Search results for "sympatric speciation"
showing 10 items of 101 documents
Different spore structures in sympatric Isoetes histrix populations and their relationship with gross morphology, chromosome number, and ribosomal nu…
2011
Abstract Traditionally, megaspores have supplied the most relevant character for the taxonomy of Isoetes at several systematic levels, including discriminant features usually used in species identification and diagnosis. Isoetes histrix Bory is a terrestrial circum-Mediterranean quillwort characterized by dark, shiny, and persistent phyllopodia with megaspore sporangia completely covered by a velum and tuberculate megaspores. Specimens of this species from Sardinian temporary wetlands showed the sympatric presence of two kinds of individuals with correlated variation in size, ornamentation, and radial ridges of megaspores, and in ornamentation of microspores. However, they showed the same d…
Parasites in sympatric populations of native and invasive freshwater bivalves
2021
An increasing threat to local, native freshwater mussels (Unionida)—an ecologically important but globally alarmingly declining group— is the invasion by exotic bivalves. The Enemy Release Hypothesis predicts that introduced species should benefit from enemy-mediated competition because they are less likely to be harmed by natural enemies, such as parasites, than their native competitors. We investigated within-site differences in parasitism between sympatric native (tot. five spp.) and invasive (tot. three spp.) bivalves in eight northern European waterbodies, which harboured totally 15 parasite taxa. In paired comparisons using within-site averages, the mean number of parasite species in …
Behavioral reproductive isolation among sympatric strains of Brachionus plicatilis Müller 1786: insights into the status of this taxonomic species
1995
We present results on cross-mating experiments using Brachionus plicatilis strains collected in three ponds of a coastal marsh (Torreblanca Marsh, Castellon, Spain). These strains were known to differ widely both in morphology and allozyme patterns from a previous study, where they were grouped into three genetically different clonal groups. Although some of the strains co-occurred in the same pond and sexual periods overlapped, no gene flow was found among them. Our first objective was to determine whether behavioral reproductive isolation was responsible for the absence of interbreeding. A second objective was to explore the relationship between sexual isolation and genetic divergence. We…
Comparative phylogeography of the Veronica alpina complex in Europe and North America
2006
The Veronica alpina complex comprises eight species of alpine habitats over a wide range of mountain systems in the Northern Hemisphere. The occurrence of sympatric species in the European and North American mountain systems allowed us not only to investigate the effect of the ice ages on intraspecific phylogeographical patterns and genetic diversity in different continents of the Northern Hemisphere, but also to compare these patterns in closely related species. Plastid DNA trnL-F sequences and AFLP (amplified fragment length polymorphism) fingerprints were used to infer the phylogenetic history of the group and phylogeographical patterns within species. Hybrid origin of tetraploid eastern…
Dissimilar molecular and morphological patterns in an introgressed peripheral population of a sand dune species ( Armeria pungens , Plumbaginaceae)
2019
Introgression is a poorly understood evolutionary outcome of hybridisation because it may remain largely undetected whenever it involves the transfer of small parts of the genome from one species to another. Aiming to understand the early stages of this process, a putative case from the southernmost border of the Armeria pungens range from its congener A. macrophylla is revisited following the discovery of a subpopulation that does not show phenotypic signs of introgression and resembles typical A. pungens. We analysed morphometrics, nuclear ribosomal DNA ITS and plastid DNA (trnL‐trnF) sequences, genome size, 45S and 5S rDNA loci‐FISH data and nrDNA IGS sequences. Within the study site, mo…
The larva of Gomphus davidi Selys, 1887
1983
The female exuvia and last larval stage of Gomphus davidi Selys, 1887, a dragonfly endemic in the Middle East are described and figured. Distinctive characters of two sympatric Gomphus-species are provided.
Local adaptation of a holoparasitic plant, Cuscuta europaea: variation among populations
2000
Locally adapted parasites have higher infectivity and/or fitness on sympatric than on allopatric hosts. We tested local adaptation of a holoparasitic plant, Cuscuta europaea, to its host plant, Urtica dioica. We infected hosts from five sites with holoparasites from the same five sites and measured local adaptation in terms of infectivity and parasite performance (biomass) in a reciprocal cross-infection experiment. The virulence of the parasite did not differ between sympatric and allopatric hosts. Overall, parasites had higher infectivity on sympatric hosts but infectivity and parasite performance varied among populations. Parasites from one of the populations showed local adaptation in t…
The staminal lever mechanism in Salvia L. (Lamiaceae): a key innovation for adaptive radiation?
2004
Abstract Floral key innovations play a significant role in the discussion of adaptive radiation in plants. The paper brings together a brief review of morphological key innovations in plants, elucidating their evolutionary significance in flower–pollinator interactions, and new data on Salvia, a genus being examined as an example for presumed adaptive radiation. We hypothesize that the characteristic staminal lever mechanism functions as a key innovation. It is defined as a functional unit including the modification of stamens to lever-like structures, their reversible movement, and the organization of the remaining floral structures involved in the process of pollen transfer. We follow the…
Sex-pairing pheromones and reproductive isolation in three sympatric Cornitermes species (Isoptera, Termitidae, Syntermitinae)
2011
International audience; The species-specificity of pairing has been studied in three sympatric Neotropical termites: Cornitermes bequaerti, Cornitermes cumulans and Cornitermes silvestrii (Termitidae, Syntermitinae). Bioassays showed that sex attraction was highly species-specific between C. bequaerti and C cumulans but not between C. cumulans and C. silvestrii. The sex-pairing pheromone of the three species is secreted by the tergal glands of female alates. It consists of a common compound (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol. In C. bequaerti, this polyunsaturated alcohol is the only compound of the sex-pairing pheromone, whereas it is associated with the oxygenated sesquiterpene (E)-nerolid…
Identifying a key host in an acanthocephalan-amphipod system.
2015
SUMMARYTrophically transmitted parasites may use multiple intermediate hosts, some of which may be ‘key-hosts’, i.e. contributing significantly more to the completion of the parasite life cycle, while others may be ‘sink hosts’ with a poor contribution to parasite transmission. Gammarus fossarum and Gammarus roeseli are sympatric crustaceans used as intermediate hosts by the acanthocephalan Pomphorhynchus laevis. Gammarus roeseli suffers higher field prevalence and is less sensitive to parasite behavioural manipulation and to predation by definitive hosts. However, no data are available on between-host differences in susceptibility to P. laevis infection, making it difficult to untangle the…