Endress, P.

Friis, E.

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Rosids - Reproductive structures, fossil and extant,and their bearing on deep relationships: IntroductionP. K. Endress1 and E. M. Friis21Institute of Systematic Botany, University of Zurich, Zurich, Switzerland2Dept. of Palaeobotany, Swedish Museum of Natural History, Stockholm, SwedenAs a consequence of the rapid and successfulprogress of phylogenetics in the past decade,there is an increasing imbalance between ourinsight on phylogenetic relationships and theevolution of structure and biology of angio-sperms. However important a continuousimprovement of resolution of the phylogenetictree of angiosperms is, it remains of limited useif the structure and biology of the newlyrecognized clades are not studied concomi-tantly.In addition, despite the phylogenetic ad-vances, the relationships between many largeclades are still not well resolved. This isparticularly true for the relationships betweenthe orders of rosids (Judd and Olmstead 2004,Soltis et al. 2005, Sytsma 2005). Thus straight-forward comparative structural studies arehampered by such uncertainties. Nevertheless,to avoid a vacuum we should not hesitate tobuild on the available new fundament, even ifit is still shaky at some places.In such comparative approaches the struc-ture of extant and fossil plants should bestudied in an integrative way (Friis and Endress1990, Endress and Friis 1994, Zimmer et al.2000, Scho¨nenberger et al. 2001, Doyle et al.2003, Friis et al. 2006). Anatomical techniquesdeveloped on extant plants can also be used forcharcoaliﬁed fossil plants. These techniquesallow not only anatomical and histologicalstudies in fossils but also a morphologicalreconstruction of the outer and inner surfacesof the organs in ﬂowers (Scho¨nenbergeret al. 2001, Friis et al. 2003, Scho¨nenberger2005).Rosids are one of the largest clades of theﬂowering plants. Molecular systematics hasidentiﬁed a number of larger monophyleticcomponents at the order level, some with thesame circumscription as in traditional classiﬁ-cations, others with new and unexpected asso-ciations of families or family clusters. Yet therelationships between the orders, i.e. deeprelationships, are not well resolved. Numerousfossil ﬂowers, fruits and seeds recovered fromLate Cretaceous ﬂoras over the past 25 yearsare crucial for the recognition of deep rela-tionships. Among Late Cretaceous rosids, taxarelated to Saxifragales, Fagales, and Rosalesare particularly common (e.g. Crane et al.2004, Crepet et al. 2004, Friis et al. 2005), butmost of the enormous diversity of Late Creta-ceous reproductive structures remains to bestudied. Based on our current knowledge it isclear that many extant lineages were wellPl. Syst. Evol. 260: 83–85 (2006)DOI 10.1007/s00606-006-0438-5established in the Late Cretaceous ﬂoras co-occurring with many extinct groups (e.g. Friiset al. 2006). Unusual structural features inﬂowers of larger clades may have sharedunderlying patterns that are synapomorphiesfor these clades (e.g. the androecium in Mal-vales). However, such underlying patternsoften have not been worked out in detail andneed critical comparative studies. Comparisonof reproductive structures among extantgroups and fossils of rosids will also be animportant component in unravelling theirevolutionary history. Exceptional groups witha rich fossil record but perhaps no direct extantdescendents need to be compared amongthemselves and with the putative closest extantrelatives (e.g. Normapolles pollen with ﬂoralfossils and with extant Fagales).For the interpretation of fossil ﬂowersknowledge on the structure and biology ofextant ﬂowers is necessary. Vice versa, fossilﬂowers, if correctly interpreted, are not onlycrucial for calibration of evolutionary events,as are fossils in general, but can reveal infor-mation on the past diversity and evolution ofextant reproductive structures.The following publications are essentiallythe contributions to a Symposium on Rosids -Reproductive structures, fossil and extant, andtheir bearing on deep relationships, which washeld at the XVII International Botanical Con-gress, Vienna, in July 2005. The symposiumintended to include and, if possible, integratefossil and extant reproductive structures ofrosids and to advance our knowledge onmorphology and relationships and evolutionwithin larger clades of rosids.Scho¨nenberger and von Balthazar (2006)give an introduction and overview of thecurrent state of knowledge of extant and fossilrosid reproductive structures in the frameworkof phylogeny and evolution. Friis et al. (2006)provide a review and new aspects on theextinct Normapolles group (Fagales), whichplayed an important role in the Late Creta-ceous and Early Cainozoic ﬂora and vegeta-tion of Europe, with special emphasis on thecoordination of isolated pollen with ﬂoralstructures. Hermsen et al. (2006) discuss theevolution of reproductive structures of Saxi-fragales based on phylogenetic studies includ-ing fossil data. Von Balthazar et al. (2006)provide new aspects for ﬂoral developmentand evolution in extant Malvales, with a focuson the Malvatheca clade of Malvaceae s.l.Matthews and Endress (2006) trace the distri-bution of a new systematic feature in rosidﬂowers, specialized mucilage cells, and com-pare the characterization of new clades withinfour rosid orders by ﬂoral structural features.Finally, Endress and Matthews (2006) makeﬁrst steps towards a ﬂoral structural charac-terization of the new supraordinal clades ofrosids as found recently in molecular phyloge-netic studies by other authors. A symposiumcontribution by P. Herendeen who used thefossil record of legumes to test evolutionaryand biogeographic hypotheses is here notincluded.We hope that this collection of publicationson structural features of rosids will catalyzenew studies on the structural and evolutionaryunderstanding of rosids and their componentclades and also of other large angiospermgroups.ReferencesvonBalthazarM., Scho¨nenberger J.,AlversonW.S.,Janka H., Bayer C., Baum D. A. (2006) Structureand evolution of the androecium in the Malvat-heca clade (Malvaceae s.l.) and implications forMalvaceae and Malvales. Pl. Syst. Evol. 260:171–197.Crane P. R., Herendeen P., Friis E. M. (2004)Fossils and plant phylogeny. Amer. J. Bot. 91:1683–1699.Crepet W. L., Nixon K. C., Gandolfo M. A. (2004)Fossil evidence and phylogeny: the age of majorangiosperm clades based on mesofossil andmacrofossil evidence from Cretaceous deposits.Amer. J. Bot. 91: 1666–1682.Doyle J. A., Eklund H., Herendeen P. S. (2003)Floral evolution in Chloranthaceae: implicationsof a morphological phylogenetic analysis. Int. J.Pl. Sci. 164 (5, Suppl.): S365–S382.84 P. K. Endress and E. M. Friis: Rosids - Reproductive structures, fossil and extantEndress P. K., Friis E. M. (eds.) (1994) Earlyevolution of ﬂowers. Pl. Syst. Evol. Suppl. 8: 1–229.Endress P. K., Matthews M. L. (2006) First stepstowards a ﬂoral structural characterization ofthe major rosid subclades. Pl. Syst. Evol. 260:223–251.Friis E. M., Endress P. K. (1990) Origin andevolution of angiosperm ﬂowers. Adv. Bot. Res.17: 99–162.Friis E. M., Pedersen K. R., Scho¨nenberger J.(2003) Endressianthus, a new Normapolles-producing plant genus of fagalean aﬃnity fromthe Late Creataceous of Portugal. Int. J. Pl. Sci.164 (Supplement), S201–S223.Friis E. M., Pedersen K. R., Crane P. R. (2005)When Earth started blooming: insights from thefossil record. Curr. Opin. Pl. Biol. 8: 5–12.Friis E. M., Pedersen K. R., Crane P. R. (2006)Cretaceous angiosperm ﬂowers: innovation andevolution in plant reproduction. Palaeogeogr.,Palaeoclimatol., Palaeoecol. 232: 251–293.Friis E. M., Pedersen K. R., Scho¨nenberger J.(2006) Normapolles plants: a prominent compo-nent of the Cretaceous rosid diversiﬁcation. Pl.Syst. Evol. 260: 107–140.Hermsen E. J., Nixon K. C., Crepet W. L. (2006)Fossil reproductive structures of Saxifragalesand saxifrage evolution. Pl. Syst. Evol. 260: 141–169.Judd W. S., Olmstead R. G. (2004) A survey oftricolpate (eudicot) phylogenetic relationships.Amer. J. Bot. 91: 1627–1644.Matthews M. L., Endress P. K. (2006) Floralstructure and systematics in four orders ofrosids, including a broad survey of ﬂoral muci-lage cells. Pl. Syst. Evol. 260: 199–221.Scho¨nenberger J. (2005) Rise from the ashes –reconstruction of charcoal fossil ﬂowers. TrendsPl. Sci. 10: 436–443.Scho¨nenberger J., von Balthazar M. (2006) Repro-ductive structures and phylogenetic frameworkof the rosids – progress and prospects. Pl. Syst.Evol. 260: 87–106.Scho¨nenberger J., Friis E. M., Matthews M. L.,Endress P. K. (2001) Cunoniaceae in the Creta-ceous of Europe: evidence from fossil ﬂowers.Ann. Bot. 88: 439–455.Soltis D. E., Soltis P. S., Endress P. K., ChaseM.W.(2005) Phylogeny and evolution of angiosperms.Sinauer, Sunderland, MA.Sytsma K. J., Hall J. (2005) Rosid angiosperms:circumscription, issues, and systematic advances.XVII International Botanical Congress, Vienna.Abstract 5.8.3., pp. 84–85.Zimmer E. A., Qiu Y.-L., Endress P. K., Friis E. M.(eds.) (2000) Current perspectives on basalangiosperms. Int. J. Pl. Sci. 161 (Suppl. 6): S1–S248.Addresses of the authors: Peter K. Endress(e-mail: pendress@systbot.unizh.ch), Institute ofSystematic Botany, University of Zurich, Zolliker-strasse 107, 8008 Zurich, Switzerland. Else MarieFriis, Dept. of Palaeobotany, Swedish Museum ofNatural History, Box 50007, 104 05 Stockholm,Sweden.P. K. Endress and E. M. Friis: Rosids - Reproductive structures, fossil and extant 85

Rosids - Reproductive structures, fossil and extant, and their bearing on deep relationships: Introduction

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Rosids - Reproductive structures, fossil and extant, and their bearing on deep relationships: Introduction

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