2011年2月16日 星期三

擴增基因序列取樣獲得蠶蛾總科高階親緣關係之穩定性

文獻出處: Zwick A., C. J. Regier, C. Mitter and M. P. Cummings. 2010. Increased gene sampling yields robust support for higher-level clades within Bombycoidea (Lepidoptera). Systematic Entomology. DOI: 10.1111/j.1365-3113.2010.00543.x


簡介

2008年由美國馬里蘭大學生物科技研究所Jerome C. Regier與現德國斯圖加特自然史博物館的Andreas Zwick博士等發表了針對蠶蛾總科與枯葉蛾總科親緣關係重建的研究。Regier等人選用50個蠶蛾總科、近緣枯葉蛾科與其他大鱗翅分類群,並取5段蛋白質轉錄基因序列(約6600鹼基對)進行親緣關係重建,然而此研究中蠶蛾總科並未獲得高支持度的單系性。


於2009年Cho等人利用多基因序列重建鱗翅目高階親緣關係,使超過10段基因所重建之親緣關係結果與其分析方法受到關注。Zwick等人此篇文章為了在實際經費與產出之間取得平衡,於是由2008年50個分類群中選取其中24個,將其基因額外增加20段蛋白轉錄基因(約11700鹼基對),也因此能評估分類群/分子序列取樣數差異對親緣重建所造成的影響。


作者將分類群/分子序列分為三組進行所得親緣樹之比較:

資料組 (A)- 50個分類群(非完全等同Regier等人2008年選用分類群)/5段序列

資料組 (B)- 50個分類群(同上述)/25段序列

資料組 (C)- 24個分類群/5段序列

結果顯示(B)(C)所重建之親緣枝系大致相似,且各枝系相對(A)呈現較高的樹形支持度,因此作者認為

(1) 增加資料的確可提高樹形支持度

(2) 擴增部份分類群之基因序列數量,造成其他分類群相對產生了missing data,然而卻並不會造成顯著的非親緣關係偏誤(nonphylogenetic bias)


依據此研究對於高支持、解析度的樹形評估,作者進行了蠶蛾總科與枯葉蛾總科之高階分類修訂:

(1) 蠶蛾科之成員縮限為原名亞科(Bombycinae);

(2) 原蠶蛾科Epiini族提升為亞科級(Epiinae);

(3) 原蠶蛾科Phiditinae亞科獨立為科級Phiditiidae;

(4) 原蠶蛾科之Oberthueriinae、Prismostictinae亞科與另一Mirinidae科視為樺蛾科Endromidae之晚近同物異名;

(5) 原枯葉蛾總科之Anthelidae重新置於蠶蛾總科。


台灣過去置於蠶蛾科之兩種波花樺(蠶)蛾 (Oberthueria formosibia Matsumura, 1927)小窗樺(蠶)蛾 (Prismosticta fenestrata Butler, 1880)據此視為樺蛾科類群


Abstract

This study has as its primary aim the robust resolution of higher-level relationships within the lepidopteran superfamily Bombycoidea. Our study builds on an earlier analysis of five genes (6.6 kbp) sequenced for 50 taxa from Bombycoidea and its sister group Lasiocampidae, plus representatives of other macrolepidoteran superfamilies. The earlier study failed to yield strong support for the monophyly of and basal splits within Bombycoidea, among others. Therefore, in an effort to increase support specifically for higher-level nodes, we generated 11.7 kbp of additional data from 20 genes for 24 of 50 bombycoid and lasiocampid taxa. The data from the genes are all derived from protein-coding nuclear genes previously used to resolve other lepidopteran relationships. With these additional data, all but a few higher-level nodes are strongly supported. Given our decision to minimize project costs by augmenting genes for only 24 of the 50 taxa, we explored whether the resulting pattern of missing data in the combined-gene matrix introduced a nonphylogenetic bias, a possibility reported by others. This was achieved by comparing node support values (i.e. nonparametric bootstrap values) based on likelihood and parsimony analyses of three datasets that differ in their number of taxa and level of missing data: 50 taxa/5 genes (dataset A), 50 taxa/25 genes (dataset B) and 24 taxa/25 genes (dataset C). Whereas datasets B and C provided similar results for common nodes, both frequently yielded higher node support relative to dataset A, arguing that: (i) more data yield increased node support and (ii) partial gene augmentation does not introduce an obvious nonphylogenetic bias. A comparison of single-gene bootstrap analyses identified four nodes for which one or two of the 25 genes provided modest to strong support for a grouping not recovered by the combined-gene result. As a summary proposal, two of these four groupings (one each within Bombycoidea and Lasiocampidae) were deemed sufficiently problematic to regard them as unresolved trichotomies. Since the alternative groupings were always highly localized on the tree, we did not judge a combined-gene analysis to present a problem outside those regions. Based on our robustly resolved results, we have revised the classification of Bombycoidea: the family Bombycidae is restricted to its nominate subfamily, and its tribe Epiini is elevated to subfamily rank (Epiinae stat.rev.), whereas the bombycid subfamily Phiditiinae is reinstated as a separate family (Phiditiidae stat.rev.). The bombycid subfamilies Oberthueriinae Kuznetzov & Stekolnikov, 1985, syn.nov. and Prismostictinae Forbes, 1955, syn.nov., and the family Mirinidae Kozlov, 1985, syn.nov. are established as subjective junior synonyms of Endromidae Boisduval, 1828. The family Anthelidae (Lasiocampoidea) is reincluded in the superfamily Bombycoidea.