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New BioFresh publication: monitoring the ‘global reshuffling’ of species distributions and diversity

February 15, 2012

A Swedish freshwater landscape. Monitoring species distributions across a landscape at different levels of diversity remains a focus of much research. Image: Nuria Bonada

There is increased attention being paid to biotic homogenisation and differentiation following increased human pressures on ecosystems, biotic  invasions and what the IUCN’s Jeff McNeely terms the ‘global reshuffling’ of species distributions. A new paper by BioFresh partners Sébastien Villéger and Sébastien Brosse develops a new mathematical metric based on species extirpation (local extinction) and non-native species invasions to measure and assess changes to biodiversity.

Sébastien Brosse outlines the basis of the paper “The loss of distinctiveness between biological communities, called “Biotic Homogenization”, has been measured using different indices (different mathematical formulations). In this paper we evaluated the relevance of these indices to measure Biotic Homogenization, and then we provide a tool to disentangle what determines homogenization. This tool will help us to better understand how human activities affect a measure of biodiversity called Beta-diversity (i.e. the taxonomic differences between localities).”

The article “Measuring changes in taxonomic dissimilarity following species introductions and extirpations”, published in the journal Ecological Indicators provides a significant step forward in quantifying and predicting human impact on the health and status of global ecosystems.  You can access the article here.

What do alpha, beta and gamma diversity mean?

The paper by Villéger and Brosse refers to the concepts of alpha and beta diversity – but what do these terms actually mean?  Many people are familiar with the term biodiversity, generally agreed to mean the variety of life on earth – from microorganisms to giant whales – and the ecosystems in which they live.

However, the idea of “biodiversity” is relatively recent concept, popularised in the 1980s.  In the 1960s, Robert Whittaker – an American plant ecologist – proposed a three-tiered concept of species diversity across a landscape.  Whittaker proposed that the total species diversity in a landscape (gamma diversity) is determined by the species diversity in sites or habitats at a local scale (e.g. an individual lake or field – alpha diversity) and the level of differentiation between these habitats (beta diversity).

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