Differential Extinction and the Contrasting Structure of Polar Marine Faunas

Andrew Z Krug,David Jablonski,Kaustuv Roy,Alan G Beu,Corrie S Moreau

doi:10.1371/journal.pone.0015362

Abstract

BackgroundThe low taxonomic diversity of polar marine faunas today reflects both the failure of clades to colonize or diversify in high latitudes and regional extinctions of once-present clades. However, simple models of polar evolution are made difficult by the strikingly different faunal compositions and community structures of the two poles.Methodology/Principal FindingsA comparison of early Cenozoic Arctic and Antarctic bivalve faunas with modern ones, within the framework of a molecular phylogeny, shows that while Arctic losses were randomly distributed across the tree, Antarctic losses were significantly concentrated in more derived families, resulting in communities dominated by basal lineages. Potential mechanisms for the phylogenetic structure to Antarctic extinctions include continental isolation, changes in primary productivity leading to turnover of both predators and prey, and the effect of glaciation on shelf habitats.Conclusions/SignificanceThese results show that phylogenetic consequences of past extinctions can vary substantially among regions and thus shape regional faunal structures, even when due to similar drivers, here global cooling, and provide the first phylogenetic support for the “retrograde” hypothesis of Antarctic faunal evolution.

Highlights

The latitudinal diversity gradient (LDG) is the most pervasive biodiversity pattern on Earth, with a dramatic pole-to-equator rise in morphological and taxonomic diversity in most marine and terrestrial clades [1]
Phylogenetic Structure to Extinction In the early Cenozoic, the Arctic and Antarctic had 35 and 40 recorded bivalve families, respectively, the difference likely reflecting the poorer Arctic fossil record, with twenty-seven families shared by the two regions during the Paleocene/Eocene (Table S1)
Extinction in Antarctica is strongly (D = .097) and significantly (Standardized Effect Size mean pairwise distance (MPD) = 21.8, p = .03; SESMNTD = 22.5, p = .003;) clustered phylogenetically, with extinctions concentrated in the orders Myoida, Veneroida and Pterioida, and the family-level phylogenetic history of the Antarctic fauna was reduced by at least 27– 38%, depending on the metric

Summary

Introduction

The latitudinal diversity gradient (LDG) is the most pervasive biodiversity pattern on Earth, with a dramatic pole-to-equator rise in morphological and taxonomic diversity in most marine and terrestrial clades [1]. The compositions of modern benthic marine communities in the two polar regions differ dramatically, with the Antarctic generally being as or more diverse than the Arctic [2,3,4] but ecologically more reminiscent of Paleozoic or early Mesozoic than of modern marine communities [5]. These differences preclude simple models of polar evolution and indicate divergent evolutionary histories for the two regions. Simple models of polar evolution are made difficult by the strikingly different faunal compositions and community structures of the two poles

Methods

Results

Conclusion