Nature 441, 337-340 (18 May 2006) | doi:10.1038/nature04690; Received 9 January 2006; Accepted 1 March 2006

Embryological evidence for developmental lability during early angiosperm evolution

William E. Friedman1

  1. Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado 80309, USA

Correspondence to: William E. Friedman1 Correspondence and requests for materials should be addressed to W.E.F. (Email: ned@colorado.edu).

Recent advances in angiosperm phylogeny reconstruction1, 2, 3, palaeobotany4, 5 and comparative organismic biology6, 7, 8 have provided the impetus for a major re-evaluation of the earliest phases of the diversification of flowering plants. We now know that within the first fifteen million years of angiosperm history, three major lineages of flowering plants—monocotyledons, eumagnoliids and eudicotyledons—were established5, and that within this window of time, tremendous variation in vegetative and floral characteristics evolved. Here I report on a novel type of embryo sac (angiosperm female gametophyte or haploid egg-producing structure) in Amborella trichopoda, the sole member of the most ancient extant angiosperm lineage. This is the first new pattern of embryo sac structure to be discovered among angiosperms in well over half a century. This discovery also supports the emerging view9, 10, 11, 12 that the earliest phases of angiosperm evolution were characterized by an extensive degree of developmental experimentation and structural lability, and may provide evidence of a critical link to the gymnospermous ancestors of flowering plants.


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