Description: Das Projekt "Are extrafloral nectaries a key innovation in plant defense strategies? Insigths from the large, widespread and diverse legume genus Senna" wird vom Umweltbundesamt gefördert und von Universität Zürich, Institut für Pflanzenbiologie durchgeführt. The main goal of the study presented here was to test whether extrafloral nectaries (EFNs) are a key innovation in plant defense strategies. EFNs occur in greater than 90 flowering plant families, typically in Leguminosae (=Fabaceae). Located commonly on vegetative parts, EFNs secrete nectar, attracting ants and forming ecologically important ant-plant mutualisms. These mutualisms may confer a higher fitness to EFN-plants and, thus, an increased potential for survival, dispersal, and adaptation, and ultimately to undergo speciation. Key innovations are one of the most important triggers of radiations and large-scale diversifications in nature. But, unraveling the diversification history of old, species-rich and widespread clades is difficult, because of extinction, undersampling and taxonomic problems. In the context of these challenges, we investigated the timing and mode of lineage diversification in the widespread legume genus Senna to gain insights into the evolutionary role of its EFNs. In Senna, EFNs characterize one large clade (EFN clade), including 80Prozent of its 350 species. Fossil evidence indicates that Senna dates from the Eocene, predating many legume genera. We outlined a novel powerful framework for key innovation hypothesis testing in old, widespread and species-rich clades, like Senna. This consists of the combination of a list of four criteria for morphological novelties to qualify as key innovation, together with an accurate inference of the diversification history of the entire study group (i.e. accurate estimation of divergence times, diversification rates, and clade sizes), and an adequate method for testing shifts in diversification rates. Our molecular dating analyses suggest that Senna originated in the early Eocene (ca. 50 Million years (My) ago), and its major lineages appeared during early/mid Eocene to early Oligocene. EFNs evolved in the late Eocene (ca. 35-40 My ago), after the main radiation of ants. The EFN clade diversified faster, becoming significantly more species-rich than non-EFN clades. The shift in diversification rates associated with EFN evolution supports the hypothesis that EFNs represent a (relatively old) key innovation in Senna. EFNs may have promoted the colonization of new habitats appearing with the early uplift of the Andes. This would explain the distinctive geographic concentration of the EFN clade in South America (144 species). Evolution of the EFNs may have helped the EFN clade to undergo a rapid radiation leading to the outstanding floral diversity observed in extant taxa. The study is the first to provide evidence for the role of a plant-ant protective mutualism in triggering plant diversification.
Types:
SupportProgram
Origin: /Bund/UBA/UFORDAT
Tags: Ameise ? Besiedlung ? Schlichtemittel ? Zierpflanze ? Zürich ? Artenverlust ? Auftrieb ? Botanik ? Leguminosen ? Ökologie ? Anden ? Main ? Blütenpflanze ? Datierung ? Diversifikation ? Habitat ? Strahlung ? Evolution ? Familie ? Geographie ? Innovation ? Studie ? Wettbewerbsfähigkeit ? Wertermittlung ? Amerika ? Strategische Aspekte ? divergence times ? ABSCHAETZUNG ? diversification rates ? extrafloral nectaries ? key innovation ? large-scale diversification ? morphological diversity ? ARBEITSAUSSCHUESSE ? ARBEITSAUSSCHUSS ? Art [Spezies] ? Bemessung ? Bepflanzung ? Diversität ? EIN ? EVOLUTIONAER ? Einwendung ? ANDEN ? GEGENWART ? HILF ? KRITERIUM ? Konzentrat ? METHODE ? MISCHUNG ? NEU ? POTENZIAL ? SCHWERPUNKT ? SUEDLICH ? Senna ? TEIL ? UEBERLEBEN ? UNTERSUCHUNG ? Vermehrung ? WICHTIG ? FOERDERN ?
License: cc-by-nc-nd/4.0
Language: Deutsch
Time ranges: 2007-11-01 - 2008-10-31
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