Research Technical Report

Disease Driven Changes In The Realized Niche Of An Apex Predator

Hamilton, S.L., S.A. Gravem, V.R. Saccomanno, W.N. Heady, A.M. Gehman, S.I. Lonhart, R. Beas-Luna, A.K. Salomon, and L. Rogers-Bennett (November 2020)

Oral presentation at the Western Society of Naturalists Annual Meeting, November 5-8, 2020, Virtual Meeting

ABSTRACT

The Sunflower Star, Pycnopodia helianthoides, was catastrophically affected by the massive outbreak of sea star wasting syndrome (SSWS) in the mid-2010s. While Pycnopodia populations were drastically reduced across their entire range, some populations were impacted less by the disease. Previous studies suggest that local environmental conditions, specifically temperature, influenced the severity of the outbreak. Where are the remaining populations of Pycnopodia and what habitats are associated with persistence of Pycnopodia populations post-outbreak? To answer these questions, we combined 30+ datasets spanning Pycnopodia’s range with species distribution modelling to characterize changes in the species’ realized niche before and after the outbreak of SSWS. Early results indicate that prior to the outbreak, Pycnopodia’s realized niche was most strongly characterized by depths of less than 200m, high salinity water, and a range of water temperatures between 6-14 °C. After the outbreak, Pycnopodia’s niche narrowed and shifted towards cooler (5-11°C) and shallower (‹100m) populations. Salinity became a weaker predictor of their realized niche and conversely the percent contribution of temperature in predicting the realized niche jumped from 32% to 60%. Four to seven years since these outbreaks first emerged, the realized niche of Pycnopodia is now more strongly characterized by temperature, which could reflect interactions between the disease-causing agent and temperature. Whether these changes are more permanent or dynamic remains to be seen.