Extinction Risk and Diversification Are Linked in a Plant Biodiversity Hotspot

T Jonathan Davies,Félix Forest,Michelle Van Der Bank,James S Boatwright,Luke J Harmon,Vincent Savolainen,A Muthama Muasya,Benny Bytebier,Richard M Cowling,Dirk U Bellstedt,Yolande Steenkamp,Brian D Schrire,Gideon F Smith

doi:10.1371/journal.pbio.1000620

Abstract

Author SummaryThe rapid loss of biodiversity is the most significant ecological challenge we face today. Over the past few years, the International Union for Conservation of Nature has published Red Lists documenting the inexorable slide towards extinction of species; recent losses include the Hawaiian crow, golden toad, Baiji dolphin, and the West African black rhino. In groups we know well, such as mammals, the risk of extinction has been related to biology, with the most vulnerable species tending to be large, slow breeding, and narrowly distributed. Although plants are the basis for life on Earth, our knowledge of the drivers of plant extinctions is poor. Here, we disentangle the causes of plant extinctions. We show that the processes linked with extinction risks in plants of the Cape, South Africa differ from those for vertebrates more generally. The most vulnerable species are found within young and fast-evolving plant lineages, opposite to patterns in vertebrates. Our results illustrate the intricate link between the processes of speciation and extinction. We also show that the most threatened species are marching towards extinction at faster rates, but surprisingly, the risk appears independent of human effects.

Highlights

The rapid and accelerating loss of biodiversity is the most significant ecological challenge we face today
Using generalized linear modeling (GLM) of threat in genera endemic to the Cape, we show that lineages with a higher proportion of threatened species are species rich and young and rapidly diversifying (z = 5.86, p,0.001; z = 26.99, p,0.001; z = 5.54, p,0.001, from GLMs for richness, age, and diversification, respectively; Table 1)
By comparing consecutive Red Lists of the South African flora (Materials and Methods), we found that the most threatened taxa are marching towards extinction at the fastest pace

Summary

Introduction

The rapid and accelerating loss of biodiversity is the most significant ecological challenge we face today. The main direct human-induced drivers that impact biodiversity are habitat loss and fragmentation, whereas climate change is likely to become a dominant future driver [5]. We lose an element of biodiversity along with the associated ecosystem services it provides and the unique evolutionary history it represents. For over four decades the Red List of Threatened Species from the International Union for Conservation of Nature (IUCN; http:// www.iucnredlist.org/) has provided a record of the incremental slide towards extinction of much of current biodiversity [6,7,8]

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