Search results for " speciation"

Parapatric diversification after post-glacial range expansion in the gall flyUrophora cardui(Tephritidae)

2010

Aim  Primary and secondary genetic clines in post-glacial colonized regions have different implications for biogeographic distributions and the origin of species. Primary clines arise in situ after colonization as adaptive responses to environmental gradients, while secondary clines are caused by contact between vicariant lineages. Here we analyse primary versus secondary origin of a genetic cline in the tephritid fly Urophora cardui in Jutland, Denmark, in a post-glacial landscape. Location  Western Palaearctic. Methods  Phylogeographic and demographic analyses of U. cardui based on mitochondrial DNA (mtDNA) genealogies, hierarchical genetic variance tests based on allozymes and distributi…

Mate recognition as a reproductive barrier in sexual and parthenogenetic Eucypris virens (Crustacea, Ostracoda)

2013

Mate selection is one of the motors of evolution and of particular importance in the case of organisms in which sexual and parthenogenetic populations coexist. Sexual populations of the ostracod species complex Eucypris virens are often mixed with parthenogenetic ones. A powerful mate selection mechanism must exist to avoid time, energy and sperm loss, for the maintenance and success of sexual reproduction in these mixed populations. There are four types of E. virens individuals: males (diploid), sexual females (diploid) and asexual females (parthenogenetic and either di- or triploid). From one parthenogenetic population and two populations with males of E. virens, we sampled early stage ju…

On the identity of Ischyropsalis dentipalpis Canestrini, 1872 and description of Ischyropsalis lithoclasica sp. n. (Opiliones: Ischyropsalididae)

2010

Ischyropsalis dentipalpis Canestrini, 1872 is re-defined, and a neotype from the type locality in the Aosta Valley, Italy, is assigned. I. helvetica Roewer, 1916 (sensu Martens 1978) is shown to be conspecific and therefore is synonymised with I. dentipalpis. A population from Bergamo Province, Italy, formerly assigned to I. dentipalpis (sensu Martens 1978), is here regarded as a different species and described under the name Ischyropsalis lithoclasica sp. n. Discrimination of males is possible by genital characters and by the shape of the cheliceral and pedipalpal apophyses. Females are distinguished by peculiarities of cheliceral spination. The distribution of I. lithoclasica n. sp. is al…

Leaf shape variation and taxonomic boundaries in two sympatric rupicolous species of Helichrysum (Asteraceae: Gnaphalieae), assessed by linear measur…

2012

Quantifying and understanding the causes of population differentiation in plants are critical for assessing the taxonomic structure of species, as the level of differentiation among populations may correspond to incipient speciation. Using linear and geometric morphometric approaches, phenotypic variation and associations between leaf traits and geographic and environmental characteristics were investigated in Helichrysum crassifolium and the widespread and sympatric Helichrysum pendulum: two species exhibiting conspicuous leaf variation in size and shape. The morphometric results show that both species have distinct patterns of leaf shape variation. However, overlapping values link the ran…

Differences in parasite susceptibility and costs of resistance between naturally exposed and unexposed host populations

2009

It is generally assumed that resistance to parasitism entails costs. Consequently, hosts evolving in the absence of parasites are predicted to invest less in costly resistance mechanisms than hosts consistently exposed to parasites. This prediction has, however, rarely been tested in natural populations. We studied the susceptibility of three naïve, three parasitized and one recently isolated Asellus aquaticus isopod populations to an acanthocephalan parasite. We found that parasitized populations, with the exception of the isopod population sympatric with the parasite strain used, were less susceptible to the parasite than the naïve populations. Exposed but uninfected (resistant) isopods f…

2015

The Indonesian island of Sulawesi harbors a highly endemic and diverse fauna sparking fascination since long before Wallace’s contemplation of biogeographical patterns in the region. Allopatric diversification driven by geological or climatic processes has been identified as the main mechanism shaping present faunal distribution on the island. There is both consensus and conflict among range patterns of terrestrial species pointing to the different effects of vicariant events on once co-distributed taxa. Tarsiers, small nocturnal primates with possible evidence of an Eocene fossil record on the Asian mainland, are at present exclusively found in insular Southeast Asia. Sulawesi is hotspot o…

Equilibrium Studies in Natural Fluids. A Chemical Speciation Model for the Major Constituents of Seawater.

1994

AbstractThe speciation of CI−, OH− and SO42- in synthetic sea water has been studied by Potentiometric measurements (pH-metric and ISE-Na methods) and by literature data analysis, using a well tested complex formation model. Stability constants, together with distribution of hypothesised species in synthetic sea water, as a function of temperature and salinity, are reported. The speciation model proposed in this work is discussed on the basis of chemical and statistical considerations. Comparison with some literature sea water models is given.

A new species of Armeria (Plumbaginaceae) from southern Spain with molecular and morphometric evidence on its origin

2001

The definitive version is available at http://onlinelibrary.wiley.com/

Divergent parasite infections in sympatric cichlid species in Lake Victoria

2018

Parasitism has been proposed as a factor in host speciation, as an agent affecting coexistence of host species in species‐rich communities and as a driver of post‐speciation diversification. Young adaptive radiations of closely related host species of varying ecological and genomic differentiation provide interesting opportunities to explore interactions between patterns of parasitism, divergence and coexistence of sympatric host species. Here, we explored patterns in ectoparasitism in a community of 16 fully sympatric cichlid species at Makobe Island in Lake Victoria, a model system of vertebrate adaptive radiation. We asked whether host niche, host abundance or host genetic differentiatio…

Hybridization, developmental stability, and functionality of morphological traits in the ground beetle Carabus solieri (Coleoptera, Carabidae).

2006

Correspondance.: stephane.garnier@u-bourgogne.fr; International audience; The assessment of developmental stability in hybrids can provide valuable information in the study of species formation because it allows an evaluation of the degree of incompatibility of genetic systems that control developmental processes. The present study assessed the impact of two hybridization events, assumed to have occurred at different times, on developmental instability in the ground beetle Carabus solieri . Developmental instability was estimated in 678 individuals from 27 populations from the fluctuating asymmetry (FA) levels of four morphological traits: the tibia length of middle and hind legs, which are…