Schuster Astrid, Erpenbeck Dirk, Pisera Andrzej, Hooper John, Bryce Monika, Fromont Jane, Wörheide Gert
Department of Earth- & Environmental Sciences, Palaeontology and Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner Str. 10, 80333 Munich, Germany; SNSB - Bavarian State Collections of Palaeontology and Geology, Richard-Wagner Str. 10, 80333 Munich, Germany.
Department of Earth- & Environmental Sciences, Palaeontology and Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner Str. 10, 80333 Munich, Germany; GeoBio-CenterLMU, Ludwig-Maximilians-Universität München, Richard-Wagner Str. 10, 80333 Munich, Germany.
PLoS One. 2015 Jan 7;10(1):e116038. doi: 10.1371/journal.pone.0116038. eCollection 2015.
Reconciling the fossil record with molecular phylogenies to enhance the understanding of animal evolution is a challenging task, especially for taxa with a mostly poor fossil record, such as sponges (Porifera). 'Lithistida', a polyphyletic group of recent and fossil sponges, are an exception as they provide the richest fossil record among demosponges. Lithistids, currently encompassing 13 families, 41 genera and >300 recent species, are defined by the common possession of peculiar siliceous spicules (desmas) that characteristically form rigid articulated skeletons. Their phylogenetic relationships are to a large extent unresolved and there has been no (taxonomically) comprehensive analysis to formally reallocate lithistid taxa to their closest relatives. This study, based on the most comprehensive molecular and morphological investigation of 'lithistid' demosponges to date, corroborates some previous weakly-supported hypotheses, and provides novel insights into the evolutionary relationships of the previous 'order Lithistida'. Based on molecular data (partial mtDNA CO1 and 28S rDNA sequences), we show that 8 out of 13 'Lithistida' families belong to the order Astrophorida, whereas Scleritodermidae and Siphonidiidae form a separate monophyletic clade within Tetractinellida. Most lithistid astrophorids are dispersed between different clades of the Astrophorida and we propose to formally reallocate them, respectively. Corallistidae, Theonellidae and Phymatellidae are monophyletic, whereas the families Pleromidae and Scleritodermidae are polyphyletic. Family Desmanthidae is polyphyletic and groups within Halichondriidae--we formally propose a reallocation. The sister group relationship of the family Vetulinidae to Spongillida is confirmed and we propose here for the first time to include Vetulina into a new Order Sphaerocladina. Megascleres and microscleres possibly evolved and/or were lost several times independently in different 'lithistid' taxa, and microscleres might at least be four times more likely lost than megascleres. Desma spicules occasionally may have undergone secondary losses too. Our study provides a framework for further detailed investigations of this important demosponge group.
协调化石记录与分子系统发育关系以增进对动物进化的理解是一项具有挑战性的任务，对于化石记录大多匮乏的类群而言尤其如此，比如海绵动物门（多孔动物门）。“石海绵目”是一类包含现生和化石海绵的多系群，它们是个例外，因为在寻常海绵纲中它们拥有最丰富的化石记录。石海绵目前包含13个科、41个属以及超过300个现生物种，其定义特征是共同拥有特殊的硅质骨针（联骨针），这些骨针通常形成坚硬的关节状骨架。它们的系统发育关系在很大程度上尚未明确，并且还没有（从分类学角度）进行全面分析以正式地将石海绵类群重新划归到其最亲近的类群中。本研究基于迄今为止对“石海绵目”寻常海绵进行的最全面的分子和形态学调查，证实了一些先前支持力度较弱的假说，并为之前的“石海绵目”的进化关系提供了新的见解。基于分子数据（部分线粒体DNA CO1和28S rDNA序列），我们发现13个“石海绵目”科中有8个属于星骨海绵目，而硬皮海绵科和管指海绵科在四放海绵纲内形成一个独立的单系分支。大多数石海绵目星骨海绵分散在星骨海绵目的不同分支之间，我们建议分别对它们进行正式的重新归类。珊瑚海绵科、皮海绵科和拟网海绵科是单系的，而厚皮海绵科和硬皮海绵科是多系的。联骨海绵科是多系的，并且归入毛壶科内——我们正式提议进行重新归类。确认了维图林海绵科与淡水海绵目的姐妹群关系，并且我们在此首次提议将维图林海绵归入一个新的球枝海绵目。大骨针和小骨针可能在不同的“石海绵目”类群中多次独立进化和/或消失，并且小骨针消失的可能性可能至少是大骨针的四倍。联骨针偶尔也可能经历了次生消失。我们的研究为进一步详细研究这个重要的寻常海绵类群提供了一个框架。
