Aquatic Plant Diversity Research Articles

Managing Successional Stage Heterogeneity to Maximize Landscape-Wide Biodiversity of Aquatic Vegetation in Ditch Networks.

The presence of a high diversity of different successional stages in a landscape may help to conserve and promote landscape-wide biodiversity. A strategy to achieve this is using Cyclic Rejuvenation through Management (CRM), an approach employed in a variety of different ecosystems. CRM periodically resets the successional stages in a landscape. For aquatic systems this constitutes vegetation removal and dredging. For this approach to be useful (a) successional stages are required to be different in community composition and (b) these differences need to be caused by true replacement of species between stages. While potentially valid, these assumptions are not generally tested prior to application of CMR. In this study we test these assumptions to explore the usefulness of managing on successional stage heterogeneity for maximizing landscape-wide aquatic plant diversity. We carried out vegetation surveys in the ditch networks of 21 polder landscapes in Netherlands, each containing 24 ditch reaches. Using a clustering approach combined with insight from literature on vegetation succession in these systems we assigned our sampled communities to defined successional stages. After partitioning landscape diversity into its alpha and beta components, we quantified the relative importance of replacement among successional stages. Next, through scenario analyses based on simulations we studied the effects of reducing successional stage heterogeneity on landscape-wide biodiversity. Results showed that differences in community composition among successional stages were a potentially important factor contributing to landscape diversity. Early successional stages were characterized by higher replacement of species compared to late successional stages. In a scenario of gradual decrease of heterogeneity through the systematic loss of the earliest successional stages we found 20% of the species richness in a polder was lost, pointing toward the importance of maintaining early successional stages in a polder. This makes a compelling case for application of CRM within agricultural drainage ditch landscapes to maximize regional aquatic plant diversity. While applied to drainage ditch systems, our data-driven approach is broadly applicable to other systems and may help in providing first indications of the potential of the CRM approach. We argue that CRM may maintain and promote regional biodiversity without compromising the hydrological function of the systems.

Mixtures of macrophyte growth forms promote nitrogen cycling in wetlands

The importance of aquatic plant diversity in regulating nutrient cycling in wetlands remains poorly understood. We investigated how variation in macrophyte growth form (emerging, submerged and bryophyte) combinations and species mixtures affect nitrogen (N) removal from the water and N accumulation in plant biomass. We conducted a wetland mesocosm experiment for 100 days during July–September 2015. Twelve species were grown in mono- and in two-species mixed cultures for a total of 32 single and two-growth form combinations. Nitrogen removal from the water was quantified on three occasions during the experiment, while N accumulation in plant biomass was determined following termination of the experiment. The number of species and growth forms present increased N removal and accumulation. The growth form combinations of emerging and bryophyte species showed the highest N accumulation and N removal from water, followed by combinations of emerging species. By contrast, submerged species growing in the presence of emerging or other submerged species showed the lowest levels of N accumulation and N removal. Temporal variation in N removal also differed among growth form combinations: N removal was highest for emerging-bryophyte combinations in July, but peaked for the emerging-submerged and emerging-bryophyte combinations in August. Indeed, the occurrence of complementarity among macrophyte species, particularly in combinations of bryophyte and emerging species, enhanced N removal and uptake during the entire growing season. Our study highlights the importance of bryophytes, which have been neglected in research on nutrient cycling in wetlands, for aquatic N cycling, especially given their worldwide distribution across biomes. Overall, our findings point towards the potential important role of the diversity of macrophyte growth forms in regulating key ecosystem processes related to N cycling in wetlands.

Temporary freshwater wetlands floristics in central Mexico highlands

Background: Mexico has a high diversity of aquatic and subaquatic plants that occur between 1,000 and 2,500 m of elevation, although a larger proportion of aquatic plants is concentrated at lower altitudes. Temporary wetlands harbor close to 73 % of the aquatic species in Mexico. These systems are under a strong anthropogenic pressure and suffer constant degradation.Questions: i) How many species grow in highland temporary wetlands? ii) Are they floristically similar? iii) Is there a latitudinal pattern of species richness?Studied groups: Charophyta, Pteridophyta, Angiosperms.Study site and years of study: Central Mexico (39 wetlands) from 2015 to 2016.Methods: We collected in 39 temporary wetlands for two years. We made a presence/absence list of species per locality, and calculated floristic similarities and correlations between wetlands. We include data characterizing life form, plant use, and conservation status.Results: We found 126 species belonging to 80 genera and 38 families. The richest families were Cyperaceae, Asteraceae, and Poaceae. As to genera, Eleocharis , Cyperus , and Juncus had more species. Species with the widest distributions were Persicaria mexicana , Marsilea mollis , Luziola fluitans , Heteranthera peduncularis , and Nymphoides fallax . We found five different life forms – all herbaceous, including 27 threatened species, 24 species with economic use, 48 endemic species, and 19 cosmopolitan species. In addition, we found 20 species recorded for the first time in some states included in our study, and two species of Eleocharis that might represent undescribed species. The richest wetland harbors 40 species, the poorest has only five. Wetlands were comparable to each other in species composition, and species richness increases towards the south.Conclusions: Temporary wetlands harbor a high floristic diversity and are similar to each other. Lower latitudes host higher numbers of species.

Aquatic Plant Diversity in Italy: Distribution, Drivers and Strategic Conservation Actions.

Italy is recognized as one of the prominent hot spot areas for plant diversity at regional and global scale, hosting a rich range of ecosystems and habitat types. This is especially true considering aquatic habitats, which represent a major portion of the total water surfaces in the Mediterranean region. Nevertheless, only a scant attention was paid to clarify the species richness of aquatic plant and its contribution to the total diversity at the country scale, despite such plants are seriously threatened at multiple scales. This paper provided the first comprehensive inventory of aquatic plants at the whole country scale, collecting data on species’ distribution, trends, and explanatory determinants of species richness. We confirmed the key contribution of Italy to the regional and global aquatic plant diversity with a total of 279 species recorded since 2005, equal to the 88.5%, 55.9% and ∼10% of the richness estimated at European/Mediterranean, Palearctic and global scale, respectively. Ten species are considered extinct in the wild [among which Aldrovanda vesiculosa L., Caldesia parnassifolia (Bassi ex L.) Parl., Helosciadium repens (Jacq.) W.J.D. Koch, and Pilularia globulifera L.], four were doubt [among which Luronium natans (L.) Raf., Utricularia intermedia Hayne, and U. ochroleuca R.W. Hartman.], and eight were erroneously reported in the past, among which Isoëtes lacustris L., Myosotis rehsteineri Wartm., and Ranunculus aquatilis L. Only 18 species – mainly helophytes (14) – were present in all the 20 Italian regions, whereas hydrophytes showed most scanty regional frequencies. Temperature, latitude, area and water resources availability are the main drivers of aquatic plant spatial arrangement and diversity. Furthermore, the number of inhabitants per km2 well described the number of “lost species” since 2000. The findings of the present survey call for an urgent elaboration of large-scale strategies to ensure the survival of aquatic plants, stressing on multiple functions played by aquatic plants in supporting national economy and human well-being. In this context, Italy can play a fundamental role guaranteeing temporary refuge for projected or expected species migrations along latitude and longitude gradients. Besides, in hyper-exploited landscapes man-made water bodies can further enhance the achievement of minimum conservation targets.

Examination of the link between life stages uncovered the mechanisms by which habitat characteristics affect odonates

AbstractThe larval and adult stages of amphibious animals are affected by both aquatic and terrestrial habitat characteristics, and each stage also affects the other. However, this link between life stages has been largely overlooked in previous studies. We examined the effect of aquatic and terrestrial habitat characteristics on the diversity of larval and adult odonates, taking into account the link between the two life stages. Species diversity of adult and larval odonates and aquatic plants, as well as patterns of land use, was investigated in 63 irrigation ponds. We created structural equation models, with paths from land use and aquatic plants characteristics to larval and adult stages of odonates, as well as between the two stages, and chose the best model based on the lowest Akaike information criterion. Adult odonates, but not larvae, were affected by aquatic and terrestrial habitat characteristics, suggesting that the former is the key stage for odonate communities. We observed a positive relationship between the diversity of aquatic plants and larval odonates, but this was in fact due to the effects of aquatic plants on adults, which carried over to the larval stage. Our study showed that a consideration of the link between life stages is crucial for a complete understanding of the relationship between habitat characteristics and amphibious animal populations.

Diversity of aquatic plants in Chaohu Basin

Diversity of aquatic plants in Chaohu Basin

Effect of wetland management: are lentic wetlands refuges of plant-species diversity in the Andean-Orinoco Piedmont of Colombia?

Accelerated degradation of the wetlands and fragmentation of surrounding vegetation in the Andean–Orinoco Piedmont are the main threats to diversity and ecological integrity of these ecosystems; however, information on this topic is of limited availability. In this region, we evaluated the value of 37 lentic wetlands as reservoirs of woody and aquatic plants and analyzed diversity and changes in species composition within and among groups defined according to management given by: (1) type (swamps, heronries, rice fields, semi-natural lakes, constructed lakes and fish farms) and (2) origins (natural, mixed and artificial). A total of 506 plant species were recorded: 80% woody and 20% aquatic. Of these, 411 species (81%) were considered species typical of the area (Meta Piedmont distribution). Diversity patterns seem to be driven by high landscape heterogeneity and wetland management. The fish farms presented the highest diversity of woody plants, while swamps ranked highest for aquatic plant diversity. Regarding wetland origin, the artificial systems were the most diverse, but natural wetlands presented the highest diversity of typical species and can therefore be considered representative ecosystems at the regional scale. Our results suggest that lentic wetlands act as refuges for native vegetation of Meta Piedmont forest, hosting 55% of the woody of Piedmont species and 29% of the aquatic species of Orinoco basin. The wetlands showed a high species turnover and the results indicated that small wetlands (mean ± SD: size = 11 ± 18.7 ha), with a small area of surrounding forest (10 ± 8.6 ha) supported high local and regional plant diversity. To ensure long-term conservation of lentic wetlands, it is necessary to develop management and conservation strategies that take both natural and created wetlands into account.

Founder events and pre-glacial divergences shape the genetic structure of European Collembola species.

BackgroundClimate oscillations in the Cenozoic reduced species richness and genetic diversity of terrestrial and aquatic animals and plants in central and northern Europe. The most abundant arthropods in temperate soils are Collembola that live in almost any soil-related habitat. Extant species show little morphological variation to Eocene fossils, suggesting persistence of species in stable habitats for millions of years. Collembola are able to evade adverse climatic conditions by moving into deeper soil layers and are tolerant to frost and draught. If these adaptations sufficed for surviving glacial periods remains open and needs to be investigated in a phylogeographic context, i.e. investigating spatial structure on molecular level. We investigated the molecular variation of three common species of Collembola at a pan-European scale to identify glacial refuges and post-glacial colonization patterns with three genetic markers.ResultsAll genes revealed remarkable genetic structure between but not within populations, suggesting density dependent processes for establishment of populations (founder-takes-all principle), which is common for European animals and plants. In contrast to the post-glacial recolonization patterns of many aboveground organisms, divergence times of most geographic lineages indicate preservation of genetic structure since the Miocene.ConclusionsCollembola survived severe climatic changes including those during Quatenary glaciation and kept high genetic variance across Europe. Likely the buffering of temperature oscilliations in soil and the ability to evade adverse climatic conditions due to cold-tolerance and horizontal migration enabled Collembola to evade strong selective pressure of abiotic forces.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0719-8) contains supplementary material, which is available to authorized users.

Seasonal dynamics in the relative density of aquatic flora along some coastal areas of the Red Sea, Tabuk, Saudi Arabia

Plants are the producers of all autotrophic ecosystems’ and are the base of the food chain taking energy from the sun and converting it into food for all other organisms through photosynthesis. Plants grow in certain places and seasons when the environmental factors are suitable for their germination, growth and developments that influence their diversity. Environmental factors can include abiotic factors such as temperature, light, moisture, soil nutrients; or biotic factors like competition from other plants or grazing by animals. Anthropogenic perturbations can also influence distribution patterns. Monitoring of ecological habitats and diversity of some aquatic flora along some coastal areas of Red Sea has been done to understand the dynamics of aquatic plants influenced by prevailing environmental and anthropogenic perturbations The results of this research showed that the summer season is the most suitable period for the study of aquatic plant diversity along the coastal sites of Red Sea. The aquatic flora had high relative density and diversity in April, May, June and July and these four months of the summer season are best for collection of aquatic plants from the selected coastal areas of Red Sea for medicinal purposes and ecological studies.

Short‐term dynamics of submerged aquatic vegetation diversity and abundance in deep lakes

AbstractQuestionWhat are the short‐term trends of submerged aquatic vegetation (SAV) in deep lakes? Is it possible to measure significant changes in SAV distribution in deep lakes characterized by different trophic states and stable water physico‐chemical conditions using standard procedures over a 3‐yr period (2010–2013), as defined by the Water Framework Directive?LocationWe collected data from four deep lakes belonging to the Italian volcanic lake system (central Italy), which is one of the most important reserves of freshwater in Mediterranean Italy as well as one of the main hotspots of stonewort diversity in the Mediterranean area.MethodsMacrophytes were sampled along five transects in each lake in 2010 and 2013. Data on aquatic plant diversity, composition and abundance were collected from each 1‐m depth intervals down to the maximum colonization depth. Simultaneously, the water quality and climate were assessed by standard procedures. Data were analysed with PCA, ANOVA, PROTEST and rank abundance curves.ResultsThe sampling revealed a significant rearrangement of SAV. Increased species diversity in the first meters of depth (0–5 m) was due to the migration of mid‐depth species to lower depths. A reduction in the maximum growing depth of macrophytes was observed within the deepest stonewort communities (below 5 m). No significant changes emerged in water quality or climate.ConclusionsOver 3 yr, SAV displayed significant changes that appear to be independent of summer nutrient conditions and climate drivers. In particular, vascular and stonewort species underwent a distinct spatial rearrangement according to specific behaviours. The present data point to the need for more rigorous analyses of the intra‐annual dynamics of macrophytes in deep lakes. An influence of the significant increase in spring precipitation (which is in keeping with local climate variability) recorded in central Italy in the last decade cannot be ruled out a priori, nor can the possibility of stochastic fluctuations be excluded. All these considerations further highlight the critical role of aquatic plants as bioindicators.

Using morphology and genomic template stability (GTS) tracking herbicide effect on some submersed aquatic plants

The biodiversity are related to environmental status, the natural ponds contained more aquatic plant diversity than paddy field. Some species were found only in paddy fields e.g. Najas Graminea Del., while, some species were found only in natural water pond such as Ceratophyllum demersum Linn. Therefore these major species were selected for herbicide effect testing. The effect of glyphosate and butachlor on aquatic plant was observed in experiment, the color and morphology showed changing related to higher dose treatment. The RAPD profiles was analyzed for genomic template stability (GTS), the results indicated that GTS of Hydrilla verticellata was lowest (7.14%GTS), follow by Utricularia aurea lour (30.77 % GTS), Najas Graminea Del (38.71 %GTS), and Nitella sp. (59.38%GTS), respectively. The results indicated that these herbicides caused abnormally morphology and DNA instability, the RAPD profile cloud be used as biomarker for detection of herbicide contamination in aquatic ecological system.

Using Morphology and Genomic Template Stability (GTS) to Track Herbicide Effect on Some Submersed Aquatic Plants

This study aimed to detect the genotoxiceffects of glyphosate on aquatic plants by the RAPD-PCR technique. Native aquatic plants were screened for herbicide testing. The aquatic plant amounts and species were counted and a comparison was made between natural ponds and paddy fields for a total of 17 sites; paddy fields (site 1-10), ponds beside paddy fields (site 11-14), and natural ponds (site 15-17). At each studied site, 5 randomized sampling plots of 2 x 5 m size were performed. Generally, the natural ponds contained more aquatic plant diversity than the paddy fields. However, some species such as Najas gramineaDel. and Ceratophyllum demersumLinn. were found onlyin the paddy fields and natural ponds, respectively. The effect of glyphosate and butachlor on aquatic plants was observed. Changes in color and morphology were found to be related to higher dose treatment. The RAPD profiles were analyzed for the study of genomic template stability (GTS). Results indicated that the GTS of Hydrilla verticellata was lowest (7.14 %GTS),followed byUtricularia aurealour (30.77 %GTS), N. gramineaDel. (38.71 %GTS), and Nitellasp. (59.38 %GTS). These results confirmed the effects of herbicides on abnormal morphology and DNA instability. In addition, results of genotoxicity of glyphosate on some aquatic plants (Hydrilla verticellata, Utricularia aurea lour, and N. graminea Del.), and macroalgae (Nitella sp.) verified that the method of RAPD-PCR could be used as a biomarker to detect herbicide contamination in aquatic ecological systems.

A new locality of endangered bog bulrush Schoenoplectiella mucronata (Cyperaceae) in the Eastern Poland

A new locality of Schoenoplectiella mucronata - an endangered and warm-temperature wetland spe- cies was found in Western Polesie (Eastern Poland). The new station is situated far away to the north-east from all known Polish sites and belongs to the easternmost one within European range of the species. The mesotrophic Lake Kleszczow in which we have found a new population of S. mucronata was characterised by a good ecological state as well as high diversity of aquatic plants dominated by a charophyte meadow. The studied species occurred in a phytocoenosis which is similar to a not known in Poland plant community Typho angustifoliae-Schoenoplectetum mucronati described from Hungary.

Checklist of aquatic and marshy Monocotyledons from the Araguaia River basin, Brazilian Cerrado.

BackgroundThe Araguaia River basin runs through the states of Goiás, Mato Grosso, Tocantins, and Pará, covering 373,000 Km2, mostly within the Brazilian Cerrado. The region has a wide variety of wetlands. The climate is characterized by high temperatures and strongly seasonal precipitation. There are two well defined seasons: the dry season (winter-spring) and the rainy season (summer- fall). The Araguaia River basin is dominated by plinthosoils that are found in low flat areas, poorly drained and prone to flooding, yielding wetland habitats of high plant diversity. Since the 1970s, human activities have led to reduction in both the diversity and area of wetlands. The construction of the Belém-Brasília highway and hydroelectric dams, as well as the expansion of agricultural and mining activities, have had major impacts on the region.New informationThe flora diversity data of the Araguaia River basin was developed through field work, herbarium research, and use of a database (Species Link). The resulting checklist of 162 aquatic and marshy monocotyledons from the Araguaia River basin represents 20 families and 50 genera. Cyperaceae (51 spp.), Poaceae (39 spp.), and Eriocaulaceae (16 spp.) are the most representative families. Life form analysis indicates that helophytes predominate (98 spp.; 60.5%). One hundred one species are native to tropical and/or subtropical America and twenty one are endemic to Brazil. Ninety-three species are new occurrences for the Araguaia River basin. Among them, three species are reported in the Brazilian Cerrado for the first time. This work contributes to the understanding of aquatic plant diversity in the Cerrado and other savanna-like vegetation physiognomies; environments and habitats poorly understood taxonomically and undercollected generally.

Paleoclimatic significance of the late Quaternary plant macrofossils from the Gokarna Formation, Kathmandu Valley, Nepal

Late Quaternary plant macrofossils from fluvial, fluvio-deltaic and lacustrine sediments of the Gokarna Formation in the Besigaon, Mulpani, and Dhapasi sections in the Kathmandu Valley, Nepal were analyzed. The obtained plant macrofossils allowed us to reconstruct the late Pleistocene paleoenvironment in central Nepal, which was influenced strongly by the SW Indian monsoon system and tectonic movements of the Himalayas. In total, 102 taxa from 52 families were identified to genus or species levels. The dominance of Eurya, Ficus, Morus, Zizyphus, Stephania, Rubus, Quercus subgen. Cyclobalanopsis, Pyracantha, and Carpinus in the lower and middle plant macrofossil assemblages indicates influence of a warm climate. In the upper plant macrofossil assemblages, the higher contents of cooler climatic taxa such as Abies, Pinus, Picea smithiana, Tsuga dumosa, Taxus wallichiana, Quercus subgen. Lepidobalanus, and Betula indicate a climatic deterioration. The higher diversity and common occurrence of aquatic plants indicate rich wetland vegetation in the Kathmandu basin. The plant macrofossil analysis shows at least three cycles of climate fluctuation between warm and cool phases during the deposition of the Gokarna Formation between 53,170±820yrs. BP and 49,300±2100/1700yrs. BP. These cycles seem to be fairly local or regional, but this can also be correlated with the overall global cooling context in GISP2 oxygen isotope curve in the late Pleistocene.

Updated checklist of aquatic macrophytes from Northern Brazil

Field collection and herbaria data did not allow to quantify the diversity of aquatic plants from Northern Brazil, so we could not detect biogeographic patterns. Therefore, our objectives were to identify and quantify the aquatic macrophytes of North Brazilian states, analyzing herbaria data plataforms (SpeciesLink and Flora do Brasil). The checklist was produced by bibliographic search (articles published between 1980 and 2000), herbaria collections of the platforms SpeciesLink and Flora do Brasil and field expeditions, where we utilized asystematic sampling. We also analyzed the floristic similarity of aquatic macrophytes among Northern Brazil, wetlands of distinct Brazilian regions and the Neotropics. We recorded 539 species, of which 48 are endemic to Brazil. The states with highest number of species were Amazonas and Pará, independently on platform. The most represented families were Poaceae (89 species), Podostemaceae (55), Cyperaceae (50) and Fabaceae (47). We highlight the unprecedent richness of Podostemaceae, due to our own field collection efforts on favorable habitats, 25 species being endemic. Emergent and/or amphibious plants (515) were dominant in total species richness and were best represented in lotic habitats. We found significant differences in richness and floristics among states, obtained from the platforms. There is floristic similarity among Northern states and other Brazilian wetlands. In conclusion, we observed a rich aquatic flora in Northern Brazil, in spite of scarcity of records for Acre, Rondonia and Tocantins; we highlight the unprecedent number of endemic species of Podostemaceae (25) and contrasting richness between SpeciesLink and Flora do Brasil.

Poor ecological quality of urban ponds in northern England: causes and consequences

The value of ponds in urban areas historically has been overlooked. While some recent studies have described considerable biodiversity in urban areas, it is unclear as to how far this extends to different urban habitats. The aims of this study were to determine the condition of 21 urban ponds in Bradford (northern England) and to quantify the connectivity of wetlands in the district. The study showed that macroinvertebrate and plant biodiversity was substantially lower than would be expected based on pristine reference sites. Of the 21 ponds surveyed, 15 were found to be classified as having very poor ecological quality, with 5 being classed as poor and just 1 was classed as moderate. The number of aquatic plant species found in the ponds ranged from 0 to 6 and the number of macroinvertebrate families found ranged from 4 to 13. It was suspected that the aquatic plant diversity was low due to management techniques such as the removal of emergent vegetation. The average distance to a wetland was found to be higher in urban areas (533 m) compared to rural areas (448 m) although this difference was small, which indicates that the low diversity found in urban ponds is likely due to habitat variables.

Italian Volcanic lakes: a diversity hotspot and refuge for European charophytes

Macrophytes are one of the most important components of primary producers in lacustrine environments. Charophytes represent the most threatened group of macrophytes and are included in many European Red-Lists. Thus, finding and preserving charophyte diversity hotspots is important for European macrophyte conservation strategies. Within the framework of a general project aimed at investigating aquatic plant diversity of Italian volcanic lakes (IVL), a field survey carried out in 2009-2010 recognized high charophyte diversity. Overall, 17 species of charophytes, which correspond to 50% of Italian stoneworts and 30% of the European species, were recorded. Nevertheless, only four IVL out of the nine lakes investigated can be considered Chara-dominated lakes. Three Chara-vegetation belts characterized the Chara dominated IVL, as in other pristine deep calcareous European lakes. A Chara aspera belt grew at a lower depth, followed by a Chara polyacantha belt at a medium depth and a Chara globularis dominated belt at a higher depth, up to the maximum growing depth. The most common species was Chara globularis, whereas seven species were rare. Sixteen of the 17 species found belong to the IUCN threatened categories throughout Europe. The most interesting taxa are Nitella hyalina, Nitella gracilis and Lychnothamnus barbatus. Nitella hyalina is extinct in Switzerland and Great Britain, critically endangered in the Balkans and in Germany. Nitella gracilis is extinct in Denmark and endangered in the Balkans, Sweden and Switzerland. The Lychnothamnus barbatus population found in Martignano is the only one known in Italy. Lakes Vico, Martignano, Bolsena and Bracciano host from 18% to 44% of European charophytes. The high number of species in each lake allows the selection of these lakes as European hotspots of charophyte diversity. Therefore, the IVL can be a reference system for the conservation of aquatic species that are typical of Italian and European deep lakes.

Loss detection of aquatic habitats in Italian volcanic lakes using historical data

Italian volcanic lakes represent an important hotspot of aquatic plant diversity. By comparing original data collected in 2009/10 with historical data, we detected species extinction and loss of habitats 3140 and 3150 (Habitats Directive 92/43/EEC). The speed of change detected claim for frequent monitoring and rapid management interventions.

Does water facilitate gene flow in spore-producing plants? Insights from the fine-scale genetic structure of the aquatic moss Rhynchostegium riparioides (Brachytheciaceae)

Hydrochory plays a key role in the maintenance, diversity and evolution of aquatic plants and has traditionally been thought to (i) decrease or erase patterns of isolation-by-distance, (ii) increase outbreeding, and (iii) result in a downstream increase of genetic diversity. These hypotheses, which are especially relevant in organisms with water-mediated fertilization and a high ability to disperse vegetatively, are tested here from fine-scale spatial analyses of genetic variation at both the haploid and diploid phases in the aquatic moss Rhynchostegium riparioides (Hedw.) Cardot. A substantial geographical partitioning of genetic variation was found at the scale of the river basin and indirect measures of dispersal point to an overall weaker dispersal ability of the moss diaspores than pollen or wind-dispersed seeds. These observations, as well as the high Fis observed at the diploid stage and the very close proximity of potential fathers of the heterozygous diploid genotypes, strongly challenge the hypothesis that water enhances sperm and diaspore-mediated gene flow. In R. riparioides, the severe dispersal limitations revealed by the spatial analyses of genetic structure suggest that shoot fragments rather than spores are involved in local dispersal, which is fully consistent with the low levels of genetic diversity observed within populations. Extremely limited routine dispersal by unspecialized vegetative diaspores, coupled with discrete episodes of local population extinctions and colonizations by spores, account for the absence of a downstream increase of genetic diversity. As a result, although spore-producing plants are typically seen as most efficient dispersers, and although streams are traditionally seen as dispersal corridors, severe limitations of clonal dispersal at the local scale and discrete opportunities of random spore dispersal and establishment among colonies, both explain why typical metapopulation processes also apply to aquatic mosses.