Genetic Consequences Of Habitat Fragmentation Research Articles

Conservation genetics of montane willow populations in Scotland—limited natural recovery despite long-distance gene flow and high genetic diversity

Plant species around the world are negatively affected by habitat fragmentation and climate change. Montane willow populations in the UK have declined primarily due to grazing, as well as climate change and muirburn in certain areas. Only small, isolated populations remain, scattered across steep ledges where shrubs escape most grazing animals. We explored the genetic effects of habitat fragmentation on gene flow and genetic diversity in the largest remaining patches in the UK, which lie in Scotland, for two now restricted and rare montane willow species—Salix myrsinites and Salix lapponum. Using ten microsatellite loci and an almost complete genetic inventory in the central Cairngorms area (S. myrsinites n = 186, S. lapponum n = 91) we showed that genetic diversity (heterozygosity and allelic richness) is relatively high in both species, particularly high for the decaploid S. myrsinites, and clonal reproduction low. Historic gene flow between populations could be demonstrated. Significant inbreeding was detected in both species and observed seed set and numbers of juveniles in the field are low, possibly indicating signs of inbreeding depression. Both species have extremely low numbers of individuals at each site, with many being smaller than ten, and in some cases combined with skewed sex-ratios (mainly female biased). This will likely cause more severe reproductive failures in the next generations unless population numbers are increased. Reinforcing populations of both species under low grazing pressure with new, unrelated individuals, as well as creating new stepping-stone populations will be necessary to help the recovery of these species. Results from this study will inform restoration work in Scotland aiming to create continuous woodland habitats from pinewoods at lower altitudes through to higher altitude downy birch woodlands merging with montane willows.

Population structure and genetic variation of fragmented mountain birch forests in Iceland.

Betula pubescens Ehrh. (mountain birch) is the only forest-forming tree in Iceland. Since human settlement (874 AD), the continuous 25,000 to 30,000 km2 forest has shrunk to 1.200 km2 of fragmented patches, making it a good object to study population genetic consequences of habitat fragmentation and disturbance. Further, genetic studies have also shown that hybridization between the tetraploid (2n = 56) B. pubescens and the diploid (2n = 28) Betula nana L. (dwarf birch) occurs among Iceland's natural populations. This study assessed the genetic variation within and among 11 birch forests remaining across Iceland. Genotype-by-sequencing methodology provided a total of 24,585 single nucleotide polymorphisms (SNP´s), with a minor allele frequency >5% for genetic analyses. The analysis showed similar diversity within forests, suggesting that fragmentation and hybridization have had a limited effect on the genetic variation within sites. A clear genetic divergence is found among forests from the different regions of Iceland that may reflect historical isolation; the differentiation between forests increased with geographic distances reflecting isolation by distance. Information on the distribution of genetic variation of birch in Iceland is essential for its conservation and to establish genotype-phenotype associations to predict responses to new environmental conditions imposed by climate change and novel biotic/abiotic stressors.

A Comparative Study of Genetic Responses to Short- and Long-Term Habitat Fragmentation in a Distylous Herb Hedyotis chyrsotricha (Rubiaceae).

The genetic effects of habitat fragmentation are complex and are influenced by both species traits and landscape features. For plants with strong seed or pollen dispersal capabilities, the question of whether the genetic erosion of an isolated population becomes stronger or is counterbalanced by sufficient gene flow across landscapes as the timescales of fragmentation increase has been less studied. In this study, we compared the population structure and genetic diversity of a distylous herb, Hedyotis chyrsotricha (Rubiaceae), in two contrasting island systems of southeast China. Based on RAD-Seq data, our results showed that populations from the artificially created Thousand-Island Lake (TIL) harbored significantly higher levels of genetic diversity than those from the Holocene-dated Zhoushan Archipelago (ZA) (π = 0.247 vs. 0.208, HO = 0.307 vs. 0.256, HE = 0.228 vs. 0.190), while genetic differences between island and mainland populations were significant in neither the TIL region nor the ZA region. A certain level of population substructure was found in TIL populations, and the level of gene flow among TIL populations was also lower than in ZA populations (m = 0.019 vs. 0.027). Overall, our comparative study revealed that genetic erosion has not become much stronger for the island populations of either the TIL or ZA regions. Our results emphasized that the matrix of water in the island system may facilitate the seed (fruit) dispersal of H. chrysotricha, thus maintaining population connectivity and providing ongoing resilience to the effects of habitat fragmentation over thousands of years.

Impacts of Chronic Habitat Fragmentation on Genetic Diversity of Natural Populations of Prunus persica in China.

Wild peach is an important resource for improving existing peach varieties. However, the extant populations of wild peach show fragmented distribution due to human disturbance and geographic isolation. In this study, we used natural populations (or wild populations) of Prunus persica (Rosaceae) to assess the genetic effects of habitat fragmentation. A total of 368 individuals sampled from 16 natural populations were analyzed using 23 polymorphic simple sequence repeat (SSR) markers. Prunus persica maintained low within-population genetic variation and high level of genetic differentiation. Two genetic clusters were revealed based on three different methods (UPGMA, PCoA, and STRUCTURE). All populations showed a significant heterozygosity deficiency and most extant populations experienced recent reduction in population size. A significant isolation by distance (IBD) was observed with Mantel’s test. Compared to historical gene flow, contemporary gene flow was restricted among the studied populations, suggesting a decrease in gene flow due to habitat fragmentation. Habitat fragmentation has impacted population genetic variation and genetic structure of P. persica. For breeding and conservation purpose, collecting as many individuals as possible from multiple populations to maximize genetic diversity was recommended during the process of germplasm collection. In addition, populations from central China had higher genetic diversity, suggesting these populations should be given priority for conservation and germplasm collection.

Assessing the genetic consequences of habitat fragmentation on the federally threatened cheat mountain salamander (Plethodon nettingi): a comparative, multi-locus approach

Assessing the genetic consequences of habitat fragmentation on the federally threatened cheat mountain salamander (Plethodon nettingi): a comparative, multi-locus approach

Plastic and quantitative genetic divergence mirror environmental gradients among wild, fragmented populations of Impatiens capensis.

Habitat fragmentation generates molecular genetic divergence among isolated populations, but few studies have assessed phenotypic divergence and fitness in populations where the genetic consequences of habitat fragmentation are known. Phenotypic divergence could reflect plasticity, local adaptation, and/or genetic drift. We examined patterns and potential drivers of phenotypic divergence among 12 populations of jewelweed (Impatiens capensis) that show strong molecular genetic signals of isolation and drift among fragmented habitats. We measured morphological and reproductive traits in both maternal plants within natural populations and their self-fertilized progeny grown together in a common garden. We also quantified environmental divergence between home sites and the common garden. Populations with less molecular genetic variation expressed less maternal phenotypic variation. Progeny in the common garden converged in phenotypes relative to their wild mothers but retained among-population differences in morphology, survival, and reproduction. Among-population phenotypic variance was 3-10× greater in home sites than in the common garden for 6 of 7 morphological traits measured. Patterns of phenotypic divergence paralleled environmental gradients in ways suggestive of adaptation. Progeny resembled their mothers less as the environmental distance between their home site and the common garden increased. Despite strong molecular signatures of isolation and drift, phenotypic differences among these Impatiens populations appear to reflect both adaptive quantitative genetic divergence and plasticity. Quantifying the extent of local adaptation and plasticity and how these covary with molecular and phenotypic variation help us predict when populations may lose their adaptive capacity.

Genetic consequences of habitat fragmentation in a perennial plant Trillium camschatcense are subjected to its slow‐paced life history

AbstractMany wild populations are suffering from the loss of genetic diversity caused by habitat fragmentation, while the degree of diversity loss differs among species and populations based on their life history characteristics. Trillium camschatcense, an understory perennial plant, has undergone intensive habitat fragmentation in the Tokachi region, Hokkaido, Japan. Although demographic deteriorations, such as reduced seed production, were already reported, genetic consequences of fragmentation have not been studied with reference to its life history. Here, we examined how life history events (e.g., growth and reproduction) and the stochasticity therein influence genetic diversity in two (each large and small) fragmented T. camschatcense populations. Genetic diversity was evaluated using genome‐wide 2,008 single nucleotide polymorphisms (SNPs). In the small population, genetic diversity of newly germinated seedlings was significantly lower than that of matured life history stages, and effective number of breeders (Nb) was smaller than that of the large population. Simulations using a matrix population model showed that the diversity loss at seedlings is caused by genetic drift during reproduction, which was intensified by smaller Nb. Besides, simulations using randomly perturbed transition matrices suggested that stasis at juvenile stages, which is a common characteristics of T. camschatcense, maintains genetic diversity by buffering stochastic decrease, possibly contributing to population viability. While previous studies showed the importance to facilitate reproduction and recruitment for demographic recovery, this study highlighted the crucial roles of juvenile survival in terms of genetic diversity for the conservation of fragmented T. camschatcense populations in the Tokachi region.

Landscape resistance affects individual habitat selection but not genetic relatedness in a reintroduced desert ungulate

The long-term success of species reintroductions is strongly dependent on the availability of large areas of suitable habitat and the genetic make-up of the population. If available habitat is poorly connected this can hinder gene flow and lead to genetic fragmentation of the population, potentially increasing its extinction risk. We employed a conservation genomics approach in which we combined analyses of genetic structure with testing for potential landscape effects on habitat selection and gene flow in reintroduced Asiatic wild ass Equus hemionus ssp. in the Israeli Negev desert. Genetic structure and pairwise relatedness were first investigated followed by examination of landscape effects on individual habitat selection using records of GPS collared individuals. We then built habitat resistance surfaces and used electrical circuit theory to test for landscape effects on genetic relatedness. We detected weak genetic structuring, yet low spatial coherence among individuals from the same genetic cluster. Landscape variables had a significant impact on individual habitat selection, with wild ass avoiding steep slopes and habitats of low suitability as predicted by a species distribution model. However, the landscape genetic analysis revealed no effect of habitat resistance on genetic relatedness. These results suggest that gene flow in the reintroduced population is not impacted by landscape resistance. Indeed, the high mobility of the species may increase its resistance to the genetic effects of habitat fragmentation, at least over a small number of generations. We discuss other potential causes for the observed genetic structure including a behavioural effect. Our study highlights the importance of understanding species-habitat interactions for the long-term success of reintroductions.

Scale-dependent effects of habitat fragmentation on the genetic diversity of Actinidia chinensis populations in China

Spatial scale partly explains the differentiated effects of habitat fragmentation on plant biodiversity, but the mechanisms remain unclear. To investigate the effects of habitat fragmentation on genetic diversity at different scales, we sampled Actinidia chinensis Planch. at broad and fine scales, China. The broad-scale sampling included five mountain populations and one oceanic island population (Zhoushan Archipelago), and the fine-scale sampling covered 11 lake islands and three neighboring land populations in Thousand-Island Lake (TIL). These populations were genotyped at 30 microsatellite loci, and genetic diversity, gene flow, and genetic differentiation were evaluated. Genetic differentiation was positively related to geographical distance at the broad scale, indicating an isolation-by-distance effect of habitat fragmentation on genetic diversity. The oceanic population differed from the mainland populations and experienced recent bottleneck events, but it showed high gene flow with low genetic differentiation from a mountain population connected by the Yangtze River. At the fine scale, no negative genetic effects of habitat fragmentation were found because seed dispersal with water facilitates gene flow between islands. The population size of A. chinensis was positively correlated with the area of TIL islands, supporting island biogeography theory, but no correlation was found between genetic diversity and island area. Our results highlight the scale-dependent effects of habitat fragmentation on genetic diversity and the importance of connectivity between island-like isolated habitats at both the broad and fine scales.

Isolation and characterization of microsatellite loci in Astroniumgraveolens (Anacardiaceae) and cross amplification in related species.

Microsatellite markers are a useful genetic tool to answer ecological and conservation genetics questions. Microsatellite primers were developed and characterized to evaluate forest fragmentation effects on genetic structure, diversity and gene flow patterns in the dioecious tropical tree Astroniumgraveolens (Anacardiaceae). Using genomic library enrichment, sixteen microsatellite loci were developed for A.graveolens. Polymorphism was evaluated in 80 individuals from four localities in Mexico. The overall number of alleles detected was 63, average alleles per locus 3.9 with a range from one to 11 per locus. Cross amplification trails on related species in the Anacardiaceae family: Spondiaspurpurea and Amphipterygiumadstringens, achieved successful amplification for all primers. Microsatellite markers described here are the first to be characterized for A.graveolens. These genetic markers will be a useful tool to assess the genetic consequences of habitat fragmentation and selective logging on A.graveolens populations. Cross amplification success on S.purpureaandA.adstringens suggest that they may be used for population genetic studies in other species within the family.

Microsatellite analysis reveals the resilience of genetic diversity within extant populations of three Akebia species to chronic forest fragmentation in China

The species of Akebia Decne are well-known medicinal plants and have been used in Chinese herbalism for at least 2000 years. The Akebia fruits have a delicious flavor and high nutritional value and are especially rich in antineoplastic, diuretic and antiphlogistic properties, making them worthy of being exploited as a new high-value crop. However, the nature habitats of the Akebia species have been fragmented due to rapid and intensive expansion of agricultural land. In this study, population genetics based on simple sequence repeat markers were conducted on the three most economically important Akebia species in order to reveal the genetic effects of habitat fragmentation to gain useful information for conservation and management of genetic resources of Akebia. Three Akebia species maintained high within-population genetic variation and low level of genetic differentiation. Mantel’s test indicated that there was a significantly positive correlation between genetic distance and geographic distance. Our results reveal the resilience of genetic diversity within extant populations of three Akebia species to chronic forest fragmentation. For breeding purpose, germplasm collection for sampling as many individuals as possible from many populations to maximize genetic diversity of the species is recommended. In addition, natural introgression events have been revealed by Cluster and Structure analysis where admixed ancestry occurred across three marginal populations of A. trifoliata ssp. australis, suggesting these populations should be given priority for germplasm collection.

Fine‐scale genetic structure in an eastern Alpine black grouse Tetrao tetrix metapopulation

Understanding genetic consequences of habitat fragmentation is crucial for the management and conservation of wildlife populations, especially in case of species sensitive to environmental changes and landscape alteration. In central Europe, the Alps are the core area of black grouse Tetrao tetrix distribution. There, black grouse dispersal is limited by high altitude mountain ridges and recent black grouse habitats are known to show some degree of natural fragmentation. Additionally, substantial anthropogenic fragmentation has occurred within the past ninety years. Facing losses of peripheral subpopulations and ongoing range contractions, we explored genetic variability and the fine‐scale genetic structure of the Alpine black grouse metapopulation at the easternmost fringe of the species’ Alpine range. Two hundred and fifty tissue samples and non‐invasive faecal and feather samples of eleven a priori defined subpopulations were used for genetic analysis based on nine microsatellite loci. Overall, eastern Alpine black grouse show similar amounts of genetic variation (HO = 0.65, HE = 0.66) to those found in more continuous populations like in Scandinavia. Despite of naturally and anthropogenically fragmented landscapes, genetic structuring was weak (global FST < 0.05), suggesting that the actual intensity of habitat fragmentation does not completely hamper dispersal, but probably restricts it to some extent. The most peripheral subpopulations at the edge of the species range show signs of genetic differentiation. The present study gives new insights into the population genetic structure of black grouse in the eastern Alps and provides a more fine‐scale view of genetic structure than previously available. Our findings will contribute to monitor the current and future status of the population under human pressures and to support supra‐regional land use planning as well as decision making processes in responsibilities of public administration.

Phylogeography and genetic effects of habitat fragmentation on endemic Urophysa (Ranunculaceae) in Yungui Plateau and adjacent regions.

Urophysa is a Chinese endemic genus with only two species (U. rockii and U. henryi) distributed in Yungui Plateau (Guizhou Province) and adjacent regions (i.e., Provinces of Hunan, Hubei, Chongqing and Sichuan). The aim of this study was to determine the genetic diversity and population differentiation within Urophysa and investigate the effect of the Yungui Plateau uplift and climate oscillations on evolution of Urophysa. In this study, micro-morphological characteristics, nine microsatellite loci (SSR), two nuclear loci (ITS and ETS) and two chloroplast fragments (psbA-trnH and trnL-trnF) were used to analyze the phylogenetic relationships and assess genetic and phylogeographical structure of Urophysa. Isolation by distance (IBD) was performed to research the effects of geographical isolation. We detected high genetic diversity at the species level but low genetic diversity within populations. Striking genetic differentiation (AMOVA) among populations and a significant phylogeographical structure (NST > GST, p < 0.01) were detected among U. henryi populations, along with significant effects of isolation by distance (IBD). Molecular clock estimation using calibration strategy and cpDNA substitution rate indicated that the divergence of U. henryi occurred during late Miocene to early Quaternary, when the orogeny of Yungui Plateau was violent. U. rockii originated at the early Quaternary and further differentiated at early Pleistocene. Our results suggested that habitat fragmentation played an important role in the genetic diversity and population differentiation of U. rockii and U. henryi. Heterogenous geomorphological configuration and complicated environment resulted from rapid uplift of the Yungui Plateau were inferred as important incentives for the modern phylogeograhpical pattern and species divergence of Urophysa. The geographical isolation, limited gene flow, specialized morphologies and the Pleistocene climatic oscillation greatly contributed to the allopatric divergence of U. rockii. Significant genetic drift and inbreeding were detected in these two species, in situ measures should be implemented to protect them.

Butterfly Genomics: Insights from the Genome ofMelitaea cinxia

The first lepidopteran genome (Bombyx mori) was published in 2004. Ten years later the genome of Melitaea cinxia came out as the third butterfly genome published, and the first eukaryotic genome sequenced in Finland. Owing to Ilkka Hanski, the M. cinxia system in the Aland Islands has become a famous model for metapopulation biology. More than 20 years of research on this system provides a strong ecological basis upon which a genetic framework could be built. Genetic knowledge is an essential addition for understanding eco-evolutionary dynamics and the genetic basis of variability in life history traits. Here we review the process of the M. cinxia genome project, its implications for lepidopteran genome evolution, and describe how the genome has been used for gene expression studies to identify genetic consequences of habitat fragmentation. Finally, we introduce some future possibilities and challenges for genomic research in M. cinxia and other Lepidoptera.

Potential Population Genetic Consequences of Habitat Fragmentation in Central European Forest Trees and Associated Understorey Species—An Introductory Survey

Habitat fragmentation threatens the maintenance of genetic diversity of affected populations. Assessment of the risks associated with habitat fragmentation is a big challenge as the change in population genetic diversity is a dynamic process, often acting over long time periods and depending on various characteristics pertaining to both species (life history traits) and their populations (extrinsic characteristics). With this survey, we provide an introductory overview for persons who have to make or are interested in making predictions about the fate of forest-dwelling plant populations which have recently become fragmented and isolated from their main occurrences. We provide a concise introduction to the field of population genetics focusing on terms, processes and phenomena relevant to the maintenance of genetic diversity and vitality of plant populations. In particular the antagonistic effects of gene flow and random genetic drift are covered. A special chapter is devoted to Central European tree species (including the Carpathians) which we treat in detail with reference to an extensive literature survey on population genetic studies assembled from the whole of Europe. We further provide an overview of the population biology of associated understorey species. We conclude with recommended steps to be taken for the evaluation of potential perils of habitat fragmentation or population thinning for the genetics of tree populations. The complexity of effects exerted by life history traits and extrinsic characteristics of populations suggest population genetic development is strongly situation dependent. Therefore, we recommend following a case-by-case approach ideally supported by computer simulations to predict future population genetic development of both trees and associated understorey species.

The Effects of Human-Mediated Habitat Fragmentation on a Sedentary Woodland-Associated Species (Rhinolophus hipposideros) at Its Range Margin

Among the many anthropogenic modifications to earth's ecosystems, habitat loss and degradation pose the most immediate threat to many biota. The predicted consequences of fragmented habitats include lower species diversity, smaller population sizes, disrupted gene flow, increased drift and inbreeding and increased differentiation between neighbouring populations; all of which are thought to be further enhanced in species with low dispersal abilities. These factors, especially when occurring in tandem, can lead to an increased risk of extinction. To examine the genetic consequences of habitat fragmentation we selected an isolated population of a sedentary woodland specialist species (Rhinolophus hipposideros) to act as an indicator of disruptions to landscape level connectivity. Based on 491 individuals from 37 colonies our results revealed the presence of a broad North-Range/South-Range differentiation within this species in Ireland; a finding supported across datasets (mtDNA and nuclear microsatellites) ...

The genetic consequences of long term habitat fragmentation on a self-incompatible clonal plant, Linnaea borealis L.

Self-incompatible species with restricted seed and pollen flow are considered the most vulnerable to the deleterious genetic effects of habitat fragmentation. Immediate effects of fragmentation are expected to be loss of allelic diversity and differentiation of fragments by genetic drift. Later, loss of S allele diversity may lead to restricted mate availability, increased relatedness of genotypes within patches, accelerated loss of genetic diversity and eventual loss of capacity for seed production. We studied the self-incompatible clonal shrub Linnaea borealis within the Cairngorms National Park, Scotland, whose pinewood habitat has been fragmented for an extensive period, possibly millennia. Exhaustive sampling revealed 123 patches (median length 15m), 91% of which were further than the maximum pollen flow distance from their nearest neighbours (30m). Using ten microsatellite markers, only 21% of the patches produced more than one multilocus genotype. Individual genotypes extended from 1 to 74m. Bayesian clustering of the 179 multilocus genotypes revealed six clusters. One cluster occupied a geographically distinct area where seed production still occurs and showed significant genetic differentiation from (Fst=0.164, P<0.01) and significantly lower allelic richness (AR=4.0 vs AR=7.0 P<0.01) than the remainder of the sample set. Spatial genetic structure in the total sample set indicated significant relatedness of clones within the first 1.5km. Overall, L. borealis in Scotland seems to be experiencing extreme genetic effects of chronic population fragmentation with only 16% of patches having the capacity for seed production. Genetic rescue is being undertaken by transplanting unrelated clones from >1.5km distance into extant monoclonal patches.

Effects of habitat fragmentation on genetic diversity and population differentiation of Liposcelis bostrychophila badonnel (Psocoptera: Liposcelididae) as revealed by ISSR markers

Liposcelis bostrychophila is a globally important stored product pest that is adapted to many habitats and is difficult to control due to insecticide resistance. We evaluated effects of habitat fragmentation on the genetic diversity and differentiation of L. bostrychophila populations. These genetic data were collected in Wuhu city, China using inter-simple sequence repeat (ISSR). A total of 108 discernible DNA fragments were detected, 107 were polymorphic and the percentage of polymorphic bands (PPB) was 99.1%. Shannon’s information index (I) and Nei’s gene diversity (He) from four populations were ordered (high to low) as herbstore > flourmill > bedroom > library. Population differentiation (Gst = 0.41) was average in these populations. Analysis of molecular variation (AMOVA) showed that variation existed mainly within populations (68.1%). At the same time, gene flow (Nm = 0.72) was interpreted to be moderate. Cluster analysis showed a small degree of genetic distance among different isolates and permitted grouping the isolates of L. bostrychophila into three distinct clusters. The study demonstrated clear genetic effects of habitat fragmentation on L. bostrychophila populations. Genetic diversity decreased and genetic differentiation increased between remnant populations when habitats were fragmented. Gene flow is not impeded by habitat fragmentation due to the impact of human activities. These findings are of great use for the prevention and control of this pest.

Small but not isolated: a population genetic survey of the tropical tree Cariniana estrellensis (Lecythidaceae) in a highly fragmented habitat.

Here, we explore the mating pattern and genetic structure of a tropical tree species, Cariniana estrellensis, in a small population in which progeny arrays (n=399), all adults (n=28) and all seedlings (n=39) were genotyped at nine highly informative microsatellite loci. From progeny arrays we were able to identify the source tree for at least 78% of pollination events. The gene immigration rates, mainly attributable to pollen, were high, varying from 23.5 to 53%. Although gene dispersal over long distance was observed, the effective gene dispersal distances within the small population were relatively short, with mean pollination distances varying from 69.9 to 146.9 m, and seed dispersal distances occurring up to a mean of 119.6 m. Mating system analyses showed that C. estrellensis is an allogamous species (tm=0.999), with both biparental inbreeding (tm-ts=-0.016) and selfing rates (s=0.001) that are not significantly different from zero. Even though the population is small, the presence of private alleles in both seedlings and progeny arrays and the elevated rates of gene immigration indicate that the C. estrellensis population is not genetically isolated. However, genetic diversity expressed by allelic richness was significantly lower in postfragmentation life stages. Although there was a loss of genetic diversity, indicating susceptibility of C. estrellensis to habitat fragmentation, no evidence of inbreeding or spatial genetic structure was observed across generations. Overall, C. estrellensis showed some resilience to negative genetic effects of habitat fragmentation, but conservation strategies are needed to preserve the remaining genetic diversity of this population.

Are some life-history strategies more vulnerable to the genetic consequences of habitat fragmentation? A case study using South Australian Caladenia R. Br. (Orchidaceae) species

Habitat fragmentation, through land clearing, has been attributed in the demise of many species of plants and animals throughout the world (Kinzig and Harte 2000). Not surprisingly, much research effort has been devoted toward understanding the dynamics of populations subject to fragmentation.