Genetic structure in two meadow varieties ofEuphrasia stricta on the Baltic island of Gotland (Sweden) and implications for conservation

The annual hemiparasiteEuphrasia stricta occurs on Gotland in two early-flowering meadow varieties.E. stricta var.suecica is on the Swedish red-list as endangered, occurring in Sweden only on the Baltic island of Gotland. It probably has near relatives east of the Baltic proper. The other variety,E. stricta var.tenuis, has a wider distribution occurring almost all over Sweden, but is declining in abundance. Both varieties have close morphological similarities and habitat preferences, raising questions about which level conservation efforts should be focused on, varieties or populations. In this study we describe the genetic structure between and within these two varieties using amplified fragment length polymorphism, AFLP.F _ST between varieties is 0.14, and between populations within the varietiesE. stricta var.suecica and var.tenuis F _ST is 0.60 and 0.26 respectively. The partitioning of gene diversity to different levels shows that 14% of the genetic diversity occurs between varieties, 42% between populations within varieties, and 44% within populations. Significant genetic differentiation was detected between varieties, populations and subpopulations within populations using a constrained principal coordinate analysis. We suggest that all of the existing populations of these two varieties on Gotland should be preserved, since they are few (6E. stricta var.suecica and 5E. stricta var.tenuis) and much of the genetic diversity is partitioned between populations.     

DIFFERENTIATION AMONG NINE POPULATIONS OF PHLOX. I. ELECTROPHORETIC AND QUANTITATIVE VARIATION

The organization of genetic variation in Phlox drummondii was investigated using both allozyme electrophoresis and quantitative genetics. Variation at five polymorphic enzyme loci was characterized in nine populations, and variation in 16 morphological and life-history characters was examined using an analysis of full- and half-sibs in seven populations. Significant levels of genetic variation were found at enzyme loci and for metric characters. Significant heritabilities were observed for 15 of the 16 characters examined. Genetic differences among populations were revealed both by Nei's genetic distance and by phenotypic differences, summarized by discriminant analysis. Partitioning variance in allozyme frequencies among hierarchical levels of genetic organization indicated that 94% of this variance lay within populations, 4% between populations within varieties, and 2% between varieties. Partitioning phenotypic variance for metric characters indicated that 73% lay within populations, 24% lay between populations within varieties, and 3% lay between varieties. Thus, both electrophoretic and metric characters indicated that despite extensive genetic differentiation among populations, most of the evolutionary potential of the species lies within populations.     

云南岩陀及其近缘种质资源群体表型多样性

为有效保护和持续利用药用植物云南岩陀及其近缘种质资源提供基础数据,采用巢式方差分析和聚类分析等方法对岩陀及其近缘种质资源共4个种(包括变种)的15个居群150个单株16种表型性状进行表型多样性分析.结果表明:不同种间表型性状变异均超过20％,变异由大到小依次为光腹鬼灯檠、岩陀、羽叶鬼灯檠、七叶鬼灯檠;居群间表型性状变异较高,其地上部分干重、单株根状茎数变异较大,变异系数均超过50％;小叶表面毛被状态变异系数为100％、小叶背沿脉柔毛色变异系数为0,因此这些性状为种和变种分类的重要依据;4个种的居群内变异系数均大于居群间,变异主要来源于居群内.种的表型多样性指数相对较高,其中根粗最高,叶表面毛被状态和叶背面沿脉柔毛色最低,总体平均多样性指数为1.39;不同种间表型多样性指数变化在1.23-1.44,岩陀最高,七叶鬼灯檠最低;通过聚类分析可将15个居群分为4类.结果暗示:岩陀及其近缘种质资源的遗传改良应适当地减少抽样居群数,增加居群内的家系数,重视居群内优良单株的选择;种质资源的保护应尽量保护一个居群的完整性.     

Systematics of the genus Floridichthys

Samples representing the three nominal subspecies of Floridichthys carpio were examined electrophoretically. Although the populations in Florida could not be distinguished completely from the populations in Yucatan by morphology, 5 of the 30 electrophoretic characters demonstrated fixed differences between Florida and Yucatan populations. Based on the observed genetic differentiation between Florida and Yucatan populations and the absence of genetic differentiation within those populations, we conclude that the Yucatan population has diverged to the species level. We, therefore, propose to elevate the nominal Yucatan subspecies Floridichthys carpio polyommus to a species status.     

Allozyme diversity in Pinus virginiana (Pinaceae): intraspecific and interspecific comparisons

Two of the four members of subsection Contortae of the genus Pinus occur in the southeastern United States: Pinus virginiana, which ranges throughout the southern and central Appalachian Mountains, and P. clausa, which is restricted to Florida and southern Alabama. We examined allozyme variation within P. virginiana and genetic relationships between this species and the two varieties of P. clausa (var. clausa and var. immuginata). P. virginiana maintains more genetic diversity at both the species (Hes = 0.139) and population (Hep = 0.128) levels than the other three species in the subsection, which may reflect the combination of its widespread distribution and the absence of cone serotiny. Genetic differentiation among populations in P. virginiana was relatively low (GST = 0.053), but significant contrasts in allozyme frequencies and genetic diversity were apparent between populations to the northwest vs. outheast of the Appalachian Mountains. These regional differences likely resulted initially from historical processes that occurred during the Pleistocene and early Holocene, and have been reinforced by modern selective pressures and barriers to gene flow. The mean genetic distance between populations of P. virginiana and P. clausa (D = 0.071) was greater than that between populations of the two varieties of P. clausa (D = 0.012), which suggests that the two varieties diverged at some point after the separation of the two species.     

Glacial History Affected Phenotypic Differentiation in the Alpine Plant,Campanula thyrsoides

Numerous widespread Alpine plant species show molecular differentiation among populations from distinct regions. This has been explained as the result of genetic drift during glacial survival in isolated refugia along the border of the European Alps. Since genetic drift may affect molecular markers and phenotypic traits alike, we asked whether phenotypic differentiation mirrors molecular patterns among Alpine plant populations from different regions. Phenotypic traits can be under selection, so we additionally investigated whether part of the phenotypic differentiation can be explained by past selection and/or current adaptation. Using the monocarpic Campanula thyrsoides as our study species, a common garden experiment with plants from 21 populations from four phylogeographic groups located in regions across the Alps and the Jura Mountains was performed to test for differentiation in morphological and phenological traits. Past selection was investigated by comparing phenotypic differentiation among and within regions with molecular differentiation among and within regions. The common garden results indicated regional differentiation among populations for all investigated phenotypic traits, particularly in phenology. Delayed flowering in plants from the South-eastern Alps suggested adaptation to long sub-mediterranean summers and contrasted with earlier flowering of plants experiencing shorter growing seasons in regions with higher elevation to the West. Comparisons between molecular and phenotypic differentiation revealed diversifying selection among regions in height and biomass, which is consistent with adaptation to environmental conditions in glacial refugia. Within regions, past selection acted against strong diversification for most phenotypic traits, causing restricted postglacial adaptation. Evidence consistent with post-glacial adaptation was also given by negative correlation coefficients between several phenotypic traits and elevation of the population''s origin. In conclusion, our study suggests that, irrespective of adaptation of plants to their current environment, glacial history can have a strong and long-lasting influence on the phenotypic evolution of Alpine plants.     

Population genetic structure of orchid bees (Euglossini) in anthropogenically altered landscapes

Habitat degradation and fragmentation are widespread phenomena in tropical regions. Negative effects on the biota are numerous, ranging from interruption of gene flow among populations, to the loss of genetic diversity within populations, to a decline in species richness over time. Orchid bees (Hymenoptera: Apidae: Euglossini) are of major conservation interest due to their function as pollinators of numerous orchid species and other tropical plants. Here, we used microsatellite markers to investigate the effects of geographic distance and habitat fragmentation on gene flow among populations. Populations of Euglossa dilemma in three geographic regions??the Yucat??n peninsula (Mexico), Veracruz (Mexico), and Florida (USA)??were genetically structured predominantly across the regions, with the strength of differentiation among populations being positively correlated with geographic distance. Within geographic regions only little substructure was found, suggesting that dispersal is substantial in the absence of geographic or ecological barriers. In a second study, patterns of genetic differentiation among eight species of Euglossa were not related to habitat fragmentation following deforestation in southern Mexico (Veracruz). Specifically, most bee populations in the 9,800?ha forest remnant of Los Tuxtlas (Volcano San Martin) were neither differentiated from, nor had less genetic diversity than, populations in near-continuous forest separated from Los Tuxtlas by 130?km of agricultural land. Either occasional long distance dispersal across open areas has buffered the expected genetic effects of fragmentation, or the history of fragmentation in southern Mexico is too recent to have caused measurable shifts in allelic composition.     

Genetic diversity and population structure of Chinese <Emphasis Type="Italic">Lentinula edodes</Emphasis> revealed by InDel and SSR markers

Genetic diversity and population structure of 88 Chinese Lentinula edodes strains belonging to four geographic populations were inferred from 68 Insertion-Deletion (InDel) and two simple sequence repeat (SSR) markers. The overall values of Shannon’s information index and gene diversity were 0.836 and 0.435, respectively, demonstrating a high genetic diversity in Chinese L. edodes strains. Among the four geographic populations, the Central China population displayed a lower genetic diversity. Multiple analyses resolved two unambiguous genetic groups that corresponded to two regions from which the samples were collected—one was a high-altitude region (region 1) and the other was a low-altitude region (region 2). Results from analysis of molecular variance suggested that the majority of genetic variation was contained within populations (74.8 %). Although there was a strong genetic differentiation between populations (F _ST ?=?0.252), the variability of ITS sequences from representative strains of the two regions (<3 %) could not support the existence of cryptic species. Pairwise F _ST values and Nei’s genetic distances showed that there were relatively lower genetic differentiations and genetic distances between populations from the same region. Geographic distribution could play a vital role in the formation of the observed population structure. Mycelium growth rate and precocity of L. edodes strains displayed significant differences between the two regions. Strains from region 2 grew faster and fructified earlier, which could be a result of adaptation to local environmental factors. To the best of our knowledge, this was the first study on the genetic structure and differentiation between populations, as well as the relationship between genetic structure and phenotypic traits in L. edodes.     

Hierarchical components of genetic variation at a species boundary: population structure in two sympatric varieties of Lupinus microcarpus (Leguminosae)

Lupinus microcarpus is a self-compatible annual plant that forms a species complex of morphologically variable but indeterminate varieties. In order to examine the hypothesis that varieties of L. microcarpus comprise genetically differentiated and reproductively isolated species, populations of L. microcarpus var. horizontalis and var. densiflorus were sampled from an area of sympatry in central California and genotyped using six microsatellite loci. Bayesian clustering divided the total sample into two groups corresponding to the named varieties with extremely low levels of inferred coancestry. Similarly, maximum likelihood and distance methods for genetic assignment placed individuals in two nonoverlapping groups. Evidence for isolation by distance (IBD) within each variety was found at shorter distance classes, but varieties remained differentiated in sympatry. Furthermore, coalescent estimates of divergence time indicate separation within the past 950-5050 generations, with minimal gene flow after divergence. A four-level hierarchical analysis of molecular variance (amova) found significant levels of genetic differentiation among varieties (theta(P) = 0.292), populations within varieties (theta(S) = 0.449), subpopulations within populations (theta(SS) = 0.623), and individuals within subpopulations (f = 0.421); but the greatest degree of differentiation was at the subpopulation level. Although it is sometimes assumed that the magnitude of genetic differences (e.g. F(ST)) should be greater between species than among populations or subpopulations of the same species, shared ancestral polymorphism may lead to relatively low levels of differentiation at the species level, even as the stochastic effects of genetic drift generate higher levels of differentiation at lower hierarchical levels. These results suggest that L. microcarpus var. horizontalis and var. densiflorus are recently diverged yet reproductively isolated species, with high levels of inbreeding resulting from the combined effects of limited gene flow, demographic bottlenecks, and partial selfing in finite, geographically structured populations.     

Population variation and phylogeny in the endangered <Emphasis Type="BoldItalic">Chamaesyce skottsbergii</Emphasis> (Euphorbiaceae) based on RAPD and ITS analyses

Chamaesyce skottsbergii var. skottsbergii is federally listed as an endangered taxon, and is found in small and isolated populations restricted to calcareous soils in dry shrubland habitats on the Hawaiian islands of Oahu and Molokai. Concern over the genetic relationship among these disjunct populations arose as a result of threats to the habitat of the Oahu population. The populations were examined using random amplified polymorphic DNA (RAPD) markers and sequence analysis of the internal transcribed spacer (ITS) region of the rDNA cistron. Chamaesyce skottsbergii var. vaccinioides, a closely related variety found in several small populations on Molokai, was used for baseline comparison of the genetic divergence among populations. RAPD analysis demonstrated that variation within and among populations is the highest for any Hawaiian species examined. Polymorphism was greater than 95% within populations and was 99.4% at the species level. Similarly, measures of genetic similarity indicate that differentiation among these populations is higher than is known for some species. Both RAPD and ITS sequence analysis indicate that populations of C. skottsbergii var. skottsbergii on Oahu and Molokai are genetically distinct, and the extent of this genetic differentiation supports the recognition of these populations as distinct varieties. The Molokai population is in fact much more closely related to var. vaccinioides than to var. skottsbergii on Oahu, and thus should be recognized by the previously used variety name, C. skottsbergii var. audens. Further conservation measures for each of the varieties are addressed.     

Pollinator-mediated mating restriction between sympatric varieties of yellow lady’s slipper orchids (Cypripedium parviflorum Salisb.)

A predominant theme in the study of orchid evolution has been the importance of floral traits contributing to pollinator-mediated isolating barriers (i.e., floral isolation). However, few studies have quantified the contribution of floral isolation in sympatric orchid populations. Cypripedium parviflorum vars. makasin and pubescens are excellent taxa to test the strength of floral isolation because of their recent phylogenetic separation, overlapping flowering phenologies, and sympatric populations that can lack intermediate morphologies. In this paper, we use sympatric populations to (1) test for pre-mating and early-acting post-mating reproductive isolating barriers, (2) quantify genetic differentiation among populations using allozyme loci, and (3) document floral size differences between varieties. Pollen tracking experiments using fluorescent powders revealed minimal inter-varietal pollen movement. Across two sympatric sites, only 4 inter-varietal pollinations were observed among 52 var. makasin pollinations and 40 var. pubescens pollinations. All of these inter-varietal pollinations had var. makasin as the pollen donor. In contrast, artificial crosses within and between the varieties revealed no statistically significant differences in fruit set, seed weight, or embryo morphology. Allozyme data are consistent with restricted inter-varietal gene flow, showing strong allele frequency differences between the varieties across multiple loci. In a clustering analysis, these differences caused the varieties to group taxonomically and not by their geographic location. These data along with statistically significant morphological differences between the varieties strongly suggest the existence of a pollinator-mediated isolating barrier. The possible nature of the isolating barrier is discussed as well as the likelihood of other late acting post-zygotic barriers.     

Genetic diversity analysis of Hepatacodium miconioides at different altitude in Tiantai Mountain, Zhejiang Province, China and its relationship with environmental factors

The genetic diversity within and among populations of Hepatacodium miconioides collected at three different altitudes in Tiantai Mountain, Zhejiang Province and its relationships to environmental factors were analyzed by random amplified polymorphic DNA (RAPD) technique. Amplification using 12 random primers of 60 plants and 122 repetitive loci were produced. The percentage of polymorphic loci of three populations ranged from 18.85% to 23.77% with an average of 21.86%, indicating the relatively low genetic diversity of H. miconioides. The average Shannon index of phenotypic diversity (0.1329) and Nei index (0.0925) within populations were relatively low. A distinct genetic differentiation existed among populations of H. miconioides in spite of the relatively small geographical distribution. The average genetic diversity within populations of H. miconioides accounted for 33.58% of the total genetic diversity while the genetic diversity among populations accounted for 66.42% as estimated by the Shannon index of phenotypic diversity, The genetic differentiation among populations of H. miconioides was 0.6546, as estimated by Nei index. The gene flow estimated from G _ST was only 0.2656 and it indicated that gene flow among populations of H. miconioides was relatively low. The mean value of the genetic identity among populations of H. miconioides was 0.7126 and the average of genetic distance of H. miconioides was 0.3412. The genetic identity between populations at the elevation of 990 m and at the elevation of 780 m was the highest. The genetic identity between population at the elevation 500 m and other two populations was relatively low. The correlation analysis showed that the genetic diversity within populations was significantly related with the soil total nitrogen.     

Genetic variability is correlated with population size and reproduction in American wild-rice (Zizania palustris var. palustris, Poaceae) populations

American wild-rice (Zizania palustris var. palustris) has served as a staple for indigenous North Americans for thousands of years, but has had significant habitat losses in recent centuries. We investigated genetic variability among 17 wild-rice populations in northern Wisconsin using 13 isozyme markers. We then compared these genetic patterns to differences in habitat and population characteristics and phenotypic variation in plant growth and reproduction across sites. Wild-rice's mean genetic diversity (0.15) is moderate compared to wind-pollinated outcrossers but lower than the mean (0.20) reported for the Poaceae. Estimated inbreeding coefficients within populations (f) average 0.12 but vary greatly among the populations (from -0.44-0.52), suggesting heterogeneous population histories. Larger populations in larger lakes express higher levels of genetic variability and smaller inbreeding coefficients than smaller or more isolated populations. The number of panicles per plant is also higher in populations with greater genetic variability. Estimated genetic differentiation among the 17 populations (F(ST)) was high (0.30), suggesting limited gene flow among drainages. Wild-rice population size and degree of isolation have opposing effects on its genetic variability, and plant performance is positively associated with genetic variability.     

Contrasting Levels of Variation in Neutral and Quantitative Genetic Loci on Island Populations of Moor Frogs (<Emphasis Type="Italic">Rana arvalis</Emphasis>)

Reduced levels of genetic variability and a prominent differentiation in both neutral marker genes and phenotypic traits are typical for many island populations as compared to their mainland conspecifics. However, whether genetic diversity in neutral marker genes reflects genetic variability in quantitative traits, and thus, their evolutionary potential, remains typically unclear. Moreover, the phenotypic differentiation on islands could be attributable to phenotypic plasticity, selection or drift; something which seldom has been tested. Using eight polymorphic microsatellite loci and quantitative genetic breeding experiments we conducted a detailed comparison on genetic variability and differentiation between Nordic islands (viz. Gotland, Öland and Læsø) and neighbouring mainland populations of moor frogs (Rana arvalis). As expected, the neutral variation was generally lower in island than in mainland populations. But as opposed to this, higher levels of additive genetic variation (V _A) in body size and tibia length were found on the island of Gotland as compared to the mainland population. When comparing the differentiation seen in neutral marker genes (F _ST) with the differentiation in genes coding quantitative traits (Q _ST) two different evolutionary scenarios were found: while selection might explain a smaller size of moor frogs on Gotland, the differentiation seen in tibia length could be explained by genetic drift. These results highlight the limited utility of microsatellite loci alone in inferring the causes behind an observed phenotypic differentiation, or in predicting the amount of genetic variation in ecologically important quantitative traits.     

Joint analysis of phenotypic and molecular diversity provides new insights on the genetic variability of the Brazilian physic nut germplasm bank

The genetic variability of the Brazilian physic nut (Jatropha curcas) germplasm bank (117 accessions) was assessed using a combination of phenotypic and molecular data. The joint dissimilarity matrix showed moderate correlation with the original matrices of phenotypic and molecular data. However, the correlation between the phenotypic dissimilarity matrix and the genotypic dissimilarity matrix was low. This finding indicated that molecular markers (RAPD and SSR) did not adequately sample the genomic regions that were relevant for phenotypic differentiation of the accessions. The dissimilarity values of the joint dissimilarity matrix were used to measure phenotypic + molecular diversity. This diversity varied from 0 to 1.29 among the 117 accessions, with an average dissimilarity among genotypes of 0.51. Joint analysis of phenotypic and molecular diversity indicated that the genetic diversity of the physic nut germplasm was 156% and 64% higher than the diversity estimated from phenotypic and molecular data, respectively. These results show that Jatropha genetic variability in Brazil is not as limited as previously thought.     

Genetic Variability and Population Structure of the Mushroom Pleurotus eryngii var. tuoliensis

The genetic diversity of 123 wild strains of Pleurotus eryngii var. tuoliensis, which were collected from nine geographical locations in Yumin, Tuoli, and Qinghe counties in the Xinjiang Autonomous Region of China, was analysed using two molecular marker systems (inter-simple sequence repeat and start codon targeted). At the variety level, the percentage of polymorphic loci and Nei’s gene diversity index for P. eryngii var. tuoliensis was 96.32% and 0.238, respectively. At the population level, Nei’s gene diversity index ranged from 0.149 to 0.218 with an average of 0.186, and Shannon''s information index ranged from 0.213 to 0.339 with an average of 0.284. These results revealed the abundant genetic variability in the wild resources of P. eryngii var. tuoliensis. Nei’s gene diversity analysis indicated that the genetic variance was mainly found within individual geographical populations, and the analysis of molecular variance revealed low but significant genetic differentiation among local and regional populations. The limited gene flow (Nm = 1.794) was inferred as a major reason for the extent of genetic differentiation of P. eryngii var. tuoliensis. The results of Mantel tests showed that the genetic distance among geographical populations of P. eryngii var. tuoliensis was positively correlated with the geographical distance and the longitudinal distances (r_Go = 0.789 and r_Ln = 0.873, respectively), which indicates that geographical isolation is an important factor for the observed genetic differentiation. Nine geographical populations of P. eryngii var. tuoliensis were divided into three groups according to their geographical origins, which revealed that the genetic diversity was closely related to the geographical distribution of this wild fungus.     

Population Genomics of the Euryhaline Teleost Poecilia latipinna

Global climate change and increases in sea levels will affect coastal marine communities. The conservation of these ecologically important areas will be a challenge because of their wide geographic distribution, ecological diversity and species richness. To address this problem, we need to better understand how the genetic variation of the species in these communities is distributed within local populations, among populations and between distant regions. In this study we apply genotyping by sequencing (GBS) and examine 955 SNPs to determine Sailfin molly (Poecilia latipinna) genetic diversity among three geographically close mangrove salt marsh flats in the Florida Keys compared to populations in southern and northern Florida. The questions we are asking are whether there is sufficient genetic variation among isolated estuarine fish within populations and whether there are significant divergences among populations. Additionally, we want to know if GBS approaches agree with previous studies using more traditional molecular approaches. We are able to identify large genetic diversity within each saltmarsh community (π ≈ 36%). Additionally, among the Florida Key populations and the mainland or between southern and northern Florida regions, there are significant differences in allele frequencies seen in population structure and evolutionary relationships among individuals. Surprisingly, even though the cumulative F_ST value using all 955 SNPs within the three Florida Key populations is small, there are 29 loci with significant F_ST values, and 11 of these were outliers suggestive of adaptive divergence. These data suggest that among the salt marsh flats surveyed here, there is significant genetic diversity within each population and small but significant differences among populations. Much of the genetic variation within and among populations found here with GBS is very similar to previous studies using allozymes and microsatellites. However, the meaningful difference between GBS and these previous measures of genetic diversity is the number of loci examined, which allows more precise delineations of population structure as well as facilitates identifying loci with excessive F_ST values that could indicate adaptive divergence.     

Genetic Structure Is Associated with Phenotypic Divergence in Floral Traits and Reproductive Investment in a High-Altitude Orchid from the Iron Quadrangle,Southeastern Brazil

Knowledge of the role of Neotropical montane landscapes in shaping genetic connectivity and local adaptation is essential for understanding the evolutionary processes that have shaped the extraordinary species diversity in these regions. In the present study, we examined the landscape genetics, estimated genetic diversity, and explored genetic relationships with morphological variability and reproductive strategies in seven natural populations of Cattleya liliputana (Orchidaceae). Nuclear microsatellite markers were used for genetic analyses. Spatial Bayesian clustering and population-based analyses revealed significant genetic structuring and high genetic diversity (He = 0.733 ± 0.03). Strong differentiation was found between populations over short spatial scales (FST = 0.138, p < 0.001), reflecting the landscape discontinuity and isolation. Monmonier´s maximum difference algorithm, Bayesian analysis on STRUCTURE and principal component analysis identified one major genetic discontinuity between populations. Divergent genetic groups showed phenotypic divergence in flower traits and reproductive strategies. Increased sexual reproductive effort was associated with rock outcrop type and may be a response to adverse conditions for growth and vegetative reproduction. Here we discuss the effect of restricted gene flow, local adaptation and phenotypic plasticity as drivers of population differentiation in Neotropical montane rock outcrops.     

Phenotypic plasticity and gene diversity in Pistacia lentiscus L. along environmental gradients in Israel

The Mediterranean common shrub Pistacia lentiscus is distributed in a wide range of habitats along the climatic gradient in Israel. We studied the factors that may shape its morphological, physiological, and genetic differentiation. We examined the phenotypic and molecular genetic variability among and within the six Israeli populations as correlated with the local environmental conditions. The genetic structure of the shrub on the island of Cyprus was also examined. Plant morphological parameters correlated significantly with the local environmental conditions, especially with the annual precipitation and temperature. Gene diversity did not differ significantly among locations, and, hence, no differentiation among Israeli populations or between populations in Israel and Cyprus was found. The major part of the molecular variance (69%) was found within the populations, 22% of the variance was found between Israel and Cyprus and 9% among the populations within the region. Gene flow estimates among all the tested populations were high with no indication for the isolation by distance. We did not find any pattern of ecologically related genetic differentiation; hence, the morphological and physiological differences are probably due to phenotypic plasticity. It seems that the ability of P. lentiscus to express the different phenotypes in response to the varying conditions in the Mediterranean region is an adaptive trait in a species that is characterized by intensive gene flow.