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Abstract Detail



Paleobotanical Section

Ranks, Stephanie [1], Contreras, Dori [1], Marshall, Charles R. [1], Looy, Cindy V [1].

Autorotating winged seeds: what they tell us about tree height in extant and fossil conifers.

The earliest known single-winged conifer seeds appear in the Early Permian. They belong to the Majonicaceae (voltzian conifers), which are known only from lateral shoots and reproductive structures. Currently, there are no fossils that provide direct evidence of the full height of these trees. Because extant single-winged seeds all autorotate, it can be assumed that the fossil single-winged seeds did so as well. Autorotating seeds are an adaptation to increase dispersal distance, but the seeds need to fall for a certain distance before they can achieve the steady state rotation necessary to slow descent. Thus, the presence of winged seeds in the Majonicaceae suggests that they may have been tall trees. To test this hypothesis, we investigated the relationship between single-winged autorotating seeds and maximum tree height among living taxa by mapping seed type and tree height onto a conifer phylogeny. Data were collected for 489 taxa, some 64% of all living conifers. The analysis reveals that the vast majority of species today that produce single-winged autorotating seeds are taller than 20 m. Thus it seems highly likely that the voltzians with single-winged seeds were also taller trees. Interestingly, a separate phylogenetic analysis also reveals that autorotating single-winged seeds evolved multiple times among living conifers: once within the Pinaceae, where the seed wing is derived from the ovuliferous scale, and several times outside the Pinaceae, where the seed wing is derived from the integument. The independent evolution of nearly identical morphotypes by different developmental mechanisms indicates that the functional demands of slowing seed descent via single-wing autorotation are very strong. The morphological similarities between the voltzian and extant single-winged seeds indicates the fossil taxa likely had similar function and constraints as the living taxa, and therefore were likely also derived from tall trees.

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1 - University of California-Berkeley, Department of Integrative Biology and Museum of Paleontology, 3060 Valley Life Sciences Bldg #3140, Berkeley, CA, 94720, USA

Keywords:
Conifer
winged seed
autorotation
Permian
phylogeny.

Presentation Type: Oral Paper:Papers for Sections
Session: 3
Location: Melrose/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 10:15 AM
Number: 3008
Abstract ID:834
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award


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