Ecology and bioreceptivity of basaltic rocks from Xitle volcano in Mexico.

Monogenetic basaltic volcanoes, the most common volcano type on Earth, produce rock surfaces with diverse morphological and textural characteristics promoting wide biodiversity. We assess ecological colonization related to volcanic rock bioreceptivity for biological rock crust communities on Xitle volcano (Mexico City). We assessed the five main volcanic geoforms present: crater, lava tube, promontory, crevasse wall and flat lobe. Climatic conditions (insolation, altitude, humidity, temperature) and biological crust diversity were registered. Thin sections were made for rock physical properties: total porosity, pore size and surface texture. Mineral analysis through microprobe and X-ray diffraction was done. For the rock-life interface, we used optical, petrographic, scanning electron and confocal microscopes. The crust communities contain crustose, foliose, powdery and fruticose lichens; mosses, liverworts, algae, cyanobacteria and bacterial biofilms. The rocks vary significantly in porosity, texture and the community structure. Alpha diversity correlates with porosity, except for the tube being a completely different environment. Beta diversity analysis shows most similarity for flat lobe and promontory (43%). We conclude that rock properties like porosity are important for biodiversity and extrinsic factors like geomorphology have a major role. We introduce bioreceptivity study into natural field sites, broadening bioreceptivity research. We show that it is a useful ecological concept to explore the multiple ecological niches of lava flows and we illustrate the great biodiversity of basaltic volcanoes, and by extension the value of basalt for ecological construction.