Niche Overlap of Congeneric Invaders Supports a Single-Species Hypothesis and Provides Insight into Future Invasion Risk: Implications for Global Management of the Bactrocera dorsalis Complex

Abstract

BackgroundThe invasive fruit fly, Bactrocera invadens, has expanded its range rapidly over the past 10 years. Here we aimed to determine if the recent range expansion of Bactrocera invadens into southern Africa can be better understood through niche exploration tools, ecological niche models (ENMs), and through incorporating information about Bactrocera dorsalis s.s., a putative conspecific species from Asia. We test for niche overlap of environmental variables between Bactrocera invadens and Bactrocera dorsalis s.s. as well as two other putative conspecific species, Bactrocera philippinensis and B. papayae. We examine overlap and similarity in the geographical expression of each species’ realised niche through reciprocal distribution models between Africa and Asia. We explore different geographical backgrounds, environmental variables and model complexity with multiple and single Bactrocera species hypotheses in an attempt to predict the recent range expansion of B. invadens into northern parts of South Africa.Principal Findings Bactrocera invadens has a high degree of niche overlap with B. dorsalis s.s. (and B. philippinensis and B. papayae). Ecological niche models built for Bactrocera dorsalis s.s. have high transferability to describe the range of B. invadens, and B. invadens is able to project to the core range of B. dorsalis s.s. The ENMs of both Bactrocera dorsalis and B. dorsalis combined with B. philipenesis and B. papayae have significantly higher predictive ability to capture the distribution points in South Africa than for B. invadens alone.Conclusions/SignificanceConsistent with other studies proposing these Bactrocera species as conspecific, niche similarity and overlap between these species is high. Considering these other Bactrocera dorsalis complex species simultaneously better describes the range expansion and invasion potential of B. invadens in South Africa. We suggest that these species should be considered the same–at least functionally–and global quarantine and management strategies applied equally to these Bactrocera species.

Global Potential Distribution of Bactrocera carambolae and the Risks for Fruit Production in Brazil

“…carambolae . A thousand random points from the native and invasive background were added to the PCA analysis (see background selection below), and the first two components were plotted as a biplot, clustering the native and invasive populations with convex hulls to investigate niche overlap within the environmental space [22]. …”

“…MaxEnt is a general-purpose machine learning software that uses presence-only data [23]. It has been widely used to predict species distribution, including tephritid species [4,22] and in addition to its robust statistical properties, MaxEnt shows a high performance across several niche modelling methods for presence-only data [24]. …”

“…First, two sets of variables were selected and then the Pearson’s correlation test performed with the software ENMtools v 1.3 [31] was used to ensure the lack of multicolinearity among the selected predictors [32]. The first set of predictors was selected based on previous studies that successfully modeled the distribution of other Bactrocera species [4,22] and included the following climatic variables: annual mean temperature (Bio1), mean diurnal range (Bio2), maximum temperature of warmest month (Bio5), minimum temperature of coldest month (Bio6), annual precipitation (Bio12), precipitation of wettest (Bio13) and driest month (Bio14). Additionally, a second set of variables was employed by removing the variables Bio5 and Bio6.…”

The progressive invasion of Bactrocera dorsalis (Diptera: Tephritidae) in South Africa

“…Ecological niche and climatic models based on global distribution of B. dorsalis with and without its synonyms (B. invadens, B. philippinensis and B. papayae) have predicted the potential distribution of B. dorsalis further south in South Africa (Hill and Terblanche 2014;Stephens et al 2007) until the southern coastal areas of the Western Cape Province. In the future, B. dorsalis would have to be managed as other fruit fly pests in South Africa using a combination of various techniques such as sanitation, protein baiting and male annihilation ideally on a coordinated area-wide basis (Mau et al 2007;Vargas et al 2014).…”

Guiding farmers' choice for an integrated pest management program against the invasive Bactrocera dorsalis Hendel (Diptera: Tephritidae) in mango orchards in Tanzania

“…True fruit flies (Diptera: Tephritidae) are the most important insects attacking horticultural crops (Hill and Terblanche, 2014;Shelly et al, 2014). Infestation by fruit flies is a major constraint to fruit production (Lux, 1999) as many species are of quarantine importance (Qin et al, 2015).…”