Antonio Ruggiero

Biodiversity and distribution patterns of freshwater invertebrates in farm ponds of a south-western French agricultural landscape

We assessed the importance for biodiversity of man-made farm ponds in an agricultural landscape in SW France lacking natural wetlands. The ponds were originally created to provide a variety of societal services (irrigation, visual amenity, water for cattle, etc.). We also assessed the environmental factors influencing invertebrate assemblages in these ponds. Only 18 invertebrate taxa out of 114 taxa occurring in the study area were common to ponds and rivers indicating that the contribution of farm ponds to freshwater biodiversity was potentially high. A Self-Organizing Map (SOM, neural network) was used to classify 36 farm ponds in terms of the 52 invertebrate families and genera they supported, and to specify the influence of environmental variables related to land-use and to pond characteristics on the assemblage patterns. The SOM trained with taxa occurrences showed five clusters of ponds, most taxa occurring only in 1–2 clusters of ponds. Abandoned ponds tended to support higher numbers of taxa, probably because they were allowed to undergo a natural succession. Nevertheless, abandoned ponds were also amongst the largest, so that it remained difficult to separate the effects of pond size and abandonment, although both factors were likely to interact to favour higher taxon richness. The invertebrate communities in the ponds appeared to be influenced mainly by widely acting environmental factors (e.g. area, regionalization of assemblages) with little evidence that pond use (e.g. cattle watering, amenity) generally influenced assemblage composition. Our results support the idea that agricultural landscapes containing man-made ponds make a significant contribution to freshwater biodiversity indicating that protection of farm ponds from threats such as in-filling and pollution can make a positive contribution to the maintenance of aquatic biodiversity. This added value for biodiversity should be considered when calculating the economic costs and benefits of constructing water bodies for human activities.

Farm ponds make a contribution to the biodiversity of aquatic insects in a French agricultural landscape

Manmade ecosystems provide a variety of resources that have strong economic values. We assessed the importance of 37 farm ponds for the biodiversity of Odonata in an agricultural landscape lacking natural wetlands in southwestern France. Farm ponds captured 40% of the regional species pool, including both common and rare species. The species assemblages were not correlated with pond use (e.g., cattle watering, duck farming, etc.) or to landscape variable. Species richness was correlated with pond area, suggesting that community diversity was primarily driven by autoecological processes. Farm ponds thus made a positive contribution to the maintenance of aquatic biodiversity. This added value for biodiversity should be considered when calculating the costs and benefits of constructing water bodies for human activities.

Influence of vegetation cover on the biological traits of pond invertebrate communities

Without human intervention, ponds progressively fill up with aquatic vegetation, so that the structure and age of the vegetal formations show great contrasts within a given set of water bodies. We hypothesized that the biological traits of pond invertebrate communities differed significantly among ponds having different vegetal formations. To test this hypothesis, we selected three neighbouring ponds showing a gradient of vegetation cover and type (sparse bryophytes on rocky substrata (pond 1), extensive submerged Chara beds (pond 2), aerial Typha stands (pond 3)), and we studied between-ponds variations in the combinations of species traits. Taxa biomass was monthly recorded in each pond over one year, to take into account species’ seasonality. Species traits were described using a fuzzy-coding method and a simultaneous analysis of the two matrices (co-inertia analysis) was used to investigate changes in biological trait composition. Biomass increased from pond 1 to pond 3, and was higher in vegetal than in muddy mesohabitats. Among 25 biological traits, 10 were significantly correlated to the distribution of samples: number of genera tions per year, cohort production interval, adult longevity, adult size, number of eggs per female, dispersal ability, dispersal mode, consumer level, ingested food type, and feeding group. Invertebrates in pond 1 species allocated much energy to reproduction, while in pond 3 resource use was favoured by larger body size, long-lived organisms, and a higher diversity of feeding groups. Our results suggest that the structure and age of the vegetal formation play role in selecting species traits related to population dynamics and feeding habits.

Nutrient Transient Storage by the Invertebrate Assemblage in Streams with Contrasting Nutrient Loads

Headwater streams account for most o f the channe1 1ength in lotic networks, are intimate1y connected with the terrestria1 mi1ieu and are biogeochemica1 hotspots (sensu McCLAIN et al. 2003) at the 1andscape scale. These headwaters can influence larger downstream ecosystems such as rivers, estuaries and even coastal waters through 1ongitudina1 linkage of 1ocal biogeochemica1 processes (ALEXANDER et al. 2000, MEYER & WALLACE 2001). During the transit from up1ands to oceans through 1otic networks, nutrients undergo multip1e cyc1es of uptake, bio1ogica1, chemica1 and physica1 storage and remineralization processes that can formally be described by the nutrient spira1ing concept (WEBSTER & PATTEN 1979, NEWBOLD et al. 1981 ). While recent research on stream nutrient dynamics mostly focused on pristine ecosystems, litt1e is known about human-altered streams. Whi1e we appreciate the ro1e of periphytic algae in nutrient cycling (MuLHOLLAND 1996) and begin to understand the consequences of microbia1 biofi1ms for ecosystem processes (BATTIN et al. 2003a), relative1y litt1e i s known about the immediate effects of invertebrates on whole-stream nutrient retention. Ihe aim o f this conceptual paper i s to p1ace benthic invertebrate consumers within the framework of stream nutrient dynamics in pristine and nutrientenriched situations.