Podaxis

Abstract: SUMMARY In twelve experiments known quantities of Lycopodium spores (in five with spores of Podaxis) were liberated into the open air artificially from a point source, under different meteorological conditions, and trapped on ‘Vaseline’-coated slides, placed horizontally at: 2.5, 5.0, 10.0, 15.0, 20.0, 25.0 and 30.0 m. from the source, along from five to thirteen radii (20° apart in some experiments, and 5° or 10° apart in others). The size of spore had little effect on the relative numbers of Lycopodium and Podaxis spores deposited at different distances (the deposition gradient), but from a cloud containing ten times as many Podaxis as Lycopodium spores over twice as many Lycopodium were deposited per unit area as were Podaxis spores. The rate of deposition is thus approximately proportional to the volume of the individual spore. Estimated percentage recovery, within the sampling area, of Lycopodium spores liberated varied from 5.4% (afternoon in wind of 4.4 m./sec.) to 91.6% (night in wind of 0.8 m./sec). Recovery of Podaxis varied from 0.3 % by day to 1.6% by night. The results of these experiments are examined in the light of the statistical theories of W. Schmidt and O. G. Sutton, which formulate atmospheric diffusion by eddies, and are found to be in closer agreement with the latter. The values of the parameters ‘m’ in Sutton's equation agree excellently with his theoretical values, but the values of the parameter ‘C’ are more variable.

Abstract: Identification of Podaxis species to species-level based on morphology alone is problematic. Thus, species of the genus Podaxis are in dire need of taxonomic and phylogenetic evaluations using molecular data to develop a consensus between morphological taxonomy and more robust molecular analyses. In Mexico, most of the collected specimens of Podaxis have been morphologically identified as Podaxis pistillaris sensu lato and are locally used for its culinary value. In this study, the internal transcribed spacer region of Podaxisspecimens from the MEXU fungarium collected between 1948 and 2014 from arid regions of Mexico were sequenced and these collections placed into a molecular phylogenetic framework using Maximum Likelihood analysis. In addition, the ethnomycological use of Podaxis in Mexico (utility, traditional handling, economic importance, etc.) is described by observations, interviews, and sampling of Podaxis species with local people from three areas of the region of the Canada of Oaxaca, which belongs to the Tehuacan-Cuicatlan Biosphere Reserve. These results indicate that the Mexican Podaxis were divided into two clades. Specimens collected in the northern region showed phylogenetic affinities to clade D, while specimens from the south of Mexico clustered within clade E. Morphological data, such as spore length and width, showed significant differences between the two phylogenetic clades, implying that these clades represent different species. None of the Mexican specimens were found in association with termite mounds, which might indicate an adaptation to desert-like regions. This study provides the first ethnomycological use of Podaxis from Mexico.