School of Forest Resources and Conservation, University of Florida, Gainesville FL 32611, United States.
Department of Biological Sciences, University of Memphis, Memphis, TN 38152, United States.
Mol Phylogenet Evol. 2018 Oct;127:229-238. doi: 10.1016/j.ympev.2018.05.028. Epub 2018 May 31.
Bark and ambrosia beetles (Curculionidae, Scolytinae) display a conspicuous diversity of unusual genetic and ecological attributes and behaviors. Reconstructing the evolution of Scolytinae, particularly the large and ecologically significant tribe Cryphalini (pygmy borers), has long been problematic. These challenges have not adequately been addressed using morphological characters, and previous research has used only DNA sequence data from small numbers of genes. Through a combination of anchored hybrid enrichment, low-coverage draft genomes, and transcriptomes, we addressed these challenges by amassing a large molecular phylogenetic dataset for bark and ambrosia beetles. The resulting DNA sequence data from 251 protein coding genes (114,276 bp of nucleotide sequence data) support inference of the first robust phylogeny of Scolytinae, with a special focus on the species rich tribe Cryphalini and its close relatives. Key strategies, including inbreeding mating systems and fungus farming, evolved repeatedly across Scolytinae. We confirm 12 of 16 hypothesized origins of fungus farming, 6 of 8 origins of inbreeding polygyny and at least 11 independent origins of a super-generalist host range. These three innovations are statistically correlated, but their appearance within lineages was not necessarily simultaneous. Additionally, the evolution of extreme host plant generalism often preceded, rather than succeeded, fungus farming. Of the high-diversity tribes of Scolytinae, only Xyleborini is monophyletic, Corthylini is paraphyletic and Cryphalini is highly polyphyletic. Cryphalini sensu stricto is part of a clade containing the genera Hypothenemus, Cryphalus and Trypophloeus, and the tribe Xyloterini. Stegomerus and Cryptocarenus (Cryphalini) are part of a clade otherwise containing all Corthylini. Several other genera, including Ernoporus and Scolytogenes (Cryphalini), make up a distantly related clade. Several of the genera of Cryphalini are also intermixed. For example, Cryphalus and Hypocryphalus are intermingled, as well as Ernoporicus, Ptilopodius and Scolytogenes. Our data are consistent with widespread polyphyly and paraphyly across Scolytinae and within Cryphalini, and provides new insights into the evolution of inbreeding mating systems and fungus farming in the species rich and ecologically significant weevil subfamily Scolytinae.
树皮和芳香甲虫（象甲科，小蠹科）表现出显著的不寻常的遗传和生态属性和行为多样性。重建小蠹科的进化，特别是大型且具有生态意义的 Cryphalini 部落（小矮人蛀虫），一直是一个问题。这些挑战使用形态特征未能充分解决，并且以前的研究仅使用了来自少数基因的 DNA 序列数据。通过结合锚定杂交富集、低覆盖率草图基因组和转录组，我们通过积累大量的树皮和芳香甲虫分子系统发育数据集来解决这些挑战。来自 251 个蛋白质编码基因的 DNA 序列数据（核苷酸序列数据 114,276bp）支持小蠹科的第一个稳健系统发育的推断，特别关注物种丰富的 Cryphalini 部落及其近亲。关键策略，包括近亲交配系统和真菌养殖，在小蠹科中反复进化。我们证实了 16 种真菌养殖起源中的 12 种、8 种近亲多态性婚制起源中的 6 种以及至少 11 种超级广义宿主范围的独立起源。这三个创新是统计相关的，但它们在谱系中的出现并不一定是同时的。此外，极端寄主植物广食性的进化往往先于真菌养殖，而不是紧随其后。在小蠹科的高多样性部落中，只有 Xyleborini 是单系的，Corthylini 是并系的，而 Cryphalini 是高度多系的。Cryphalini sensu stricto 是一个包含 Hypothenemus、Cryphalus 和 Trypophloeus 属以及 Xyloterini 部落的分支的一部分。Stegomerus 和 Cryptocarenus（Cryphalini）是一个包含所有 Corthylini 的分支的一部分。其他几个属，包括 Ernoporus 和 Scolytogenes（Cryphalini），组成了一个远缘分支。几个 Cryphalini 属也相互混合。例如，Cryphalus 和 Hypocryphalus 混合在一起，还有 Ernoporicus、Ptilopodius 和 Scolytogenes。我们的数据与小蠹科的广泛多系和并系以及 Cryphalini 内部的多系和并系一致，并为物种丰富且具有生态意义的象甲亚科小蠹科中近亲交配系统和真菌养殖的进化提供了新的见解。
