Primary productivity and species richness: relationships among functional guilds, residency groups and vagility classes at multiple spatial scales

One of the major determinants of species richness is the amount of energy available, often measured as primary productivity. Heterogeneity of environmental variables has also been found to influence species richness. Predicting species distributions across landscapes and identifying areas that have high species richness, or vulnerable groups of species, is useful for land management. Remotely sensed data may help identify such areas, with the Normalized Difference Vegetation Index (NDVI) providing an estimate of primary productivity. We examined the relationship between maximum productivity (NDVI), heterogeneity of productivity, and species richness of birds and butterflies at multiple spatial scales. We also explored relationships between productivity, functional guilds and residency groups of birds, and vagility classes of butterflies. Positive linear relationships between maximum NDVI and number of functional guilds of birds were found at two spatial scales. We also found positive linear relationships between maximum NDVI and species richness of neotropical migrant birds at two scales. Heterogeneity of NDVI, by contrast, was negatively associated with number of functional guilds of birds and species richness of resident birds. Maximum NDVI was associated with species richness of all butterflies and of the most vagile butterflies. No association was found between heterogeneity of NDVI and species richness of butterflies. In the Great Basin, where high greenness and availability of water correspond to areas of high species richness and maximum NDVI, our results suggest that NDVI can provide a reliable basis for stratifying surveys of biodiversity, by highlighting areas of potentially high biodiversity across large areas. Measures of heterogeneity of NDVI appear to be less useful in explaining species richness.     

Effects of chorda tympani nerve anesthesia on taste responses in the NST

Human clinical and psychophysical observations suggest that the taste system is able to compensate for losses in peripheral nerve input, since patients do not commonly report decrements in whole mouth taste following chorda tympani nerve damage or anesthesia. Indeed, neurophysiological data from the rat nucleus of the solitary tract (NST) suggests that a release of inhibition (disinhibition) may occur centrally following chorda tympani nerve anesthesia. Our purpose was to study this possibility further. We recorded from 59 multi- and single- unit taste-responsive sites in the rat NST before, during and after recovery from chorda tympani nerve anesthesia. During anesthesia, average anterior tongue responses were eliminated but no compensatory increases in palatal or posterior tongue responses were observed. However, six individual sites displayed increased taste responsiveness during anesthesia. The average increase was 32.9%. Therefore, disinhibition of taste responses was observed, but infrequently and to a small degree in the NST At a subset of sites, chorda tympani-mediated responses decreased while greater superficial petrosal-mediated responses remained the same during anesthesia. Since this effect was accompanied by a decrease in spontaneous activity, we propose that taste compensation may result in part by a change in signal-to-noise ratio at a subset of sites.