Karyotypic evolution and phylogeny of Mexican Passalidae (Coleoptera: Polyphaga: Scarabaeoidea)

The chromosomes of 26 taxa from Mexico of the tribes Passalini (three species) and Proculini (23 species) have been studied, increasing the karyotypically known species of the family Passalidae to 56. Karyotypic dynamism is high since the diploid number varies from 18 to 44 in the tribe Proculini. and from 25 to 31 in the tribe Passalini. In addition, supernumerary chromosomes, chromosome heteromorphism, translocations and possible sex multivalents have been found. These results contrast with the numerical conservatism found in related families of the superfamily Scarabaeoidea. However, both tribes are conservative with regard to sex determination, as all species of Proculini have male XY chromosomes whereas species of the Passalini have male XO chromosomes. It is postulated that differences in patterns shown by these two tribes are mainly due to population structure, because many species of Proculini are endemic to restricted areas of Meso and South America, favouring the settlement of karyotypic changes, whereas species of Passalini are distributed over large areas in the lowlands. It is also postulated that the ancestral karyotypic formula of the family is close to 12–14 pairs of autosomes although the ancestral male sex determination may be either XY or XO. At present only a weak relationship between morphological and karyotypic evolution has been found, which together with the marked numerical variability found within and between genera make it difficult to obtain phylogenetic conclusions from karyotypic results.     

Mammalian phylogeny: comparison of morphological and molecular results

In an attempt to resolve the "bushy" part at the root of the eutherian tree, 182 nondental morphological characters from 100 species (79 extant and 21 extinct; 98 mammalian and 2 nonmammalian) were analyzed using two maximum-parsimony tree-building algorithms. Parallel analyses of 2,258 pairwise immunodiffusion comparisons with chicken antisera on 101 mammalian species and of amino acid sequence data of alpha and beta hemoglobins and other published protein sequences were also carried out. The morphological and molecular phylogenies agree in depicting the infraclass Eutheria as consisting of five major clades (thus resolving part of the "bush"). Rates of evolution were also found to be similar in the two types of phylogenies.     

A molecular cytogenetic study of chromosome evolution in chimpanzee

We applied multitude multicolor banding (mMCB) in combination with a novel FISH DNA probe set including subcentromeric, subtelomeric and whole chromosome painting probes (subCTM) to characterize a Pan paniscus (PPA) cell line. These powerful techniques allowed us to refine the breakpoints of a pericentric inversion on chimpanzee chromosome 4, and discovered a novel cryptic pericentric inversion in chimpanzee chromosome 11. mMCB provided a starting point for mapping and high resolution analysis of breakpoints on PPA chromosome 4, which are within a long terminal repeat (LTR) and surrounded by segmental duplications, as well as the integration/expansion sites of the interstitial heterochromatin on chimpanzee chromosomes 6 and 14. Moreover, we found evidence at hand for different types of heterochromatin in the chimpanzee genome. Finally, shedding new light on the human/chimpanzee speciation, karyotypes of three members of the genus Pan were studied by mMCB and no cytogenetic differences were found although the phylogenetic distance between these subspecies is suggested to be 2.5 million years.     

Karyotypic evolution in an originally XY cell line of Drosophila melanogaster

The cell line Ca of Drosophila melanogaster, characterized initially by a nearly diploid and normal male karyotype (XY), was used to study chromosomal variation over a period of 5 years of cultivation in vitro. Some general aspects of cell population dynamics which are in accordance with previous findings are pointed out. Various phenomena regarding chromosomal changes leading to karyotype polymorphism are outlined, with a particular emphasis being given to the sex chromosomes. Accordingly, with the aid of fluorescence analysis, some features of the Y and the X chromosomes providing evidence of an enlargement of the heterochromatin (due to addition and to saltatory replication) are described. Moreover, a case of variation in cell morphology accompanied by karyotypic changes was observed, as well as the emergence of a new cell subline of XX type derived from the original of XY type.     

The first molecular phylogeny of Strepsiptera (Insecta) reveals an early burst of molecular evolution correlated with the transition to endoparasitism

A comprehensive model of evolution requires an understanding of the relationship between selection at the molecular and phenotypic level. We investigate this in Strepsiptera, an order of endoparasitic insects whose evolutionary biology is poorly studied. We present the first molecular phylogeny of Strepsiptera, and use this as a framework to investigate the association between parasitism and molecular evolution. We find evidence of a significant burst in the rate of molecular evolution in the early history of Strepsiptera. The evolution of morphological traits linked to parasitism is significantly correlated with the pattern in molecular rate. The correlated burst in genotypic-phenotypic evolution precedes the main phase of strepsipteran diversification, which is characterised by the return to a low and even molecular rate, and a period of relative morphological stability. These findings suggest that the transition to endoparasitism led to relaxation of selective constraint in the strepsipteran genome. Our results indicate that a parasitic lifestyle can affect the rate of molecular evolution, although other causal life-history traits correlated with parasitism may also play an important role.     

A molecular phylogeny of the peacock-pheasants (Galliformes: Polyplectron spp.) indicates loss and reduction of ornamental traits and display behaviours

The South-east Asian pheasant genus Polyplectron is comprised of six or seven species which are characterized by ocelli (ornamental eye-spots) in all but one species, though the sizes and distribution of ocelli vary among species. All Polyplectron species have lateral displays, but species with ocelli also display frontally to females, with feathers held erect and spread to clearly display the ocelli. The two least ornamented Polyplectron species, one of which completely lacks ocelli, have been considered the primitive members of the genus, implying that ocelli are derived. We examined this hypothesis phylogenetically using complete mitochondrial cytochrome b and control region sequences, as well as sequences from intron G in the nuclear ovomucoid gene, and found that the two least ornamented species are in fact the most recently evolved. Thus, the absence and reduction of ocelli and other ornamental traits in Polyplectronare recent losses. The only variable that may correlate with the reduction in ornamentation is habitat, as the two less-ornamented species inhabit montane regions, while the ornamented species inhabit lowland regions. The implications of these findings are discussed in light of models of sexual selection. The phylogeny is not congruent with current geographical distributions, and there is little evidence that Pleistocene sea level changes promoted speciation in this genus. Maximum likelihood and maximum parsimony analyses of cytochrome b sequences suggest that the closest relatives of Polyplectron are probably the peafowl and the argus pheasants.     

The evolution of reproductive strategies in dasyurid marsupials: implications of molecular phylogeny

Dasyurid marsupials show a remarkable diversity of reproductive patterns ranging from aseasonal polyoestry to restricted annual breeding in which males synchronously die after a brief mating season. Previous studies have categorized dasyurid reproduction into six strategies, defined on the basis of five life-history characters. We provide an up-to-date summary of reproductive traits in dasyurid species and examine the evolution of these characters on a phylogeny for the family recently obtained from DNA sequence data. Our results suggest that reproductive evolution in modern dasyurids is characterized by a basal separation of subfamily lineages employing Strategy II (monoestrous females, restricted breeding season, 11 months to maturity; Dasyurinae) and Strategy V (polyoestrous females, extended breeding season, 8–11 months to maturity; Sminthopsinae). Strategies I (male die-off) and III (facultative polyoestry) appear to have arisen several times from Strategy II or V ancestors, and Strategy IV appears to have arisen within Sminthopsis from a Strategy V ancestor. Strategy VI (aseasonal breeding) has arisen independently in each of the four major dasyurid lineages (tribes), and is highly (but not perfectly) correlated with New Guinean endemism. This scenario is not strongly affected if reproductive characters are optimized on an alternative phylogeny more consistent with morphology-based opinions on species relationships. When evaluated in light of current habitat associations and geographic distributions, the reproductive data suggest that the Miocene diversification of modern dasyurids may have been correlated with the invasion of dry forest or woodland habitats.     

Roberts syndrome: study of 4 new Rgyptian cases with comparison of clinical and cytogenetic findings

Roberts syndrome is a rare autosomal recessive genetic disorder (MIM 268300). It is characterized by pre and postnatal growth retardation, severe shortening of limbs with radial defects, oligodactyly and characteristic facial features. The present study reports 4 new cases of Roberts syndrome from 3 families presenting variable phenotypes. Patients were thoroughly investigated clinically and cytogenetically. By reviewing literature, we compared our cases to those previously reported. The rating severity system proposed by Van den Berg and Francke (30) was applied to correlate the phenotypic and cytogenetics changes. We observed more severe reduction defects in the upper limbs than in the lower limbs. While the main reduction defects in the upper limbs involved the thumb and radius ranging to phocomelia, absent or severely hypoplastic fibula was the main lower limb involvement. We emphasize this finding in the present investigation. Heterochromatin repulsion of chromosomes derived from Roberts syndrome patients is a characteristic cytogenetic abnormality. It was a constant finding in our studied patients demonstrated by DABI stain which supports the possibility that mutations in Roberts syndrome lie in centromere related proteins which may also play a role in body patterning. This was proved recently by Vega et al. (31). Application of the clinical rating score and its correlation with cytogenetic changes showed negative results. Cytogenetic studies in normal obligatory heterozygotes parents showed no changes. Phenotypic variability within the same family as well as between different families was observed. The ascertainment of 4 cases with Roberts syndrome from 3 Egyptian consanguineous families during one year in our department may indicate a high frequency of the Roberts syndrome allele among Egyptians. This confirms the need for molecular studies for early and accurate prenatal diagnosis to prevent such dramatic malformation syndrome.     

Multivariate analysis of karyotypic abnormality in leukemia facilitated by numerical encoding of cytogenetic data

A system is proposed whereby human karyotype data is expressed in quantitative terms rather than in the ISCN (1985) terminology used at present. This recoding facilitates application of multivariate analysis using standard statistical packages. As an example, karyotypes of 714 cases from 11 leukemias (Mitelman, 1983) are here recorded and subjected to discriminant analysis (SPSSx, 1983). Significant karyotypic specificity is apparent in six of the 11 FAB leukemia types. Four others show insignificant levels of specificity, while the last is equivocal. These results merely confirm present views. However, their generation by means of computerized multivariate analysis is novel, and confirms the feasibility of the approach. In this quantitative form, karyotypic data may be combined with any other data of diagnostic or prognostic value. Given such a consolidated data set, desired information concerning any aspect of neoplasia could be extracted via a single procedure.     

Morphological vs. molecular evolution: ecology and phylogeny both shape the mandible of rodents

What actually is the expected pattern relating to molecular and morphological divergence? A phylogenetic correlation is expected; however, natural selection may force morphological evolution away from this expected correlation. To assess this relationship and the way it is modulated by selection, we investigated the radiation of the murine rodents, also called as Old World rats and mice. Regarding their diet, they are diversified as they include many omnivorous as well as specialist taxa. The size and shape of the mandible, a morphological character involved in the feeding process, was quantified and compared with an estimate of molecular divergence based on interphotoreceptor retinoid binding protein (IRBP) sequences. Size and shape of the mandible appeared to be related by an allometric relationship whatever the ecology of the taxa. Small size characterizes most murines, causing a dominance of low size distances; still, the frequency of important size differentiation increases with molecular distances. Regarding shape changes, the pattern is much contrasted between omnivores and specialists. A pattern of phenotypic drift characterizes the mandible evolution of taxa sharing an omnivorous diet. Little saturation occurs over more than 10 million years with regard to the shape of the mandible that appears as a valuable marker of phylogenetic history in this context. In contrast, important morphological distances can occur when specialist taxa are involved, even when the molecular divergence is small. Ecological specialization thus triggers an uncoupling of molecular and phenotypic evolution, and the departure from a phenotypic drift pattern.     

Wolf Hirshhorn syndrome in a case of ring chromosome 4: phenotype and molecular cytogenetic findings

Ring chromosome 4 associates concomitant loss of the telomeric 4p and 4q regions and leads to variable clinical manifestations depending on the size of the deleted chromosomal material. We report on a patient with ring chromosome 4, showing the Wolf-Hirshhorn Syndrome (WHS) phenotype and minor symptoms of distal 4q deletion syndrome; the severity of the signs of WHS masks the symptomatology of the 4q deletion syndrome. The absence of seizures despite the absence of the specific 4p16.3 region with haploinsufficiency of the LETM1 gene is striking. The double telomeric deletion due to the ring chromosome formation confirmed by FISH has been rarely described in WHS.     

Karyotypic conservatism in five species of Prochilodus (Characiformes,Prochilodontidae) disclosed by cytogenetic markers

The family Prochilodontidae is considered a group with well conserved chromosomes characterized by their number, morphology and banding patterns. Thence, our study aimed at accomplishing a cytogenetic analysis with conventional methods (Giemsa staining, silver staining of the nucleolus organizer regions-AgNOR, and C-banding) and fluorescence in situ hybridization (FISH) with 18S and 5S ribosomal DNA probes in five species of the Prochilodus genus (Prochilodus argenteus, Prochilodus brevis, Prochilodus costatus, Prochilodus lineatus and Prochilodus nigricans) collected from different Brazilian hydrographic basins. The results revealed conservatism in chromosome number, morphology, AgNORs 18S and 5S rDNAs location and constitutive heterochromatin distribution patterns. The minor differences observed in this work, such as an Ag-NOR on a P. argenteus chromosome and a distinct C-banding pattern in P. lineatus, are not sufficient to question the conservatism described for this group. Future work using repetitive DNA sequences as probes for FISH will be interesting to further test the cytogenetic conservatism in Prochilodus.     

Mitochondrial phylogeny of notothenioids: a molecular approach to Antarctic fish evolution and biogeography

Antarctic waters represent a unique marine environment delimited by an oceanographic barrier, the Polar Front Zone, and characterized by constant subzero temperatures and presence of sea ice. A group of teleost fish, the Notothenioidei, have adapted to these challenging environmental conditions, undergoing a remarkable diversification. In the present study a total of 798 base pairs, generated from partial sequencing of 16S and 12S mitochondrial ribosomal RNA genes, were examined in 33 notothenioid species representative of all families included in the suborder Notothenioidei. Phylogenetic trees, reconstructed on the basis of sequence data by different methods, indicate that traditional hypotheses on notothenioid systematics and biogeography might be in need of reexamination. Molecular evidence suggests that vicariant speciation could be invoked to explain the early divergence of Eleginops maclovinus, a species previously included in the family Nototheniidae, which is now proposed as the closest sister group to all the rest of notothenioids apart from bovichtids. On the other hand, repeated, independent dispersal through the Polar Front is proposed for the divergence of other subantarctic notothenioid species. Likewise, multiple, independent transitions from benthic to pelagic habit are inferred from molecular data, at variance with the more conservative hypothesis based on cladograms reconstructed from morphological data.     

Karyotypic mosaicism and molecular cytogenetic markers in the scleractinian coral Acropora pruinosa Brook, 1982 (Hexacorallia,Anthozoa, Cnidaria)

Coral Reefs - Molecular cytogenetic investigation was carried out on the scleractinian coral, Acropora pruinosa (A. pruinosa). Conventional Giemsa staining techniques for karyotyping, such as G-...     

Structure and molecular phylogeny of sasA genes in cyanobacteria: insights into evolution of the prokaryotic circadian system

Cyanobacteria are the simplest organisms known to have a circadian system. In addition to the three well-studied kai genes, kaiA, kaiB, and kaiC, an important element of this system is a two-component sensory transduction histidine kinase sasA. Using publicly available data of complete prokaryotic genomes, we performed structural and phylogenetic analyses of the sasA genes. Results show that this gene has a triple-domain structure, and the domains are under different selective constraints. The sasA gene originated in cyanobacteria probably through the fusion of the ancestral kaiB gene with a double-domain, two-component sensory transduction histidine kinase. The results of the phylogenetic analyses suggest that sasA emerged before the kaiA gene, about 3,000-2,500 MYA, and has evolved in parallel with the evolution of the kaiBC cluster. The observed concordant patterns of the sasA and kaiBC evolution suggest that these genes might compose an ancient KaiBC-SasA-based circadian system, without the kaiA gene, and that such a system still exists in some unicellular cyanobacteria.     

The evolution of social behaviour in sentinel crabs (Macrophthalmus): implications from molecular phylogeny

Crabs of the genus Macrophthalmus are known to exhibit highly developed and diverse social behaviour, such as allocleaning, fighting and waving display behaviour, the first being observed widely throughout the genus. Fighting behaviour between males has been classified previously into grasping fighting and claw‐extending fighting, and male waving display into four patterns, the vertical non‐forward‐pointing type, vertical forward‐pointing type, lateral non‐forward‐pointing type and lateral forward‐pointing type, on the basis of interspecific behaviour comparisons. To understand the evolutionary pathways of these social behavioural activities, 978‐bp nucleotide sequences from mitochondrial 16S rRNA genes of 21 species, including two outgroup taxa, were analysed and a molecular phylogeny was reconstructed. The resultant tree demonstrated striking inconsistencies with the relationships inferred from morphological features. Species with similar habitat conditions showed similar morphological features, although they were not phylogenetically close relatives. Phylogenetic analysis of allocleaning behaviour suggested that it evolved once in the early history of the lineage. The analysis of fighting behaviour demonstrated that species with claw‐extending fighting, being a more complex behaviour than grasping fighting, are found in the most ancestral part of the phylogeny. The analysis also revealed that claw‐extending fighting has evolved secondarily on two occasions, suggesting that fighting behaviour is not characterized by sufficient phylogenetic components. The superimposition of a waving pattern on to the phylogeny indicated that the lateral non‐forward‐pointing type has evolved from the vertical non‐forward‐pointing type, the lateral forward‐pointing type having evolved from the vertical forward‐pointing type. This scenario also appeared reasonable with respect to the behavioural trends of cheliped movements in waving. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88 , 45–59.     

The molecular evolution of the alcohol dehydrogenase locus and the phylogeny of Hawaiian Drosophila.

DNA sequences in the alcohol dehydrogenase genes of flies representing the major groups of Hawaiian Drosophila are used to clarify the relationships of these groups, among themselves and with mainland Drosophila. The topology of the tree derived from these sequences agrees with karyotypic and morphological data but disagrees, in part, with the results of an earlier study that used immunological comparisons between variants of a larval hemolymph protein. A time scale, derived from a comparison of closely related Hawaiian Drosophila species, provides divergence-time estimates that are substantially more recent than those obtained from the immunological studies, although they are still within the bounds set by fossil and biogeographical evidence. The two major lineages of Hawaiian Drosophila, the scaptomyzoids and the drosophiloids, are shown to be widely separated from one another. The scaptomyzoids appear to have diverged early in the history of the subgenus Drosophila, greater than 25 Mya. While hundreds of scaptomyzoid species are found in the Hawaiian archipelago, many fewer are found elsewhere around the world, suggesting that they could have originated outside Hawaii. The drosophiloid lineage is strictly endemic to Hawaii and originated little more than 10 Mya, according to the alcohol dehydrogenase molecular clock. Thus, Drosophila apparently inhabited the Hawaiian archipelago (greater than or equal to 5 Myr before the emergence of the oldest existing high island, Kauai, 5 Mya.