Journal Article

Eutrophication causes speciation reversal in whitefish adaptive radiations

Bittner, D., Lundsgaard-Hansen, B., Müller, R., Seehausen, O., Largiader, C. R., Vonlanthen, P., Hudson, A. G., Di Piazza, S., Roy, D., Young, K. A.

2012

Overview

Species diversity can be lost through two different but potentially interacting extinction processes: demographic decline and speciation reversal through introgressive hybridization. To investigate the relative contribution of these processes, we analysed historical and contemporary data of replicate whitefish radiations from 17 pre-alpine European lakes and reconstructed changes in genetic species differentiation through time using historical samples. Here we provide evidence that species diversity evolved in response to ecological opportunity, and that eutrophication, by diminishing this opportunity, has driven extinctions through speciation reversal and demographic decline. Across the radiations, the magnitude of eutrophication explains the pattern of species loss and levels of genetic and functional distinctiveness among remaining species. We argue that extinction by speciation reversal may be more widespread than currently appreciated. Preventing such extinctions will require that conservation efforts not only target existing species but identify and protect the ecological and evolutionary processes that generate and maintain species. Historical and contemporary data of whitefish radiations from pre-alpine European lakes and reconstruction of changes in whitefish genetic species differentiation through time show that species diversity may have evolved in response to ecological opportunity, and that eutrophication, by diminishing this opportunity, has driven extinctions through speciation reversal and demographic decline. Extinction through reversed speciation Species extinctions happen in two very different ways. In the first, there can be a simple population decline. Less obvious is a second mechanism, in which previously distinct species merge through a reversal of the speciation process. This process reduces biodiversity, but not necessarily the total number of individual animals or plants present. An analysis of historical and contemporary data on endemic whitefish from 17 large European lakes that experienced major diversity loss demonstrates the second mechanism in action. There is strong evidence to suggest that eutrophication, the biological enrichment of a lake over time, has driven the extinction of many endemic species by reversing ecological speciation. Such extinctions can be prevented only if conservation efforts, in addition to preserving existing species, identify and protect the processes that generate species.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/158/672 / 631/1647/334/1874 / 631/181/759/2467 / 704/158/670 / Animal and plant ecology / Animal, plant and microbial ecology / Animals / Applied ecology / Biodiversity / Biological and medical sciences / Biological Evolution / Conservation, protection and management of environment and wildlife / Endangered & extinct species / Environmental degradation: ecosystems survey and restoration / Europe / Eutrophication / Eutrophication - physiology / Extinction, Biological / Fish / Fresh water ecosystems / Freshwater / Fundamental and applied biological sciences. Psychology / Genetic Speciation / Humanities and Social Sciences / Lakes / Models, Biological / multidisciplinary / Phenotype / Plankton / Protected species / Salmonidae - genetics / Salmonidae - physiology / Science / Science (multidisciplinary) / Speciation / Species diversity / Species extinction / Synecology