Genetic diversity and structure of the endemic Caesalpinia hintonii complex (Leguminosae: Caesalpinioideae) in Mexico

The Caesalpinia hintonii complex is formed by five endemic species (C. hintonii, C. laxa, C. macvaughii, C. melanadenia and C. epifanioi) occurring in central Mexico. This species complex is under incipient genetic divergence as by-product of local adaptations in reproductive and morphological traits to different habitats. We estimate the genetic variation and structure of populations of this species complex to assess the extent of genetic differentiation among populations and related species along its geographic distribution. Estimations of genetic diversity and structure were done based on ten enzymes and 18 loci. Mean number of alleles per locus ranged from 1.5 to 1.9. Polymorphic loci ranged from 42.1 to 68.4. Observed (H_o: range 0.191–0.275) and expected (H_e: range 0.205–0.317) heterozygosities in this complex were higher compared with other endemic and legume species. Neis genetic diversity estimates showed that most genetic variation was found within (H_S = 0.325) rather than among populations (D_ST = 0.085). Populations of the species C. hintonii showed a considerable genetic differentiation (F_ST = 0.207). The results of genetic diversity and structure within and among populations are in accord with the great morphological differentiation described for this species complex.     

Genetic structure of the critically endangered endemic Cochlearia polonica (Brassicaceae): efficiency of the last-chance transplantation

Cochlearia polonica , a narrow endemic of southern Poland, is one of the rarest and most endangered species of the European flora. All natural populations are extinct and the species has survived in only one transplanted population derived from 14 original individuals. Using AFLPs, the genetic variation and spatial structure of this population were analysed approximately 30 years after transplantation. The incidence of polymorphic AFLP bands (30.46%) is low compared with data from a natural population of another Cochlearia species, C. tatrae . Principal co-ordinates and spatial autocorrelation analyses demonstrated the presence of significant genetic structure. It is recommended that conservation efforts on C. polonica should preserve the complete population area, because local extinctions may lead to a loss of genetic information. The presence of genetic structure should also be taken into account during the sampling of material (plants or seeds) for ex situ conservation measures.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 527–532.     

Microhabitat Types Promote the Genetic Structure of a Micro-Endemic and Critically Endangered Mole Salamander (Ambystoma leorae) of Central Mexico

The reduced immigration and emigration rates resulting from the lack of landscape connectivity of patches and the hospitality of the intervening matrix could favor the loss of alleles through genetic drift and an increased chance of inbreeding. In order for isolated populations to maintain sufficient levels of genetic diversity and adapt to environmental changes, one important conservation goal must be to preserve or reestablish connectivity among patches in a fragmented landscape. We studied the last known population of Ambystoma leorae, an endemic and critically threatened species. The aims of this study were: (1) to assess the demographic parameters of A. leorae and to distinguish and characterize the microhabitats in the river, (2) to determine the number of existing genetic groups or demes of A. leorae and to describe possible relationships between microhabitats types and demes, (3) to determine gene flow between demes, and (4) to search for geographic locations of genetic discontinuities that limit gene flow between demes. We found three types of microhabitats and three genetically differentiated subpopulations with a significant level of genetic structure. In addition, we found slight genetic barriers. Our results suggest that mole salamander’s species are very sensitive to microhabitat features and relatively narrow obstacles in their path. The estimates of bidirectional gene flow are consistent with the pattern of a stepping stone model between demes, where migration occurs between adjacent demes, but there is low gene flow between distant demes. We can also conclude that there is a positive correlation between microhabitats and genetic structure in this population.     

Growth and the expression of alternative life cycles in the salamander Ambystoma talpoideum (Caudata: Ambystomatidae)

Complex life cycles (CLCs) contain larval and adult phases that are morphologically and ecologically distinct. Simple life cycles (SLCs) have evolved from CLCs repeatedly in a wide variety of lineages but the processes that may underlie the transition have rarely been identified or investigated experimentally. We examined the influence of larval growth rate on the facultative expression of alternative life cycles (metamorphosis or maturation as gill-bearing adults [= paedomorphosis]) in the salamander Ambystoma talpoideum. We manipulated growth rates by altering the amount of food individuals received throughout larval development. The expression of alternative life cycles in A. talpoideum is influenced by growth via food levels, but the same growth rates at different points in the larval period elicit different responses. Individuals were more likely to metamorphose (i.e. express a CLC) when food levels and growth rates were high later in development and more likely to mature without metamorphosing (SLC) when growth rates were comparatively low during the same point in development. Growth rates at particular points in development, rather than overall larval growth rate, may be an important proximate factor in salamander life-cycle evolution.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 639–646.     

Genetic covariance structure of growth in the salamander Ambystoma macrodactylum

The size of an organism at any point during ontogeny often has fitness consequences through either direct selection on size or through selection on size-related morphological, performance, or life history traits. However, the evolutionary response to selection on size across ontogeny (a growth trajectory) may be limited by genetic correlations across ages. Here we characterize the phenotypic and genetic covariance structure of length and mass growth trajectories in a natural population of larval Ambystoma macrodactylum using function-valued quantitative genetic analyses and principal component decomposition. Most of the phenotypic and genetic variation in both growth trajectories appears to be confined to a single principal component describing a pattern of positive covariation among sizes across all ages. Higher order principal components with no significant associated genetic variation were identified for both trajectories, suggesting that evolution towards certain patterns of negative covariation between sizes across ages is constrained. The well-characterized positive relationship between size at metamorphosis and fitness in pond-breeding amphibians predicts that the across-age covariance structure will strongly limit evolution only if there is negative selection on size prior to metamorphosis. The pattern of genetic covariation observed in this study is similar to that observed in other vertebrate taxa, indicating that size may often be highly genetically and phenotypically integrated across ontogeny. Additionally, we find that phenotypic and genetic analyses of growth trajectories can yield qualitatively similar patterns of covariance structure.     

Infracommunity of parasite helminths of Ambystoma lernaensis (Caudata: Ambystomatidae) in Lerma,Mexico

The helminth infracommunity structure was analyzed in 48 salamanders (Ambystoma lermaensis) from San Pedro Tlaltizapán, Lerma, Estado de Mexico (June 1997 to March 1999). Richness (2.46 +/- 1.8), abundance (29.5 +/- 42.3), and diversity (0.64 +/- 0.58) levels characterize these communities as depauperate, similar to other amphibian helminth communities worldwide. Apparently, the main forces determining infracommunity structure are ectothermy (as regulator of the ingestion rate), and the opportunistic feeding habits of the hosts, because 80% of the helminth taxa enter the host by ingestion of intermediate hosts.     

Floristic diversity of sabal palmetto woodland: an endemic and endangered vegetation type from Mexico

The sabal palmetto woodland is a tropical plant formation dominated by Sabal mexicana, with restricted distribution to southeast Mexico. Sabal palms grow on poor soils but accumulate large quantities of organic substrate in their crowns, harboring a contingent of plants that use it as phorophyte. Although it is a threatened formation, basic information on its biodiversity is scant. We examined the floristic diversity of recruited (diameter at breast height, DBH, ≥1 cm) and understory (DBH ≤ 1 cm) plants, and its variation with anthropogenic disturbance. We also examined the floristic diversity of plants that use the sabal palms as phorophytes, and assessed its variation with human impact. All plants present in transects within a conserved and an adjacent perturbed area were sampled. The list of observed taxa shows that this vegetation has a clear affinity with tropical dry and wet forests of Mexico, with a small representation of taxa from desert ecosystems. The floristic contingent included a total of 81 species in 2000 m². Richness, composition and diversity were affected by disturbance. Recruited and understory vegetation in the disturbed site were 5- and 1.6-times less diverse than in the conserved site, and species of mature, conserved vegetation were substituted by heliophytes in the disturbed site. In contrast, abundance of palms and diversity and identity of epiphytic/hemiepiphytic plants were not affected by disturbance. We show that even monodominated tropical ecosystems growing on poor soils have a high floristic diversity and that current anthropogenic impact threatens not only species and populations but also entire plant formations.     

镇海棘螈的精子结构

应用透射电镜和扫描电镜对镇海棘螈Echinotritonchinhaiensis精子的超微结构进行了研究。结果表明 :镇海棘螈的精子具有蝾螈科精子的一些共同特征 ,如精子头部较长、前端有顶体钩、细胞核周围有核脊、尾部轴丝旁有边缘丝 ,但也具有其自身的形态结构特点 ,如精子颈部的长度、核脊的形状和大小等与有尾两栖类物种的精子存在明显差别。镇海棘螈精子发达的颈部和丰富的核脊具类群特异性     

Genetic diversity of two endemic and endangered Plantago species

Plantago algarbiensis and Plantago almogravensis are two endangered and endemic species from Portugal. Due to the rarity and endangered nature of these species as well as the lack of molecular data, their genetic variation was evaluated using ISSR and RAPD markers. P. algarbiensis species showed higher genetic variability (73.9% of polymorphism) than P. almogravensis (61.2%). The two species revealed a high level of genetic diversity, with a Nei's genetic diversity of 0.1965 and 0.2309 and a Shannon's diversity index of 0.2975 and 0.3520, for P. almogravensis and P. algarbiensis, respectively. A low level of genetic differentiation was observed (Gst = 0.1873) among the species. However, the cluster and PCA analyses, based on genetic similarity, revealed two main, clearly separate clusters, which directly corresponded to the plants isolated from each species. In situ and ex situ measures should be applied in order to preserve both species but, based on these results, P. almogravensis population should be a priority for conservation.     

Genetic diversity and population structure of endangered endemic Paeonia jishanensis in China and conservation implications

Paeonia jishanensis, one of the most important ancestral species of cultivated tree peonies, is an endangered ornamental and medicinal plant endemic to China. A total of 236 individuals of P. jishanensis from 10 extant populations were analysed using 21 EST-SSR markers to assess their genetic diversity and population structure. Moderate genetic diversity levels (H_E = 0.340) and high genetic differentiation among populations (F_ST = 0.335) were revealed. Combining the results of STRUCTURE, PCoA and neighbour-joining analyses, the 10 populations were divided into four genetic groups that were significantly related to their geographical origins, which was further supported by hierarchical AMOVA showing the highest variation of 17.9% among groups. The Mantel test showed a significant positive correlation between genetic distance and geographic distance among populations (r = 0.873, P < 0.0001). The genetic structure of P. jishanensis may be due to limited gene flow hindered by vicariance and its breeding system: facultative vegetative reproduction. This study carries significant implications for the conservation and utilization of this endangered species.     

Genetic diversity and differentiation in the critically endangered orchid (Amitostigma hemipilioides): implications for conservation

Amitostigma hemipilioides is an endangered terrestrial orchid endemic to China. In the Southwestern China, the species is found restricted growing in the karst limestone or rock in the edge of farmland, moist hillsides or river. In the present study, the genetic diversity and differentiation was estimated within and among habitats, populations and groups of this species by ISSR markers. Using 13 polymorphic primers, an intermediate level of genetic diversity was found at the species level and population level with the percentage of polymorphic bands (P) of 64.7 and 50.9 %, Shannon index of diversity (I) of 0.3873 and 0.2949, respectively. The analysis of molecular variance (AMOVA) showed that the high level of population differentiation was presented with 45.63 % relative to the total genetic variation residing among eight populations. It was noteworthy that as much as 69.17 % of the total diversity was most likely attributed to the difference among the populations in fragmentation habitat conditions, while 16.32 % of the total diversity could be attributed to the difference among the populations in stable and favorable habitat conditions. The in situ conservation is a top strategy, thus the mycorrhizal fungi and pollinators are protected by protecting habitat and avoiding fragmentation which is helpful to the cycle of this endangered orchid species and recovery of its wild populations. In addition, to maintaining the germplasm bank of this species, the ex situ conservation by habitat simulation and reintroduction has been considered in the living collection at Kaili University ecological garden and Yuntai Mountain scenic spot using the plants collected in this study.     

Genetic diversity of the endangered endemic Agave victoriae-reginae (Agavaceae) in the Chihuahuan Desert

Long-lived perennials are a species-rich, ecologically important component of the North American deserts, yet we know little about their genetic structure, information important for their conservation. Agave victoriae-reginae is an endemic of the Chihuahuan Desert of northern Mexico that is endangered by collection for the ornamental trade. We examined levels and patterns of variation at ten polymorphic allozyme loci in ten populations representing the range of the species. Levels of genetic variation (mean H_e= 0.335) and differentiation (mean F_ST = 0.236) were high. Phenetic clustering suggested the existence of at least three distinct groups of populations. If this pattern of variation is representative of other long-lived desert perennials, it may explain the species richness of this group and will pose a real challenge to gene conservation efforts.     

Genetic diversity and population structure of Nuphar submersa (Nymphaeaceae), a critically endangered aquatic plant endemic to Japan,and implications for its conservation

Journal of Plant Research - Nuphar submersa (Nymphaeaceae) is a critically endangered freshwater macrophyte indigenous to central Japan, with only four small extant populations represented across...     

Genetic diversity of Narcissus tortifolius,an endangered endemic species from Southeastern Spain

In this work, we analyzed inter-simple sequence repeat markers from 10 populations (298 individuals) spanning the whole distribution range of the endemic Narcissus tortifolius. We assessed genetic variation levels and distribution by estimates of genetic diversity, analysis of molecular variance (AMOVA), principal coordinates and Bayesian methods. N. tortifolius showed moderate genetic diversity at intrapopulation level and low genetic differentiation of populations. In general, Almerian populations showed slightly higher levels of genetic diversity than Murcian populations. Our results indicate that habitat fragmentation has not caused genetic depauperation in N. tortifolius but did reveal moderate genetic differentiation. Indeed, principal coordinate analysis and Mantel test revealed a slight tendency to separate populations into two groups (Murcian vs. Almerian). A recent isolation event of populations, together with the perennial nature of this species could be the main reasons for this low to moderate differentiation. Our findings could be used to establish management guidelines for the conservation of this rare species.     

Genetic structure and diversity of Coscinium fenestratum: a critically endangered liana of Western Ghats,India

Coscinium fenestratum is a critically endangered medicinal plant, well-known for its bioactive isoquinoline alkaloid berberine. The species has been over harvested from its natural habitats to meet the huge requirement of raw drug market and industrial consumption. This has lead to a rapid decline in the population size and has also led to local population extinction at few locations in the Western Ghats, India. In this study, inter-simple sequence repeat markers were used to investigate the genetic variation and population structure of seven extant populations of C. fenestratum from the central Western Ghats, India. Eight primer combination produced a total of 57 unambiguous bands, of which (47.1 %) were polymorphic. The species exhibited a moderate to low level of intra population genetic diversity (H _s = 0.347 ± 0.008; H _t = 0.378 ± 0.006 (POPGENE) and H _s = 0.262 ± 0.0028; H _t = 0.204 ± 0.020 (HICKORY)). The populations were low to moderately differentiated from one another (G _ST = 0.221) and geographical distance was not significantly correlated with genetic distance, suggesting that these long-lived, geographically distant remnant populations were once connected through gene flow. There was a significant amount of genetic variation among populations (19.85 %). The Bayesian software STRUCTURE and HICKORY were used to further reveal the genetic structure of C. fenestratum. The results revealed weak population structure (K = 2) with one single widespread gene pool, and indicated that gene flow and inbreeding are likely to be the major driving force in shaping current population genetic structure of C. fenestratum. Thus, an understanding of the genetic diversity and population structure of C. fenestratum can provide insight into the conservation and management of this species.     

Genetic diversity and structure of Atta robusta (Hymenoptera,Formicidae, Attini), an endangered species endemic to the restinga ecoregion

The genetic diversity and structure of the ant Atta robusta were assessed by ISSR (inter-simple sequence repeats) in 72 colonies collected from 10 localities in the Brazilian states of Espírito Santo (48 colonies) and Rio de Janeiro (24 colonies). The ISSR pattern included 67 bands, 51 of them (76.1%) polymorphic. Analysis of molecular variance (AMOVA) revealed a high level (57.4%) of inter-population variation, which suggested a high degree of genetic structure that was confirmed by UPGMA (unweighted pair-group method using an arithmetic average) cluster analysis. The significant correlation between genetic and geographic distances (r = 0.64, p < 0.05) indicated isolation that reflected the distance between locations. Overall, the populations were found to be genetically divergent. This finding indicates the need for management plans to preserve and reduce the risk of extinction of A. robusta.     

Genetic diversity and conservation evaluation of a critically endangered endemic maple,Acer yangbiense,analyzed using microsatellite markers

The newly discovered endemic maple Acer yangbiense of China has only five individuals left in the wild, and thus has been classified as a plant species with extremely small populations (PSESP). PSESP species call for emergency protection procedures, such as ex-situ conservation and reintroduction. Our objectives were to examine the genetic diversity of A. yangbiense and to evaluate former conservation strategies from a genetic point of view. Our results suggested that A. yangbiense was not genetically depauperate, but its genetic loss at a species level was obvious. A parentage analysis indicated a high selfing-rate in A. yangbiense and suggested the existence of a previously unknown wild individual. Former conservation strategies did not include all genetic variations of the wild population, and gene diversity of the ex-situ conserved seedlings is lower than that of the wild population. From our findings, we make suggestions to guide the subsequent protection of this species.