Immediate and longer-term effects of managed flooding on floodplain invertebrate assemblages in south-eastern Australia: generation and maintenance of a mosaic landscape

1. We compared assemblages of ground‐active, terrestrial beetles and spiders from different areas of river red gum Eucalyptus camaldulensis floodplain forest in subhumid, south‐eastern Australia before and for 2 years following a managed flood to determine whether the Flood Pulse Concept is an appropriate ecological model for this regulated, lowland river‐floodplain system. 2. Immediately following flooding, the abundance, species richness and biomass of beetles were greatest at sites that had been inundated for the longest period (approximately 4 months). The abundance, species richness and biomass of spiders were not reduced at sites that were flooded for 4 months compared with unflooded or briefly flooded areas. Sites recently flooded for several months had high densities of predatory, hygrophilic beetles (Carabidae) and spiders (Lycosidae). 3. Over the 2 years following the flood, beetles generally were more abundant at sites that had been inundated for longer. At all sampling times, the species richness of beetles at sites increased with the length of time sites were inundated, even before the flood. Neither the abundance nor species richness of spiders was related to duration of flooding. 4. The structure of beetle and spider assemblages at sites that were flooded for different lengths of time did not appear to converge monotonically over the 2 years after the flood. 5. Managed flooding promotes diversity of beetles and spiders both by providing conditions that create a ‘pulse’ in populations of hygrophilic specialists in the short term, and by creating subtle, persistent changes in forest‐floor conditions. Despite its monotypic canopy, river red gum floodplain forest is a habitat mosaic generated by differing inundation histories.     

Genetic variation and bidirectional gene flow in the riparian plant Miscanthus lutarioriparius,across its endemic range: implications for adaptive potential

Miscanthus lutarioriparius is an endemic species that grows along the middle and lower reaches of the Yangtze River and is a valuable source of germplasm for the development of second‐generation energy crops. The plant that propagates via seeds, stem nodes, and rhizomes shows high phenotypic variation and strong local adaptation. Here, we examined the magnitude and spatial distribution of genetic variation in M. lutarioriparius across its entire distributional range and tested underlying factors that shaped its genetic variation. Population genetic analyses were conducted on 644 individuals from 25 populations using 16 microsatellite markers. M. lutarioriparius exhibited a high level of genetic variation (H_E = 0.682–0.786; A_r = 4.74–8.06) and a low differentiation (F_ST = 0.063; D_est = 0.153). Of the total genetic variation, 10% was attributed to the differences among populations (df = 24, P < 0.0001), whereas 90% was attributed to the differences among individuals (df = 619, P ≤ 0.0001). Genetic diversity did not differ significantly across longitudes and did not increase in the populations growing downstream of the Yangtze River. However, significant associations were found between genetic differentiation and spatial distance. Six genetic discontinuities were identified, which mostly distributed among downstream populations. We conclude that anthropogenic factors and landscape features both contributed to shaping the pattern of gene flow in M. lutarioriparius, including long‐distance bidirectional dispersal. Our results explain the genetic basis of the high degree of adaptability in M. lutarioriparius and identify potential sources of new germplasm for the domestication of this potential second‐generation energy crop.     

汶川地震区灾后植被恢复时空过程及特征——以都江堰龙溪河流域为例

定量评估地震区灾后植被恢复,对于灾区生态系统恢复重建及区域社会经济可持续发展规划具有重要科学意义.以都江堰龙溪河流域为案例区,采用MODIS-NDVI的时间序列数据,确定植被恢复评估的Landsat影像时间,并以Landsat影像定量揭示龙溪河流域植被在“5.12”汶川地震前后的动态变化;进而根据区域水系和地形因子,定量解析并揭示植被覆盖度受损恢复率的时空变化特征.结果表明:研究区植被覆盖受损恢复情况整体较好,但植被覆盖度对地震损害的响应存在滞后现象;受损植被恢复率与河流水系距离、海拔、坡度和坡向存在显著的相关性.本研究结果可为地震灾后植被恢复的决策干预提供技术支撑.     

The ecology of Helicoverpa spp. (Lepidoptera: Noctuidae) in the Riverina region of south-eastern Australia and the implications for tactical and strategic management

Decisions on the choice of appropriate tactical and strategic control techniques require an understanding of the seasonal distribution and ecology of the target species. To address this need, data were collected from 1997 to 2000 using crop surveys, field sampling and pheromone trapping to monitor the population trends of Helicoverpa armigera (Hübner) and H. punctigera (Wallengren) in the Riverina region of south-eastern Australia. The data gathered are compared to predictions from the HElicoverpa Armigera and Punctigera Simulation (HEAPS) model, that simulates Helicoverpa population dynamics to assist in identifying the drivers of regional populations and provide a framework to make informed decisions. The results highlight the contrasting seasonal dynamics of H. punctigera and H. armigera within the region. Helicoverpa punctigera populations peak in the spring, driven by large scale spring migration into the region and subsequently decline. Helicoverpa armigera populations, conversely, are characterized by a period of spring recruitment of adults from overwintering pupae within the region, followed by a within-season population increase leading to severe late season pressure. The within-season increase of H. armigera is a result of the succession of crop and non-crop hosts with the main driver being sequentially sown, unsprayed maize. Tactical and strategic management options are discussed in light of these findings.     

Habitat structure is more important than vegetation composition for local‐level management of native terrestrial reptile and small mammal species living in urban remnants: A case study from Brisbane,Australia

Abstract As urban areas continue to expand and replace natural and agricultural landscapes, the ability to manage and conserve native wildlife within urban environments is becoming increasingly important. To do so we first need to understand species' responses to local‐level habitat attributes in order to inform the decision‐making process and on‐ground conservation actions. Patterns in the occurrence of native terrestrial reptile and small mammal species in 59 sites located in remnant urban habitat fragments of Brisbane City were assessed against local‐level environmental characteristics of each site. Cluster analysis, multidimensional scaling ordination, and principal axis correlation were used to investigate relationships between species' occurrences and environmental characteristics. Native reptiles were most strongly associated with the presence of termite mounds, a high amount of fallen woody material, and a moderate amount of weed cover. Native small mammals were most strongly associated with the presence of grass trees (Xanthorrhoea spp.), and both reptiles and small mammals were negatively influenced by increased soil compaction. Significant floristic characteristics were considered to be important as structural, rather than compositional, habitat elements. Therefore, habitat structure, rather than vegetation composition, appears to be most important for determining native, terrestrial reptile and small mammal species assemblages in urban forest fragments. We discuss the management implications in relation to human disturbances and local‐level management of urban remnants.     

Evaluation of the risk of overwintering Helicoverpa spp. pupae under irrigated summer crops in south-eastern Australia and the potential for area-wide management

Surveys were undertaken to determine the distribution of overwintering pupae of two species of Helicoverpa in south‐eastern Australia. The results indicate that significant populations of H. armigera have the potential to overwinter as pupae in the region under residues of their summer crop hosts. H. punctigera, conversely, was found not to overwinter in the region to any significant degree. The results also suggest that a high proportion of the overwintering H. armigera population are located in relatively few high risk fields. The overwintering population represents an ideal opportunity for control on an area‐wide basis using post harvest cultivation or “pupae busting”. The risk of overwintering H. armigera pupae occurring was largely associated with crop type, the mechanism being related to the date that the crop flowers, the level of pupal parasitism and the use of larval control measures. The results are discussed in terms of recommendations for farmers and it is suggested that a concerted effort to cultivate high risk fields has the potential to significantly reduce the population on an area‐wide basis.     

Formation and maintenance of discrete wild rabbit (Oryctolagus cuniculus) population systems in arid Australia: Habitat heterogeneity and management implications

Abstract The wild rabbit (Oryctolagus cuniculus L.) is a significant pest in arid and semi‐arid Australia, where erratic rainfall and irregular pasture growth cause population sizes to oscillate, increasing virtually without limit and then crashing during drought conditions. Vacant habitat patches can be rapidly recolonized from nearby patches in high rainfall years. Using two adjoining rabbit population systems in arid and semi‐arid south‐west Queensland, this study evaluates patterns of population differentiation and proposes a mechanism that may lead to the formation of multiple rabbit population systems in the same locality. Using the combined haplotype frequency data from both a local and regional study, estimates of genetic exchange among local populations are considered in conjunction with ecological data to evaluate the significance of habitat attributes (and their spatial distribution) on the local distribution of rabbit populations, both within and between two adjacent population systems. A tentative model is proposed to explain the observed differences in population structure between the two adjoining systems. Under this model, population structure at specific locations is determined primarily by the availability of areas suitable for prolonged colonization and the quality of the intervening habitat that dictates the degree of isolation between locations and therefore the probability of recolonization following local extinctions. It is also suggested that the current rabbit distribution may be a function of the flexibility of behavioural responses in rabbits to the level of spatial heterogeneity of favourable habitats within the two regions.     

A synthesis of genetic connectivity in deep‐sea fauna and implications for marine reserve design

With anthropogenic impacts rapidly advancing into deeper waters, there is growing interest in establishing deep‐sea marine protected areas (MPAs) or reserves. Reserve design depends on estimates of connectivity and scales of dispersal for the taxa of interest. Deep‐sea taxa are hypothesized to disperse greater distances than shallow‐water taxa, which implies that reserves would need to be larger in size and networks could be more widely spaced; however, this paradigm has not been tested. We compiled population genetic studies of deep‐sea fauna and estimated dispersal distances for 51 studies using a method based on isolation‐by‐distance slopes. Estimates of dispersal distance ranged from 0.24 km to 2028 km with a geometric mean of 33.2 km and differed in relation to taxonomic and life‐history factors as well as several study parameters. Dispersal distances were generally greater for fishes than invertebrates with the Mollusca being the least dispersive sampled phylum. Species that are pelagic as adults were more dispersive than those with sessile or sedentary lifestyles. Benthic species from soft‐substrate habitats were generally less dispersive than species from hard substrate, demersal or pelagic habitats. As expected, species with pelagic and/or feeding (planktotrophic) larvae were more dispersive than other larval types. Many of these comparisons were confounded by taxonomic or other life‐history differences (e.g. fishes being more dispersive than invertebrates) making any simple interpretation difficult. Our results provide the first rough estimate of the range of dispersal distances in the deep sea and allow comparisons to shallow‐water assemblages. Overall, dispersal distances were greater for deeper taxa, although the differences were not large (0.3–0.6 orders of magnitude between means), and imbalanced sampling of shallow and deep taxa complicates any simple interpretation. Our analyses suggest the scales of dispersal and connectivity for reserve design in the deep sea might be comparable to or slightly larger than those in shallow water. Deep‐sea reserve design will need to consider the enormous variety of taxa, life histories, hydrodynamics, spatial configuration of habitats and patterns of species distributions. The many caveats of our analyses provide a strong impetus for substantial future efforts to assess connectivity of deep‐sea species from a variety of habitats, taxonomic groups and depth zones.     

Factors associated with suni distribution in Tembe Elephant Park,South Africa: implications for management and conservation of a small antelope

While small antelopes are becoming increasingly threatened, knowledge of their biology is often limited. Management recommendations are therefore frequently based on insufficient information. One of the declining small antelopes is the suni in South Africa. A reduction in sand forests as well as habitat destruction by increased nyala populations are the suggested causes of suni declines. However, no recent study has quantified the factors that underlie suni distribution in southern Africa. Here we investigate whether the vegetation types, vegetation structures or occurrences of sympatric browsers affect suni distribution within Tembe Elephant Park, South Africa. We found that vegetation type and vegetation structure interacted in their effects on suni distribution, but there were no effects of sympatric browsers. Suni were found most often in the sand forests, but were also present in closed woodland. Vegetation structure was, however, related to the local distribution of suni only in sand forest. This highlights that suni are not exclusively bound to sand forest, and also that the vegetation structure within the sand forest may be as important as the vegetation type. We suggest that the current conservation assessment of this subspecies is based on insufficient data, and that a more detailed assessment of their distribution and the factors that determine the same is critically needed.     

Australia’s Stock Route Network: 1. A review of its values and implications for future management

Summary The Stock Route Network (SRN) is a vast system of public land, comprising vegetated strips and small reserves across the eastern length of the Australian continent. Now predominantly following the road system, this network was historically established to allow for the movement of livestock prior to truck and railway transport. Owing to declines in traditional uses, parts of the SRN may now be sold to private landholders, or put under long‐term grazing leases, making them unavailable for other emerging uses. This is in spite of the fact that it is widely accepted by researchers, practitioners, graziers and agriculturalists that the SRN holds great natural and cultural value. We conducted a review of scientific and grey literature to determine the known values of the network for biodiversity conservation, cultural heritage, rural communities and Australian society as a whole. We found that the majority of existing literature on the network focuses on New South Wales (NSW) and is of a conservation‐based nature. The Stock Route Network supports a wide range of threatened species and communities, with considerable potential for many more to be discovered. The network also holds heritage value for both Indigenous and non‐Indigenous Australians. The societal benefits from the SRN are numerous because it provides land for recreation and apiary sites, a source of seed for revegetation projects, a focus for rural tourism, as well as the traditional benefits for stock droving and emergency agistment. In the light of our review, we identified key knowledge gaps pertaining to the values of the SRN and propose a number of options for its future management. Appropriate governance and increased investment in SRN management is now urgently required to ensure that it continues to conserve its many environmental and social values in perpetuity.     

面向连通性提升的旱区城市生态网络优化情景——以巴彦淖尔市及其周边地区为例

巴彦淖尔市作为典型的干旱区城市,经济发展与生态保护之间的矛盾突出,生态空间的破碎化日益严重。生态网络是景观连通性视角下耦合景观结构、生态过程和功能的有效途径。基于生态系统服务重要性、景观核心区与桥接区、自然保护区、重要湖泊湿地4个层面指标选取生态源地,使用最小耗费距离方法识别巴彦淖尔市及其周边区域的潜在生态网络,并设置了3种网络优化情景进行网络优化,包括情景一增加生态"踏脚石"、情景二清除生态障碍点、情景三保护生态夹点,结合"网络构建成本"及"生境连通效果"选取最佳优化方案。结果表明,研究区当前的生态网络由24处生态源地,44条生态廊道、39个生态障碍点和41个生态夹点组成。3种情景中生态夹点的保护对生态网络连通度的改善最明显,且相对保护成本较低。研究结果对干旱区城市生态网络构建提供了方法支撑。     

Spatio‐temporal patterns of genetic variations in populations of yellowtail kingfish Seriola lalandi from the south‐eastern Pacific Ocean and potential implications for its fishery management

The genetic population structure and genetic diversity of yellowtail kingfish Seriola lalandi from the coastal south‐eastern Pacific Ocean (SEP) were evaluated at spatiotemporal scale in order to understand the ecology of this species. Between 2012 and 2015, temporal and spatial population genetic structure and a low genetic diversity were detected in S. lalandi from SEP. These results suggest that S. lalandi specimens arriving annually from offshore to the SEP coast could come from at least two genetically distinct populations, revealing a particular life strategy (i.e. reproductive or habitat segregation) for this fish species. Therefore, the SEP coast might constitute a point of population mixing for this species. Additionally, the low genetic diversity of S. lalandi in the SEP could be a result of a founder effect or overfishing. Regardless of the process explaining the genetic diversity and structure of S. lalandi in this geographical area, this new information should be considered in order to implement successful fishery management of this resource in the South Pacific.     

A computational approach to ecological and economic sustainable harvest management strategies in a multi-species context, with implications for cod recovery plans

Multi-species models consider interactions, particularly predation, between and within species. Traditional harvest management strategies, such as maximum sustainable yield do not account for these interactions. The exploitation of a single species can be maximised, but this does not mean that the entire ecosystem is being harvested sustainably or at its economic maximum. I present a computational technique (evolutionary algorithms) that can simultaneously optimise harvest management strategies of many species and can easily be modified to allow for factors such as stock recovery, sustainable yields or maximum levels of economic sustainable exploitation. I demonstrate that in an ecologically sustainably managed system where a stock is recovering, maximum economic yield is identical to the maximisation of yield by mass. These findings may have important implications for long term conservation aims and long term profits by fishers.     

Diversity and distribution of the Italian Aesculapian snake Zamenis lineatus: A phylogeographic assessment with implications for conservation

Geographic range size and genetic diversity are key correlates of extinction risk and evolutionary potential of a species, with species occupying smaller geographic ranges and showing limited genetic diversity assumed to be more threatened by environmental changes. The Italian Aesculapian snake Zamenis lineatus is a narrow‐range endemic of southern Italy and Sicily, once considered as part of the widespread species Z. longissimus. To date, we still lack comprehensive data on geographic range and intraspecific diversity of Z. lineatus. In this study, we analysed 106 Aesculapian snakes across the Italian Peninsula and Sicily in order to define the genetic diversity and distribution range of Z. lineatus, its possible range overlap with Z. longissimus and to assess whether hybridization occurs at the species’ range boundaries. We combined genetic data from mitochondrial and nuclear DNA markers with phenotypic data suitable for taxonomic identification. The observed phylogeographic pattern of Z. lineatus suggests: (i) a reduced peninsular range size, about a half of what is currently considered; (ii) limited genetic diversity and weak population structure; (iii) the occurrence of pervasive introgressive hybridization with Z. longissimus in the eastern contact zone. Together, results from this study indicate a higher extinction risk for Z. lineatus than previously appreciated and provide directions for future studies on the hybridization at the contact zone(s) between Z. lineatus and Z. longissimus.     

Morphological and genetic differentiation in populations of the dispersal‐limited coco de mer (Lodoicea maldivica): implications for management and conservation

Aims Developing plant conservation strategies requires knowledge of ecological and genetic processes underlying population dynamics. We aimed to quantify morphological and genetic differentiation among remnant populations of the iconic coco‐de‐mer palm Lodoicea maldivica. We hypothesized that limited gene flow among widely spaced populations would result in high genetic variation and large phenotypic differences among populations. Location Islands of Praslin and Curieuse (CU), Seychelles, Indian Ocean. Methods We conducted an extensive population survey and recorded morphological parameters for 447 Lodoicea in the main populations at Vallée de Mai (VM) and Fond Ferdinand (FF) on Praslin, and on CU. We collected leaf material from 180 trees in these populations for DNA genotyping using amplified fragment length polymorphisms. Results A total of 16,766 Lodoicea trees were recorded in the three populations (72.6% of Lodoicea on both islands). Lodoicea trees at VM and FF showed similar morphology, but differed in most parameters from those at CU, which were shorter, grew more slowly and produced fewer seeds. Mean overall genetic diversity was 0.337, and percentage of polymorphic loci was 91.1. Genetic diversity of the CU population was lower than that at VM and FF. There was weak genetic differentiation between CU and Praslin populations, but 99% of all genetic diversity was within populations. Main conclusions Trees on CU differed in growth and morphology from those of the two Praslin populations. These phenotypic differences, however, were not mirrored in the genetic structure of the populations. All populations were relatively genetically diverse with remarkably little differentiation among populations. This suggests that the capacity of Lodoicea to dominate across a range of habitats may be because of high phenotypic plasticity. High genetic connectivity may be maintained through long‐distance wind pollination. Given the uncertainty about the extent of underlying adaptive variation, we recommend that restoration projects avoid transferring seeds between island populations.     

A climate change context for the decline of a foundation tree species in south-western Australia: insights from phylogeography and species distribution modelling

Background and Aims A worldwide increase in tree decline and mortality has been linked to climate change and, where these represent foundation species, this can have important implications for ecosystem functions. This study tests a combined approach of phylogeographic analysis and species distribution modelling to provide a climate change context for an observed decline in crown health and an increase in mortality in Eucalyptus wandoo, an endemic tree of south-western Australia.Methods Phylogeographic analyses were undertaken using restriction fragment length polymorphism analysis of chloroplast DNA in 26 populations across the species distribution. Parsimony analysis of haplotype relationships was conducted, a haplotype network was prepared, and haplotype and nucleotide diversity were calculated. Species distribution modelling was undertaken using Maxent models based on extant species occurrences and projected to climate models of the last glacial maximum (LGM).Key Results A structured pattern of diversity was identified, with the presence of two groups that followed a climatic gradient from mesic to semi-arid regions. Most populations were represented by a single haplotype, but many haplotypes were shared among populations, with some having widespread distributions. A putative refugial area with high haplotype diversity was identified at the centre of the species distribution. Species distribution modelling showed high climatic suitability at the LGM and high climatic stability in the central region where higher genetic diversity was found, and low suitability elsewhere, consistent with a pattern of range contraction.Conclusions Combination of phylogeography and paleo-distribution modelling can provide an evolutionary context for climate-driven tree decline, as both can be used to cross-validate evidence for refugia and contraction under harsh climatic conditions. This approach identified a central refugial area in the test species E. wandoo, with more recent expansion into peripheral areas from where it had contracted at the LGM. This signature of contraction from lower rainfall areas is consistent with current observations of decline on the semi-arid margin of the range, and indicates low capacity to tolerate forecast climatic change. Identification of a paleo-historical context for current tree decline enables conservation interventions to focus on maintaining genetic diversity, which provides the evolutionary potential for adaptation to climate change.     

Genetic structure and historical diversification of catfish Brachyplatystoma platynemum (Siluriformes: Pimelodidae) in the Amazon basin with implications for its conservation

Brachyplatystoma platynemum is a catfish species widely distributed in the Amazon basin. Despite being considered of little commercial interest, the decline in other fish populations has contributed to the increase in the catches of this species. The structure, population genetic variability, and evolutionary process that have driven the diversification of this species are presently unknown. Considering that, in order to better understand the genetic structure of this species, we analyzed individuals from seven locations of the Amazon basin using eight molecular markers: control region and cytochrome b mtDNA sequences, and a set of six nuclear microsatellite loci. The results show high levels of haplotype diversity and point to the occurrence of two structured populations (Amazon River and the Madeira River) with high values for F_ST. Divergence time estimates based on mtDNA indicated that these populations diverged about 1.0 Mya (0.2–2.5 Mya 95% HPD) using cytochrome b and 1.4 Mya (0.2–2.7 Mya 95% HPD) using control region. During that time, the influence of climate changes and hydrological events such as sea level oscillations and drainage isolation as a result of geological processes in the Pleistocene may have contributed to the current structure of B. platynemum populations, as well as of differences in water chemistry in Madeira River. The strong genetic structure and the time of genetic divergence estimated for the groups may indicate the existence of strong structure populations of B. platynemum in the Amazon basin.     

Spider biodiversity potential of an ungrazed and a grazed inland salt meadow in the National Park 'Neusiedler See-Seewinkel' (Austria): implications for management (Arachnida: Araneae)

To assess the biodiversity potential of an ungrazed and a grazed inland salt meadow in the Seewinkel (Eastern Austria), spider assemblages were recorded by pitfall trapping for 1 year. Both species assemblages consisted, to a large extent, of rare species of conservation interest. The species assemblage of the grazed site was dominated by Pardosa agrestis, but highly specific halotopobiontic species also occurred in higher numbers. Halotolerant species were also present in the ungrazed meadow, but their individual number was much lower. The species composition of this site reflects the more balanced microclimatical situation of the high sward. Comparison of the two assemblages with 207 other meadow spider assemblages of Central Europe shows a separated position, especially of the grazed site assemblage. High similarities with assemblages of meadows with a similar vegetation structure indicate a high importance of management. Considering the high proportion of rare species on both sites, the best management of the salt meadow and pan shores of the Seewinkel should combine areas of light grazing with ungrazed areas. However, the proportion of these parts and the intensity of grazing still remains to be determined by quantitative experiments.     

Low levels of allozyme variability in the threatened species Antirrhinum subbaeticum and A. pertegasii (Scrophulariaceae): implications for conservation of the species

AIMS: This study was designed to compare levels of genetic variation and its partitioning in three related species of Antirrhinum, A. subbaeticum, A. pertegasii and A. pulverulentum, and to check the hypothesis that species with small total population size have lower levels of genetic variability than those with bigger ones. This information should contribute to the development of conservation strategies of rare endemic species of Antirrhinum. METHODS: One hundred and seventy-seven plants were screened for variability at 14 allozyme loci by means of horizontal starch gel. Parameters of genetic diversity, and its partitioning, were calculated. An indirect estimate of gene flow was based on the equation: Nm = (1 - GST)/4GST. KEY RESULTS: Genetic variabilities in A. subbaeticum and A. pertegasii were found to be the lowest known for the genus, the within-population genetic diversity being correlated with population size in both species. The distribution of genetic diversity is strikingly different among species, with 85 % of the total variation distributed among populations in A. subbaeticum, 6 % in A. pertegasii and 23 % in A. pulverulentum. Estimated levels of gene flow were negligible for A. subbaeticum (0.04), high for A. pertegasii (3.92), and substantial for A. pulverulentum (0.83). Genetic and geographic distances were negatively correlated in A. pertegasii, whereas no significant correlation was found in the other two species. CONCLUSIONS: Levels of total genetic diversity agree with the hypothesis that species with small total population size have lower levels of genetic variability than those with bigger ones. Strategies for the conservation of the species are recommended, such as preservation of natural populations and avoidance of possible causes of threat, as well as ex situ preservation of seeds, reinforcement of small populations of A. subbaeticum with plants or seeds from the same population, and avoidance of translocations among populations.     

Dissimilarity of contemporary and historical gene flow in a wild carrot (Daucus carota) metapopulation under contrasting levels of human disturbance: implications for risk assessment and management of transgene introgression

Background and Aims

Transgene introgression from crops into wild relatives may increase the resistance of wild plants to herbicides, insects, etc. The chance of transgene introgression depends not only on the rate of hybridization and the establishment of hybrids in local wild populations, but also on the metapopulation dynamics of the wild relative. The aim of the study was to estimate gene flow in a metapopulation for assessing and managing the risks of transgene introgression.

Methods

Wild carrots (Daucus carota) were sampled from 12 patches in a metapopulation. Eleven microsatellites were used to genotype wild carrots. Genetic structure was estimated based on the F_ST statistic. Contemporary (over the last several generations) and historical (over many generations) gene flow was estimated with assignment and coalescent methods, respectively.

Key Results

The genetic structure in the wild carrot metapopulation was moderate (F_ST = 0·082) and most of the genetic variation resided within patches. A pattern of isolation by distance was detected, suggesting that most of the gene flow occurred between neighbouring patches (≤1 km). The mean contemporary gene flow was 5 times higher than the historical estimate, and the correlation between them was very low. Moreover, the contemporary gene flow in roadsides was twice that in a nature reserve, and the correlation between contemporary and historical estimates was much higher in the nature reserve. Mowing of roadsides may contribute to the increase in contemporary gene flow. Simulations demonstrated that the higher contemporary gene flow could accelerate the process of transgene introgression in the metapopulation.

Conclusions

Human disturbance such as mowing may alter gene flow patterns in wild populations, affecting the metapopulation dynamics of wild plants and the processes of transgene introgression in the metapopulation. The risk assessment and management of transgene introgression and the control of weeds need to take metapopulation dynamics into consideration.