Patterns of spatial distribution in macroalgal communities from tropical lotic ecosystems

Abstract

-(Patterns of spatial distribution in macroalgal communities from tropical lotic ecosystems). Three sampling sites were analysed in each of the following tropical regions: 1) northwestern São Paulo State, representing a disturbed region; 2) Bonito, Mato Grosso do Sul State, representing a hard water region; and 3) Ubatuba, northern costal region of São Paulo State, a well preserved tropical rainforest region. The hard water region had the highest mean values for macroalgal species richness (6.3) and diversity index (H' = 0.62). Northwest and rainforest regions had the highest percent cover values (22.5% and 17.0%, respectively). All sites in the northwest region had one or two dominant species (percent cover significantly higher than the remaining species), characterizing the niche pre-emption distribution pattern. The same pattern was found in two sites of the Atlantic rainforest. The hard water region had dominance of one species in two out of the three sites, but differently from the northwest region, niche overlap values were lower, evidencing a patch distribution. Competition for space was one of the main factors to explain spatial distribution. Overall, sites characterized by niche pre-emption had lower species richness, higher values for niche width and overlap, dominance index and percent cover of dominant species. In contrast, sites characterized by patch distribution had higher species richness and lower values for niche overlap and width, dominance index and percent cover.

Spatial variations at different observational scales and the seasonal distributions of stream macroalgae in a Brazilian subtropical region

“…Species abundance, in turn, showed significant differences only at the mesohabitat scale. The absence of significant differences in the percentage coverage of macroalgae (differing from that observed in terms of species richness) is probably due to particular characteristics of that group, as a number of studies have reported macroalgae communities with generally low abundances (Branco & Necchi Júnior 1996, Necchi Júnior et al 2000, Borges & Necchi Júnior 2006, Krupek et al 2007, Branco et al 2009). This situation may be responsible for the similarities of abundance values observed at different scales.…”

Ecological distribution of stream macroalgae in different spatial scales using taxonomic and morphological groups

“…investigations of the spatial organization of aquatic communities in lotic environments, especially considering algae with clearly visible macroscopic growth (macroalgae "sensu " sheath & Cole 1992), have revealed interesting patterns that have generally been described as mosaics in which correlations between richness and species abundance are essentially obligatory (Borges & necchi Júnior 2006).…”

Estrutura das comunidades de macroalgas da bacia de drenagem do rio Cascavel, Estado do Paraná, Brasil

“…Isto mostra que, mesmo em um ambiente que apresente certo grau de heterogeneidade espacial, quando uma das condições altera-se em maior escala, a comunidade também sofre as consequências modificando seu padrão de distribuição. Os maiores valores de abundância e dominância verificados no período de verão reforçam tal constatação, onde as poucas espécies mais bem adaptadas ao fluxo da correnteza mais elevado predominam e abundam sobre as demais (Francoeur & Biggs 2006 (Borges & Necchi Júnior 2006). Durante o período de inverno, a redução da velocidade da correnteza foi o fator responsável pelo aumento da diversidade de espécies.…”