Geographic isolation and climate govern the functional diversity of native fish communities in European drainage basins

Abstract

Aim In times of biodiversity crisis, it is extremely important to understand diversity gradients. In particular, the study of the diversity of ecological functions is a key issue for the management of ecosystem integrity. Here we identify areas of low functional diversity of the native fish fauna in European drainage basins and we determine the relative importance of three underlying mechanisms: environmental filtering, geographic isolation and climatic history. Location The European continent. Methods Based on 14 morphological traits that are closely related to fish function (habitat and dietary niches), three independent functional diversity indices [functional richness (FR), functional evenness (FE), functional divergence (FD)] were calculated for 128 European drainage basins with a total of 230 fish species. The indices were standardized for species richness using null models. The patterns of the standardized indices are described and three potentially underlying mechanisms are tested using variance partitioning and multi‐linear regression models. Results FR and FD were highest in eastern European drainage basins and in Great Britain and lowest in the Mediterranean. FE patterns were less pronounced. All observed patterns were mainly governed by geographic isolation and present environmental conditions. Within the environmental conditions, average annual temperature and precipitation were good predictors for functional diversity. The role of habitat diversity and size was negligible. Main conclusions Geographic isolation coupled with harsh environmental conditions such as extreme temperatures and low precipitation, as in Mediterranean regions, can lead to low FR and FD. This can be explained by extinction that could not be compensated by re‐colonization and high speciation. Due to their high functional redundancy, communities in these areas might better withstand further species extinctions on a small scale. Over the short term, however, their often extremely low FR suggests a less flexible functioning that can hinder their ability to withstand today's rapid environmental and anthropogenic threats.

Stream ichthyofauna of the Tapajós National Forest, Pará, Brazil

“…The existence of dissimilarity in fish species composition of different, however geographically close, drainage systems within the Tapajos National Forest indicates that geographic isolation coupled with environmental characteristics is responsible for the structuring of fish communities, in accordance with observed by Schleuter et al (2012) in temperate regions and Barros et al 2013, in tropical streams. Furthermore the smaller drainage basins can significantly influence the stream fish assemblages composition (Mendonça et al 2005; Barros et al 2013) since headwaters streams often support exclusive species that do not occur in the river system, allowing constitute single assemblages that are fundamental to compose the regional fish diversity (Paller 1994; Meyer et al 2007) and must be priority included in units conservation planning for freshwater systems.…”

Size diversity and species diversity relationships in fish assemblages of Western Palearctic lakes

“…A1), maybe reflecting that biogeographical differences and ecological processes (e.g. higher interspecific competition) at local or evolutionary scales lead to increased niche specialisation towards low latitudes, as has been found in several previous studies (Griffiths 2006, Reyjol et al 2007, Mason et al 2008, Tedesco et al 2012, Schleuter et al 2012, Cirtwill et al 2015.…”

The influence of environmental variables on the functional structure of headwater stream fish assemblages: a study of two tropical basins in Central Brazil

“…These authors suggest that this trend corresponds to different forms of ecosystem functioning, ranging from warm water and lower altitudinal systems (in our study represented by Araguaia basin streams) to colder and high altitudinal systems (Tocantins basin streams). Schleuter et al (2012) also observed differences between fish assemblages' functional structure of neighboring basins separated by mountain chains, as is the case of the Araguaia and Tocantins. Rahel & Hubert (1991) pointed out that transition in biological communities due to thermal conditions is expected in mountainous regions, where water temperature decreases as altitude increases.…”