臺灣大蕈蟲亞科物種多樣性研究

Abstract

探究喜腐木性昆蟲多樣性在生物多樣性領域的研究中很重要，它提供了未來生態學、演化和保育研究提供了基礎資訊。 大蕈蟲亞科是喜腐木性的蕈食性甲蟲，不同的大蕈蟲亞科物種會偏好不同種擔子菌門真菌。因此，探究大蕈蟲亞科的物種多樣性可顯現真菌的多樣性並與森林健康狀況有關。大蕈蟲亞科的物種多樣性研究面臨穩定的鑑定特徵不足的狀況並且缺乏完整的分類修訂和回顧。為了提供穩定的物種界線與完善的鑑定特徵，有必要探究大蕈蟲亞科的物種多樣性，我們結合了真菌寄主偏好、形態和DNA數據來研究台灣 大蕈蟲亞科的物種多樣性。我們的親緣關係分析結果顯示親緣關係相近的分類群可能具有相似的真菌寄主偏好，並且提供真菌-甲蟲相互作用研究設定了標竿。此外，我們的親緣關係分析顯示了舊世界大蕈蟲亞科各族之間的親緣關係，並揭示了 Encaustini 和 Dacnini族以及 Tritoma 和 Triplax 屬不是單系群，儘管在演化樹較接近根的節點有低的統計支持。基因樹不一致分析顯示我們的親緣關係樹除了粒線體和核基因的不一致外，還有核基因之間的不一致且不同親緣關係方法之間也存在差異。基於物種界定的結果，大蕈蟲亞科的物種多樣性是被低估的，顯示有高的隱蔽種多樣性和未描述的物種，但物種的種化歷程可能與寄主偏好沒有關係。我們認為大蕈蟲亞科中還有很多未描述的物種，為了加深我們對物種種化和寄主主偏好之間關係的認識，我們需要更多的物種採樣、共演化分析以及寄主專一性實驗。另外，大蕈蟲亞科的物種多樣性是否可以顯示示森林的健康程度還有待進一步的研究。

Exploring saproxylic insect diversity is important in biodiversity research that provides baseline information for downstream ecology, evolution, and conservation studies. Erotylinae beetles are saproxylic mycophagous insects where different species may have different host fungal preferences on several orders of Agaricomycetes. The species diversity of Erotylinae thus may be indicative of fungal diversity and related to forest health. Studying Erotylinae species diversity has been challenging because only few diagnostic characters are available, and lack of proper revisionary works. In this study, we incorporated multiple lines of evidences, e.g., fungal host preference, morphology, and molecular data, to study the species diversity of Taiwanese Erotylinae. We showed that closely related taxa may have similar fungal host preferences and set a benchmark for further fungus-beetle interaction studies using a phylogenetic approach. Additionally, our phylogenetic analysis showed the phylogenetic relationship among the Old World Erotylinae tribes and revealed that tribes Encaustini and Dacnini and genera Tritoma and Triplax are not monophyletic, although low posterior probabilities existed at the deeper nodes. The gene tree discordance analysis showed that there are mitonuclear discordance and nuclear-nuclear discordance and also discrepancy among different phylogenetic methods. The species diversity was underestimated with a high number of cryptic species and morphologically distinct species based on molecular species delimitation analyses, but the speciation may not be accompanied by host preference divergence. We conclude that there are still more undescribed species in Erotylinae and that, to enhance our understanding on the relationship between species divergence and host preference, and to test whether the Erotylinae species diversity can be indicative of forest health, additional sampling, cophylogenetic analyses, and host specialization experiments with genome-wide data are needed.