Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “convergent evolution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed2006

Comparative phylogenetic analysis of male alternative reproductive tactics in ray-finned fishes.

Using comparative phylogenetic analysis, we analyzed the evolution of male alternative reproductive tactics (MARTs) in ray-finned fishes (Actinopterygii). Numerous independent origins for each type of MART (involving sneaker males, female mimics, pirates, and satellite males) indicate that these behaviors have been highly labile across actinopterygiian evolution, consistent with a previous notion that convergent selection in fishes can readily mold the underlying suites of reproductive hormones into similar behaviors. The evolutionary appearance of MARTs was significantly correlated with the presence of sexually selected traits in bourgeois males (P = 0.001) but not with the presence of male parental care. This suggests that MARTs often arise from selection on some males to circumvent bourgeois male investment in mate monopolization, rather than to avoid male brood care per se. We found parsimony evidence for an evolutionary progression of MARTs wherein sneaking is usually the evolutionary precursor to the presumably more complex MARTs of female mimicry and cooperative satellite behavior. Nest piracy appears not to be part of this evolutionary progression, possibly because its late onset in the life cycle of most ray-finned fishes reduces the effects of selection on this reproductive tactic.

Animals↗
PubMed2005

Mosaics of convergences and noise in morphological phylogenies: what's in a viverrid-like carnivoran?

Adaptive convergence in morphological characters has not been thoroughly investigated, and the processes by which phylogenetic relationships may be misled by morphological convergence remains unclear. We undertook a case study on the morphological evolution of viverrid-like feliformians (Nandinia, Cryptoprocta, Fossa, Eupleres, Prionodon) and built the largest morphological matrix concerning the suborder Feliformia to date. A total of 349 characters grouped into four anatomical partitions were used for all species of Viverridae and viverrid-like taxa plus representatives of the Felidae, Hyaenidae, Herpestidae, and one Malagasy mongoose. Recent molecular phylogenetic analyses suggest that viverrid-like morphotypes appeared independently at least three times during feliformian evolution. We thus used a synthetic molecular tree to assess morphological evolutionary patterns characterizing the viverrid-like taxa. We examined phylogenetic signal, convergence and noise in morphological characters using (a) tree-length distribution (g1), (b) partitioned Bremer support, (c) RI values and their distribution, (d) respective contributions of diagnostic synapomorphies at the nodes for each partition, (e) patterns of shared convergences among viverrid-like taxa and other feliformian lineages, (f) tree-length differences among alternative hypotheses, and (g) the successive removal of convergent character states from the original matrix. In addition, the lability of complex morphological structures was assessed by mapping them onto the synthetic molecular tree. The unconstrained morphological analysis yielded phylogenetic groupings that closely reflected traditional classification. The use of a synthetic molecular tree (constraint) combined with our thorough morphological investigations revealed the mosaics of convergences likely to have contributed to part of the historical uncertainty over viverrid classification. It also showed that complex morphological structures could be subjected to reversible evolutionary trends. The morphological matrix proved useful in characterizing several feliformian clades with diagnostic synapomorphies. These results support the removal from the traditionally held Viverridae of several viverrid-like taxa into three distinct families: Nandiniidae (Nandinia), Prionodontidae (Prionodon), and the newly defined Eupleridae (including Cryptoprocta, Fossa, Eupleres plus all "mongoose-like" Malagasy taxa). No clearly "phylogenetically misleading" data subsets could be identified, and the great majority of morphological convergences appeared to be nonadaptive. The multiple approaches used in this study revealed that the most disruptive element with regards to morphological phylogenetic reconstruction was noise, which blured the expression of phylogenetic signal. This study demonstrates the crucial need to consider independent (molecular) phylogenies in order to produce reliable evolutionary hypotheses and should promote a new approach to the definition of morphological characters in mammals. [Constrained analysis; convergence; evolutionary scenario; Feliformia; morphology; noise; phylogenetic signal; phylogeny; Viverridae.].

Anatomy, Comparative↗
PubMed1998

Primordial nucleosynthesis.

With the advent of the new extragalactic deuterium observations, Big Bang nucleosynthesis (BBN) is on the verge of undergoing a transformation. In the past, the emphasis has been on demonstrating the concordance of the BBN model with the abundances of the light isotopes extrapolated back to their primordial values by using stellar and galactic evolution theories. As a direct measure of primordial deuterium is converged upon, the nature of the field will shift to using the much more precise primordial D/H to constrain the more flexible stellar and galactic evolution models (although the question of potential systematic error in 4He abundance determinations remains open). The remarkable success of the theory to date in establishing the concordance has led to the very robust conclusion of BBN regarding the baryon density. This robustness remains even through major model variations such as an assumed first-order quark-hadron phase transition. The BBN constraints on the cosmological baryon density are reviewed and demonstrate that the bulk of the baryons are dark and also that the bulk of the matter in the universe is nonbaryonic. Comparison of baryonic density arguments from Lyman-alpha clouds, x-ray gas in clusters, and the microwave anisotropy are made.

Astronomical Phenomena↗
PubMed2026

Lack of Evidence for Gene-Level Convergence Linked to Evolutionary Shifts in Torpor Among Placental Mammals.

Torpor is a key survival strategy that many avian and mammalian lineages evolved in response to challenging environmental conditions. Whether the independent evolution of torpor in different lineages involved changes in the same genes remains poorly understood. Here, we performed comparative screens across 190 placental mammal genomes to comprehensively examine associations between loss, positive selection, and evolutionary rate shifts in individual protein-coding genes and evolutionary shifts in torpor use. We find that gene-torpor associations are highly clade-specific, with no gene being able to explain the majority of torpor shifts across the phylogeny of placental mammals. In contrast, there is more evidence, albeit still limited, for evolutionary convergence at the pathway level. Our results suggest that torpor emerged through several genetic routes in placental mammals, which likely explains the vast diversity of torpor use patterns that can be observed among torpor-capable species today.

Animals↗
PubMed2000

Evolution of cortical lamination: the reelin/Dab1 pathway.

The mammalian cortical plate is characterized by its radial organization and its inside-outside developmental gradient. Observations on reelin and Dab1-deficient mice show that reelin and Dab1 are both required to develop radial cortical organization and a normal maturation gradient. In the reptilian cortex, radial organization varies among species; it is the most rudimentary in turtles and the most elaborate in lizards, and can be described as intermediate in other species such as crocodilians and Sphenodon. On the other hand, the gradient of corticogenesis is directed from outside to inside in all reptiles studied, as well as in mice that are deficient in reelin, Dab1, as well as cyclin-dependent kinase 5 (Cdk5) and p35. All reptiles, even turtles, have reelin-expressing cells in the embryonic marginal zone. Mammals are characterized by a drastic increase in the number of reelin-positive cells (Cajal-Retzius cells) as well as by an amplification of reelin expression per cell. In lizards, the pattern of reelin expression is different, as reelin-expressing cells are also present below the cortical plate. In all mammalian and reptilian species, Dab1 is expressed in cortical plate cells. These data suggest that the reelin/Dab1 pathway was a driver of cortical evolution on the synapsid lineage and that similarities in radial cortical organization between squamates and mammals result from evolutionary convergence.

Animals↗
PubMed2000

Rapid evolution of a geographic cline in size in an introduced fly.

The introduction and rapid spread of Drosophila subobscura in the New World two decades ago provide an opportunity to determine the predictability and rate of evolution of a geographic cline. In ancestral Old World populations, wing length increases clinally with latitude. In North American populations, no wing length cline was detected one decade after the introduction. After two decades, however, a cline has evolved and largely converged on the ancestral cline. The rate of morphological evolution on a continental scale is very fast, relative even to rates measured within local populations. Nevertheless, different wing sections dominate the New versus Old World clines. Thus, the evolution of geographic variation in wing length has been predictable, but the means by which the cline is achieved is contingent.

Animals↗
PubMed2006

Dishevelled genes mediate a conserved mammalian PCP pathway to regulate convergent extension during neurulation.

The planar cell polarity (PCP) pathway is conserved throughout evolution, but it mediates distinct developmental processes. In Drosophila, members of the PCP pathway localize in a polarized fashion to specify the cellular polarity within the plane of the epithelium, perpendicular to the apicobasal axis of the cell. In Xenopus and zebrafish, several homologs of the components of the fly PCP pathway control convergent extension. We have shown previously that mammalian PCP homologs regulate both cell polarity and polarized extension in the cochlea in the mouse. Here we show, using mice with null mutations in two mammalian Dishevelled homologs, Dvl1 and Dvl2, that during neurulation a homologous mammalian PCP pathway regulates concomitant lengthening and narrowing of the neural plate, a morphogenetic process defined as convergent extension. Dvl2 genetically interacts with Loop-tail, a point mutation in the mammalian PCP gene Vangl2, during neurulation. By generating Dvl2 BAC (bacterial artificial chromosome) transgenes and introducing different domain deletions and a point mutation identical to the dsh1 allele in fly, we further demonstrated a high degree of conservation between Dvl function in mammalian convergent extension and the PCP pathway in fly. In the neuroepithelium of neurulating embryos, Dvl2 shows DEP domain-dependent membrane localization, a pre-requisite for its involvement in convergent extension. Intriguing, the Loop-tail mutation that disrupts both convergent extension in the neuroepithelium and PCP in the cochlea does not disrupt Dvl2 membrane distribution in the neuroepithelium, in contrast to its drastic effect on Dvl2 localization in the cochlea. These results are discussed in light of recent models on PCP and convergent extension.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Ancestral sequence reconstruction in primate mitochondrial DNA: compositional bias and effect on functional inference.

Reconstruction of ancestral DNA and amino acid sequences is an important means of inferring information about past evolutionary events. Such reconstructions suggest changes in molecular function and evolutionary processes over the course of evolution and are used to infer adaptation and convergence. Maximum likelihood (ML) is generally thought to provide relatively accurate reconstructed sequences compared to parsimony, but both methods lead to the inference of multiple directional changes in nucleotide frequencies in primate mitochondrial DNA (mtDNA). To better understand this surprising result, as well as to better understand how parsimony and ML differ, we constructed a series of computationally simple "conditional pathway" methods that differed in the number of substitutions allowed per site along each branch, and we also evaluated the entire Bayesian posterior frequency distribution of reconstructed ancestral states. We analyzed primate mitochondrial cytochrome b (Cyt-b) and cytochrome oxidase subunit I (COI) genes and found that ML reconstructs ancestral frequencies that are often more different from tip sequences than are parsimony reconstructions. In contrast, frequency reconstructions based on the posterior ensemble more closely resemble extant nucleotide frequencies. Simulations indicate that these differences in ancestral sequence inference are probably due to deterministic bias caused by high uncertainty in the optimization-based ancestral reconstruction methods (parsimony, ML, Bayesian maximum a posteriori). In contrast, ancestral nucleotide frequencies based on an average of the Bayesian set of credible ancestral sequences are much less biased. The methods involving simpler conditional pathway calculations have slightly reduced likelihood values compared to full likelihood calculations, but they can provide fairly unbiased nucleotide reconstructions and may be useful in more complex phylogenetic analyses than considered here due to their speed and flexibility. To determine whether biased reconstructions using optimization methods might affect inferences of functional properties, ancestral primate mitochondrial tRNA sequences were inferred and helix-forming propensities for conserved pairs were evaluated in silico. For ambiguously reconstructed nucleotides at sites with high base composition variability, ancestral tRNA sequences from Bayesian analyses were more compatible with canonical base pairing than were those inferred by other methods. Thus, nucleotide bias in reconstructed sequences apparently can lead to serious bias and inaccuracies in functional predictions.

Animals↗
PubMed1997

The shape of cell death.

Cell death, a scheduled event during development and tissue turnover, or the ultimate consequence of toxic or pathologic insults seems to involve a relatively limited number of execution pathways. This reflects the evolution of an organized sequence of events perhaps converging onto final common pathways that are used to dispose of unwanted or injured cells. In many cases, the ordered execution of this internal death program leads to typical morphological and biochemical changes that have been termed apoptosis. Apoptosis, often equated with developmental or programmed cell death, has been opposed to unscheduled or accidental cell lysis/necrosis. However, increasing evidence suggests that the two forms of cell demise share similar characteristics, at least in the signaling and early progression phase. Recent studies have shown that, when the intensity of the insult is very high and/or when ATP generation is deficient, cells fail to execute the ordered changes ensuing in apoptosis. Then cell lysis/necrosis supervenes before the processes leading to nuclear condensation and exposure of surface molecules can be completed. Thus, apoptosis and necrosis seem to represent only different shapes of cell demise, resulting from a more or less complete execution of the internal death program.

Animals↗
PubMed2002

An overview of a free-market approach to climate change and conservation.

This paper describes the convergence of environmental and financial markets, reviews the evolution of market-based environmental programmes as an example of the seven-stage evolutionary process witnessed in a variety of markets and summarizes the emergence of greenhouse-gas-mitigation markets and their potential role in advancing land stewardship, biodiversity and other environmental services. Emissions trading has been developed to meet the demand to reduce pollution while avoiding economic disruption. Consistent with the seven-stage pattern of market evolution, the US programme to reduce the damage from acid rain established a standardized environmental commodity, developed 'evidence of ownership' necessary for financial instruments and provided the infrastructure to efficiently transfer title. The success of the system in reducing pollution at low cost has provided a model for other market-based environmental protection initiatives. The demand for cost-effective action to reduce the threat of climate change has initiated the same evolutionary process for markets to reduce greenhouse-gas emissions. Many of the land- and forest-management practices that can capture and store atmospheric CO(2) can also provide other environmental benefits, such as biodiversity preservation and enhanced water quality. The presence of a carbon-trading market will introduce a clear financial value for capture and mitigation of CO(2) emissions, thus introducing a new source of funding for land stewardship and forest rehabilitation. The market is now emerging through a variety of 'bottom-up' developments being undertaken through governmental, multilateral, private-sector and non-governmental-organization initiatives. The extension of markets to other emerging environmental issues is now underway, and the linkages between environmental sustainability and capital markets are being more deeply understood. The early evidence indicates that environmental sustainability can be compatible with maximization of shareholder value.

Air Pollution↗
PubMed1995

Premalignant epithelium and microinvasive cancer of the vocal fold: the evolution of phonomicrosurgical management.

Phonomicrosurgical treatment of premalignant vocal fold epithelium and microinvasive cancer combines principles of surgical oncology with advanced laryngoscopic microsurgical-techniques. This treatment is guided by mucosal-wave theory of voice production and strives not only to cure the disease but also to achieve optimal vocal function. Surgical techniques developed during the past two centuries have improved methods for vocal fold visualization, tissue retrieval, and tissue evaluation. Examination of the evolution of these surgical techniques reveals the incomplete convergence of laryngoscopic surgical theory with both the concept of premalignancy and the anatomical-physiological principles of voice production. This historical review, which helps to explain the lack of consensus about current treatment options, led to a series of four investigations. They were conducted with the aim of developing a laryngoscopic (phonomicrosurgical) management approach for improving the treatment of premalignant and microinvasive vocal fold epithelium. In the first of four investigations, 42 patients (each of whom had a significant smoking history) underwent microlaryngoscopic biopsy of 52 vocal fold lesions. These lesions, which were suspicious for atypia or malignancy and were confined to the musculomembranous vocal fold, were mapped according to surface involvement and depth of penetration. Review of the maps revealed that 27 of the 52 lesions involved only the superior/ventricular surface. For these patients, the entire layered vocal fold structure could potentially be preserved on the medial/vocalizing surface. Twenty-five of the 52 lesions involved both the superior/ventricular surface and the medial/vocalizing surface. No lesion involved only the medial surface. These data suggest that (in smokers) geographic localization of keratotic and erythroplastic lesions on the superior/ventricular surface of the musculomembranous vocal fold are likely to contain atypia. This characteristic facilitates the appropriate selection of patients for biopsy and may spare individuals, who have lesions resulting from hyperfunctional dysphonia and/or gastroesophageal reflux, from unnecessary biopsy. These two disorders typically result in pathology on the medial and/or posterior glottal surfaces. In order to determine whether a directed biopsy or an excisional biopsy approach is preferable for obtaining an accurate diagnosis, all specimens underwent whole-mount sectioning for three-dimensional histopathological analysis. Keratosis was noted: without atypia in 14; with atypia in 27; and with carcinoma in 11. The severity of the atypia usually varied throughout each specimen. The surface appearance of the lesion was not a reliable prognosticator of the severity of dysplasia either between patients or in different areas of the same lesion; therefore, excisional biopsy and whole-mount, multiple-section histopathological analysis were necessary for obtaining an accurate diagnosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Biopsy↗
PubMed1984

On the frog amphibian papilla.

Comparative morphological studies in living species of frogs and toads (anurans) indicate that the amphibian papilla (a specialized auditory sensory organ of the amphibian inner ear) has undergone considerable elongation over the course of evolution. Physiological studies on the amphibian papilla of one recently-derived species (Rana catesbeiana) provide strong evidence that frequency selectivity (tuning) in that organ is accomplished by one or more traveling wave structures, in many ways analogous to that of the mammalian cochlea. I suggest that the process of elongation inferred from the comparative morphology is a direct reflection of the evolution of a single traveling wave structure (i.e., convergence on an auditory mechanism analogous to that in the mammal). One selective advantage of such a mechanism is the combination of high rejection ratio in frequency filtering and good temporal resolution of acoustical stimuli.

Animals↗
PubMed1999

Molecular phylogeny of the marmots (Rodentia: Sciuridae): tests of evolutionary and biogeographic hypotheses.

There are 14 species of marmots distributed across the Holarctic, and despite extensive systematic study, their phylogenetic relationships remain largely unresolved. In particular, comprehensive studies have been lacking. A well-supported phylogeny is needed to place the numerous ecological and behavioral studies on marmots in an evolutionary context. To address this situation, we obtained complete cytochrome (cyt) b sequences for 13 of the species and a partial sequence for the 14th. We applied a statistical approach to both phylogeny estimation and hypothesis testing, using parsimony and maximum likelihood-based methods. We conducted statistical tests on a suite of previously proposed hypotheses of phylogenetic relationships and biogeographic histories. The cyt b data strongly support the monophyly of Marmota and a western montane clade in the Nearctic. Although some other scenarios cannot be rejected, the results are consistent with an initial diversification in North America, followed by an invasion and subsequent rapid diversification in the Palearctic. These analyses reject the two major competing hypotheses of M. broweri's phylogenetic relationships--namely, that it is the sister species to M. camtschatica of eastern Siberia, and that it is related closely to M. caligata of the Nearctic. The Alaskan distribution of M. broweri is best explained as a reinvasion from the Palearctic, but a Nearctic origin can not be rejected. Several other conventionally recognized species groups can also be rejected. Social evolution has been homoplastic, with large colonial systems evolving in two groups convergently. The cyt b data do not provide unambiguous resolution of several basal nodes in the Palearctic radiation, leaving some aspects of pelage and karyotypic evolution equivocal.

Animals↗
PubMed1994

Molecular adaptation of a leaf-eating bird: stomach lysozyme of the hoatzin.

This report describes a lysozyme expressed at high levels in the stomach of the hoatzin, the only known foregut-fermenting bird. Evolutionary comparison places it among the calcium-binding lysozymes rather than among the conventional types. Conventional lysozymes were recruited as digestive enzymes twice in the evolution of mammalian foregut fermenters, and these independently recruited lysozymes share convergent structural changes attributed to selective pressures in the stomach. Biochemical convergence and parallel amino acid replacements are observed in the hoatzin stomach lysozyme even though it has a different genetic origin from the mammalian examples and has undergone more than 300 million years of independent evolution.

Adaptation, Physiological↗
PubMed2002

Origin of plant glycerol transporters by horizontal gene transfer and functional recruitment.

Gene-family evolution mostly relies on gene duplication coupled with functional diversification of gene products. However, other evolutionary mechanisms may also be important in generating protein diversity. The ubiquitous membrane intrinsic protein (MIP) gene family is an excellent model system to search for such alternative evolutionary mechanisms. MIPs are proteins that transport water, glycerol, and small solutes across cell membranes in all living organisms. We reconstructed the molecular phylogeny of MIPs based on amino acid sequence data by using neighbor-joining, maximum-likelihood, and Bayesian methods of phylogenetic inference. The recovered trees show an early and distinct separation of water and glycerol transporters, i.e., aquaporins (AQPs), and aquaglyceroporins. The latter are absent from plants. As expected, gene duplication and functional diversification account for most of the diversity of animal and plant members of the family. However, in contrast to this model, we find that the sister group of plant glycerol transporters are bacterial AQPs. This relationship suggests first that plant glycerol transporters may resulted from a single event of horizontal gene transfer from bacteria, which we have estimated to have occurred approximately 1,200 million years ago, at the origin of plants, and second that bacterial AQPs were likely recruited to transport glycerol in plants because of their absence of aquaglyceroporins. This striking example of adaptive evolution at the molecular level was demonstrated further by finding convergent or parallel replacements at particular amino acid positions related to water- and glycerol-transporting specificity.

Amino Acid Sequence↗
PubMed1990

The networking standards evolution: toward a real electronic medical record. Interview by Carolyn Dunbar.

While converging networking standards have created short- and long-term options for healthcare IS planners, one strong goal is a "life-long, longitudinal electronic medical record" that includes data of all types--text, wave forms, voice, images and other pictorial data. Jack Harrington of Hewlett-Packard says these complex efforts are shaped by major forces that now speed progress toward multilateral acceptance of a uniform standard.

Computer Communication Networks↗
PubMed2003

The evolution of resource use.

The evolution of a consumer exploiting two resources is investigated. The strategy x under selection represents the fraction of time or energy an individual invests into extracting the first resource. In the model, a dimensionless parameter alpha quantifies how simultaneous consumption of both resources influences consumer growth; alpha<0 corresponds to hemi-essential resources, 0 1 corresponds to antagonistic resources. An analysis of the ecological and evolutionary dynamics leads to five conclusions. First, when alpha< or =1, there is a unique singular strategy x* for the adaptive dynamics and it is evolutionarily stable and globally convergent stable. Second, when alpha=1, the singular strategy x* corresponds to the populations exhibiting an ideal free distribution and a population playing this strategy can invade and displace populations playing any other strategy. Third, when alpha>1, the strategies x=0 and x=1 are evolutionarily stable and convergent stable. Hence, if the populations initially specialize on one resource, evolution amplifies this specialization. Fourth, when alpha is slightly larger than one (i.e. the resources are slightly antagonistic), there is a convergent stable singular strategy whose basin of attraction is almost the entire strategy space (0,1). This singular strategy is evolutionarily unstable and serves as an evolutionary branching point. Following evolutionary branching, our analysis and numerical simulations suggest that evolutionary dynamics are driven toward an end state consisting of two populations specializing on different resources. Fifth, when alpha>>1, there is only one singular strategy and it is convergent unstable and evolutionarily unstable. Hence, if resources are overly antagonistic, evolutionary branching does not occur and ultimately only one resource is exploited.

Animals↗