Time filter

Source Type

Hessler I.,University of Bremen | Dupont L.,University of Bremen | Bonnefille R.,Aix - Marseille University | Behling H.,University of Gottingen | And 9 more authors.
Quaternary Science Reviews | Year: 2010

To reconstruct the response of vegetation to abrupt climate changes during the last glacial we have compiled pollen records from the circum-Atlantic tropics between 23°N and 23°S from both marine and terrestrial sediment cores. Pollen data were grouped into mega-biomes to facilitate the comparison between the different records. Most tropical African records do not appear to register Dansgaard-Oeschger (D-O) variability, although there are vegetation changes during Heinrich Stadials (HS). There is a stronger signal of D-O and HS variability in the South American records. Records close to the modern northern and southern limits of the Intertropical Convergence Zone (ITCZ) show opposite trends in vegetation development during HS and D-O cycles. The pollen data from tropical South America corroborate the hypothesis of a southward shift in the migration pattern of the ITCZ and a reduction in the Atlantic Meridional Overturning Circulation (AMOC) during HS. © 2009 Elsevier Ltd.

Penalver E.,Instituto Geologico Y Minero Of Espana | Gaudant J.,CNRS Laboratory of Functional Biology, Insects and Interactions
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2010

In an attempt to arrive at a preliminary reconstruction of the limnic food web of the Upper Miocene Bicorb Basin (Eastern Spain), and to obtain new palaeontological information regarding the salinity of its palaeolake, studies were made of the fossil assemblages of aquatic organisms in the outcrops of facies associations 2 and 3 (subunit b of the upper unit, established in 1998 by Anadón et al.) These outcrops (known as Venus, Cantera and Bicorb Insectos-1 and -3) are typical Konservat-Lagerstätten. We here describe four specimens of a new species of the cyprinodontid genus Aphanius (A. bicorbensis sp. nov.) plus several chironomid insects and coprolites, mainly from the Venus outcrop. Two morphotypes of chironomid pupal exuviae were found, both of which were attributed to the subfamily Chironominae. The larger morphotype was attributed to Chironomus sp. (tribe Chironomini) and the smaller to Tanytarsini gen. et sp. indet. Coprolites were separated into two types - C1 and C2 - based on their contents, i.e., the remains of chironomids or miliolid foraminifers respectively. The miliolid foraminifers belonged to the family Hauerinidae, possibly to the genus Quinqueloculina. It is concluded that Aphanius fish were second level consumers, feeding on chironomids and miliolid foraminifers. Primary producers were mainly represented by the aquatic plant Potamogeton, Botryococcus green algae, and microbial mats (almost certainly photosynthetic). This notably simple limnic food web and this aquatic fossil assemblage suggest that the Bicorb palaeolake was saline or brackish; the living taxa related to this assemblage are notably tolerant of high salinity. This salinity is related to the presence of a Triassic diapir on the southern side of the Bicorb Basin. In addition, non-bioturbated, finely laminated calcareous mudstones and exceptionally well-preserved delicate insects indicate the lake water to have shown a halocline (leading to meromictic episodes), with the development of microbial mats at the lake bottom. © 2010 Elsevier B.V.

Vignon M.,CNRS Host-Pathogen-Environment Interactions Laboratory | Vignon M.,CNRS Insular Research Center and Environment Observatory | Vignon M.,French National Institute for Agricultural Research | Pariselle A.,CNRS Laboratory of Functional Biology, Insects and Interactions | And 2 more authors.
Biological Journal of the Linnean Society | Year: 2011

Cichlidogyrus spp. (Monogenea, Ancyrocephalidae) are common parasites of cichlid fishes from Africa and the Levant. They display important morphological variation in their attachment apparatus and infect a broad host spectrum throughout a wide geographic range. Thus, they offer an interesting model to investigate to what extent the phenotypic variability of the attachment organ among congeners is related to host specificity, geographic/environmental components, or phylogeny. A geometric morphometric approach was carried out to analyse the shape variation of sclerotized structures of the attachment organ within 66 African species of the genus Cichlidogyrus. The interspecific shape comparison supports the presence of three main morphological configurations, each consisting of a given combination of particular sclerite shapes. Moreover, data emphasize strong coordination and integration (shape co-variation) among the different sclerites jointly forming the attachment organ. Although attachment apparatuses are usually considered to be the result of adaptive processes and must be adapted to the hosts and local environmental conditions, we found no relationship between these clusters and host specificity or geographical distribution. Nevertheless, groups are partially congruent with those obtained with the molecular phylogeny of a subset of species, suggesting a phylogenetic constraint rather than an adaptation to either hosts or environment. Because of the necessity to form a functional entity, modularity within attachment organ imposes important evolutionary constraint. This provides new insights into the evolvability of attachment organs, as well as into the morphological basis of host specificity and host-parasite co-evolutionary interaction in helminth parasites. © 2011 The Linnean Society of London.

The revision of Prolebias stenoura Sauvage, 1874, the type species of the genus Prolebias Sauvage, 1874, a cyprinodontid fish from the Upper Stampian (= Rupelian) (Oligocene) of the surroundings of Corent (Limagne, central France), has made possible the preparation of a detailed anatomical study and of an emended diagnosis. The occurrence of coccolithophorids and of dinoflagellates has determined several authors to suggest an incursion of marine waters into this basin during the Stampian. However, the fact that all the species of the genus Prolebias hitherto known by articulated skeletons have been living in fresh and brackish waters is, on the contrary, more in agreement with the hypothesis of a shallow meromictic lake, the superficial part of which was filled by seasonal rains, suitable for the life of this species. © Publications Scientifiques du Muséum national d'Histoire naturelle, Paris.

Mone Y.,CNRS Biometry and Evolutionary Biology Laboratory | Mone Y.,CNRS Laboratory of Functional Biology, Insects and Interactions | Monnin D.,CNRS Biometry and Evolutionary Biology Laboratory | Kremer N.,CNRS Biometry and Evolutionary Biology Laboratory | Kremer N.,University of Wisconsin - Madison
Proceedings of the Royal Society B: Biological Sciences | Year: 2014

Symbiotic interactions are ubiquitous in nature and play a major role in driving the evolution of life. Interactions between partners are oftenmediated by shared signalling pathways, which strongly influence both partners' biology and the evolution of the association in various environments. As an example of 'common language', the regulation of the oxidative environment plays an important role in driving the evolution of symbiotic associations. Such processes have been occurring for billions of years, including the increase in Earth's atmospheric oxygen and the subsequent evolution of mitochondria. The effect of reactive oxygen species and reactive nitrogen species (RONS) has been characterized functionally, but the molecular dialogue between partners has not been integrated within a broader evolutionary context yet. Given the pleiotropic role of RONS in cell-cell communication, development and immunity, but also their associatedphysiological costs,we discuss here howtheir regulation can influence the establishment, the maintenance and the breakdown of various symbiotic associations. By synthesizing recent developments in redox biology, we aim to provide an interdisciplinary understanding of the influence of such mediators of interspecies communication on the evolution and stability of symbioses, which in turn can shape ecosystems and play a role in health and disease. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Discover hidden collaborations