Consistent phenological shifts in the making of a biodiversity hotspot: the Cape flora

Ben Warren ,Benny Bytebier,Félix Forest,Chloé Galley,Klaus Mummenhoff,Vincent Savolainen,Dawn Edwards,Timotheüs Van Der Niet,Marcus Quint,G Anthony Verboom ,Brian Schrire ,James E Richardson ,Baoheng Du ,A Muthama Muasya ,Regine Claßen‐Bockhoff ,Freek T Bakker ,L.l Dreyer ,Christopher R Hardy ,H Peter Linder ,Chris Yesson ,Kenneth C Oberlander ,Julie A Hawkins

doi:10.1186/1471-2148-11-39

Abstract

BackgroundThe best documented survival responses of organisms to past climate change on short (glacial-interglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years.ResultsForty-three distributional and phenological shifts consistent with past climatic change occur across the flora, and a comparable number of clades underwent adaptive changes in their flowering phenology (9 clades; half of the clades investigated) as underwent distributional shifts (12 clades; two thirds of the clades investigated). Of extant Cape angiosperm species, 14-41% have been contributed by lineages that show distributional shifts consistent with past climate change, yet a similar proportion (14-55%) arose from lineages that shifted flowering phenology.ConclusionsAdaptive changes in ecology at the scale we uncover in the Cape and consistent with past climatic change have not been documented for other floras. Shifts in climate tolerance appear to have been more important in this flora than is currently appreciated, and lineages that underwent such shifts went on to contribute a high proportion of the flora's extant species diversity. That shifts in phenology, on an evolutionary timescale and on such a scale, have not yet been detected for other floras is likely a result of the method used; shifts in flowering phenology cannot be detected in the fossil record.

Highlights

IntroductionThe best documented survival responses of organisms to past climate change on short (glacialinterglacial) timescales are distributional shifts
The best documented survival responses of organisms to past climate change on short timescales are distributional shifts
Our phylogenetic reconstructions demonstrate that 9 clades have undergone shifts in flowering pattern consistent with predictions based on past climate change (Figure 2; Table 1)

Summary

Introduction

The best documented survival responses of organisms to past climate change on short (glacialinterglacial) timescales are distributional shifts. We use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa’s biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. At the level of species or evolutionarily significant units, the traditional view is based on the fossil record [18,19,20], which shows that in response to past climatic changes in the Quaternary (fluctuations occurring on the timescale of thousands of years, within the last 2.6 million years) species underwent dramatic distributional shifts, but retained remarkable stability in phenotype and inferred ecology. The importance of distributional shifts on this timescale is further supported by the success of ecological niche models in predicting ancient distributions [21,22]

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