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Evolution of the basal angiosperm family Winteraceae on Zealandia

Evolution of the basal angiosperm family Winteraceae on Zealandia. Chrissen Gemmill*, Steven Pratt, Jérôme Munzinger , Porter Lowry II, Nick Demetras. INTRODUCTION

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Evolution of the basal angiosperm family Winteraceae on Zealandia

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  1. Evolution of the basal angiosperm family Winteraceae on Zealandia Chrissen Gemmill*, Steven Pratt, JérômeMunzinger, Porter Lowry II, Nick Demetras INTRODUCTION The oceanic islands of New Zealand and New Caledonia are cut from much the same cloth: they are both off cast fragments of Gondwana, have endured dynamic and transformative geological processes including periods of submergence, and have been isolated from any other landmasses in the southern Pacific ocean for similar time frames. Furthermore, these islands are intimately connected as they both rest upon the sunken former continent of Zealandia (Fig 1). Evidence of this shared history is reflected by the numerous flowering plant families that are found on both of these sister- archipelagos. This study focuses on the evolution of the iconic plant family Winteraceae of Zealandia, and specifically on the sister genera Pseudowintera and Zygogynum (sensulato). Winteraceae are an ancient, mostly Southern Hemisphere angiosperm family of evergreen trees, known for their vessel-less wood, peppery scent, remarkable flowers and excellent fossil record. Winteraceaeare represented in New Zealand by a single genus Pseudowintera (horopito) with four extant endemic, well-known species. The case is quite different for the New Caledonian taxa, which reveal a complex taxonomic history. The most recent revisions by Vink were highly radical, placing all members of four previously recognized genera into a single broadly defined genus Zygogynum(Fig 2.) comprising 18 endemic species, within which he also recognized 13 subspecies and 3 varieties for a total of 30 taxa. It is not clear whether the characters used to delimit these infraspecific entities are constant or if they are phenotypically plastic and hence taxonomically artificial and uninformative. Fig 1. Zealandia Fig 2. Zygogynum

  2. METHODS To test Vink's taxonomic hypotheses and resolve relationships among these taxa, we have sampled Zealandic taxa comprehensively and used both nuclear (ITS) and cpDNA(psbA-trnH) sequence variation.

  3. RESULTS ITS only analysis: Subset ITS + cpDNA:998 characters, 896 constan, 63 parsimony-informative, 39 autapomorphic characters; GTR+Γ+I Insert full ITS tree and ITS+cpDNA trees here.

  4. CONCLUSIONS • Preliminary analyses suggest that Zygogynum is not monophyletic with Z. amplecicaule (including all currently recognized infraspecific taxa) sister to Pseudowintera and the remaining Zygogynum taxa. Within the large Zygogynum clade, some species are resolved as monophyletic (e.g., Z. comptonii), while many remain paraphyletic. Overall our analyses suggest that revision of this genus is required. • We observed the evolutionary trend from free carpels to fused carpels within this single genus • In addition to a revised taxonomic treatment and reconstructed biogeographic and evolutionary scenarios, our work will contribute important new information relevant to the on-going debate about the extent and duration of the Oligocene drowning of New Zealand and help address a much-debated question regarding the origin of these taxa: are they continuously inhabiting ancient lineages or is their modern presence the result of more recent long-distance dispersal?

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