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

Worsley [9] concluded that the current south-eastern range limit lies north of the Queensland- NSW border (~25.5˚ south), while the south-western limit lies at approximately 18˚ south. However, previous analysis suggested that this species’ current climatic range could extend into the cooler temperate areas of southern NSW, and eastern and northern Victoria [4]. Our models partly agree, indicating that suitable conditions along the east coast of Victoria in the baseline period. This species can also withstand very warm conditions, with eggs known to be more heat tolerant than those of the sympatric Qfly, surviving temperatures of 48.2˚C [65]. Given that these species infest many of the same hosts, competition is likely, hence eradication of Qfly may result in the competitive release of B. jarvisi, increasing the threat it poses to horti- culture [4, 65]. Further, as the cultivation of B. jarvisi host plants expands geographically, this species may increase in abundance and extend its range, potentially becoming a major pest in north-western Australia [6, 36]. However, across north-western Australia, and to a lesser extent the far north-east, models for most species were projected onto novel conditions, decreasing confidence in suitability estimates for these regions. In contrast, MESS maps dem- onstrated that extrapolation rarely occurred across eastern and southern regions, although novel interactions between climate variables cannot be ruled out. While widespread throughout Queensland, Z. cucumis currently has a restricted distribu-

tion in the Northern Territory, although there is a disputed single record from northern West- ern Australia [66]. Both Fitt [67] and the Horticultural Policy Council [4] reported that if the cucurbit industry expands in the Northern Territory, the pest status of Z. cucumis may increase. However, while the species has been trapped frequently in the Northern Territory, it has not been found on cucurbits growing in this region [6]. In NSW, Z. cucumis appears to be currently limited to regions close to the Queensland border, with rare detection as far south as Sydney [66]. It has not been detected in the (former) Fruit Fly Exclusion Zone in southern NSW [37]. Our model also estimates the southern limit of suitable climate for this species to be around Sydney. However, with climate change this may extend further southward, with parts Table 2. Percentage (%) of Australia projected to be suitable for the 11 fruit fly species considered in this study, under baseline (1960–1990) and future climates. Suitable area (% of Australia) Count Baseline (Novel masked) 2030 2050 2070 0 68.4% (68.5%) 67.5% (70.2%) 59.5% (73.6%) 47.0% (72.0%) 1 11.0% (11.1%) 9.6% (9.4%) 11.6% (9.6%) 14.6% (10.0%) 2 11.1% (11.0%) 10.5% (9.7%) 14.8% (8.8%) 17.5% (10.3%) 3 2.3% (2.3%) 3.4% (4.1%) 3.0% (3.0%) 6.5% (3.4%) 4 1.2% (1.2%) 1.9% (2.2%) 3.2% (1.6%) 4.8% (1.2%) 5 1.6% (1.8%) 2.6% (2.8%) 2.9% (1.9%) 3.9% (1.6%) 6 1.2% (1.5%) 1.9% (0.8%) 1.8% (0.6%) 2.3% (0.7%) 7 1.3% (1.3%) 0.6% (0.4%) 1.0% (0.5%) 1.2% (0.5%) 8 0.4% (0.7%) 0.4% (0.2%) 0.5% (0.2%) 0.6% (0.1%)

9 0.8% (0.3%) 1.3% (0.2%) 1.4% (0.1%) 1.4% (0.1%) 10 0.6% (0.4%) 0.3% (0.1%) 0.1% (0.1%) 0.1% (0.1%) 11 0.0% (1.3E-05%) 0.1% (0.0%) 0.1% (0.0%) 0.1% (0.0%) This is a summary of the ‘consensus’ maps for each species. Values in brackets represent results when novel environments have been excluded. Each row of the table indicates the percentage of Australia projected to be suitable in the baseline period (1960–1990), in 2030, 2050, and 2070, for n species, where n is given in the “Count” column. Thus, the first row (with Count = 0) gives the area projected to be unsuitable for all 11 species under four or more of the climate scenarios, the row with Count = 1 gives the area projected to be suitable for any one of the 11 species in at least four of the climate scenarios, and the row with Count = 11 gives the area projected to be suitable for all 11 species in at least four of the climate scenarios. Note that the number of 1 km2 grid cells spanning Australia is 7,667,790. https://doi.org/10.1371/journal.pone.0213820.t002 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 13 / 19