Abstract
Bactrocera dorsalis (Hendel) is the most economically important invasive fruit fly in sub-Saharan Africa, yet long-term evidence linking its seasonal dynamics to environmental drivers across altitudinal gradients remains limited. We analysed 279 site-month observations of male trap catches (flies per trap per day, FTD) collected between October 2004 and February 2012 at six sites spanning 526–1,650 m along the Uluguru Mountain transect in Morogoro, Tanzania. Climatic variables (temperature, rainfall, relative humidity) were obtained from ERA5 reanalysis, and host fruit phenology was characterised for key commercial species. Abundance declined sharply with altitude, with mean FTD decreasing from 87.1 at the lowland site (Sokoine University of Agriculture [SUA], 526 m) to 0.07 at the highest site (Nyandira, 1,650 m), where 55% of months recorded zero catches. Seasonal peaks occurred during the warm–wet period (November–April), but their magnitude and duration declined with altitude, the high season shortening from seven months at SUA to three at Nyandira. Peaks also became less predictable upslope, with the coefficient of variation rising from 0.54 to 1.38. Relative humidity showed the strongest association with FTD (Spearman ρ = 0.202, p = 0.0007), whereas temperature showed no significant overall relationship. Host availability further shaped dynamics, with ripening of jew plum, mango and soursop linked to increased abundance, while citrus and loquat had minimal influence. Overall, variation in B. dorsalis abundance along the gradient was most strongly associated with altitude and host availability, whereas climatic variables showing weaker, context-dependent associations. These findings provide understanding of the factors associated with pest pressure and informing targeted management across heterogeneous East African landscapes.
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- Climate sciences
- Ecology
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The authors are grateful to all field and laboratory personnel who contributed to trap servicing and specimen identification throughout the long-term monitoring period, and to the institutions and programmes that supported the work (see Funding).
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This work was supported by the Belgian Development Cooperation through the Framework Programme with the Royal Museum for Central Africa (Projects F13 and S1_TNZ_IPM); the joint Food and Agriculture Organization/International Atomic Energy Agency (FAO/IAEA) Programme on Nuclear Techniques in Food and Agriculture, through the Coordinated Research Project “Resolution of Cryptic Species Complexes of Tephritid Pests to Overcome Constraints to the Sterile Insect Technique (SIT) Application and International Trade”; the International Foundation for Science (Project C3956); and the Belgian Science Policy (Project MO/37/017).
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This study involved only the trapping of an unregulated invertebrate pest species (B. dorsalis) together with environmental observations and did not involve human participants or vertebrate animals. No approval of a research ethics committee was required to accomplish the goals of this study. All procedures complied with the institutional guidelines and accepted scientific practice in force at the time the work was carried out (2004–2012).
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Mwatawala, M.W., Ruboha, J.O., Bakengesa, J. et al. Unravelling long-term temporal dynamics of the invasive fruit fly Bactrocera dorsalis along an altitudinal gradient in Morogoro, Eastern Tanzania.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-65232-x
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DOI: https://doi.org/10.1038/s41598-026-65232-x
Keywords
Bactrocera dorsalis
- Altitudinal gradient
- Seasonal dynamics
- Host phenology
- Relative humidity
- Tropical agroecosystems
Source: Ecology - nature.com
