Landscape genetics of a recent population extirpation in a burnet moth species

The intensification of agricultural land use over wide parts of Europe has led to the decline of semi-natural habitats, such as extensively used meadows, with those that remain often being small and isolated. These rapid changes in land use during recent decades have strongly affected populations inhabiting these ecosystems. Increasing habitat deterioration and declining permeability of the surrounding landscape matrix disrupt the gene flow within metapopulations. The burnet moth species Zygaena loti has suffered strongly from recent habitat fragmentation, as reflected by its declining abundance. We have studied its population genetic structure and found a high level of genetic diversity in some of the populations analysed, while others display low genetic diversity and a lack of heterozygosity. Zygaena loti was formerly highly abundant in meadows and along the skirts of forests. However, the species is currently restricted to isolated habitat remnants, which is reflected by the high genetic divergence among populations (F _ST: 0.136). Species distribution modelling as well as the spatial examination of panmictic clusters within the study area strongly support a scattered population structure for this species. We suggest that populations with a high level of genetic diversity still represent the former genetic structure of interconnected populations, while populations with low numbers of alleles, high F _IS values, and a lack of heterozygosity display the negative effects of reduced interconnectivity. A continuous exchange of individuals is necessary to maintain high genetic variability. Based on these results, we draw the general conclusion that more common taxa with originally large population networks and high genetic diversity suffer stronger from sudden habitat fragmentation than highly specialised species with lower genetic diversity which have persisted in isolated patches for long periods of time.     

Molecular biogeography of the arctic-alpine disjunct burnet moth species Zygaena exulans (Zygaenidae, Lepidoptera) in the Pyrenees and Alps

Aim The phylogeography of ‘southern’ species is relatively well studied in Europe. However, there are few data about ‘northern’ species, and so we studied the population genetic structure of the arctic‐alpine distributed burnet moth Zygaena exulans as an exemplar. Location and methods The allozymes of 209 individuals from seven populations (two from the Pyrenees, five from the Alps) were studied by electrophoresis. Results All 15 analysed loci were polymorphic. The mean genetic diversities were moderately high (A: 1.99; H_e: 11.5; P: 65%). Mean genetic diversities were significantly higher in the Alps than in the Pyrenees in all cases. F_ST was 5.4% and F_IS was 10%. Genetic distances were generally low with a mean of 0.022 between large populations. About 62% of the variance between populations was between the Alps and the Pyrenees. The two samples from the Pyrenees had no significant differentiation, whereas significant differentiation was detected between the populations from the Alps (F_ST = 2.8%, P = 0.02). Main conclusion Zygaena exulans had a continuous distribution between the Alps and the Pyrenees during the last ice age. Most probably, the species was not present in Iberia, and the samples from the Pyrenees are derived from the southern edge of the glacial distribution area and thus became genetically impoverished. Post‐glacial isolation in Alps and Pyrenees has resulted in a weak genetic differentiation between these two disjunct high mountain systems.     

Migration and Allee effects in the six-spot burnet moth Zygaena filipendulae

Abstract 1. Migration into local populations may increase the likelihood of persistence but emigration may decrease the persistence of small and isolated populations. The dispersal behaviour of a day-flying moth Zygaena filipendulae was examined to determine whether emigration is correlated positively or negatively with population size and host plant density.
2. A mark–release–recapture study showed that most moths moved small distances (< 40 m on average) and only 6% of movements were > 100 m.
3. Twenty-five individuals moved between populations, a measured exchange rate of 8%. Moths were more likely to move between patches that were close together and they moved to relatively large patches.
4. The fraction of residents increased with increasing population size in the patch and increasing host plant cover. Relatively high proportions of individuals left small patches with small moth populations.
5. Moths released in grassland lacking Lotus corniculatus (the host plant) tended to leave the area and biased their movement towards host plant areas, whereas those released within an area containing L. corniculatus tended to stay in that area.
6. Biased movement away from small populations and areas of low host plant density (normally with low population density) was found. This migration-mediated Allee effect is likely to decrease patch occupancy in metapopulations, the opposite of the rescue effect. The effects on metapopulation persistence are not known.     

Low genetic diversity and high levels of inbreeding in the Sinai primrose (Primula boveana), a species on the brink of extinction

The Sinai primrose (Primula boveana) is one of the most endangered plant species worldwide, with less than 200 wild individuals surviving in the Sinai mountains of Egypt. There has been a decline in both the number and size of its populations in recent times, possibly caused by threats that include habitat aridification and the impact of human activities. Studying the standing genetic variation and extent of inbreeding of P. boveana is necessary for the design of appropriate conservation strategies for this species. In the present work, we used a set of seven, recently developed, polymorphic microsatellite markers to characterize the genetic variation and levels of inbreeding of the extant populations of P. boveana. We found low levels of genetic variation (H _T = 0.470), high differentiation between populations (F _ST = 0.737, R _ST = 0.935), and very elevated levels of inbreeding (F = 0.862) due to recurrent selfing. These results may be the reflection of low levels of genetic variation and high levels of inbreeding over a long evolutionary period, suggesting that the current genetic pool of the species may enable P. boveana to persist in a habitat where water availability and pollinator services are restricted. Nevertheless, in sight of its rapidly dwindling abundance, it seems prudent to adopt swift measures, including habitat restoration and ex-situ conservation, to prevent the impending extinction of this emblematic species.     

青藏高原地区不同环境条件下鳞翅目昆虫物种多样性与系统发育多样性的初步研究

本研究以青藏高原鳞翅目蛾类为例,探究不同环境梯度下蛾类群落物种多样性及系统发育多样性,并探讨物种多样性与系统发育多样性、不同的环境因子与蛾类系统发育多样性之间的关系。结果表明:(1)波密的物种多样性和系统发育多样性程度最高;(2)系统发育多样性与物种多样性指数之间存在正相关关系,相关性排序为:物种丰富度(R=0.9740,P=4.30E-05)香农指数(R=0.8323,P=0.0103)Invsimpson指数(R=0.8061,P=0.0156)辛普森指数(R=0.6311,P=0.0933);(3)在21个环境因子中,有4个环境因子与系统发育多样性之间呈现显著相关,分别是最湿润季度的降水量、最热季度的降水量、最湿润月份的降水量和最湿润季度的平均气温,它们可能是影响青藏高原地区蛾类系统发育多样性的关键生态因子。     

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.     

Isolation and high genetic diversity in dwarf mountain toads (Capensibufo) from South Africa

Traditional models of amphibian dispersal and gene flow point to low dispersal and high philopatry. In recent years, this traditional view has been challenged and it appears that no general model holds across taxa. Conservation of amphibians cannot be addressed on an over‐arching scale, but must come on a case‐by‐case basis, especially for range‐restricted species where information on gene flow and migration must be incorporated into conservation efforts. The only two members of the genus Capensibufo Grandison, 1980 (Anura: Bufonidae) are range restricted small bufonids, with distributions limited to montane areas in South Africa. Using a Bayesian analysis of two mitochondrial markers (16S and ND2), we examined the genetic patterns in Capensibufo rosei and Capensibufo tradouwi in order to understand both taxonomic and geographic boundaries. These species were not monophyletic, and demonstrate no clear taxonomic boundaries. Instead, the genus is extremely diverse genetically, with distinct lineages confined to isolated mountains that represent geographic boundaries. In addition, bioclimatic modelling using MAXENT and scenarios of climatic conditions at both the present and last glacial maximum suggest multiple bioclimatic and physical barriers to gene flow at present and in the past. We conclude that members of the genus have very low vagility, that current taxonomic boundaries are inadequate, and that strong geographic structuring has undoubtedly contributed to genetic diversity at the species level, rather than the population level. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 822–834.     

Group feeding as a strategy for exploiting food resources in the burnet moth Pryeria sinica

Summary Pryeria sinica (Zygaenidae) larvae feed on young and growing leaves of Euonymus japonicus in groups. The larvae often defoliate their host plant. Hence, the larvae are occasionally subject to serious shortage in food resources. We hypothesize that larval aggregation is an adaptation for the economical utilization of limited food resources. To test this hypothesis, the patterns of resource utilization were studied on larvae settled on shoots of host plant in various group sizes. The amount of food resources in a shoot was affected by the following three factors; (1) shoot growth, (2) food consumption of larvae, and (3) inhibition of growth or degeneration of shoot by larval activity on it. These factors were measured and the efficiency in resource utilization was compared among groups of varied sizes. The loss in resources caused by the third factor was found to be decreased with group size, i.e., the larger the group size, the larvae utilized the food resources more economically. The advantages of group feeding in survival and reproduction of this species were discussed using a simple graphical model.     

Connections between species diversity and genetic diversity

Species diversity and genetic diversity remain the nearly exclusive domains of community ecology and population genetics, respectively, despite repeated recognition in the literature over the past 30 years of close parallels between these two levels of diversity. Species diversity within communities and genetic diversity within populations are hypothesized to co‐vary in space or time because of locality characteristics that influence the two levels of diversity via parallel processes, or because of direct effects of one level of diversity on the other via several different mechanisms. Here, we draw on a wide range of studies in ecology and evolution to examine the theoretical underpinnings of these hypotheses, review relevant empirical literature, and outline an agenda for future research. The plausibility of species diversity–genetic diversity relationships is supported by a variety of theoretical and empirical studies, and several recent studies provide direct, though preliminary support. Focusing on potential connections between species diversity and genetic diversity complements other approaches to synthesis at the ecology–evolution interface, and should contribute to conceptual unification of biodiversity research at the levels of genes and species.     

Parallel changes in genetic diversity and species diversity following a natural disturbance

We examined the spatial and temporal variation of species diversity and genetic diversity in a metacommunity comprising 16 species of freshwater gastropods. We monitored species abundance at five localities of the Ain river floodplain in southeastern France, over a period of four years. Using 190 AFLP loci, we monitored the genetic diversity of Radix balthica , one of the most abundant gastropod species of the metacommunity, twice during that period. An exceptionally intense drought occurred during the last two years and differentially affected the study sites. This allowed us to test the effect of natural disturbances on changes in both genetic and species diversity. Overall, local (alpha) diversity declined as reflected by lower values of gene diversity H _S and evenness. In parallel, the among-sites (beta) diversity increased at both the genetic ( F _ST) and species ( F _STC) levels. These results suggest that disturbances can lead to similar changes in genetic and community structure through the combined effects of selective and neutral processes.     

Ecophysiology and genetic diversity in species of the bamboo Chusquea in the high Andes,Venezuela

ABSTRACT

Background: Woody bamboos of the genus Chusquea grow along a broad range of elevations in the Venezuelan Andes. Their growth-form and density vary along the cloud forest – páramo gradient. In this article, we related ecophysiological traits and population genetic diversity information to explain the distribution of growth-form patterns of Chusquea in the Merida Andes, Venezuela.

Aims: We quantified differences in the ecophysiological response and genetic diversity of scandent cloud forest and shrub-like páramo bamboos of the genus Chusquea, taking in account the differences in their flowering patterns, growth-form and habitat.

Methods: We related low temperature resistance, water relations and leaf gas exchange variables to the growth-form, habitat, flowering patterns and genetic diversity in species of Chusquea. The genetic diversity study was based on Inter Sequence Simple Repeats and Random Amplified Polymorphic DNA markers analysis of cloud forest and páramo populations.

Results: Scandent cloud forest and shrub-like páramo species of Chusquea had a very similar ecophysiological response for all the variables analysed during wet and dry seasons and were capable of enduring freezing temperatures through moderate supercooling. Species associated with the cloud forest – páramo gradient maintained low stomatal conductance and transpiration rates that favoured high leaf water potentials, without limiting photosynthetic rates. Shrub-like bamboos growing above the continuous forest line had a small decline in net photosynthesis rates, associated with an increase in water use efficiency. Both scandent and shrub-like bamboos had a remarkably high genetic diversity, comparable to non-clonal species.

Conclusions: Species of Chusquea in the Venezuelan Andes are a physiologically relatively homogeneous group across a broad elevation gradient. Population genetic diversity appears to be more related with their flowering pattern and habitat conditions than with their growth form.     

Low gene flow but high genetic diversity in the threatened Mallorcan midwife toad Alytes muletensis

We investigated fine-scale genetic structuring in the rare and vulnerable Mallorcan midwife toad Alytes muletensis using eight polymorphic microsatellite markers. The current range of this amphibian is restricted to some 19 sites of which six are derived from reintroductions, all located in the mountain ranges of Mallorca. We sampled tadpoles from 14 pools covering 10 natural sites and two reintroduction sites for microsatellite DNA analyses. Relatively high levels of genetic variation were found in most pools (H(E) = 0.38-0.71, allelic richness = 2.6-6.2). Only at one pool has the population recently gone through a bottleneck. Dispersal between pools in different torrents does not occur whereas downstream dispersal between pools within the same torrent does happen at low frequencies. This occasional exchange of individuals does not lead to neighbouring pools in the same torrent being panmictic. This can be concluded because all F(ST) values (0.12-0.53) differ significantly from zero and STRUCTURE analyses identified neighbouring pools as separate populations. Furthermore, assignment and migration tests showed little exchange between neighbouring pools. If upstream locations or complete torrents go extinct, they are unlikely to be recolonized naturally. For conservation purposes, reintroductions of tadpoles to sites where local extinctions have occurred may therefore be advisable.     

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.     

Low genetic diversity in tepui summit vertebrates

The Pantepui region of South America, located in southern Venezuela, northern Brazil, and western Guyana, is characterized by table mountains (tepuis) made of Proterozoic (> 1.5 billion years old) sandstone - the highest reaching nearly 3 km - that are isolated from their surroundings by up to 1000 m high vertical cliffs (Figure 1A). Tepuis are among the most inaccessible places on earth (Supplemental information), and the majority of their summits have been visited less than the moon. Due to its age and topography [1,2], this region has been assumed to be an ideal nursery of speciation and a potential inland counterpart to oceanic islands [3,4]. High endemism has been reported for the flora (25% in vascular plants) and fauna (68.5% in amphibians and reptiles) of single tepuis [5,6], and an ancient origin has been postulated for some of these organisms. But, it has also been suggested that a few taxa living in habitats extending from lowlands to summits (e.g., savannah) invaded some of the more accessible tepuis only recently [6-8]. Taken at face value, the overall timing and extent of biotic interchange between tepui summits has remained unstudied. Here, we show that recent faunal interchange among currently isolated tepui summits has been extensive, and affected even taxa living in some of the most tepui-specific habitats and on the most inaccessible summits.     

Ecology: linking species diversity and genetic diversity

Although there is a great deal of interest in the biological diversity of species and of genes, it is only recently that researchers have begun to investigate the processes that exert parallel influences on these different levels of diversity.     

Multiple geographic origins and high genetic differentiation of the Alpine marmots reintroduced in the Pyrenees

Reintroductions inherently involve a small number of founders leading reintroduced populations to be prone to genetic drift and, consequently, to inbreeding depression. Assessing the origins as the genetic diversity and structure of reintroduced populations compared to native populations are thus crucial to foresee their future. Here, we aim to clarify the origins of the Alpine marmots reintroduced in the Pyrenees and to evaluate the genetic consequences of this reintroduction after almost 30 years without monitoring. We search for the origins and compare the genetic structure and the genetic variability of three reintroduced Pyrenean and eight native Alpine populations using pairwise genetic distances, Bayesian clustering method and multivariate analyses. Our results reveal that the Alpine marmots reintroduced in the Pyrenees originated both from the Northern and the Southern Alps, and that, despite these multiple origins, none of the current Pyrenean marmots are admixed. The reintroduction led to a strong genetic differentiation and to a decrease in genetic diversity. This pattern likely results from the small number of founders and the low dispersal capacities of Alpine marmots and thus, highlight the necessity to consider both genetic characteristics and natural history when reintroducing a species.     

Low genetic diversity in a marine nature reserve: re-evaluating diversity criteria in reserve design

Little consideration has been given to the genetic composition of populations associated with marine reserves, as reserve designation is generally to protect specific species, communities or habitats. Nevertheless, it is important to conserve genetic diversity since it provides the raw material for the maintenance of species diversity over longer, evolutionary time-scales and may also confer the basis for adaptation to environmental change. Many current marine reserves are small in size and isolated to some degree (e.g. sea loughs and offshore islands). While such features enable easier management, they may have important implications for the genetic structure of protected populations, the ability of populations to recover from local catastrophes and the potential for marine reserves to act as sources of propagules for surrounding areas. Here, we present a case study demonstrating genetic differentiation, isolation, inbreeding and reduced genetic diversity in populations of the dogwhelk Nucella lapillus in Lough Hyne Marine Nature Reserve (an isolated sea lough in southern Ireland), compared with populations on the local adjacent open coast and populations in England, Wales and France. Our study demonstrates that this sea lough is isolated from open coast populations, and highlights that there may be long-term genetic consequences of selecting reserves on the basis of isolation and ease of protection.     

Population decline despite high genetic diversity in the new allopolyploid species Senecio cambrensis (Asteraceae)

Senecio cambrensis (Welsh groundsel) is a new allohexaploid species, which originated in Wales, UK, in the early part of the 20th century following hybridization between the native tetraploid groundsel (Senecio vulgaris) and the introduced diploid Oxford ragwort (Senecio squalidus). A survey of the number of populations and flowering individuals per population of S. cambrensis in Wales was conducted at peak flowering time in June 2002, 2003 and 2004. The results show a dramatic decrease in both population number and population size of the species since the 1980s when the last population census was conducted. A survey of amplified fragment length polymorphism (AFLP) variation showed that this decline has occurred despite the fact that S. cambrensis contains a high level of genetic diversity with each individual screened possessing a unique multilocus phenotype. The level of variance within the species was similar to that found in one parent (S. vulgaris) and slightly greater than that among samples of the other parent (S. squalidus). Only a small proportion (5%) of AFLP diversity was partitioned among populations indicating a lack of population structure and possibly high levels of gene flow via seed dispersal in what is predominantly a selfing species. Senecio cambrensis showed closer similarity in AFLP phenotype to S. vulgaris than to S. squalidus. Possible causes of this and also the high level of AFLP diversity found in S. cambrensis are discussed. It is suggested that intergenomic recombination following occasional multivalent formation during meiosis in S. cambrensis is likely to be an important cause of both phenomena, although other causes are not ruled out.     

Low population differentiation and high genetic diversity in the invasive species Carduus acanthoides L. (Asteraceae) within its native range in the Czech Republic

Colonizing species are predicted to suffer from reductions in genetic diversity during founding events. Although there is no unique mode of reproduction that is characteristic of successful plant colonizers, many of them are predominantly self-fertilizing or apomictic species, and almost all outcrossing colonizers are self-compatible. Carduus acanthoides comprises a species of disturbed habitats with wind-dispersed seeds that colonizes open spaces of various sizes. Population genetic diversity was expressed by assessing patterns of variation at nine putatively neutral allozyme loci within and among 20 natural populations in its native distribution range in the Czech Republic. Overall, C. acanthoides displayed high levels of genetic diversity compared to other herbaceous plants. The percentage of polymorphic loci was 84.5, with values of 2.37, 0.330, and 0.364 for the mean number of alleles per polymorphic locus ( A ), observed heterozygosity ( H _o), and expected heterozygosity ( H _e), respectively. There was only weak evidence of inbreeding within populations ( f  = 0.097) and very low genetic differentiation among populations ( θ  = 0.085). Analyses of the data provide strong evidence for isolation-by-distance for the whole study area. Even the colonizing species, C. acanthoides , currently supports a substantial amount of allozyme variation at both the species and population levels.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 596–607.