Drift happens: Molecular genetic diversity and differentiation among populations of jewelweed ( Impatiens capensis Meerb.) reflect fragmentation of floodplain forests

Resurrected seeds from herbarium specimens reveal rapid evolution of drought resistance in a selfing annual

PREMISE

Increased aridity and drought associated with climate change are exerting unprecedented selection pressures on plant populations. Whether populations can rapidly adapt, and which life history traits might confer increased fitness under drought, remain outstanding questions.

METHODS

We utilized a resurrection ecology approach, leveraging dormant seeds from herbarium collections to assess whether populations of Plantago patagonica from the semi-arid Colorado Plateau have rapidly evolved in response to approximately ten years of intense drought in the region. We quantified multiple traits associated with drought escape and drought resistance and assessed the survival of ancestors and descendants under simulated drought.

RESULTS

Descendant populations displayed a significant shift in resource allocation, in which they invested less in reproductive tissues and relatively more in both above- and below-ground vegetative tissues. Plants with greater leaf biomass survived longer under terminal drought; moreover, even after accounting for the effect of increased leaf biomass, descendant seedlings survived drought longer than their ancestors.

CONCLUSIONS

Our results document rapid adaptive evolution in response to climate change in a selfing annual and suggest that shifts in tissue allocation strategies may underlie adaptive responses to drought in arid or semi-arid environments. This work also illustrates a novel approach, documenting that under specific circumstances, seeds from herbarium specimens may provide an untapped source of dormant propagules for future resurrection experiments.

Deep genome-wide divergences among species in White Cloud Mountain minnow Tanichthys albonubes (Cypriniformes: Tanichthyidae) complex: Conservation and species management implications

Identifying cryptic species is important for the assessments of biodiversity. Further, untangling mechanisms underlying the origins of cryptic species can facilitate our understanding of evolutionary processes. Advancements in genomic approaches for non-model systems have offered unprecedented opportunities to investigate these areas. The White Cloud Mountain minnow (Tanichthys albonubes) is a popular freshwater pet fish worldwide but its wild populations in China are critically endangered. Recent research based on a few molecular markers suggested that this species in fact comprised seven cryptic species, of which six were previously unknown. Here, we tested six of these cryptic species and quantified genomic interspecific divergences between species in the T. albonubes complex by analyzing genome-wide restriction site-associated DNA sequencing (RADseq) data generated from 189 individuals sampled from seven populations (including an outgroup congeneric species, T. micagemmae). We found that six cryptic species previously suggested were well supported by RADseq data. The genetic diversity of each species in the T. albonubes complex was low compared with T. micagemmae and the contemporary effective population sizes (Ne) of each cryptic species were small. Phylogenetic analysis showed seven clades with high support values confirmed with Neighbor-Net trees. The pairwise divergences between species in T. albonubes complex were deep and the highly differentiated loci were evenly distributed across the genome. We proposed that the divergence level of T. albonubes complex is at a late stage of cryptic speciation and lacking gene flow. Our findings provide new insights into cryptic speciation and have important implications for conservation and species management of T. albonubes complex.

The impact of habitat loss on molecular signatures of coevolution between an iconic butterfly (Alcon blue) and its host plant (Marsh gentian)

Habitat loss is threatening natural communities worldwide. Small and isolated populations suffer from inbreeding and genetic drift, which jeopardize their long-term survival and adaptive capacities. However, the consequences of habitat loss for reciprocal coevolutionary interactions remain poorly studied. In this study, we investigated the effects of decreasing habitat patch size and connectivity associated with habitat loss on molecular signatures of coevolution in the Alcon blue butterfly (Phengaris alcon) and its most limited host, the marsh gentian (Gentiana pneumonanthe). Because reciprocal coevolution is characterized by negative frequency-dependent selection as a particular type of balancing selection, we investigated how signatures of balancing selection vary along a gradient of patch size and connectivity, using single nucleotide polymorphisms (SNPs). We found that signatures of coevolution were unaffected by patch characteristics in the host plants. On the other hand, more pronounced signatures of coevolution were observed in both spatially isolated and in large Alcon populations, together with pronounced spatial variation in SNPs that are putatively involved in coevolution. These findings suggest that habitat loss can facilitate coevolution in large butterfly populations through limiting swamping of locally beneficial alleles by maladaptive ones. We also found that allelic richness (Ar) of the coevolutionary SNPs is decoupled from neutral Ar in the butterfly, indicating that habitat loss has different effects on coevolutionary as compared with neutral processes. We conclude that this specialized coevolutionary system requires particular conservation interventions aiming at generating a spatial mosaic of both connected and of isolated habitat to maintain coevolutionary dynamics.

Evaluating the genetic consequences of population subdivision as it unfolds and how to best mitigate them: A rare story about koalas

The genetic consequences of the subdivision of populations are regarded as significant to long-term evolution, and research has shown that the scale and speed at which this is now occurring is critically reducing the adaptive potential of most species which inhabit human-impacted landscapes. Here, we provide a rare and, to our knowledge, the first analysis of this process while it is happening and demonstrate a method of evaluating the effect of mitigation measures such as fauna crossings. We did this by using an extensive genetic data set collected from a koala population which was intensely monitored during the construction of linear transport infrastructure which resulted in the subdivision of their population. First, we found that both allelic richness and effective population size decreased through the process of population subdivision. Second, we predicted the extent to which genetic drift could impact genetic diversity over time and showed that after only 10 generations the resulting two subdivided populations could experience between 12% and 69% loss in genetic diversity. Lastly, using forward simulations we estimated that a minimum of eight koalas would need to disperse from each side of the subdivision per generation to maintain genetic connectivity close to zero but that 16 koalas would ensure that both genetic connectivity and diversity remained unchanged. These results have important consequences for the genetic management of species in human-impacted landscapes by showing which genetic metrics are best to identify immediate loss in genetic diversity and how to evaluate the effectiveness of any mitigation measures.

Breeding system and geospatial variation shape the population genetics of Triodanis perfoliata

Both intrinsic and extrinsic forces work together to shape connectivity and genetic variation in populations across the landscape. Here we explored how geography, breeding system traits, and environmental factors influence the population genetic patterns of Triodanis perfoliata, a widespread mix‐mating annual plant in the contiguous US. By integrating population genomic data with spatial analyses and modeling the relationship between a breeding system and genetic diversity, we illustrate the complex ways in which these forces shape genetic variation. Specifically, we used 4705 single nucleotide polymorphisms to assess genetic diversity, structure, and evolutionary history among 18 populations. Populations with more obligately selfing flowers harbored less genetic diversity (π: R² = .63, p = .01, n = 9 populations), and we found significant population structuring (F_ST = 0.48). Both geographic isolation and environmental factors played significant roles in predicting the observed genetic diversity: we found that corridors of suitable environments appear to facilitate gene flow between populations, and that environmental resistance is correlated with increased genetic distance between populations. Last, we integrated our genetic results with species distribution modeling to assess likely patterns of connectivity among our study populations. Our landscape and evolutionary genetic results suggest that T. perfoliata experienced a complex demographic and evolutionary history, particularly in the center of its distribution. As such, there is no singular mechanism driving this species' evolution. Together, our analyses support the hypothesis that the breeding system, geography, and environmental variables shape the patterns of diversity and connectivity of T. perfoliata in the US.

Genetic drift drives rapid speciation of an Arctic insular endemic shrew (Sorex pribilofensis)

Episodes of Quaternary environmental change shaped the genomes of extant species, influencing their response to contemporary environments, which are changing rapidly. Island endemics are among the most vulnerable to such change, accounting for a disproportionate number of recent extinctions. To prevent extinctions and conserve island biodiversity it is vital to combine knowledge of species' ecologies with their complex evolutionary histories. The Bering Sea has a history of cyclical island isolation and reconnection, coupled with modern rates of climate change that exceed global averages. The endangered Pribilof Island shrew (Sorex pribilofensis) is endemic to St. Paul Island, Alaska, which was isolated from mainland Beringia ~14,000 years ago by rising sea levels. Using ~11,000 single nucleotide polymorphisms, 17 microsatellites and mitochondrial sequence data, we test predictions about the evolutionary processes driving shrew speciation across Beringia. Our data show considerable differentiation of S. pribilofensis from mainland sibling species, relative to levels of divergence between mainland shrews. We also find a genome-wide loss of diversity and extremely low N_e for S. pribilofensis. We then show that intraspecific genetic diversity is significantly related to interspecific divergence, and that differentiation between S. pribilofensis and other Beringian shrews is highest across loci that are fixed in S. pribilofensis, indicating that strong drift has driven differentiation of this island species. Our findings show that drift as a consequence of Arctic climate cycling can rapidly reshape insular biodiversity. Arctic island species that lack genomic diversity and have evolved in response to past climate may have limited ability to respond to modern environmental changes.

Genetic differentiation that is exceptionally high and unexpectedly sensitive to geographic distance in the absence of gene flow: Insights from the genus Eranthis in East Asian regions

Genetic differentiation between populations is determined by various factors, including gene flow, selection, mutation, and genetic drift. Among these, gene flow is known to counter genetic differentiation. The genus Eranthis, an early flowering perennial herb, can serve as a good model to study genetic differentiation and gene flow due to its easily detectable population characteristics and known reproductive strategies, which can be associated with gene flow patterns. Eranthis populations are typically small and geographically separated from the others. Moreover, previous studies and our own observations suggest that seed and pollen dispersal between Eranthis populations is highly unlikely and therefore, currently, gene flow may not be probable in this genus. Based on these premises, we hypothesized that the genetic differentiation between the Eranthis populations would be significant, and that the genetic differentiation would not sensitively reflect geographic distance in the absence of gene flow. To test these hypotheses, genetic differentiation, genetic distance, isolation by distance, historical gene flow, and bottlenecks were analyzed in four species of this genus. Genetic differentiation was significantly high, and in many cases, extremely high. Moreover, genetic differentiation and geographic distance were positively correlated in most cases. We provide possible explanations for these observations. First, we suggest that the combination of the marker type used in our study (chloroplast microsatellites), genetic drift, and possibly selection might have resulted in the extremely high genetic differentiation observed herein. Additionally, we provide the possibility that genetic distance reflects geographic distance through historical gene flow, or adaptation in the absence of historical gene flow. Nevertheless, our explanations can be more rigorously examined and further refined through additional observations and various population genetic analyses. In particular, we suggest that other accessible populations of the genus Eranthis should be included in future studies to better characterize the intriguing population dynamics of this genus.

The impact of urbanization on outcrossing rate and population genetic variation in the native wildflower, Impatiens capensis

Cities are one of the fastest growing ecosystems on the planet, and conserving urban biodiversity is of primary importance. Urbanization increases habitat fragmentation and may be particularly problematic for native plant species which often exist in small, remnant populations in cities. We studied the effects of urbanization on Impatiens capensis, a self-compatible native wildflower, which is an important nectar and pollen source for native bees and hummingbirds. We sampled I. capensis from six populations located in urban and rural habitats in Toronto, Ontario, Canada. We sequenced the DNA of 43 families (N = 86 individuals) using genotype-by-sequencing to obtain 5627 single nucleotide polymorphisms. From each parent and offspring, we estimated individual outcrossing rates, population-level genetic diversity and genetic structure among populations. We found that 95% of plants were outcrossed, and populations were genetically differentiated, where urban populations contained a subset of the genetic variation found in rural populations. Urban populations exhibited lower genetic diversity than rural populations, and we detected a relationship between population census size and habitat on genetic diversity. Despite high outcrossing rates, our results suggest that urbanization reduces the genetic diversity of I. capensis populations, potentially increasing the vulnerability of these populations to long-term population declines and extirpation in response to urbanization.

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

PREMISE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

One Step Away From Extinction: A Population Genomic Analysis of A Narrow Endemic, Tropical Plant Species

Intraspecific genetic variation plays a fundamental role in maintaining the evolutionary potential of wild populations. Hence, the assessment of genetic diversity patterns becomes essential to guide biodiversity conservation policies, particularly for threatened species. To inform management strategies for conservation of Mimosa catharinensis - a narrow endemic, critically endangered plant species - we identified 1,497 unlinked SNP markers derived from a reduced representation sequencing method (i.e., double digest restriction site associated DNA sequencing, or ddRADseq). This set of molecular markers was employed to assess intrapopulation genetic parameters and the demographic history of one extremely small population of M. catharinensis (N=33) located in the Brazilian Atlantic Forest. Contrary to what is expected for narrow endemic and threatened species with small population sizes, we observed a moderate level of genetic diversity for M. catharinensis [uH E(0%missing data)=0.205, 95% CI (0.160, 0.250); uH E(30%missing data)=0.233, 95% CI (0.174, 0.292)]. Interestingly, M. catharinensis, which is a lianescent shrub with no indication of seed production for at least two decades, presented high levels of outcrossing [t (0%missing data)=0.883, SE±0.0483; t (30%missing data)=0.909, SE±0.011] and an apparent absence of inbreeding [F (0%missing data)=-0.145, 95% CI (-0.189, -0.101); F (30%missing data)=-0.105, 95% CI (-0.199, -0.011)]. However, the reconstruction of demographic history of M. catharinensis indicated that the population should be suffered a recent bottleneck. Our population genomic study tackles a central issue in evolution and conservation biology and we expect that it will be useful to help safeguard the remaining genetic diversity reported for this unique genetic resource.

Spatial and Ecological Drivers of Genetic Structure in Greek Populations of Alkanna tinctoria (Boraginaceae), a Polyploid Medicinal Herb

Background and Aims: Quantifying genetic variation is fundamental to understand a species' demographic trajectory and its ability to adapt to future changes. In comparison with diploids, however, genetic variation and factors fostering genetic divergence remain poorly studied in polyploids due to analytical challenges. Here, by employing a ploidy-aware framework, we investigated the genetic structure and its determinants in polyploid Alkanna tinctoria (Boraginaceae), an ancient medicinal herb that is the source of bioactive compounds known as alkannin and shikonin (A/S). From a practical perspective, such investigation can inform biodiversity management strategies. Methods: We collected 14 populations of A. tinctoria within its main distribution range in Greece and genotyped them using restriction site-associated DNA sequencing. In addition, we included two populations of A. sieberi. By using a ploidy-aware genotype calling based on likelihoods, we generated a dataset of 16,107 high-quality SNPs. Classical and model-based analysis was done to characterize the genetic structure within and between the sampled populations, complemented by genome size measurements and chromosomal counts. Finally, to reveal the drivers of genetic structure, we searched for associations between allele frequencies and spatial and climatic variables. Key Results: We found support for a marked regional structure in A. tinctoria along a latitudinal gradient in line with phytogeographic divisions. Several analyses identified interspecific admixture affecting both mainland and island populations. Modeling of spatial and climatic variables further demonstrated a larger contribution of neutral processes and a lesser albeit significant role of selection in shaping the observed genetic structure in A. tinctoria. Conclusion: Current findings provide evidence of strong genetic structure in A. tinctoria mainly driven by neutral processes. The revealed natural genomic variation in Greek Alkanna can be used to further predict variation in A/S production, whereas our bioinformatics approach should prove useful for the study of other non-model polyploid species.

Population genetic structure and connectivity of a riparian selfing herb Caulokaempferia coenobialis at a fine-scale geographic level in subtropical monsoon forest

BACKGROUND

Rivers and streams facilitate movement of individuals and their genes across the landscape and are generally recognized as dispersal corridors for riparian plants. Nevertheless, some authors have reported directly contrasting results, which may be attributed to a complex mixture of factors, such as the mating system and dispersal mechanisms of propagules (seed and pollen), that make it difficult to predict the genetic diversity and population structure of riparian species. Here, we investigated a riparian self-fertilizing herb Caulokaempferia coenobialis, which does not use anemochory or zoochory for seed dispersal; such studies could contribute to an improved understanding of the effect of rivers or streams on population genetic diversity and structure in riparian plants. Using polymorphic ISSR and cpDNA loci, we studied the effect at a microgeographic scale of different stream systems (a linear stream, a dendritic stream, and complex transverse hydrological system) in subtropical monsoon forest on the genetic structure and connectivity of C. coenobialis populations across Dinghu Mountain (DH) and Nankun Mountain (NK).

RESULTS

The results indicate that the most recent haplotypes (DH: H7, H8; NK: h6, h7, h11, h12) are not shared among local populations of C. coenobialis within each stream system. Furthermore, downstream local populations do not accumulate genetic diversity, whether in the linear streamside local populations across DH (H: 0.091 vs 0.136) or the dendritic streamside local populations across NK (H: 0.079 vs 0.112, 0.110). Our results show that the connectivity of local C. coenobialis populations across DH and NK can be attributed to historical gene flows, resulting in a lack of spatial genetic structure, despite self-fertilization. Selfing C. coenobialis can maintain high genetic diversity (H = 0.251; I = 0.382) through genetic differentiation (GST = 0.5915; FST = 0.663), which is intensified by local adaptation and neutral mutation and/or genetic drift in local populations at a microgeographic scale.

CONCLUSION

We suggest that streams are not acting as corridors for dispersal of C. coenobialis, and conservation strategies for maintaining genetic diversity of selfing species should be focused on the protection of all habitat types, especially isolated fragments in ecosystem processes.

Charting a course for genetic diversity in the UN Decade of Ocean Science

The health of the world's oceans is intrinsically linked to the biodiversity of the ecosystems they sustain. The importance of protecting and maintaining ocean biodiversity has been affirmed through the setting of the UN Sustainable Development Goal 14 to conserve and sustainably use the ocean for society's continuing needs. The decade beginning 2021-2030 has additionally been declared as the UN Decade of Ocean Science for Sustainable Development. This program aims to maximize the benefits of ocean science to the management, conservation, and sustainable development of the marine environment by facilitating communication and cooperation at the science-policy interface. A central principle of the program is the conservation of species and ecosystem components of biodiversity. However, a significant omission from the draft version of the Decade of Ocean Science Implementation Plan is the acknowledgment of the importance of monitoring and maintaining genetic biodiversity within species. In this paper, we emphasize the importance of genetic diversity to adaptive capacity, evolutionary potential, community function, and resilience within populations, as well as highlighting some of the major threats to genetic diversity in the marine environment from direct human impacts and the effects of global climate change. We then highlight the significance of ocean genetic diversity to a diverse range of socioeconomic factors in the marine environment, including marine industries, welfare and leisure pursuits, coastal communities, and wider society. Genetic biodiversity in the ocean, and its monitoring and maintenance, is then discussed with respect to its integral role in the successful realization of the 2030 vision for the Decade of Ocean Science. Finally, we suggest how ocean genetic diversity might be better integrated into biodiversity management practices through the continued interaction between environmental managers and scientists, as well as through key leverage points in industry requirements for Blue Capital financing and social responsibility.

Type and intensity of surrounding human land use, not local environment, shape genetic structure of a native grassland plant

Landscape heterogeneity can shape genetic structure and functional connectivity of populations. When this heterogeneity imposes variable costs of moving across the landscape, populations can be structured according to a pattern of "isolation by resistance" (IBR). At the same time, divergent local environmental filters can limit gene flow, creating an alternative pattern of "isolation by environment" (IBE). Here, we evaluate IBR and IBE in the insect-pollinated, biennial plant Sabatia angularis (L.) Pursh (Gentianaceae) across serpentine grasslands in the fragmented landscape of SE Pennsylvania, USA using ~4500 neutral SNP loci. Specifically, we test the extent to which radical alteration of the landscape matrix by humans has fundamentally altered the cost of movement, imprinting a pattern of IBR dictated by land use type and intensity, and the potential for IBE in relation to a gradient of heavy metal concentrations found in serpentine soil. We reveal a strong signal of IBR and a weak signal of IBE across sites, indicating the greater importance of the landscape matrix in shaping genetic structure of S. angularis populations in the study region. Based on Circuitscape and least cost path approaches, we find that both low- and high-intensity urbanization resist gene flow by orders of magnitude greater than "natural" habitats, although resistance to low-intensity urbanization weakens at larger spatial scales. While cropland presents a substantially lower barrier than urban development, cumulative human land use surrounding populations predicts within-population genetic diversity and inbreeding in S. angularis. Our results emphasize the role of forest buffers and corridors in facilitating gene flow between serpentine grassland patches and averting local extinction of plant populations.

Urbanization reduces gene flow but not genetic diversity of stream salamander populations in the New York City metropolitan area

Natural landscape heterogeneity and barriers resulting from urbanization can reduce genetic connectivity between populations. The evolutionary, demographic, and ecological effects of reduced connectivity may lead to population isolation and ultimately extinction. Alteration to the terrestrial and aquatic environment caused by urban influence can affect gene flow, specifically for stream salamanders who depend on both landscapes for survival and reproduction. To examine how urbanization affects a relatively common stream salamander species, we compared genetic connectivity of Eurycea bislineata (northern two-lined salamander) populations within and between streams in an urban, suburban, and rural habitat around the New York City (NYC) metropolitan area. We report reduced genetic connectivity between streams within the urban landscape found to correspond with potential barriers to gene flow, that is, areas with more dense urbanization (roadways, industrial buildings, and residential housing). The suburban populations also exhibited areas of reduced connectivity correlated with areas of greater human land use and greater connectivity within a preserve protected from development. Connectivity was relatively high among neighboring rural streams, but a major roadway corresponded with genetic breaks even though the habitat contained more connected green space overall. Despite greater human disturbance across the landscape, urban and suburban salamander populations maintained comparable levels of genetic diversity to their rural counterparts. Yet small effective population size in the urban habitats yielded a high probability of loss of heterozygosity due to genetic drift in the future. In conclusion, urbanization impacted connectivity among stream salamander populations where its continual influence may eventually hinder population persistence for this native species in urban habitats.

Genetic differentiation between two varieties of Oreocharis benthamii (Gesneriaceae) in sympatric and allopatric regions

The pattern of genetic differentiation between diverging species receives much attention as one of the key observable features of speciation. It has often been suggested that introgression between closely related species occurs commonly where their distributions overlap, leading to their becoming more morphologically and genetically similar, but there are a few opposite results. However, most of these studies have been carried out with animals and separate species; few have looked at intraspecific cases, especially in plants. Here, we conduct a comparative study on patterns of genetic differentiation among populations of two varieties of Oreocharis benthamii in allopatry and sympatry based on ISSR data for 754 individuals from 26 populations, in order to understand the processes leading to speciation. Contrary to expectations, the facultative xenogamy (mixed mating) species O. benthamii has a relatively low genetic diversity within populations (H = 0.1014, I = 0.1528) and high genetic differentiation among populations (G ST = 0.5867, ФST = 0.659), as is typically found for selfing species. Genetic variance between the two varieties in sympatric populations (44%, ФST = 0.444) is significantly more than that in allopatric populations (14%, ФST = 0.138). Consistent with the taxonomical delimitation of the two varieties, all sampled individuals of O. benthamii clustered into two genetic groups. Moreover, the genetic structures of populations of both varieties are correlated with their different geographical origins. Our studies show that significant divergence between sympatric populations of the two varieties could be attributed primarily to reinforcement by genetic divergent selection in sympatry where secondary contact had occurred. The major proportion of the genetic variation in outcrossing and mixed mating plants may exist among populations when the populations are distributed in fragmented habitats, due to the paucity of suitable habitat combined with inefficient seed dispersal mechanism and limited pollinator foraging area that may limit the gene flow.

The boon and bane of boldness: movement syndrome as saviour and sink for population genetic diversity

BACKGROUND

Many felid species are of high conservation concern, and with increasing human disturbance the situation is worsening. Small isolated populations are at risk of genetic impoverishment decreasing within-species biodiversity. Movement is known to be a key behavioural trait that shapes both demographic and genetic dynamics and affects population survival. However, we have limited knowledge on how different manifestations of movement behaviour translate to population processes. In this study, we aimed to 1) understand the potential effects of movement behaviour on the genetic diversity of small felid populations in heterogeneous landscapes, while 2) presenting a simulation tool that can help inform conservation practitioners following, or considering, population management actions targeting the risk of genetic impoverishment.

METHODS

We developed a spatially explicit individual-based population model including neutral genetic markers for felids and applied this to the example of Eurasian lynx. Using a neutral landscape approach, we simulated reintroductions into a three-patch system, comprising two breeding patches separated by a larger patch of differing landscape heterogeneity, and tested for the effects of various behavioural movement syndromes and founder population sizes. We explored a range of movement syndromes by simulating populations with various movement model parametrisations that range from 'shy' to 'bold' movement behaviour.

RESULTS

We find that movement syndromes can lead to a higher loss of genetic diversity and an increase in between population genetic structure for both "bold" and "shy" movement behaviours, depending on landscape conditions, with larger decreases in genetic diversity and larger increases in genetic differentiation associated with bold movement syndromes, where the first colonisers quickly reproduce and subsequently dominate the gene pool. In addition, we underline the fact that a larger founder population can offset the genetic losses associated with subpopulation isolation and gene pool dominance.

CONCLUSIONS

We identified a movement syndrome trade-off for population genetic variation, whereby bold-explorers could be saviours - by connecting populations and promoting panmixia, or sinks - by increasing genetic losses via a 'founder takes all' effect, whereas shy-stayers maintain a more gradual genetic drift due to their more cautious behaviour. Simulations should incorporate movement behaviour to provide better projections of long-term population viability and within-species biodiversity, which includes genetic diversity. Simulations incorporating demographics and genetics have great potential for informing conservation management actions, such as population reintroductions or reinforcements. Here, we present such a simulation tool for solitary felids.

Using genomic information for management planning of an endangered perennial, Viola uliginosa

Species occupying habitats subjected to frequent natural and/or anthropogenic changes are a challenge for conservation management. We studied one such species, Viola uliginosa, an endangered perennial wetland species typically inhabiting sporadically flooded meadows alongside rivers/lakes. In order to estimate genomic diversity, population structure, and history, we sampled five sites in Finland, three in Estonia, and one each in Slovenia, Belarus, and Poland using genomic SNP data with double-digest restriction site-associated DNA sequencing (ddRAD-seq). We found monophyletic populations, high levels of inbreeding (mean population F SNP = 0.407-0.945), low effective population sizes (N e = 0.8-50.9), indications of past demographic expansion, and rare long-distance dispersal. Our results are important in implementing conservation strategies for V. uliginosa, which should include founding of seed banks, ex situ cultivations, and reintroductions with individuals of proper origin, combined with continuous population monitoring and habitat management.

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.

Genomic variation predicts adaptive evolutionary responses better than population bottleneck history

The relationship between population size, inbreeding, loss of genetic variation and evolutionary potential of fitness traits is still unresolved, and large-scale empirical studies testing theoretical expectations are surprisingly scarce. Here we present a highly replicated experimental evolution setup with 120 lines of Drosophila melanogaster having experienced inbreeding caused by low population size for a variable number of generations. Genetic variation in inbred lines and in outbred control lines was assessed by genotyping-by-sequencing (GBS) of pooled samples consisting of 15 males per line. All lines were reared on a novel stressful medium for 10 generations during which body mass, productivity, and extinctions were scored in each generation. In addition, we investigated egg-to-adult viability in the benign and the stressful environments before and after rearing at the stressful conditions for 10 generations. We found strong positive correlations between levels of genetic variation and evolutionary response in all investigated traits, and showed that genomic variation was more informative in predicting evolutionary responses than population history reflected by expected inbreeding levels. We also found that lines with lower genetic diversity were at greater risk of extinction. For viability, the results suggested a trade-off in the costs of adapting to the stressful environments when tested in a benign environment. This work presents convincing support for long-standing evolutionary theory, and it provides novel insights into the association between genetic variation and evolutionary capacity in a gradient of diversity rather than dichotomous inbred/outbred groups.