Victor S. Saito

Should phylogenetic and functional diversity metrics compose macroinvertebrate multimetric indices for stream biomonitoring

AbstractThe idea behind multimetric indices is to integrate information from several metrics to provide a general classification of water bodies without losing the particularities of each individual metric. Historically, multimetric indices use information on richness, taxon sensitivity, and taxonomic diversity. Recently, functional and phylogenetic diversity proved to capture different dimensions of biodiversity. Here we asked if these new metrics provide complementary information to classical metrics and should be included in multimetric indices. We used an index construction protocol based on statistical filters to test candidate metrics for range, sensitivity, and redundancy. We used macroinvertebrate data from streams located in a Savanna region of Brazil, encompassing a gradient of impact, to test our ideas. Of 41 candidate metrics, functional dispersion of functional diversity, mean nearest neighbor distance of phylogenetic diversity, and four classical metrics passed the filter selection composing the final multimetric index. Our results indicated that functional and phylogenetic diversity metrics indeed responded to environmental impact and complemented the information provided by classical metrics. We suggest that future indices should consider including new metrics of functional and phylogenetic diversity to properly monitor multiple dimensions of biodiversity.

Characterization of galls, insect galls and associated fauna of Ecological Station of Jataí (Luiz Antônio, SP)

This is the first study about galls, gall makers and associated fauna of the Ecological Station of Jatai. Galls are plant structures formed by abnormal growth of cells, tissues or organs induced by several organisms, as fungous, nematoids and insects. Five areas of the conservation unity, two in the phytophysionomy of cerrado in regeneration and three in the cerradao area were studied, totalizing 69 morphotypes of galls on 41 host species from 24 families. This is the first record of Annonaceae as the richest family in morphotypes in Brazil; 34 gall makers and associated fauna were identified, which 23 Diptera (67.4%), eight Hymenoptera (23.5%), two Hemiptera (5.8%) and one Thysanoptera (2.9%). Were described 41 new morphotypes of gall and made the first characterization of gall on Maprounea guianensis Aubl., Acosmium subelegans (Mohlenbr.) Yakovlev., Strychnosbicolor Progel, Eriotheca gracilipes K. Schum., Stryphnodendron obovatum Benth., Broyesum gaudichaudii Trecul, Psychotria suterella Mull. Arg., Psychotria trichophora Mull. Arg. and Serjania erecta Radlk.

Phylogenetic clustering among aggressive competitors: evidence from odonate assemblages along a riverine gradient

Studies on phylogenetic community ecology usually infer habitat filtering when communities are phylogenetically clustered or competitive exclusion when communities are overdispersed. This logic is based on strong competition and niche similarity among closely related species—a less common phenomenon than previously expected. Dragonflies and damselflies are good models for testing predictions based on this logic because they behave aggressively towards related species due to mistaken identification of conspecifics. This behavior may drive communities toward phylogenetic overdispersion if closely related species frequently exclude each other. However, phylogenetically clustered communities could also be observed if habitat filtering and/or competitive asymmetry among distantly related species are major drivers of community assembling. We investigated the phylogenetic structure of odonate assemblages in central Brazil in a watershed characterized by variations in stream width, vegetation cover, aquatic vegetation, and luminosity. We observed general clustering in communities according to two indices of phylogenetic structure. Phylogenetic beta diversity coupled with Mantel tests and RLQ analysis evidenced a correlation between the riverine gradient and phylogenetic structure. Larger rivers with aquatic vegetation were characterized by anisopterans, while most zygopterans stayed in small and shaded streams. These results indicate niche conservatism in Odonata habitat occupancy, and that the environment is a major influence on the phylogenetic structure of these communities. We suggest that this is due to clade-specific ecophysiological requirements, and because closely related species may also have competitive advantages and dominate certain preferred habitats.

How does leaf litter chemistry influence its decomposition and colonization by shredder Chironomidae (Diptera) larvae in a tropical stream

The nutritional quality of leaf litter can influence shredder chironomid larvae activities and affect leaf litter decomposition in tropical streams. The invasion of riparian areas by exotic plants may alter the nutritional quality of allochthonous material in streams, which would influence litter decomposition in these systems. We carried out an in situ experiment to verify the relationship between the initial leaf litter chemistry of two invasive plants (Hedychium coronarium and Pteridium arachnoideum) and a native one (Magnolia ovata) and the shredder chironomid larvae density and decomposition rates in a tropical stream. We found differences in the initial leaf litter chemistry and mass loss between leaf litter species. Differences in leaf litter chemistry influenced the colonization behavior by chironomid larvae. Larval densities differed among litter species, both taxonomically and functionally. The density of shredders was similar between M. ovata and H. coronarium, although they were colonized by different taxa: Endotribelos was more abundant in M. ovata and Stenochironomus in H. coronarium. P. arachnoideum was colonized by fewer shredders probably due to its high secondary compounds and lignin concentration. The invasion of riparian areas by exotic plants can alter the colonization of chironomid shredder assemblages and therefore the decomposition rates in aquatic systems.

Taxonomic composition and feeding habits of Chironomidae in Cerrado streams (Southeast Brazil): impacts of land use changes

The Chironomidae family is the most abundant and diverse member of the benthic community in streams, yet their identification is still neglected in many papers. It is considered a family tolerant to environmental impacts and with homogeneous feeding habit. AIM: To compare the richness, abundance and taxonomic composition of Chironomidae in Cerrado streams under different land uses as well as the feeding habit differences between genera of reference areas, sugar cane culture and pasture. METHODS: We selected seven streams in each land use and sampled six units using Surber sampler. The material was transported live for laboratory processing. RESULTS: Our results showed no significant differences in abundance and richness of Chironomidae among different land use, but we observed greater average values of abundance and richness in streams impacted by pasture. We found a distinct taxonomic composition between reference streams and impacted streams, both sugar cane and pasture. Stenochironomus was the most representative genus in reference areas, while Parametriocnemus was in sugar cane culture and Tanytarsus in pastures. The only statistically different feeding pattern found were between Cerrado streams and sugar cane for plant tissues, reflecting the greater abundance of Stenochironomus in Cerrado and among Cerrado streams and pasture for microalgae. CONCLUSIONS: We conclude that the conversion of natural areas in monocultures and pastures directly impact streams by modifying the taxonomic structure of Chironomidae. In contrast we did not observe a clear change in feeding patterns, because in all streams the diet pattern was mostly detritivorous.

Macroinvertebrates under stochastic hydrological disturbance in Cerrado streams of Central Brazil

ABSTRACT. In the Cerrado vegetation, where the seasonal is well defined, rainfall has an important role in controlling the flow of streams and consequently on the structure of macroinvertebrates community. Despite the effects of rainfall associated with seasonality are well studied, little is known about the effects of stochastic rains on the community. In the present study we evaluated the structure and faunal composition of four first-order streams in Central Brazil during the dry season in two years, with and without stochastic rains. Community sampling was done by colonization of boards of high density polyethylene (HDPE), removed after one month submerged in streams. Analysis of Variance (ANOVA) performed indicated no difference in rarefied richness between the two periods, different from numeric density of organisms that was higher in the period without disturbance; moreover, the Detrended Correspondence Analysis (DCA) revealed differences in faunal composition between the two periods. Our results indicate that stochastic rainfall is an important factor in structuring the macroinvertebrates community in studied region.

Evidence of species sorting driving aquatic beetles associated with woody debris in a transitional region between Cerrado and Atlantic Forest biomes

We investigated (1) the variation of both species composition and species relative abundances of aquatic beetles associated with submerged woody debris in a transitional region between Cerrado (Brazilian savannah) and Atlantic Forest biomes; and (2) which assembling processes are more associated with the observed patterns, species sorting or mass effects. We hypothesized that the marked differences between Cerrado and Atlantic Forest streams regarding vegetation composition and structure would produce different environmental conditions for stream beetle faunas assembling. We used spatial explicit multivariate techniques to analyze whether metacommunity patterns were more associated with environmental variables, indicating a major role of species sorting, or with spatial variables, indicating intense dispersal. We found distinct communities within each biome in terms of both changes in taxonomic composition and species relative abundance driven by environmental factors. Biome type, a regional scale variable, and variation in dissolved oxygen levels, a local scale variable, were the best explanatory variables of variation in metacommunity structure. We did not find any evidence of the influence of processes related to the spatial configuration of streams. Altogether our results pointed to species sorting structuring saproxylic beetles assemblages patterns.

Egg-laying traits reflect shifts in dragonfly assemblages in response to different amount of tropical forest cover

Oviposition site selection by aquatic insects is usually influenced by both aquatic and terrestrial cues. Landscape changes (e.g. native vegetation loss) can affect the level of the reproductive success in aquatic insects, changing local species composition and richness. We investigate whether forest cover loss around streams influences the number of species with exophytic (species which lay eggs directly on the water surface), endophytic (species which lay their eggs directly into plant tissue), or epiphytic (species which lay eggs on the exposed surface of rocks, leaves, trunks or other substrates protruding from the stream surface) oviposition behaviour in dragonfly assemblages. We sampled adult dragonflies in 116 streams in a Neotropical savanna region in Brazil. The relationship between species richness for each behavioural category, and the proportion of forest cover around the streams, was tested using regression analysis. We collected 2413 dragonfly (Anisoptera and Zygoptera) individuals, belonging to 8 families, 30 genera, and 63 species. Of these, 25 species were classified as exophytic, 28 as epiphytic, and 10 as endophytic. Our results show that the number of species with exophytic or epiphytic behaviour was strongly related to riparian forest loss. Forest loss changes the habitat, and here, specifically changes site suitability for oviposition. We highlight the importance of using behavioural traits as a bioindicator tool for the assessment of anthropogenic impacts on tropical forest.

Distinct responses of Copepoda and Cladocera diversity to climatic, environmental, and geographic filters in the La Plata River basin

The distribution of freshwater cladocerans and copepods and the drivers of beta diversity along La Plata basin were studied. We propose that local environmental conditions, dispersal limitation, and climate affect cladocerans and copepods differently owing to their variances in terms of life strategies. We calculated beta diversity using four dissimilarity metrics, and also the relative importance of spatial, environmental, and climatic variables by partitioning variance and forward selection procedure coupled with a partial redundancy analysis. Beta diversity patterns were characterized by a high turnover in the subbasins and a small contribution of nestedness. Forward selection evidenced the influence of total nitrogen and total suspended matter for both copepods and cladocerans, suggesting a strong role of eutrophication in controlling their turnover, but spatial distance, precipitation, and mean temperature of winter were related only to copepods. The last one suggests a likely role of geographic isolation driving speciation and endemism in Copepoda and reinforces the strong effect of climatic variation resulting in the high endemism patterns one finds in the Neotropical region.