Murphy, S. J. | Search bioRxiv

bioRxiv2021

Imprecisely georeferenced specimen data provide unique information on species' distributions and environmental tolerances: Don't let the perfect be the enemy of the good

AimMuseum and herbarium specimen records are frequently used to assess species conservation status and responses to climate change. Typically, occurrences with imprecise geolocality information are discarded because they cannot be matched confidently to environmental conditions, and are thus expected to increase uncertainty in downstream analyses. However, using only precisely georeferenced records risks undersampling of species environmental and geographic distributions. We present two related methods to allow the use of imprecisely georeferenced occurrences in biogeographic analysis. InnovationOur two procedures assign imprecise records to the 1) locations or 2) climates that are closest to the geographic or environmental centroid of the precise records of a species. For virtual species, including imprecise records alongside precise records improved the accuracy of ecological niche models projected to the present and the future, especially for species with ~20 or fewer precise occurrences. Using only precise records underestimates loss in suitable habitat and overestimates the amount of suitable habitat in both the present and future. Including imprecise records also improves estimates of niche breadth and extent of occurrence. An analysis of 44 species of North American Asclepias (Apocynaceae) yielded similar results. Main conclusionsExisting studies examining the effects of spatial imprecision compare outcomes based on precise records to the same records with spatial error added to them. However, in real-world cases, analysts possess a mix of precise and imprecise records and must decide whether to retain or discard the latter. Discarding imprecise records can undersample species geographic and environmental distributions and lead to mis-estimation of responses to past and future climate change. Our method, for which we provide a software implementation in the enmSdmX package for R, is simple to employ and can help leverage the large number of specimen records that are typically deemed "unusable" because of spatial imprecision in their geolocation.

ecology↗

bioRxiv2020

A novel juxtamembrane basolateral targeting motif regulates TGF-β receptor signaling in Drosophila

In polarized epithelial cells, receptor-ligand interactions can be restricted by different spatial distributions of the two interacting components, giving rise to an underappreciated layer of regulatory complexity. We explored whether such regulation occurs in the Drosophila wing disc, an epithelial tissue that requires the TGF-{beta} family member Dpp for growth and patterning. Dpp protein has been observed in a gradient within the columnar cells of the disc, but also uniformly in the disc lumen, leading to the question of how graded signaling is achieved in the face of two distinctly localized pools. We find the Dpp type II receptor Punt, but not the type I receptor Tkv, is enriched at the basolateral membrane, and depleted at the junctions and apical surface. Wit, a second type II receptor, shows a markedly different behavior, with the protein detected on all membrane regions but enriched at the apical side. Mutational studies identified the BLT, a short juxtamembrane sequence required for basolateral targeting of Punt in both wing discs and mammalian MDCK cells, and that dominantly confers basolateral localization on an otherwise apical receptor. Rescue of punt mutants with transgenes altered in the targeting motif showed that flies expressing apicalized Punt due to the lack of a functional BLT displayed developmental defects, female sterility and significant lethality. We also show that apicalized Punt does not produce an ectopic signal, indicating that the apical pool of Dpp is not a significant signaling source even when presented with Punt. Finally, we present evidence that the BLT acts through polarized sorting machinery that differs between types of epithelia. This suggests a code whereby each epithelial cell type may differentially traffic common receptors to enable distinctive responses to spatially localized pools of extracellular ligands.

cell biology↗