Responses of riffle beetle assemblages to deforestation in a semi-deciduous Atlantic Forest remnant.

Deforestation affects freshwater assemblages since aquatic organisms are dependent on the structure of the riparian vegetation. To investigate the responses of riffle beetles (Elmidae) to deforestation, this study assessed the structure of riffle beetle assemblages found in streams running through a large and well-preserved semi-deciduous Atlantic Forest remnant in Southern Brazil and in nearby deforested areas. Additionally, the effects of different substrate types (litter and stone) on the assemblages were assessed. Riffle beetle assemblages showed a remarkably distinct structure between forested and deforested areas. Lower abundance occurred in deforested streams. Indicator genera of forested streams were detected (e.g.,Macrelmis and Microcylloepus), while a generalist genus (Heterelmis) predominated in deforested streams. Substrate type did not affect the composition of riffle beetle genera, although higher abundance was found in litter. Our results are likely associated with changes in the vegetation type and levels and quality of allochthonous material input between forested (native and higher levels) and deforested (exotic and lower levels) streams, which are directly linked to the feeding habits of riffle beetles. Thus, our study reveals an interesting potential of riffle beetles as indicators of stream ecological integrity in semi-deciduous areas of the Atlantic Forest biome.

The influence of natural and anthropic environmental variables on the structure and spatial distribution along longitudinal gradient of macroinvertebrate communities in southern Brazilian streams.

Southern Brazilian rivers and streams have been intensively affected by human activities, especially agriculture and the release of untreated domestic sewage. However, data about the aquatic macroinvertebrates in these streams are scarce and limited to only certain groups. In addition, studies focusing on the structure and spatial distribution of these communities are lacking. This study analyzed the effects of natural and anthropic variables on the community structure of macroinvertebrates along a longitudinal gradient in three microbasins located in a region of landscape transition in the state of Rio Grande do Sul, Brazil. Sampling was conducted in the Vacacaí-Mirim River (August 2008) and in the Ibicuí-Mirim and Tororaipí rivers (August 2009) following an environmental gradient including 1(st), 2(nd), 3(rd), and 4(th) order segments. Local natural factors that were analyzed include water temperature, pH, electrical conductivity, dissolved oxygen, substrate granulometry, and the presence of aquatic vegetation. Anthropic variables that were analyzed include including bank erosion, land use, urbanization, riparian deforestation, and fine sediments input. A total of 42 families and 129 taxa were found, with predominance of environmentally tolerant taxa. Geological context (landscape transition and large hydrographic basins) tended to influence natural environmental factors along the rivers' longitudinal gradients. However, changes in anthropic variables were not affected by these geological differences and therefore did not correlate with patterns of spatial distribution in macroinvertebrate communities. Only 1(st) order stream segments showed a community composition with high richness of taxa intolerant to anthropic disturbance. Richness as a whole tended to be higher in 3(rd) to 4(th) order set of segments, but this trend was a result of local anthropic environmental disturbances. Future inventories conducted in similar landscape transition regions of Brazil, for conservation purposes, must consider stream segments of different orders, microbasins, and major basins in order to obtain data that faithfully reflect the regional diversity. Additionally, it is necessary to consider environmental gradients of land use and anthropic impacts in order to suggest appropriate strategies for conserving the environmental integrity of streams.

Diversity and distribution of riffle beetle assemblages (Coleoptera, Elmidae) in montane rivers of Southern Brazil / Diversidade e distribuição de comunidades de Elmidae (Coleoptera) em rios montanhosos do sul do Brasil

The diversity and spatio-temporal distribution of Elmidae (Coleoptera) assemblages in montane rivers and streams of southernmost Brazil (Rio Grande do Sul state) were studied. Six genera were found, represented mostly by larval specimens. Austrolimnius and Macrelmis are new occurrences in the region. Assemblages' genera composition and dominance were related to the presence of the macrophyte Podostemum. Also, water temperature and stream depth and velocity were the most important drivers related to the assemblages' distribution. Richness and abundance were positively related to high water velocity and negatively to stream depth. Temporal patterns were detected especially in assemblage abundance, yet a slight pattern in richness was also observed. The seasonal structure was related to warm temperatures, but temporal distribution of Elmidae assemblages appears to be related to the dominant genera life cycles. The studied area shows an overall Elmidae richness similar to that found in some tropical areas and the role of mountainous environments in sustaining high rates of regional diversity in the Neotropics is stated.

A diversidade e a distribuição espaço-temporal de comunidades de Elmidae (Coleoptera) em rios e riachos de uma área montanhosa no sul do Brasil (estado do Rio Grande do Sul) foram estudadas. Sete gêneros foram encontrados, representados principalmente pelo estágio larval. Austrolimniuse Macrelmis são novas ocorrências no estado. A composição e a dominância dos gêneros estiveram relacionadas com a presença da macrófitaPodostemum. Além disso, a temperatura da água, a velocidade da corrente e a profundidade dos riachos foram os fatores mais importantes relacionados à distribuição das comunidades. A riqueza e a abundância foram positivamente relacionadas com a velocidade da corrente e negativamente com a profundidade. Não foram detectados fortes padrÕes temporais na riqueza, mas certa sazonalidade na abundância das comunidades foi observada. A distribuição temporal não esteve relacionada a um fator abiótico especí;fico. Assim, a distribuição temporal das comunidades de Elmidae parece estar relacionada aos ciclos de vida dos gêneros dominantes. Por fim, ressalta-se que a área de estudo apresenta uma riqueza total Elmidae semelhante à de algumas áreas tropicais e o importante papel dos riachos montanhosos na manutenção de altas taxas de diversidade regional na região Neotropical.