and population structure of Vernonia amygdalina, a fodder, vegetable and medicinal species of Africa and some parts of Yemen. Most empirical studies demonstrate that populations that are separated by geographic or ecological factors may experience genetic differentiation resulting from restricted gene flow between populations. A total of 238 individuals were sampled from two populations: i) Lake Victoria crescent (LVC) and ii) Southern and Eastern Lake Kyoga basin (SEK) agroecological zones of Uganda and genotyped using DArT platform. Of the two populations, the overall mean observed heterozygosity (Ho) was low to medium (Ho = 0.07[silicoDArTs] and 0.2[SNPs]). Inbreeding levels were also very low (-0.04 to -0.08) suggesting the presence of random mating. Partitioning of genetic structure in the two populations indicated that SEK exhibited a higher genetic diversity than LVC. The principal coordinates analysis (PCA) showed no geographical structuring, consistent with the low genetic differentiation (Fst = 0.00) and the low Euclidean genetic distance (1.38-1.39) between the LVC and SEK populations. However, STRUCTURE analysis with admixture models revealed weak possible genetic clusters with very small genetic distance among them. Overall, the results suggest low genetic diversity and weak genetic differentiation between the two populations. One possible explanation of the results could be the presence of human assisted gene flow over long distances.

Israeli Oncocyclus irises: Phylogenetic relationships and evolutionary history

Abstract Oncocyclus is a large group of bearded irises with poorly known phylogeny and evolutionary history. In Israel, Iris sect. Oncocyclus comprises eight species belonging to three aggregates. We used a combination of approaches to resolve the phylogenetic relationships of these species and indicate the evolutionary forces responsible for their origin. We sequenced the whole chloroplast genomes of species and integrated a phylogenetic tree with results of genetic (AFLP) divergence, degree of reproductive isolation, and species distribution modeling. Our findings suggest that quantitative and even qualitative morphological characters, such as flower color, are unreliable diagnostic traits for Oncocyclus taxonomy; that some recognized species comprise more than one species; and that group evolution did not involve the origin of distinct flower aggregates. A lack of pre-zygotic reproductive isolation agrees with the very low variability of the Oncocyclus plastome, suggesting that Israeli Oncocyclus species are very young. Homoploid hybridization followed or preceded by long periods of geographic isolation, and local selection likely contributed to speciation in Oncocyclus. In the group evolutionary history, importance of homoploid hybridization and local selection differed among species, but limited gene flow played a crucial role for all species.

Extent of intraspecific trait variability in ecologically central and marginal populations of a dominant alpine plant across European mountains.

Studying trait variability and restricted gene flow between populations of species can reveal species dynamics. Peripheral populations commonly exhibit lower genetic diversity and trait variability due to isolation and ecological marginality, unlike central populations experiencing gene flow and optimal conditions. This study focused on Carex curvula, the dominant species in alpine acidic meadows of European mountain regions. The species is sparser in dry areas such as the Pyrenees and Balkans, compared to the Central-Eastern Alps and Carpathians. We hypothesized that distinct population groups could be identified based on their mean functional trait values and their correlation with the environment; we predicted that ecologically marginal populations would have stronger trait correlations, lower within-population trait variability (intraspecific trait variability, ITV) and lower genetic diversity than populations of optimal habitats. Sampling was conducted in 34 populations that spanned the entire distribution range of C. curvula. We used hierarchical clustering to identify emergent functional groups of populations, defined by combinations of multiple traits associated with nutrient economy and drought tolerance (e.g. specific leaf area, anatomy). We contrasted the geographical distribution of these groups in relation to environment and genetic structure. We compared pairwise trait relationships, within-population trait variation (ITV) and neutral genetic diversity between groups. Our study identified emergent functional groups of populations. Those in the southernmost ranges, specifically the Pyrenees and Balkan region, showed drought-tolerant trait syndromes and correlated with indicators of limited water availability. While we noted a decline in population genetic diversity, we did not observe any significant changes in ITV in ecologically marginal (peripheral) populations. Our research exemplifies the relationship between ecological marginality and geographical peripherality, which in this case study is linked to genetic depauperation but not to reduced ITV. Understanding these relationships is crucial for understanding the biogeographical factors shaping trait variation.

Population Structure and Genetic Diversity of Rice (Oryza sativa L.) Germplasm from the Democratic Republic of Congo (DRC) Using DArTseq-Derived Single Nucleotide Polymorphism (SNP)

Understanding the genetic diversity and population structure of rice is crucial for breeding programs, conservation efforts, and the development of sustainable agricultural practices. This study aimed to assess the genetic diversity and population structure of 94 rice (Oryza sativa L.) genotypes from the Democratic Republic of Congo using a set of 8389 high-quality DArTseq-based single nucleotide polymorphism (SNP) markers. The average polymorphic information content (PIC) of the markers was 0.25. About 42.4% of the SNPs had a PIC value between 0.25 and 0.5, which were moderately informative. The ADMIXTURE program was used for structure analysis, which revealed five sub-populations (K = 5), with admixtures. In principal component analysis (PCA), the first three principal components accounted for 36.3% of the total variation. Analysis of molecular variance revealed significant variation between sub-populations (36.09%) and within genotypes (34.04%). The low overall number of migrants (Nm = 0.23) and high fixation index (Fst = 0.52) indicated limited gene flow and significant differentiation between the sub-populations. Observed heterozygosity (Ho = 0.08) was lower than expected heterozygosity (He = 0.14) because of the high inbreeding (Fis = 0.52) nature of rice. A high average Euclidean genetic distance (0.87) revealed the existence of genetic diversity among the 94 genotypes. The significant genetic diversity among the evaluated rice genotypes can be further explored to obtain potentially desirable genes for rice improvement.

Genetic Structure of Aedes (Stegomyia) albopictus Populations in Russia.

Aedes (Stegomyia) albopictus was found for the first time in 2011 on the Black Sea coast in Russia, and during 2011-2019, the species expanded over two climate zones Cfa and Csa. Here, we studied the sequence diversity of the mitochondrial cytochrome c oxidase I (COI) gene, 1317-1433bp in length. In total, 131 specimens of Ae. albopictus sampled from 21 locations in Russia and Abkhazia were examined. Two of the six identified mitochondrial haplotypes were detected for the first time. Four COI haplotypes were shared by at least two studied local populations. The most prevalent H1 and H2 haplotypes dominated in all the sampled localities in the Cfa zone. The H3 haplotype was prevalent in the Csa zone. Other haplotypes were rare. Phylogenetic analyses, spatial isolation and limited gene flow revealed that the samples from the Csa zone differed significantly from those from the Cfa zone. Two spatially isolated genetic lineages exist in Ae. albopictus population in southern region of Russia. One lineage obtained on the seacoast and inland (in valleys of the Caucasus Mountains and steppe zone) is widely distributed worldwide including Mediterranean populations. This confirms the hypothesis that the emergence of Ae. albopictus population in southern region of Russia may be associated with the terrestrial spread of mosquitoes from the well-established European population due to human activity. The other lineage, discovered in Novorossiysk, a maritime port, is similar to Ae. albopictus from the USA and Japan, suggesting the independent introduction of these mosquitoes.

Recruitment and migration patterns reveal a key role for seed banks in the meta-population dynamics of an aquatic plant

Progressive habitat fragmentation threatens plant species with narrow habitat requirements. While local environmental conditions define population growth rates and recruitment success at the patch level, dispersal is critical for population viability at the landscape scale. Identifying the dynamics of plant meta-populations is often confounded by the uncertainty about soil-stored population compartments. We combined a landscape-scale assessment of an amphibious plant’s population structure with measurements of dispersal complexity in time to track dispersal and putative shifts in functional connectivity. Using 13 microsatellite markers, we analyzed the genetic structure of extant Oenanthe aquatica populations and their soil seed banks in a kettle hole system to uncover hidden connectivity among populations in time and space. Considerable spatial genetic structure and isolation-by-distance suggest limited gene flow between sites. Spatial isolation and patch size showed minor effects on genetic diversity. Genetic similarity found among extant populations and their seed banks suggests increased local recruitment, despite some evidence of migration and recent colonization. Results indicate stepping-stone dispersal across adjacent populations. Among permanent and ephemeral demes the resulting meta-population demography could be determined by source-sink dynamics. Overall, these spatiotemporal connectivity patterns support mainland-island dynamics in our system, highlighting the importance of persistent seed banks as enduring sources of genetic diversity.