Community assembly at the patch scale in a species rich tropical river

Abstract

In tropical floodplain rivers, communities associated with structurally complex habitats are disassembled and reassembled as aquatic organisms repeatedly colonize new areas in response to gradual but continuous changes in water level. Thus, a neutral model reflecting random colonization and extinction dynamics may be sufficient to predict assemblage patterns at the scale of local habitat patches. If water level fluctuations and associated patch dynamics are sufficiently predictable, however, community assembly on habitat patches also may be influenced by species-specific responses to habitat features and/or species interactions. We experimentally manipulated structural complexity and proximity to source habitat (which influences colonization rate) of simulated rocky patches in the littoral zone of a tropical lowland river and demonstrate significant effects of both factors on species density of fishes and macroinvertebrates. Interspecific variation in vagility significantly affected assemblage response to habitat complexity. In a second experiment, created habitat patches were sampled over time intervals ranging from 1 day to 36 days to examine temporal dynamics of community assembly. A null-model test revealed that assemblage structure became increasingly non-random, concomitant with increasing species density, over time. Community dynamics in newly formed habitat patches appeared to be dominated by dispersal, whereas in older patches, abundances of individual species increasingly were influenced by habitat characteristics. These data suggest that species-specific responses to environmental variation resulted, in part, because of species interactions. We conclude that community assembly in shallow habitats of this tropical lowland river is influenced by physical habitat characteristics, the spatial distribution of habitat patches, and species interactions as habitats are saturated with individuals.

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

“…Flecker (1992 reported rapid colonization of manipulated substrata by invertebrates in a piedmont river in Venezuela, with from 600 to > 2400 individuals per 0.25 m 2 . Crenicichla lugubris in the Cinaruco River were common near submerged woody debris and rocks, and these habitats probably hold relatively sedentary prey Arrington et al, 2005). These structurally in the Cinaruco River and Layman et al (in press) in the nearby Caño La Guardia.…”

“…During the wet season (May to October), the riparian forest and surrounding savanna is flooded, and organisms disperse widely throughout the river floodplain. The dry season is associated with a continuously falling water level that forces aquatic organisms off the floodplain and into the main river channel and lagoons (Winemiller & Jepsen, 1998;Arrington et al, 2005).…”

Fish assemblage structure is consistent through an annual hydrological cycle in habitats of a floodplain-lake in the Colombian Amazon

“…Two main assemblages were identified in Taraira Lake, a large assemblage of species associated with lagoon channels, stream, isolated shrub patches and flooded forest habitats; and a second assemblage of species associated with muddy beaches. Non-random associations of fish species have seemingly been found in other seasonal system, influenced by characteristics of the habitat and by interspecific interactions (Rodriguez & Lewis, 1997;Petry et al, 2003;Arrington et al 2005).…”

“…Layman and Winemiller (2004) found direct evidence for the influence of predator abundance on medium-size prey fishes in beach communities of a lowland river in Venezuela during the low-water season. Arrington et al (2005) found evidence for species interactions influencing fish assemblage structure mediated by dispersal dynamics in response to changing water levels in a floodplain river in the Venezuelan llanos.…”

Fatores que influenciam a comunidade de peixes em dois ambientes no baixo Rio das Mortes, Planície do Bananal, Mato Grosso, Brasil

“…Durante o período de cheia muitas espécies de peixes tendem a se dispersar ao longo da planície inundada para explorar novos hábitats e recursos alimentares (SAINT-PAUL et al 2000, SILVANO et al 2000, GALACATOS et al 2004, ARRINGTON et al 2005. Na seca, com a diminuição do nível da água, os peixes estão mais concentrados nos ambientes e são mais facilmente capturados pelas redes de espera (GOULDING et al 1988, SILVANO et al 2000.…”