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PubMed2005

Systematics and evolution of the subfamily Gerbillinae (Mammalia, Rodentia, Muridae).

Although they represent a quarter of the mammalian species, the evolutionary relationships among as well as within, the main murid lineages are still controversial. The subfamily Gerbillinae is no exception as previous studies based on morphological, karyotypical, and allozyme characters are highly incongruent. Here, we present the first molecular phylogeny for gerbils based on cytochrome b and 12S rRNA mitochondrial genes. Results are largely congruent between the two genes as well as with the concatenated data set with most of the nodes being well-supported. Based on the topologies retrieved here, we (1) propose the identification of three main clades, (2) support the split of Tatera genus into an Asian and an African group, the latter including Gerbillurus species, and (3) provide some evidence towards the inaccuracy of subgeneric divisions within both Gerbillus and Meriones. In addition, the sharp contrast between the genetic characters and morphological data sets suggest high levels of convergence, probably as a result of strong environmental constraints imposed on these rodents adapted to arid and semi-arid regions. Finally, molecular datings for the various cladogenetic events are in good agreement with the known gerbilline fossil record and support an African origin with subsequent migrations to Asia.

Africa↗

PubMed2003

Evolution of the army ant syndrome: the origin and long-term evolutionary stasis of a complex of behavioral and reproductive adaptations.

The army ant syndrome of behavioral and reproductive traits (obligate collective foraging, nomadism, and highly specialized queens) has allowed these organisms to become the premiere social hunters of the tropics, yet we know little about how or why these strategies evolved. The currently accepted view holds that army ants evolved multiple times on separate continents. I generated data from three nuclear genes, a mitochondrial gene, and morphology to test this hypothesis. Results strongly indicate that the suite of behavioral and reproductive adaptations found in army ants throughout the world is inherited from a unique common ancestor, and did not evolve convergently in the New World and Old World as previously thought. New Bayesian methodology for dating the antiquity of lineages by using a combination of fossil and molecular information places the origin of army ants in the mid-Cretaceous, consistent with a Gondwanan origin. Because no known army ant species lacks any component of the army ant syndrome, this group represents an extraordinary case of long-term evolutionary stasis in these adaptations.

Adaptation, Physiological↗

PubMed2005

Modelling the interactions between phenology and insecticide resistance genes in the codling moth Cydia pomonella.

In the codling moth Cydia pomonella (L), insecticide resistance genes have been associated with pleiotropic effects affecting phenology. In this paper, we investigated whether an increase in the frequency of insecticide resistance in field populations of C pomonella was likely to entail significant divergences in the temporal occurrence of both susceptible and insecticide-resistant individuals. For this purpose, we built a phenological model that provided suitable predictions of the distinct and diverging seasonal evolutions of populations of a susceptible and two insecticide-resistant (at two and three loci) homozygous genotypes of C pomonella. Model simulations for each genotype were further compared with pheromone trap catches recorded in a field insecticide-treated population over an 8-year period (from 1992 to 2000), which reflected the progressive annual increase in the frequency of resistance in southeastern France. We found a significant delay in field adult emergence relative to those predicted by the homozygous susceptible model, and the magnitude of such a delay was positively correlated with increasing frequencies of insecticide resistance in the sampled field population of C pomonella. Adult emergence predicted in the theoretical population that was homozygous for resistance at two loci converged with those recorded in the field during the investigated 8-year period. This suggested that the pleiotropic effects of resistance were likely to result in a significant phenological segregation of insecticide-resistant alleles in the field. The results of this study emphasized the potential for pest populations exposed to chemical selection to evolve qualitatively with respect to phenology. This may raise critical questions regarding the use of phenological modelling as a forecasting tool for appropriate resistance management strategies that would take into account the diverging seasonal evolutions of both insecticide resistance and susceptibility.

Animals↗

PubMed1997

Fluorescene in situ hybridization establishes homology between human and silvered leaf monkey chromosomes, reveals reciprocal translocations between chromosomes homologous to human Y/5, 1/9, and 6/16, and delineates an X1X2Y1Y2/X1X1X2X2 sex-chromosome system.

We employed in situ hybridization of chromosome-specific DNA probes ("chromosome painting") of all human chromosomes to establish homologies between the human and the silvered lead monkey karyotypes (Presbytis cristata 2n = 44). The 24 human paints gave 30 signals on the haploid female chromosome set and 34 signals on the haploid male chromosome set. This difference is due to a reciprocal translocation between the Y and an autosome homologous to human chromosome 5. This Y/autosome reciprocal translocation which is unique among catarrhine primates has produced a X1X2Y1Y2/X1X1X2X2 sex-chromosome system. Although most human syntenic groups have been maintained in the silvered leaf monkey chromosomes homologous to human chromosomes 14 and 15, 21 and 22 have experienced Robertsonian fusions. Further, the multiple FISH signals provided by libraries to human chromosomes 1/9, 6/16 indicate that these chromosomes have been split be reciprocal translocations. G-binding analysis shows three different forms of chromosome 1 (X2) which differ by a complex series of inversions in the 10 individuals karyotype. Comparisons with the hybridization patterns in hylobatids (gibbons and siamang) demonstrate that resemblances in chromosomal morphology and banding previously taken to indicate a special phylogenetic relationship between gibbons and colobines are due to convergence.

Animals↗

PubMed2006

Diversity and duplication of DQB and DRB-like genes of the MHC in baleen whales (suborder: Mysticeti).

The molecular diversity and phylogenetic relationships of two class II genes of the baleen whale major histocompatibility complex were investigated and compared to toothed whales and out-groups. Amplification of the DQB exon 2 provided sequences showing high within-species and between-species nucleotide diversity and uninterrupted reading frames consistent with functional class II loci found in related mammals (e.g., ruminants). Cloning of amplified products indicated gene duplication in the humpback whale and triplication in the southern right whale, with average nucleotide diversity of 5.9 and 6.3%, respectively, for alleles of each species. Significantly higher nonsynonymous divergence at sites coding for peptide binding (32% for humpback and 40% for southern right) suggested that these loci were subject to positive (overdominant) selection. A population survey of humpback whales detected 23 alleles, differing by up to 21% of their inferred amino acid sequences. Amplification of the DRB exon 2 resulted in two groups of sequences. One was most similar to the DRB3 of the cow and present in all whales screened to date, including toothed whales. The second was most similar to the DRB2 of the cow and was found only in the bowhead and right whales. Both loci showed low diversity among species and apparent loss of function or altered function including interruption of reading frames. Finally, comparison of inferred protein sequence of the DRB3-like locus suggested convergence with the DQB, perhaps resulting from intergenic conversion or recombination.

Amino Acid Sequence↗

PubMed2005

Immortalization of human extravillous cytotrophoblasts by human papilloma virus gene E6E7: sequential cytogenetic and molecular genetic characterization.

Extravillous cytotrophoblast (EVCT) cultures from the normal placentas of three pregnant women were transfected by HPVE6E7. Sequential cytogenetic and molecular analyses were performed to delineate genetic events that may be critical for cell immortalization. One line, PE1-E6E7, was immortalized successfully, whereas 2 other lines, PE3-E6E7 and PE4-E6E7, could not be maintained beyond crisis. Before crisis, the majority of cells in all lines were karyotypically normal. During the early stages of crisis, there was progressive telomere shortening. Most cells were karyotypically abnormal, with extreme cytogenetic divergence and a predominance of telomeric association and dicentric chromosomes affecting many chromosomes. At the later stages of crisis, the karyotype became more convergent with a drastic decrease in nonclonal aberrations. In PE1-E6E7, after crisis the karyotype was complex, with frequent centromeric rearrangements in the form of isochromosomes and whole-arm translocations. There were unbalanced structural aberrations and numerical changes, including loss of chromosome 13, that could be traced throughout the evolution of the line. These findings support the concept that immortalization is a relatively rare and nonrandom event that occurs only in cells that have acquired the necessary or critical genetic alterations. Telomeric dysfunction may be an important mechanism leading to the acquisition of complex karyotypical aberrations.

Cells, Cultured↗

PubMed1996

The molecular biology of apoptosis.

All multicellular organisms have mechanisms for killing their own cells, and use physiological cell death for defence, development, homeostasis, and aging. Apoptosis is a morphologically recognizable form of cell death that is implemented by a mechanism that has been conserved throughout evolution from nematode to man. Thus homologs of the genes that implement cell death in nematodes also do so in mammals, but in mammals the process is considerably more complex, involving multiple isoforms of the components of the cell death machinery. In some circumstances this allows independent regulation of pathways that converge upon a common end point. A molecular understanding of this mechanism may allow design of therapies that either enhance or block cell death at will.

Animals↗

PubMed1985

Neuropsychology qua interface.

This paper focuses on the multidisciplinary nature and requirements of neuropsychology. It illustrates two approaches to this convergence of neuropsychology and its complementary disciplines: the relationship between the dissociated visual-perceptual and spatial disorders consequent upon focal lesions of the right cerebral hemisphere in man and the evidence (neuroanatomical, neurophysiological, and behavioural) of two major cortico-cortical pathways for processing visual information in monkey; and the evolution of information-processing models (derived from cognitive psychology, linguistics, and pathophysiological data) to delineate the functional architecture of reading and speech production. It cites the study of attention and frontal-lobe function as a major target for research; and it invokes the need to encompass the art of medicine in neuropsychological research and practice.

Animals↗

PubMed2001

Numerical study of the coupled time-dependent Gross-Pitaevskii equation: application to Bose-Einstein condensation.

We present a numerical study of the coupled time-dependent Gross-Pitaevskii equation, which describes the Bose-Einstein condensate of several types of trapped bosons at ultralow temperature with both attractive and repulsive interatomic interactions. The same approach is used to study both stationary and time-evolution problems. We consider up to four types of atoms in the study of stationary problems. We consider the time-evolution problems where the frequencies of the traps or the atomic scattering lengths are suddenly changed in a stable preformed condensate. We also study the effect of periodically varying these frequencies or scattering lengths on a preformed condensate. These changes introduce oscillations in the condensate, which are studied in detail. Good convergence is obtained in all cases studied.

Journal Article↗

PubMed2003

Climatic variability and the evolution of insect freeze tolerance.

Insects may survive subzero temperatures by two general strategies: Freeze-tolerant insects withstand the formation of internal ice, while freeze-avoiding insects die upon freezing. While it is widely recognized that these represent alternative strategies to survive low temperatures, and mechanistic understanding of the physical and molecular process of cold tolerance are becoming well elucidated, the reasons why one strategy or the other is adopted remain unclear. Freeze avoidance is clearly basal within the arthropod lineages, and it seems that freeze tolerance has evolved convergently at least six times among the insects (in the Blattaria, Orthoptera, Coleoptera, Hymenoptera, Diptera and Lepidoptera). Of the pterygote insect species whose cold-tolerance strategy has been reported in the literature, 29% (69 of 241 species studied) of those in the Northern Hemisphere, whereas 85 % (11 of 13 species) in the Southern Hemisphere exhibit freeze tolerance. A randomization test indicates that this predominance of freeze tolerance in the Southern Hemisphere is too great to be due to chance, and there is no evidence of a recent publication bias in favour of new reports of freeze-tolerant species. We conclude from this that the specific nature of cold insect habitats in the Southern Hemisphere, which are characterized by oceanic influence and climate variability must lead to strong selection in favour of freeze tolerance in this hemisphere. We envisage two main scenarios where it would prove advantageous for insects to be freeze tolerant. In the first, characteristic of cold continental habitats of the Northern Hemisphere, freeze tolerance allows insects to survive very low temperatures for long periods of time, and to avoid desiccation. These responses tend to be strongly seasonal, and insects in these habitats are only freeze tolerant for the overwintering period. By contrast, in mild and unpredictable environments, characteristic of habitats influenced by the Southern Ocean, freeze tolerance allows insects which habitually have ice nucleators in their guts to survive summer cold snaps, and to take advantage of mild winter periods without the need for extensive seasonal cold hardening. Thus, we conclude that the climates of the two hemispheres have led to the parallel evolution of freeze tolerance for very different reasons, and that this hemispheric difference is symptomatic of many wide-scale disparities in Northern and Southern ecological processes.

Acclimatization↗

PubMed1996

Network analysis of human Y microsatellite haplotypes.

To investigate the utility of Y chromosome microsatellites for studying human male-lineage evolution, we typed samples from three populations for five tetranucleotide repeats and an Alu insertion polymorphism. We found very high levels of haplotype diversity and evidence that most mutations involve the gain or loss of only one repeat unit, implying that any given microsatellite haplotype may have arisen independently on two or more Y-chromosome lineages. Together, these factors suggest that interpretation of small sample sizes (< 30) will be problematic. By typing a large sample of individuals (n = 174) from one population, East Anglia, we were able to construct a haplotype network. The network exhibits a well-connected core structure of commoner haplotypes. Computer simulations based on this network estimate the convergence time for African and Caucasian groups may be between 1.4 and 1.8 times as long as the convergence of the East Anglian population. Based on our comparison between large and small sample sizes, we suggest that large sample sizes are necessary in order to interpret Y-microsatellite haplotypes, and that a network analysis of the type we describe may prove informative in future studies.

Base Sequence↗

PubMed1992

Tandemly duplicated alpha globin genes of gibbon.

The alpha globin gene locus of the common gibbon (Hylobates lar) was isolated, and it contains two closely linked alpha globin genes that share the same arrangement as that found for the homologous genes of other catarrhine primates. The nucleotide sequences of the gibbon alpha globin genes were determined and compared with the alpha globin gene sequences from other primate species (human, chimpanzee, orangutan, baboon, and rhesus); the prosimian primate, galago, alpha A and alpha B globin genes provided the out-group for this analysis. The degree of divergence for both synonymous and nonsynonymous substitutions among the alpha globin genes are generally smaller for intraspecies than interspecies comparisons, which is indicative of concerted evolution between the paired alpha globin genes of each catarrhine species. The pattern of differences is suggestive of gene conversions. This possibility is supported by both site-by-site and branch-swapping parsimony analyses. The site-by-site parsimony analysis was also used to determine the 3' boundary of each catarrhine species-specific conversion. These alpha globin gene conversion events encompass most of the transcriptional region, including the promoter, exons, introns, and about one-half of the 3'-untranslated region. However, the paired gibbon alpha globin genes show the highest degree of divergence, differing by five nucleotides in their coding regions, three of which encode amino acid replacement substitutions. It appears that the last convergence event between the paired gibbon alpha globin genes is relatively ancient, having occurred approximately 11 million years ago. The remaining 3'-untranslated region and flanking DNAs show no evidence of involvement in any recent conversion event as the parsimony analysis of these sequences group all the alpha 1 globin genes of the different catarrhine species into one clade and all the alpha 2 globin gene of these species into a separate clade. The sequence comparison among the alpha globin genes of different primate species also provides interesting implications regarding the evolution and functional domains of the 3'-untranslated regions.

Amino Acid Sequence↗

PubMed2003

The evolution of environmental and genetic sex determination in fluctuating environments.

Twenty years ago, Bulmer and Bull suggested that disruptive selection, produced by environmental fluctuations, can result in an evolutionary transition from environmental sex determination (ESD) to genetic sex determination (GSD). We investigated the feasibility of such a process, using mutation-limited adaptive dynamics and individual-based computer simulations. Our model describes the evolution of a reaction norm for sex determination in a metapopulation setting with partial migration and variation in an environmental variable both within and between local patches. The reaction norm represents the probability of becoming a female as a function of environmental state and was modeled as a sigmoid function with two parameters, one giving the location (i.e., the value of the environmental variable for which an individual has equal chance of becoming either sex) and the other giving the slope of the reaction norm for that environment. The slope can be interpreted as being set by the level of developmental noise in morph determination, with less noise giving a steeper slope and a more switchlike reaction norm. We found convergence stable reaction norms with intermediate to large amounts of developmental noise for conditions characterized by low migration rates, small differential competitive advantages between the sexes over environments, and little variation between individual environments within patches compared to variation between patches. We also considered reaction norms with the slope parameter constrained to a high value, corresponding to little developmental noise. For these we found evolutionary branching in the location parameter and a transition from ESD toward GSD, analogous to the original analysis by Bulmer and Bull. Further evolutionary change, including dominance evolution, produced a polymorphism acting as a GSD system with heterogamety. Our results point to the role of developmental noise in the evolution of sex determination.

Adaptation, Biological↗

PubMed2003

[The anatomy of episodic memory: evolution of concepts].

Historically, the hippocampus belongs to the limbic lobe described by Broca or to the Papez circuit. His role was first restricted to emotions. The observations that medial temporal lobe (MTL) damage led also to mnemonic dysfunction have been advanced greatly by the study of brain-damaged patients and experimental animals studies. Functional imaging, either positron emission tomography or functional MRI, has helped to change this historical concepts. Recent findings have converged on the observation that hippocampal or parahippocampal regions could be consistently activated in verbal or visuospatial memory paradigms. Furthermore, these functional neuroimaging studies have also stressed the importance of the prefrontal cortical activations in such memory processes. These results show that memory is subserved by a more widely distributed cortical network than expected.

Brain↗

PubMed1992

[Sclerosing cholangitis in the evolution of a surgical hepatic hydatid cyst].

The retrospective analysis of 3 clinical observations points out the etiopathogenetic, clinical and therapeutical aspects of the diffuse stenotic cholangitis, which can occur after the surgical treatment of the hepatic hydatid cyst. Although rare (2.9% of hydatid cysts, 13% of those which communicate with the bile ducts), the diffuse stenotic posthydatid cholangitis represents a severe postoperative complication in cases of median cysts, exerting a compression upon the convergence of hepatic ducts and communicating with the biliary tract. Its presence should be clinically suspected if a mechanical icterus with septic angiocholitis, sometimes associated with an external biliary fistula (from the residual cavity), occurs in the postoperative course of these patients, especially if the primary operation has excluded the remanance of an obstacle at the level of the main bile duct. The lesional substrate is comparable with that of the primitive sclerosing cholangitis, from which it differs through its clear relation with the primary treatment of the hepatic hydatid cyst, through the rapid course of stenotic lesions which, although diffuse, may become more marked in certain segments, as well as through the constant suprastenotic dilatation of the bile ducts. In the pathogenesis are involved the caustic action of some scolicide solutions (2 per cent formaldehyde solution, hypertonic salt solution) on the wall of the bile duct and the cystobiliary communication which predisposes to the peroperative occurrence o-a migration syndrome and of angiocholitis. It requires an early surgical reintervention in order to solve the cholestasis and angiocholitis: according to the morphological situation, we have the choice between disobstruction and trans-stenotic calibration drainage, on the one hand, and biliodigestive derivations in the hilum, which are more efficient, on the other. The prognosis is burdened with the vital risk of septic angiocholitis and with the early occurrence of a secondary biliary cirrhosis or of stenotic recurrences. Prophylaxis consists in the performance of a primary surgical treatment, adequate in median and communicating hydatid cysts, avoiding the "blind" intracystic administration of scolicide solutions, which exert a caustic action on the bile ducts.

Adult↗

PubMed1999

Visuomotor processing as reflected in the directional discharge of premotor and primary motor cortex neurons.

Premotor and primary motor cortical neuronal firing was studied in two monkeys during an instructed delay, pursuit tracking task. The task included a premovement "cue period," during which the target was presented at the periphery of the workspace and moved to the center of the workspace along one of eight directions at one of four constant speeds. The "track period" consisted of a visually guided, error-constrained arm movement during which the animal tracked the target as it moved from the central start box along a line to the opposite periphery of the workspace. Behaviorally, the animals tracked the required directions and speeds with highly constrained trajectories. The eye movements consisted of saccades to the target at the onset of the cue period, followed by smooth pursuit intermingled with saccades throughout the cue and track periods. Initially, an analysis of variance (ANOVA) was used to test for direction and period effects in the firing. Subsequently, a linear regression analysis was used to fit the average firing from the cue and track periods to a cosine model. Directional tuning as determined by a significant fit to the cosine model was a prominent feature of the discharge during both the cue and track periods. However, the directional tuning of the firing of a single cell was not always constant across the cue and track periods. Approximately one-half of the neurons had differences in their preferred directions (PDs) of >45 degrees between cue and track periods. The PD in the cue or track period was not dependent on the target speed. A second linear regression analysis based on calculation of the preferred direction in 20-ms bins (i.e., the PD trajectory) was used to examine on a finer time scale the temporal evolution of this change in directional tuning. The PD trajectories in the cue period were not straight but instead rotated over the workspace to align with the track period PD. Both clockwise and counterclockwise rotations occurred. The PD trajectories were relatively straight during most of the track period. The rotation and eventual convergence of the PD trajectories in the cue period to the preferred direction of the track period may reflect the transformation of visual information into motor commands. The widely dispersed PD trajectories in the cue period would allow targets to be detected over a wide spatial aperture. The convergence of the PD trajectories occurring at the cue-track transition may serve as a "Go" signal to move that was not explicitly supplied by the paradigm. Furthermore, the rotation and convergence of the PD trajectories may provide a mechanism for nonstandard mapping. Standard mapping refers to a sensorimotor transformation in which the stimulus is the object of the reach. Nonstandard mapping is the mapping of an arbitrary stimulus into an arbitrary movement. The shifts in the PD may allow relevant visual information from any direction to be transformed into an appropriate movement direction, providing a neural substrate for nonstandard stimulus-response mappings.

Animals↗

PubMed2003

Morphological convergence in Hippidion and Equus (Amerhippus) South American equids elucidated by ancient DNA analysis.

Unusual equids named hippidions inhabited South America for more than 2 MY (million years). Like many other animals they succumbed to the worldwide climatic change that occurred 10 KY (thousand years) ago and completely disappeared during the great late Pleistocene megafaunal extinction. According to fossil records and numerous dental, cranial, and postcranial characters, Hippidion and Equus lineages are known to have diverged prior to 10 MY. Some equid bones from Rio Verde and Ultima Esperanza (Patagonia, Chile) dating back to the late Pleistocene period (8-13 KY) have been identified as Hippidion saldiasi, while a few teeth have been assigned to Equus. Six samples of those remains have been obtained from the Zoological Museum of Amsterdam for ancient DNA analysis to try to place Hippidion in the evolutive tree of Perissodactyla. Two samples of Hippidion and one sample of Equus yielded 241-394 bp of the mtDNA control region and 172-296 bp of the cytochrome b gene. Unexpectedly, all the sequences clustered deep inside the Equus genus, casting doubt on the initial identification of the bones. For paleontologists, one of the striking and classical diagnostic characters of Hippidion is their extremely short and massive metapodials, a probable locomotory adaptation to the Andine steep slopes. However, our DNA analysis reveals that a very Hippidion-like metapod might also have been possessed by another South American equid, i.e., Equus (Amerhippus), an interpretation supported by complementary anatomical observations. This adaptive convergence between members of the two South American equid genera may lead paleontologists to limb bone misidentification.

Animals↗

PubMed1978

An ethmoid exposure (os planum) in the orbit of Indri indri (Primates, Lemuriformes).

In 6 of 17 skulls of Indri indri retaining distinct sutures in the medial orbital wall, a small separate bony element intervenes between the frontal and the maxillolacrimal suture. This element is demonstrably continuous with the ethmoid on one such skull. The occurrence of an ethmoid exposure in the orbit of Indri suggests that this trait is not a simple function of orbital size and convergence. Since such an exposure is found in non-cheirogaleine lemuriforms, its distribution provides no support for the hyothesis that lorises and galagos are derived from cheirogaleines.

Animals↗