Affect of trembling aspen (Populus tremuloides) diversity on the abundance and fate of aspen blotch miners (Lithocolletis salicifoliella) Cham. (Lepidoptera: Gracillariidae).

The purpose of this experiment is to increase current knowledge of the relationship between Lithocolettis salicifoliella and Populus tremuloides, specifically focusing on diversity of aspen stands and how this affects the abundance, fate and cause of death of the blotch miners. We selected two stands of aspen trees, a monoculture and a polyculture, that were equidistant from a red pine plantation. We counted the numbers of trees and trembling aspens, and gathered leaves to observe the blotch miners in the lab. We determined the fate and cause of death of each miner that we gathered, and the average area of the leaves within each stand. We found significant difference for cause of death between the two stands and the abundace of blotch miners between the two stands. Trembling aspen within a monoculture have a greater chance of being infested by miners than those in a polyculture because of the protection that the polyculture provides. The monoculture had a greater chance of being infested by parasites and less of a chance of being preyed upon than the polyculture. Parasitism is higher in plants with chemical and physical alterations, and the monoculture has less protection from damage due to less vegetation. Predation may be higher in the polyculture because plant predators live in the surrounding vegetation, encountering the aspen trees in the polyculture first.http://deepblue.lib.umich.edu/bitstream/2027.42/54540/1/2979.pdfDescription of 2979.pdf : Access restricted to on-site users at the U-M Biological Station

Specification of the mammalian cochlea is dependent on Sonic hedgehog

Organization of the inner ear into auditory and vestibular components is dependent on localized patterns of gene expression within the otic vesicle. Surrounding tissues are known to influence compartmentalization of the otic vesicle, yet the participating signals remain unclear. This study identifies Sonic hedgehog (Shh) secreted by the notochord and/or floor plate as a primary regulator of auditory cell fates within the mouse inner ear. Whereas otic induction proceeds normally in Shh(−/−) embryos, morphogenesis of the inner ear is greatly perturbed by midgestation. Ventral otic derivatives including the cochlear duct and cochleovestibular ganglia failed to develop in the absence of Shh. The origin of the inner ear defects in Shh(−/−) embryos could be traced back to alterations in the expression of a number of genes involved in cell fate specification including Pax2, Otx1, Otx2, Tbx1, and Ngn1. We further show that several of these genes are targets of Shh signaling given their ectopic activation in transgenic mice that misexpress Shh in the inner ear. Taken together, our data support a model whereby auditory cell fates in the otic vesicle are established by the direct action of Shh