Abstract Detail

Reproductive biology

Diedrich, John [1], Leslie, Andrew [2].

Cone scale shape determines seed wing morphology in Pinaceae.

The seeds of many species in the Pinaceae family of conifers have conspicuous wings, which aid in wind dispersal by causing falling seeds to autorotate and thus lowering their settling velocity. These wings show a wide variety of shapes across Pinaceae species and genera, and understanding the origin of these differences is important because seed wings may contain useful systematic characters for both living and fossil species. Differences in Pinaceae seed wing morphology may reflect optimization for specific aerodynamic properties, although alternatively, their shape may reflect seed cone morphology and have little association with aerodynamics. This is because Pinaceae wings are unique in being formed through the abscission of the upper surface of the cone scale that supports the seeds, which means the shape of the wing may simply mirror the shape of the cone scales. In this study, we test which of these two factors is more important in determining wing shape within Pinaceae. We quantified seed wing size and shape in 154 species from 11 genera using traditional linear measurements, and we specifically analyzed wing outline using Elliptical Fourier Descriptors. Wherever possible, we also measured linear dimensions of the cones and cone scales that produced the seeds. We then measured the settling velocity of 20 artificial seed models with different wing morphologies in order to test if seed shape was related to aerodynamic properties. When analyzed within the context of a large Pinaceae phylogeny, our results show a strong correlation between wing shape and cone scale shape, consistent with expectations from seed development. Aerodynamic tests showed no significant relationship between wing morphology and settling velocity, suggesting that the shapes of specific Pinaceae seeds are unlikely to reflect selection for more efficient seed dispersal by wind. Although more detailed aerodynamic modeling is needed, our results suggest that the diversity of Pinaceae seed morphologies is mostly due to the diversity of Pinaceae cone scales, which in turn reflect the many different ways in which the group constructs its seed cones. The extent to which seed wing morphology is useful as a phylogenetic character is therefore closely related to the extent to which cone scale shape is useful.

1 - Brown University, Ecology and Evolutionary Biology, 80 Waterman Street, Providence, RI, 02912, USA
2 - Brown University, Ecology and Evolutionary Biology, Box G-W, 80 Waterman Street, Providence, RI, 02912, USA

Keywords:
conifers
morphometric analysis
character correlation
Seed dispersal.

Presentation Type: Oral Paper
Session: 42, Reproductive Biology
Location: 205/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 11:30 AM
Number: 42006
Abstract ID:268
Candidate for Awards:None