Search results for "POPULATION"

Morphological and genetic analyses reveal a cryptic species complex in the echinoid Echinocardium cordatum and rule out a stabilizing selection expla…

2014

14 pages; International audience; Preliminary analyses revealed the presence of at least five mitochondrial clades within the widespread sea urchin Echinocardium cordatum (Spatangoida). In this study, we analyzed the genetic (two mitochondrial and two nuclear sequence loci) and morphological characteristics (20 indices) from worldwide samples of this taxon to establish the species limits, morphological diversity and differentiation. Co-occurring spatangoid species were also analyzed with mitochondrial DNA. The nuclear sequences confirm that mitochondrial lineages correspond to true genetic entities and reveal that two clades (named A and B1) hybridize in their sympatry area, although a more…

2017

This article reviews research on the evolutionary mechanisms leading to different transmission modes. Such modes are often under genetic control of the host or the pathogen, and often in conflict with each other via trade-offs. Transmission modes may vary among pathogen strains and among host populations. Evolutionary changes in transmission mode have been inferred through experimental and phylogenetic studies, including changes in transmission associated with host shifts and with evolution of the unusually complex life cycles of many parasites. Understanding the forces that determine the evolution of particular transmission modes presents a fascinating medley of problems for which there is…

Fluctuating Asymmetry in Central and Marginal Populations of Lychnis viscaria in Relation to Genetic and Environmental Factors

1998

Developmental instability in the form of increased fluctuating asymmetry can be caused by either genetic or environmental stress. Because extinctions can be attributed broadly to these factors, fluctuating asymmetry may provide a sensitive tool for detecting such stresses. We studied the level of fluctuating asymmetry of flowers of a perennial outcrossing plant species, Lychnis viscaria, both in natural and common-garden populations. The degree of flower asymmetry was higher in small, isolated, and marginal populations of the species range. These marginal populations also were the most homozygous. In the core area of the species' range, flowers were more symmetrical The level of asymmetry w…

Natural Occurrence of Secondary Bacterial Symbionts in Aphids from Tunisia, with a Focus on Genus Hyalopterus

2018

Aphids (Hemiptera: Aphididae) can harbor two types of bacterial symbionts. In addition to the obligate endosymbiont Buchnera aphidicola Munson, Baumann and Kinsey 1991 (Enterobacteriales: Enterobacteriaceae), several facultative symbiotic bacteria, called secondary (S) symbionts, have been identified among many important pest aphid species. To determine interpopulational diversity of S-symbionts, we carried out a survey in a total of 18 populations of six aphid species collected from six localities in Tunisia, by performing a diagnostic polymerase chain reaction analysis of partial 16S-23S rRNA operon sequences. While 61.7% of individuals contained only Buchnera, three S-symbionts were foun…

Temporal variations in symbiotic hindgut protist community of the subterranean termite Reticulitermes lucifugus Rossi in Sicily.

2015

The dynamics of symbiotic protist communities of Reticulitermes lucifugus ‘‘Sicily’’ were investigated to assess the effects of seasonal environmental conditions and the termite’s feeding activity. In worker and soldier castes, the total protist population (total abundance), individual species abundances, and species proportions in their hindguts were examined monthly from December 2012 to February 2014. The main protist species taken into account were Dinenympha fimbriata Kirby, D. gracilis Leidy, Pyrsonympha flagellata Gras., Spirotrichonympha flagellata Grassi u. Fo` a, Holomastigotes elongatum Grassi u. Fo`a, and Trichonympha agilis Leidy, while others were not specifically identified, …

Evolutionary rescue at different rates of environmental change is affected by trade-offs between short-term performance and long-term survival.

2021

As climate change accelerates and habitats free from anthropogenic impacts diminish, populations are forced to migrate or to adapt quickly. Evolutionary rescue (ER) is a phenomenon, in which a population is able to avoid extinction through adaptation. ER is considered to be more likely at slower rates of environmental change. However, the effects of correlated characters on evolutionary rescue are seldom explored yet correlated characters could play a major role in ER. We tested how evolutionary background in different fluctuating environments and the rate of environmental change affect the probability of ER by exposing populations of the bacteria Serratia marcescens to two different rates …

On the thermodynamic origin of metabolic scaling

2018

The origin and shape of metabolic scaling has been controversial since Kleiber found that basal metabolic rate of animals seemed to vary as a power law of their body mass with exponent 3/4, instead of 2/3, as a surface-to-volume argument predicts. The universality of exponent 3/4 -claimed in terms of the fractal properties of the nutrient network- has recently been challenged according to empirical evidence that observed a wealth of robust exponents deviating from 3/4. Here we present a conceptually simple thermodynamic framework, where the dependence of metabolic rate with body mass emerges from a trade-off between the energy dissipated as heat and the energy efficiently used by the organi…

Changes in freshwater sediment microbial populations during fermentation of crude glycerol

2020

This work was supported by the Latvian Council of Science , project NN-CARMA, project No. lzp-2018/1-0194.

Ancient DNA reveals the Arctic origin of Viking Age cod from Haithabu, Germany

2017

Knowledge of the range and chronology of historic trade and long-distance transport of natural resources is essential for determining the impacts of past human activities on marine environments. However, the specific biological sources of imported fauna are often difficult to identify, in particular if species have a wide spatial distribution and lack clear osteological or isotopic differentiation between populations. Here, we report that ancient fish-bone remains, despite being porous, brittle, and light, provide an excellent source of endogenous DNA (15-46%) of sufficient quality for whole-genome reconstruction. By comparing ancient sequence data to that of modern specimens, we determine …

A roadmap for understanding the evolutionary significance of structural genomic variation

2020

Author's accepted manuscript Structural genomic variants (SVs) take diverse forms and are ubiquitous drivers of ecological and evolutionary processes. Most studies of SVs focus on the adaptive significance of gene duplications and large inversions. Future studies should catalog SVs of all types and sizes and systematically test their evolutionary implications. We propose a roadmap and definitions for the study of SVs in ecological and evolutionary genomics. Best practices for SV detection are needed to facilitate comparisons across studies. Integrating population genomic, theoretical, and experimental approaches to SVs will more comprehensively characterize genomic variation, uncover the ad…