Search results for "COLON"
showing 10 items of 2038 documents
Dual colonization of the Palaearctic from different regions in the Afrotropics bySenecio
2016
Aim Investigation of the geographical origin of Senecio and the colonization of the Palaearctic including the relationship of life-history strategy and elevational distribution in the source area and the colonized area. Location Worldwide with a focus on the Afrotropic and the Palaearctic. Methods Sampling focused on adding species from the Afrotropic to existing datasets of Senecio. Two nuclear markers and three chloroplast markers were amplified and sequenced. Maximum likelihood and Bayesian inference were used to infer phylogeny, divergence times, biogeographical history and life-history strategy evolution. Results Senecio originated most likely during the Mid to Late Miocene in western …
Life history evolution in social insects: a female perspective
2016
Social insects are known for their unusual life histories with fecund, long-lived queens and sterile, short-lived workers. We review ultimate factors underlying variation in life history strategies in female social insects, whose social life reshapes common trade-offs, such as the one between fecundity and longevity. Interspecific life history variation is associated with colony size, mediated by changes in division of labour and extrinsic mortality. In addition to the ratio of juvenile to adult mortality, social factors such as queen number influence life history trajectories. We discuss two hypotheses explaining why queen fecundity and lifespan is higher in single-queen societies and sugg…
Pleistocene diversification in Morocco and recent demographic expansion in the Mediterranean pond turtle Mauremys leprosa
2016
Quaternary climatic oscillations and geographic barriers have strongly influenced the distribution and diversification of thermophilic species occurring in the Mediterranean Basin. The Western Mediterranean pond turtle, Mauremys leprosa, is widely distributed throughout the Iberian Peninsula, southern France and most of the Maghreb region, with two subspecies currently recognized. In this work, we used 566 samples, including 259 new individuals, across the species range, and sequenced two mitochondrial markers (cytochrome b gene and control region; 163 samples in a concatenated mtDNA dataset) and one nuclear intron (R35; 23 samples representing all identified sublineages) to study the evolu…
The loss of dispersal on islands hypothesis revisited: Implementing phylogeography to investigate evolution of dispersal traits in Periploca (Apocyna…
2017
Aim: The loss of dispersal on islands hypothesis (LDIH) posits that wind-dispersed plants should exhibit reduced dispersal potential, particularly if island populations are old. In this study, we tested this hypothesis using a detailed phylogeographical framework across different geographical scales. Location: Mainland and island areas of the Atlantic and Mediterranean regions, including Macaronesia (Canary Islands and Cape Verde) and Mediterranean islands in the strait of Sicily. Methods: Forty-five populations of Periploca laevigata, a wind-dispersed shrub, were sampled. Plastid and nuclear microsatellite data were used to reconstruct spatio-temporal patterns of island colonization, and e…
Private information alone can trigger trapping of ant colonies in local feeding optima.
2015
Ant colonies are famous for using trail pheromones to make collective decisions. Trail pheromone systems are characterised by positive feedback, which results in rapid collective decision making. However, in an iconic experiment, ants were shown to become 'trapped' in exploiting a poor food source, if it was discovered earlier. This has conventionally been explained by the established pheromone trail becoming too strong for new trails to compete. However, many social insects have a well-developed memory, and private information often overrules conflicting social information. Thus, route memory could also explain this collective 'trapping' effect. Here, we disentangled the effects of social …
Plant growth promotion, metabolite production and metal tolerance of dark septate endophytes isolated from metal-polluted poplar phytomanagement sites
2016
Numerous studies address the distribution and the diversity of dark septate endophytes (DSEs) in the literature, but little is known about their ecological role and their effect on host plants, especially in metal-polluted soils. Seven DSE strains belonging to Cadophora, Leptodontidium, Phialophora and Phialocephala were isolated from roots of poplar trees from metal-polluted sites. All strains developed on a wide range of carbohydrates, including cell-wall-related compounds. The strains evenly colonized birch, eucalyptus and ryegrass roots in re-synthesis experiments. Root and shoot growth promotion was observed and was both plant and strain dependent. Two Phialophora and Leptodontidium st…
Getting there and around: Host range oscillations during colonization of the Canary Islands by the parasitic nematode Spauligodon
2016
Episodes of expansion and isolation in geographic range over space and time, during which parasites have the opportunity to expand their host range, are linked to the development of host-parasite mosaic assemblages and parasite diversification. In this study, we investigated whether island colonization events lead to host range oscillations in a taxon of host-specific parasitic nematodes of the genus Spauligodon in the Canary Islands. We further investigated whether range oscillations also resulted in shifts in host breadth (i.e., specialization), as expected for parasites on islands. Parasite phylogeny and divergence time estimates were inferred from molecular data with Bayesian methods. H…
Colonization of Plant Roots by Pseudomonads and AM Fungi: A Dynamic Phenomenon, Affecting Plant Growth and Health
2008
Because of their enormously large range of plant hosts and role in plant nutrition, arbuscular mycorrhizal (AM) fungi represent an extraordinarily fascinating field of study. Plant growth promotion effects by AM fungi were described as early as 1900 (Sthal 1900) and several data obtained in the second half of the last century support the idea that these microrganisms can act as biocontrol agents (BCA). The extent of root colonization is variable in different plants and under different environmental conditions (Giovannetti and Hepper 1985). Some effects of AM colonization on plants have been reported to be dependent on the degree of root colonization, while others have not. Root exudation an…
Rapid range extension of the Ponto-Caspian amphipod Dikerogammarus villosus in France: potential consequences
2004
Non-indigenous species are increasingly recognized as altering local com- munities in newly colonized areas. In some north European freshwater systems, the Ponto-Caspian invasive crustacean Dikerogammarus villosus (Amphipoda) is im- plicated to have such an effect, with general monitoring of its progress and general im- pact required. The present study contributes to this monitoring. D. villosus was ob- served in 2003 in all the major French rivers prospected (i.e. Rhine, Meuse, Moselle, Sao ne, Rho ne, Seine, and Loire), a European region previously overlooked for its co- lonization. This species was also detected in some tributaries of the rivers Sao ne and Seine, and in Geneva Lake. The …
Evolution of leaf anatomy in arid environments – A case study in southern African Tetraena and Roepera (Zygophyllaceae)
2015
The dry biomes of southern Africa (Desert, Nama Karoo and Succulent Karoo) are home to a rich and diverse xerophytic flora. This flora includes two morphologically diverse clades of Zygophyllaceae, Tetraena and Roepera (Zygophylloideae), which inhabit some of the most arid habitats in the region. Using a plastid phylogeny of Zygophylloideae we assess whether the evolution of putatively adaptive traits (leaf shape, vasculature, mode of water storage and photosynthetic type: C3 versus C4) coincides with the successful colonisation of environments with different drought regimes within southern Africa. Our results show general niche conservatism within arid habitats in Tetraena, but niche shift…