Showing papers by "Andy Purvis published in 2003"

Preserving the Tree of Life

Abstract: Phylogenies provide new ways to measure biodiversity, to assess conservation priorities, and to quantify the evolutionary history in any set of species. Methodological problems and a lack of knowledge about most species have so far hampered their use. In the future, as techniques improve and more data become accessible, we will have an expanded set of conservation options, including ways to prioritize outcomes from evolutionary and ecological processes.

Biological correlates of extinction risk in bats.

Abstract: We investigated patterns and processes of extinction and threat in bats using a multivariate phylogenetic comparative approach. Of nearly 1,000 species worldwide, 239 are considered threatened by the International Union for Conservation of Nature and Natural Resources (IUCN) and 12 are extinct. Small geographic ranges and low wing aspect ratios are independently found to predict extinction risk in bats, which explains 48% of the total variance in IUCN assessments of threat. The pattern and correlates of extinction risk in the two bat suborders are significantly different. A higher proportion (4%) of megachiropteran species have gone extinct in the last 500 years than microchiropteran bats (0.3%), and a higher proportion is currently at risk of extinction (Megachiroptera: 34%; Microchiroptera: 22%). While correlates of microchiropteran extinction risk are the same as in the order as a whole, megachiropteran extinction is correlated more with reproductive rate and less with wing morphology. Bat extinction risk is not randomly distributed phylogenetically: closely related species have more similar levels of threat than would be expected if extinction risk were random. Given the unbalanced nature of the evolutionary diversification of bats, it is probable that the amount of phylogenetic diversity lost if currently threatened taxa disappear may be greater than in other clades with numerically more threatened species.

A composite species‐level phylogeny of the ‘Insectivora’ (Mammalia: Order Lipotyphla Haeckel, 1866)

Abstract: The first MRP (matrix representation with parsimony) supertree phylogeny of the Lipotyphla is presented, covering all the families that were considered to make up the traditional mammalian order Insectivora. The phylogeny does not examine relationships within the shrew subfamily Crocidurinae, but all other taxa are considered at the species level, drawing upon 41 years of systematic literature and combining information from 47 published sources. The MRP technique is also critically discussed. This study will be of use to comparative biology studies of the Lipotyphla (or of mammals as a whole) and is a rigorous review of past systematic work, as well as clearly demonstrating our current level of knowledge. The supertree clearly details a strong imbalance in phylogenetic understanding across the taxon: a great deal is known about the hedgehogs and gymnures (Erinaceidae), the New World moles (Talpidae), Palaearctic species of Sorex (subgenus Sorex )a nd the relationships between genera of red-toothed shrews (Soricinae). The supertree, however, clearly shows areas where our knowledge is conflicting or non-existent, and these gaps do not always correspond to obscure species: nothing is known about the systematics of Old World mole genera. Also very little is known about golden moles (Chrysochloridae) and the shrew-tenrec genus Microgale ,s ome of the most threatened mammals on Earth.

Phylogenetically nested comparisons for testing correlates of species richness: a simulation study of continuous variables

Abstract: Explaining the uneven distribution of species among lineages is one of the oldest questions in evolution. Proposed correlations between biological traits and species diversity are routinely tested by making comparisons between phylogenetic sister clades. Several recent studies have used nested sister-clade comparisons to test hypotheses linking continuously varying traits, such as body size, with diversity. Evaluating the findings of these studies is complicated because they differ in the index of species richness difference used, the way in which trait differences were treated, and the statistical tests employed. In this paper, we use simulations to compare the performance of four species richness indices, two choices about the branch lengths used to estimate trait values for internal nodes and two statistical tests under a range of models of clade growth and character evolution. All four indices returned appropriate Type I error rates when the assumptions of the method were met and when branch lengths were set proportional to time. Only two of the indices were robust to the different evolutionary models and to different choices of branch lengths and statistical tests. These robust indices had comparable power under one nonnull scenario. Regression through the origin was consistently more powerful than the t-test, and the choice of branch lengths exerts a strong effect on both the validity and power. In the light of our simulations, we re-evaluate the findings of those who have previously used nested comparisons in the context of species richness. We provide a set of simple guidelines to maximize the performance of phylogenetically nested comparisons in tests of putative correlates of species richness.

Supertrees Are a Necessary Not-So-Evil: A Comment on Gatesy et al.

Abstract: 1Lehrstuhl für Tierzucht, Technical University of Munich, Alte Akademie 12, 85354 Freising-Weihenstephan, Germany; E-mail: olaf.bininda@tierzucht.tum.de 2Department of Biology, Gilmer Hall, University of Virginia, Charlottesville, Virginia 22904-4328, USA; E-mail: kate.jones@virginia.edu (K.E.J.), sprice@virginia.edu (S.A.P.), jlgittleman@virginia.edu (J.L.G.) 3Department of Biological Sciences, Imperial College London, Silwood Park Campus, Ascot SL5 7PY, United Kingdom; E-mail: r.grenyer@imperial.ac.uk (R.G.), m.cardillo@imperial.ac.uk (M.C.)

The life history legacy of evolutionary body size change in carnivores

Abstract: We estimate the body sizes of direct ancestors of extant carnivores, and examine selected aspects of life history as a function not only of species’ current size, but also of recent changes in size Carnivore species that have undergone marked recent evolutionary size change show life history characteristics typically associated with species closer to the ancestral body size Thus, phyletic giants tend to mature earlier and have larger litters of smaller offspring at shorter intervals than do species of the same body size that are not phyletic giants Phyletic dwarfs, by contrast, have slower life histories than nondwarf species of the same body size We discuss two possible mechanisms for the legacy of recent size change: lag (in which life history variables cannot evolve as quickly as body size, leading to species having the ‘wrong’ life history for their body size) and body size optimization (in which life history and hence body size evolve in response to changes in energy availability); at present, we cannot distinguish between these alternatives Our finding that recent body size changes help explain residual variation around life history allometries shows that a more dynamic view of character change enables comparative studies to make more precise predictions about species traits in the context of their evolutionary background

Evolution: Opportunity versus innovation

Abstract: Why have some evolutionary lineages produced many more species than others? As far as one large group of birds is concerned, being in the right place at the right time is a plausible answer.