Phylogenetic Relationships of Oryzomine Rodents (Muroidea: Sigmodontinae): Separate and Combined Analyses of Morphological and Molecular Data
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PHYLOGENETIC RELATIONSHIPS OF ORYZOMINE RODENTS (MUROIDEA: SIGMODONTINAE): SEPARATE AND COMBINED ANALYSES OF MORPHOLOGICAL AND MOLECULAR DATA MARCELO WEKSLER Division of Vertebrate Zoology (Mammalogy), American Museum of Natural History, Graduate Center, City University of New York ([email protected]) Present address: Institute of Arctic Biology, and University of Alaska Museum, University of Alaska Fairbanks BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 296, 149 pp., 48 figures, 8 tables Issued February 16, 2006 Copyright E American Museum of Natural History 2006 ISSN 0003-0090 CONTENTS Abstract.......................................................... 3 Introduction . ...................................................... 3 Oryzomyine Composition and Taxonomic History........................... 4 Phylogenetic Studies of Oryzomyines .................................... 7 The Oryzomys Problem............................................. 10 MaterialsandMethods............................................... 14 Taxonomic Sampling and Morphological Character Scoring. ................. 14 Character Sampling and Description ................................... 15 DataAnalysis.................................................... 16 Results.......................................................... 17 Character Descriptions ............................................. 17 ExternalMorphology............................................ 17 Skull........................................................ 27 Dentition..................................................... 42 PostcranialSkeleton............................................. 52 GlansPenis................................................... 55 MaleAccessoryReproductiveGlands................................. 57 DigestiveSystem................................................ 58 Summary of Morphological Dataset . ................................... 59 PhylogeneticResults............................................... 60 NodalSupport................................................... 69 Discussion . ..................................................... 69 Effects of Different Codings of Polymorphic Data.......................... 69 Effects of Missing Data on Topology and Support ......................... 71 Dataset Comparison ............................................... 72 OryzomyineSynapomorphies......................................... 73 Oryzomyine Relationships ........................................... 74 The ‘‘Oryzomys’’Problem........................................... 75 Oryzomyine Evolution. ............................................. 77 Biogeography .................................................... 82 Acknowledgments.................................................. 89 References........................................................ 90 Appendix 1: Specimens Examined ...................................... 100 Appendix2:SummaryofCharacters.................................... 104 Appendix3:DescriptionofNodes...................................... 122 Appendix 4: Character Transformations in Morphological Tree. ................ 135 Appendix 5: Character Transformations in Combined Tree .................... 142 2 ABSTRACT In this study I provide a phylogenetic hypothesis for the tribe Oryzomyini that can be used to understand the diversification and evolution of this group of rodents and to revise the current generic-level classification. Morphological and molecular data were used for these purposes in combined and separate analyses. Molecular data consisted of partial sequences (1266 bp) from the first exon of the nuclear gene encoding the interphotoreceptor retinoid binding protein (IRBP); the morphological matrix comprised 99 characters, including 16 integumental characters, 32 skull characters, 29 dental characters, 7 postcranial characters, and 10 characters from the phallus and soft-anatomy systems. I present anatomical descriptions for each character, including delineation of different states observed among oryzomyines. Results of the combined analysis were congruent with the IRBP-only dataset for oryzomyine higher-level relationships. Morphological analyses, although showing discrepancies from the combined or IRBP consensus cladograms and with low nodal support values, recovered several clades similar to the combined and IRBP analyses. Systematics of the tribe and the evolution of a few pivotal characters are discussed in light of the proposed phylogeny. Different taxonomic arrangements for species currently included in the genus Oryzomys are suggested. Finally, I evaluate evolutionary and biogeographic hypotheses that are compatible with our current knowledge on oryzomyine relationships. INTRODUCTION Despite such progress, many significant problems remain, especially among the 16 Sigmodontine rodents—the monophyletic extant genera and approximately 115 species group that includes almost all South Amer- currently assigned to the sigmodontine tribe ican muroids and excludes North American Oryzomyini. Oryzomyines are ubiquitous in neotomines and tylomyines (Reig, 1980; the Neotropics, ranging from Tierra del Smith and Patton, 1999; Jansa and Weksler, Fuego to the southern United States. Oryzo- 2004)—have challenged students of mamma- myines occupy forests, savannas, swamps, lian systematics for the past two centuries. scrublands, and semi-arid environments, and After an explosive radiation following an ancestral invasion of South America at the they are often among the most abundant end of the Tertiary (Pardin˜as et al., 2002; small mammals in many of these habitats Steppan et al., 2004), sigmodontines became (Eisenberg, 1999). Most oryzomyines are the most diverse family-level mammalian ordinary-looking rodents that somewhat re- clade in the Neotropical region: with about semble common house rats and mice. Nev- 70 genera and 320 recognized species (Musser ertheless, other oryzomyines display a range and Carleton, 1993), this group now accounts of morphological diversity hardly surpassed for roughly 29% of all Neotropical mammals. by other muroid groups of equivalent taxo- The sheer number of sigmodontine species, nomic rank. Varying in size from small (ca. coupled with pervasive homoplasy in classi- 10 g) to large (ca. 300 g), most oryzomyines cally studied character systems such as the are predominantly cursorial, but some species skull and dentition, has made rigorous testing display marked specializations for arboreal of phylogenetic hypotheses difficult. System- or semiaquatic (amphibious) life. atic research during the last several decades, Long considered a basal group in the however, has improved our understanding of radiation of Neotropical muroids (e.g., by sigmodontine relationships at all taxonomic Hershkovitz, 1962; Gardner and Patton, levels (e.g., Voss, 1988, 1991, 1993; Smith 1976; Reig, 1986), oryzomyines are now and Patton, 1993; Voss and Carleton, 1993; thought to be nested among other derived Steppan, 1995; Bonvicino and Weksler, 1998; sigmodontine clades (Steppan, 1995; Engel et Musser et al., 1998; Smith and Patton, 1999; al., 1998; Smith and Patton, 1999; D’Elı´a, Bonvicino and Moreira, 2001; Geise et al., 2003; Pacheco, 2003; Weksler, 2003). Al- 2001; Pardin˜as et al., 2002; D’Elı´a, 2003; though the taxonomic composition of the D’Elı´a et al., 2003; Pacheco, 2003; Weksler, Oryzomyini as originally defined and di- 2003). agnosed by Voss and Carleton (1993) has 3 4 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 296 been corroborated by subsequent phyloge- border of palate square or concave, never V- netic studies (Steppan, 1995; Weksler, 2003), shaped, and sometimes provided with a short relationships among members of the tribe are median spine which is never produced onward still unclear. Below, I provide a synopsis of as median palatal ridge; parapterygoid fossa, as viewed from the ventral surface, relatively oryzomyine taxonomic history and summa- shallow with the lateral wall flattened, the rize previous hypotheses of intratribal rela- anterior corner not undercut. Incisors more or tionships. less recurved, their face smooth, not grooved; anterior and posterior cingula present; meso- ORYZOMYINE COMPOSITION AND style (id) and mesoloph (id) united, always TAXONOMIC HISTORY present and well developed.... The structure of the palate and the presence in each molar of Neotropical muroid rodents were original- a fused mesostyle (id) and mesoloph (id) are ly divided into two groups based on the characters which together are sufficient to presence/absence of the mesoloph (id) on distinguish the oryzomyine rodents from any others with which comparison need [sic] to upper and lower molars (Winge, 1887). made. Thomas (1906, 1917) further divided the pentalophodont genera (i.e., taxa with Other authors, however, have not regarded the mesoloph) into an Oryzomys group the differences in palatal morphology as including Oryzomys, Oligoryzomys, Rhago- a sufficient character for separating oryzo- mys, and Oecomys, and a Thomasomys- myines from thomasomyines, and they in- Rhipidomys group, including Thomasomys, cluded both in the same group (e.g., Tate, Delomys, Phaenomys, and Rhipidomys, based 1932d; Vorontsov, 1959; Reig, 1980, 1984, on the morphology of the hard palate and (to 1986). In particular, Vorontsov’s (1959) a lesser degree) the number of mammae. classification of ‘‘hamster-like’’ muroids (in- However, ‘‘oryzomyines’’ were first explicitly cluding sigmodontines, cricetines, neoto-