820 research outputs found

    The evolutionary origins of ritualized acoustic signals in caterpillars

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    Animal communication signals can be highly elaborate, and researchers have long sought explanations for their evolutionary origins. For example, how did signals such as the tail-fan display of a peacock, a firefly flash or a wolf howl evolve? Animal communication theory holds that many signals evolved from non-signalling behaviours through the process of ritualization. Empirical evidence for ritualization is limited, as it is necessary to examine living relatives with varying degrees of signal evolution within a phylogenetic framework. We examine the origins of vibratory territorial signals in caterpillars using comparative and molecular phylogenetic methods. We show that a highly ritualized vibratory signal—anal scraping—originated from a locomotory behaviour—walking. Furthermore, comparative behavioural analysis supports the hypothesis that ritualized vibratory signals derive from physical fighting behaviours. Thus, contestants signal their opponents to avoid the cost of fighting. Our study provides experimental evidence for the origins of a complex communication signal, through the process of ritualization

    Mitochondrial phylogeography and demographic history of the Vicuña: implications for conservation

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    The vicuña (Vicugna vicugna; Miller, 1924) is a conservation success story, having recovered from near extinction in the 1960s to current population levels estimated at 275 000. However, lack of information about its demographic history and genetic diversity has limited both our understanding of its recovery and the development of science-based conservation measures. To examine the evolution and recent demographic history of the vicuña across its current range and to assess its genetic variation and population structure, we sequenced mitochondrial DNA from the control region (CR) for 261 individuals from 29 populations across Peru, Chile and Argentina. Our results suggest that populations currently designated as Vicugna vicugna vicugna and Vicugna vicugna mensalis comprise separate mitochondrial lineages. The current population distribution appears to be the result of a recent demographic expansion associated with the last major glacial event of the Pleistocene in the northern (18 to 22°S) dry Andes 14–12 000 years ago and the establishment of an extremely arid belt known as the 'Dry Diagonal' to 29°S. Within the Dry Diagonal, small populations of V. v. vicugna appear to have survived showing the genetic signature of demographic isolation, whereas to the north V. v. mensalis populations underwent a rapid demographic expansion before recent anthropogenic impacts

    Evolution favors protein mutational robustness in sufficiently large populations

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    BACKGROUND: An important question is whether evolution favors properties such as mutational robustness or evolvability that do not directly benefit any individual, but can influence the course of future evolution. Functionally similar proteins can differ substantially in their robustness to mutations and capacity to evolve new functions, but it has remained unclear whether any of these differences might be due to evolutionary selection for these properties. RESULTS: Here we use laboratory experiments to demonstrate that evolution favors protein mutational robustness if the evolving population is sufficiently large. We neutrally evolve cytochrome P450 proteins under identical selection pressures and mutation rates in populations of different sizes, and show that proteins from the larger and thus more polymorphic population tend towards higher mutational robustness. Proteins from the larger population also evolve greater stability, a biophysical property that is known to enhance both mutational robustness and evolvability. The excess mutational robustness and stability is well described by existing mathematical theories, and can be quantitatively related to the way that the proteins occupy their neutral network. CONCLUSIONS: Our work is the first experimental demonstration of the general tendency of evolution to favor mutational robustness and protein stability in highly polymorphic populations. We suggest that this phenomenon may contribute to the mutational robustness and evolvability of viruses and bacteria that exist in large populations

    Vanishing native American dog lineages

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    <p>Abstract</p> <p>Background</p> <p>Dogs were an important element in many native American cultures at the time Europeans arrived. Although previous ancient DNA studies revealed the existence of unique native American mitochondrial sequences, these have not been found in modern dogs, mainly purebred, studied so far.</p> <p>Results</p> <p>We identified many previously undescribed mitochondrial control region sequences in 400 dogs from rural and isolated areas as well as street dogs from across the Americas. However, sequences of native American origin proved to be exceedingly rare, and we estimate that the native population contributed only a minor fraction of the gene pool that constitutes the modern population.</p> <p>Conclusions</p> <p>The high number of previously unidentified haplotypes in our sample suggests that a lot of unsampled genetic variation exists in non-breed dogs. Our results also suggest that the arrival of European colonists to the Americas may have led to an extensive replacement of the native American dog population by the dogs of the invaders.</p

    Persistent anthrax as a major driver of wildlife mortality in a tropical rainforest

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    Anthrax is a globally important animal disease and zoonosis. Despite this, our current knowledge of anthrax ecology is largely limited to arid ecosystems, where outbreaks are most commonly reported. Here we show that the dynamics of an anthrax-causing agent, Bacillus cereus biovar anthracis, in a tropical rainforest have severe consequences for local wildlife communities. Using data and samples collected over three decades, we show that rainforest anthrax is a persistent and widespread cause of death for a broad range of mammalian hosts. We predict that this pathogen will accelerate the decline and possibly result in the extirpation of local chimpanzee (Pan troglodytes verus) populations. We present the epidemiology of a cryptic pathogen and show that its presence has important implications for conservation

    Evolution of the mammalian lysozyme gene family

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    <p>Abstract</p> <p>Background</p> <p>Lysozyme <it>c </it>(chicken-type lysozyme) has an important role in host defense, and has been extensively studied as a model in molecular biology, enzymology, protein chemistry, and crystallography. Traditionally, lysozyme <it>c </it>has been considered to be part of a small family that includes genes for two other proteins, lactalbumin, which is found only in mammals, and calcium-binding lysozyme, which is found in only a few species of birds and mammals. More recently, additional testes-expressed members of this family have been identified in human and mouse, suggesting that the mammalian lysozyme gene family is larger than previously known.</p> <p>Results</p> <p>Here we characterize the extent and diversity of the lysozyme gene family in the genomes of phylogenetically diverse mammals, and show that this family contains at least eight different genes that likely duplicated prior to the diversification of extant mammals. These duplicated genes have largely been maintained, both in intron-exon structure and in genomic context, throughout mammalian evolution.</p> <p>Conclusions</p> <p>The mammalian lysozyme gene family is much larger than previously appreciated and consists of at least eight distinct genes scattered around the genome. Since the lysozyme <it>c </it>and lactalbumin proteins have acquired very different functions during evolution, it is likely that many of the other members of the lysozyme-like family will also have diverse and unexpected biological properties.</p

    Widespread Gene Conversion of Alpha-2-Fucosyltransferase Genes in Mammals

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    The alpha-2-fucosyltransferases (α2FTs) are enzymes involved in the biosynthesis of α2fucosylated glycan structures. In mammalian genomes, there are three α2FT genes located in tandem—FUT1, FUT2, and Sec1—each contained within a single exon. It has been suggested that these genes originated from two successive duplications, with FUT1 being generated first and FUT2 and Sec1 second. Despite gene conversion being considered the main mechanism of concerted evolution in gene families, previous studies of primates α2FTs failed to detect it, although the occurrence of gene conversion between FUT2 and Sec1 was recently reported in a human allele. The primary aim of our work was to initiate a broader study on the molecular evolution of mammalian α2FTs. Sequence comparison leads us to confirm that the three genes appeared by two rounds of duplication. In addition, we were able to detect multiple gene-conversion events at the base of primates and within several nonprimate species involving FUT2 and Sec1. Gene conversion involving FUT1 and either FUT2 or Sec1 was also detected in rabbit. The extent of gene conversion between the α2FTs genes appears to be species-specific, possibly related to functional differentiation of these genes. With the exception of rabbits, gene conversion was not observed in the region coding the C-terminal part of the catalytic domain. In this region, the number of amino acids that are identical between FUT1 and FUT2, but different in Sec1, is higher than in other parts of the protein. The biologic meaning of this observation may be related to functional constraints

    Transient Receptor Potential Ion Channels Control Thermoregulatory Behaviour in Reptiles

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    Biological functions are governed by thermodynamics, and animals regulate their body temperature to optimise cellular performance and to avoid harmful extremes. The capacity to sense environmental and internal temperatures is a prerequisite for the evolution of thermoregulation. However, the mechanisms that enable ectothermic vertebrates to sense heat remain unknown. The recently discovered thermal characteristics of transient receptor potential ion channels (TRP) render these proteins suitable to act as temperature sensors. Here we test the hypothesis that TRPs are present in reptiles and function to control thermoregulatory behaviour. We show that the hot-sensing TRPV1 is expressed in a crocodile (Crocodylus porosus), an agamid (Amphibolurus muricatus) and a scincid (Pseudemoia entrecasteauxii) lizard, as well as in the quail and zebrafinch (Coturnix chinensis and Poephila guttata). The TRPV1 genes from all reptiles form a unique clade that is delineated from the mammalian and the ancestral Xenopus sequences by an insertion of two amino acids. TRPV1 and the cool-sensing TRPM8 are expressed in liver, muscle (transversospinalis complex), and heart tissues of the crocodile, and have the potential to act as internal thermometer and as external temperatures sensors. Inhibition of TRPV1 and TRPM8 in C. porosus abolishes the typically reptilian shuttling behaviour between cooling and heating environments, and leads to significantly altered body temperature patterns. Our results provide the proximate mechanism of thermal selection in terrestrial ectotherms, which heralds a fundamental change in interpretation, because TRPs provide the mechanism for a tissue-specific input into the animals' thermoregulatory response

    An Earthworm Riddle: Systematics and Phylogeography of the Spanish Lumbricid Postandrilus

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    As currently defined, the genus Postandrilus Qui and Bouché, 1998, (Lumbricidae) includes six earthworm species, five occurring in Majorca (Baleares Islands, western Mediterranean) and another in Galicia (NW Spain). This disjunct and restricted distribution raises some interesting phylogeographic questions: (1) Is Postandrilus distribution the result of the separation of the Baleares-Kabylies (BK) microplate from the proto-Iberian Peninsula in the Late Oligocene (30-28 Mya)--vicariant hypothesis? (2) Did Postandrilus diversify in Spain and then colonize the Baleares during the Messinian salinity crisis (MSC) 5.96-5.33 Mya--dispersal hypothesis? (3) Is the distribution the result of a two-step process--vicariance with subsequent dispersal?To answer these questions and assess Postandrilus evolutionary relationships and systematics, we collected all of the six Postandrilus species (46 specimens - 16 locations) and used Aporrectodea morenoe and three Prosellodrilus and two Cataladrilus species as the outgroup. Regions of the nuclear 28S rDNA and mitochondrial 16S rDNA, 12S rDNA, ND1, COII and tRNA genes (4,666 bp) were sequenced and analyzed using maximum likelihood and Bayesian methods of phylogenetic and divergence time estimation. The resulting trees revealed six new Postandrilus species in Majorca that clustered with the other five species already described. This Majorcan clade was sister to an Iberian clade including A. morenoe (outgroup) and Postandrilus bertae. Our phylogeny and divergence time estimates indicated that the split between the Iberian and Majorcan Postandrilus clades took place 30.1 Mya, in concordance with the break of the BK microplate from the proto-Iberian Peninsula, and that the present Majorcan clade diversified 5.7 Mya, during the MSC.Postandrilus is highly diverse including multiple cryptic species in Majorca. The genus is not monophyletic and invalid as currently defined. Postandrilus is of vicariant origin and its radiation began in the Late Oligocene
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