|Title||Complementarity of rarity, specialisation and functional diversity metrics to assess community responses to environmental changes, using an example of spider communities in salt marshes|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Leroy, B, Le Viol, I, Petillon, J|
|Keywords||Community Specialisation Index, CSI, Cutting, FDiv, Functional divergence, Functional Divergence Index, Grazing, Index of Relative Rarity, IRR, Species Specialisation Index, spiders, SSI|
The study of community responses to environmental changes can be enhanced by the recent development of new metrics useful in applied conservation: relative rarity, ecological specialisation and functional diversity. These different metrics have been critically assessed independently, but are rarely combined in applied conservation studies, especially for less-studied taxa such as arthropods. Here we report how these different metrics can complement each other by using the response of spider communities to environmental changes in salt marshes as an example. Sampling took place using pitfall traps in salt marshes of the Mont St Michel Bay (France) during 2004 and 2007. The sampling design was spatially replicated (3 plots per treatment and 4 traps per plot) and encompassed four habitat treatments: control, sheep grazing, cutting (annual, in summer) and invasion by the plant Elymus athericus. We observed contrasting responses of spider communities to the different treatments: grazing had a negative impact on both rarity and functional diversity but a positive impact on specialisation; cutting had a negative impact on the three metrics; and invasion only had a negative impact on rarity and specialisation. These contrasting responses emphasise the necessity of using different complementary community metrics in such conservation studies. Consequently, rarity-, specialisation-, and functional-based indices should be applied simultaneously more frequently, as they potentially provide additional complementary information about communities. Such complementary information is the key to better-informed conservation choices.