Molecular phylogeny of the Praomys complex (Rodentia: Murinae): a study based on DNA/DNA hybridization experiments.

Within the Murinae (Muridae: Rodentia), the African rats of the Praomys group, whose systematics has been studied through different approaches, have raised numerous taxonomic problems. Different taxa related to Praomys have successively been described, among which Mastomys, Myomys and Hylomyscus were considered either as separate genera or subgenera of Praomys. In order to clarify the relationships within the Praomys group, we conducted a series of DNA/DNA hybridization experiments involving different species of Praomys, Mastomys, Myomys and Hylomyscus plus other Murinae and a Cricetomyinae. This study indicates that the Praomys complex is a monophyletic entity clearly separated from the other African and Asian Murinae. If Mastomys and Hylomyscus appeared to be independent genera, the taxonomic situation of Praomys and Myomys is more difficult to ascertain. Indeed, Praomys tullbergi appears more closely related to Myomys daltoni than to another species of Praomys , namely P. jacksoni , suggesting paraphyly for Praomys. Furthermore, P. jacksoni is as distant from P. tullbergi as from any species of Mastomys. Additional species of Praomys and, especially, of Myomys , are needed for reaching a definitive conclusion on these latter taxa. The Praomys group is more related to Mus than to Rattus. To calibrate our molecular distances with geological time, we used a dating of 10 Myr for the Musi Rattus dichotomy. The inferred rate of molecular evolution suggests a dating of c. 8 Myr for the separation of the Praomys group from the Mus lineage.     

Growth of Neural Crest Cells In Vitro Is Enhanced By Extracts From Silky Fowl Embryonic Tissues

In the Silky Fowl (SF) breed of chicken, most of the internal organs are infiltrated with melanocytes. Previous studies have shown that this generalized mesodermal pigmentation is not due to a cell autonomous abnormality of the melanocytes but to environmental factors able to promote both the homing of pigment cell precursors in abnormal embryonic sites and their proliferation and differentiation. To analyse the mode of these environmental cues, we tested the effect of SF embryo extract (SFEE) on cultured quail neural crest cells as compared with that of EE from normal chickens of the JA57 strain (JA57EE). We found that SFEE enhances crest cell proliferation as judged by ³H-TdR incorporation and cell counting. In contrast, no effect of SFEE was observed either on the proportion of cultured cells that are engaged into the melanocytic differentiation pathway or on the amount of melanin produced by each differentiated pigment cell. The simple observation, however, reveals that SFEE has a significant effect on pigmentation of the cultured quail neural crest cells. This effect has therefore to be accounted for by the general increase in cell number induced by SFEE. The question is raised as to whether the in vivo SF phenotype is generated exclusively by this mechanism.     

Ecological distribution and niche segregation of sibling species: the case of bean beetles, Acanthoscelides obtectus Say and A. obvelatus Bridwell

Abstract.  1. Molecular techniques have greatly added to the number of known sympatric cryptic species in insects. Ecological differences between these newly distinguished species are little explored, but niches often appear to overlap strongly. These cases are good models for exploring new ideas about species coexistence and community structure.
2.  Acanthoscelides obtectus and A. obvelatus are two sister species of bean bruchids, which have been confused until the last decade. One important ecological difference between them has emerged, however: A. obtectus is multivoltine and now distributed worldwide, whereas A. obvelatus is univoltine and restricted to Mesoamerica. Where their ranges overlap, the two species share the same host plants and larvae can sometimes complete development in the same seed.
3. The analysis of 27 622 Mexican individuals of the two species in 2001-2002 and 2002-2003 indicates that their niches overlap, but are differentiated with respect to altitude and the kind of beans (wild vs. domesticated). The principal patterns in their relative abundance in different habitats, and at different seasons, were constant from one year to the next.
4. As sympatry of these species seems to be of recent origin, the observed niche differentiation may not have evolved in response to competition, but could instead be the consequence of physiological differences, evolved independently in each species in allopatry, that pre-adapted them for different altitudes and kinds of resources.
5. The combination of biological and historical factors thus appears to allow these two sibling species to coexist in sympatry, despite their broadly overlapping ecological niches.     

Evolutionary systematics of the Indian mouse Mus famulus Bonhote, 1898: molecular (DNA/DNA hybridization and 12S rRNA sequences) and morphological evidence

The genus Mus encompasses 38 species of mice divided into four subgenera: Mus , Pyromys , Nannomys and Coelomys . Each of these four taxa is characterized by discrete morphological as well as biochemical traits. We used two different molecular approaches to determine the relationships between these subgenera: DNA/DNA hybridization and 12S rRNA mitochondrial sequences. We compared the resulting phylogenies from each method and with phylogenies derived from morphological data. The degree of resolution of each molecular approach is discussed. The two molecular studies indicate that Mus , Pyromys , Nannomys and Coelomys are clearly distinct monophyletic groups, as previously indicated by morphological data and other biochemical and molecular approaches. There is one divergence between previous morphological and the molecular and morphological studies presented here: the position of the Indian species Mus famulus . This taxon, which was formerly included in the subgenus Coelomys , is demonstrated here to belong to the subgenus Mus. We also propose the following relationships within Mus sensu lato : Mus and Pyromys are the closest relatives, followed by Nannomys and Coelomys , whose relationships are still unclear. This arrangement is more robustly supported by DNA/DNA hybridization than by 12S rRNA data. A molecular time scale for the evolution within Mus sensu lato is proposed, using as a reference the Mus/Rattus divergence estimated by the fossil record at around 12 mya.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 137 , 385–401.     

Characterization of five new bovine dinucleotide repeats

Five new bovine (TG)n microsatellite sequences were characterized. During the screening procedure, one-third of the clones had essentially the same flanking sequences. A fast technique was devised to eliminate these clones.     

Five polymorphic microsatellite markers for the study of Cardiocondyla elegans (Hymenoptera: Myrmicinae)

We describe primer sequences for five microsatellite markers in Cardiocondyla elegans, an ant species with ergatoid males. Polymorphism of these loci was investigated using 236 individuals from 22 colonies from four locations. The microsatellites are dinucleotide repeats with four to 16 alleles, and the observed heterozygosity ranges from 0.244 to 0.720. We characterized these markers for the study of the population as well as the social structure of colonies.