Detecting Disease from Skin Swabs
Chytrid (Batrachochytrium dendrobatidis) is a fungal disease causing amphibian die offs around the world (we wrote about it here). Given its wide distribution both on hosts and geographically, there’s no surprise that there is genomic variation. Scientists are interested in this variation to understand virulence, host specificity, and patterns of geographic spread between different strains. But obtaining chytrid DNA requires laborious sterile culture and sometimes requires sacrificing animals to obtain enough fungus to grow in the lab. This paper (sub) reports a genotyping array that detects variation within and between the major clades of chytrid genome. This array has the power to genotype samples from very small amounts of DNA, such as those on swabs of amphibian skin. There may be > 100,000 of these swabs collected by researchers on different species, across space and time. Thus, if they were genotyped on this array, they would make a powerful dataset to understand chytrid.
Side photo of an amphibian being swabbed for chytrid by Stefan Lotters via ARKive.
Following the introduction of maize into Europe and Asia, two species of moth (European and Asian corn borers; Ostrinia nubilalis and furnacalis, respectively) shifted from dicot hosts onto the introduced monocot. They are closely related to the adzuki bean borer (O. scapulalis). Each moth feeds on their host plant and can result in large crop yields. Mechanical harvest of maize cuts the tops off of the crop, and has been encouraged as a way to kill off corn borer. Over time farmers noticed that borers appeared further down the stem, below the harvest line, suggesting a selected behavior that allowed them to survive corn harvest. This paper (open) compared vertical movement of European and Asian corn borers to adzuki bean borers (where the harvest is not based on plant height). The researchers made artificial corn stalks in growth chambers in the lab, then placed larvae on them. They measured the proportion of larvae at different heights during their development, and saw that the corn borers began moving down the stalk as they got closer to diapause where the adzuki bean borers remained higher on the artificial stalks. Thus the researchers show parallel adaptation due to a human induced selection pressure.