Search results for "Biological Evolution"

The phylogeny of the European high mountain genus Adenostyles (Asteraceae-Senecioneae) reveals that edaphic shifts coincide with dispersal events.

2013

UNLABELLED PREMISE OF THE STUDY Heterogeneity of edaphic conditions plays a large role in driving the diversification of many plant groups. In the Alps and other European high mountains, many closely related calcicole and calcifuge plant taxa exist. To better understand patterns and processes of edaphic differentiation, the phylogeny of the edaphically variable genus Adenostyles was studied. The genus contains three species, of which A. alpina has five subspecies. Each species and subspecies is largely confined to either calcareous or noncalcareous substrates. • METHODS We analyzed the phylogeny of Adenostyles using DNA sequences of nrITS, nrETS, nuclear chalcone synthase, and three plastid…

1993

Observers of the past and present noted an extraordinary diversity in the organic world: A snail is different from a river crayfish, which differs from a starfish, which in turn has nothing in common with a lobster or even man.

THERMOREGULATION CONSTRAINS EFFECTIVE WARNING SIGNAL EXPRESSION

2009

Evolution of conspicuous signals may be constrained if animal coloration has nonsignaling as well as signaling functions. In aposematic wood tiger moth (Parasemia plantaginis) larvae, the size of a warning signal (orange patch on black body) varies phenotypically and genetically. Although a large warning signal is favored as an antipredator defense, we hypothesized that thermoregulation may constrain the signal size in colder habitats. To test this hypothesis, we conducted a factorial rearing experiment with two selection lines for larval coloration (small and large signal) and with two temperature manipulations (high and low temperature environment). Temperature constrained the size and br…

Comparative evolution of P–M system and infection by the sigma virus in French and Spanish populations ofDrosophila melanogaster

1992

SummaryIn 1983, an extensive survey of populations ofD. melanogasterwas started in a southern French region (Languedoc) in two non-Mendelian systems: the P–M system of transposable elements and the hereditary Rhabdovirus sigma. Unexpectedly fast-evolving phenomena were observed and interesting correlations were noted, giving similar geographical pattern to the region in both systems. For these reasons, the analysis was continued and extended towards the north (Rhône Valley) and the south (Spain). In the P–M system, all the Languedoc populations evolved from 1983 to 1991 towards the Q type which is characteristic of the Rhône Valley populations. In contrast, M′ strains are currently observed…

Evolutionary history and diversity of arthropod hemocyanins

2004

Hemocyanins are copper-containing, multi-subunit proteins that transport oxygen in the hemolymph of many molluscs and arthropods [Markl and Decher, Adv. Comp. Environ. Physiol. 13 (1992) 325; van Holde et al., J. Biol. Chem. 276 (2001) 15563]. Arthropod hemocyanins originated more than 550 million years ago from oxygen-consuming phenoloxidases. Hemocyanins are present in various Onychophora, Chelicerata, Myriapoda, Crustacea, and Hexapoda, but subunit evolution differs striking in these arthropod subphyla. Hemocyanins also gave rise to non-respiratory proteins (crustacean pseudo-hemocyanins, insect hexamerins, and hexamerin receptors), which most likely have storage functions.

Prebiotic polypeptides and the origin of biological information.

1983

Recent data on the origin of biological information are reviewed. These data corroborate the view that polyamino acids were the first informational polymers. The source of information is seen in the chemical reactivity of amino acids, their prebiotic abundance and the prebiotic environment. Evidence is presented in favor of Matsuno's protohypercycle that may have preceded Eigen's hypercycle, but that involves a translation of information from polypeptides into that of polynucleotides.

Modelling the evolution of cognitive styles.

2019

Abstract Individuals consistently differ in behaviour, exhibiting so-called personalities. In many species, individuals differ also in their cognitive abilities. When personalities and cognitive abilities occur in distinct combinations, they can be described as ‘cognitive styles’. Both empirical and theoretical investigations produced contradicting or mixed results regarding the complex interplay between cognitive styles and environmental conditions. Here we use individual-based simulations to show that, under just slightly different environmental conditions, different cognitive styles exist and under a variety of conditions, can also co-exist. Co-existences are based on individual speciali…

On hidden heterogeneity in directional asymmetry – can systematic bias be avoided?

2006

8 pages; International audience; Directional asymmetry (DA) biases the analysis of fluctuating asymmetry (FA) mainly because among-individual differences in the predisposition for DA are difficult to detect. However, we argue that systematic bias mainly results from predictable associations between signed right-left asymmetry and other factors, i.e. from systematic variation in DA. We here demonstrate methods to test and correct for this, by analysing bilateral asymmetry in size and shape of an irregular sea urchin. Notably, in this model system, DA depended significantly on body length and geographic origin, although mean signed asymmetry (mean DA) was not significant in the sample as a wh…

Consistent phenological shifts in the making of a biodiversity hotspot: the Cape flora

2011

Abstract Background The best documented survival responses of organisms to past climate change on short (glacial-interglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. Results Forty-three dist…

Why are defensive toxins so variable? An evolutionary perspective

2012

Defensive toxins are widely used by animals, plants and micro-organisms to deter natural enemies. An important characteristic of such defences is diversity both in the quantity of toxins and the profile of specific defensive chemicals present. Here we evaluate evolutionary and ecological explanations for the persistence of toxin diversity within prey populations, drawing together a range of explanations from the literature, and adding new hypotheses. We consider toxin diversity in three ways: (1) the absence of toxicity in a proportion of individuals in an otherwise toxic prey population (automimicry); (2) broad variation in quantities of toxin within individuals in the same population; (3)…