Impacts of climate change on high priority fruit fly species in Australia

database of plant pest and pathogen specimens held within herbaria and insect collections across Australia. It is a powerful tool for market access and emergency responses to pest incursion, and supports associated research activities. ALA is Australia’s largest digital database of species occur- rence records, containing information from a wide array of data providers including Australia’s major museums and government departments. GBIF provides similar data at a global scale. Before downloading data from APPD, ALA and GBIF, we applied filters to restrict records to those that were resolved to species-level, were dated no earlier than 1 January 1950, contained valid geo- graphic coordinates, and were not flagged as ‘environmental outliers’. We also collected trap data from various state government departments (Biosecurity and Food Safety, Department of Primary Industries, NSW; Biosecurity Queensland and the Queensland Department of Agriculture and Fisheries; Department of Economic Development, Jobs, Transport and Resources, Victoria; and Department of Primary Industries and Regions South Australia (PIRSA)). Trap data from these sources were collected at different periods from 1996 to 2017. Finally, we also obtained occurrence data from the literature [1–4, 6, 7, 11, 33–37]. Major commercial fruit and vegetable hosts For each of the 11 fruit fly species, we compiled information on the major commercial hosts on which infestation has been recorded. For this purpose, we defined major fruit and vegetable

host species according to the Australian Horticulture Statistics Handbook (HSHB; www. horticulture.com.au) for the year 2016/2017 [32]. This document consolidates horticulture sta- tistics of interest to industry members and other stakeholders. The data contained in HSHB were derived from the Australian Bureau of Statistics, projects funded by Hort Innovation, international trade sources and horticulture industry representative bodies where available. Climate data For baseline and future climate conditions we used the bioclimatic variables available within the WorldClim database (v1.4), at a spatial resolution of 30 arc-seconds [38] (approximately 1 km; http://www.worldclim.org). These data, based on meteorological records for the period 1960–1990, comprise 19 climatic variables, 11 of which are temperature-based while eight relate to precipitation. Combined, the data represent annual trends, seasonality, and limiting or extreme environmental conditions. Assuming that host plants are available, temperature and moisture are the key factors influencing fruit fly reproduction and survival [18, 39]. Thus, these variables were chosen as predictor candidates based on the fruit flies’ biology and eco- logical requirements, and similar habitat suitability studies undertaken on other insects [40]. For each species, we identified a set of ecologically-relevant variables, with minimal collinear- ity, that resulted in high predictive power for the model [41] (described below). When projecting future suitability, we considered a range of climate scenarios to acknowl-

edge this important aspect of uncertainty. CSIRO recommends eight global climate models (GCMs) as being useful for Australian climate impact assessments [42]. Data from six of these models were available from the CCAFS GCM Data Portal (http://www.ccafs-climate.org/data_ spatial_downscaling/), at a spatial resolution of 30 arc seconds. These data were developed from anomalies of the original GCM data that were statistically downscaled using a thin plate spline spatial interpolation, and then applied to the WorldClim v1.4 baseline. The GCMs included: CanESM2 (The Second Generation of Canadian Earth System Model); ACCESS1.0 (The Australian Community Climate and Earth System Simulator); MIROC5 (Model for Interdisciplinary Research on Climate); HadGEM2-CC (Hadley Centre Global Environmental Model Version 2 Carbon Cycle); NorESM1-M (The Norwegian Earth System Model-Part-1); Impacts of climate change on high priority fruit fly species in Australia PLOS ONE | https://doi.org/10.1371/journal.pone.0213820 February 13, 2020 4 / 19