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PubMedDate not supplied

Comparative karyology in Akodon (Rodentia, Sigmodontinae) from Southeastern Brazil.

Karyotypic comparisons among five Akodon species showed that they shared a substantial proportion of their chromosome complements, indicated by distinct homologies between chromosomes, arms, or arm regions despite that this genus is karyotypically rearranged. A comparison with a related outgroup (Bolomys lasiurus) allowed for the recognition of ancestral and derived karyotypic traits as well as for inferring the direction of several chromosome rearrangements. This study indicated that species with lower diploid chromosome number are derived from species with higher diploid number, mainly by 11 fusions and 1 pericentric inversion while the direction of 5 other rearrangements could not be determined (fusions or fissions). UPGMA analyses of karyologic data indicated a topology like (Bolomys lasiurus (Akodon sp. (A. lindberghi (A. montensis (A. aff. cursor, A. cursor))))).

Animals↗
PubMed1989

Geomydoecus (Mallophaga: Trichodectidae) from Pappogeomys and Zygogeomys pocket gophers (Rodentia: Geomyidae) in central Mexico.

Descriptions and illustrations are given for 13 previously described species and subspecies of Geomydoecus and four new subspecies: G. mexicanus Price and Emerson (type host: Pappogeomys merriami saccharalis (Nelson and Goldman], G. perotensis perotensis Price and Emerson (type host: P. m. estor (Merriam], G. p. irolonis Price and Emerson (type host: P. m. irolonis (Nelson and Goldman], G. traubi Price and Emerson (type host: P. m. merriami (Thomas], G. fulvescens Price and Emerson (type host: P. m. fulvescens (Merriam], G. coronadoi coronadoi Barrera, n. status (type host: P. m. estor), G. c. submerriami, n. ssp. (type host: P. m. merriami), G. c. saccharalis, n. ssp. (type host: P. m. saccharalis), G. merriami Price and Emerson (type host: P. tylorhinus planiceps (Merriam], G. veracruzensis Price and Emerson (type host: P. m. fulvescens). G. polydentatus polydentatus Price and Emerson, n. status (type host: P. zinseri (Goldman], G. p. angustirostris, n. ssp. (type host: P. t. angustirostris (Merriam], G. mcgregori Price and Emerson (type host: P. fumosus (Merriam], G. wernecki wernecki Price and Emerson, n. status (type host: P. zinseri), G. w. planiceps, n. ssp. (type host: P. t. planiceps), G. alcorni Price and Emerson (type host: P. alcorni Russell), and G. trichopi Price and Emerson (type host: Zygogeomys trichopus trichopus Merriam).

Animals↗
PubMed1994

Two new subgenera of chewing lice (Phthiraptera: Trichodectidae) from pocket gophers (Rodentia: Geomyidae), with a key to all included taxa.

The new subgenera Thaelerius and Jamespattonius are described, respectively, for the eight species of Geomydoecus in the thomomyus complex of lice and the four species of Thomomydoecus in the wardi complex. Except for T. byersi Hellenthal & Price from Thomomys bottae (Eydoux & Gervais), these lice are restricted to the Thomomys talpoides (Richardson) complex of pocket gophers and are the only lice found on these hosts. A key is given for the identification of the currently recognized 122 taxa of pocket gopher lice.

Animals↗
PubMed2001

Recurrent amplifications and deletions of satellite DNA accompanied chromosomal diversification in South American tuco-tucos (genus Ctenomys, Rodentia: Octodontidae): a phylogenetic approach.

We investigated the relationship between satellite copy number and chromosomal evolution in tuco-tucos (genus Ctenomys), a karyotypically diverse clade of rodents. To explore phylogenetic relationships among 23 species and 5 undescribed forms, we sequenced the complete mitochondrial cytochrome b genes of 27 specimens and incorporated 27 previously published sequences. We then used quantitative dot-blot techniques to assess changes in the copy number of the major Ctenomys satellite DNA (satDNA), named RPCS. Our analysis of the relationship between variation in copy number of RPCS and chromosomal changes employed a maximum-likelihood approach to infer the copy number of the satellite RPCS in the ancestors of each clade. We found that amplifications and deletions of RPCS were associated with extensive chromosomal rearrangements even among closely related species. In contrast, RPCS copy number stability was observed within clades characterized by chromosomal stability. This example reinforces the suspected role of amplification, deletion, and intragenomic movement of satDNA in promoting extensive chromosomal evolution.

Animals↗
PubMed2002

Phylogenetic relationships, ecological correlates, and molecular evolution within the cavioidea (mammalia, rodentia).

A molecular phylogeny of the rodent superfamily Cavioidea was derived using two nuclear sequences (exon #10 of the growth hormone receptor gene and intron #1 of the transthyretin gene) and one mitochondrial gene (12S rRNA). A combined analysis produced a highly derived and well-supported phylogenetic hypothesis that differed from traditional taxonomy primarily in the placement of two taxa. Kerodon, traditionally included within the subfamily Caviinae with guinea pigs and its relatives, is placed sister to the family Hydrochaeridae and closely aligned with the subfamily Dolichotinae. Inclusion of Hydrochaeris within the Caviidae renders the familial classification paraphyletic. Our data further support the taxonomic separation of the families Agoutidae and Dasyproctidae. Both the molecular and traditional morphological interpretations are assessed in testing an ecological constraints hypothesis regarding social behaviors. Whereas traditional taxonomy is consistent with an environmental constraints explanation for social behavior, the molecular data suggest that phylogenetic effects may be a more important factor in the evolution of social behavior in this group. Although lineage-specific rate heterogeneity was identified in all three molecular data sets, no significant support was obtained for the metabolic rate hypothesis. However, both nuclear genes displayed patterns in accordance with the generation time hypothesis.

Adaptation, Biological↗
PubMed1992

Nucleotide sequence variation in the mitochondrial 12S rRNA gene and the phylogeny of African mole-rats (Rodentia: Bathyergidae).

Mitochondrial DNA (mtDNA) sequence variation was examined in eight taxa of the African rodent family Bathyergidae, as well as in two taxa representative of the Old-World hystricognathid rodent families Petromyidae and Thryonomyidae. A total of 812 bp, constituting domains I-III of the 12S ribosomal rRNA gene, were compared for each taxon. The high levels of intrafamilial mtDNA sequence divergence observed (average 16.8, range 3.5-23.2) support an ancient origin for the five genera, 20-38 Mya. These data do not support the current subfamilial groupings of the Bathyergidae. The eastern African naked mole-rat, Heterocephalus glaber, is the most basal representative of the family, with the silvery mole-rat, Heliophobius, being the next most basal. South African forms [dune, common, and cape mole-rats (Bathyergus, Cryptomys, and Georychus, respectively)] group together. The independent origin of the common mole-rat, relative to the naked mole-rat, suggests that complex social systems evolved in parallel along different bathyergid lineages. The 12S rRNA gene is not evolving at a higher rate within the rodent lineages, relative to that seen for artiodactyls and primates. Bathyergid rodents appear to fall at an extreme end of the spectrum of mammalian variation, with respect to both transition/transversion ratios and divergence, showing much lower transition/transversion ratios than those previously reported for intrafamilial comparisons.

Animals↗
PubMed2005

The evolution of fossoriality and the adaptive role of horns in the Mylagaulidae (Mammalia: Rodentia).

Ceratogaulus, a member of the extinct fossorial rodent clade Mylagaulidae, is the only known rodent with horns and the smallest known horned mammal. The function of the large, dorsally projecting nasal horns on this burrowing animal has been the subject of wide speculation among palaeontologists; suggested uses range from sexual combat to burrowing. Mammals have evolved adaptations for digging repeatedly; horns and other cranial appendages have also evolved numerous times. These two adaptations co-occur in mammals extremely rarely: only two fossil genera (Ceratogaulus and the xenarthran Peltephilus) and no extant mammals are both horned and fossorial. Tracing the evolution of fossoriality in aplodontoid rodents (the larger clade to which Ceratogaulus belongs) reveals that Ceratogaulus descended from ancestors who dug by head-lifting. Whereas this suggests an obvious explanation for the horns of this rodent, evidence from functional morphology, anatomy, phylogeny and geologic context indicates that the horns in Ceratogaulus were used for defence, rather than digging, and evolved to offset increased predation costs associated with spending more time foraging above ground as body size increased.

Adaptation, Biological↗