Ramírez-Benavides William
Rev Biol Trop. 2016 Dec;64(4):1721-35. doi: 10.15517/rbt.v64i4.20808.
It has been assumed that Tetrapus female wasps (Agaonidae s.s.), the pollinators of the figs of the New World, section Pharmacosycea, are mainly characterized by the presence of one mandibular appendange only, and that it is the most ancestral clade of extant Agaonidae s.s., and the males are tetrapodous. The main objective of this work was to study five Tetrapus morphotypes, whose females have two mandibular appendages and the males are hexapodous, their fig host association and phylogenetic position to the family Agaonidae. The question of which group of fig pollinating wasps and associated figs are the sister to the rest of the pollinating agaonids, and figs respectively remain open. I report a group of New World extant Tetrapus morphotypes (Agaonidae: Agaoninae) provisionally assigned to Hexapus subg. nov. in preparation. Currently, Tetrapus appears as the sister taxon to all other fig pollinating taxa. Howeveer, morphologically, ecologically, geographically and historically Hexapus seems to be the ancestral clade of the extant Agaoninae. Hexapus morphotypes develop in fig species of subsection Petenenses (section Pharmacosycea). In the known extant Tetrapus, the females have one mandibular appendage and the males have reduced one or two short-lobe atrophied non-functional midlegs (tetrapodous). Hexapus females have two free mandibular appendages, and the males have five segmented functional mid-legs (hexapodous). Molecularly Hexapus seems to be the ancestral clade of extant Agaoninae; e.g., a Tetrapus sp. of Ficus crassivenosa was placed by other author as the ancestral clade of 101 wasp species, representing 19 worldwide Agaoninae genera, including four Tetrapus species. In Tetrapus sp. of Ficus crassivenosa, the female has two mandibular appendages and the male is hexapodous. The females of T. apopnus and T. delclosi, preserved in Early to mid-Miocene amber from the Dominican Republic, also have two mandibular appendages and the general morphology of extant Hexapus. I suggest that Hexapus stands up as a living fossil and the sister clade of Tetrapus s.s. The presence of extant Hexapus; as well as extant Tetrapus and their fig host species, especially in South America supports a Southern Gondwanaland origin for both of them, but not a trans-Pacific migrating connection with tropical America for section Pharmacosycea (the host of Tetrapus and Hexapus), a long oceanic dispersal, high levels of stem extinction of Tetrapus or Atlantic land connections, as proposed by other authors. However, lastly it has been assumed that figs and their pollinators arose simultaneously in Eurasia during early Tertiary and spread southwards from it. Most of the morphological and molecular studies of the fig biology of Agaoninae and Ficus, did not include Hexapus morphotypes and their fig hosts, and assumed that Tetrapus is the most ancestral clade of the extant fig pollinating wasps.
一直以来人们认为，新世界药囊榕亚组（Pharmacosycea）榕果的传粉者四足小蜂（狭义榕小蜂科）主要特征是仅具有一个下颚附器，并且它是现存狭义榕小蜂科最原始的分支，而雄性为四足。本研究的主要目的是研究五种四足小蜂形态型，其雌性具有两个下颚附器，雄性为六足，研究它们与榕果宿主的关联以及在榕小蜂科中的系统发育位置。关于哪一组榕果传粉小蜂及其相关榕果分别是其他传粉榕小蜂及其榕果的姐妹群这一问题仍然没有答案。我报告了一组新世界现存的四足小蜂形态型（榕小蜂科：榕小蜂亚科），暂归入新的六足小蜂亚属（Hexapus subg. nov.），正在整理中。目前，四足小蜂似乎是所有其他榕果传粉类群的姐妹分类单元。然而，从形态学、生态学、地理分布和历史角度来看，六足小蜂似乎是现存榕小蜂亚科的原始分支。六足小蜂形态型在佩滕榕亚组（药囊榕亚组）的榕树种中发育。在已知的现存四足小蜂中，雌性具有一个下颚附器，雄性的中腿有一或两个短叶萎缩且无功能（四足）。六足小蜂的雌性有两个游离的下颚附器，雄性有分五节的功能性中腿（六足）。从分子层面看，六足小蜂似乎是现存榕小蜂亚科的原始分支；例如，其他作者将粗叶榕的一种四足小蜂置于101种黄蜂物种的原始分支中，这些黄蜂代表了全球19个榕小蜂亚科属，包括四种四足小蜂。在粗叶榕的四足小蜂中，雌性有两个下颚附器，雄性为六足。保存在多米尼加共和国早中新世至中新世中期琥珀中的阿波普努斯四足小蜂和德尔克洛西四足小蜂的雌性也有两个下颚附器，且具有现存六足小蜂的一般形态。我认为六足小蜂是一个活化石，并且是狭义四足小蜂的姐妹分支。现存六足小蜂以及现存四足小蜂及其榕果宿主物种的存在，特别是在南美洲，支持了它们两者都起源于冈瓦纳大陆南部，但不支持如其他作者所提出的药囊榕亚组（四足小蜂和六足小蜂的宿主）与热带美洲有跨太平洋迁徙联系、长距离海洋扩散、四足小蜂高水平的主干灭绝或大西洋陆地连接。然而，最后一直以来人们认为榕果及其传粉者在第三纪早期同时出现在欧亚大陆，并从那里向南扩散。大多数关于榕小蜂亚科和榕属榕果生物学的形态学和分子研究都没有包括六足小蜂形态型及其榕果宿主，并且认为四足小蜂是现存榕果传粉小蜂最原始的分支。
