Identifying indicator plant species of habitat quality and invasibility as a guide for peri-urban forest management

A floristic survey has been carried out in a peri-urban forest, the Sonian Forest in Brussels, to identify indicator plant species in the herbaceous layer, which could be used as an aid within the framework of a more sustainable management of the forest. Three hundred and seventy two (372) taxa have been identified, 33 of which are non-native (i.e. non-indigenous species regarding the study area, whether invasive or not). Criteria of habitat quality that have been chosen are the species richness, the commonness of the habitat, based on constitutive species, and its invasibility (vulnerability for invasion). On the basis of a comparison of the value of these criteria when each considered (potential indicator) species is present or not, 17 species have been recognised as reliable indicators of at least one of these three criteria. In particular, vegetation types containing either Anthriscus sylvestris, Galeopsis tetrahit or Senecio ovatus were found to be more susceptible to invasion than other habitats. The way to how the predictability of invasions might be effectively used as a management tool is discussed. Furthermore, we found a positive significant correlation (Bonferroni corrected probabilities) between the species richness and luminosity factor (derived from Ellenberg's indices), and the proportion of grassland and wetland species. The species richness was significantly negatively correlated with the proportion of woodland species. An increase in commonness was significantly correlated with a decrease in the proportion of geophytes. The usefulness of these results as an ecological basis for forest management is discussed.     

Leaf fluctuating asymmetry of common plantain as an indicator of habitat quality

Abstract

Although developmental instability (DI), measured as fluctuating asymmetry (FA), is expected to be positively related to environmental stress and negatively to habitat quality, the pattern found here was the reverse. Developmental instability of leaf traits (leaf width and vein distances within a leaf) was estimated (using two indices of FA: FA₄ and σ_i ²) and compared between three populations of Plantago major L. (Plantaginaceae) from northern Serbia. Two of the populations are from chronically polluted areas (Karaburma & Zemun), while Crni Lug is from an unpolluted, natural area. Results obtained using both FA indices were the same; higher asymmetry levels in the unpolluted area than in the polluted sites, were found for both traits. Between the two polluted sites, FA values were significantly higher in Karaburma site for vein distances within a leaf. Concerning differences in FA₄ values between samples, in two cases, results are similar to those found for σ_i ² values, for vein distances within leaf. These are the first quantitative data on P. major indicating that (i) plants living in the stressful sites are more symmetrical and (ii) leaf FA for plant species with wide ecological distribution such as P. major should be considered as an ‘index of habitat quality.’     

The population biology of mitigation: impacts of habitat creation on an endangered plant species

Conservation practitioners widely agree that optimal conservation strategies will maximize the amount of genetic variation preserved in target taxa, but there is ongoing debate about how that variation should be distributed through restoration and mitigation activities. Here, we evaluate the impacts of ~10 years of mitigation on the population genetic structure of Limnanthes vinculans, a state- and federally-listed endangered plant species restricted to ephemeral vernal pool wetlands in the Santa Rosa Plain of California. Using microsatellite loci to estimate patterns of neutral molecular variation, we found that created pools support similar levels of variation in L. vinculans as natural pools. Habitat creation and seed translocation have not disrupted the largest-scale patterns of population structure across the species range, but a concentration of mitigation activity towards the range center has reduced the extent of isolation-by-distance operating in this region and shifted the location of at least one genetic boundary. Patterns of genetic variation among populations in remnant vernal pools reveal that gene flow has historically occurred beyond the scale of individual pools at the center of the species range, while small genetic populations have differentiated around the range margins. On average, L. vinculans in created pools exhibit less cover and more restricted local distributions than those in remnant pools, but these patterns were driven by two particularly productive natural sites rather than consistent differences between natural and created sites. We conclude that mitigation activities have changed the historical patterns of gene flow within the species range to a moderate degree, that these changes will likely impact remnant pools through gene flow, and that current created sites provide less heterogeneous habitat for L. vinculans than do natural pools. Studies that track individual plants will be needed to determine if the changes in gene flow due to mitigation will have positive or negative impacts on the demographic and microevolutionary trajectories of L. vinculans. More generally, this study provides a retrospective analysis of the outcome of managing an endangered plant species through intensive mitigation, and yields several insights to inform future conservation strategies.     

A habitat quality indicator for common birds in Europe based on species distribution models

The EU 2020 Biodiversity Strategy requires the gathering of information on biodiversity to aid in monitoring progress towards its main targets. Common species are good proxies for the diversity and integrity of ecosystems, since they are key elements of the biomass, structure, functioning of ecosystems, and therefore of the supply of ecosystem services. In this sense, we aimed to develop a spatially-explicit indicator of habitat quality (HQI) at European level based on the species included in the European Common Bird Index, also grouped into their major habitat types (farmland and forest). Using species occurrences from the European Breeding Birds Atlas (at 50 km × 50 km) and the maximum entropy algorithm, we derived species distribution maps using refined occurrence data based on species ecology. This allowed us to cope with the limitations arising from modelling common and widespread species, obtaining habitat suitability maps for each species at finer spatial resolution (10 km × 10 km grid), which provided higher model accuracy. Analysis of the spatial patterns of local and relative species richness (defined as the ratio between species richness in a given location and the average richness in the regional context) for the common birds analysed demonstrated that the development of a HQI based on species richness needs to account for the regional species pool in order to make objective comparisons between regions. In this way, we proved that relative species richness compensated for the bias caused by the inherent heterogeneous patterns of the species distributions that was yielding larger local species richness in areas where most of the target species have the core of their distribution range. The method presented in this study provides a robust and innovative indicator of habitat quality which can be used to make comparisons between regions at the European scale, and therefore potentially applied to measure progress towards the EU Biodiversity Strategy targets. Finally, since species distribution models are based on breeding birds, the HQI can be also interpreted as a measure of the capacity of ecosystems to provide and maintain nursery/reproductive habitats for terrestrial species, a key maintenance and regulation ecosystem service.     

浙江省珍稀濒危植物物种多样性保护的关键区域

浙江省植物资源丰富,有野生维管植物215科1196属3283种,其中包含了我国特有属49个,浙江省特有植物约200余种,许多物种十分稀少,并受到严重威胁,亟待保护。但浙江省需优先保护的植物物种的分布并不是均匀的,有些地区的重要保护对象比较集中,对这些地区我们应该给予更多的保护。本文根据维管植物物种多样性、珍稀濒危植物的物种数量及个体数量特征、受威胁状况以及浙江省特有植物的分布情况,提出了浙江省珍稀濒危植物保护的7个关键区域：以西天目山为中心的浙西北山区,以古田山为中心的浙西山区,以九龙山为中心的浙西南山区,以凤阳山－百山祖为中心的浙南山区,以括苍山为中心的浙东山区,以天台山为中心的浙东丘陵,以普陀山为中心的舟山群岛。最后提出了浙江省植物物种多样性保护的几点建议。     

遗传多样性与濒危植物保护生物学研究进展

尽管对于濒危物种的遗传学人们已经进行了大量研究,但是种群遗传学在植物保护中的实际地位尚存在很大争议。濒危物种的遗传多样性可能会由于遗传漂变、近交的作用而丧失;但这种丧失更可能是濒危的结果而不是濒危的起因。遗传多样性水平与物种生存力之间没有任何必然的联系。但植物种群遗传结构如果由于自交不亲和等位基因的丧失和与亲缘种杂交造成的遗传同化而发生改变,那么它对物种生存力会产生明显负作用。     

Genetic diversity and karyotype of Pitcairnia azouryi: an endangered species of Bromeliaceae endemic to Atlantic Forest inselbergs

Plant species of various families, such as those of Bromeliaceae, occur on inselbergs where they are subject to geographic isolation and environmental conditions that can lead to genetic erosion. This, in turn, can result in the loss of natural populations due to homozygosis, or changes in ploidy that may lead to reproductive isolation. The genetic diversity of five natural populations of Pitcairnia azouryi was measured using nine microsatellite markers transferred from P. albiflos and P. geyskesii. Chromosome numbers and nuclear DNA content were also evaluated. The results indicated moderate genetic differentiation among populations (F_ST?=?0.188), and significant gene flow (N_m?=?1.073) in four of the five populations. P. azouryi has, predominantly, 2n?=?50 chromosomes and DNA content of 2C?=?1.16 pg, but the tetraploid condition was found (2n?=?100 and 2C?=?2.32 pg) in seedlings of an individual of the most geographically isolated population. The moderate level of genetic structuring observed for P. azouryi seems to be related to its disjoint geographical distribution and the locally aggregated spatial structure of the populations, which are isolated from each other, hindering the inter and intrapopulational gene flow. This interpretation was also evidenced by the mantel test (r?=?0.777, P?<?0.05). The occurrence of diploid individuals with tetraploid seedlings is indicative of events of eupolyploidization, possibly due to the environmental conditions of this geographically isolated population.

     

High genetic diversity in a rare and endangered sunflower as compared to a common congener

Determining the genetic structure of isolated or fragmented species is of critical importance when planning a suitable conservation strategy. In this study, we use nuclear and chloroplast SSRs (simple sequence repeats) to investigate the population genetics of an extremely rare sunflower, Helianthus verticillatus Small, which is known from only three locations in North America. We investigated levels of genetic diversity and population structure compared to a more common congener, Helianthus angustifolius L., using both nuclear and chloroplast SSRs. We also investigated its proposed hybrid origin from Helianthus grosseserratus Martens and H. angustifolius. Twenty-two nuclear SSRs originating from the cultivated sunflower (Helianthus annuus L.) expressed sequence tag (EST) database, and known to be transferable to H. verticillatus and its putative parental taxa, were used in this study thereby allowing for statistical control of locus-specific effects in population genetic analyses. Despite its rarity, H. verticillatus possessed significantly higher levels of genetic diversity than H. angustifolius at nuclear loci and equivalent levels of chloroplast diversity. Significant levels of population subdivision were observed in H. verticillatus but of a magnitude comparable to that of H. angustifolius. Inspection of multilocus genotypes also revealed that clonal spread is highly localized. Finally, we conclude that H. verticillatus is not of hybrid origin as it does not exhibit a mixture of parental alleles at nuclear loci, and it does not share a chloroplast DNA haplotype with either of its putative parents.     

Comparative population genetics of mimetic Heliconius butterflies in an endangered habitat; Brazil's Atlantic Forest

Background

The islands of North Maluku, Indonesia occupy a central position in the major prehistoric dispersal streams that shaped the peoples of Island Southeast Asia and the Pacific. Within this region a linguistic contact zone exists where speakers of Papuan and Austronesian languages reside in close proximity. Here we use population genetic data to assess the extent to which North Maluku populations experienced admixture of Asian genetic material, and whether linguistic boundaries reflect genetic differentiation today.

Results

Autosomal and X-linked markers reveal overall Asian admixture of 67% in North Maluku, demonstrating a substantial contribution of genetic material into the region from Asia. We observe no evidence of population structure associated with ethnicity or language affiliation.

Conclusions

Our data support a model of widespread Asian admixture in North Maluku, likely mediated by the expansion of Austronesian-speaking peoples into the region during the mid Holocene. In North Maluku there is no genetic differentiation in terms of Austronesian- versus Papuan-speakers, suggesting extensive gene flow across linguistic boundaries. In a regional context, our results illuminate a major genetic divide at the Molucca Sea, between the islands of Sulawesi and North Maluku. West of this divide, populations exhibit predominantly Asian ancestry, with very little contribution of Papuan genetic material. East of the Molucca Sea, populations show diminished rates of Asian admixture and substantial persistence of Papuan genetic diversity.     

Forest classification in an Amazonian rainforest landscape using pteridophytes as indicator species

Habitat classification systems are poorly developed for tropical rainforests, where extremely high plant species richness causes numerous methodological difficulties. We used an indicator species approach to classify primary rainforest vegetation for purposes of comparative wildlife habitat studies. We documented species composition of pteridophytes (ferns and fern allies) in 635 plots (2×100 m) along 8 transects within a continuous rainforest landscape in northeastern Peruvian Amazonia. Considerable floristic variation was found when the data were analyzed using multivariate methods. The obtained forest classification was interpreted with the help of indicator value analysis and known soil preferences of the pteridophyte species. The final classification included four forest types: 1) inundated forests, 2) terrace forests, 3) intermediate tierra firme forests and 4) Pebas Formation forests. This rapid and relatively simple vegetation classification technique offers a practical, quantitative method for large-scale vegetation inventory in complex rainforest landscapes.     

Genetic diversity and structure of an endangered medicinal plant species (Pilocarpus microphyllus) in eastern Amazon: implications for conservation

Few studies have evaluated the genetic status of medicinal plants exposed to commercial harvesting. Here, we examine the genetic variability of Pilocarpus microphyllus, an endemic and threatened medicinal plant species from the eastern Amazon, across its largest remaining wild population. Popularly known as jaborandi, species of Pilocarpus genus are the unique known natural source of pilocarpine, an alkaloid used to treat glaucoma and xerostomia. However, Populations of P. microphyllus has experienced a severe decline in the last decades. Using RAD sequencing, we identified a total of 5,266 neutral and independent SNPs in 277 individuals collected from the Carajás National Forest (CNF). We quantified genetic diversity and gene flow patterns and estimated the minimum number of individuals necessary to establish a germplasm bank. Our results revealed high genetic diversity and four spatially distinct clusters of P. microphyllus with substantial admixture among them. Geographic distance and temperature dissimilarity were the factors that best explained the relatedness patterns among individuals. Additionally, our findings indicate that at least 40 matrices sampled randomly from each population would be required to conserve genetic diversity in the long term. In short, P. microphyllus showed high levels of genetic diversity and an effective population size (N_E) sufficient to reduce the likelihood of extinction due to inbreeding depression. Our results indicate that diversity has been maintained despite the continuous harvesting of raw leaf material in the area over recent decades. Finally, the results provide information essential for the design of a germplasm bank to protect the endangered medicinal plant species.

     

The species pool concept as a framework for studying patterns of plant diversity

Co‐existence theories fail to adequately explain observed community patterns (diversity and composition) because they mainly address local extinctions. For a more complete understanding, the regional processes responsible for species formation and geographic dispersal should also be considered. The species pool concept holds that local variation in community patterns is dependent primarily on the availability of species, which is driven by historical diversification and dispersal at continental and landscape scales. However, empirical evidence of historical effects is limited. This slow progress can be attributed to methodological difficulties in determining the characteristics of historical species pools and how they contributed to diversity patterns in contemporary landscapes. A role of landscape‐scale dispersal limitation in determining local community patterns has been demonstrated by numerous seed addition experiments. However, disentangling general patterns of dispersal limitation in communities still requires attention. Distinguishing habitat‐specific species pools can help to meet both applied and theoretical challenges. In conservation biology, the use of absolute richness may be uninformative because the size of species pools varies between habitats. For characterizing the dynamic state of individual communities, biodiversity relative to species pools provides a balanced way of assessing communities in different habitats. Information about species pools may also be useful when studying community assembly rules, because it enables a possible mechanism of trait convergence (habitat filtering) to be explicitly assessed. Empirical study of the role of historic effects and dispersal on local community patterns has often been restricted due to methodological difficulties in determining habitat‐specific species pools. However, accumulating distributional, ecological and phylogenetic information, as well as use of appropriate model systems (e.g. archipelagos with known biogeographic histories) will allow the species pool concept to be applied effectively in future research.     

The impact of two non-native plant species on native flora performance: potential implications for habitat restoration

Both Impatiens glandulifera and Fallopia japonica are highly invasive plant species that have detrimental impacts on native biodiversity in areas where they invade and form dense monocultures. Both species are weakly dependent on arbuscular mycorrhizal fungi (AMF) for their growth and, therefore, under monotypic stands, the AMF network can become depauperate. We evaluated the impact of I. glandulifera and F. japonica on the performance (expressed as shoot biomass) of three UK native species (Plantago lanceolata, Lotus corniculatus and Trifolium pratense) grown in soil collected from under stands of both invasive plants and compared to plants grown in soil from under stands of the corresponding native vegetation. All native species had a higher percentage colonisation of AMF when grown in uninvaded soil compared to the corresponding invaded soil. P. lanceolata and L. corniculatus had a higher biomass when grown in uninvaded soil compared to corresponding invaded soil indicating an indirect impact from the non-native species. However, for T. pratense there was no difference in biomass between soil types related to I. glandulifera, suggesting that the species is more reliant on rhizobial bacteria. We conclude that simply managing invasive populations of non-native species that are weakly, or non-dependent, on AMF is inadequate for habitat restoration as native plant colonisation and establishment may be hindered by the depleted levels of AMF in the soil below invaded monocultures. We suggest that the reintroduction of native plants to promote AMF proliferation should be incorporated into future management plans for habitats degraded by non-native plant species.     

Evaluating the local habitat history deepens the understanding of the extinction debt for endangered plant species in semi-natural grasslands

Habitat losses occur non-randomly within human-modified landscapes, resulting in high spatial heterogeneity of local habitat histories. Although local habitat history can modulate the existence of extinction debt (i.e., the number of populations predicted to become extinct) in a landscape, its role in detecting extinction debt has not been examined explicitly. We aimed to compare the detectability of extinction debt among populations of an endangered semi-natural grassland species, Echinops setifer (Compositae), in the grassland landscape of Mt. Aso, Japan. We classified populations into three groups that differed in local habitat history: stable (habitat loss ≤30% since the 1930s), moderately decreased (30% < loss ≤ 90%), and severely decreased (loss >90%). We then evaluated whether the effects of habitat areas during the 1930s and 2000s varied among groups to explain population size by GLMMs and estimated coefficient of explanatory variable by Bayesian MCMC methods. Within the groups, stable group showed significant positive relationships with both past and current habitat areas. The moderately decreased group only showed significant positive relationships with past habitat areas, indicating the existence of extinction debt in these populations. The severely decreased group only showed significant positive relationships with current habitat areas, indicating that they may have already paid their extinction debt because the rate of grassland loss exceeded the extinction threshold. Even within the same landscape, extinction debt varied in response to local habitat history. In spatially heterogeneous landscapes, evaluation of effects of local habitat history can elucidate the habitat-based extinction risks for plant populations.     

Phytoplankton alpha diversity as an indicator of environmental changes in a neotropical floodplain

Habitat fragmentation, overexploitation of natural resources, the introduction of alien species and environmental degradation in aquatic environments are the main causes of reductions in aquatic biota diversity. Phytoplankton represent good ecological indicators because they are highly diverse and rapidly respond to a wide array of environmental disturbances. We investigated the interannual variation in alpha diversity of the phytoplankton community in lakes of an alluvial floodplain. We predicted that the phytoplankton diversity decreases over time in lakes and rivers subjected to human activities, whereas those biotopes in areas under pristine environmental conditions do not show a reduction in alpha diversity. Phytoplankton samples were taken quarterly over a period of eleven years (2000–2010), from ten localities associated with three large rivers, which showed different uses of the watershed. The time series of alpha diversity was analysed, to assess the temporal trend, in addition to their relationships with environmental factors. Phytoplankton alpha diversity in the Upper Paraná River floodplain ranged between 4 and 87 species and showed a mean of 30 (±16.5). Sites associated with the Paraná River showed a decline in diversity, which was associated with transparency, nitrogen and phosphorus forms. These results reflect a combination of seston retention by damming and an increase in the N:P ratio, which appears to negatively affect phytoplankton diversity. If temporal trends in environmental variation and the phytoplankton community remain, the future consequences for phytoplanktonic diversity in the Paraná subsystem will be severe, which might cause changes in the trophic structure and dynamics, and therefore in the functioning of environments, since this community is one of the main sources of energy for other trophic levels.     

Neither common nor garden: The garden as a refuge for threatened plant species

An increasing number of plant species are being lost to the world primarily as a result of massive levels of degradation to wild habitats, and in a smaller number of cases through inappropriate trading. A handful of these extinctions have been prevented, or perhaps delayed, through cultivation in gardens and nurseries (Melville, 1970). In a well-stocked garden-centre the amateur horticulturist can purchase a number of species now extinct in the wild. These species survive as genetic fragments of the diversity originally present in the lost wild population. This paper, through a series of case studies, discusses the ambivalent relationship between the horticulturist and species conservation.     

Genetic structure and gene flow in a metapopulation of an endangered plant species,Silene tatarica

We investigated the distribution of genetic variation within and between seven subpopulations in a riparian population of Silene tatarica in northern Finland by using amplified fragment length polymorphism (AFLP) markers. A Bayesian approach-based clustering program indicated that the marker data contained not only one panmictic population, but consisted of seven clusters, and that each original sample site seems to consist of a distinct subpopulation. A coalescent-based simulation approach shows recurrent gene flow between subpopulations. Relative high FST values indicated a clear subpopulation differentiation. However, amova analysis and UPGMA-dendrogram did not suggest any hierarchical regional structuring among the subpopulations. There was no correlation between geographical and genetic distances among the subpopulations, nor any correlation between the subpopulation census size and amount of genetic variation. Estimates of gene flow suggested a low level of gene flow between the subpopulations, and the assignment tests proposed a few long-distance bidirectional dispersal events between the subpopulations. No apparent difference was found in within-subpopulation genetic diversity among upper, middle and lower regions along the river. Relative high amounts of linkage disequilibrium at subpopulation level indicated recent population bottlenecks or admixture, and at metapopulation levels a high subpopulation turnover rate. The overall pattern of genetic variation within and between subpopulations also suggested a 'classical' metapopulation structure of the species suggested by the ecological surveys.     

Differential influence of a monotypic and diverse native aquatic plant bed on a macroinvertebrate assemblage; an experimental implication of exotic plant induced habitat

Aquatic plants mediate ecological processes in aquatic habitats, specifically predator–prey (bluegill sunfish (Lepomis macrochirus Rafinesque)-macroinvertebrate) interactions. Macroinvertebrate colonization is directly and indirectly influenced by substrate heterogeneity, interstitial space, and surface complexity. Exotic invasive plant species, such as Hydrilla verticillata L.F. Royle, may alter the available structure in aquatic habitat by creating a shift to a homogeneous habitat, thus affecting the macroinvertebrate community. Since macroinvertebrates provide a food base for young phytophilic fishes, changes in their density and abundance may alter food webs. We investigated the hypothesis that macroinvertebrate community structure is influenced by differences in habitat heterogeneity by measuring difference between a heterogeneous native aquatic plant bed, homogenous hydrilla plant bed, and habitat with no plants. Studies were conducted in the field (pond) and the experimental treatments were: (1) no plants, (2) monotypic bed of hydrilla, and (3) diverse native plants. Aquatic plants, regardless of species, supported greater macroinvertebrate abundance, richness, and biomass. Macroinvertebrate abundance, richness, and biomass in a hydrilla-dominated habitat did not differ significantly from a diverse plant habitat, except for richness in October. Indicator taxa did differ significantly between respective treatments, suggesting a change in species composition. However, no significant effect of fish predation on macroinvertebrate populations and/or community structure was documented. The data suggest that a shift from a natural mosaic of vegetated habitat to a highly complex monotypic habitat (e.g., exotic hydrilla) may reduce spatial heterogeneity important to structuring a macroinvertebrate assemblage. Handling editor: S. M. Thomaz     

No genetic diversity at molecular markers and strong phenotypic plasticity in populations of Ranunculus nodiflorus, an endangered plant species in France

BACKGROUND AND AIMS: Although conservation biology has long focused on population dynamics and genetics, phenotypic plasticity is likely to play a significant role in population viability. Here, an investigation is made into the relative contribution of genetic diversity and phenotypic plasticity to the phenotypic variation in natural populations of Ranunculus nodiflorus, a rare annual plant inhabiting temporary puddles in the Fontainebleau forest (Paris region, France) and exhibiting metapopulation dynamics. METHODS: The genetic diversity and phenotypic plasticity of quantitative traits (morphological and fitness components) were measured in five populations, using a combination of field measurements, common garden experiments and genotyping at microsatellite loci. KEY RESULTS: It is shown that populations exhibit almost undetectable genetic diversity at molecular markers, and that the variation in quantitative traits observed among populations is due to a high level of phenotypic plasticity. Despite the lack of genetic diversity, the natural population of R. nodiflorus exhibits large population sizes and does not appear threatened by extinction; this may be attributable to large phenotypic plasticity, enabling the production of numerous seeds under a wide range of environmental conditions. CONCLUSIONS: Efficient conservation of the populations can only be based on habitat management, to favour the maintenance of microenvironmental variation and the resulting strong phenotypic plasticity. In contrast, classical actions aiming to improve genetic diversity are useless in the present case.