Data for: The paradoxical rarity of a parasitic fruit fly fungus attacking a broad range of hosts

Understanding the factors that determine the realized and potential distribution of a species requires knowledge of abiotic, physiological, limitations as well as ecological interactions. Entomopathogenic fungi of the order Laboulbeniales specialize on arthropod hosts and are typically thought to be highly specialized on a single host or closely related group of hosts. Because infections are solely transmitted through direct contact of the hosts, the host ecology to a large extent determines the distribution and occurrence of the fungus. We examined ~20,000 fruit flies (Diptera: Dacinae) collected in Malaysia, Sulawesi, Australia and the Solomon Islands between 2017–2019 for ectoparasitic fungal infections and found 197 infected flies across eight different Bactrocera species. Morphology and small subunit (18S) DNA sequences both support that the infections are from a single polyphagous fungal species. This presents the paradox of why S. dacinus is not more common when its hosts are widespread and ubiquitous. In addition, the hosts are all Bactrocera, a genus with ~480 species, but many sympatric Bactrocera were never infected. Host-selection does not appear to be phylogenetically correlated. Our results show that a single fungus species can be found on different host species in different continents. We discuss factors that might be involved in determining the host and distribution range of S. dacinus, such as host resistance, and discuss the potential for population control of agriculturally important hosts, such as the pestiferous Oriental fruit fly Bactrocera dorsalis and the Queensland fruit fly B. tryoni.

要探明决定物种现实分布与潜在分布的影响因子，需同时掌握非生物因子、生理限制条件及生态互作相关知识。虫囊菌目（Laboulbeniales）的昆虫病原真菌专性寄生于节肢动物宿主，学界普遍认为其对单一宿主或亲缘关系密切的宿主类群具有高度专一性。由于该类真菌仅通过宿主间的直接接触传播，宿主的生态特征在很大程度上决定了真菌的分布与发生状况。2017年至2019年间，我们对采自马来西亚、苏拉威西、澳大利亚及所罗门群岛的约20000头实蝇（双翅目：实蝇亚科（Dacinae））开展了外寄生真菌感染筛查，最终在8个不同寡鬃实蝇属（Bactrocera）物种中发现197头受感染实蝇。形态学观察与18S核糖体DNA小亚基（18S）序列分析均证实，上述感染均源自单一多食性真菌物种。这一结果引出一个难解的悖论：在其宿主分布广泛且随处可见的情况下，为何达克努斯真菌（S. dacinus）并未更为常见？此外，所有受感染宿主均属于寡鬃实蝇属（Bactrocera）——该属共包含约480个物种，但诸多同域分布的寡鬃实蝇从未被该真菌感染。该真菌的宿主选择似乎与宿主的系统发育关系并无关联。本研究结果表明，单一真菌物种可在不同大陆的不同宿主物种上被检测到。我们探讨了可能影响达克努斯真菌（S. dacinus）宿主范围与分布区域的各类因子（如宿主抗性），并讨论了利用该真菌对具有农业经济重要性的宿主种群进行生物防控的潜力——这些宿主包括为害严重的东方果实蝇（Bactrocera dorsalis）与昆士兰果实蝇（B. tryoni）。