Genetic structure and population diversity of Phytophthora infestans strains in Pacific western Canada.

Late blight caused by Phytophthora infestans is an economically important disease of potato and tomato worldwide. In Canada, an increase in late blight incidence and severity coincided with changes in genetic composition of P. infestans. We monitored late blight incidence on tomato and potato in Pacific western and eastern Canada between 2019 and 2022, identified genotypes of P. infestans, and examined their population genetic diversity. We identified four major existing genotypes US11, US17, US8, and US23 as well as 25 new genotypes. The US11 genotype was dominant in Pacific western Canada, accounting for 59% of the total population. We discovered the US17 genotype for the first time in Canada. We revealed a higher incidence of late blight and quite diverse genotypes of P. infestans in Pacific western Canada than in eastern Canada. We found high genetic diversity of P. infestans population from Pacific western Canada, as evidenced by the high number of multilocus genotypes, high values of genetic diversity indices, and emergence of 25 new genotypes. Considering the number of disease incidence, the detection of diverse known genotypes, the emergence of novel genotypes, and the high number of isolates resistant to metalaxyl-m (95%) from Pacific western Canada, the region could play a role in establishing sexual recombination and diverse populations, which could ultimately pose challenges for late blight management. Therefore, continuous monitoring of P. infestans populations in Pacific western region and across Canada is warranted. KEY POINTS: • Genotypes of P. infestans in Pacific western were quite diverse than in eastern Canada. • We discovered US17 genotype for the first time in Canada and identified 26 novel genotypes. • Approximately 95% of P. infestans isolates were resistant to metalaxyl-m.

Identificación molecular y diversidad genética de las especies de nematodos Globodera rostochiensis y G. pallida en regiones productoras de papa de Guatemala / Molecular identification and genetic diversity of the species of nematodesGlobodera rostochiensisandG. pallidain potato growing regions of Guatemala

En Guatemala, la producción del cultivo de papa se ve afectada por los nematodos Globodera rostochiensis y Globo-dera pallida. La capacidad de ambas especies para formar quistes complica su control y provoca el aumento de sus poblaciones. En Guatemala se reporta la presencia de ambas especies de nematodos por identificación morfológica, sin embargo, no se ha realizado una confirmación molecular. Este es el primer estudio para validar la presencia de ambas especies de nematodos por PCR múltiple y la determinación de la diversidad y estructura genética de las poblaciones utilizando marcadores moleculares. Se realizaron muestreos en cuatro departamentos productores de papa del país. La identificación por PCR se realizó con el cebador común ITS5 y los cebadores PITSr3 específico para G. rostochiensisy PITSp4 para G. pallida. La caracterización molecular se realizó con el marcador AFLP. Se confirmó la presencia de las dos especies de nematodos en los cuatro departamentos. Los índices de diversidad Shannon y heterocigosidad esperada revelaron mayor diversidad genética en G. rostochiensis (H = 0.311, He = 0.301) que en G. pallida (H = 0.035, He = 0.223). Los métodos NJ, DAPC y PCA exhibieron una débil estructura entre las poblaciones de ambas especies de nematodos. Los resultados sugieren un patrón de dispersión desde Quetzaltenango hacia el resto del país, atribuido a la comercialización de semilla contaminada con nematodos. Se sugiere promover programas de socialización sobre los beneficios del uso de semilla certificada, además de constantes monitoreos moleculares para un diagnóstico certero de ambas especies de nematodos.

In Guatemala, potato crop production is affected by the nematodes Globodera rostochiensis and Globodera pallida. The ability of both species to form cysts complicates their control and causes an increase in their populations. In Guatemala, both species of nematodes have been reported by morphological identification; however, molecular confirmation has not been carried out. It is the first study to validate the presence of both nematode species by multiplex PCR and determine the diversity and genetic structure of the populations using molecular markers. Sampling was carried out in four pota-to-producing departments of the country. PCR identification was performed with the common primer ITS5 and the primers PITSr3 specific for G. rostochiensis and PITSp4 for G. pallida. We performed molecular characterization with the AFLP marker. We confirmed the presence of the two nematode species in the four departments. Shannon diversity and expected heterozygosity indices revealed higher genetic diversity in G. rostochiensis (H = 0.311, He = 0.301) than in G. pallida (H = 0.035, He = 0.223). The NJ, DAPC, and PCA methods exhibited weak structure among populations of both nematode species. The results suggest a dispersal pattern from Quetzaltenango to the rest of the country, attributed to the commer-cialization of seed contaminated with nematodes. We suggest promoting socialization programs on the benefits of using certified seeds and constant molecular monitoring for an accurate diagnosis of both species of nematodes.

Genetic rescue by distant trees mitigates qualitative pollen limitation imposed by fine-scale spatial genetic structure.

Restricted seed dispersal frequently leads to fine-scale spatial genetic structure (i.e., FSGS) within plant populations. Depending on its spatial extent and the mobility of pollinators, this inflated kinship at the immediate neighbourhood can critically impoverish pollen quality. Despite the common occurrence of positive FSGS within plant populations, our knowledge regarding the role of long-distance pollination preventing reproductive failure is still limited. Using microsatellite markers, we examined the existence of positive FSGS in two low-density populations of the tree Pyrus bourgaeana. We also designed controlled crosses among trees differing in their kinship to investigate the effects of increased local kinship on plant reproduction. We used six pollination treatments and fully monitored fruit production, fruit and seed weight, proportion of mature seeds per fruit, and seed germination. Our results revealed positive FSGS in both study populations and lower fruit initiation in flowers pollinated with pollen from highly-genetically related individuals within the neighbourhood, with this trend intensifying as the fruit development progressed. Besides, open-pollinated flowers exhibited lower performance compared to those pollinated by distant pollen donors, suggesting intense qualitative pollen limitation in natural populations. We found positive fine-scale spatial genetic structure is translated into impoverished pollen quality from nearby pollen donors which negatively impacts the reproductive success of trees in low-density populations. Under this scenario of intrapopulation genetic rescue by distant pollen donors, the relevance of highly-mobile pollinators for connecting spatially and genetically distant patches of trees may be crucial to safeguarding population recruitment.

Hybridization and geographic distribution shapes the spatial genetic structure of two co-occurring orchid species.

Multiple ecological and life-history traits shape the fine-scale spatial genetic structure (FSGS) of a given population. The occurrence in core versus peripheral populations, levels of outcrossing, pollen and seed dispersal, and hybridization are important biological properties that influence the kinship of individuals within populations. We examined spatial genetic structure within 15 populations of Epidendrum fulgens and E. puniceoluteum distributed along a linear gradient of Brazilian coastal vegetation, including both allopatric and sympatric populations where the two orchid species hybridize. We analyzed 581 mapped specimens using nine simple sequence repeat loci, aiming to investigate how geographic distribution and hybridization shape within-population FSGS. A significant increase in FSGS was found towards peripheral populations, compared to core populations. Analysis of short-distance and long-distance components of FSGS identified biparental inbreeding and higher levels of FSGS at peripheral populations, when compared to core populations. In contrast, the relatively high density of reproductive adults in core populations potentially leads to highly overlapping seed and pollen movement, decreasing FSGS. Hybridization was an important factor shaping within-population spatial genetic structure at sympatric sites, decreasing the FSGS observed in parental species. Our results indicate that different ecological forces act in concert to create a gradient of FSGS along species distribution ranges, shaped by extensive levels of intraspecific and interspecific gene exchange.

Genetic Structure and Subclonal Variation of Extant and Recent U.S. Lineages of Phytophthora infestans.

The oomycete Phytophthora infestans is an important plant pathogen on potato and tomato crops. We examined the genetic structure of extant 20th and 21st century U.S. lineages of P. infestans and compared them with populations from South America and Mexico to examine genetic relationships and potential sources of lineages. US-23, currently the most prevalent lineage detected in the United States, shared genetic similarity primarily with the BR-1 lineage identified in the 1990s from Bolivia and Brazil. Lineages US-8, US-14, and US-24, predominantly virulent on potato, formed a cluster distinct from other U.S. lineages. Many of the other U.S. lineages shared significant genetic similarity with Mexican populations. The US-1 lineage, dominant in the mid-20th century, clustered with US-1 lineages from Peru. A survey of the presence of RXLR effector PiAVR2 revealed that some lineages carried PiAVR2, its resistance-breaking variant PiAVR2-like, or both. Minimum spanning networks developed from simple sequence repeat genotype datasets from USABlight outbreaks clearly showed the expansion of US-23 over a 6-year time period and geographic substructuring of some lineages in the western United States. Many clonal lineages of P. infestans in the United States have come from introductions from Mexico, but the US-23 and US-1 lineages were most likely introduced from other sources.

Temporal population genetic structure in the pollen pool for flowering time: A field experiment with Brassica rapa (Brassicaceae).

PREMISE OF THE STUDY: Assortative mating by flowering time can cause temporal genetic structure in species with heritable flowering times. A strong temporal structure, when coupled with a seasonal shift in selection, may lead to adaptive temporal clines. We implemented a prospective and retrospective method to estimate the temporal genetic structure in the pollen pool of Brassica rapa. METHODS: The prospective method uses flowering schedules to estimate the seasonal shift in the pollen donors' phenotype. By examining the offspring generation, we can get a direct estimate of temporal genetic structure, i.e., a retrospective estimate. However, this estimate is problematic because of the phenotypic correlation of the trait of interest, flowering time, between dam and sire. We developed a novel retrospective method that isolates flowering time by holding the maternal contribution constant and sampled the pollen pool in eight open-pollinated field plots throughout the flowering season. KEY RESULTS: We found temporal genetic structure for flowering time in seven of the eight field plots. Interestingly, the direct (retrospective) temporal structure estimate was 35% larger than the prospective estimate based on flowering schedules. Spatial clumping of pollen donors did not affect temporal structure, but structure intensified when heritability was experimentally enhanced. CONCLUSIONS: Temporal genetic structure, especially for flowering time, likely occurs in many plant populations and may be underestimated using a prospective method. We discuss the genome-wide consequences of temporal genetic structure and the potential for adaptive temporal clines in plant populations.

Quimiotipos, Extracción, Composición y Aplicaciones del Aceite Esencial de Lippia alba / Quimiotipos, extração, composição e uso do óleo essencial de Lippia alba / Chemotypes, extraction, chemical composition and use of lippia alba essential oil

RESUMO Lippia alba é uma planta amplamente distribuída nas zonas tropicais, subtropicais e temperadas das Américas, África e Ásia. O óleo essencial de L. alba tem sido amplamente estudado, entretanto apresenta variações de produção. Portanto este estudo teve como objetivo realizar uma revisão dos principais quimiotipos, métodos de extração, composição e aplicação do óleo essencial de L. alba. Neste estudo são discutidos os principais quimiotipos e sua relação com fatores genéticos e características morfológicas. Também são discutidos os fatores que afetam o rendimento de produção, composição química, métodos de extração e do uso e da atividade biológica do óleo essencial de L. alba. Apesar da vasta literatura sobre os óleos essenciais de L. alba, ainda desenvolvimento de aplicações para a produção de cosméticos, fármacos e alimentos, bem como faltam definições agronomicas sobre o cultivo e melhoramento desta planta.

ABSTRACT Lippia alba is a plant widely distributed in tropical, subtropical and temperate zones of the Americas, Africa and Asia. The essential oil of L. alba has been widely studied and there are many variations in the production process. Therefore, this study is aimed at conducting a review of the main chemotypes, extraction methods, composition and application of the essential oil of L. alba. In this study, the main chemotypes and its relation to genetic and morphological characteristics are discussed. It also discusses the factors that affect the yield, chemical composition, extraction methods and the use and the biological activity of the essential oil of L. alba. Despite the vast literature on the essential oils of L. alba, there is still a lack of development in its application for the production of cosmetics, pharmaceuticals and food, as well as a lack of agronomic definitions for its cultivation and genetic improvement.

Spatial Scales of Genetic Structure in Free-Standing and Strangler Figs (Ficus, Moraceae) Inhabiting Neotropical Forests.

Wind-borne pollinating wasps (Agaonidae) can transport fig (Ficus sp., Moraceae) pollen over enormous distances (> 100 km). Because of their extensive breeding areas, Neotropical figs are expected to exhibit weak patterns of genetic structure at local and regional scales. We evaluated genetic structure at the regional to continental scale (Panama, Costa Rica, and Peru) for the free-standing fig species Ficus insipida. Genetic differentiation was detected only at distances > 300 km (Jost´s Dest = 0.68 ± 0.07 & FST = 0.30 ± 0.03 between Mesoamerican and Amazonian sites) and evidence for phylogeographic structure (RST>>permuted RST) was only significant in comparisons between Central and South America. Further, we assessed local scale spatial genetic structure (SGS, d ≤ 8 km) in Panama and developed an agent-based model parameterized with data from F. insipida to estimate minimum pollination distances, which determine the contribution of pollen dispersal on SGS. The local scale data for F. insipida was compared to SGS data collected for an additional free-standing fig, F. yoponensis (subgenus Pharmacosycea), and two species of strangler figs, F. citrifolia and F. obtusifolia (subgenus Urostigma) sampled in Panama. All four species displayed significant SGS (mean Sp = 0.014 ± 0.012). Model simulations indicated that most pollination events likely occur at distances > > 1 km, largely ruling out spatially limited pollen dispersal as the determinant of SGS in F. insipida and, by extension, the other fig species. Our results are consistent with the view that Ficus develops fine-scale SGS primarily as a result of localized seed dispersal and/or clumped seedling establishment despite extensive long-distance pollen dispersal. We discuss several ecological and life history factors that could have species- or subgenus-specific impacts on the genetic structure of Neotropical figs.

Diversidade e estrutura genética de populações de Varronia curassavica Jacq. em restingas da Ilha de Santa Catarina / Genetic diversity and structure of Varronia curassavica Jacq. populations in the restinga of Santa Catarina Island

RESUMO Varronia curassavica Jacq. (Boraginaceae) está presente na vegetação de restinga e apresenta relevantes propriedades medicinais. A espécie é explorada especialmente por comunidades locais e pela indústria farmacêutica, porém, carece de informações ecológicas e genéticas a seu respeito. Nesse contexto, o estudo foi conduzido com o objetivo de caracterizar a diversidade genética de três populações de V. curassavica em áreas de restinga na Ilha de Santa Catarina. Foram coletadas folhas de 50 indivíduos adultos em cada uma das três áreas de estudo e as frequências alélicas das populações foram obtidas a partir de 14 locos alozímicos. Foram encontrados 25 alelos distintos nas três populações, sendo dois alelos exclusivos. As populações apresentaram diversidade genética média de 0,111 e índice de fixação médio de -0,060 (-0,273 até 0,222). Os níveis de diversidade são intermediários, semelhantes aos exibidos por espécies da mesma família ou de características ecológicas semelhantes. Os índices de fixação foram todos significativos e discrepantes entre as populações, sendo que duas delas apresentaram excesso de heterozigotos. A divergência genética interpopulacional foi significativa e igual a 0,079, considerada moderada e sugerindo efeitos de subdivisão populacional. Os níveis de diversidade genética encontrados e a redução populacional causada pela redução e fragmentação dos habitats em que a espécie ocorre sugerem medidas de conservação ex situ e demandam maior rigor na proteção legal de áreas de proteção permanente.

ABSTRACT The Varronia curassavica Jacq. (Boraginaceae) is present in restinga vegetation and shows relevant medicinal properties. The species is exploited by local communities and by the pharmaceutical industry; however, it lacks ecological and genetic information. Thus, this study aimed to characterize the genetic diversity of three V. curassavica populations in restinga areas of Santa Catarina Island. Leaves of 50 adult individuals were sampled in each of the three study areas and the allelic frequencies were obtained from 14 allozyme loci. Twenty-five different alleles were found in the three populations, two of them being exclusive. The populations showed, on average, a genetic diversity of 0,111 and a fixation index of -0,060 (-0,273 to 0,222). The diversity levels are intermediary, similar to those ones owned by species of the same family or with similar ecological traits. The fixation indexes were all significant and discrepant among the populations, with two of them showing excess of heterozygotes. The genetic divergence among populations was significant and equal to 0,079, which is considered moderate and suggests effects of population subdivision. The levels of genetic diversity found and the population decrease caused by reduction and fragmentation of habitats in which the species are present implies in ex situ conservation measures and a higher enforcement of the legal preservation of permanent protected areas.

[Genetic structure and genetic diversity of Artemisia annua varieties (strains) populations based on SCoT markers].

To reveal the genetic diversity and genetic structure in Artemisia annua varieties (strains) populations, we detected the genetic polymorphism within and among eight varieties (strains) populations (192 individuals) by the approach of Start Codon Targeted Polymorphism (SCoT). The associated genetic parameters were calculated by POPGENE1.31 and the relationship was constructed based on UPGMA method. The results showed that, using 20 screened primers, a total of 145 bands were produced, of which 122 were polymorphic loci. At species level, there was a high level of genetic diversity among eight varieties (strains) populations (PPB = 84.1% ,H = 0.217 3 and H(sp) = 0.341 9). However, at the variety (strains) population level, genetic diversity was lower, the average of genetic parameters was PPB = 41.9%, H = 0.121 5, H(pop) = 0.186 8. The Nei's genetic differentiation coefficient was 0.441 0, indicate that most of the genetic variation in this species existed within the variety populations. The gene flow (N(m) = 0.633 9) was less among populations, indicating that the degree of genetic differentiation was higher. Genetic similarity coefficient were changed from 0.755 1 to 0.985 7. By clustering analysis, eight varieties (strains) were clustered into two major categories and it was also showed the same or similar genetic background varieties (strains) have a tendency to gather in the same group. Results suggest that, in variety breeding, breeders should strengthen the exchange of bred germplasm and increase mutual penetration of excellent genes, which would broaden the genetic base of A. annua.

Patterns of pollen dispersal in a small population of the Canarian endemic palm (Phoenix canariensis).

The genetic diversity of small populations is greatly influenced by local dispersal patterns and genetic connectivity among populations, with pollen dispersal being the major component of gene flow in many plants species. Patterns of pollen dispersal, mating system parameters and spatial genetic structure were investigated in a small isolated population of the emblematic palm Phoenix canariensis in Gran Canaria island (Canary Islands). All adult palms present in the study population (n=182), as well as 616 seeds collected from 22 female palms, were mapped and genotyped at 8 microsatellite loci. Mating system analysis revealed an average of 5.8 effective pollen donors (Nep) per female. There was strong variation in correlated paternity rates across maternal progenies (ranging from null to 0.9) that could not be explained by the location and density of local males around focal females. Paternity analysis revealed a mean effective pollen dispersal distance of ∼71 m, with ∼70% of effective pollen originating from a distance of <75 m, and 90% from <200 m. A spatially explicit mating model indicated a leptokurtic pollen dispersal kernel, significant pollen immigration (12%) from external palm groves and a directional pollen dispersal pattern that seems consistent with local altitudinal air movement. No evidence of inbreeding or genetic diversity erosion was found, but spatial genetic structure was detected in the small palm population. Overall, the results suggest substantial pollen dispersal over the studied population, genetic connectivity among different palm groves and some resilience to neutral genetic erosion and subsequently to fragmentation.

[Genetic diversity and genetic structure of endangered wild Sinopodophyllum emodi by start codon targeted polymorphism].

OBJECTIVE: Revealed the genetic diversity level and genetic structure characteristics in Sinopodophyllum emodi, a rare and endangered species in China. METHOD: We detected the genetic polymorphism within and among six wild populations (45 individuals) by the approach of Start Codon Targeted (SCoT) Polymorphism. The associated genetic parameters were calculated by POP-GENE1.31 and the relationship was constructed based on UPGMA method. RESULT: A total of 350 bands were scored by 27 primers and 284 bands of them were polymorphic. The average polymorphic bands of each primer were 10.52. At species level, there was a high level of genetic diversity among six populations (PPB = 79.27%, N(e) = 1.332 7, H = 0.210 9 and H(sp) = 0.328 6). At population level, the genetic diversity level was low (PPB = 10.48% (4.00% -23.71%), N(e) = 1.048 7 (1.020 7-1.103 7), H = 0.029 7 (0.012 9-0.063 1), H(pop) = 0.046 2 (0.019 9-0.098 6). The Nei's coefficient of genetic differentiation was 0.841 1, which was consistent with the Shannon's coefficient of genetic differentiation (0.849 4). Two calculated methods all showed that most of the genetic variation existed among populations. The gene flow (N(m) = 0.094 4) was less among populations, indicating that the degree of genetic differentiation was higher. Genetic similarity coefficient were changed from 0.570 8 to 0.978 7. By clustering analysis, the tested populations were divided into two classes and had a tendency that the same geographical origin or material of similar habitats clustered into one group. CONCLUSION: The genetic diversity of samples of S. emodi is high,which laid a certain foundation for effective protection and improvement of germplasm resources.

The population genetic structure of Rhizoctonia solani AG-3PT from potato in the Colombian Andes.

The soilborne fungus Rhizoctonia solani anastomosis group 3 (AG-3PT) is a globally important potato pathogen. However, little is known about the population genetic processes affecting field populations of R. solani AG-3PT, especially in the South American Colombian Andes, which is near the center of diversity of the two most common groups of cultivated potato, Solanum tuberosum and S. phureja. We analyzed the genetic structure of 15 populations of R. solani AG-3PT infecting potato in Colombia using 11 simple-sequence repeat (SSR) markers. In total, 288 different multilocus genotypes were identified among 349 fungal isolates. Clonal fractions within field populations were 7 to 33%. RST statistics indicated a very low level of population differentiation overall, consistent with high contemporary gene flow, though moderate differentiation was found for the most distant southern populations. Genotype flow was also detected, with the most common genotype found widely distributed among field populations. All populations showed evidence of a mixed reproductive mode, including both asexual and sexual reproduction, but two populations displayed evidence of inbreeding.

Genetic diversity and genetic structure of endangered wild Sinopodophyllum emodi by start codon targeted polymorphism / 中国中药杂志

<p><b>OBJECTIVE</b>Revealed the genetic diversity level and genetic structure characteristics in Sinopodophyllum emodi, a rare and endangered species in China.</p><p><b>METHOD</b>We detected the genetic polymorphism within and among six wild populations (45 individuals) by the approach of Start Codon Targeted (SCoT) Polymorphism. The associated genetic parameters were calculated by POP-GENE1.31 and the relationship was constructed based on UPGMA method.</p><p><b>RESULT</b>A total of 350 bands were scored by 27 primers and 284 bands of them were polymorphic. The average polymorphic bands of each primer were 10.52. At species level, there was a high level of genetic diversity among six populations (PPB = 79.27%, N(e) = 1.332 7, H = 0.210 9 and H(sp) = 0.328 6). At population level, the genetic diversity level was low (PPB = 10.48% (4.00% -23.71%), N(e) = 1.048 7 (1.020 7-1.103 7), H = 0.029 7 (0.012 9-0.063 1), H(pop) = 0.046 2 (0.019 9-0.098 6). The Nei's coefficient of genetic differentiation was 0.841 1, which was consistent with the Shannon's coefficient of genetic differentiation (0.849 4). Two calculated methods all showed that most of the genetic variation existed among populations. The gene flow (N(m) = 0.094 4) was less among populations, indicating that the degree of genetic differentiation was higher. Genetic similarity coefficient were changed from 0.570 8 to 0.978 7. By clustering analysis, the tested populations were divided into two classes and had a tendency that the same geographical origin or material of similar habitats clustered into one group.</p><p><b>CONCLUSION</b>The genetic diversity of samples of S. emodi is high,which laid a certain foundation for effective protection and improvement of germplasm resources.</p>

Diversidade genética de populações naturais de pariparoba [Pothomorphe umbellata (L. ) Miq.] por RAPD / Genetic diversity of natural populations of pariparoba [Pothomorphe umbellata (L. ) Miq.] according to RAPD analysis

O objetivo desse trabalho foi analisar a estrutura genética de populações de Pothomorphe umbellata (L.) Miq. com base em polimorfismos moleculares do tipo RAPD. Foram analisadas quatro populações naturais do estado de São Paulo (Jacareí, Jundiaí, Piquete e Ubatuba) e uma população do Paraná (Adrianópolis). Foram identificados 25 locos polimórficos (96,15%). Elevados índices de diversidade genética foram observados dentro das populações (Hs = 0,2220). Verificou-se que 65,33% da variabilidade genética total encontra-se dentro das populações e 34,67% entre as populações; índices estes, obtidos a partir do cálculo da divergência genética (G ST = 0,3467). Os resultados sugerem que essas populações possuem níveis elevados de variabilidade genética, a qual pode ser fortemente impactada pela ação humana.

The aim of this study was to analyze the genetic structure of populations of Pothomorphe umbellata (L.) Miq. based on RAPD molecular polymorphisms. Analysis included four natural populations from São Paulo State (Jacareí, Jundiaí, Piquete, Ubatuba) and one population from Paraná State (Adrianópolis). Twenty-five polymorphic loci (96.15%) were identified. There were high levels of genetic diversity within populations (Hs = 0.2220). Of the total genetic variability, 65.33% is within populations and 34.67% among populations (G ST = 0.3467). Results suggest that these populations have high levels of genetic variability, which can be strongly impacted by human action.

Genetic differentiation for size at first reproduction through male versus female functions in the widespread Mediterranean tree Pinus pinaster.

BACKGROUND AND AIMS: The study of local adaptation in plant reproductive traits has received substantial attention in short-lived species, but studies conducted on forest trees are scarce. This lack of research on long-lived species represents an important gap in our knowledge, because inferences about selection on the reproduction and life history of short-lived species cannot necessarily be extrapolated to trees. This study considers whether the size for first reproduction is locally adapted across a broad geographical range of the Mediterranean conifer species Pinus pinaster. In particular, the study investigates whether this monoecious species varies genetically among populations in terms of whether individuals start to reproduce through their male function, their female function or both sexual functions simultaneously. Whether differences among populations could be attributed to local adaptation across a climatic gradient is then considered. METHODS: Male and female reproduction and growth were measured during early stages of sexual maturity of a P. pinaster common garden comprising 23 populations sampled across the species range. Generalized linear mixed models were used to assess genetic variability of early reproductive life-history traits. Environmental correlations with reproductive life-history traits were tested after controlling for neutral genetic structure provided by 12 nuclear simple sequence repeat markers. KEY RESULTS: Trees tended to reproduce first through their male function, at a size (height) that varied little among source populations. The transition to female reproduction was slower, showed higher levels of variability and was negatively correlated with vegetative growth traits. Several female reproductive traits were correlated with a gradient of growth conditions, even after accounting for neutral genetic structure, with populations from more unfavourable sites tending to commence female reproduction at a lower individual size. CONCLUSIONS: The study represents the first report of genetic variability among populations for differences in the threshold size for first reproduction between male and female sexual functions in a tree species. The relatively uniform size at which individuals begin reproducing through their male function probably represents the fact that pollen dispersal is also relatively invariant among sites. However, the genetic variability in the timing of female reproduction probably reflects environment-dependent costs of cone production. The results also suggest that early sex allocation in this species might evolve under constraints that do not apply to other conifers.

The pollen dispersal kernel and mating system of an insect-pollinated tropical palm, Oenocarpus bataua.

Pollen dispersal shapes the local genetic structure of plant populations and determines the opportunity for local selection and genetic drift, but has been well studied in few animal-pollinated plants in tropical rainforests. Here, we characterise pollen movement for an insect-pollinated Neotropical canopy palm, Oenocarpus bataua, and relate these data to adult mating system and population genetic structure. The study covers a 130-ha parcel in which all adult trees (n=185) were mapped and genotyped at 12 microsatellite loci, allowing us to positively identify the source tree for 90% of pollination events (n=287 of 318 events). Mating system analysis showed O. bataua was effectively outcrossed (t(m)=1.02) with little biparental inbreeding (t(m)-t(s)=-0.005) and an average of 5.4 effective pollen donors (N(ep)) per female. Dispersal distances were relatively large for an insect-pollinated species (mean=303 m, max=1263 m), and far exceeded nearest-neighbour distances. Dispersal kernel modelling indicated a thin-tailed Weibull distribution offered the best fit to the genetic data, which contrasts with the fat-tailed kernels typically reported for pollen dispersal in trees. Preliminary analyses suggest that our findings may be explained, at least in part, by a relatively diffuse spatial and temporal distribution of flowering trees. Comparison with previously reported estimates of seed movement for O. bataua suggests that pollen and seed dispersal distances may be similar. These findings add to the growing body of information on dispersal in insect-pollinated trees, but underscore the need for continued research on tropical systems in general, and palms in particular.

Pollen dispersal and gene flow within and into a population of the alpine monocarpic plant Campanula thyrsoides.

BACKGROUND AND AIMS: Gene flow by seed and pollen largely shapes the genetic structure within and among plant populations. Seed dispersal is often strongly spatially restricted, making gene flow primarily dependent on pollen dispersal within and into populations. To understand distance-dependent pollination success, pollen dispersal and gene flow were studied within and into a population of the alpine monocarpic perennial Campanula thyrsoides. METHODS: A paternity analysis was performed on sampled seed families using microsatellites, genotyping 22 flowering adults and 331 germinated offspring to estimate gene flow, and pollen analogues were used to estimate pollen dispersal. The focal population was situated among 23 genetically differentiated populations on a subalpine mountain plateau (<10 km(2)) in central Switzerland. KEY RESULTS: Paternity analysis assigned 110 offspring (33·2 %) to a specific pollen donor (i.e. 'father') in the focal population. Mean pollination distance was 17·4 m for these offspring, and the pollen dispersal curve based on positive LOD scores of all 331 offspring was strongly decreasing with distance. The paternal contribution from 20-35 offspring (6·0-10·5 %) originated outside the population, probably from nearby populations on the plateau. Multiple potential fathers were assigned to each of 186 offspring (56·2 %). The pollination distance to 'mother' plants was negatively affected by the mothers' degree of spatial isolation in the population. Variability in male mating success was not related to the degree of isolation of father plants. CONCLUSIONS: Pollen dispersal patterns within the C. thyrsoides population are affected by spatial positioning of flowering individuals and pollen dispersal may therefore contribute to the course of evolution of populations of this species. Pollen dispersal into the population was high but apparently not strong enough to prevent the previously described substantial among-population differentiation on the plateau, which may be due to the monocarpic perenniality of this species.

Determination of genetic structure of germplasm collections: are traditional hierarchical clustering methods appropriate for molecular marker data?

Despite the availability of newer approaches, traditional hierarchical clustering remains very popular in genetic diversity studies in plants. However, little is known about its suitability for molecular marker data. We studied the performance of traditional hierarchical clustering techniques using real and simulated molecular marker data. Our study also compared the performance of traditional hierarchical clustering with model-based clustering (STRUCTURE). We showed that the cophenetic correlation coefficient is directly related to subgroup differentiation and can thus be used as an indicator of the presence of genetically distinct subgroups in germplasm collections. Whereas UPGMA performed well in preserving distances between accessions, Ward excelled in recovering groups. Our results also showed a close similarity between clusters obtained by Ward and by STRUCTURE. Traditional cluster analysis can provide an easy and effective way of determining structure in germplasm collections using molecular marker data, and, the output can be used for sampling core collections or for association studies.

Genetic structure based on nuclear and chloroplast microsatellite loci of Solanum lycocarpum A. St. Hil. (Solanaceae) in Central Brazil.

Solanum lycocarpum (Solanaceae) is a woody species found in the Brazilian Cerrado. The flowers are pollinated by Xylocopa spp bees, and seeds are dispersed by mammals with distinct home range sizes. As a consequence, relative contributions of pollen and seeds to overall gene flow can vary according to different spatial scales. We studied the genetic structure of four natural populations of S. lycocarpum separated by 19 to 128 km, including individuals located along dirt roads that interlink three of the populations. A total of 294 individuals were genotyped with five nuclear and six chloroplast microsatellite markers. Significant spatial genetic structure was found in the total set of individuals; the Sp statistic was 0.0086. Population differentiation based on the six chloroplast microsatellite markers (θ(pC) = 0.042) was small and similar to that based on the five nuclear microsatellite markers (θ(p) = 0.054). For this set of populations, pollen and seed flow did not differ significantly from one another (pollen-to-seed flow ratio = 1.22). Capability for long distance seed dispersion and colonization of anthropogenic sites contributes to the ability of S. lycocarpum to maintain genetic diversity. Seed dispersion along dirt roads may be critical in preserving S. lycocarpum genetic diversity in fragmented landscapes.