Habitat structural complexity and morphological diversity of fish assemblages in a Neotropical floodplain river

Abstract

High species richness and evenness in structurally complex habitats has been hypothesized to be associated with niche partitioning. To test this idea, relationships between habitat structural complexity in river littoral-zone habitats and morphological diversity of tropical fishes were examined in the Cinaruco River, Venezuela. Six habitat attributes were quantified in 45 sites spanning a range of structural complexity. Fishes were collected during day and night to estimate species density and relative abundances at each site. Twenty-two morphological variables were measured for each species. Principal components analysis (PCA) of physical habitat data yielded two axes that modeled >80% of variation across sites. The first two axes from PCA of fish morphological variables modeled >70% of variation. Species density during both day and night was negatively associated with flow velocity and positively associated with habitat complexity. Similarity of day and night samples from the same site was significantly greater for sites with high habitat complexity and low flow. In general, mean local assemblage morphological PC scores were not significantly associated with habitat PC scores. Average, maximum, and standard deviation of morphological Euclidean distances of local assemblages revealed positive associations with structural complexity and negative associations with flow. These relationships held even when the positive relationship of species density was statistically removed from assemblage morphological patterns. Findings suggest that both species niche compression and assemblage niche space increase when habitat complexity is greater and flow velocity is lower in this tropical lowland river.

Reforming Watershed Restoration: Science in Need of Application and Applications in Need of Science

“…The mechanisms are numerous and not necessarily mutually exclusive: habitat heterogeneity may provide more physical space, refuge, resource availability, and open niches for members of a community, thus promoting diversity. A great deal of work has focused on the role of niche fractionation in promoting diversity and the role of refuges in time and space minimizing competitive exclusion and mediating predator-prey interactions (Grabowski 2004;Willis et al 2005). …”

Comparative feeding ecology and habitats use of Crenicichla species (Perciformes: Cichlidae) in a Venezuelan floodplain river

“…2). The Cinaruco is characterized by a low-gradient, sandy oligotrophic substrates, and high fish diversity (> 280 fish species) that spans a wide range of ecological attributes and life history strategies Willis et al, 2005). The Cinaruco River has a strongly seasonal hydrology with a pronounced annual wet and dry season (Montoya et al, 2006).…”

Intraspecific ecomorphological variations in Poecilia reticulata (Actinopterygii, Cyprinodontiformes): comparing populations of distinct environments

“…Thus, the index use nullifies the chance of analyzes being dominated by a single variable (Winemiller, 1991). Despite the controversy about this procedure in ecomorphological studies (Peres-Neto, 1999), some authors have used index in their analysis (Gatz, 1979;Watson & Balon, 1984;Winemiller, 1991;Willis et al, 2005;Casatti & Castro, 2006;Oliveira et al, 2010). These authors assume that, by expressing the shape of morphological structures, the indices are able to reveal their ecological roles.…”