Search results for "Biological dispersal"
showing 10 items of 326 documents
Areas of endemism in the Antarctic - a case study of the benthic hydrozoan genusOswaldella(Cnidaria, Kirchenpaueriidae)
2010
Aim The aim of this study is to investigate areas of endemism within the distribution of Oswaldella species in the Southern Ocean, thereby testing previous hypotheses and proposing alternative scenarios for Antarctic evolution. Location Southern Ocean, Antarctic and sub-Antarctic waters of southern South America. Methods We prepared a database for the 31 currently known species of the Antarctic genus Oswaldella, which includes geographical locations gathered from published taxonomic studies as well as materials from museums and expeditions. A parsimony analysis of endemicity (PAE) was used to test hypotheses of distribution patterns. Results Four areas of endemism are hypothesized: southern…
A stochastic model of seed dispersal pattern to assess seed predation by ants in annual dry grasslands
2005
A combined field experiment and modelling approach has been used to provide evidence that ants may be responsible for an observed lower patchiness and higher plant diversity in the neighbourhood of ant nests, within Mediterranean dry grasslands belonging to the phytosociological class Tuberarietea guttatae. The hypothesis was that seeds occurring in clumps may have an higher probability to be harvested than seeds having a scattered distribution. In order to test this hypothesis, four analysis steps have been performed. First, the seed productivity and dispersal pattern was recorded for four plant species found, either more abundant beside the ant nests (Tuberaria guttata, Euphorbia exigua) …
Genetic variability of the blue and red shrimp Aristeus antennatus in the Western Mediterranean Sea inferred by DNA microsatellite loci
2011
Genetic variation at eight microsatellite loci was studied in nine populations of the blue and red shrimp Aristeus antennatus to investigate whether distinct stocks are present in the Western Mediterranean Sea. A high level of gene flow and no evidence of genetic partitioning were discovered. No significant variation was found (FST = 0.00673, P-value = 0.067) even when shrimps from exploited and those from deep-water unexploited grounds were compared. No evidence of reduction or expansion of population size in the recent past was found, as indicated by the bottleneck and interlocus g-tests. Our results are consistent with previous studies using mitochondrial gene methods and allozymes, indi…
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…
Dispersal of larval and juvenile seabream: Implications for Mediterranean marine protected areas
2015
International audience; In the marine context, information about dispersal is essential for the design of networks of marine protected areas (MPAs). Generally, most of the dispersal of demersal fishes is thought to be driven by the transport of eggs and larvae in currents, with the potential contribution of dispersal in later life stages relatively minimal.Using otolith chemistry analyses, we estimate dispersal patterns across a spatial scale of approximately 180 km at both propagule (i.e. eggs and larvae) and juvenile (i.e. between settlement and recruitment) stages of a Mediterranean coastal fishery species, the two-banded seabream Diplodus vulgaris. We detected three major natal sources …
A legacy of contrasting spatial genetic structure on either side of the Atlantic-Mediterranean transition zone in a marine protist
2012
The mechanisms that underpin the varied spatial genetic structures exhibited by free-living marine microorganisms remain controversial, with most studies emphasizing a high dispersal capability that should redistribute genetic diversity in contrast to most macroorganisms whose populations often retain a genetic signature of demographic response to historic climate fluctuations. We quantified the European phylogeographic structure of the marine flagellate Oxyrrhis marina and found a marked difference in spatial genetic structure, population demography, and genetic diversity between the northwest Atlantic and Mediterranean Sea that reflects the persistent separation of these regions as well …
Plant colonization of a bare peat surface: population changes and spatial patterns
1992
. Changes in size and spatial arrangement of plant populations established on an initially bare peat surface were described over a period of 5 yr by following plant individuals on a 1-cm grid in an area of 10 m x 25 m. The spatial pattern of populations and association between species was analyzed statistically. The study site was very slowly colonized by 14 perennial plant species. The early successional stage was dominated by Carex rostrata, with a clumped spatial distribution, and the homogeneously distributed Eriophorum vaginatum and Pinus sylvestris. Both the growth in size of populations and changes in their spatial distribution were interpreted as a result of species dispersal abilit…
Dispersal rate and parasitism by Closterocerus chamaeleon (Girault) after its release in Sicily to control Ophelimus maskelli (Ashmead) (Hymenoptera,…
2011
Abstract Spread of the exotic parasitoid Closterocerus chamaeleon (Girault) and its parasitism on the Eucalyptus gall wasp Ophelimus maskelli (Ashmead) (Hymenoptera, Eulophidae) were studied in Sicily after C. chamaeleon introduction in May 2006. Parasitoid spread was evaluated by sampling sites at increasing distances from the five release sites. C. chamaeleon quickly established and spread; within 5 months, it caused 62% parasitism at release sites and 38% parasitism at sites 2 km from release sites. One year after its introduction (spring 2007), C. chamaeleon was detected more than 50 km distant from release sites. By winter 2007–08, the parasitoid was recovered throughout Sicily and in …
Leaps and bounds: geographical and ecological distance constrained the colonisation of the Afrotemperate by Erica.
2018
Abstract Background The coincidence of long distance dispersal (LDD) and biome shift is assumed to be the result of a multifaceted interplay between geographical distance and ecological suitability of source and sink areas. Here, we test the influence of these factors on the dispersal history of the flowering plant genus Erica (Ericaceae) across the Afrotemperate. We quantify similarity of Erica climate niches per biogeographic area using direct observations of species, and test various colonisation scenarios while estimating ancestral areas for the Erica clade using parametric biogeographic model testing. Results We infer that the overall dispersal history of Erica across the Afrotemperate…
Back to Gondwanaland: can ancient vicariance explain (some) Indian Ocean disjunct plant distributions?
2015
Oceans, or other wide expanses of inhospitable environment, interrupt present day distributions of many plant groups. Using molecular dating techniques, generally incorporating fossil evidence, we can estimate when such distributions originated. Numerous dating analyses have recently precipitated a paradigm shift in the general explanations for the phenomenon, away from older geological causes, such as continental drift, in favour of more recent, long-distance dispersal (LDD). For example, the ‘Gondwanan vicariance’ scenario has been dismissed in various studies of Indian Ocean disjunct distributions. We used the gentian tribe Exaceae to reassess this scenario using molecular dating with mi…