TRACKING A MEDICAL MENACE: CLIMATE CHANGE, ECOLOGICAL NICHE MODELING, AND THE BROWN RECLUSE SPIDER (LOXOSCELES RECLUSA)
The brown recluse can cause necrotic lesions of medical concern and is one of the most-feared spiders in North America. However, brown recluse bites are not always easy to diagnose and are sometimes confused with other serious conditions including Lyme disease and various cancers. In addition, the spider’s distributional limitations are poorly understood, and medical professionals routinely diagnose brown recluse bites outside endemic areas. By more fully characterizing its distribution, and by examining potential new areas of distribution, the medical community and the public can be better informed about this species.
ENM is a technique used to elucidate the niche of a species, oftentimes referred to as the set of tolerances and limits in multidimensional space that constrain where a species is potentially able to maintain populations. The ENM framework is built on the correspondence between species occurrences and the associated environmental characteristics from its known range, analyzed via computer algorithms. The resulting ENM can be projected on different spatial (geography) and temporal (e.g., future climates) domains. We used two modelling algorithms (GARP & Maxent) and two future climate change scenarios (a2a & b2a) from the Intergovernmental Panel on Climate Change Third Assessment Report for three time slices (2020, 2050, & 2080) to predict future range shifts by the brown recluse.
Using ENM, we delineate range boundaries and show that under future climate change scenarios the spider’s distribution may expand northward, invading previously unaffected regions of the USA. These results illustrate a significant negative consequence of climate change on humans and will aid medical professionals in proper bite identification/treatment, potentially reducing bite misdiagnoses.