Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Ancestor

  • common ancestor
  • last common ancestor
  • recent common ancestor
  • wild ancestor

  • Terms modified by Ancestor

  • ancestor gene

  • Selected Abstracts


    EVOLUTION, Issue 1 2002
    Cortland K. Griswold
    Abstract We analyzed sequences from a 275-bp hypervariable region in the 5, end of the mitochondrial DNA control region in 190 common chaffinches (Fringilla coelebs) from 19 populations in Europe and North Africa, including new samples from Greece and Morocco. Coalescent techniques were applied to estimate the time to the most recent common ancestor (TMRCA) and divergence times of these populations. The first objective of this study was to infer the locations of refugia where chaffinches survived the last glacial episode, and this was achieved by estimating the TMRCA of populations in regions surrounding the Mediterranean that were unglaciated in the late Pleistocene. Although extant populations in Iberia, Corsica, Greece, and North Africa harbor haplotypes that are basal in a phylogenetic tree, this information alone cannot be used to infer that these localities served as refugia, because it is impossible to infer the ages of populations and their divergence times without also considering the population genetic processes of mutation, migration, and drift. Provided we assume the TMRCAs of populations are a reasonable estimate of a population's age, coalescent-based methods place resident populations in Iberia, Corsica, Greece, and North Africa during the time of the last glacial maximum, suggesting these regions served as refugia for the common chaffinch. The second objective was to determine when populations began diverging from each other and to use this as a baseline to estimate current levels of gene flow. Divergence time estimates suggest that European populations began diverging about 60,000 years before present. The relatively recent divergence of populations in North Africa, Italy, and Iberia may explain why classic migration estimates based on equilibrium assumptions are high for these populations. We compare these estimates with nonequilibrium-based estimates and show that the nonequilibrium estimates are consistently lower than the equilibrium estimates. [source]


    EVOLUTION, Issue 2 2009
    Nicola J. Barson
    The development of isolation by distance (IBD) and isolation by time (IBT) was contrasted among demes of European grayling (Thymallus thymallus) that have diverged within the last 25 generations following colonization of a lake (Lesjaskogsvatnet). We find low but significant levels of genetic differentiation among spawning tributaries and a pattern of IBD among them. We do not, however, find evidence for IBT despite an up to four-week difference in spawning date between "warm/early" and "cold/late" spawning demes and differences in the incubation temperatures experienced by offspring. It appears that IBD has developed more rapidly than IBT in this system and that adaptive divergence has been initiated in the absence of IBT. Although analysis of selected loci could reveal reduced recombination in parts of the genome associated with temporal divergence, our analysis of neutral genetic data suggests that IBD is a more important isolating mechanism in the early stages of adaptive divergence in European grayling. [source]

    Writing the History of Humanity: The Role of Museums in Defining Origins and Ancestors in a Transnational World

    Monique Scott
    ABSTRACT This article explores the question of how transnational audiences experience anthropology exhibitions in particular, and the natural history museum overall. Of interest are the ways in which natural history museums reconcile anthropological notions of humanity's shared evolutionary history,in particular, African origins accounts,with visitors' complex cultural identities. Through case studies of British, American, and Kenyan museum audiences, this research probed the cultural preconceptions that museum visitors bring to the museum and use to interpret their evolutionary heritage. The research took special notice of audiences of African descent, and their experiences in origins exhibitions and the natural history museums that house them. The article aims to draw connections between natural history museums and the dynamic ways in which museum visitors make meaning. As museums play an increasing role in the transnational homogenization of cultures, human origins exhibitions are increasingly challenged to communicate an evolutionary prehistory that we collectively share, while validating the cultural histories that make us unique. [source]

    Evolution and human tissue expression of the Cres/Testatin subgroup genes, a reproductive tissue specific subgroup of the type 2 cystatins

    Jessica Frygelius
    SUMMARY The cystatin family comprises a group of generally broadly expressed protease inhibitors. The Cres/Testatin subgroup (CTES) genes within the type 2 cystatins differs from the classical type 2 cystatins in having a strikingly reproductive tissue-specific expression, and putative functions in reproduction have therefore been discussed. We have performed evolutionary studies of the CTES genes based on gene searches in genomes from 11 species. Ancestors of the cystatin family can be traced back to plants. We have localized the evolutionary origin of the CTES genes to the split of marsupial and placental mammals. A model for the evolution of these genes illustrates that they constitute a dynamic group of genes, which has undergone several gene expansions and we find indications of a high degree of positive selection, in striking contrast to what is seen for the classical cystatin C. We show with phylogenetic relations that the CTES genes are clustered into three original groups, a testatin, a Cres, and a CstL1 group. We have further characterized the expression patterns of all human members of the subfamily. Of a total of nine identified human genes, four express putative functional transcripts with a predominant expression in the male reproductive system. Our results are compatible with a function of this gene family in reproduction. [source]

    Ancestors and variants: tales from the cryptic

    William E. Browne
    SUMMARY Those who work at the interface of development and evolution are united by the conviction that developmental comparisons can shed light on both the evolution of specific morphologies and the macroevolutionary process itself. In practice, however, the field comprises a diversity of approaches. As the field grows and practitioners attempt to digest a growing mountain of comparative data, the various approaches of "Evo Devo" have themselves evolved. A meeting organized by the authors and held at the University of Chicago in the Spring of 1999 illustrated some of these changes. This review will draw on its content to discuss recent developments in two areas: the reconstruction of common ancestors and the developmental basis of evolutionary change. [source]

    A New AcanthocyclopsKiefer, 1927 (Copepoda: Cyclopoida) from Central Mexico with Comments on the Distributionof the Genus in Middle America

    Nancy Mercado
    Abstract A new species of AcanthocyclopsKiefer is described from central Mexico. It differs from its congeners by a combination of characters including mainly: 11,13 antennular segments, a spine formula of 3444 and modified setae on legs 2,4. The presence of a compound distal antennular segment is aberrant within the Cyclopoida. The new species seems to be related to Nearctic forms of the vernalis ,robustus clade. Ancestors of this lineage probably reached central Mexico as a result of glaciation events and the new species is a remain of stranded postglacial populations; some of these forms were succesful in colonizing tropical lands. A key for the identification of the species of Acanthocyclops recorded in Mexico is included. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Intolerable human suffering and the role of the ancestor: literary criticism as a means of analysis

    Elizabeth Harrison RN PhD
    Intolerable human suffering and the role of the ancestor: literary criticism as a means of analysis This essay explores the experience of intolerable human suffering in Toni Cade Bambara's novel, The Salt Eaters. The method of analysis is literary criticism, a technique that shares many of the same goals as other types of inquiry. It employs close reading to illuminate the novel's meaning(s), thereby revealing information about the nature of intolerable human suffering. Morrison's characteristics of black art is the literary and cultural framework that guides the analysis of Bambara's novel. The paradigm has broad application for nursing. The purpose of this analysis was to describe the role of the ancestral system as a predictor of the trajectory of suffering. The results extend Morrison's paradigm and her notion of ancestor to include traditions and other non-corporeal factors that are essential for well-being and survival. The protagonist in Bambara's novel, Velma Henry, is the patient and exemplar who does not succumb to intolerable suffering because of its cumulative weight, but because she has lost touch with the traditions of her people, an essential component of her ancestral system. The ancestral system is a rich and complex network of individuals, groups, customs and beliefs that are instructive, protective and benevolent. Ancestors are also timeless and provide wisdom, but when the ancestral system is weak or absent, the trajectory of suffering is not favourable. Nurses must learn to recognize intolerable human suffering, to identify the patient's ancestral system, and to work within that system to keep suffering patients from harm. [source]

    Speaking with the Ancestors: Mississippian Stone Statuary of the Tennessee-Cumberland Region by Kevin Smith and James Miller

    Timothy R. Pauketat
    No abstract is available for this article. [source]

    Vaka Moana: Voyages of the Ancestors edited by K. R. Howe

    No abstract is available for this article. [source]

    The Curatorial Voice: U.S. Institutions Exhibit the Ancient Andes

    Two new exhibits on ancient Andean civilizations are open in the United States. Machu Picchu: Unveiling the Mystery of the Incas is a large traveling exhibition and Tiwanaku: Ancestors of the Inca is a smaller temporary exhibition that is not traveling. Both introduce North American audiences to objects and information that have never been exhibited in the United States and each includes some extraordinary artifacts. The two exhibits differ in many ways: Machu Picchu emphasizes information, archaeological science, and cultural history, whereas Tiwanaku focuses on art style and objects. The curatorial voice and point of view are strong in each exhibit, as is the institutional perspective of its originiating museum. In this respect these exhibits differ significantly from contemporary ones on ancient North America, which generally include the voices and points of view of descendant communities and others. [source]

    Mortgaging the Ancestors: Ideologies of Attachment in Africa by Parker Shipton

    No abstract is available for this article. [source]

    Book review: The Link: Uncovering our Earliest Ancestors

    Alfred L. Rosenberger
    No abstract is available for this article. [source]

    Ancestors, magic, and exchange in Yolngu doctrines: extensions of the person in time and space

    Ian Keen
    The article draws on the association drawn by Munn between Aboriginal ancestral transformations and the moral order, and the theory of partible persons, in order to re-examine Yolngu doctrines and related practices to do with totemic ancestors and their traces, magic and sorcery, and exchange. It argues that all three broad domains draw on beliefs about intrinsic relations between part and whole, image and object, and the intrinsic powers of bodily substance and spirits of the dead. These domains imply the extension of persons in time and space, and each relates to a rather distinct aspect of the moral-political order. The article shows that the strong dichotomy drawn by Durkheim and his followers between ,religion' and ,magic' obscures the connections between these domains, and neglects the instrumental aspect of Yolngu ancestral doctrines and practices. [source]


    ART HISTORY, Issue 3 2007
    Drawing on Mieke Bal's construction of a critical history of art, which facilitates the extension of Walter Benjamin's philosophy to the visual arts, this essay reconsiders Michelangelo's Sistine Chapel in Rome, attentive to the conditions that allows the work of art from the past to appear in the present. Two forms of anachronism are proposed: the first may be understood as constituting the temporal structure of the Sistine Chapel up to its completion in 1542; the second, by contrast, is concerned with our ,present' and is a more audacious form of anachronism defined by the relationship between Samuel Beckett's Waiting for Godot and the Chapel, particularly the ,Ancestors of Christ'. In elucidating these connections, Careri proposes ,constellation' rather than influence to signify deep and problematic relations. [source]

    Biological and Molecular Geochemical Evidence for Dinoflagellate Ancestors in the Upper Sinian-Cambrian

    ZHANG Shuichang
    Abstract Dinoflagellates are single celled organisms that reflect the ecological conditions in modern oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic (c. 240 Ma ago). However, the presence of molecular biomarkers (dinosterane, 4,-methyl-24-ethylcholestane and triaromatic dinosteroids) in rock extracts and coccoid dinoflagellate fossils from the upper Sinian to Cambrian of the Tarim basin confirms the hypothesis that dinoflagellates have an ancient origin, and predate the oldest undisputed dinoflagellate fossils at least by 300 Ma, as early as the late Sinian-Cambrian. [source]

    One of the duplicated matrix metalloproteinase-9 genes is expressed in regressing tail during anuran metamorphosis

    Kenta Fujimoto
    The drastic morphological changes of the tadpole are induced during the climax of anuran metamorphosis, when the concentration of endogenous thyroid hormone is maximal. The tadpole tail, which is twice as long as the body, shortens rapidly and disappears completely in several days. We isolated a cDNA clone, designated as Xl MMP-9TH, similar to the previously reported Xenopus laevis MMP-9 gene, and showed that their Xenopus tropicalis counterparts are located tandemly about 9 kb apart from each other in the genome. The Xenopus MMP-9TH gene was expressed in the regressing tail and gills and the remodeling intestine and central nervous system, and induced in thyroid hormone-treated tail-derived myoblastic cultured cells, while MMP-9 mRNA was detected in embryos. Three thyroid hormone response elements in the distal promoter and the first intron were involved in the upregulation of the Xl MMP-9TH gene by thyroid hormone in transient expression assays, and their relative positions are conserved between X. laevis and X. tropicalis promoters. These data strongly suggest that the MMP-9 gene was duplicated, and differentiated into two genes, one of which was specialized in a common ancestor of X. laevis and X. tropicalis to be expressed in degenerating and remodeling organs as a response to thyroid hormone during metamorphosis. [source]

    Primary mesenchyme cell-ring pattern formation in 2D-embryos of the sea urchin

    Hideki Katow
    Primary mesenchyme cell (PMC) migration during PMC-ring pattern formation was analyzed using computer-assisted time-lapse video microscopy in spread embryos (2D-embryo) of the sea urchin, Mespilia globulus, and a computer simulation. The PMC formed a near normal ring pattern in the 2D-embryos, which were shown to be an excellent model for the examination of cell behavior in vivo by time-lapse computer analysis. The average migration distance of the ventro-lateral PMC aggregate-forming cells (AFC) and that of the dorso-ventral PMC cable-forming cells (CFC) showed no significant difference. All PMC took a rather straightforward migration path to their destinations with little lag time after ingression. This in vivo cell behavior fitted well to a computer simulation with a non-diffusable chemotaxis factor in the cyber-cell migration field. This simulation suggests that PMC recognize their destination from a very early moment of cell migration from the vegetal plate, and implicates that a chemoattractive region is necessary for making the PMC migration pattern. The left- and right-lateral AFC and dorso and ventral CFC were each derived from an unequally divided one-quarter segment of the vegetal plate. This suggests that AFC and CFC have a distinctive ancestor in the vegetal plate, and the PMC are a heterogeneous population at least in terms of their destination in the PMC-ring pattern. [source]

    Comparative expression analysis of transcription factor genes in the endostyle of invertebrate chordates

    Jin Hiruta
    Abstract The endostyle of invertebrate chordates is a pharyngeal organ that is thought to be homologous with the follicular thyroid of vertebrates. Although thyroid-like features such as iodine-concentrating and peroxidase activities are located in the dorsolateral part of both ascidian and amphioxus endostyles, the structural organization and numbers of functional units are different. To estimate phylogenetic relationships of each functional zone with special reference to the evolution of the thyroid, we have investigated, in ascidian and amphioxus, the expression patterns of thyroid-related transcription factors such as TTF-2/FoxE4 and Pax2/5/8, as well as the forkhead transcription factors FoxQ1 and FoxA. Comparative gene expression analyses depicted an overall similarity between ascidians and amphioxus endostyles, while differences in expression patterns of these genes might be specifically related to the addition or elimination of a pair of glandular zones. Expressions of Ci-FoxE and BbFoxE4 suggest that the ancestral FoxE class might have been recruited for the formation of thyroid-like region in a possible common ancestor of chordates. Furthermore, coexpression of FoxE4, Pax2/5/8, and TPO in the dorsolateral part of both ascidian and amphioxus endostyles suggests that genetic basis of the thyroid function was already in place before the vertebrate lineage. Developmental Dynamics 233:1031,1037, 2005. © 2005 Wiley-Liss, Inc. [source]

    An amphioxus winged helix/forkhead gene, AmphiFoxD: Insights into vertebrate neural crest evolution

    Jr-Kai Yu
    Abstract During amphioxus development, the neural plate is bordered by cells expressing many genes with homologs involved in vertebrate neural crest induction. However, these amphioxus cells evidently lack additional genetic programs for the cell delaminations, migrations, and differentiations characterizing definitive vertebrate neural crest. We characterize an amphioxus winged helix/forkhead gene (AmphiFoxD) closely related to vertebrate FoxD genes. Phylogenetic analysis indicates that the AmphiFoxD is basal to vertebrate FoxD1, FoxD2, FoxD3, FoxD4, and FoxD5. One of these vertebrate genes (FoxD3) consistently marks neural crest during development. Early in amphioxus development, AmphiFoxD is expressed medially in the anterior neural plate as well as in axial (notochordal) and paraxial mesoderm; later, the gene is expressed in the somites, notochord, cerebral vesicle (diencephalon), and hindgut endoderm. However, there is never any expression in cells bordering the neural plate. We speculate that an AmphiFoxD homolog in the common ancestor of amphioxus and vertebrates was involved in histogenic processes in the mesoderm (evagination and delamination of the somites and notochord); then, in the early vertebrates, descendant paralogs of this gene began functioning in the presumptive neural crest bordering the neural plate to help make possible the delaminations and cell migrations that characterize definitive vertebrate neural crest. © 2002 Wiley-Liss, Inc. [source]

    Retinoids and nonvertebrate chordate development

    Shigeki Fujiwara
    Abstract Retinoic acid (RA) is required for the differentiation and morphogenesis of chordate-specific features, such as the antero-posterior regionalization of the dorsal hollow nerve cord and neural crest cells. RA receptors (RARs) have been reported exclusively in chordates, suggesting that the acquisition of the RAR gene was important for chordate evolution. A scenario is presented here for the establishment of an RAR-mediated developmental regulatory system during the course of chordate evolution. In the common chordate ancestor, RAR came to control the spatial expression pattern of Hox genes in the ectoderm and endoderm along the antero-posterior axis. In these germ layers, RA was required for the differentiation of epidermal sensory neurons and the morphogenesis of pharyngeal gill slits, respectively. As the diffuse epidermal nerve net in the chordate ancestor became centralized to form the dorsal nerve cord, the epidermal Hox expression pattern was carried into the central nervous system. Because the Hox code here came to specify neuronal identity along the antero-posterior axis, RA became inextricably linked to the antero-posterior patterning of the chordate central nervous system. © 2006 Wiley Periodicals, Inc. J Neurobiol 66: 645,652, 2006 [source]

    The evolution of the protonephridial terminal organ across Rotifera with particular emphasis on Dicranophorus forcipatus, Encentrum mucronatum and Erignatha clastopis (Rotifera: Dicranophoridae)

    ACTA ZOOLOGICA, Issue 2 2010
    Ole Riemann
    Abstract Riemann, O. and Ahlrichs, W.H. 2009. The evolution of the protonephridial terminal organ across Rotifera with particular emphasis on Dicranophorus forcipatus, Encentrum mucronatum and Erignatha clastopis (Rotifera: Dicranophoridae). ,Acta Zoologica (Stockholm) 91: 199,211 We report on the ultrastructure of the protonephridial terminal organ in three species of dicranophorid rotifers (Dicranophorus forcipatus, Encentrum mucronatum and Erignatha clastopis). Differences between the three species relate to shape and size, the morphology of the filter region and the number of microvilli and cilia inside the terminal organ. A comparison across Rotifera indicates that the terminal organs in D. forcipatus display a number of plesiomorphic characters, but are modified in E. mucronatum and Er. clastopis. This is in accordance with the results of phylogenetic analyses suggesting a basal position of D. forcipatus compared with the more derived species E. mucronatum and Er. clastopis. Moreover, we survey available data on the terminal organ in Rotifera and discuss its evolutionary transformations. The protonephridial terminal organ in the common ancestor of Rotifera consisted of a cytoplasmic cylinder with cilia united into a vibratile flame and a single circle of circumciliary microvilli. Depending on the topology on which characters are optimized, the site of ultrafiltration was formed by longitudinal cytoplasmic columns spanned by a fine filter diaphragm or by pores in the wall of the terminal organ. In several taxa of Rotifera, the terminal organ , probably independently , lost its circumciliary microvilli. [source]

    Architecture of developing multicellular yeast colony: spatio-temporal expression of Ato1p ammonium exporter

    e Váchová
    Summary Yeasts, when growing on solid surfaces, form organized multicellular structures, colonies, in which cells differentiate and thus possess different functions and undergo dissimilar fate. Understanding the principles involved in the formation of these structures requires new approaches that allow the study of individual cells directly in situ without needing to remove them from the microbial community. Here we introduced a new approach to the analysis of whole yeast microcolonies either containing specific proteins labelled by fluorescent proteins or stained with specific dyes, by two-photon excitation confocal microscopy. It revealed that the colonies are covered with a thin protective skin-like surface cell layer which blocks penetration of harmful compounds. The cells forming the layer are tightly connected via cell walls, the presence of which is essential for keeping of protective layer function. Viewing the colonies from different angles allowed us to reconstruct a three-dimensional profile of the cells producing ammonium exporter Ato1p within developing microcolonies growing either as individuals or within a group of microcolonies. We show that neighbouring microcolonies coordinate production of Ato1p-GFP. Ato1p itself appears synchronously in cells, which do not originate from the same ancestor, but occupy specific position within the colony. [source]

    Lateral transmission of equine arteritis virus among Lipizzaner stallions in South Africa

    Summary Reasons for performing study:A serological study conducted in 1995 revealed that 7 stallions at the Lipizzaner Centre, Gauteng, South Africa, were seropositive for antibody to equine arteritis virus (EAV). A Lipizzaner stallion imported into South Africa from Yugoslavia in 1981 had previously (1988) been confirmed to be an EAV carrier. Despite being placed under life-long breeding quarantine, EAV had been transmitted between stallions at the Lipizzaner Centre. Objectives: To investigate the phylogenetic relationships between the strain of EAV shed in the semen of the original carrier stallion and strains recovered from the semen of 5 other stallions; and to investigate the means whereby lateral transmission of EAV occurred among 7 in-contact, nonbreeding stallions at the Centre. Methods: EAV was isolated from semen collected from the seropositive stallions using RK-13 cells. Viral RNA was reverse transcribed and amplified by polymerase chain reaction using ORF5-specific primers, subjected to sequence and phylogenetic analysis. Results: Phylogenetic analysis of strains of EAV recovered from the semen of 6 persistently infected stal lions confirmed that all viruses were closely related and probably derived from a common ancestor, i.e. the stallion imported from Yugoslavia. Lateral transmission subsequently occurred among 7 in-contact, nonbreeding stallions at the Centre. It is speculated that these stallions may have been exposed to virus from be dding or fo mites contaminated with semen. Conclusions: These data confirm that lateral transmission of EAV can occur from shedding stallions to susceptible, in-contact horses, including other stallions, which may become persistently infected with the virus. Potential relevance: The findings are consistent with lateral spread of a single, unique strain of EAV among a group; and suggest that transmission of EAV may be initiated by infection of one or more stallions with virus on bedding or other fomites contaminated with EAV-infected semen. [source]

    Song Learning in Wild and Domesticated Strains of White-Rumped Munia, Lonchura striata, Compared by Cross-Fostering Procedures: Domestication Increases Song Variability by Decreasing Strain-Specific Bias

    ETHOLOGY, Issue 5 2010
    Miki Takahasi
    Song diversity results from the interactions between natural selection, sexual selection, and individual learning. To understand song diversity, all three factors must be considered collectively, not separately. Bengalese Finches were domesticated about 250 yr ago. Their courtship songs have become different from their ancestor, the White-rumped Munia. Bengalese Finches sing songs with complex note-to-note transition patterns and with acoustically diverse song notes while White-rumped Munias sing songs with fixed note sequence and mostly broad band song notes. Bengalese Finches were selected for domestication based on their good parenting ability, not their songs, but this artificial selection has nonetheless affected their songs. To test whether divergence occurred not only in the song phenotypes but also in the genetic basis for predisposition of strain specific song learning, we conducted a cross-fostering experiment between Bengalese Finches and White-rumped Munias. In both strains, song learning was affected by rearing condition: the acoustical feature and transition patterns followed those of the foster fathers. However, the accuracy of song learning differed between the wild and the domesticated strains: sharing of song note between sons and tutors in Finches was not very accurate regardless of the tutor, while Munias were highly accurate in copying Munia songs but often omitted song elements from Finch fathers. These results suggest that White-rumped Munias are strongly constrained to learn their own strain's song, and that this constraint was relaxed in the Bengalese Finch by domestication. [source]

    Adaptive loss of ultraviolet-sensitive/violet-sensitive (UVS/VS) cone opsin in the blind mole rat (Spalax ehrenbergi)

    Z. K. David-Gray
    Abstract In previous studies, fully functional rod and long-wavelength-sensitive (LWS) cone photopigments have been isolated from the eye of the subterranean blind mole rat (Spalax ehrenbergi superspecies). Spalax possesses subcutaneous atrophied eyes and lacks any ability to respond to visual images. By contrast this animal retains the ability to entrain circadian rhythms of locomotor behaviour to environmental light cues. As this is the only known function of the eye, the rod and LWS photopigments are thought to mediate this response. Most mammals are dichromats possessing, in addition to a single rod photopigment, two classes of cone photopigment, LWS and ultraviolet-sensitive/violet-sensitive (UVS/VS) with differing spectral sensitivities which mediate colour vision. In this paper we explore whether Spalax is a dichromat and has the potential to use colour discrimination for photoentrainment. Using immunocytochemistry and molecular approaches we demonstrate that Spalax is a LWS monochromat. Spalax lacks a functional UVS/VS cone photopigment due to the accumulation of several deleterious mutational changes that have rendered the gene nonfunctional. Using phylogenetic analysis we show that the loss of this class of photoreceptor is likely to have arisen from the visual ecology of this species, and is not an artefact of having an ancestor which lacked a functional UVS/VS cone photopigment. We conclude that colour discrimination is not a prerequisite for photoentrainment in this species. [source]


    EVOLUTION, Issue 9 2009
    Diego Astúa
    The New World family Didelphidae, the basal lineage within marsupials, is commonly viewed as morphologically conservative, yet includes aquatic, terrestrial, scansorial, and arboreal species. Here, I quantitatively estimated the existing variability in size and shape of the Didelphidae scapula (1076 specimens from 56 species) using geometric morphometrics, and compared size and shape differences to evolutionary and ecologic distances. I found considerable variation in the scapula morphology, most of it related to size differences between species. This results in morphologic divergence between different locomotor habits in larger species (resulting from increased mechanical loads), but most smaller species present similarly shaped scapulae. The only exceptions are the water opossum and the short-tailed opossums, and the functional explanations for these differences remain unclear. Scapula size and shape were mapped onto a molecular phylogeny for 32 selected taxa and ancestral size and shapes were reconstructed using squared-changed parsimony. Results indicate that the Didelphidae evolved from a medium- to small-sized ancestor with a generalized scapula, slightly more similar to arboreal ones, but strikingly different from big-bodied present arboreal species, suggesting that the ancestral Didelphidae was a small scansorial animal with no particular adaptations for arboreal or terrestrial habits, and these specializations evolved only in larger-bodied clades. [source]


    EVOLUTION, Issue 1 2008
    Virginie Poullain
    The evolution of exploitative specificity can be influenced by environmental variability in space and time and the intensity of trade-offs. Coevolution, the process of reciprocal adaptation in two or more species, can produce variability in host exploitation and as such potentially drive patterns in host and parasite specificity. We employed the bacterium Pseudomonas fluorescens SBW25 and its DNA phage ,2 to investigate the role of coevolution in the evolution of phage infectivity range and its relation with phage growth rate. At the phage population level, coevolution led to the evolution of broader infectivity range, but without an associated decrease in phage growth rate relative to the ancestor, whereas phage evolution in the absence of bacterial evolution led to an increased growth rate but no increase in infectivity range. In contrast, both selection regimes led to phage adaptation (in terms of growth rates) to their respective bacterial hosts. At the level of individual phage genotypes, coevolution resulted in within-population diversification in generalist and specialist infectivity range types. This pattern was consistent with a multilocus gene-for-gene interaction, further confirmed by an observed cost of broad infectivity range for individual phage. Moreover, coevolution led to the emergence of bacterial genotype by phage genotype interactions in the reduction of bacterial growth rate by phage. Our study demonstrates that the strong reciprocal selective pressures underlying the process of coevolution lead to the emergence and coexistence of different strategies within populations and to specialization between selective environments. [source]


    EVOLUTION, Issue 9 2004
    Sylvain Charlat
    Abstract . -Cytoplasmic incompatibility (CI) is induced in arthropods by the maternally inherited bacterium Wolbachia. When infected males mate with uninfected females or with females bearing a different Wolbachia variant, paternal chromosomes behave abnormally and embryos die. This pattern can be interpreted as resulting from two bacterial effects: One (usually termed mod, for modification) would affect sperm and induce embryo death, unless Wolbachia is also present in the egg, which implies the existence of a second effect, usually termed resc, for rescue. The fact that CI can occur in crosses between males and females infected by different Wolbachia shows that mod and resc interact in a specific manner. In other words, different compatibility types, or mod/resc pairs seem to have diverged from one (or a few) common ancestor(s). We are interested in the process allowing the evolution of mod/resc pairs. Here this question is addressed experimentally after cytoplasmic injection into a single host species (Drosophila simulans) by investigating compatibility relationships between closely related Wolbachia variants naturally evolving in different dipteran hosts: D. simulans, Drosophila melanogaster, and Rhagoletis cerasi. Our results suggest that closely related bacteria can be totally or partially incompatible. The compatibility relationships observed can be explained using a formal description of the mod and resc functions, implying both qualitative and quantitative variations. [source]


    EVOLUTION, Issue 5 2004
    M. Alice Pinto
    Abstract The invasion of Africanized honeybees (Apis mellifera L.) in the Americas provides a window of opportunity to study the dynamics of secondary contact of subspecies of bees that evolved in allopatry in ecologically distinctive habitats of the Old World. We report here the results of an 11-year mitochondrial DNA survey of a feral honeybee population from southern United States (Texas). The mitochondrial haplotype (mitotype) frequencies changed radically during the 11-year study period. Prior to immigration of Africanized honeybees, the resident population was essentially of eastern and western European maternal ancestry. Three years after detection of the first Africanized swarm there was a mitotype turnover in the population from predominantly eastern European to predominantly A. m. scutellata (ancestor of Africanized honeybees). This remarkable change in the mitotype composition coincided with arrival of the parasitic mite Varroa destructor, which was likely responsible for severe losses experienced by colonies of European ancestry. From 1997 onward the population stabilized with most colonies of A. m. scutellata maternal origin. [source]


    EVOLUTION, Issue 7 2003
    Noah A. Rosenberg
    Abstract., The genealogies of samples of orthologous regions from multiple species can be classified by their shapes. Using a neutral coalescent model of two species, I give exact probabilities of each of four possible genealogical shapes: reciprocal monophyly, two types of paraphyly, and polyphyly. After the divergence that forms two species, each of which has population size N, polyphyly is the most likely genealogical shape for the lineages of the two species. At , 1.300N generations after divergence, paraphyly becomes most likely, and reciprocal monophyly becomes most likely at ,1.665N generations. For a given species, the time at which 99% of its loci acquire monophyletic genealogies is ,5.298N generations, assuming all loci in its sister species are monophyletic. The probability that all lineages of two species are reciprocally monophyletic given that a sample from the two species has a reciprocally monophyletic genealogy increases rapidly with sample size, as does the probability that the most recent common ancestor (MRCA) for a sample is also the MRCA for all lineages from the two species. The results have potential applications for the testing of evolutionary hypotheses. [source]