Dispersal ecology of the endangered woodland lichen Lobaria pulmonaria in managed hemiboreal forest landscape

Changes in the forest management practices have strongly influenced the distribution of species inhabiting old-growth forests. The epiphytic woodland lichen Lobaria pulmonaria is frequently used as a model species to study the factors affecting the population biology of lichens. We sampled 252 L. pulmonaria individuals from 12 populations representing three woodland types differing in their ecological continuity and management intensity in Estonia. We used eight mycobiont-specific microsatellite loci to quantify genetic diversity among the populations. We calculated the Sørensen distance to estimate genetic dissimilarity among individuals within populations. We revealed that L. pulmonaria populations have significantly higher genetic diversity in old-growth forests than in managed forests and wooded meadows. We detected a significant woodland-type-specific pattern of genetic dissimilarity among neighbouring L. pulmonaria individuals, which suggests that in wooded meadows and managed forests dominating is vegetative reproduction. The vegetative dispersal distance between the host trees of L. pulmonaria was found to be only 15–30 m. Genetic dissimilarity among individuals was also dependent on tree species and trunk diameter. Lobaria pulmonaria populations in managed forests included less juveniles compared to old-growth forests and wooded meadows, indicating that forest management influences life stage structure within populations. We conclude that as intensive stand management reduces the genetic diversity of threatened species in woodland habitats, particular attention should be paid to the preservation of remnant populations in old-growth habitats. Within managed habitats, conservation management should target on maintenance of the stand’s structural diversity and availability of potential host trees.     

Population structure and genetic diversity of black redhorse (Moxostoma duquesnei) in a highly fragmented watershed

Dams have the potential to affect population size and connectivity, reduce genetic diversity, and increase genetic differences among isolated riverine fish populations. Previous research has reported adverse effects on the distribution and demographics of black redhorse (Moxostoma duquesnei), a threatened fish species in Canada. However, effects on genetic diversity and population structure are unknown. We used microsatellite DNA markers to assess the number of genetic populations in the Grand River (Ontario) and to test whether dams have resulted in a loss of genetic diversity and increased genetic differentiation among populations. Three hundred and seventy-seven individuals from eight Grand River sites were genotyped at eight microsatellite loci. Measures of genetic diversity were moderately high and not significantly different among populations; strong evidence of recent population bottlenecks was not detected. Pairwise F_ST and exact tests identified weak (global F_ST = 0.011) but statistically significant population structure, although little population structuring was detected using either genetic distances or an individual-based clustering method. Neither geographic distance nor the number of intervening dams were correlated with pairwise differences among populations. Tests for regional equilibrium indicate that Grand River populations were either in equilibrium between gene flow and genetic drift or that gene flow is more influential than drift. While studies on other species have identified strong dam-related effects on genetic diversity and population structure, this study suggests that barrier permeability, river fragment length and the ecological characteristics of affected species can counterbalance dam-related effects.     

High genetic diversity in the remnant island population of hihi and the genetic consequences of re-introduction

The maintenance of genetic diversity is thought to be fundamental for the conservation of threatened species. It is therefore important to understand how genetic diversity is affected by the re-introduction of threatened species. We use establishment history and genetic data from the remnant and re-introduced populations of a New Zealand endemic bird, the hihi Notiomystis cincta, to understand genetic diversity loss and quantify the genetic effects of re-introduction. Our data do not support any recent bottleneck events in the remnant population. Furthermore, all genetic diversity measures indicate the remnant hihi population has retained high levels of genetic diversity relative to other New Zealand avifauna with similar histories of decline. Genetic diversity (N(A) , alleles per locus, allelic richness, F(IS) and H(S) ) did not significantly decrease in new hihi populations founded through re-introduction when compared to their source populations, except in the Kapiti Island population (allelic richness and H(S) ) which had very slow post-re-introduction population growth. The N(e) /N(c) ratio in the remnant population was high, but decreased in first-level re-introductions, which together with significant genetic differentiation between populations (F(ST) & Fisher's exact tests) suggest that extant populations are diverging as a result of founder effects and drift. Importantly, simulations of future allele loss predict that the number of alleles lost will be higher in populations with a slow population growth, fewer founding individuals and with nonrandom mating. Interestingly, this species has very high levels of extra-pair paternity which may reduce reproductive variance by allowing social and floater males to reproduce a life history trait that together with a large remnant population size may help maintain higher levels of genetic diversity than expected.     

Genome-wide SNPs detect fine-scale genetic structure in threatened populations of squirrel glider Petaurus norfolcensis

Australian arboreal mammals are experiencing significant population declines, particularly due to land clearing and resulting habitat fragmentation. The squirrel glider, Petaurus norfolcensis, is a threatened species in New South Wales, with a stronghold population in the Lake Macquarie Local Government Area (LGA) where fragmentation due to urbanization is an ongoing problem for the species conservation. Here we report on the use of squirrel glider mitochondrial (385 bp cytochrome b gene, 70 individuals) and nuclear DNA (6,834 SNPs, 87 individuals) markers to assess their population genetic structure and connectivity across 14 locations sampled in the Lake Macquarie LGA. The mitochondrial DNA sequences detected evidence of a historical genetic bottleneck, while the genome-wide SNPs detected significant population structure in the Lake Macquarie squirrel glider populations at scales as fine as one kilometer. There was no evidence of inbreeding within patches, however there were clear effects of habitat fragmentation and biogeographical barriers on gene flow. A least cost path analysis identified thin linear corridors that have high priority for conservation. These areas should be protected to avoid further isolation of squirrel glider populations and the loss of genetic diversity through genetic drift.

     

Remaining genetic diversity in Brazilian Merganser (Mergus octosetaceus)

The Brazilian Merganser is a very rare and threatened species that nowadays inhabits only a few protected areas and their surroundings in the Brazilian territory. In order to estimate the remaining genetic diversity and population structure in this species, two mitochondrial genes were sequenced in 39 individuals belonging to two populations and in one individual collected in Argentina in 1950. We found a highly significant divergence between two major remaining populations of Mergus octosetaceus, which suggests a historical population structure in this species. Furthermore, two deeply divergent lineages were found in a single location, which could due to current or historical secondary contact. Based on the available genetic data, we point out future directions which would contribute to design strategies for conservation and management of this threatened species.     

Identifying Priority Giant Anteater (Myrmecophaga tridactyla) Populations for Conservation in São Paulo State,Brazil

Habitat loss is the main threat to biodiversity conservation worldwide. Some species may be particularly susceptible to the effects of fragmentation and the isolation of populations. The impacts of human activity on wild animal populations may be understood through relationships between individual genetic data and spatial landscape variables, particularly when considering local population dynamics influenced by fragmented habitats. Thus, the objective of this study was to analyze the population structure and genetic diversity of the giant anteater (Myrmecophaga tridactyla) using an individual sampling scheme (ISS) on a regional geographic scale. Data were collected from 41 specimens from twenty different locations in São Paulo State, Brazil, and six polymorphic microsatellite loci were genotyped. Our results indicate that barriers to gene flow exist and have segregated individuals of the farther away areas into two spatially structured clusters. The populations were also found to have high genetic diversity. The experimental sampling approach used herein enabled an analysis of the population dynamics of the giant anteater on a regional scale, as well as the identification of priority populations for genetic resource conservation for this species. The results reflect the need for adequate management plans. The efficacy of the sampling scheme may vary based on the study model used, but we argue that the use of an ISS combined with suitable molecular markers and statistical methods may serve as an important tool for initial analyses of threatened or vulnerable species, particularly in anthropized regions where populations are small or hard to characterize.     

Genetic diversity of Annona crassiflora (Annonaceae) in northern Minas Gerais State

Genetic diversity analyses of tropical tree species are relevant to landscape management, plant genetic resource inventory, and biological conservation of threatened species. Annona crassiflora is an endangered fruit tree native to the Cerrado biome that is threatened by reduction of natural populations and fruit extraction. We examined the intra- and interpopulational genetic diversity of this species in the northern region of Minas Gerais State. Seventy-two individuals from four natural populations were genotyped using RAPD markers. We found moderate genetic diversity among populations, with Shannon's I index varying between 0.31 and 0.44, and Nei's genetic diversity (H(E)) for the population set equal to 0.31. AMOVA indicated a greater genetic variation within (77.38%) rather than among populations (22.62%), tending towards isolation by distance (Mantel's r = 0.914; P = 0.089). Nei's genetic identity estimates among populations revealed a hierarchical pattern of genetic similarity of form [(CA1, CA2), MC], [(GM)], corroborating the high genetic differentiation between spatially isolated populations.     

Genetic Management of Captive and Reintroduced Bilby Populations

Captive breeding and translocation, whereby selected individuals are used to supplement or re-establish failing populations, are powerful tools for conserving threatened fauna. These tools, however, are rarely successful at establishing self-sustaining populations that can survive without ongoing human assistance. The maintenance of genetic diversity and demographic security in captivity, or following wildlife translocation events, is important for improving the long-term effectiveness of threatened species recovery efforts around the world. Routine population monitoring using hypervariable genetic markers represents a promising technique for evaluating the effect of established management practices on population structure and genetic diversity across various spatial and temporal scales. In this study, we employed a data set of 1,068 single nucleotide polymorphisms to conduct a comprehensive survey of population structure and genetic diversity in greater bilbies (Macrotis lagotis) held at 13 zoos and wildlife sanctuaries across Australia between August 1996 and December 2016. We observed significant genetic structuring across the study sites, consistent with the limited exchange of animals between independently managed facilities. The majority of variation, however, still occurred at the level of individual bilbies (75%, P < 0.001). We also uncovered evidence for an ongoing loss of genetic diversity in some conservation-fenced populations, despite a slight excess of heterozygosity across the sampling sites as a whole. Maintaining the genetic health of bilbies in captivity or following translocation will therefore require stakeholders to focus on reducing individual mortality, and maintaining genetic connectivity across all existing populations through the regular exchange of selected individuals. As such, admixture is expected to play an increasingly important role in future conservation programs. © 2019 The Authors. Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

Managing genetic diversity in threatened populations: a New Zealand perspective

Genetic diversity allows a population to adapt genetically to a changing environment or to buffer it against stochastic events such as harsh weather or disease outbreaks. Genetic diversity is therefore an important consideration in the development of management strategies for threatened populations around the world, with the possible exception of New Zealand, where species recovery programmes tend to focus on increasing population size while neglecting the maintenance of genetic diversity. Many of New Zealand?s threatened species have relatively low genetic variation and consequently may still be at risk in the long-term due to reduced resilience even if the effects of introduced predators were eliminated. The three main factors affecting genetic diversity – genetic drift, inbreeding and population subdivision – are processes that potentially impact on many of our locally threatened species, but their effects tend to occur over a considerably broader timescale than ecological effects, and as such are much more difficult to detect and ultimately to justify additional resource spending towards. Our message is that genetic management of New Zealand threatened species should not take priority over other management concerns such as controlling predators or improving habitat quality, but it needs more attention than it currently receives. We recommend that genetic diversity be a fundamental component in long-term management strategies for threatened species, and that such strategies are made explicit within the New Zealand Department of Conservation?s current species recovery plans so that the persistence of biodiversity becomes of key importance, as opposed to current approaches that seek solely to maximise representation.     

Conservation Genetics of Jacquemontia reclinata (Convolvulaceae), an Endangered Species from Southern Florida: Implications for Restoration Management

Guidelines designed to aid in the restoration of rare species have been previously proposed using two primary strategies to select individuals for augmentation and reintroduction: mixing progeny from different populations or separating individuals from different populations. Understanding the genetic structure and diversity of an endangered species can offer insights into conservation management strategies. We used random amplified polymorphic DNA markers to assess the genetic structure and diversity of Jacquemontia reclinata , a federally endangered species endemic to Southeastern Florida. We sampled 20 percent of total number of individuals from eight of the ten known wild populations. Across individuals high levels of polymorphic loci (94.7%) were found and larger populations had greater genetic diversity. Cluster and ordination analyses found that one population was genetically differentiated from all the others; this population grows in a unique habitat. Most genetic variation (77.5%) was found within populations, and genetic distances between populations were not explained by their geographic distances. We recommend the use of two management units in restoration programs for J. reclinata , one consisting of the genetically differentiated population and the second consisting of the other seven populations sampled.     

Genetic structure,diversity and distribution of a threatened lizard affected by widespread habitat fragmentation

Understanding the demographic consequences of habitat loss on populations is essential for the conservation of threatened species. The threatened swamp skink (Lissolepis coventryi) is restricted to fragmented wetland habitats in Victoria and southeast South Australia. It has experienced significant habitat loss in the last 150 years, particularly around the Melbourne metropolitan area, where several small and isolated populations remain. Using mtDNA and nuDNA SNPs, we examined distribution patterns and population structure to infer evolutionary history and genetic distinctiveness of populations throughout the species’ range. For populations in the Melbourne metropolitan area, we examined genetic diversity. We found the species to be highly divergent, separating into two distinct lineages to the east and west of Melbourne, likely due to geological and climate influences causing isolation of populations. Species’ detectability was low, particularly in the far east despite relatively intact habitat and presumed higher abundance. Melbourne populations showed signs of limited genetic diversity. We suggest that translocations to promote gene diversity amongst these populations, together with habitat restoration and protection, present an important management strategy for L. coventryi.

     

Conservation genetics of the yellow-bellied toad (Bombina variegata): population structure,genetic diversity and landscape effects in an endangered amphibian

Revealing patterns of genetic diversity and barriers for gene flow are key points for successful conservation in endangered species. Methods based on molecular markers are also often used to delineate conservation units such as evolutionary significant units and management units. Here we combine phylo-geographic analyses (based on mtDNA) with population and landscape genetic analyses (based on microsatellites) for the endangered yellow-bellied toad Bombina variegata over a wide distribution range in Germany. Our analyses show that two genetic clusters are present in the study area, a northern and a southern/central one, but that these clusters are not deeply divergent. The genetic data suggest high fragmentation among toad occurrences and consequently low genetic diversity. Genetic diversity and genetic connectivity showed a negative relationship with road densities and urban areas surrounding toad occurrences, indicating that these landscape features act as barriers to gene flow. To preserve a maximum of genetic diversity, we recommend considering both genetic clusters as management units, and to increase gene flow among toad occurrences with the aim of restoring and protecting functional meta-populations within each of the clusters. Several isolated populations with especially low genetic diversity and signs of inbreeding need particular short-term conservation attention to avoid extinction. We also recommend to allow natural gene flow between both clusters but not to use individuals from one cluster for translocation or reintroduction into the other. Our results underscore the utility of molecular tools for species conservation, highlight outcomes of habitat fragmentation onto the genetic structure of an endangered amphibian and reveal particularly threatened populations in need for urgent conservation efforts.

     

Phylogeography,Population Structure,and Conservation of the Javan Gibbon (<Emphasis Type="Italic">Hylobates moloch</Emphasis>)

An understanding of phylogeography and population genetics is needed for a comprehensive long-term conservation management strategy. The Javan gibbon (Hylobates moloch), an Endangered species endemic to the island of Java, has been protected since 1924 but is threatened by ongoing habitat loss, habitat degradation, and the wildlife trade. We studied the phylogeography and population genetic structure of the Javan gibbon, to define the number of Evolutionary Significant Units (ESUs) in the species, and the population genetic structure in each ESU. We sampled 47 individuals, analyzing 35 for variation in mitochondrial DNA control region, 41 for variation in 8 nuclear DNA microsatellites, and 13 for variation in 45 nuclear DNA single nucleotide polymorphisms (SNPs). We found support for two ESUs across the species range: a western ESU, extending from Ujung Kulon to Gunung Gede–Pangrango, and a central ESU, extending from Gunung Masigit–Simpang–Tilu to Gunung Slamet. Analysis of molecular variance and population structure analysis indicate significant structuring in the western ESU between Ujung Kulon and Gunung Halimun–Salak–Gede–Pangrango, and little to moderate structure in the central ESU, underscoring the importance of conserving as many populations as possible to preserve the full array of genetic diversity in this species. Our results will inform future more comprehensive population genetic surveys and the conservation genetic management of the Javan gibbon. This study demonstrates the importance of genetics when designing conservation management strategies for endangered primates.     

Stepping into the past to conserve the future: Archived skin swabs from extant and extirpated populations inform genetic management of an endangered amphibian

Moving animals on a landscape through translocations and reintroductions is an important management tool used in the recovery of endangered species, particularly for the maintenance of population genetic diversity and structure. Management of imperiled amphibian species rely heavily on translocations and reintroductions, especially for species that have been brought to the brink of extinction by habitat loss, introduced species, and disease. One striking example of amphibian declines and associated management efforts is in California's Sequoia and Kings Canyon National Parks with the mountain yellow‐legged frog species complex (Rana sierrae/muscosa). Mountain yellow‐legged frogs have been extirpated from more than 93% of their historic range, and limited knowledge of their population genetics has made long‐term conservation planning difficult. To address this, we used 598 archived skin swabs from both extant and extirpated populations across 48 lake basins to generate a robust Illumina‐based nuclear amplicon data set. We found that samples grouped into three main genetic clusters, concordant with watershed boundaries. We also found evidence for historical gene flow across watershed boundaries with a north‐to‐south axis of migration. Finally, our results indicate that genetic diversity is not significantly different between populations with different disease histories. Our study offers specific management recommendations for imperiled mountain yellow‐legged frogs and, more broadly, provides a population genetic framework for leveraging minimally invasive samples for the conservation of threatened species.     

Diversity and structure of fragmented populations of a threatened endemic cyprinodontid (Aphanius sophiae) inferred from genetics and otolith morphology: Implications for conservation and management

The assessment of population structure and genetic diversity is crucial for the management and conservation of threatened species. Natural and artificial barriers to dispersal (i.e., gene flow) increase populations’ differentiation and isolation by reducing genetic exchange and diversity. Freshwater ecosystems are highly fragmented because of human activities. Threatened species with small population sizes are more sensitive to habitat fragmentation effects. Here, we investigate the genetic population structure and gene flow among seven populations of Aphanius sophiae in the Kor Basin by using sequences of the complete Cyt b gene and otolith morphometry. The Cyt b gene showed low level of genetic variation, only 4.12% of the identified sites were variable, and 2.42% were parsimony informative. Overall, haplotype diversity was low to moderate and nucleotide diversity was low to extremely low. Fish populations exhibited high levels of genetic differentiation, suggesting limited gene flow among them. These differences were obtained not only among geographically distant populations, but also among neighboring localities. Genetic population structure was supported by the AMOVA analysis and by the haplotype network (only one of 21 haplotypes were shared by two localities). Otolith morphometric analysis was in agreement with genetic results, the two most distant and isolated populations were clearly separated, and genetically close populations showed less differences in morphometry. A significant pattern of isolation by distance was also detected among A. sophiae populations, with genetic distance more correlated with hydrological distance than with geographic distance. Results suggested that limited gene flow due to habitat fragmentation is an important factor contributing to genetic structuring and to the loss of genetic variation of A. sophiae populations. Aphanius sophiae population structure seems to be the result of habitat fragmentation and water pollution, but other factors such as introduced species should be considered. Given the high degree of genetic structuring, the definition of conservation groups is of particular importance for A. sophiae, which should be considered endangered according to the IUCN criteria. Conservation plans must recognize the genetic independence of populations and manage separately preventing the loss of locally adapted genotypes.     

Optimizing the genetic management of reintroduction projects: genetic population structure of the captive Northern Bald Ibis population

Many threatened species are bred in captivity for conservation purposes and some of these programmes aim at future reintroduction. The Northern Bald Ibis, Geronticus eremita, is a Critically Endangered bird species, with recently only one population remaining in the wild (Morocco, Souss Massa region). During the last two decades, two breeding programs for reintroduction have been started (in Austria and Spain). As the genetic constitution of the founding population can have strong effects on reintroduction success, we studied the genetic diversity of the two source populations for reintroduction (‘Waldrappteam’ and ‘Proyecto eremita’) as well as the European zoo population (all individuals held ex situ) by genotyping 642 individuals at 15 microsatellite loci. To test the hypothesis that the wild population in Morocco and the extinct wild population in the Middle East belong to different evolutionary significant units, we sequenced two mitochondrial DNA fragments. Our results show that the European zoo population is genetically highly structured, reflecting separate breeding lines. Genetic diversity was highest in the historic samples from the wild eastern population. DNA sequencing revealed only a single substitution distinguishing the wild eastern and wild western population. Contrary to that, the microsatellite analysis showed a clear differentiation between them. This suggests that genetic differentiation between the two populations is recent and does not confirm the existence of two evolutionary significant units. The European zoo population appears to be vital and suitable for reintroduction, but the management of the European zoo population and the two source populations for reintroductions can be optimized to reach a higher level of admixture.     

Loss of genetic diversity in an outbreeding species: small population effects in the African wild dog <Emphasis Type="Italic">(Lycaon pictus</Emphasis>)

Genetic studies on the endangered African wild dog (Lycaon pictus) have primarily focused on the few remaining large and viable populations. However, investigations on the many isolated small African wild dog populations might also be informative for species management because the majority of extant populations are small and may contain genetic variability that is important for population persistence and for species conservation. Small populations are at higher risk of extinction from stochastic and deterministic demographic processes than larger populations and this is often of more immediate conservation concern than loss of genetic diversity, particularly for species that exhibit out-breeding behaviour such as long distance dispersal which may maintain gene flow. However, the genetic advantages of out-breeding behaviour may be reduced if dispersal is compromised beyond reserve borders (edge effects), further weakening the integrity of small populations. Mitochondrial DNA and 11 microsatellite genetic markers were used to investigate population genetic structure in a small population of out-breeding African wild dogs in Zambia, which occupies an historical dispersal corridor for the species. Results indicated the Zambian population suffered from low allelic richness, and there was significant evidence of a recent population bottleneck. Concurrent ecological data suggests these results were due to habitat fragmentation and restricted dispersal which compromised natural out-breeding mechanisms. This study recommends conservation priorities and management units for the African wild dog that focus on conserving remaining levels of genetic diversity, which may also be applicable for a range of out-breeding species.     

Genetic diversity is retained in a bottlenecked Cinereous Vulture population in Turkey

Vulture populations worldwide have suffered precipitous declines in recent decades. The Cinereous Vulture Aegypius monachus, a highly philopatric scavenger distributed across southern Europe and the central Asian plateau, is threatened in many parts of its range. Turkey holds the second largest population of this species in the Western Palaearctic, but there has been no research on its genetic structure and the possible implications of this structure for the future of the species. Here we report nuclear diversity and relatedness determined by short tandem repeat genotyping of 81 individuals from the four largest colonies. Our results demonstrated no significant genetic structuring, suggesting a single panmictic metapopulation connected by frequent dispersal. Furthermore, we show that the study population has retained moderate levels of genetic diversity, despite passing through a recent demographic bottleneck. We estimated the effective population size to be 112 individuals (95% confidence interval 74–201). Our results imply that the observed lack of increase in population size since the 1990s has not been caused by lowered fitness due to genetic inbreeding but rather by increased mortality via demographic processes. In the short term, we suggest that conservation efforts should treat the Turkish subpopulations as a single management unit and aim to increase population size through effective protection, especially during the breeding season.     

The impact of management practices and past demographic history on the genetic diversity of red deer (Cervus elaphus): an assessment of population and individual fitness

The influences of management practices and past demographic history on genetic diversity are of critical relevance to sustainable practices and the conservation of wildlife populations. The red deer (Cervus elaphus) is an interesting model species to address these questions because it has a wide geographical distribution and it has been intensively managed for humans in the last decades. In the present study, we have analyzed the impact of recent management practices on the genetic diversity of Iberian red deer populations and assessed the genetic variation effects on population and individual fitness‐related traits. Four populations subjected to distinct management systems were selected: Cabañeros (CB) and Doñana (DN), not hunted populations; Fraga/Caspe (FG/CP), open hunting area with very low or absent management; and PE, fenced private hunting estate founded 31 years ago through the introduction of deer of different origins. Ten microsatellites were amplified in a total of 172 individuals. Additionally, several fitness‐related traits such as the presence of tuberculosis compatible lesions (TBCL), spleen weight (SW), and body length (BL) were estimated. We found a marked genetic variation and differentiation among populations, suggesting a strong population structure. In the fenced population, the introduction of genetically distinct animals has led to high genetic variability (no evidence of inbreeding) despite intensive management. Lower levels of genetic diversity were observed in two historically isolated natural populations (DN and FG/CP). The past demographic history of Iberian populations appears to be more relevant than the current management policy in shaping the genetic variability of natural populations. Population genetic diversity may correlate with life‐history traits and disease susceptibility, which could compromise the conservation and management of these wildlife populations. Although no significant effects of individual genetic diversity (general and local effect hypotheses) were observed on TBCL, SW and BL, some single‐locus effects had almost significant trends for the TBCL and SW traits. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 209–223.     

The importance of reproductive strategies in population genetic approaches to conservation: an example from the marine angiosperm genus Zostera

Knowledge of the levels of genetic diversity maintained in natural populations can play a central role in conservation programmes, particularly in threatened habitats or species. Fluctuations in population size can lead to loss of variation and, consequently, increase the risk of extinction. We have examined whether such a genetic bottleneck has occurred in populations of two species in the seagrass genus Zostera, which are believed to have been affected by an outbreak of wasting disease at the start of the last century. A test for heterozygote excess at five nuclear microsatellite loci did not suggest the occurrence of a genetic bottleneck, but analysis of seven chloroplast microsatellite loci and sequence data from two regions did suggest a bottleneck in the chloroplast genome. Extremely low levels of between-population diversity suggest that all subpopulations can be treated as a single management unit for each species. Comparable levels of nuclear genetic diversity were found in the three populations of the primarily sexual Zostera marina var. angustifolia studied but a wider range of within-population diversity was found in Zostera noltii, which displays both sexual and vegetative reproductive strategies. This may be due to an increase in sexual recruitment due to localised fresh water inflow into the study site near to the most diverse population. Such populations should be prioritised as source material for any replanting or remediation due to natural or anthropogenic loss of Zostera beds in the area.