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Abstract Detail

Reproductive biology

Leslie, Andrew B. [1], Beaulieu, Jeremy M. [2].

Dispersal Biology and the Evolution of Seed Size in Conifers.

The evolution of seed size in plants reflects many influences, including factors as diverse as genome size to life history strategies to dispersal ecology. Teasing apart the relative importance of these can be difficult, and here we use conifers as a study group to investigate the importance of seed dispersal biology in the evolution of seed size. Conifers include approximately 605 living species with a global distribution from the tropics to boreal forests, and the phylogenetic relationships and dispersal ecologies among these species are reasonably well known. Living conifer species predominantly use one of two modes to disperse their seeds, either wind (~52% of species) or animals (~47% of species), and animal dispersed seeds are likely to be larger than wind dispersed seeds. To explicitly test the relationship between these dispersal modes and seed size, we used a dataset of seed and seed cone sizes for nearly all extant conifer species based on published sources and direct measurements from herbarium specimens. We coupled this data set with a time-calibrated phylogeny that samples 545 species (~90% of extant diversity), as well as several additional species traits that may be correlated with seed size, including genome size and general climate regime. An analysis of these data using phylogenetic regression techniques and likelihood-based models of character evolution indicates that the strongest influences on seed size are dispersal syndrome, clade identity, and to a lesser extent, genome size. Seed size shows no significant relationship with climatic variables such as temperature and precipitation when analyzed across all conifers. Our results suggest that conifers exhibit three distinct seed size regimes: abiotically dispersed seeds tend to be small, biotically dispersed seeds where attractant tissues (such as fleshy or succulent cone scales) subtend the seed are slightly larger, and biotically dispersed seeds where the attractant tissues are either the seed itself or tissues directly fused to the seed are much larger. This suggests that the exact way in which seeds are dispersed by animals is as important as the distinction between abiotic and biotic dispersal strategies. Finally, seed sizes are also generally different among the major conifer clades, which likely relates to basic differences in plant architecture and seed cone construction. These basic architectural differences interact with differences in dispersal biology to generate the distribution of seed sizes observed in living conifers.

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1 - Brown University, Box G-W, 80 Waterman Street, Providence, RI, 02912, USA
2 - University of Tennessee, National Institute for Mathematical and Biological Synthesis, 1122 Volunteer Blvd, Knoxville, TN, 37996, USA

genome size
Dispersal patterns
animal dispersal.

Presentation Type: Oral Paper:Papers for Topics
Session: 2
Location: Salon 1/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 10:15 AM
Number: 2008
Abstract ID:400
Candidate for Awards:None

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