Species interactions and the structure of complex communication networks

A universal challenge faced by animal species is the need to communicate effectively against a backdrop of heterospecific signals. It is often assumed that this need results in signal divergence to minimize interference among community members, yet previous support for this idea is mixed, and few studies have tested the opposing hypothesis that interactions among competing species promote widespread convergence in signaling regimes. Using a null model approach to analyze acoustic signaling in 307 species of Amazonian birds, we show that closely related lineages signal together in time and space and that acoustic signals given in temporal or spatial proximity are more similar in design than expected by chance. These results challenge the view that multispecies choruses are structured by temporal, spatial, or acoustic partitioning and instead suggest that social communication between competing species can fundamentally organize signaling assemblages, leading to the opposite pattern of clustering in signals and signaling behavior

Ultrasensitive flow cytometric analyses

New techniques and approaches to cellular analysis being developed at the Los Alamos National Flow Cytometry Resource can be divided into those that improve sensitivity and those that move the technology into new areas by refining existing approaches. An example of the first category is a flow cytometric system capable of measuring the phase shift of fluorescence emitted by fluorophors bound to cells is being assembled. This phase sensitive cytometer is be capable of quantifying fluorescence life time on a cell-by-cell basis as well as using the phase sensitive detection to separate fluorescence emissions that overlap spectrally but have different lifetimes. A Fourier transform flow cytometer capable of measuring the fluorescence emission spectrum of individual labeled cells at rates approaching several hundred per second is also in the new technology category. The current implementation is capable of resolving the visible region of the spectrum into 8 bands. With this instrument, it is possible to resolve the contributions of fluorophors with overlapping emission spectra and to determine the emission spectra of dyes such as calcium concentration indicators that are sensitive to the physiological environment. Flow cytometric techniques have been refined to the point that it is possible to detect individual fluorescent molecules in solution as they flow past a laser beam. This capability has lead to a rapid DNA sequencing project. The goal of the project is to develop a technique that is capable of sequencing long strands of DNA (40,000 kb) at a rate of between 100 and 1,000 bases per second

VERTICAL AND SEASONAL PATTERNS CONTROL BACTERIOPLANKTON COMMUNITIES AT TWO HORIZONTALLY COHERENT COASTAL UPWELLING SITES OFF GALICIA (NW SPAIN)

Analysis of seasonal patterns of marine bacterial community structure along horizontal and vertical spatial scales can help to predict long-term responses to climate change. Several recent studies have shown predictable seasonal reoccurrence of bacterial assemblages. However, only a few have assessed temporal variability over both horizontal and vertical spatial scales. Here we simultaneously studied the bacterial community structure at two different locations and depths in shelf waters of a coastal upwelling system during an annual cycle. The most noticeable biogeographic patterns observed were seasonality, horizontal homogeneity and spatial synchrony in bacterial diversity and community structure related with regional upwelling-downwelling dynamics. Water column mixing eventually disrupted bacterial community structure vertical heterogeneity. Our results are consistent with previous temporal studies of marine bacterioplankton in other temperate regions, and also suggest a marked influence of regional factors on the bacterial communities inhabiting this coastal upwelling system. Bacterial-mediated carbon fluxes in this productive region appear to be mainly controlled by community structure dynamics in surface waters, and local environmental factors at the base of the euphotic zone

VERTICAL AND SEASONAL PATTERNS CONTROL BACTERIOPLANKTON COMMUNITIES AT TWO HORIZONTALLY COHERENT COASTAL UPWELLING SITES OFF GALICIA (NW SPAIN)

Analysis of seasonal patterns of marine bacterial community structure along horizontal and vertical spatial scales can help to predict long-term responses to climate change. Several recent studies have shown predictable seasonal reoccurrence of bacterial assemblages. However, only a few have assessed temporal variability over both horizontal and vertical spatial scales. Here we simultaneously studied the bacterial community structure at two different locations and depths in shelf waters of a coastal upwelling system during an annual cycle. The most noticeable biogeographic patterns observed were seasonality, horizontal homogeneity and spatial synchrony in bacterial diversity and community structure related with regional upwelling-downwelling dynamics. Water column mixing eventually disrupted bacterial community structure vertical heterogeneity. Our results are consistent with previous temporal studies of marine bacterioplankton in other temperate regions, and also suggest a marked influence of regional factors on the bacterial communities inhabiting this coastal upwelling system. Bacterial-mediated carbon fluxes in this productive region appear to be mainly controlled by community structure dynamics in surface waters, and local environmental factors at the base of the euphotic zone