Pattern of natural introgression in a <Emphasis Type="Italic">Nothofagus</Emphasis> hybrid zone from South American temperate forests

Interspecific gene flow is a common phenomenon in Nothofagaceae species; however, the dynamics of introgression in hybrid zones remains largely unknown. We focused on two ecologically and morphologically different Nothofagus species from Patagonia, Nothofagus nervosa and Nothofagus obliqua. In a natural hybrid zone, we established two plots 280 m apart in altitude (ca. 1.9 °C difference in mean temperature), and two subplots which captured microsite variation (abundance and spatial distribution of species and predominance of wind direction). We used intensive sampling of individuals (2055, including adults and regeneration) and molecular genotyping of 6 highly species-specific nuclear microsatellites for the identification and classification of hybrids, based on estimates of ancestry and interclass heterozygosity. We evaluated the relative contribution of our sampling effects to variation in hybrid incidence and direction of introgression using generalized linear mixed effects models. We determined that introgressive hybridization occurs at a global rate of 7.8% and that variation was mostly explained by plots (frequency at low altitude was approximately twice that found at high altitude), while it was less influenced by subplots. The high altitude plot was dominated by late-generation backcrosses to N. obliqua (asymmetric bimodality), whereas the low altitude plot consisted of intermediate hybrids (unimodality) and showed asymmetry for introgression between subplots. Differences were not detected between adults and regeneration, suggesting early-acting reproductive isolating barriers. F1 hybrids occur at a global frequency of 3.8%, and are fertile, as the detection of first- and late-generation hybrids indicates.     

Phylogeography and historical demography of the orchid bee <Emphasis Type="Italic">Euglossa iopoecila</Emphasis>: signs of vicariant events associated to Quaternary climatic changes

The aim of this study was to investigate whether Pleistocene climatic instability influenced the phylogeographic structure and historical demography of an endemic Atlantic Forest (AF) orchid bee, Euglossa iopoecila Dressler, which shows two main patterns of integument colors over of its geographical distribution. We based our analysis on the concatenated sequence of four mtDNA segments belonging to genes 16S (357 bp), Cytb (651 bp) and COI (1206 bp), totaling 2234 bp. Samples of E. iopoecila populations were collected in 14 AF remnants along its geographic distribution. Median-Joining haplotype networks, SAMOVA and BAPS results indicated three lineages (southern, central and northern clusters) for E. iopoecila, with two important phylogeographic ruptures. We found higher genetic diversity among samples collected in the central region of the AF, which coincides with predicted areas of climatic stability, according to recent AF stability–extinction model. The demographic analysis suggests that only the southern cluster had undergone recent population expansion, which probably started after the last glacial maximum (LGM). Our data suggest that the differentiation observed in the three mitochondrial lineages of E. iopoecila is the result of past disconnections and multiple extinction/recolonization events involving climate fluctuations. In terms of conservation, we would emphasize the importance of considering: (1) the region of the central clade as the location of the highest genetic diversity of mtDNA of E. iopoecila populations; (2) the philopatric behavior of females that tends to restrict mtDNA gene flow in particular, with direct implications for the conservation of the total genetic diversity in euglossine populations.     

Conservation genetics of rare trees restricted to subtropical montane cloud forests in southern China: a case study from <Emphasis Type="Italic">Quercus arbutifolia</Emphasis> (Fagaceae)

Montane cloud forests (MCFs), with their isolated nature, offer excellent opportunities to study the long-term effects of habitat fragmentation and the impacts of climate change. Quercus arbutifolia is a rare oak in MCFs of southern China and Vietnam. Its isolated populations, small population size and unique ecological niche make this species vulnerable to climate change and habitat loss. In this study, we used chloroplast (cpDNA) and nuclear (ITS) DNA sequences to investigate genetic divergence patterns and demographic history of five of the six known populations of Q. arbutifolia. Considering its small population size and fragmentation, Q. arbutifolia has unexpectedly high genetic diversity. The time since the most recent common ancestor of all cpDNA haplotypes was c. 10.25 Ma, and the rapid diversification of haplotypes occurred during the Quaternary. The maximum clade credibility chronogram of cpDNA haplotypes suggests that the DM population (Daming Mountain, Guangxi province) diverged early and rapidly became isolated from other populations. The Pearl River drainage system may have been the main geographic barrier between DM and other populations since the late Miocene. ITS data suggests that population expansion occurred during the last interglacial of the Quaternary. The combined effects of pre-Quaternary and Quaternary climatic and geological changes were the main drivers to the current genetic diversity and distribution pattern of Q. arbutifolia. Because of the high between-population genetic differentiation and high within-population genetic diversity of Q. arbutifolia, conservation efforts should be implemented for all populations, but if conservation resources are limited, populations DM, YZ (Mang Mountain, Hunan province) and ZZ (Daqin Mountain, Fujian province) should have priority.     

Genetic diversity of endangered orchid <Emphasis Type="Italic">Phaius australis</Emphasis> across a fragmented Australian landscape

Historical events such as colonisation, spatial distribution across different habitats, and contemporary processes, such as human-mediated habitat fragmentation can leave lasting imprints on the population genetics of a species. Orchids currently comprise 17% of threatened flora species in Australia (Environment Protection and Biodiversity Conservation Act 1999) due to the combination of fragmentation and illegal harvesting (Benwell in Recovery plan, swamp orchids Phaius australis, Phaius tancarvilliae, NSW National Parks and Wildlife Service, Sydney, 1994; Jones in A complete guide to native orchids of Australia including the island territories, 2nd edn, Reed Natural History, Sydney, 2006; DE in Phaius australis in species profile and threats database, Department of the Environment. http://www.environment.gov.au/sprat, 2015). The federally endangered Swamp Orchid Phaius australis has a disjunct distribution across an almost 2000 km latitudinal range along Australia’s east coast but it was estimated that 95% of the populations have been lost since European settlement (Benwell 1994). Phaius australis is endangered due to illegal collection and habitat loss that has resulted in limited connectivity between populations, in ecosystems that are vulnerable to climate change. Thus the genetic impacts of its history combined with more recent fragmentation may have impacts on its future viability especially in light of changing environmental conditions. Thirty-four populations were sampled from tropical north Queensland to the southern edge of the subtropics in New South Wales. Population genetics analysis was conducted using 13 polymorphic microsatellite markers developed for the species using NextGen sequencing. Spatial genetic patterns indicate post-colonisation divergence from the tropics southwards to its current climate niche limits. Genetic diversity is low across all populations (A?=?1.5, H _e  = 0.171), and there is little evidence of genetic differentiation between regions. Consistent with population genetic theory, the historic loss of populations has resulted in significantly lower genetic diversity in small populations compared to large (P, A, He; p?<?0.05). The viability and persistence of P. australis populations now and in a changing climate are discussed in the context of conservation priorities.     

Effects of Pleistocene climate change on genetic structure and diversity of <Emphasis Type="Italic">Shorea macrophylla</Emphasis> in Kalimantan Rainforest

The island of Borneo is the diversity center of the Dipterocarpaceae, the most important family of tropical rainforest trees in Southeast Asia. However, changes in land use and climate have affected dipterocarp distributions on the island, raising concerns about the vulnerability (inter alia) of the endemic riparian species Shorea macrophylla. Thus, to aid conservation efforts, we have investigated the genetic diversity, structure, and demographic history of S. macrophylla. The species’ genetic diversity and structure in Kalimantan (part of Indonesia, covering 75% of the island) were explored by examining genotypes of 377 individuals representing 13 populations in three regions (Northeast, Central, and West Kalimantan) using 14 newly developed microsatellite loci. Higher genetic diversity was found, at all loci, in samples from Northeast Kalimantan than in samples from the other regions. Moderate genetic differentiation between populations was detected (F_ST 0.093). Bayesian clustering, principal coordinate, and neighbor joining tree analyses of the population structure consistently identified two genetically distinct groups, one in the Northeast and the other in the Central and West regions. The higher diversity of the diverged populations in Northeast Kalimantan indicates that the region may have hosted rainforest refugia during the ice age. Accordingly, analysis using DIY ABC software indicated that the Northeast and Central-West Kalimantan groups diverged 194,000 years ago. We conclude that global climate change during the Pleistocene strongly influenced the genetic diversity and structure of S. macrophylla populations in Kalimantan.     

Conservation genetics of the annual hemiparasitic plant <Emphasis Type="Italic">Melampyrum sylvaticum</Emphasis> (Orobanchaceae) in the UK and Scandinavia

Melampyrum sylvaticum is an endangered annual hemiparasitic plant that is found in only 19 small and isolated populations in the United Kingdom (UK). To evaluate the genetic consequences of this patchy distribution we compared levels of diversity, inbreeding and differentiation from ten populations from the UK with eight relatively large populations from Sweden and Norway where the species is more continuously distributed. We demonstrate that in both the UK and Scandinavia, the species is highly inbreeding (global F _IS = 0.899). Levels of population differentiation were high (F’_ST = 0.892) and significantly higher amongst UK populations (F’_ST = 0.949) than Scandinavian populations (F’_ST = 0.762; P < 0.01). The isolated populations in the UK have, on average, lower genetic diversity (allelic richness, proportion of loci that are polymorphic, gene diversity) than Scandinavian populations, and this diversity difference is associated with the smaller census size and population area of UK populations. From a conservation perspective, the naturally inbreeding nature of the species may buffer the species against immediate effects of inbreeding depression, but the markedly lower levels of genetic diversity in UK populations may represent a genetic constraint to evolutionary change. In addition, the high levels of population differentiation suggest that gene flow among populations will not be effective at replenishing lost variation. We thus recommend supporting in situ conservation management with ex situ populations and human-mediated seed dispersal among selected populations in the UK.     

Biodiversity potential of <Emphasis Type="Italic">Nothofagus</Emphasis> forests in Tierra del Fuego (Argentina): tool proposal for regional conservation planning

It is difficult to map and quantify biodiversity at landscape level in areas with low data availability, despite demand from decision-makers. We propose a methodology to determine potential biodiversity pattern using habitat suitability maps of the understory plant species with highest cover and occurrence frequency in the three different forests types of Tierra del Fuego (Argentina). We used a database of vascular plants from 535 surveys from which we identified 35 indicative species. We explored more than 50 potential explanatory variables to develop habitat suitability maps of the indicative species, which were combined to develop a map of the potential biodiversity. Correlation among environmental, topographic and forest landscape variables were discussed, as well as the marginality and the specialization of the indicative species. We detected differences in the niches of the species prevailing in the three forest types. The developed map of potential biodiversity uncovered hotspots of biodiversity in the ecotone of Nothofagus pumilio and N. antarctica as well as in the wettest part of the mixed N. pumilio–N. betuloides forests. It allowed thus to identify forest areas with different conservation potential and can be readily used as a decision support system for conservation and management strategies at different scales including the identification of land-use conflicts (e.g. of biodiversity with timber production and livestock) and the development of a network of protected areas, which currently does not cover the forests of highest conservation value.     

Xylem anatomy and calculated hydraulic conductance of four <Emphasis Type="Italic">Nothofagus</Emphasis> species with contrasting distribution in South-Central Chile

Nothofagus obliqua, N. dombeyi, N. alpina and N. antarctica are characteristic tree species of the temperate forests on the western slopes of the Andes with centres of distribution that differ in their temperature and moisture regimes. We tested branch wood from co-occurring specimens of these species for the inherent differences in xylem anatomy and theoretical hydraulic conductance to evaluate their resistance to drought or frost. The hydraulic conductivity of the xylem was calculated using a modified Hagen–Poiseuille equation and related to wood density. Conduit dimensions were used to predict the water potential that would cause 50 % loss of hydraulic conductivity (Ψ ₅₀). Nothofagus alpina, which mainly grows at sites with low frost frequency, exhibited the largest conduits and the highest mean values for conduit area, fraction of conduit area in the cross-section and hydraulic conductivity, but the lowest wood density. Opposite relationships were found in the plastic N. antarctica, whose xylem seems to be least vulnerable to freezing-induced, but also to drought-induced embolism. Calculated Ψ ₅₀ was highest (least negative) in N. alpina, indicating a relatively high susceptibility to cavitation. The xylem of the thermophilic N. obliqua and of N. dombeyi, which mainly occurs under oceanic climate, but can also survive at sporadically dry and warm sites, is not particularly adapted to periods of drought stress. Across all species, wood density was negatively correlated with the calculated hydraulic conductance. The xylem traits of N. alpina might contribute to its relatively high growth rate and facilitate its spread into forest gaps.     

A complex history of introgression and vicariance in a threatened montane skink (<Emphasis Type="Italic">Pseudemoia cryodroma</Emphasis>) across an Australian sky island system

Species endemic to sky island systems are isolated to mountain peaks and high elevation plateaux both geographically and ecologically, making them particularly vulnerable to the effects of climate change. Pressures associated with climate change have already been linked to local extinctions of montane species, emphasizing the importance of understanding the genetic diversity and population connectivity within sky islands systems for the conservation management of remaining populations. Our study focuses on the endangered alpine skink Pseudemoia cryodroma, which is endemic to the Victorian Alps in south-eastern Australia, and has a disjunct distribution in montane habitats above 1100 m a.s.l. Using mitochondrial DNA (mtDNA) and microsatellite loci, we investigated species delimitation, genetic connectivity and population genetic structure across the geographic range of this species. We found discordance between genetic markers, indicating historical mtDNA introgression at one of the study sites between P. cryodroma and the closely related, syntopic P. entrecasteauxii. Molecular diversity was positively associated with site elevation and extent of suitable habitat, with inbreeding detected in three of the five populations. These results demonstrate the complex interaction between geography and habitat in shaping the population structure and genetic diversity of P. cryodroma, and highlight the importance of minimising future habitat loss and fragmentation for the long-term persistence of this species.     

Genetic diversity and population structure of a drought-tolerant species of <Emphasis Type="Italic">Eucalyptus</Emphasis>, using microsatellite markers

Given the impact of climate change on the availability of water resources, it becomes necessary the use of plant species well suited to planting on dryland sites. Eucalyptus cladocalyx, a native tree of South Australia, is capable of growing under relatively dry environments and saline soils. Two hundred twenty simple sequence repeat (microsatellites) markers, from a consensus linkage map of Eucalyptus, were selected to examine genetic diversity and population structure in a collection of E. cladocalyx introduced to southern Atacama Desert, Chile. A total of 130 microsatellites were successfully amplified, some of which are associated with quantitative traits of interest in Eucalyptus. Genetic analysis revealed a total of 457 alleles, ranging from 2 to 8 alleles per locus. A moderate level of genetic diversity (He = 0.492) and differentiation (FST = 0.086) was found among the populations. Mount Remarkable and Marble Range showed the highest and lowest level of genetic diversity, respectively. The Bayesian clustering analysis revealed three homogeneous genetic groups confirming that the individuals of E. cladocalyx from natural forest are highly and significantly structured. These results provide a novel information for the development of breeding strategies in E. cladocalyx by using marker-assisted selection in regions with low rainfall patterns.     

Population genetic diversity and geographical differentiation of MHC class II DAB genes in the vulnerable Chinese egret (<Emphasis Type="Italic">Egretta eulophotes</Emphasis>)

Major histocompatibility complex (MHC) genes are excellent markers for the study of adaptive genetic variation occurring over different geographical scales. The Chinese egret (Egretta eulophotes) is a vulnerable ardeid species with an estimated global population of 2600–3400 individuals. In this study, we sampled 172 individuals of this egret (approximately 6 % of the global population) from five natural populations that span the entire distribution range of this species in China. We examined their population genetic diversity and geographical differentiation at three MHC class II DAB genes by identifying eight exon 2 alleles at Egeu-DAB1, eight at Egeu-DAB2 and four at Egeu-DAB3. Allelic distributions at each of these three Egeu-DAB loci varied substantially within the five populations, while levels of genetic diversity varied slightly among the populations. Analysis of molecular variance showed low but significant genetic differentiation among five populations at all three Egeu-DAB loci (haplotype-based ?_ST: 0.029, 0.020 and 0.042; and distance-based ?_ST: 0.036, 0.027 and 0.043, respectively; all P < 0.01). The Mantel test suggested that this significant population genetic differentiation was likely due to an isolation-by-distance pattern of MHC evolution. However, the phylogenetic analyses and the Bayesian clustering analysis based on the three Egeu-DAB loci indicated that there was little geographical structuring of the genetic differentiation among five populations. These results provide fundamental population information for the conservation genetics of the vulnerable Chinese egret.     

Genetic consequences of anthropogenic disturbances and population fragmentation in <Emphasis Type="Italic">Acacia senegal</Emphasis>

Acacia senegal is endemic to dry forest and woodland ecosystems of Sub-Saharan Africa and provides both ecological and socio-economic benefits. However, these ecosystems are threatened by escalating human disturbances and fragmentation. To investigate the human impacts on genetic diversity and structure of A. senegal, we studied genetic variability and differentiation of 330 individual trees from 11 natural A. senegal populations, grouped into lightly and heavily disturbed, using 12 polymorphic nuclear microsatellite markers. Gene diversity (H _E ) ranged from H _E = 0.570 to H _E = 0.632. Significant differences (P < 0.05) between the levels of disturbances are reported for mean gene diversity, number of alleles and allelic richness with lightly disturbed populations showing higher values. Overall, the indirect estimates of average outcrossing rates ranged from 0.794 (Kiserian) to 0.999 (Kampi ya Moto) with a mean of 0.997 suggesting a predominantly outcrossing species. There was no significant relationship (P > 0.05) detected between genetic and geographic distances, showing lack of isolation by distance. Analysis of population structure using unweighted pair group method with arithmetic mean and Bayesian model suggests presence of three gene pools as most probable, although most individuals showed mixed ancestry. The diversity and genetic structure reported in this study revealed negative impacts of human disturbance on A. senegal within this ecosystem. We recommend in-situ conservation strategies to safeguard the woodland ecosystem from further deforestation.     

Genetic diversity of the African poplar (<Emphasis Type="Italic">Populus ilicifolia</Emphasis>) populations in Kenya

We evaluated the genetic diversity of the African poplar (Populus ilicifolia) populations found in Kenya compared with reference samples of five poplar species from North America and one species introduced in Kenya from India (KEFRI-Kenya). Amplified fragment length polymorphism (AFLP) was used with the objective of providing important information for breeding and in situ/ex situ conservation of this species. Samples collected from three locations along the species’ natural range (Athi, Ewaso Nyiro, and Tana rivers) were compared with four samples of locally planted Populus deltoides stand introduced from India and ten reference samples from North America. Six AFLP primer combinations produced 521 clear bands for analysis. The percentage polymorphic loci were lowest in Tana (20.4 %) and highest in Athi (40.6 %). The average heterozygosity across the studied populations was between 0.07 and 0.3. AMOVA revealed more genetic variation partitioning within population (87 %; P?<?0.01) than among populations (13 %; P?<?0.01) suggesting significant genetic variation between populations. Further, UPGMA delineation showed two clusters of the Tana, Athi, and Ewaso Nyiro populations clustered together compared to the North America and India/KEFRI reference samples. Moreover, the study showed that the Athi population is more diverse than those of Tana and Ewaso Nyiro and may be important for conservation, domestication, and improvement studies. The genetic differentiation (F _ST ?=?0.134) among Kenyan P. ilicifolia populations suggests limited possibility of gene flow between these populations.     

Conservation genetics and geographic patterns of genetic variation of endangered shrub <Emphasis Type="Italic">Ammopiptanthus</Emphasis> (Fabaceae) in northwestern China

Phylogeographic patterns of Ammopiptanthus in northwestern China were examined with internal transcribed spacer (ITS) and three chloroplast intergenic spacers (trnH–psbA, trnL–trnF, and trnS–trnG). Two ITS genotypes (a–b) and 8 chloroplast haplotypes (A–H) were detected. Both ITS genotypes and chloroplast lineages were split in two geographic regions: western Xinjiang and the Alxa Desert. This lineage split was also supported by AMOVA analysis and the Mantel test. AMOVA showed that 89.81 % of variance in Ammopiptanthus occurred between the two geographic regions, and correlation between genetic distances and geographical distances was significant (r = 0.757, p < 0.0001). All populations in western Xinjiang shared haplotype A with high frequency, and range expansion was strongly supported by negative Fu’s F_S value, and mismatch distribution analysis, whereas populations in the Alxa Desert had higher genetic diversity and structure. We speculate that the cold and dry climate during the early Quaternary fragmented habitats of the species, limiting gene flow between regions, and interglacial periods most likely led to the range expansion in western Xinjiang. The low genetic diversity of Ammopiptanthus indicate a significant extinction risk, and protective measures should be taken immediately.     

Genetic assessment of <Emphasis Type="Italic">Abies koreana</Emphasis> (Pinaceae), the endangered Korean fir,and conservation implications

To establish a management plan for endangered and rare species, genetic assessment must first be conducted. The genetic characteristics of plant species are affected by demographic history, reproductive strategy, and distributional range as well as anthropological effects. Abies koreana E. H. Wilson (Pinaceae), Korean fir, is endemic to Korea and found only in sub-alpine areas of the southern Korean Peninsula and Jejudo Island. This species has been designated as critically endangered by the International Union for Conservation of Nature due to a continuous decline in its range and population fragmentation. We genotyped 176 individuals from seven natural populations and two afforested populations on the Korean Peninsula using 19 microsatellite loci. STRUCTURE analysis revealed two genetic clusters in natural populations (F _st  = 0.040 and R _st  = 0.040) despite low differentiation. We did not detect a significant reduction in genetic diversity or the signature of a genetic bottleneck despite population fragmentation and small population size. We deduced that this species exhibits a metapopulation structure, with the population on Jirisan Mountain acting as a source of genetic diversity for other local small populations on the Korean Peninsula, through contemporary asymmetric gene flow. However, the majority of afforested individuals on the Korean Peninsula originated from a different gene cluster. Thus, we recommend a conservation strategy that maintains two genetically unique clusters.     

Elucidating the multiple genetic lineages and population genetic structure of the brooding coral <Emphasis Type="Italic">Seriatopora</Emphasis> (Scleractinia: Pocilloporidae) in the Ryukyu Archipelago

The elucidation of species diversity and connectivity is essential for conserving coral reef communities and for understanding the characteristics of coral populations. To assess the species diversity, intraspecific genetic diversity, and genetic differentiation among populations of the brooding coral Seriatopora spp., we conducted phylogenetic and population genetic analyses using a mitochondrial DNA control region and microsatellites at ten sites in the Ryukyu Archipelago, Japan. At least three genetic lineages of Seriatopora (Seriatopora-A, -B, and -C) were detected in our specimens. We collected colonies morphologically similar to Seriatopora hystrix, but these may have included multiple, genetically distinct species. Although sexual reproduction maintains the populations of all the genetic lineages, Seriatopora-A and Seriatopora-C had lower genetic diversity than Seriatopora-B. We detected significant genetic differentiation in Seriatopora-B among the three populations as follows: pairwise F _ST = 0.064–0.116 (all P = 0.001), pairwise G′′_ST = 0.107–0.209 (all P = 0.001). Additionally, only one migrant from an unsampled population was genetically identified within Seriatopora-B. Because the peak of the settlement of Seriatopora larvae is within 1 d and almost all larvae are settled within 5 d of spawning, our observations may be related to low dispersal ability. Populations of Seriatopora in the Ryukyu Archipelago will probably not recover unless there is substantial new recruitment from distant populations.     

Genetic structure and diversity in relation to the recently reduced population size of the rare conifer, <Emphasis Type="Italic">Pseudotsuga japonica</Emphasis>, endemic to Japan

Rare species consisting of small populations are subject to random genetic drift, which reduces genetic diversity. Thus, determining the relationship between population size and genetic diversity would provide key information for planning a conservation strategy for rare species. We used six microsatellite markers to investigate seven extant populations of the rare conifer Pseudotsuga japonica, which is endemic to the Kii Peninsula and Shikoku Island regions that are geographically separated by the Kii Channel in southwest Japan. The population differentiation of P. japonica was relatively high (F_ST = 0.101) for a coniferous species, suggesting limited gene flow among populations. As expected, significant regional differentiation (AMOVA; p?<?0.05) indicated genetic divergence across the Kii Channel. A strong positive correlation between census population size and the number of rare alleles (r?=?0.862, p?<?0.05) was found, but correlations with major indices of genetic diversity were not significant (allelic richness: r?=?0.649, p?=?0.104, expected heterozygosity: r?=?0.361, p?=?0.426). The observed order of magnitude of correlation with three genetic diversity indices corresponded with the theoretically expected order of each index’ sensitivity (i.e., the rate of decline per generation) to the bottleneck event. Thus, features that exhibit a faster response, i.e., the number of rare alleles, would have been subject to deleterious effects of the recent decline in population size, which is presumably caused by the development of extensive artificial plantations of other tree species over the last several decades. Finally, we propose a conservation plan for P. japonica based on our findings.     

High genetic diversity in an endangered medicinal plant, <Emphasis Type="Italic">Saussurea involucrata</Emphasis> (<Emphasis Type="Italic">Saussurea</Emphasis>, Asteraceae), in western Tianshan Mountains,China

Saussurea involucrata (Asteraceae) is a medicinal and second-degree national priority endangered plant that is mainly distributed in the high latitude region of the western Tianshan Mountains. The population is fragmented and isolated, and extensive human impact merits a suitable and specific conservation strategy, which can be compiled based on the genetic diversity, population structure, and demographic history. Phylogeographic studies were conducted on a total of five natural populations and 150 individuals were sampled. Data from three cpDNA intergenic spacer regions (trnL-F, matK, and ndhF-rpl32) and nrDNA ITS sequences showed that twelve haplotypes in cpDNA and five haplotypes in nrDNA indicated high genetic diversity among populations sampled (H _T?=?0.820 and 0.756) and within populations sampled (H _S?=?0.792 and 0.721). Additionally, the high genetic diversity did not mirror genetic structure in either cpDNA (F _ST?=?0.03153, G _ST?>?N _ST, p?<?0.05) or nrDNA (F _ST?=?0.03666, meaningless G _ST and N _ST). Two groups (north and south) were determined for a SAMOVA analysis. Based on this analysis, the demographic history was conducted with a Bayesian Skyline Plot and Isolation with Migration analysis, which showed sustainable and stable extension without a marked bottleneck. Divergence time was indicated at c. 6.25 Mya (90%HPD: 15.30–0.22 Mya) in the Miocene, which is consistent with the formation of the Kelasu section of Tianshan. The southern populations in the Bayanbulak and Gonglu regions require additional attention and transplanting would be an effective way to restore rare cpDNA haplotypes, increase effective population size, and migration rate. Our results suggested that in situ conservation of S. involucrata in western Tianshan should be the main strategy for protection and recovery of the species.     

Population isolation results in unexpectedly high differentiation in Carolina hemlock (<Emphasis Type="Italic">Tsuga caroliniana</Emphasis>), an imperiled southern Appalachian endemic conifer

Carolina hemlock (Tsuga caroliniana Engelm.) is a rare conifer species that exists in small, isolated populations within a limited area of the Southern Appalachian Mountains of the USA. As such, it represents an opportunity to assess whether population size and isolation can affect the genetic diversity and differentiation of a species capable of long-distance gene flow via wind-dispersed pollen and seed. This information is particularly important in a gene conservation context, given that Carolina hemlock is experiencing mortality throughout its range as a result of infestation by hemlock wooly adelgid (Adelges tsugae Annand), an exotic insect. In this study, 439 Carolina hemlock trees from 29 areas (analyzed as populations) were sampled, representing an extensive range-wide sampling of the species. Data from 12 polymorphic nuclear microsatellite loci were collected and analyzed for these samples. The results show that populations of Carolina hemlock are extremely inbred (F _IS  = 0.713) and surprisingly highly differentiated from each other (F _ST  = 0.473) with little gene flow (N_m = 0.740). Additionally, most populations contained at least one unique allele. This level of differentiation is unprecedented for a North American conifer species. Numerous genetic clusters were inferred using two different clustering approaches. The results clearly demonstrate that, existing as a limited number of small and isolated populations, Carolina hemlock has insufficient gene flow to avoid widespread genetic drift and inbreeding, despite having the capacity to disperse pollen and seed relatively long distances by wind. These results have important conservation implications for this imperiled species.