Biogeomorphologic succession dynamics in a Mediterranean river system

Biogeomorphologic succession (i.e. reciprocal adjustments between vegetation and geomorphologic dynamics) of the Mediterranean River Tech, France, was analysed using aerial photographs over a period of sixty years between 1942 and 2000. A spatial analysis of the biogeomorphologic succession was undertaken considering effects of flood regime. Interactions between vegetation dynamics and flood events largely controlled the spontaneous replacement of the dense riparian forest removed in October 1940 during an exceptional high magnitude flood event with a recurrence time >100 yr. In response to this major disturbance event, the fluvial landscape demonstrated a very high resilience emphasizing the existence of a positive feedback driven by pioneer riparian vegetation. The observed feedback corresponded to landform accretion, vegetation succession and to an increase of biogeomorphologic stability under current hydrogeomorphologic and bioclimatic conditions. The evolution of the biogeomorphologic system toward stabilisation appeared to be non‐linear with a threshold occurring thirty years after the exceptional destructive flood event. This threshold materialized a reinforcement of biogeomorphologic cohesive forces driven by vegetation dynamics. This study showed the control of riparian vegetation on the dynamics of Mediterranean fluvial landscapes and pointed to the need to improve our knowledge about biogeomorphologic succession cycles and threshold dynamics within different biogeomorphologic settings.     

Plants intertwine fluvial landform dynamics with ecological succession and natural selection: a niche construction perspective for riparian systems

Aim   To contribute to the development of a macroevolutionary framework for riparian systems, reinforcing conceptual linkages between earth surface processes and biological and ecological processes.
Location   Riparian systems.
Methods   Literature review leading to an original proposition for perceiving the functioning of riparian systems in a new and different way.
Results   Riparian systems provide diverse landforms, habitats and resources for animals and plants. Certain organisms, defined as 'ecosystem engineers', significantly create and modify the physical components of riparian systems. Many studies have highlighted such engineering effects by animals on riparian systems, but the identification and understanding of the effects and responses of plants within fluvial corridors have emerged only recently. The modulation of matter, resources and energy flows by engineering plants helps establish characteristic sequences of fluvial landform creation and maintenance associated with synergetic ecological successions. We relate this process to the concept of niche construction, developed mainly by evolutionary biologists. Feedbacks between adaptive responses of riparian plants to flow regime and adjusting effects on biostabilization and bioconstruction are discussed in the context of niche construction at the scale of ecological succession and the evolution of organisms.
Main conclusions   Our conceptualization forges an integrated approach for understanding vegetated fluvial systems from a macroevolutionary perspective, for elucidating riparian ecosystem dynamics and potentially for establishing long-term stream conservation and restoration strategies.     

Oxime derivatives related to AP18: Agonists and antagonists of the TRPA1 receptor

AP18 1 was recently disclosed as an antagonist of the TRPA1 receptor by the research group of Patapoutian. However, no detailed structure–activity relationships around 1 have been disclosed. Thus, a small number of oximes related to AP18 were examined in order to characterize the determinants of TRPA1 activity. Congeners of AP18 were found to possess both agonist and antagonist activity, suggesting that AP18 may behave as a covalent antagonist of the TRPA1 ion-channel.     

Sex, drugs and mating role: testosterone-induced phenotype-switching in Galapagos marine iguanas

Males of many vertebrate species have flexible reproductivephenotypes and must decide before each mating season whetherto adopt sneaker, satellite, or territorial mating tactics.How do males gauge their abilities against others in the population?We tested experimentally whether hormone–behavior feedbackloops allow Galapagos marine iguana males to activate theirthree behavioral phenotypes as predicted by the relative plasticityhypothesis. Territorial males defended small mating areas andhad significantly higher plasma testosterone (T) levels (75± 11 ng/ml) than did satellite males that roamed aroundterritories (64 ± 8 ng/ml) or sneaker males that behavedlike females within territories (43 ± 11ng/ml). In territorialmales, temporary pharmacological blockade of T slowed head-bobpatrolling, decreased territory size threefold, and reducedthe number of females on territories 20-fold. This supportsprevious data that females may gauge male attractiveness byusing head-bob patrolling, here shown to be a T-dependent trait.Control-treated neighbors reacted to the weakening of T-blockedmales by increasing head-bob rate fivefold and territory size1.6-fold, and female numbers increased 2.5-fold. Unmanipulatedor control-injected males remained unchanged. Behavioral effectswere partly reversed after 7 days. T injections induced satellitemales to establish temporary territories, even at unconventionallocations. Some T-boosted satellite males suffered serious fightinginjuries. T-injected sneakers left female clusters and behavedlike larger satellite males that roam around territories. Thus,territorial and mating tactics are activated by T, but experimental(de-) activation at the wrong ontogenetic stage is costly: manipulatedmales switched phenotype but thereby lowered their access tofemales. We hypothesize that T levels of males that are basedon early-season behavioral interactions influence a males' subsequentphenotypic role.     

The Coolidge effect, individual recognition and selection for distinctive cuticular signatures in a burying beetle

The ability to recognize individuals is an important aspect of social interactions, but it can also be useful to avoid repeated matings with the same individual. The Coolidge effect is the progressive decline in a male's propensity to mate with the same female combined with a heightened sexual interest in new females. Although males that recognize previous partners and show a preference for novel females should have a selective advantage as they can distribute sperm evenly among the females they encounter, there are few invertebrate examples of the Coolidge effect. Here we present evidence for this effect in the burying beetle Nicrophorus vespilloides and examine the mechanism underlying the discrimination between familiar and novel mates. Burying beetles feed and reproduce on vertebrate carcasses, where they regularly encounter conspecifics. Males showed greater sexual interest in novel females (virgin or mated) than in females they had inseminated before. The application of identical cuticular extracts allowed us to experimentally create females with similar odours, and male responses to such females demonstrated that they use female cuticular patterns for discrimination. The chemical analysis of the cuticular profile revealed greater inter-individual variation in female than in male cuticular patterns, which might be due to greater selection on females to signal their individual identity.     

Cuticular hydrocarbons as a basis for chemosensory self‐referencing in crickets: a potentially universal mechanism facilitating polyandry in insects

Females of many species obtain benefits by mating polyandrously, and often prefer novel males over previous mates. However, how do females recognise previous mates, particularly in the face of cognitive constraints? Female crickets appear to have evolved a simple but effective solution: females imbue males with their own cuticular hydrocarbons (CHCs) at mating and utilise chemosensory self‐referencing to recognise recent mates. Female CHC profiles exhibited significant additive genetic variation, demonstrating that genetically unique chemical cues are available to support chemosensory self‐referencing. CHC profiles of males became more similar to those of females after mating, indicating physical transfer of CHCs between individuals during copulation. Experimental perfuming of males with female CHCs resulted in a female aversion to males bearing chemical cues similar to their own. Chemosensory self‐referencing, therefore, could be a widespread mechanism by which females increase the diversity of their mating partners.     

Dreamed movement elicits activation in the sensorimotor cortex

Since the discovery of the close association between rapid eye movement (REM) sleep and dreaming, much effort has been devoted to link physiological signatures of REM sleep to the contents of associated dreams [1-4]. Due to the impossibility of experimentally controlling spontaneous dream activity, however, a direct demonstration of dream contents by neuroimaging methods is lacking. By combining brain imaging with polysomnography and exploiting the state of "lucid dreaming," we show here that a predefined motor task performed during dreaming elicits neuronal activation in the sensorimotor cortex. In lucid dreams, the subject is aware of the dreaming state and capable of performing predefined actions while all standard polysomnographic criteria of REM sleep are fulfilled [5, 6]. Using eye signals as temporal markers, neural activity measured by functional magnetic resonance imaging (fMRI) and near-infrared spectroscopy (NIRS) was related to dreamed hand movements during lucid REM sleep. Though preliminary, we provide first evidence that specific contents of REM-associated dreaming can be visualized by neuroimaging.