Abstract
In 2003, a new fruit fly pest species was recorded for the first time in Kenya and has subsequently been found in 28 countries across tropical Africa. The insect was described as Bactrocera invadens, due to its rapid invasion of the African continent. In this study, the morphometry and DNA Barcoding of different populations of B. invadens distributed across the species range of tropical Africa and a sample from the pest's putative aboriginal home of Sri Lanka was investigated. Morphometry using wing veins and tibia length was used to separate B. invadens populations from other closely related Bactrocera species. The Principal component analysis yielded 15 components which correspond to the 15 morphometric measurements. The first two principal axes contributed to 90.7% of the total variance and showed partial separation of these populations. Canonical discriminant analysis indicated that only the first five canonical variates were statistically significant. The first two canonical variates contributed a total of 80.9% of the total variance clustering B. invadens with other members of the B. dorsalis complex while distinctly separating B. correcta, B. cucurbitae, B. oleae and B. zonata. The largest Mahalanobis squared distance (D2 = 122.9) was found to be between B. cucurbitae and B. zonata, while the lowest was observed between B. invadens populations against B. kandiensis (8.1) and against B. dorsalis s.s (11.4). Evolutionary history inferred by the Neighbor-Joining method clustered the Bactrocera species populations into four clusters. First cluster consisted of the B. dorsalis complex (B. invadens, B. kandiensis and B. dorsalis s. s.), branching from the same node while the second group was paraphyletic clades of B. correcta and B. zonata. The last two are monophyletic clades, consisting of B. cucurbitae and B. oleae, respectively. Principal component analysis using the genetic distances confirmed the clustering inferred by the NJ tree.
Highlights
Dacine fruit flies of the genus Bactrocera Macquart (Diptera: Tephrtitidae) are among the most important pests of fruits and vegetables [1]
Bactrocera invadens populations and the other Bactrocera species belonging to the B. dorsalis complex could not be separated by principal coordinate analysis (PCA) (Figure 1)
Our results showed that B. invadens can be morphometrically separated from other Bactrocera species (B. correcta, B. cucurbitae, B. oleae and B. zonata) used in this study with respect to wing morphology and the tibia length
Summary
Dacine fruit flies of the genus Bactrocera Macquart (Diptera: Tephrtitidae) are among the most important pests of fruits and vegetables [1]. In addition to the polyphagous nature of some species, several are considered highly invasive; aided by globalization of trade and poor quarantine infrastructure in the developing countries. Bactrocera invadens is an emerging polyphagous fruit fly pest and in Africa it has been reported to attack over 43 fruit species from 23 families with mango being one of the most preferred cultivated host [10,12,13,14]. Direct damage to mango due to B. invadens has been reported to range from 30–80% depending on the cultivar, locality and season [8,12,15]. The direct and indirect damage continue to have wide reaching socio-economic implications for millions of rural and urban populations involved in the mango value chain across Africa. The pest has been described as ‘‘a devastating quarantine pest’’ by the Inter-African Phytosanitary Council [6]
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