Banca de DEFESA: MILAINE SILVANO DA FONSECA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : MILAINE SILVANO DA FONSECA
DATE: 16/03/2022
TIME: 14:00
LOCAL: on-line
TITLE:

Importance of spatial scales on the structure and beta diversity of reef fish assemblages in Ilha Grande Bay, RJ

KEY WORDS:

ichthyofauna, beta diversity, habitat structure, spatial scales

PAGES: 55
BIG AREA: Ciências Biológicas
AREA: Zoologia
SUBÁREA: Zoologia Aplicada
SUMMARY:

Understanding the influence of spatial scales on biodiversity is essential to determine which
conservation measures should be implemented at the sites in a region. Reef fish are a
fundamental component for the functioning of reef ecosystems and have been threatened by
impacts that occur at local and regional scales. Detecting which spatial scales are associated
with greater variation in assemblage composition is crucial to identify the processes in the
habitat that promote this pattern and propose effective conservation measures. The objectives
of this study were: (1) to quantify the spatial variation of reef fish assemblages at scales from
tens of meters to tens of kilometers, and (2) to determine whether there are patterns of beta
diversity at these spatial scales. The tested hypotheses were that (1) there is a positive
association between habitat heterogeneity and beta diversity, and (2) that smaller spatial scale
leads to greater heterogeneity and beta diversity. These components of fish assemblage
diversity (beta diversity) and habitat (habitat heterogeneity) were evaluated at a local spatial
scale (between transects of sites) and a larger spatial scale (between sites of regions). Five
regions were established in Ilha Grande Bay, with 2 covering deeper locations and increased
distances from the coast (Ilha Grande and Canal Central), and 3 with shallower locations, close
to the coast and under estuarine influence (Ribeira Bay, Mambucaba and Paraty). At each site,
4-6 transects were sampled, totaling 289 transects. The difference in fish assemblage structure
across spatial scales was tested using permutational multivariate analysis of variance
(PERMANOVA) based on the Bray-Curtis index. The variation in species composition across
spatial scales (beta diversity) was tested with analysis of the Homogeneity of Multivariate
Dispersions (PERMDISP) based on the Jaccard index, while the components of nestedness and
turnover were obtained by the BetaPart package. The greatest variability in fish assemblage
structure occurred between sites within each region (Pseudo-F = 3.9, p=0.0001, ECV = 26%).
Distance from the coast and benthic cover were the best predictors of assemblage structure. An
assemblage of predatory fishes of mobile and carnivorous invertebrates characterized the
samples from the Ribeira and Paraty bays, while a richer assemblage with fish from multiple
trophic groups represented the samples from the Central Channel, Ilha Grande. Beta diversity
varied within sites (F=4.241, P=0.0001) and regions (F=4.7173, p=0.0163). However, the local
scale presented the highest Jaccard dissimilarity, with the turnover component as the main
contributor, while in the regions the Jaccard dissimilarity decreased, and the contribution of
turnover and nestedness were more uniform. Beta diversity was positively correlated with
habitat heterogeneity (p<0.01), with the Ilha Grande sites being more heterogeneous compared
to the Ribeira and Paraty bay sites. The variation of the fish assemblage at the scale of the sites
was associated with the heterogeneity of the habitat, while the impacts associated with the
influence of rivers and proximity to the coast were associated to assemblages’ differences at
the scale of the regions. Conservation measures should consider the heterogeneity of habitats
and the usage history at the scale of sites, and actions that minimize the effects of broader and
more diffuse impacts at the scale of regions.

BANKING MEMBERS:
Externo ao Programa - 1767348 - FABIO SOUTO DE ALMEIDA
Interno - 2143107 - LEONARDO MITRANO NEVES
Externo à Instituição - LUIS FELIPE SKINNER - UERJ
Interno - 1341945 - RAFAEL DE ALMEIDA TUBINO