Low genetic diversity of a high mountain burnet moth species in the Pyrenees

The burnet moth Zygaena anthyllidis, endemic to the high elevations of the Pyrenees, is vulnerable to land-use. In order to identify conservation priorities based on an assessment of genetic diversity within populations and gene flow among populations, we examined Z. anthyllidis’ genetic variability and differentiation based on allozyme electrophoresis from seven populations scattered across its entire range. In comparison to other mountain Lepidoptera, the populations studied exhibit a low level of genetic diversity. Remarkable between-population differentiation (F _ST = 0.053), the presence of private alleles, and the lack of significant isolation-by-distance pattern characterises the genetic make-up of the species. We interpreted the pattern of genetic differentiation as a consequence of low dispersal power in combination with insufficient landscape connectivity. Ongoing land-use change might reinforce genetic differentiation due to habitat fragmentation and additionally affect negatively allozyme variability at shifting range margins, i.e. the capacity to adapt to changing environments. We therefore suggest creating a network of suitable habitats at the landscape scale to facilitate genetic exchange and to conserve the species’ overall genetic variability.     

Low genetic diversity and high genetic divergence caused by inbreeding and geographical isolation in the populations of endangered species Loropetalum subcordatum (Hamamelidaceae) endemic to China

Loropetalum subcordatum (Hamamelidaceae) is one of the most endangered angiosperm species in China. It is narrowly distributed in a few localities in the evergreen broadleaved forest of southern China. Up to now only a few dozen remnant individuals have been found in the four extant populations. In this project, we studied its genetic diversity and population genetic structure using the high resolution molecular marker of amplified fragment length polymorphism. In total, 47 individuals from all the four populations (including all individuals in three populations) were analyzed. Comparably low genetic diversity within populations was revealed and significantly high genetic differentiation among the populations was detected. Four independent groups were identified which corresponded with their geographical ranges. Autogamy is considered to be the major factor contributing to the low genetic variation and high genetic divergence within this species. In addition, small population size, restricted distribution range, geographical isolation and limited seed dispersal may also contribute to the low genetic diversity and high population genetic differentiation. Clonal reproduction was inferred to occur in the two island populations. Suggestions for conservation strategies are provided to preserve the genetic resources of this species.     

Genetic diversity and floral dimorphism in Limonium dendroides (Plumbaginaceae), a woody Canarian species on the way of extinction

We combined reproductive and allozyme data to assess the levels and structuring of genetic variation and propose conservation guidelines in Limonium dendroides, a critically endangered Canarian endemic Plumbaginaceae featuring the floral and pollen pap/cob dimorphisms associated with the heteromorphic diallelic self-incompatibility system described for this family. Although seed germination has been reported in greenhouse conditions, the detection of individuals of only one morph in all wild subpopulations surveyed explains the extremely limited seed production and recruitment in nature. The geographical proximity and genetic closeness between some subpopulations, together with absence of inbreeding depression symptoms, and a higher allozyme variation in the cultured or reintroduced offspring than in their parental wild subpopulations indicate the viability of occasional compatible matings, thereby suggesting that even low levels of gene flow could mitigate the deleterious effects of fragmentation on subpopulation survival. However, our overall results indicate that L. dendroides is in a critical conservation situation where the utter scarcity of compatible mates within the subpopulations, radically low subpopulation sizes, poor inter-subpopulation gene flow, impoverished genetic variation, herbivore grazing, and the extreme habitat topography have overridden the reproductive capabilities of the species. According to our results, once morph types in all wild and cultured specimens can be determined, inducing fertile crosses through mixed reinforcements is advisable only in the most extremely isolated and small subpopulations (Argaga and Guarimiar) using individuals from the nearest ones (Azadoe and Palmarejo), whilst non-mixed reinforcements seem viable in the remaining subpopulations. Only when the subpopulations attain higher seed production and recruitment rates will it be adequate to collect seeds for their storage at a germplasm bank facility.     

Local extinction event despite high levels of gene flow and genetic diversity in the federally-endangered Miami blue butterfly

A certain level of genetic diversity and connectivity between populations is necessary to allow small populations to persist over time. In this study, we investigate the last two populations of the highly endangered Miami blue butterfly, one of which was extirpated in 2010. We investigate whether an erosion of genetic diversity was the cause for the extirpation of the Bahia Honda State Park (BHSP) population. As the level of existing molecular diversity within and gene flow between the last two populations of the endangered Miami blue butterfly was unknown, we present data from twelve polymorphic microsatellite loci as an assessment. We show that greater genetic diversity (allelic richness and observed heterozygosity) than originally predicted existed in the BHSP population prior to its extirpation and values were even greater in the Key West National Wildlife Refuge population. Allelic frequencies show short-range gene flow between neighboring habitat patches and underline the importance of habitat connectivity. It does not appear that loss of genetic diversity was the cause for the loss of the BHSP population. Greater consideration of habitat connectivity should be considered for short and long-term conservation and management of this taxon.     

Effects of inbreeding on the genetic diversity of populations

The study of variability within species is important to all biologists who use genetic markers. Since the discovery of molecular variability among normal individuals, data have been collected from a wide range of organisms, and it is important to understand the major factors affecting diversity levels and patterns. Comparisons of inbreeding and outcrossing populations can contribute to this understanding, and therefore studying plant populations is important, because related species often have different breeding systems. DNA sequence data are now starting to become available from suitable plant and animal populations, to measure and compare variability levels and test predictions.     

Back from the brink: Gladiolus halophila (Iridaceae: Crocoideae), a remarkable new species from southern Namibia escapes imminent extinction

The new species Gladiolus halophila Goldblatt & J.C.Manning from near Keetmanshoop in southern Namibia is described and illustrated. It is closely allied to G. longicollis and G. tristis from southwestern and eastern South Africa but is distinguished by its lilac flowers with shorter perianth tube, 35–40 mm long. The flowers last just one day and are self-compatible. The species, which is restricted to saline seepages, is known from just two populations, one of which is due to be inundated by a planned dam, and it is therefore classified as Endangered. The action of the Namibian Government in commissioning a search for additional localities serves as a valuable example in similar instances.     

Plant species diversity and ecological districts of the Sinai desert

Summary Lists of vascular plant species for each of the 12 ecological districts of Sinai were prepared. In all 78,000 observations on altogether 812 species were analyzed. The number of districts where each species occurred was also counted. Linear regressions were calculated for the log-transformed values of species/area, species/altitude and multiple regression of species on both area and altitude.The regression of species on area for the 12 ecological districts of Sinai gave the equation: log S = 1.0309+0.3 log A The value of z=0.3 is higher than 0.222—the measured overall value for the continents and higher than the values for the Sahara, California mainland, the British Isles, and the Netherlands. However, it is lower than the values for the Galápagos Archipelago and the California Islands.The number of species supported in districts characterized by fissured limestone, gravel plains, chalk, marl, sandstones, sands or fissured magmatic and metamorphic rocks is close to the regression of species on area, whereas large outcrops of smooth-faced rocks are relatively richer in total number of species as well as in stenotople species.It is suggested that the high gamma diversity of Sinai as compared with other parts of the world is primarily due to its environmental heterogeneity. Sinai being a meeting place of three phytogeographical regions and to past climatic changes. The effect of smooth-faced rock outcrops as conducive to providing refugia must also be taken into account.This work is based on a comprehensive study of the vegetation of Sinai directed by Prof. G. Orshan, with the collaboration of Dr. A. Shmida, the present author and the late Prof. N.H. Tadmor and Dr. G. Halevy.     

High levels of genetic diversity in populations of Iris aphylla L. (Iridaceae), an endangered species in Poland

We used RAPDs (Random Amplified Polymorphic DNAs) to investigate genetic diversity and its partition within and between three populations of Iris aphylla in Poland. Analysis of Molecular Variance (AMOVA) of 84 distinct RAPD multiband genotypes revealed higher variation within populations (77.2%) than genetic differentiation between them (22.8%, P  < 0.002). Values of genetic diversity indices ( H ) were similar in all three sites (0.21–0.24). The differentiation of the populations corresponded to low average gene flow ( Nm  = 0.81). Our results indicated that genetic diversity was independent of population size. We concluded that although sexual reproduction and gene flow between populations of I. aphylla were very limited, they preserved high levels of genetic diversity. Relatively large number of seeds, which migrated in the past to populations, as well as patterns of reproduction and life history of I. aphylla may explain this situation.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 65–72.     

Low diversity,little genetic structure but no inbreeding in a high-density island endemic pit-viper Gloydius shedaoensis

Island species and their ecosystems play an important role in global biodiversity preservation, and many vulnerable island species are conservation priorities. Although insular habitat likely facilitates the species diversification process, it may also aggravate the fragility of these species with high risk of inbreeding. The Shedao pit-viper Gloydius shedaoensis is an island endemic species with an extremely high population density, which has been categorized as vulnerable in the IUCN (International Union for the Conservation of Nature and Natural Resources) Red List. We collected 13,148 SNP (Single Nucleotide Polymorphism) from across its genome and examined its genetic diversity and demographic history. The Shedao pit-viper has a low genetic diversity but shows no sign of inbreeding. Furthermore, population genetic structure analysis, including the neighbor-joining tree, principal coordinate analysis, clustering, and spatial autocorrelation, revealed a general lack of spatial structure. Only the isolation by distance residues suggested a weak patchiness. Overall, the population is nearly panmictic and gene flow is evenly distributed across the island. A large number of individuals, small size of the island, and the lack of population structure likely all contribute to the lack of inbreeding in this species. We also detected signs of male-biased dispersal, which likely is another inbreeding avoidance strategy. Historical demographic analysis suggested that the historical population size and distribution of the species are much larger than their current ones. The multiple transgressive–regressive events since the Late Pleistocene are likely the main cause of the population size changes. Taken together, our results provide a basic scientific foundation for the conservation of this interesting and important species.     

Low genetic diversity as revealed by SPAR methods possibly leads to extinction of two critically-endangered and endemic species of Mantisia

Mantisia spathulata Schult. and M. wengeri Fischer, two critically-endangered, endemic and rare species of the genus Mantisia (Zingiberaceae), have been rediscovered from Lunglei province of Mizoram, India, after two decades. For sustainable conservation and utilization of the Mantisia species, in vitro seed and clonal propagation methods have been developed earlier by our research group and plantlets have been reintroduced to their natural habitat for species recovery. To comprehend the plausible reasons for endemism and endangeredness of both the species at DNA level, they were analyzed to assess natural genetic variation using three different polymerase chain reaction (PCR) based DNA markers viz. random amplified polymorphic DNA (RAPD), inter simple sequence repeat (ISSR) and directed amplification of minisatellite DNA regions (DAMD), both individually and cumulatively, which are popularly regarded as single primer amplification reaction (SPAR) methods. A total of 107 primers belonging to three SPARs are used which collectively endow low genetic variation (15 and 20 %, respectively) in both M. spathulata and M. wengeri. The use and efficacy of SPAR methods to reveal the natural genetic variation in Mantisia species at intra-specific level has been recorded for the first time. To impede the extinction risk of these two species of genus Mantisia, large scale conservation strategies including in situ and ex situ conservation are recommended.     

Low genetic diversity but local genetic differentiation in endemic Minasia (Asteraceae) species from Brazil

Espinhaço Range is a Brazilian chain of mountains, extremely rich in endemic species. Minasia has six species, all perennial herbs endemic to this range. Twenty-two populations were sampled from all Minasia species and assayed for allozyme variation. The species showed low genetic variation, compatible with the expectation for endemics. Genetic identities in Serra do Cipó and Diamantina were high, even between populations of different species. On the other hand M. cabralensis, from Serra do Cabral, was more differentiated from the other species. We also observed a marked genetic differentiation within M. cabralensis. Most strikingly, two close populations of this species showed very different allele frequencies. Our findings highlight the importance of local differentiation in campos rupestres. The observed genetic structure indicates that substantial portions of genetic diversity could be lost with the extinction of only one population, which is especially threatening considering the already low genetic diversity.     

Low levels of genetic variation inPhenakospermum guyannense (Strelitziaceae), a widespread bat-pollinated Amazonian herb

Phenakospermum guyannense is a monotypic, arborescent, long-lived monocot that is widespread in Amazonian South America. This outcrossing species is pollinated primarily by phyllostomid bats. Given these life-history characteristics,P. guyannense is expected to exhibit high levels of genetic variation and gene flow. We used isozyme electrophoresis and randomly amplified polymorphic DNA (RAPD) to characterize genetic variation in populations ofP. guyannense from French Guiana. Both measures detected a surprisingly low level of genetic variation, with only five out of twenty (25%) allozyme loci polymorphic (P), 1.35 alleles per locus (A), and an expected heterozygosity (H_e) of 0.090 at the species level. Isozymic genetic variation was even lower within populations (P = 17.5, A = 1.24, H_e = 0.074), and was corroborated by a RAPD assay that used 26 arbitrary primers (P = 3.61, A = 1.04, H_e = 0.014). Although overall levels of variation were low, the detectable variation was distributed as would be expected for an outcrossing species with extensive gene flow (mean G_ST = 0.230). We suspect thatP. guyannense is depauperate in genetic variation because of a series of bottlenecks that affected the species over this portion of its range.     

Low levels of genetic variation within and high levels of genetic differentiation among populations of species of Abies from southern Mexico and Guatemala

Populations of Abies in southern Mexico and Guatemala (A. flinckii, A. guatemalensis, A. hickeli, and A. religiosa) have a patchy distribution. This pattern is particularly clear in A. guatemalensis. Genetic diversity within populations, measured by average heterozygosity at 16 isozyme loci, is lower than the range reported for most conifers (mean H(o) ranging from 0.069 in A. guatemalensis to 0.113 in A. flinckii), while differentiation among populations is higher than that observed in most conifer species studied (θ = F(st) ranging from 0.073 in A. hickeli to 0.271 in A. flinckii). Estimated levels of gene flow are low (ranging from 0.672 in A. flinckii to 3.17 in A. hickeli). Populations in most cases had an excess of homozygosity over that expected under Hardy-Weinberg equilibrium, suggesting some inbreeding (F(is) ranging from 0.074 in A. flinckii to 0.235 in A. guatemalensis). A significant relationship between gene flow and geographic distance was observed in A. religiosa, but not in the other three taxa studied. The patterns of genetic variation appear to have been influenced by the distributions and histories of these species. Paleoclimatic evidence suggests that the ranges of these species retreated upwards during the Pleistocene glaciation and became fragmented during the warming period that followed. The populations could have passed through genetic bottlenecks that reduced genetic variation and led to interpopulation differentiation.     

Variation in self-fertility,inbreeding depression and levels of inbreeding in four Cyclamen species

The ability to self in the absence of pollinators, i.e. reproductive assurance, and the detrimental consequences of inbreeding, i.e. inbreeding depression, are central factors influencing plant mating system evolution. The purpose of this study was to quantify whether self-fertility and inbreeding depression are related to levels of inbreeding in four Cyclamen species, namely C. balearicum (mean F_is = 0.930), C. creticum (mean F_is = 0.748), C. repandum (mean F_is = 0.658) and C. hederifolium (mean F_is = 0.329). C. balearicum showed a markedly greater capacity to autonomously self-fertilize than the three other species, which may have favoured inbreeding in this species. Levels of inbreeding depression were highest in C. creticum and C. hederifolium at the fruit maturation (δ = 0.18 and 0.20, respectively) and seed number (δ = 0.32 and 0.30, respectively) stages, and for C. repandum at the seed weight stage (δ = 0.23). Although C. balearicum showed inbreeding depression on seed germination (δ = 0.45), this may be an artefact of the generally low levels of seed germination in the experiment. Overall, we observed only limited evidence for the predicted negative relation between inbreeding coefficients and levels of inbreeding since C. creticum had high levels of inbreeding and inbreeding depression. Other factors may thus influence the relationship between inbreeding and inbreeding depression in these species.     

What the reasons for no inbreeding and high genetic diversity of the neotropical fig tree Ficus arpazusa ?

Ficus arpazusa Casaretto is a fig tree native to the Atlantic Rain Forest sensu lato. High levels of genetic diversity and no inbreeding were observed in Ficus arpazusa. This genetic pattern is due to the action of its pollinator, Pegoscapus sp., which disperses pollen an estimated distance of 5.6 km, and of Ficus arpazusa’s mating system which, in the study area, is allogamous. This study highlights the importance of adding both ecological and genetic data into population studies, allowing a better understanding of evolutionary processes and in turn increasing the efficacy of forest management and revegetation projects, as well as species conservation.     

There are high levels of functional and genetic diversity in Oxyrrhis marina

Oxyrrhis marina, a widely distributed marine protist, is used to model heterotrophic flagellate responses in microbial food webs. Although clonal variability occurs in protists, assessments of intraspecific diversity are rare; such assessments are critical, particularly where species are used as models in ecological studies. To address the extent of intraspecific variation within O. marina, we assessed diversity among 11 strains using 5.8S rDNA and ITS sequences. The 5.8S rDNA and ITS regions revealed high divergence between strains: 63.1% between the most diverse. To compare O. marina diversity relative to other alveolates, 18S rDNA sequences for five strains were analysed with sequences from representatives of the major alveolate groups. 18S rDNA also revealed high divergence in O. marina. Additionally, consistent with phylogenies based on protein coding genes, maximum likelihood analysis indicated that O. marina was monophyletic and ancestral to the dinoflagellates. To assess ecophysiological differences, growth rates of seven O. marina strains were measured at 10 salinities (10-55 per thousand). Two salinity responses occurred: one group achieved highest growth rates at high salinities; the other grew best at low salinities. There was no clear correlation between molecular, ecophysiological, or geographical differences. However, salinity tolerance was associated with habitat type: intertidal strains grew best at high salinities; open-water strains grew best at low salinities. These data indicate the need to examine many strains of a species in both phylogenetic and ecological studies, especially where key-species are used to model ecological processes.     

Reappraisal of Primula ranunculoides (Primulaceae), an endangered species endemic to China,based on morphological,molecular genetic and reproductive characters

The taxonomic status of Primula ranunculoides and other members of section Ranunuculoides is reappraised here based on data from morphological, reproductive and molecular characters. Multivariate analysis of morphological characters indicates that P. ranunculoides is a coherent species that can be distinguished from its sectional congeners P. cicutariifolia and P. merrilliana by the characters of simple kidney‐shaped outer leaves and the unique clonal reproductive ability by which apices of the scape differentiate into bulblets at the late phases of flowering. Recognition of P. ranunculoides at the specific level is also supported by palynological characters, breeding system, cross pollination results and molecular phylogenetic analysis of nrDNA internal transcribed spacer sequences. A taxonomic revision of section Ranunuculoides is presented and a possible mechanism of speciation discussed. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 338–349.     

Allorecognition in the Tasmanian devil (Sarcophilus harrisii), an endangered marsupial species with limited genetic diversity

Tasmanian devils (Sarcophilus harrisii) are on the verge of extinction due to a transmissible cancer, devil facial tumour disease (DFTD). This tumour is an allograft that is transmitted between individuals without immune recognition of the tumour cells. The mechanism to explain this lack of immune recognition and acceptance is not well understood. It has been hypothesized that lack of genetic diversity at the Major Histocompatibility Complex (MHC) allowed the tumour cells to grow in genetically similar hosts without evoking an immune response to alloantigens. We conducted mixed lymphocyte reactions and skin grafts to measure functional MHC diversity in the Tasmanian devil population. The limited MHC diversity was sufficient to produce measurable mixed lymphocyte reactions. There was a wide range of responses, from low or no reaction to relatively strong responses. The highest responses occurred when lymphocytes from devils from the east of Tasmania were mixed with lymphocytes from devils from the west of Tasmania. All of the five successful skin allografts were rejected within 14 days after surgery, even though little or no MHC I and II mismatches were found. Extensive T-cell infiltration characterised the immune rejection. We conclude that Tasmanian devils are capable of allogeneic rejection. Consequently, a lack of functional allorecognition mechanisms in the devil population does not explain the transmission of a contagious cancer.