Ecologia de camarões de riachos amazônicos: efeito do tamanho corporal no uso do habitat, padrões temporais de reprodução e divergência ecológica

Abstract

Environmental variation remains the mechanism that most affects species distribution and abundance at intermediate scales. Thus, the adjustment required for species persistence and success generally depends on the spatial and temporal availability of resources. However, little is known about the combined effect of space and time on resource availability on multiple traits of freshwater shrimp species, especially at fine geographic scales. This thesis sought to unravel the combined effects of spatial and temporal habitat variation on the ontogenetic niche, reproduction, and ecological similarity of three common Amazonian shrimp species (Macrobrachium inpa, Macrobrachium nattereri, and Pseudopalaemon amazonensis). Individuals of all species were sampled in streams of an upland rainforest located in a 64 km² area in Central Amazonia. In Chapter 1, we showed that conspecifics of different life stages use habitat resources differently and that heterospecifics at similar life stages use different resources only at specific stages. In Chapter 2, we revealed that the species reproduce continuously throughout the year, although a non-stochastic pattern was found for one species. Overall, body size did not differ significantly throughout our time-series and for one species, precipitation was negatively correlated with the proportion of reproductive females. In Chapter 3, we demonstrated that, at relatively small scales, populations exhibited ecological divergence for fecundity selection along gradients of water speed and substrate. This result suggests that this divergence may have been driven by local adaptation, phenotypic plasticity, or both. In this thesis, we demonstrate that relatively small spatial scales can capture spatial and temporal variations in the environment significant enough to both maintain, and possibly create, shrimp diversity. These results fill long-standing gaps for freshwater shrimp ecology and bring new perspectives to evolutionary studies related to the group.