The conservation status of athalassic lakes in New South Wales,Australia

To provide an overview for the State Pollution Control Commission of NSW, 102 lakes were visited throughout the state during the 1988–9 summer to ascertain their ecological condition. The sites chosen covered a spectrum of geomorphic types in approximate proportion to their perceived relative abundance. Field work concentrated on some physicochemical parameters and on zooplankton and littoral invertebrates. A summary of these features of the lakes of NSW is given.The most widespread problem is eutrophication, though for many lakes changes in trophic status could be part of wider changes in lakes since European settlement. A significant number of lakes suffer eroded shorelines and sedimentation. The introduced mosquito fish, Gambusia affinis, is associated with decreased diversity mainly in coastal lakes where also alien plants may be pestiferous. A few lakes in western areas have their flooding regime altered, while a number in the east are drained. With few exceptions there are no management programs to improve the conservation status of degraded lakes in NSW.     

Molecular diversity of soil basidiomycete communities in northern-central New South Wales, Australia

Basidiomycete communities were profiled using terminal RFLP (TRFLP) and amplified ribosomal DNA restriction analysis (ARDRA) approaches at seven field sites under differing land use in northern-central New South Wales (NSW), Australia. TRFLP data indicated greater basidiomycete species richness at sites with natural vegetation. Sixty-seven basidiomycete ARDRA-types were detected. Various putatively ectomycorrhizal fungi were detected at all sites with native vegetation. Most ectomycorrhizal taxa had affinities to the genus Tomentella, while two Pisolithus taxa and putatively ectomycorrhizal Cantharellales taxa were also detected. Although soils under woodland or grassland communities supported a range of putatively saprotrophic taxa, only members of the Ceratobasidiales were detected in soils under agricultural land use. This study is the first investigation of fungal communities in soils of northern-central NSW, Australia.     

A new genus of alonine chydorid cladocerans from athalassic saline waters of New South Wales,Australia

A new genus (Celsinotum) and three new species are described from intermittent athalassic saline waters in the Paroo region of northwest New South Wales, which have TDS varying from 2.8 to 14.0 g l^-1. The species are large, thin, high-bodied, and have a pronounced keel on the shell but not on the head. The marginal armature of the postabdomen consists entirely of clusters of fine spinules. Most strikingly, the males have 12 terminal aesthetascs on the antennule, and in addition have 5 or 6 equally long accessory aesthetascs arising laterally. Alona taraporevalae from India presumably also has this character, but a comparison of the two species indicates they are not closely related.The taxa bear a general similarity to Alona diaphana from Australia, but a close comparison shows that they, too, are unrelated. A. diaphana has a prominent spine arising from the basal segment of the antennal exopod, the two IDL (= inner distal lobe) setae on trunklimb I have a much coarser setulation distally than in Celsinotum, and on the postabdomen the postanal portion is always considerably longer than the anal, and the marginal armament consists of single setae distally and clusters of only a few setae proximally. Besides, the species is smaller, the body is wider and less high, and the shell although weakly ridged is not keeled. The male has 9 terminal aesthetascs and no accessory lateral ones.In athalassic saline waters around the world the number of anomopod species declines negative exponentially in relation to salinity. Many of the freshwater species persist into the 3 to 10 range without any difficulty, some occur in abundance up to 30, and a few even extend into the hypersaline range. Chydorids, though, except for a very few species, do not tolerate salinities higher than about 15, and none of them seem adapted to these salinities and confined to them. Celsinotum, though, possibly is so adapted, as it did not occur in other basins of the region with lower salinities, and it is not presently known from other regions.Having different but closely related congeneric taxa in nearby lakes of the same region seems surprising. The three species of Celsinotum are very similar in most details of morphology, but they vary significantly in body proportions, the number of denticle clusters on the postanal portion of the postabdomen, and in such seemingly minor details as the amount of expansion of the labral plate. Such taxonomic differentiation, which has been observed in other groups of organisms as well, is believed to have arisen from the extreme temporal isolation of these waterbodies, those in the Paroo region normally containing water only once every 5 to 20 years.     

Dissolved and particulate organic carbon in two wetlands in southwestern New South Wales,Australia

Concentrations of dissolved (DOC) and particulate organic carbon (POC) in two billabong wetlands (Murrumbidgil Swamp and Lake Merrimajeel) in inland temperate Australia were positively correlated with leaf fall from river red gums Eucalyptus camaldulensis (DOC and POC in Murrumbidgil Swamp), phytoplankton productivity (DOC in Murrumbidgil Swamp, DOC and POC in Lake Merrimajeel), and with biomass of aquatic macrophytes (DOC in the two wetlands). DOC correlated with water level at both sites. Mean concentrations of DOC (Murrumbidgil Swamp, 36.0 gm^-3; Lake Merrinmajeel, 27.5 g m^-3) and POC (15.0 g m^-3; 15.5 g m^-3) were high compared with other water bodies worldwide, although average for wetlands. The relatively high concentrations of DOC and POC in the study wetlands appear to be the result of their high rates of plant production, and input of leaves from river red gums.     

Influence of arbuscular mycorrhizae and Rhizobium on nutrient content and water relations in drought stressed alfalfa

The objective of this research was to study the effect of drought on nutrient content and leaf water status in alfalfa (Medicago sativa L. cv Aragón) plants inoculated with a mycorrhizal fungus and/or Rhizobium compared with noninoculated ones. The four treatments were: a) plants inoculated with Glomus fasciculatum and Rhizobium meliloti 102 F51 strain, (MR); b) plants inoculated with R. meliloti only (R); c) plants with G. fasciculatum only (M); and d) noninoculated plants (N). Nonmycorrhizal plants were supplemented with phosphorus and nonnodulated ones with nitrogen to achieve similar size and nutrient content in all treatments. Plants were drought stressed using two cycles of moisture stress and recovery. The components of total leaf water potential (osmotic and pressure potentials at full turgor), percentage of apoplastic water volume and the bulk modulus of elasticity of leaf tissue were determined. Macronutrient (N, P, K, Ca, S and Mg) and micronutrient (Co, Mo, Zn, Mn, Cu, Na, Fe and B) content per plant were also measured. Leaves of N and R plants had decreased osmotic potentials and increased pressure potentials at full turgor, with no changes either in the bulk modulus of elasticity or the percentage of apoplastic water upon drought conditions. By contrast, M and MR leaves did not vary in osmotic and turgor potentials under drought stress but had increased apoplastic water volume and cell elasticity (lowering bulk modulus). Drought stress decreased nutrient content of leaves and roots of noninoculated plants. R plants showed a decrease in nutrient content of leaves but maintained some micronutrients in roots. Leaves of M plants were similar in content of nutrients to N plants. However, roots of M and MR plants had significantly lower nutrient content. Results indicate an enhancement of nutrient content in mycorrhizal alfalfa plants during drought that affected leaf water relations during drought stress.     

Host plant differences in arbuscular mycorrhizae: Extra radical hyphae differences between an invasive forb and a native bunchgrass

Arbuscular mycorrhizae affect grassland plant community composition and host plant nutrient uptake, and can mediate shifts in competitive outcome between plant species. Centaurea maculosa, an invasive forb from Eurasia, dominates more than 4 million hectares in the Rocky Mountain region of North America. We examined the role of AM for phosphorus (P) acquisition from a distant source for C. maculosa and Festuca idahoensis, a native bunchgrass. Plants were grown individually in pots divided by a barrier that either excluded plant roots and AM hyphae, or only plant roots. In the half of the pot without a plant, 1 of 3 P treatments was applied: no P, phosphate rock (PR) or triple superphosphate (TSP), applied at a rate of 144 mg P kg^–1 soil. After 14 weeks of growth, C. maculosa was twice as large as F. idahoensis, and neither species biomass was affected by barrier type. Phosphorus fertilizer, and especially PR, moved across the barrier to the plant side of the pot. Tissue P concentration for C. maculosa was highest with the PR treatment, and was not affected by the barrier type. In contrast, F. idahoensis tissue P concentration did not vary with barrier or P treatments. There was more AM extra radical hyphae (ERH) associated with C. maculosa than F. idahoensis, suggesting that C. maculosa provides more carbon for the AM fungi, resulting in greater ERH production, ERH soil exploration and potential for soil nutrient pool exploitation. Although not tested in this study, differences between host plants may be the result of different physiological characteristics of the host plant or differences in AM fungal species that colonize the invader, with different fungal species accessing P from different distances.     

Halotolerance of the oyster predator, Imogine mcgrathi, a stylochid flatworm from Port Stephens, New South Wales, Australia

The stylochid flatworm, Imogine mcgrathi was confirmed as a predator of the pteriid oyster Pinctada imbricata. Occurring at an average of 3.2 per oyster spat collector bag, the flatworms were found to consume oysters at a rate of 0.035–0.057 d^–1 in laboratory trials. Predation was affected by flatworm size with larger worms capable of consuming larger oysters and of consuming greater dry weights of oyster flesh. Irrespective of flatworm size, predation was generally confined to oysters less than 40 mm in shell height. Although all predation occurred at night, shading flatworms during the day did not significantly increase the rate of predation, but there were significant increases in the dry weight of oyster meat consumed. As a means of controlling flatworm infestations, salt, brine baths (250 g kg^–1) and freshwater baths were effective in killing I. mcgrathi. The ease of use of hyper- or hyposaline baths then encouraged assessments of I. mcgrathi halotolerance. The flatworms were exposed to solutions ranging in salinity from 0 to 250 g kg^–1for periods of from 5 min to 3 h. Despite showing both behavioural and physiological signs of stress, I. mcgrathi survived the maximum exposure time of 3 h at salinities in the range 7.5–60 g kg^–1, inclusive. Beyond this range, the duration of exposure tolerated by flatworms decreased until 0 and 250 g kg^–1, at which the flatworms no longer survived the minimum tested exposure of 5 min. Thus, despite the significant impact of other stylochids on commercial bivalves, at their current prevalence, I. mcgrathi can be controlled by exposing them to hyper- and hyposaline baths for the culture of P. imbricata in Port Stephens, NSW, Australia.     

Soil and vegetation response to thinning White Cypress Pine (Callitris glaucophylla) on the North Western Slopes of New South Wales, Australia

Dense White Cypress Pine (Callitris glaucophylla J. Thompson and L.A.S. Johnson) regrowth occurs frequently across previously cleared landscapes in New South Wales (NSW), and is thought to adversely affect agricultural production and to cause land degradation. The NSW Native Vegetation Act (2003) requires that management of native vegetation including pre-1990 regrowth must ‘improve or maintain’ site condition, yet there is currently limited information regarding techniques for the optimum management of C. glaucophylla in this regard. We conducted a preliminary study to examine floristic composition, soil condition (to 50 cm) and carbon storage under ‘Dense’ (dense regrowth), ‘Thinned’ (dense regrowth thinned 2000/2001) and ‘Un-colonised’ (pasture not yet recolonised by C.␣glaucophylla) plots on private lands in NSW. Reduced tree density from thinning resulted in increased biomass of the remaining individual trees. Un-colonised plots had significantly more groundcover than thinned plots, which had significantly more groundcover than dense plots. Differences in plant diversity however, were explained by site factors rather than land use. Soils in the dense plots were the most acid but soil pH was significantly higher in thinned plots and pH was highest in soil of the un-colonised plots. Mean values for carbon, nitrogen, sulphur and extractable phosphorus varied among sites, although each were significantly more abundant in the mineral soil of dense and thinned plots compared with un-colonised plots, suggesting that thinning had had a minimal effect on the soil parameters assessed. Accounting for all site components, site carbon storage was significantly higher in dense and thinned plots compared with un-colonised plots due to elevated levels of soil and litter carbon as well as the presence of trees. The results indicate that thinning dense C. glaucophylla can maintain and (by some measures) improve site condition. However, given the variability in some of the parameters assessed, further study across a wider range of soil types and rainfall gradients is proposed.     

Mycotrophy of Annona cherimola and the morphology of its mycorrhizae

The mycotrophic character of Annona cherimola (Magnoliales), a tropical/subtropical plantation crop of interest, is described for the first time. This crop seems to depend on mycorrhizae (arbuscular) for optimal growth, with Glomus deserticola being the most effective endophyte tested. Study of the morphology of the arbuscular mycorrhizae in Annona roots showed exclusively intracellular hyphal development, with cell-to-cell fungal passage and an abundance of arbuscules and coiled hyphae within cells. Intercellular distributive hyphae were not observed. The morphology and the pattern of spread of the mycorrhizal colonization were similar for the different endophytes involved and appeared to be dependent on the host root. Such features of mycorrhizal colonization are characteristic of host species lacking intercellular air channels and have been described for some species of ecological interest, but they are not commonly noted in the mycorrhizal literature, especially that dealing with crop species. Some ecophysiological consequences of this pattern of colonization are discussed.     

The interaction of rockphosphate,Bradyrhizobium, vesicular-arbuscular mycorrhizae and phosphate-solubilizing microbes on soybean grown in a sub-Himalayan mollisol

A factorial design 2³ × 4 with two levels of Mussorie rockphosphate (RP) with or without vesicular-arbuscular mycorrhizal (VAM) fungi and Bradyrhizobium japonicum, and four treatments of phosphate-solubilizing microbes (PSM) Pseudomonas striata, Bacillus polymyxa, Aspergillus awamori was employed using Patharchatta sandy loam soil (Typic Hapludoll). The observations included mycorrhization, nodulation, grain and straw yield, N and P uptake, available soil P and the PSM population in the soil after crop harvest. Inoculation with endophytes alone caused about 70% root colonization. Addition of rockphosphate or inoculation with PSM, except B. polymyxa, stimulated root infection of native as well as introduced VAM endophytes. Application of RP or inoculation with Bradyrhizobium japonicum, mycorrhizal fungi or phosphate-solubilizing microorganisms significantly increased nodulation, N uptake, available soil P and the PSM population in the soil after the crop harvest. The grain and straw yields did not increase following RP addition or mycorrhizal inoculation but increased significantly after inoculation wit Bradyrhizobium or PSM. In general, the application of RP, Bradyrhizobium, VAM and PSM in combinations of any two or three resulted in significant increases in nodulation, plant growth, grain yield and uptake of N and P. Among the four factor interactions, rockphosphate, Bradyrhizobium and P. striata in the absence of VAM resulted in maximal nodulation, grain and straw yields and N uptake by soybean. The highest P uptake by soybean grain was recorded with Bradyrhizobium and A. awamori in the absence of rockphosphate and VAM. Generally, available soil P and PSM population after crop harvest were not significantly increased by the treatment combinations giving the maximal uptake of nutrients. However, they increased significantly in response to PSM, which produced no significant increase in total uptake of nutrients.Research paper no. 7498     

Biology, distribution and host-range of the sawfly,Lophyrotoma zonalis (Hym. pergidae), a potential biological control agent for the paperbark tree,Melaleuca quinquenervia

Since its introduction into southern Florida at the beginning of this century, the Australian paperbark tree,Melaleuca quinquenervia (Cav.) S. T. Blake, has become a major economic and environmental pest. A project to develop biological control agents for this tree in Australia began in 1986. Among a number of potential agents, a defoliating sawfly,Lophyrotoma zonalis (Rohwer) (Hymenoptera: Pergidae), was selected for further study. The larvae of this sawfly are conspicuous defoliators ofMelaleuca trees in northern Queensland. We collected these sawflies from Cairns to Mackay in northern Queensland, and they are also known from the Northern Territory and New Guinea. The life-cycle from egg to adult takes about 12 weeks. The egg, larval and pupal stages are parasitized by dipteran and hymenopteran parasites. We conducted 2234 larval no-choice feeding tests on 46 plant species from 20 families. Although feeding occurred on 35 of these plant species,M. quinquenervia and its close relative,M. leucadendra (L.) L., were preferred. In oviposition tests, larvae only emerged from egg cases laid onM. quinquenervia andM. leucadendra. Our extensive field surveys of nearly 70 tree species foundL. zonalis eggs and larvae only on several closely relatedMelaleuca species. The potential effectiveness of this sawfly as a biocontrol agent is discussed and estimated using the Goeden-Harris scoring system. Quarantine studies of this insect began in Florida in early 1994.     

The effect of phosphorus on nodule formation and function in the Casuarina-Frankia symbiosis

A study was conducted to investigate the effects of phosphorus on nodule formation and function in the Casuarina-Frankia symbiosis. The effects of P on growth and survival of Frankia in the rhizosphere was assessed by examing Frankia growth and survival in flasks of basal nutrient solution. There was no growth in the nutrient solution during the experimental period. However, the viability of Frankia in the nutrient solution without P supply was half that of the initial level, whereas, with P supply, there was only a minor decline during the first week. In a growth pouch experiment, supplying P increased plant and nodule growth, irrespective of P status of the inoculant Frankia culture. There were no effects of P status on any growth or nodulation parameters measured when the inoculants had been standardized on the basis of viability. In a split root experiment, Frankia inoculation and application of P together or separately did not cause any significant difference. This suggests that growth and nodulation respond only to total P supply. Increasing P from 0.1 to 10 M significantly increased plant growth but not N concentrations. Both nitrogen-fixation and nitrate supported growth were strongly increased as P increased from 0.1 to 1.0 M. This study indicates that P deficiency limits the growth of host plants more severely than nitrogen fixation processes and P deficiency on nodulation and symbiotic nitrogen fixation in Casuarina cunninghamiana operated indirectly via reducing host plant growth.     

Structure and histochemistry of mycorrhizae synthesized between Arbutus menziesii (Ericaceae) and two basidiomycetes,Pisolithus tinctorius (Pisolithaceae) and Piloderma bicolor (Corticiaceae)

Arbutoid mycorrhizae were synthesized in growth pouches between Arbutus menziesii Pursch. (Pacific madrone) and two broad host range basidiomycete fungi, Pisolithus tinctorius (Pers.) Coker and Couch and Piloderma bicolor (Peck) Jülich. P. tinctorius induced the formation of dense, pinnate mycorrhizal root clusters enveloped by a thick fungal mantle. P. bicolor mycorrhizae were usually unbranched, and had a thin or non-existent mantle. Both associations had the well-developed para-epidermal Hartig nets and intracellular penetration of host epidermal cells by hyphae typical of arbutoid interactions. A. menziesii roots developed a suberized exodermis which acted as a barrier to cortical cell penetration by the fungi. Ultrastructurally, the suberin appeared non-lamellar, but this may have been due to the imbedding resin. Histochemical analyses indicated that phenolic substances present in epidermal cells may be an important factor in mycorrhiza establishment. Analyses with X-ray energy dispersive spectroscopy showed that some of the granular inclusions present in fungal hyphae of the mantle and Hartig net were polyphosphate. Other inclusions were either protein or polysaccharides.     

A new genus and species of dalodesmid millipede from New South Wales,Australia (Diplopoda,Polydesmida, Dalodesmidae)

Cernethia inopinata gen. n., sp. n. is described from highland New South Wales. Like other dalodesmids the new species has numerous sphaerotrichomes on the legs of adult males, but Cernethia inopinata sp. n. shares several character states with Tasmanian species in the genera Noteremus Mesibov, 2009, Paredrodesmus Mesibov, 2003 and Procophorella Mesibov, 2003, which lack sphaerotrichomes and have not yet been assigned to family within the suborder Dalodesmoidea.     

Differences in above- and below-ground responses to ozone between two populations of a perennial grass

Our study examined the influence of elevated ozone levels on the growth and mycorrhizal colonization of two populations of Elymus glaucus L. (blue wildrye). We hypothesized that ozone would reduce carbon availability to the plants, particularly below ground, and would affect mycorrhizal colonization. Because of the wide geographic range of E. glaucus, two populations of plants were selected from areas of contrasting ozone histories to examine intraspecies variation in response to ozone. Two populations of E. glaucus (southern California versus northern California) exposed in a factorial experiment involving ozone, mycorrhizal inoculation with Glomus intraradices Schenck and Smith, and plant source population. Ozone had a subtle effect on leaf area and number of tillers but did not affect overall root:shoot ratio in either population. The impact of ozone on above-ground growth characteristics was most pronounced in the southern population that came from a high-ozone environment, while below-ground responses such as reduced arbuscular colonization was most pronounced in the northern population which originated in a low-ozone environment. Further analysis of soil characteristics from the northern population of plants revealed a significant reduction in active soil bacterial biomass and an increase in total fungi per gram dry weight soil, suggesting a possible role for ozone in altering soil processes. Whether or not population differences in response to ozone were due to genetic shifts resulting from prior ozone remains to be determined. However, these subtle but important differences in population response to ozone above- and below-ground have significant implications in any attempt to generalize plant response, even within a species. Future research efforts need to include better characterization of intraspecific variation in response to ozone as well as possible adaptive strategies that may result from chronic ozone exposure.     

The role of natural enemies in controllingIcerya purchasi in South Australia

The obscure occurrence of the cottony-cushion scaleIcerya purchasi Maskell in its native country Australia is generally attributed to its natural enemies. Twelve natural-enemy-exclusion experiments were conducted at monthly intervals to confirm the role of natural enemies. Each experiment had uncaged, open-caged, and caged treatments. The natural enemies were active throughout the year. The percentage of scales surviving to adults in the cages was significantly higher than in the open-caged treatments, except the April (first) cohort. In both open-caged and uncaged treatments, the percentage of scales surviving to adults was similar and matched the changes in the numbers of natural enemies, thus confirming their importance in controllingI. purchasi in South Australia.      

Response of heart rate and cloacal ventilation in the bimodally respiring freshwater turtle, Rheodytes leukops, to experimental changes in aquatic PO2

Changes in heart rate (f _H) and cloacal ventilation frequency (f _C) were investigated in the Fitzroy turtle, Rheodytes leukops, under normoxic (17.85 kPa) and hypoxic (3.79 kPa) conditions at 25°C. Given R. leukops’ high reliance on aquatic respiration via the cloacal bursae, the objective of this study was to examine the effect of varying aquatic PO₂ levels upon the expression of a bradycardia in a freely diving, bimodally respiring turtle. In normoxia, mean diving f _H and f _C for R. leukops remained constant with increasing submergence length, indicating that a bradycardia failed to develop during extended dives of up to 3 days. Alternatively, exposure to aquatic hypoxia resulted in the expression of a bradycardia as recorded by a decreasing mean diving f _H with increasing dive duration. The observed bradycardia is attributed to a hypoxic-induced metabolic depression, possibly facilitated by a concurrent decrease in f _C. Results suggest that R. leukops alters its strategy from aquatic O₂ extraction via cloacal respiration in normoxia to O₂ conservation when exposed to aquatic hypoxia for the purpose of extending dive duration. Upon surfacing, a significant tachycardia was observed for R. leukops regardless of aquatic PO₂, presumably functioning to rapidly equilibrate blood and tissue gas tensions with alveolar gas to reduce surfacing duration.     

Arbuscular mycorrhizae formed by Penicillium pinophilum improve the growth, nutrient uptake and photosynthesis of strawberry with two inoculum-types

Penicillium pinophilum was isolated from the soil in a commercial strawberry field. The strain readily formed arbuscular mycorrhizae (AM) with the roots of strawberry 'Zoji' (Fragaria x ananassa Duch. CV.) when plants were inoculated with either fresh cultured hyphae or root/soil mixtures. Fresh hyphae, however, resulted in higher amounts of colonization than root/soil inoculum. Compared with uninoculated strawberries, inoculation increased plant dry weight by 31%, as well as nitrogen content (47%), phosphorus content (57%), and photosynthetic rate (71%). AM inoculation also shortened the blossom and ripening date by 3 and 4 days, respectively. This is the first report of a P. pinophilum strain resulting in mycorrhiza with strawberry roots. The significant advantages of this strain are that it is easy to culture and inoculation of plants results in significant growth benefits that may be useful in strawberry production.     

Morphological plasticity of a spreading aquatic macrophyte,Ranunculus peltatus,in response to environmental variables

Ranunculus peltatus Schrank is an aquatic macrophyte spreading in northeastern France. As with other Ranunculus species, its growth demonstrates considerable plasticity. A preliminary understanding of its development and precise adaptive strategy is possible through functional ecology. The present study took morphological traits into account in order to analyse R. peltatus' development and morphological plasticity in relation to environmental parameters. During the five-month growing season, field measurements of ten different morphological traits were performed monthly at twelve sampling sites presenting various physical and chemical characteristics. Three overall growth stages occurred between April and August 2000: a stage of elongation of the main stem, a stage of branching and flowering and a stage of decline associated with vegetative dispersion. The sampling sites were defined according to environmental parameters and divided into three groups corresponding to three morphologically different R. peltatus populations. Plants in upstream, nutrient-poor, undisturbed sites were small and achieved little sexual reproduction. Plants in nutrient-rich, undisturbed sites had long shoots and were branched. Plants in weakly shaded, disturbed sites were small but produced many flowers. Correlations between morphological traits and environmental parameters showed significant relationships between chemical parameters and some characteristic vegetative growth traits. Physical environmental parameters were found to be less well correlated with morphological traits than the chemical parameters. The phenology and morphological plasticity of R. peltatus confer competitive advantages that could explain its ability to spread in some circumstances. Finally, the previous classification of R. peltatus as a Grime CSR species is discussed in relation to its plasticity. According to its morphological characteristics, R. peltatus tended indeed to adopt a C-strategy in nutrient-rich undisturbed sites, a S-strategy in nutrient-poor undisturbed sites and a R-strategy in disturbed sites.