Search results for "field"

Measured immunocompetence relates to the proportion of dead parasites in a wild roach population

2009

Summary 1. Although various methods are used to measure immunocompetence, their relationship with the actual parasite clearance or parasite load is seldom demonstrated in natural systems. 2. We combined nine measures of immune function using principal component analysis (PCA), and examined the relationship of the collective measures with (i) the proportion of parasites killed by the host, (ii) the burden of several parasite species and (iii) a viral disease in a wild population of the roach, Rutilus rutilus. We also studied if these variables were associated with the concentration of steroids (testosterone and oestradiol). 3. Most significant correlations between the loads of ecto- and gill…

When morphometry meets genetics: inferring the phylogeography of Carabus solieri using Fourier analyses of pronotum and male genitalia

2004

Population differentiation is a crucial step in the speciation process and is therefore a central subject in studies of microevolution. Assessing divergence and inferring its dynamics in space and time generally require a wide array of markers. Until now however, most studies of population structure are based on molecular markers and those concerning morphological traits are more scarce. In the present work, we studied morphological differentiation among populations of the ground beetle Carabus solieri, and tested its congruence with genetic population structure. The shape of pronotum and aedeagus was assessed using Dual Axis Fourier Shape Analysis. manova on Fourier coefficients revealed h…

Exploring phylogeography and species limits in the Altai vole (Rodentia: Cricetidae)

2013

Natural hybridization between species is not a rare event. In arvicoline rodents, hybridization is known to occur in the wild and/or in captivity. In the Microtus arvalis group, cytogenetic studies revealed that there were two distinct chromosomal forms (2n = 46 but a different fundamental number of autosomes). These forms have been attributed to two cryptic species: the common (arvalis) and Altai (obscurus) voles. Recently, individuals with intermediate karyotypes (F1 and backcrosses) were discovered in central European Russia, and, for this reason, other studies have regarded obscurus and arvalis as conspecific. In the present study, to address the question of the species limits in the Al…

Evolutionary population dynamics

2005

The interface between the evolution of life history traits and population dynamics in temporally and spatially variable environments is the topic of this chapter. Thus, the frame for the life history processes is set by spatial and temporal fluctuations in population density. Here, we will focus primarily on modes of reproduction and we are especially interested in whether alternative reproductive strategies can co-exist in a population. We show that spatially structured populations may allow co-existence of various life history strategies that do not easily co-exist in a nonstructured environment. Also, intrinsic and external temporal fluctuations in the environment tend to enhance polymor…

2019

Aposematic organisms couple conspicuous warning signals with a secondary defense to deter predators from attacking. Novel signals of aposematic prey are expected to be selected against due to positive frequency-dependent selection. How, then, can novel phenotypes persist after they arise, and why do so many aposematic species exhibit intrapopulation signal variability? Using a polytypic poison frog ( Dendrobates tinctorius ), we explored the forces of selection on variable aposematic signals using 2 phenotypically distinct (white, yellow) populations. Contrary to expectations, local phenotype was not always better protected compared to novel phenotypes in either population; in the white po…

A Tale of Big Game and Small Bugs

1999

Animal populations undergo repetitive cycles of rising and falling numbers. In a Perspective, [Ranta and colleagues][1] discuss the value of time-series analyses for examining the changing dynamics of animal populations. A large time series gathered by the Hudson Bay Company based on the fur trade has provided invaluable data on the rise and fall of the Canadian lynx population from 1821 to the present. Analysis of this time series reveals that climate as well as factors influencing birth and death rates are important in regulating the lynx population ([ Stenseth et al .][2]). In a separate study, mathematical modeling combined with fieldwork revealed the importance of predators in determin…

Synchronicity in population systems: cause and consequence mixed

1999

Drosophila Evolution over Space and Time (DEST) - A New Population Genomics Resource

2021

Abstract Drosophila melanogaster is a leading model in population genetics and genomics, and a growing number of whole-genome datasets from natural populations of this species have been published over the last 20 years. A major challenge is the integration of these disparate datasets, often generated using different sequencing technologies and bioinformatic pipelines, which hampers our ability to address questions about the evolution and population structure of this species. Here we address these issues by developing a bioinformatics pipeline that maps pooled sequencing (Pool-Seq) reads from D. melanogaster to a hologenome consisting of fly and symbiont genomes and estimates allele frequenc…

Sex ratio and sexual conflict in a collective action problem

2020

AbstractThe maintenance of cooperation is difficult whenever collective action problems are vulnerable to freeriding (reaping the benefits without contributing to the maintenance of the good). We identify a novel factor that can make a system tolerate an extent of freeriding. If a population consists of discrete types with demographically distinct roles, such that the success of one type does not imply it can spread to replace other types in the population, then collective goods may persist in the presence of free-riders because they are necessarily kept in a minority role. Biased sex ratios (e.g. in haplodiploids) create conditions where individuals of one sex are a minority. We show that …

Harvesting‐induced population fluctuations?

2003

It has recently been shown that damped endogenous dynamics is a common feature in Finnish grouse species; In this paper, we demonstrate that time-variant harvesting may turn damped dynamics to quasi-periodic fluctuations. Exploited populations, e.g. grouse, may therefore fluctuate more than expected if we do not manage to keep the harvest fraction constant over time. However, the harvest fraction of Finnish grouse varies with the phase of the cycle. Such a harvesting strategy could potentially change the periodicity of the fluctuations, as can a threshold harvest strategy where a constant fraction is harvested above a density threshold. The two non-linear harvesting strategies investigated …