Phylogeny and evolution of African shrews (Mammalia: Soricidae) inferred from 16s rRNA sequences

Current phylogenetic hypotheses on the African Crocidurinae (Soricidae) are based upon morpho-anatomical, karyological, and allozyme studies. The present study attempts to resolve the interrelationships among African Crocidurinae and their relationships to Eurasian Crocidurinae and to the subfamily Soricinae, on the basis of partial mitochondrial 16s rRNA sequences (549 bp). This is the first molecular study to include all but one of the nine currently recognized African shrew genera. In agreement with current views, two major lineages emerge. The first lineage includes Myosorex and Congosorex and supports the existence of a myosoricine taxon. The second lineage includes the six remaining genera. The genus Sylvisorex appears to be polyphyletic, whereas species of the controversial genus Crocidura are monophyletic. The genus Suncus presumably originated in Africa. The monospecific genera Ruwenzorisorex and Scutisorex and the two representatives of Paracrocidura cluster with species of other genera. Grouping patterns of species from different continents suggest that there have been multiple exchanges between Africa and Eurasia. The time estimates of these exchanges, inferred from two independent fossil-based calibrations of a molecular clock, coincide with the time estimates for migration events in other mammalian taxa.     

Esterase-16 (ES-16) of the rat (Rattus norvegicus): Identification and genetic characterization

Esterase-16, an esterase present in lung and other tissues of the laboratory rat, has been characterized by its biochemical properties (electrophoretic mobility, substrate pattern, sensitivity to inhibitors) and genetic variation in 107 inbred strains and substrains including 14 RI strains. It was classified as a carboxylesterase (EC 3.1.1.1). The phenotype ES-16A (BN/Han and 63 other strains) was defined as a narrow electrophoretic band migrating between ES-1A and ES-13A, ES-16B (LEW/Han and 42 other strains) exhibited the same electrophoretic mobility as ES-16A but was distinguished by its extremely weak activity. Segregation of ES-16 in RI strains and backcrosses indicated linkage to linkage group V (LGV). The Es-16 locus was tentatively placed into esterase cluster 2 and homology with Es-7 of the house mouse is proposed.     

Light conditions and the evolution of heteroblasty (and the divaricate form) in New Zealand

Heteroblasty, changes in vegetative phenotype during ontogeny, is unusually common in the New Zealand flora. Some feature(s) unique to the New Zealand situation must have influenced the evolution of this strategy. Similarities were examined between the ontogenetic changes in phenotype and growth strategy in Elaeocarpus hookerianus, Carpodetus serratus and Pseudopanax crassifolius. Variation in hypothesised light capture efficiency of juvenile and adult forms can be related to changes in the light environment that these growth forms experience. Heteroblasty is hypothesised to have evolved as a result of the change from a low light intensity environment below the canopy of high altitude conifer/broad-leaved forests, to a high light intensity environment above the canopy. The differences in architecture between juvenile E. hookerianus and C. serratus on the one hand, and P. crassifolius on the other hand, are likely to be related to their adaptation to heterogeneous moderate light intensity and homogeneous low light intensity, respectively. The divaricate form characteristic of many New Zealand shrubs may have arisen following the development of heteroblastic trees with a divaricate juvenile, and the subsequent loss of the adult state. This paper provides hypotheses which future research can scientifically test.     

Mitogenome evolution in Cephini (Hymenoptera: Cephidae): Evidence for parallel adaptive evolution

Two mitogenomes of remarkable size of the stem-boring sawflies, Trachelus tabidus (18539 bp) and T. iudaicus (20730 bp), were characterized and compared with previously known mitogenomes of Cephini. A rearrangement in the IQM gene cluster, an unusual elongation in rrnS gene and supposedly functional tandem repeat sequences in the A+T-rich region are synapomorphies of Cephini. Mitogenome evolution of the Cephini was investigated in a dataset of seven species representing all genera. The noticeably divergent mitogenomes of the Cephini both at nucleotide and amino acid level, and the variable rates of ω values, indicate the effects of different selective forces, rather than neutral evolution. The effect of positive selection is revealed by radical amino acid changes with ten physicochemical properties (P_α, B_r, pK′, h, E_l, H_nc, α_c, α_n, R_a and H_p) throughout each branch of the tree. The radical changes in the ND and ATP complexes are mostly related to chemical and energetic properties due to different energy requirements among species. The phenology of Cephini species and their host plants, together with habitat structure, rather than host plant preferences or phylogenetic constraint, are suggested to explain the role of adaptive evolution in shaping Cephini mitogenomes.     

Fragile site (16) (q22)

Summary The rare autosomal fragile site, fra (16)(q22), is the most common of all rare autosomal fragile sites and has a heterozygote frequency of about 5%. Evidence for it was found following the segregation expected from a simple codominant trait with complete penetrance; this is in contrast to a variety of other rare autosomal fragile sites. Based on the analysis of 12 families in which fra (16)(q22) is segregating, we found that, whereas complete penetrance could be confirmed, the transmitting parent was significantly more likely to be of the female sex. On the other hand, there was no evidence for preferential transmission to offspring of either sex.     

Phylogenetic position of Phthiraptera (Insecta: Paraneoptera) and elevated rate of evolution in mitochondrial 12S and 16S rDNA

Phthiraptera (chewing and sucking lice) and Psocoptera (booklice and barklice) are closely related to each other and compose the monophyletic taxon Psocodea. However, there are two hypotheses regarding their phylogenetic relationship: (1) monophyletic Psocoptera is the sister group of Phthiraptera or (2) Psocoptera is paraphyletic, and Liposcelididae of Psocoptera is the sister group of Phthiraptera. Each hypothesis is supported morphologically and/or embryologically, and this problem has not yet been resolved. In the present study, the phylogenetic position of Phthiraptera was examined using mitochondrial 12S and 16S rDNA sequences, with three methods of phylogenetic analysis. Results of all analyses strongly supported the close relationship between Phthiraptera and Liposcelididae. Results of the present analyses also provided some insight into the elevated rate of evolution in mitochondrial DNA (mtDNA) in Phthiraptera. An elevated substitution rate of mtDNA appears to originate in the common ancestor of Phthiraptera and Liposcelididae, and directly corresponds to an increased G+C content. Therefore, the elevated substitution rate of mtDNA in Phthiraptera and Liposcelididae appears to be directional. A high diversity of 12S rDNA secondary structure was also observed in wide range of Phthiraptera and Liposcelididae, but these structures seem to have evolved independently in different clades.     

Midline (dermoid) cysts of the floor of the mouth: report of 16 cases and review of surgical techniques

A retrospective review of 16 cases of midline (dermoid) cysts of the floor of the mouth is presented, evaluating the different surgical approaches. Sixteen cases of patients with a diagnosis of midline cyst of the floor of the mouth, treated at the Maxillofacial Surgery Department of the School of Medicine and Surgery of the "Federico II" University of Naples (Naples, Italy), were observed over a 10-year period, between 1988 and 1998; age, sex, localization, diagnostic technique, and type of treatment were evaluated. Male patients were more frequently affected, with a male-to-female ratio of 3:1 (12:4 cases). Patients ranged in age from 5 to 51 years (average age, 27.8 years). The preoperative assessment was made using ultrasonography in all cases but one, computed tomography in eight cases, and magnetic resonance imaging in three cases. Regarding surgical techniques used, a transcutaneous approach was adopted for median geniohyoid cysts, an extended median glossotomy technique was used for very large median genioglossal cysts, a median glossotomy technique was used for median genioglossal cysts, and a midline incision of the oral mucosa along the lingual frenulum was used for sublingual cysts. During the postoperative course, there were no complications except for modest edema in three cases. Follow-up ranged between 24 months and 12 years; no relapses or malignant changes were observed. In the authors' experience, the intraoral approach was also effective for the treatment of large lesions and led to very good cosmetic and functional results, whereas the extraoral incision was necessary only when the cysts were under the geniohyoid muscle.     

SRY evolution in Cebidae (Platyrrhini: Primates)

Sex determination in mammals is dependent on the presence of SRY, which codes for a protein with a DNA binding motif (the HMG-box domain). Here we analyze the evolution of SRY among seven genera of New World monkeys belonging to the family Cebidae. Estimates of the number of synonymous and nonsynonymous substitutions indicated the absence of positive selection acting on SRY evolution. The presence of indels at the C-terminus coding region in different genera and species maintained an open reading frame, indicating a selective pressure constraining the evolution of this coding region. Available data on the fertility of natural and captive interspecific hybrids failed to show any relationship between SRY evolution and speciation for the genera herein studied. Our phylogenetic arrangement for Cebidae genera was similar to previous topologies based on mitochondrial and autosomal DNA sequences. This arrangement also corroborated the division of Cebus into two species groups. However, for Callithrix the differences among SRY topology and those derived from autosomal and mitochondrial genes suggested a Y-chromosome ancestral polymorphism.     

Increased Expression of Phosphatidylcholine (16:0/18:1) and (16:0/18:2) in Thyroid Papillary Cancer

A good prognosis can be expected for most, but not all, cases of thyroid papillary cancer. Numerous molecular studies have demonstrated beneficial treatment and prognostic factors in various molecular markers. Whereas most previous reports have focused on genomics and proteomics, few have focused on lipidomics. With the advent of mass spectrometry (MS), it has become possible to identify many types of molecules, and this analytical tool has become critical in the field of omics. Recently, imaging mass spectrometry (IMS) was developed. After a simple pretreatment process, IMS can be used to examine tissue sections on glass slides with location information.Here, we conducted an IMS analysis of seven cases of thyroid papillary cancer by comparison of cancerous with normal tissues, focusing on the distribution of phospholipids. We identified that phosphatidylcholine (16:0/18:1) and (16:0/18:2) and sphingomyelin (d18:0/16:1) are significantly higher in thyroid papillary cancer than in normal thyroid tissue as determined by tandem mass (MS/MS) analysis. These distributional differences may be associated with the biological behavior of thyroid papillary cancer.     

The origin and evolution of Eragrostis tef (Poaceae) and related polyploids: evidence from nuclear waxy and plastid rps16

Tef (Eragrostis tef; Poaceae) is an allotetraploid (2n = 4x = 40) cereal crop whose origin within the large genus Eragrostis is unknown. Previous studies have suggested a total of 14 wild Eragrostis species as potential progenitors. Phylogenetic analysis of sequence data from the nuclear gene waxy and the plastid locus rps16 strongly supports the widely held hypothesis of a close relationship between tef and E. pilosa, a wild allotetraploid. Eragrostis heteromera, another previously proposed progenitor, is shown by the waxy data to be a close relative of one of the tef genomes. Other putative progenitors included in the taxon sample are not supported as closely related to tef. Plastid sequences from five varieties of tef and four E. pilosa accessions are identical and therefore are uninformative with respect to the question of multiple origins of these polyploids. The waxy phylogeny also resolves the relationships among other allopolyploids, supporting a close relationship between the morphologically similar allotetraploids E. macilenta, E. minor, and E. mexicana. Eragrostis cilianensis, another morphologically similar allopolyploid, appears to have shared one diploid progenitor with these species but derived its other genome from an unrelated diploid.     

Parallel evolution of Myobiidae (Acari: Prostigmata) mites and jerboas (Rodentia: Dipodoidea)

The phenomenon of the parallel evolution is considered with the example of the myobiid mites (Acari: Prostigmata: Myobiidae) and the jerboas (Rodentia: Dipodoidea). According to recent phylogenetic studies of the superfamily Dipodoidea it is separated into 4 family: Allactagidae, Dipodidae, Zapodidae and Sminthidae (Shenbrot e. a., 1995). The myobiid mites of the subenus Dipodomyobia (11 species) of the genus Cryptomyobia are known as specific parasites associated with jerboas of the families Dipodidae and Allactagidae. One more species (Radfordia ewingi) considered as incertae sedis species within the genus Radfordia is found on the jerboas of the family Zapodidae. The myobiid mites are apparently absent on the members of the family Sminthidae. The reconstruction of phylogeny of the myobiid subgenus Dipodomyobia was carried out by the cladistic method (software PAUP 3.0 s). The analysis was based on 13 morphological characters. At the first step of analysis 42 parsimonious trees have been obtained. The strict consensus tree displays one distinct cluster, which incorporates mites of the allactaga species of group restricted to the jerboa family Allactagidae, and several plesions, species of which are usually refferred to as dipi species group and associated with the family Dipodidae (fig. 1). At the second step of analysis, two characters, which appeared as homoplasies at the first step of analysis were excluded, and one new characters (structure of male genital shield) was additionally included. Single cladogram obtained displays two general clusters and one plesion. The first cluster comprises the allactaga species group (parasites of Allactagidae). The second cluster incorporates the dipi species group, the parasites of subfamilies Dipodinae and Paradipodinae of Dipodidae). The plesion is represented by one species Cryptomyobia baranovae being a specific parasite of Salpingotus crassicauda (Cardiocraninae, Dipodidae). There is the high level congruence between the pattern of myobiid cladogram and jerboas phylogeny proposed by Shenbrot (1992) (fig. 2). The position of one species C. paradipi (the parasite of Paradipus ctenodactylus, single representative of subfam. Paradipodinae) does not fit to this phylogenetic system of the jerboas. This mite species belongs to the claster dipi. All others myobiid species of this group are the parasites of the subfamily Dipodinae. In the cladogram of jerboas, the subfam. Paradipodinae is a sister group of Cardiocraninae, but not of Dipodinae, as it is suggested by the parasitological data. If sinapomorphies in the node Paradipodinae--Cardiocraninae are not correct (as Shenbrot admitted), there would be a complete congruence between the phylogenetic pattern of myobiid and of jerboas. The general phylogeny of Dipodoidea based on citogenetical data was proposed by Vorontsov e. a. (1971). 3 families only were recognized within Dipodoidea: Zapodidae, Sminthidae and Dipodidae. The latter family included 3 subfamilies: Dipodinae, Cardiocraninae and Allactaginae. The version of the jerboa phylogeny proposed in the present paper based on parasitological data corresponds in general lines to the hypotesis of Vorontsov e. a. (1971). The myobiid mites are absent on Sminthidae, they are represented by one species incertae sedis on Zapodidae, and by the subgenus Dipodomyobia on others jerboas (Dipodidae sensu Vorontsov e. a.). According to the parasitological data, the subfamilies Dipodinae and Allactaginae are the sister groups, because the myobiid mites of the subgenus Dipodomyobia parazitise on the jerboas of these taxa only. The subfamily Paradipodinae (sensu Shenbrot) is a sister group for Dipodinae, as far as species C. paradipi is the sister species to other members of the dipi group. The subfamily Cardiocraninae is a sister group for the node Dipodinae-Paradipodinae and also should be included to Dipodidae, because the aberrant species C. baranovae is obviously related to the dipi species group.     

Contents Volume 16 (2002)

Volume Contents

Contents Volume 16 (2002)