UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Complex body size trends in the evolution of sloths (Xenarthra: Pilosa)

Pant, SR; Goswami, A; Finarelli, JA; (2014) Complex body size trends in the evolution of sloths (Xenarthra: Pilosa). BMC Evolutionary Biology , 14 , Article 184. 10.1186/s12862-014-0184-1. Green open access

[thumbnail of s12862-014-0184-1.pdf]
Preview
PDF
s12862-014-0184-1.pdf

Download (533kB)
[thumbnail of Additional file 1: Table S1.:] Excel Spreadsheet (Additional file 1: Table S1.:)
s12862-014-0184-1-s1.xlsx

Download (94kB)

Abstract

Background Extant sloths present an evolutionary conundrum in that the two living genera are superficially similar (small-bodied, folivorous, arboreal) but diverged from one another approximately 30 million years ago and are phylogenetically separated by a radiation of medium to massive, mainly ground-dwelling, taxa. Indeed, the species in the two living genera are among the smallest, and perhaps most unusual, of the 50+ known sloth species, and must have independently and convergently evolved small size and arboreality. In order to accurately reconstruct sloth evolution, it is critical to incorporate their extinct diversity in analyses. Here, we used a dataset of 57 species of living and fossil sloths to examine changes in body mass mean and variance through their evolution, employing a general time-variable model that allows for analysis of evolutionary trends in continuous characters within clades lacking fully-resolved phylogenies, such as sloths. Results Our analyses supported eight models, all of which partition sloths into multiple subgroups, suggesting distinct modes of body size evolution among the major sloth lineages. Model-averaged parameter values supported trended walks in most clades, with estimated rates of body mass change ranging as high as 126 kg/million years for the giant ground sloth clades Megatheriidae and Nothrotheriidae. Inclusion of living sloth species in the analyses weakened reconstructed rates for their respective groups, with estimated rates for Megalonychidae (large to giant ground sloths and the extant two-toed sloth) were four times higher when the extant genus Choloepus was excluded. Conclusions Analyses based on extant taxa alone have the potential to oversimplify or misidentify macroevolutionary patterns. This study demonstrates the impact that integration of data from the fossil record can have on reconstructions of character evolution and establishes that body size evolution in sloths was complex, but dominated by trended walks towards the enormous sizes exhibited in some recently extinct forms.

Type: Article
Title: Complex body size trends in the evolution of sloths (Xenarthra: Pilosa)
Open access status: An open access version is available from UCL Discovery
DOI: 10.1186/s12862-014-0184-1
Publisher version: http://dx.doi.org/10.1186/s12862-014-0184-1
Language: English
Additional information: © 2014 Raj Pant et al.; licensee BioMed Central Ltd This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Keywords: Ancestral character state reconstruction, Evolutionary rates, Fossils, Mammalia
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Genetics, Evolution and Environment
URI: https://discovery.ucl.ac.uk/id/eprint/1449813
Downloads since deposit
188Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item