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Project Progress

Evolution in Microbe-based Ecosystems (dm)

Last year we made progress by initiating studies at our field study sites in Cuatro Cienegas, central Mexico. We worked with our UNAM collaborators to obtain full scientific permitting for project work in Mexico. During a 10-day expedition in December 2000, we completed field site reconnaissance and sampling and continued ongoing genetic studies of fish populations across environmental gradients started the previous year with seed funding from ASU. This was followed-up with a longer expedition in March 2001 in which several additional project components were initiated. Sampling sites for a chosen headwater-terminal basin flow path (Churince) were established. Two 2×2 nutrient enrichment (nitrogen, phosphorus fertilization) experiments were performed at Laguna Intermedia (Churince system) to compare a diatom-dominated mat system to one dominated by cyanobacteria. The experiment involved the laboratory incubation of isolated mat samples under natural illumination.

Fifty-five localities within five separate drainage systems were sampled for analysis of diversity of archaea and bacteria using molecular techniques. Many of these have been successfully isolated using selective media and brought into culture and frozen for detailed genetic analysis. Population genetic studies have been initiated for widespread taxa across important environmental gradients. For studies of stromatolitic phototrophs at Cuatro Cienegas, we have carried out extensive sampling in the field area and succesfully developed methodologies for efficient nucleic acid extraction from encrusted/calcified microbial communities. Characterization of phototrophic components of stromatolite billding microbial communities using molecular techniques is underway, and morphogenesis studies have been initiated. We thin-sectioned fixed oncolite samples and started basic paleontological, mineralogical and microfabric studies of those and previously collected samples.

Population genetic studies of pupfish (Cyrpinodon) across environmental extremes were continued. Cyprinodon specimens were collected from throughout the basin, providing necessary perspective for examination of horizontal gene transfer between C. atrorus and C. bifasciatus. Temporal sampling of physicochemical data and Cyprinodon within areas of hybridization was initiated. We developed morphological, systematic, and molecular protocols to analyze the evolution and ecology of Hydrobiid snails from Cuatro Cienegas. All physicochemical measurements and Cyprinodon samples are currently being prepared for analysis. A database has been set up to integrate data on landmark morphometric analyses, relationships to environmental factors (i.e., temperature, pH, salinity), and existing molecular DNA analyses. Our project also involves modeling of food-web evolution. We have completed formulating the architecture of our model for ecological communities evolving under stoichiometric constraints, which we will use to compare to empirical observations of the living systems under study. We have nearly completed the mathematical derivation of mass conservation equations and are also nearing completion of encoding the model into C++.