The Neotropical rodent genus Rhipidom ys (Cricetidae: Sigmodontinae) - a taxonomic revision Christopher James Tribe Thesis submitted for the degree of Doctor of Philosophy University College London 1996 ProQuest Number: 10106759 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10106759 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 ABSTRACT South American climbing mice and rats, Rhipidomys, occur in forests, plantations and rural dwellings throughout tropical South America. The genus belongs to the thomasomyine group, an informal assemblage of plesiomorphous Sigmodontinae. Over 1700 museum specimens were examined, with the aim of providing a coherent taxonomic framework for future work. A shortage of discrete and consistent characters prevented the use of strict cladistic methodology; instead, morphological assessments were supported by multivariate (especially principal components) analyses. The morphometric data were first assessed for measurement error, ontogenetic variation and sexual dimorphism; measurements with most variation from these sources were excluded from subsequent analyses. The genus is characterized by a combination of reddish-brown colour, long tufted tail, broad feet with long toes, long vibrissae and large eyes; the skull has a small zygomatic notch, squared or ridged supraorbital edges, large oval braincase and short palate. Three main divisions of the genus are recognized. The R. julviventer section contains four species - Julviventer, wetzeli, caucensis and ochrogaster - inhabiting montane forests in the northern Andes and Guiana Highlands of Colombia and Venezuela; they share grey-based ventral pelage, dark extremities, a rounded interorbital region, broad braincase, and (except for caucensis) a primitive carotid circulation pattern; R. julviventer consists of a chain of isolated subspecies, including venustus. The monospecific R. macconnelli section is restricted to the Guiana Highlands of Venezuela; it differs in certain external characters - darker colour (especially ventrally), longer metatarsals, bicoloured tail - but is similar cranially. The R. leucodactylus section is usually paler with broad feet, stronger cranial ridges and a derived carotid circulation pattern, and occurs mainly at lower levels. It contains 13 species: couesi, leucodactylus, modicus, austrinus, latimanus (including venezuelae), nitela, emiliae, macrurus, mastacalis and four as yet unnamed. Three species occur in N£ Brazil; in SE Brazil the material currently available does not permit a clear-cut arrangement. CONTENTS Abstract 2 List of tables 7 List of illustrations 8 Acknowledgements 11 1. Introduction 14 2. The systematic context 2.1 Muroidea 19 2.2 New World Cricetids 20 2.3 Sigmodontinae: historical zoogeography 25 2.4 The position of Rhipidomys withinthe Sigmodontinae 30 3. Material examined and data collected 3.1 Collections and specimens 35 3.2 Data sets: a) Non-metric characters 36 b) Dental age classes 37 c) Morphometric data 39 4. Numerical methods and preparatory analyses 4.1 Overview 44 4.2 Preparatory procedures: (a) Measurement error analysis 45 (b) Ontogenetic variation and sexual dimorphism 50 (c) Imputation of missing values 56. 4.3 Exploratory analyses 57 4.4 Discrimination of taxa 61 Delimitation of the genus 64 5.1 External morphology 65 5.2 Cranial characters 73 5.3 Dental characters 79 5.4 Postcranial skeleton and soft anatomy 85 5.5 Phylogenetic analyses 87 Diversity within Rhipidomys 6.1 Primary division of the genus 89 6.2 The Rhipidomys Julviventer section 91 6.3 The Rhipidomys macconnelli section 106 6.4 Rhipidomys leucodactylus 110 Karyotypes 111 Large-bodied species 114 Medium and small-bodied species: a) Northwestern South America 129 b) The Guiana Highlands and Amazon Basin 133 c) Eastern Brazil 144 Taxonomic synthesis Rhipidomys 166 The Rhipidomys julviventer section: R. julviventer 175 R. wetzeli 185 R. caucensis 187 R. ochrogaster 190 The Rhipidomys macconnelli section: R. macconnelli 192 The Rhipidomys leucodactylus section: R. couesi 196 R. cf. couesi 200 R. leucodactylus 200 R. modicus 209 Rhipidomys sp. 1 213 R, austrinus 215 Rhipidomys sp. 2 218 R. latimanus 220 Rhipidomys sp. 3 231 R. nitela 232 ' R. emiliae 238 R. macrurus 241 R. cf. macrurus 246 Rhipidomys incertae sedis 246 R. mastacalis 247 Rhipidomys sp. 4 251 8. Conclusions 254 Literature cited 258 Appendices: I Specimens examined for preparatory analyses 283 II Allocation of nominal taxa within Rhipidomys 285 III Gazetteer and maps of Rhipidomys collecting localities: Gazetteer 287 Map of collecting localities (general) 314 Map of collecting localities in southern Colombia, Ecuador and northern Peru 315 Map of collecting localities in Venezuela, Guyana and northern Brazil 316 List of tables Table 3.1 - Collections holding specimens of Rhipidomys examined for this study, with acronyms. 36 Table 4.1 - Results of measurement error analysis: Number of specimens, grand mean, total variance, percent measurement error and coefficient of among-specimen variation for two untransformed data sets. 47 Table 4.2 - Measurement error: greatest absolute difference in mm among three repeated measurements (largest minus smallest value) averaged over specimens, for two untransformed data sets. 48 Table 4.3 - Analysis of variance due to dental age class (DAQ, sex, and DAC/sex interaction in two series of specimens: summary of significant results ip<\7o and l%<p<5% for acceptance of Ho: no difference between groups) in three replications with different random selections of specimens. Left-hand half of table corresponds to whole series, right-hand half restricted to adults. 52 Table 4.4 - Multivariate analysis of variance due to dental age class (DAQ, sex, and DAC/sex interaction in two series of specimens: summary of significant results (p<l% and l%</?<5% for acceptance of Hg: no difference between groups) for approximate chi-squared and F-tests in three replications with different random selections of specimens. 54 Table 4.5 - Principal components analysis of Rhipidomys "cearanus" adults using standardized, log-transformed data: t-test results on differences in scores according to sex and dental age class along the principal component axes. 60 Table 6.1 - Summary of karyotype data on Rhipidomys. 113 List of figures Fig. 1.1- Rhipidomys mastacalis from Fazenda Uniao, Casimiro de Abreu, Rio de Janeiro, Brazil (Universidade Federal do Rio de Janeiro, Laboratdrio de Ecologia, no. FU 19). Photo: Lena Geise. 13 Fig. 3.1 - Measurements taken on Rhipidomys skulls. 41 Fig. 5.1- Representative Rhipidomys skulls, dorsal and ventral views (X 1.5). Left to right, first and third rows: R. ochrogaster (holotype, AMNH 16481), R. couesi (holotype, AMNH 5956/4585), R. latimanus venezuelae (AMNH 24347); second and fourth rows: R. macconnelli (AMNH 75604), R. caucensis (holotype, AMNH 32466). 70 Fig. 5.2 - Representative Rhipidomys skulls, lateral view (X 1.5). Specimens as in Fig. 5.1. Top left: R. ochrogaster (reversed); top right: R. latimanus venezuelae, centre: R, couesi; bottom left: R. macconnelli; bottom right R. caucensis ( rtvJi rç* <A). 71 Fig. 5.3 - Bones and structures of a Rhipidomys skull (/?. ochrogaster, holotype, AMNH 16481): dorsal, ventral and lateral views. 72 Fig. 5.4 - Occlusal structures of typical Rhipidomys molars. Above: upper left molar row; below: lower right molar row. Homologous elements in the second and third molars are not labelled. Nomenclature from Reig (1977). 80 Fig. 6.1 - Rhipidomys "ochrogaster" and "leucodactylus" from Inka region, Peru: Plot of scores on the first two principal component axes. 92 Fig. 6.2 - Rhipidomys "venustus" and "venezuelae" from N and NW Venezuela: Plot of scores on the first two principal component axes. 93 Fig. 6.3 - Rhipidomys julviventer ("fiilviventer" and "venustus" size classes from Colombia and Mérida, Venezuela) and R. latimanus (from Ecuador and Colombia) : plot of scores on the first two principal component a x e s.^ Fig. 6.4 - Rhipidomys "wetzeli" and "caucensis" from Venezuela and Colombia: plot of scores on the first two principal component axes. 95 Fig. 6.5 - The Rhipidomys julviventer group: plot of scores on the first two component axes (8-variable analysis). 99 Fig. 6.6 - Rhipidomys macconnelli and/?, nitela from Bolivar (Venezuela) and Roraima (Brazil): plot of scores on the first two principal component axes. 108 Fig. 6.7 - Rhipidomys "goodfeliowi", "leucodactylus" and western Andean specimens: plot of scores on the second and third principal component axes. 118 Fig. 6.8 - Rhipidomys "couesi", "cuzco", "goodfellowi", "leucodactylus" and W Andean specimens: plot of scores on the first two principal component axes. 119 Fig. 6.9 - Large-bodied forms of Rhipidomys occurring wholly or partly in Peru: plot of scores on the first three principal component axes. 121 Fig. 6.10 - Large-bodied Rhipidomys from SE Peru to N Argentina: plot of scores on the first two principalcomponent axes. 122 Fig. 6.11- Medium-sized Rhipidomys specimens from central