Specific limits and emerging diversity patterns in East African populations of laminate-toothed rats, genus Otomys (Muridae: Murinae: Otomyini): Revision of the Otomys typus complex

Abstract

We combined evidence from biogeography, craniodental traits, linear and geometric morphometrics (233 skulls), cytogenetics (karyotypes of 18 individuals) and mitochondrial DNA sequences (44 cytochrome b and 21 12S rRNA sequences) to test species limits within Otomys typus s.l. (Muridae: Murinae: Otomyini), a complex that is patchily distributed across alpine zones of Ethiopia and East Africa. Our results confirm the specific validity of O. dartmouthi, O. jacksoni, O. orestes, and O. uzungwensis, forms recently removed from synonymy under typus s.l.; support elevation of four other alpine forms to species (O. fortior, O. helleri, O. thomasi, and O. zinki); identify three additional new species (O. cheesmani sp. nov., O. simiensis sp. nov., O. yaldeni sp. nov.); and enable redefinition of O. typus s.s. as a species restricted to certain mountains west of the Great Rift Valley in Ethiopia (Simien and Guna Mountains in the north, extending to the highlands of the western rim of the Rift Valley). Phylogenetic interpretation of the cytochrome b data clearly demonstrates that the alpine morphotype once united under O. typus s.l. has originated independently at high elevations on several mountain ranges in eastern and northeastern Africa; although generally adapted to high-elevation vegetation, such alpine species are ecologically segregated from one another. Patterns of morphometric, genetic, and ecological differentiation among populations once misassigned to nominal O. tropicalis and O. typus more parsimoniously reflect regional cladogenesis along elevational gradients, rather than multiple, successive colonization by different ancestral forms from southern Africa as earlier supposed. Although incomplete and preliminary, information gathered for O. tropicalis indicates that it too is a species composite; several lines of research are discussed to redress its polyphyletic content. Our results, together with other recent taxonomic studies of Otomys, appreciably elevate the level of endemism within eastern Africa and underscore the significance of Africa's eastern highlands to the continental diversification of Otomyini.

Molecular phylogeny of Panaspis and Afroablepharus skinks (Squamata: Scincidae) in the savannas of sub-Saharan Africa

“…Although most of our recovered lineages are not considered to be Afromontane, their divergences might be explained by the irregular physiography seen along the areas where these populations occur. This pattern of micro-endemism has been documented in other skinks (Parham and Papenfuss, 2009), geckos (Travers et al, 2014), chameleons (Glaw et al, 2012), chelonians (Daniels et al, 2007; Petzold et al, 2014), birds (Huseman et al, 2013), and mammals (Taylor et al, 2011; Stoffberg et al, 2012). For example, Tanzania has two populations that are separated by the Great Rift Valley: P .…”

Molecular phylogenetic analyses indicate paraphyly of the genusHybomys(Rodentia: Muridae): Taxonomic implications

“…badius , respectively. Molecular genetic analyses are increasingly used to delimit species, particularly in rodents (Baker & Bradley, ; Bryja et al., , ; Granjon & Montgelard, ; Taylor et al., ). In the following paragraphs, we discuss the status of rufocanus and eisentrauti based on our DNA sequence data, and data from the literature.…”

Molecular and morphological evidence for a Pleistocene radiation of laminate-toothed rats (Otomys: Rodentia) across a volcanic archipelago in equatorial Africa

“…The availability of a series of 25 recently collected (by CD, VN, ADM) specimens from Mt Oku, provisionally identified as O. occidentalis , and a single O. burtoni individual from Mt Cameroon, allowed us to make molecular comparisons with other West, East and Central African Otomys taxa. Molecular comparisons were based on available published (Maree, ; Taylor et al ., 2009a; 2011) cyt b sequences of 15 East African species and subspecies ( angoniensis , barbouri , lacustris , denti , jacksoni , tropicalis tropicalis , t. elgonis , t. faradjius , zinki , dartmouthi , uzungwensis , simiensis, fortior, helleri and typus ) and four additional southern African species ( Parotomys brantsii , P. littledalei , O. angoniensis and O. irroratus ) (Table ). Although Parotomys is normally regarded as a distinct genus from Otomys (Musser & Carleton, ), its monophyly has been questioned by Taylor et al .…”

“…Several new species of Otomys have been described recently and we follow the classification and nomenclature of Taylor et al . () and Taylor () who recognize 31 species of Otomyinae. Nine murine genera were selected as outgroups (Watrous & Wheeler, ) to represent a range of divergent rodent lineages of successive relatedness to the Otomyini, and to include taxa with fossil dates which could be used for calibration as discussed below: Arvicanthis , Aethomys , Batomys , Lemniscomys , Micaelamys , Mus , Oenomys , Phloeomys and Rattus (Table ; Lecompte et al ., ; Rowe et al ., ).…”