Linking spatial scale dependence of land-use descriptors and invertebrate cave community composition

Thais Pellegrini,Rodrigo Lopes Ferreira,Polyanne Aguiar,Lilian Patrícia Sales

doi:10.3897/subtbiol.18.8335

Abstract

Patterns of biodiversity respond to habitat disturbances and different land-uses. Those patterns possibly vary according to the spatial scale under analysis. Although other studies have shown such responses for different systems, no study has ever demonstrated spatial-scale influences in subterranean terrestrial communities. Therefore, the objective of this paper was to analyze how land use and cave physical structure could influence the terrestrial cave invertebrate species composition. We also determined the influence of different spatial scale on the structure of invertebrate cave composition. We collected environmental data at local scale (e.g. cave size, substrate and environmental stability). For spatial scale we determined land uses at three different landscape scales; we gathered these data into circular areas of different sizes (50, 100 and 250 meters) with centroids in the cave entrances. We finally performed three Distance Based Linear Modeling analyses to test for differences among the predictability of environmental variables when comparing different spatial scales. The best explanatory variable for cave invertebrate similarities was the percentage of covering of the external environment by limestone outcrops. We confirm the scale-dependence hypothesis through the different patterns showed among distinct buffer areas. Models become more precise when larger scales were analyzed to explain cave invertebrate composition. This suggests that larger scales capture important environmental features that explain the cave fauna similarities more precisely. Additionally, we found a strong influence of limestone outcrops at all landscape scale structuring cave communities.

Highlights

Environmental heterogeneity in natural landscapes has been historically replaced by anthropogenic mosaics around the world
Biodiversity is often positively correlated with the amount of available habitat (Fahrig 2003), but the effect of land-use changes on biodiversity depends on the landscape context (MacDonald et al 2000) and on the spatial scale that has been analyzed (McGlinn and Hurlbert 2012, Dumbrell et al 2008, Zimmermann et al 2010, Morueta-Holme et al 2013)
Ecological communities are structured under processes that act on the landscape, in which both regional and local scales are important factors (Harrison and Cornell 2008)

Summary

Introduction

Environmental heterogeneity in natural landscapes has been historically replaced by anthropogenic mosaics around the world. Since the cave communities are dependent on the allochthonous input of nutrients, alterations in the availability, properties and abundance of these nutrients in the landscape surrounding the caves may affect cave biodiversity Despite their fragility, caves are under several anthropogenic pressures, and only few studies evaluated how such human activities can affect the invertebrate cave communities, such as inadequate tourism Poulson et al 1995, Moldovan et al 2003, Pellegrini and Ferreira 2012) Such studies are even scarcer when considering human impact at landscape scale, such as agriculture, urban development, deforestation and mineral resources extraction (Eme et al 2014, Zagmajster et al 2014). Other studies have shown responses for different spatial scales under analysis (e.g. Steffan-Dewenter et al 2002), few studies have demonstrated such influences in subterranean communities patterns (Eme et al 2014, Zagmajster et al 2014)

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Conclusion