Clarke Anthony R, Leach Peter, Measham Penelope F
School of Biology and Environmental Science, Queensland University of Technology (QUT), P.O. Box 2434, Brisbane, QLD 4001, Australia.
Horticulture and Forestry Science, Department of Agriculture and Fisheries, P.O. Box 652, Cairns, QLD 4870, Australia.
Insects. 2022 Sep 28;13(10):882. doi: 10.3390/insects13100882.
The genus (Diptera: Tephritidae) is endemic to the monsoonal rainforests of South-east Asia and the western Pacific where the larvae breed in ripe, fleshy fruits. While most remain rainforest restricted, species such as , and are internationally significant pests of horticulture, being both highly invasive and highly polyphagous. Almost universally in the literature it is assumed that breed continuously if temperature and hosts are not limiting. However, despite that, these flies show distinct seasonality. If discussed, seasonality is generally attributed to the fruiting of a particular breeding host (almost invariably mango or guava), but the question appears not to have been asked why flies do not breed at other times of the year despite other hosts being available. Focusing initially on , for which more literature is available, we demonstrate that the seasonality exhibited by that species is closely correlated with the seasons of its endemic rainforest environment as recognised by traditional Aboriginal owners. Evidence suggests the presence of a seasonal reproductive arrest which helps the fly survive the first two-thirds of the dry season, when ripe fruits are scarce, followed by a rapid increase in breeding at the end of the dry season as humidity and the availability of ripe fruit increases. This seasonal phenology continues to be expressed in human-modified landscapes and, while suppressed, it also partially expresses in long-term cultures. We subsequently demonstrate that , across both its endemic and invasive ranges, shows a very similar seasonality although reversed in the northern hemisphere. While high variability in the timing of population peaks is exhibited across sites, a four-month period when flies are rare in traps (Dec-Mar) is highly consistent, as is the fact that nearly all sites only have one, generally very sharp, population peak per year. While literature to support or deny a reproductive arrest in is not available, available data is clear that continuous breeding does not occur in this species and that there are seasonal differences in reproductive investment. Throughout the paper we reinforce the point that our argument for a complex reproductive physiology in is based on inductive reasoning and requires specific, hypothesis-testing experiments to confirm or deny, but we do believe there is ample evidence to prioritise such research. If it is found that species in the genus undergo a true reproductive diapause then there are very significant implications for within-field management, market access, and biosecurity risk planning which are discussed. Arguably the most important of these is that insects in diapause have greater stress resistance and cold tolerance, which could explain how tropical species have managed to successfully invade cool temperate regions.
[果蝇属（双翅目：实蝇科）] 原产于东南亚和西太平洋的季风雨林，其幼虫在成熟的肉质果实中繁殖。虽然大多数[果蝇]仍局限于雨林，但诸如[某些果蝇物种]等物种是具有国际重要性的园艺害虫，具有高度的入侵性和多食性。几乎在所有文献中都认为，如果温度和寄主不受限制，[果蝇]会持续繁殖。然而，尽管如此，这些果蝇表现出明显的季节性。如果讨论到季节性，通常归因于特定繁殖寄主（几乎总是芒果或番石榴）的结果，但问题似乎是，尽管有其他寄主可供利用，为什么果蝇在一年中的其他时间不繁殖却从未被问起过。最初以[某种果蝇]为重点，因为有更多关于它的文献，我们证明该物种表现出的季节性与传统原住民所认可的其原生雨林环境的季节密切相关。有证据表明存在季节性生殖停滞，这有助于果蝇在旱季的前三分之二时间存活下来，此时成熟果实稀少，随后随着旱季结束时湿度和成熟果实可用性的增加，繁殖迅速增加。这种季节性物候在人类改造的景观中仍然存在，并且虽然受到抑制，但在长期的养殖环境中也会部分表现出来。我们随后证明，[另一种果蝇]在其原生和入侵范围内都表现出非常相似的季节性，尽管在北半球情况相反。虽然不同地点的[果蝇]种群高峰期时间存在很大差异，但诱捕器中果蝇稀少的四个月时期（12月至次年3月）非常一致，而且几乎所有地点每年通常只有一个，且通常非常明显的种群高峰期这一事实也是如此。虽然没有支持或否定[某种果蝇]存在生殖停滞的文献，但现有数据清楚地表明该物种不会持续繁殖，并且在生殖投入方面存在季节性差异。在整篇论文中，我们强调我们关于[果蝇]具有复杂生殖生理的论点是基于归纳推理，需要进行特定的假设检验实验来证实或否定，但我们确实认为有充分的证据优先进行此类研究。如果发现果蝇属中的物种经历真正的生殖滞育，那么对于田间管理、市场准入和生物安全风险规划将产生非常重大的影响，我们将对此进行讨论。可以说其中最重要的一点是，处于滞育状态的昆虫具有更强的抗逆性和耐寒性，这可以解释热带[果蝇]物种是如何成功入侵凉爽温带地区的。
