Gene Flow Dynamics Research Articles

Small-scale genetic structure of Cerastoderma glaucum in a lagoonal environment: potential significance of habitat discontinuity and unstable population dynamics

Environmental heterogeneity in coastal lagoons is expected to facilitate local adaptation in response to different ecological conditions, causing significant genetic structuring within lagoon populations at a small scale and also differentiation between lagoons. However, these patterns and processes of genetic structuring are still poorly understood. The aims of our study were (1) to seek genetic structure at a small scale in Cerastoderma glaucum inside the Mar Menor coastal lagoon using a mitochondrial DNA marker (COI) that has previously detected genetic differentiation inside the lagoon in other species and (2) to evaluate the influence of extreme environmental conditions and habitat discontinuity on its genetic composition. The results indicate high levels of haplotype diversity and low values of nucleotide diversity. COI data provide evidence of significant population differentiation among some localities within the lagoon. Limited gene flow and unstable population dynamics (i.e. fluctuations in population size caused by local extinction and recolonization), probably due to the high environmental heterogeneity, could generate the small-scale genetic divergence detected between populations within the lagoon.

Genetic diversity and gene flow dynamics revealed in the rare mixed populations of wild soybean (Glycine soja) and semi-wild type (Glycine gracilis) in China

Thus far, there is little knowledge of the genetic diversity, structure and gene flow dynamics in rare wild and semi-wild soybean mixed populations, and such information is vital for understanding of the origin of semi-wild soybean (Glycine gracilis) and the biosafety protection of wild soybean from transgenic soybeans. Population eco-genetic data are necessary to provide a more coherent and comprehensive understanding of the genetic events that occurred in the natural habitats of wild soybean (Glycine soja). We tested genetic diversity and structure of 11 wild mixed populations of wild soybean (Glycine soja) and semi-wild soybean (G. gracilis), 1 wild soybean population, and 1 cultivated soybean variety population were studied using 20 nuclear microsatellite markers (SSRs). We found based on microsatellite polymorphisms that the mixed populations were characterized by higher mean heterozygosity (H o = 0.029) and outcrossing rate (t m = 6.35 %), and lower fixation index (F is = 0.891), and the semi-wild plants had distinctly higher heterozygosity (H o = 0.081) than that of the wild plants (H o = 0.007). The occurrence of semi-wild plants influenced population genetic structure but not geographical population differentiation. These mixed populations exhibited strong ecogeographical differentiation, which suggests that their original populations were colonized over a long phytogeographical history. The introgression occurred through pollen gene flow from the soybean fields into wild populations and created the semi-wild plants, with significant genetic differentiation from the typical wild ones. Introgressive genes could become established by two possible modes in wild soybean populations by both self-segregation and/or intrapopulation secondary hybridization. The latter deserves attention because of the possibility of rapid transgene escape.

Historical connectivity, contemporary isolation and local adaptation in a widespread but discontinuously distributed species endemic to Taiwan, Rhododendron oldhamii (Ericaceae)

Elucidation of the evolutionary processes that constrain or facilitate adaptive divergence is a central goal in evolutionary biology, especially in non-model organisms. We tested whether changes in dynamics of gene flow (historical vs contemporary) caused population isolation and examined local adaptation in response to environmental selective forces in fragmented Rhododendron oldhamii populations. Variation in 26 expressed sequence tag-simple sequence repeat loci from 18 populations in Taiwan was investigated by examining patterns of genetic diversity, inbreeding, geographic structure, recent bottlenecks, and historical and contemporary gene flow. Selection associated with environmental variables was also examined. Bayesian clustering analysis revealed four regional population groups of north, central, south and southeast with significant genetic differentiation. Historical bottlenecks beginning 9168-13,092 years ago and ending 1584-3504 years ago were revealed by estimates using approximate Bayesian computation for all four regional samples analyzed. Recent migration within and across geographic regions was limited. However, major dispersal sources were found within geographic regions. Altitudinal clines of allelic frequencies of environmentally associated positively selected outliers were found, indicating adaptive divergence. Our results point to a transition from historical population connectivity toward contemporary population isolation and divergence on a regional scale. Spatial and temporal dispersal differences may have resulted in regional population divergence and local adaptation associated with environmental variables, which may have played roles as selective forces at a regional scale.

Modular Evolution of Tn GBS s, a New Family of Integrative and Conjugative Elements Associating Insertion Sequence Transposition, Plasmid Replication, and Conjugation for Their Spreading

Integrative and conjugative elements (ICEs) have a major impact on gene flow and genome dynamics in bacteria. The ICEs TnGBS1 and TnGBS2, first identified in Streptococcus agalactiae, use a DDE transposase, unlike most characterized ICEs, which depend on a phage-like integrase for their mobility. Here we identified 56 additional TnGBS-related ICEs by systematic genome analysis. Interestingly, all except one are inserted in streptococcal genomes. Sequence comparison of the proteins conserved among these ICEs defined two subtypes related to TnGBS1 or TnGBS2. We showed that both types encode different conjugation modules: a type IV secretion system, a VirD4 coupling protein, and a relaxase and its cognate oriT site, shared with distinct lineages of conjugative elements of Firmicutes. Phylogenetic analysis suggested that TnGBSs evolved from two conjugative elements of different origins by the successive recruitment of a transposition module derived from insertion sequences (ISs). Furthermore, TnGBSs share replication modules with different plasmids. Mutational analyses and conjugation experiments showed that TnGBS1 and TnGBS2 combine replication and transposition upstream promoters for their transfer and stabilization. Despite an evolutionarily successful horizontal dissemination within the genus Streptococcus, these ICEs have a restricted host range. However, we reveal that for TnGBS1 and TnGBS2, this host restriction is not due to a transfer incompatibility linked to the conjugation machineries but most likely to their ability for transient maintenance through replication after their transfer.

Individual mating decisions and hybridization

The dynamics of gene flow among populations ultimately depend on behavioural interactions among individuals (Ritchie, 2007), construed in the broadest sense to encompass chemical and mechanical interactions in plants and microorganisms. The mechanisms underlying mate choice can, therefore, determine whether hybridization promotes or retards speciation. Further, the nature of the processes underlying mating decisions imposes important constraints on their role as agents of selection. Understanding the evolutionary genetics of hybridization requires a more detailed consideration of what determines mating interactions among individuals. For hybridization to have notable evolutionary consequences, two things have to happen: first, matings have to occur between males and females from divergent populations and second, hybrids have to mate with each other and/or backcross to parentals. There is a growing body of evidence to suggest that behavioural barriers to interspecific mating are brittle and susceptible to environmental perturbation. Once hybridization occurs, novel suites of signals and novel suites of preferences can facilitate backcrossing to parentals or, alternatively, can lead to hybrid speciation. I will discuss each of these processes in turn.

Molecular identification of a Buffy-tufted-ear marmoset (Callithrix aurita) incorporated in a group of invasive marmosets in the Serra dos Orgãos National Park, Rio de Janeiro – Brazil

For years, illegal pet trade resulted in the introduction of marmosets from the species Callithrix jacchus and C. penicillata in the Atlantic Forest of southeastern Brazil. Among other problems these primates are able to produce fertile hybrids in crosses between themselves and also with its counterpart, the endangered Buffy-tufted-ear marmoset (C. aurita) natural of this region. Molecular genetic data has increasingly been used as support for issues related to biodiversity with great contribution to conservation programs, because of its power to elucidate gene flow, introgression, levels of kinship and hybridization. In forensics, this information has the potential to be used for the control of exotic species and curb trafficking of native species. By sequencing using mitochondrial markers Cyt b and CO II, this work shows the molecular characterization of a mixed group of marmosets found between the forest and a urbanized area close to the Serra dos Orgãos National Park in Rio de Janeiro state. The results showed that the group of marmosets here studied is formed by a male individual with phenotype and genotype matching that of the endangered species C. aurita, among others which belong to the invasive species C. penicillata and C. jacchus. This reinforces the importance of studies aimed at elucidating the dynamics of gene flow and the viability of possible hybrids facing the conservation of native species. From the forensics standpoint, the characterization based on molecular markers, ensures a more comprehensive tool for identifying those species fighting illegal trade and preserving the endangered C. aurita.

Conservation and management of peripheral populations: Spatial and temporal influences on the genetic structure of wood frog (Rana sylvatica) populations

Peripheral populations of wide-ranging species are often of special conservation concern, and knowledge of genetic diversity, gene flow, and historical population dynamics are critical to informed management of these populations. In this study we evaluate patterns of genetic diversity and gene flow among a series of wood frog populations in east-central Missouri where it is a species of conservation concern. Because these populations are on the periphery of the species’ range and are isolated from one another by fragmented landscapes, we expected to see population subdivision with signatures of range-edge effects and isolation by resistance. Our analyses reveal significant interpopulation differentiation and a distinct gradient in diversity where levels of allelic richness and heterozygosity decline as the species boundary is approached. These patterns likely stem from factors characteristic of peripheral populations, including reduced population size, reduced gene flow, and more frequent extinction–recolonization events. Population structure was evident, but isolation by resistance (i.e. fragmentation) was not a significant factor in our focal landscape. Isolation by distance was significant, but the level of population differentiation suggests that gene flow among populations is limited. We hypothesize that the lack of gene flow is due to the absence of available fishless breeding habitats outside of protected, managed lands, and recommend that future management efforts of the wood frog include increasing population connectivity at the landscape scale via the creation and maintenance of fishless aquatic breeding habitat.

Characterization and pilot application of 14 microsatellite loci from the Korean shiner (Coreoleuciscus splendidus)

The Korean shiner (Coreoleuciscus splendidus, Gobioninae), a small freshwater fish native to Korea Peninsula, widely inhabits in most of the major drainages in South Korea. Here we describe the development of 14 novel and polymorphic microsatellites for this species and its effective utilization in estimation of genetic diversity using 72 individuals from three sampling sites in different drainages. Loci were isolated from a microsatellite enrichment procedure using probe-labeled magnetic beads. A total of 242 alleles were detected across all loci with an average of 17.3 alleles per locus ranging 4–32. The loci varied levels of polymorphism as evident from its expected heterozygosity ranging from 0.111 to 0.957. The average pairwise F ST between two populations examined shows significant differentiation (F ST=0.215, p < 0.05). The 14 microsatellite loci developed here will also be useful to explain for the genetic structures among geographically isolated populations and gene flow dynamics within drainages in this species as well as the closely related species.

Spatio-temporal variation in the structure of a chromosomal polymorphism zone in the house mouse

Several long-term temporal analyses of the structure of Robertsonian (Rb) hybrid zones in the western house mouse, Mus musculus domesticus, have been performed. Nevertheless, the detection of gradual or very rapid variations in a zone may be overlooked when the time elapsed between periods of study is too long. The Barcelona chromosomal polymorphism zone of the house mouse covers about 5000, km(2) around the city of Barcelona and is surrounded by 40 chromosome telocentric populations. Seven different metacentrics and mice with diploid numbers between 27 and 40 chromosomes and several fusions in heterozygous state (from one to seven) have been reported. We compare the present (period 2008-2010) and past (period 1996-2000) structure of this zone before examining its dynamics in more detail. Results indicate that there is not a Rb race in this area, which is consistent with the proposal that this zone was probably originated in situ, under a primary intergradation scenario. The lack of individuals with more than five metacentrics in heterozygous state in the current period suggests that selection acted against such mice. By contrast, this situation did not occur for mice with fewer than five fusions in heterozygous condition. Changes in human activity may affect the dynamics of gene flow between subpopulations, thus altering the chromosomal composition of certain sites. Although these local variations may have modified the clinal trend for certain metacentrics, the general staggered structure of the zone has not varied significantly in a decade.

DYNAMICS OF DRIFT, GENE FLOW, AND SELECTION DURING SPECIATION INSILENE

The mechanics of speciation with gene flow are still unclear. Disparity among genes in population differentiation (F(ST)) between diverging species is often interpreted as evidence for semipermeable species boundaries, with selection preventing "key" genes from introgressing despite ongoing gene flow. However, F(ST) can remain high before it reaches equilibrium between the lineage sorting of species divergence and the homogenizing effects of gene flow (via secondary contact). Thus, when interpreting F(ST), the dynamics of drift, gene flow, and selection need to be taken into account. We illustrate this view with a multigenic analyses of gene flow and selection in three closely related Silene species, S. latifolia, S. dioica, and S. diclinis. We report that although S. diclinis appears to have evolved in allopatry, isolation with (bidirectional) gene flow between S. latifolia and S. dioica is likely, perhaps as a result of parapatric speciation followed by more extensive sympatry. Interestingly, we detected the signatures of apparently independent instances of positive selection at the same locus in S. latifolia and S. dioica. Despite gene flow between the species, the adaptive alleles have not crossed the species boundary, suggesting that this gene has independently undergone species-specific (diversifying or parallel) selection.

Joint estimation of contemporary seed and pollen dispersal rates among plant populations

There are few statistical methods for estimating contemporary dispersal among plant populations. A maximum-likelihood procedure is introduced here that uses pre- and post-dispersal population samples of biparentally inherited genetic markers to jointly estimate contemporary seed and pollen immigration rates from a set of discrete external sources into a target population. Monte Carlo simulations indicate that accurate estimates and reliable confidence intervals can be obtained using this method for both pollen and seed migration rates at modest sample sizes (100 parents/population and 100 offspring) when population differentiation is moderate (F(ST) ≥ 0.1), or by increasing pre-dispersal samples (to about 500 parents/population) when genetic divergence is weak (F(ST) = 0.01). The method exhibited low sensitivity to the number of source populations and achieved good accuracy at affordable genetic resolution (10 loci with 10 equifrequent alleles each). Unsampled source populations introduced positive biases in migration rate estimates from sampled sources, although they were minor when the proportion of immigration from the latter was comparatively low. A practical application of the method to a metapopulation of the Australian resprouter shrub Banksia attenuata revealed comparable levels of directional seed and pollen migration among dune groups, and the estimate of seed dispersal was higher than a previous estimate based on conservative assignment tests. The method should be of interest to researchers and managers assessing broad-scale nonequilibrium seed and pollen gene flow dynamics in plants.

High gene flow and metapopulation dynamics detected for three species in a dryland river system

Summary 1. The highly variable hydrology of dryland rivers has important implications for population dynamics in these systems. In western Queensland, fluctuations in sub-population size are likely to lead to local bottlenecks and extinctions, increasing the need for connectivity and gene flow to maintain population viability. 2. Using microsatellite markers, we explored evidence for this metapopulation structure in two species of freshwater fish (Maquaria ambigua and Tandanus tandanus) and one crustacean (Macrobrachium australiense) in a sub-catchment of the upper Murray–Darling Basin, Australia. 3. Overall, we found very weak genetic structure for all three species. Two species (M. ambigua and M. australiense) showed some significant genetic structure that did not correlate with geographic distance. However, decomposed pairwise regression analysis revealed evidence for intense genetic drift at the waterhole scale, suggesting that local bottlenecks are driving what little genetic structure does exist for these species. 4. The results identify the local impact of bottlenecks on genetic diversity, but highlight the importance of gene flow in maintaining population viability in these highly variable systems. As the impacts of bottlenecks are likely to be tempered by gene flow, it is suggested that the maintenance of connectivity is of paramount importance in this dryland system.

Impacts of climate warming on hybrid zone movement: Geographically diffuse and biologically porous “species borders”

The ecology and evolutionary biology of insect–plant associations has realized extensive attention, especially during the past 60 years. The classifications (categorical designations) of continuous variation in biodiversity, ranging from global patterns (e.g., latitudinal gradients in species richness/diversity and degree of herbivore feeding specialization) to localized insect–plant associations that span the biospectrum from polyphenisms, polymorphisms, biotypes, demes, host races, to cryptic species, remain academically contentious. Semantic and biosystematic (taxonomical) disagreements sometimes detract from more important ecological and evolutionary processes that drive diversification, the dynamics of gene flow and local extinctions. This review addresses several aspects of insect specialization, host-associated divergence and ecological (including “hybrid”) speciation, with special reference to the climate warming impacts on species borders of hybridizing swallowtail butterflies (Papilionidae). Interspecific hybrid introgression may result in collapse of multi-species communities or increase species numbers via homoploid hybrid speciation. We may see diverging, merging, or emerging genotypes across hybrid zones, all part of the ongoing processes of evolution. Molecular analyses of genetic mosaics and genomic dynamics with “divergence hitchhiking”, combined with ecological, ethological and physiological studies of “species porosity”, have already begun to unveil some answers for some important ecological/evolutionary questions. (i) How rapidly can host-associated divergence lead to new species (and why doesn't it always do so, e.g., resulting in “incomplete” speciation)? (ii) How might “speciation genes” function, and how/where would we find them? (iii) Can oscillations from specialists to generalists and back to specialists help explain global diversity in herbivorous insects? (iv) How could recombinant interspecific hybridization lead to divergence and speciation? From ancient phytochemically defined angiosperm affiliations to recent and very local geographical mosaics, the Papilionidae (swallowtail butterflies) have provided a model for enhanced understanding of ecological patterns and evolutionary processes, including host-associated genetic divergence, genomic mosaics, genetic hitchhiking and sex-linked speciation genes. Apparent homoploid hybrid speciation in Papilio appears to have been catalyzed by climate warming-induced interspecific introgression of some, but not all, species diagnostic traits, reflecting strong divergent selection (discordant), especially on the Z (= X) chromosome. Reproductive isolation of these novel recombinant hybrid genotypes appears to be accomplished via a delayed post-diapause emergence or temporal isolation, and is perhaps aided by the thermal landscape. Changing thermal landscapes appear to have created (and may destroy) novel recombinant hybrid genotypes and hybrid species.

What can gene flow and recruitment dynamics tell us about connectivity between European hake stocks in the Eastern North Atlantic?

Systematic genetic analyses of fish populations allow the testing of temporal stability in their genetic structures and better understanding their pattern of connectivity. In this study the pattern of gene flow between the two Atlantic stocks of the European hake has been examined for the period 2000–2002. Present analyses indicate that a large genetic homogeneity existed among all Atlantic populations in that period, and that a systematic grouping occurred between Porcupine Bank samples and Cantabric ones. This scenario is congruent with an inter-annual gene flow from central grounds of the northern stock (Porcupine and Great Sole) to Iberian grounds inhabited by the southern stock. Additionally, estimated migration figures were in agreement with the good recruitments observed in the southern stock after 2003 despite the spawning biomass was at its historical minimum. Altogether these results highlight the central role of Porcupine bank and Great Sole in making sustainable both stocks and advocate the integrative management of this hake fishery by means of a multidisciplinary assessment.

REPRODUCTIVE PATTERNS SHAPE INTROGRESSION DYNAMICS AND SPECIES SUCCESSION WITHIN THE EUROPEAN WHITE OAK SPECIES COMPLEX

The reproductive system of hybrids is an important factor shaping introgression dynamics within species complexes. We combined paternity and parentage analyses with previous species characterization by genetic assignment, to directly identify reproductive events that occurred within a stand comprising four European white oak species. Comparing species status of parent pairs provided a precise quantification of hybridization rate, backcrosses, and intraspecific matings in two life stages. The detailed mating system analysis revealed new findings on the dynamics of interspecific gene flow. First, hybrids acted successfully as both male and female during reproduction. They produced acorns and seedlings that were as viable as those sired by purebreds. Second, species maintenance could be due to a relatively low level of interspecific mating contrasting with a large proportion of intraspecific crosses and backcrosses. Despite a high proportion of hybrids and extensive interspecific gene flow, partial species integrity is maintained by genetically controlled pollen discrimination, ensuring preferential matings within purebreds and high parental species fidelity in hybrid reproduction, which impedes complete collapse into a continuous hybrid swarm. Finally, we showed that pollen from the different species had unequal contributions to reproduction suggesting that introgression processes could ultimately lead to extirpation or expansion of some species.

Glyphosate drift promotes changes in fitness and transgene gene flow in canola (Brassica napus) and hybrids

With the advent of transgenic crops, genetically modified, herbicide-resistant Brassica napus has become a model system for examining the risks and potential ecological consequences of escape of transgenes from cultivation into wild compatible species. Escaped transgenic feral B. napus and hybrids with compatible weedy species have been identified outside of agriculture and without the apparent selection for herbicide resistance. However, herbicide (glyphosate) exposure can extend beyond crop field boundaries, and a drift-level of herbicide could function as a selective agent contributing to increased persistence of transgenes in the environment. The effects of a drift level (0·1 × the field application rate) of glyphosate herbicide and varied levels of plant competition were examined on plant fitness-associated traits and gene flow in a simulated field plot, common garden experiment. Plants included transgenic, glyphosate-resistant B. napus, its weedy ancestor B. rapa, and hybrid and advanced generations derived from them. The results of this experiment demonstrate reductions in reproductive fitness for non-transgenic genotypes and a contrasting increase in plant fitness for transgenic genotypes as a result of glyphosate-drift treatments. Results also suggest that a drift level of glyphosate spray may influence the movement of transgenes among transgenic crops and weeds and alter the processes of hybridization and introgression in non-agronomic habitats by impacting flowering phenology and pollen availability within the community. The results of this study demonstrate the potential for persistence of glyphosate resistance transgenes in weedy plant communities due to the effect of glyphosate spray drift on plant fitness. Additionally, glyphosate drift has the potential to change the gene-flow dynamics between compatible transgenic crops and weeds, simultaneously reducing direct introgression into weedy species while contributing to an increase in the transgenic seed bank.

Development, characterization, and transferability of microsatellite markers for Kirengeshoma palmata (Hydrangeaceae)

Microsatellite markers were developed for Kirengeshoma palmata to assess the population genetics and mating pattern of this critically endangered species. • A total of 24 microsatellite markers were developed for K. palmata using an enrichment protocol. These markers were screened in 37 individuals from four populations in China and Japan, and twelve were found to be polymorphic, with the number of alleles per locus ranging from two to eight. All of these primers also amplified in K. koreana. • These microsatellite markers provide a useful tool to investigate the mating system, gene flow, parentage, and population dynamics of Kirengeshoma.

Inter-specific gene flow dynamics during the Pleistocene-dated speciation of forest-dependent mosquitoes in Southeast Asia

Tropical forests have undergone repeated fragmentation and expansion during Pleistocene glacial and interglacial periods, respectively. The effects of this repeated forest fragmentation in driving vicariance in tropical taxa have been well studied. However, relatively little is known about how often this process results in allopatric speciation, since it may be inhibited by recurrent gene flow during repeated secondary contact, or to what extent Pleistocene-dated speciation results from ecological specialization in the face of gene flow. Here, divergence times and gene flow between three closely-related mosquito species of the Anopheles dirus species complex endemic to the forests of Southeast Asia, are inferred using coalescent based Bayesian analysis. An Isolation with Migration model is applied to sequences of two mitochondrial and three nuclear genes, and 11 microsatellites. The divergence of An. scanloni has occurred despite unidirectional nuclear gene flow from this species into An. dirus. The inferred asymmetric gene flow may result from the unique evolutionary adaptation of An. scanloni to limestone karst habitat, and therefore the fitness advantage of this species over An. dirus in regions of sympatry. Mitochondrial introgression has led to the complete replacement of An. dirus haplotypes with those of An. baimaii through a recent (approximately 62 kya) selective sweep. Speciation of An. baimaii and An. dirus is inferred to have involved allopatric divergence throughout much of the Pleistocene. Secondary contact and bidirectional gene flow has occurred only within the last 100 000 years, by which time the process of allopatric speciation seems to have been largely completed.

Favourable habitats for Coffea inter‐specific hybridization in central New Caledonia: combined genetic and spatial analyses

Summary 1. Human disturbance of natural habitats has increasingly promoted hybridization between previously isolated species. Coffee trees (Coffea canephora, C. liberica and C. arabica) have been introduced into New Caledonia for cultivation since the 1850s. Many plantations have since been abandoned, leaving the cultivars to evolve in natural conditions. This historical situation and the local environmental conditions have led to gene flow between sympatric species and the creation of hybrid zones which can be considered as a natural laboratory for studying gene flow dynamics. Our objectives were to assess the nature of these hybridizations and to model the distribution of habitats favourable for these hybrid zones at a regional scale. 2. We analysed a tri‐specific model population with 26 microsatellite markers using a multilocus analysis approach. We applied Bayesian methods to characterize the species identity of founder individuals and identify inter‐specific hybrids. A high level of genetic diversity and inter‐specific hybridization was observed in the population. To evaluate the presence of other favourable environments in the local area, a geographic information system was used to spatially differentiate the phenomenon and optimize future hybrid collecting missions. We constructed a predictive distribution model based on observation and environmental expertise (climatic parameters, physical parameters and landcover) at four reference sites of the hybrid zone. 3. At all four sites the Coffea species were found to be involved in inter‐specific hybridization, with one population, in particular, revealing high genetic diversity. According to the environmental expertise, 40% of the studied region appeared to be favourable for this phenomenon and the model was validated with a prediction accuracy of 79%. 4. Synthesis and applications. The use of microsatellite markers was efficient for assessing the nature and extent of coffee tree hybridization events. The environmental expertise and model allowed comparisons between New Caledonia and Africa ecological niches. This methodology may be recommended for better management of de novo in situ coffee genetic resources and applied to other plants to provide insight into the impact of adaptation to new environment. Combining environmental and species biological parameters would help in analysing modifications in plant reproductive behaviour induced by global climate change.

Eighteen SSR-primers for tetraploid Adansonia digitata and its relatives

Co-dominant markers suitable for molecular ecological studies in the genus Adansonia are highly desirable in order to be able to address a number of interesting research questions related to the special life history traits, gene flow, and distribution dynamics of the Adansonia species. This note presents a set of 18 SSR-primers developed for Adansonia digitata, and tested for cross-amplification on all members of the Adansonia genus. All reported primers were found to amply loci with more than two alleles per locus in Adansonia digitata, reflecting its tretraploid nature. Segregation of alleles in open pollinated progenies from trees with four alleles per locus indicated polysomic inheritance for 14 of the 18 loci.