Abstract:

Phytophagous Fruit flies (Diptera: Tephritidae) cause heavy losses on fruits and vegetable crops,
and pose a threat to the commercialisation of the horticulture industry in Uganda. In order to
develop an effective management strategy against fruit flies, it is important to understand the
diversity, patterns of host utilization and ecological niche of the major fruit species, which were
the objectives of this study. Major differences in species richness and community structure
occurred among the three major mango growing regions. The alien Bactrocera invadens was
noted to be displacing native fruit fly species. Similarly, fruit infestation was predominated by B.
invadens, while damage by native fruit flies was negligible. Tropical almonds showed the
highest fruit fly infestation incidence (87.9%), and were mainly infested by B. invadens (82.1%).
Psidium guajava and Mangifera indica were also favorable hosts. There was significant
difference in infestation among mango varieties (p < 0.0001). Among the host fruit species,
female B. invadens fruit flies frequently oviposited most on fruits that gave better adapted
offsprings (support for Preference Performance Hypothesis-PPH), with overall coefficient of
determination (R2) for infestation averaging 75.4%. However, PPH was poorly evident among
the various mango varieties, with the trends suggestive of an Optimal Foraging Theory (OFT)
(oviposition on readily available fruits). B. invadens from different agro ecological zones and
fruit hosts were significantly different in morphology (p < 0.0001), which suggested that
geographic and host-associated adaptations could produce phenotypic variations that can lead to
ecotype and host populations. Precipitation (61.41%) and temperature (29.21%) were the most
important determinants of fruit fly distribution in the country. On that basis, the most suitable
habitats were central and mid north zones, while the western, north-eastern areas were marginal.
Future potential fruit fly habitats were projected to decline by 25.4% on average. Dacus
bivittatus, Bactrocera cucurbitae and Ceratitis anonae were projected to be the least climate
change resilient species. D. cilliatus (249.3%), B. invadens (-1.9%) and C. cosyra (-2.2%) were
projected to be the most climate change resilient species. Future fruit fly niches were predicted
to shift northwards, mainly to the northern moist farmlands. This study has provided knowledge
on several aspects of the ecology of fruit and crucial information that can help in the
development of adaptative pest management strategies in Uganda.