Effect of Environmental and Temporal Factors on Patterns of Rarity of Ephemeroptera in Stream of the Brazilian Cerrado

Abstract

Patterns of species' abundance and occurrence over time and space allow division of species into (i) common species, which are abundant, but have a low diversity, and (ii) rare species, which are far more diverse and less abundant. Understanding the relationships among these two species groups and how they are affected by environmental conditions is a major challenge for ecologists, especially considering the distinction between local environmental factors and regional factors and variations in abundance over the course of the year. In this study, we focused on the long-term relationship between the abundance of rare and common ephemeropterans and abiotic factors on local and regional scales. Our hypotheses are that common species will be affected primarily by regional environmental variables (i), whereas rare species will be influenced more by temporal variation (ii). Together, both local and regional abiotic variables, plus temporal variation, best explained the abundance of the common species, whereas temporal variation was the best predictor of rare species. Considering the theoretical aspects and the empirical evidence, we discuss the results based on the plasticity of the common species and the life cycle of the rare ones. We believe that our findings reinforce the need for the deconstruction of communities for a deeper understanding of their relationships with abiotic variables and, in particular, the specific aspects of these relationships in the context of the different guilds of the community.

Spatiotemporal dynamics in caddisfly (Insecta: Trichoptera) of a Cerrado stream, Brazil

“…This corroborates our hypothesis that there is an important interaction between spatial and temporal factors in determining community composition in these environments. Other studies carried out in the same stream but with other taxonomic groups have found similar results of the longitudinal distribution on the distribution of a Heteroptera population (Giehl et al, 2015), and of the temporal variation on rare and common Ephemeroptera communities (Brasil et al, 2017). In addition to a temporal evaluation of zooplankton of reservoirs in the Cerrado (Lodi et al, 2014), these previous evidences along with our results indicate a certain level of synchrony in the spatiotemporal distribution of aquatic species in the Cerrado.…”

“…The environmental variables were electrical conductivity, pH, dissolved oxygen, water temperature, and turbidity. The temporal variables were calculated using a principal coordinate analysis of neighbor matrices (PCNM) (Dray et al, 2006) as "temporal filters" to understand how much of the community variation was explained by the temporal distance among samples (temporal autocorrelation) (Brasil et al, 2017). We used the function "pcnm" of the package vegan (Oksanen et al, 2013) to calculate the PCNMs, where the vectors represented the sampling dates (month and year).…”

“…This is because the stream channel accumulates more leaf banks in this period, providing an increased heterogeneity (Baptista et al, 2001). Simultaneously, more rare species, which live for only few months of the year as immature individuals, are recorded in the driest season (Brasil et al, 2017). In this work and others (e.g., Bispo et al, 2006;Yokoyama et al, 2012;Brasil et al, 2017), the relation of communities with the variation in the physico-chemical conditions of water was evident, mainly between dry and rainy seasons (Bleich et al, 2009).…”

“…On a temporal perspective, a prominent lateral contribution of nutrients is observed when the water level retracts after a flood pulse, importing organic particles into the streams (Junk et al, 1989). In both processes (longitudinal and temporal), abiotic dynamics modulate species diversity through time and space (Vannote et al, 1980;Junk et al, 1989;Brasil et al, 2017).…”

The importance of common and the irrelevance of rare species for partition the variation of community matrix: implications for sampling and conservation

“…One potential reason for such an antagonistic response is the categorization of species as rare or common, which tend to respond to environmental gradients in an idiosyncratic way 18,22 . Because of that, by analyzing all species in the community together, it is possible to increase the model residual portion.…”