Abstract Detail

Anatomy and Morphology

Losada, Juan M [1], Leslie, Andrew B [2].

Functional Morphology, Morphological Disparity, and Heterochrony in Conifer Seed Cone Evolution.

Conifer seed cones perform a series of discrete functions over their ontogeny, first facilitating the capture of windborne pollen, then protecting maturing seeds, and finally aiding in the dispersal of mature seeds. Cones perform these functions with the same basic structure, meaning that specific patterns of growth and development in different parts of the cone are crucial for changing its shape in order to meet these different demands. Observed disparity among conifer seed cones then presumably reflects differences in growth patterns, which generate different specific morphological solutions to the same general functional demands of pollination, protection, and dispersal. We investigated this by focusing on two species in the Pinaceae clade of conifers, Abies koreana and Picea jezoensis, which differ significantly in their cone morphology at pollination. Both species produce pollination-stage cones that look superficially similar and likely function in the same way, but which are built differently: in Picea cones consist of elongated ovuliferous scales while in Abies the bracts that subtend the ovuliferous scales are much longer and better developed. We used traditional sectioning and staining techniques, as well as confocal microscopy, to track the development of the bracts and ovuliferous scales from bud initiation through pollination in order to identify shifts in the timing and location of cell expansion and cell proliferation within the context of their function. Both Abies and Picea follow the same developmental sequence: bracts development first but then cease growing, at which point ovuliferous scales rapidly enlarge and expand. The taxa differ, however, in the relative rate of this process: in Picea, development occurs quickly and pollination occurs during the initial expansion of the ovuliferous scale, while in Abies, development occurs more slowly and pollination occurs during the maximum development of the bract but prior to the expansion of the ovuliferous scale, which only occurs following pollination. These results show how slight heterochronic shifts in the same basic developmental sequence can lead to very different morphologies, which nonetheless perform a basically similar function (i.e., facilitating wind pollination). Differences in the timing and location of cell expansion and proliferation, therefore provide a mechanism to explain broader patterns of morphological disparity among conifer seed cones.

1 - Brown University, Ecology and Evolutionary Biology, 80 Waterman St., Providence, RI, 02912, USA
2 - Brown University, 80 Waterman St., Providence, RI, 02912, United States

Keywords:
gymnosperms
conifers
seed cone
heterochrony
Diversification.

Presentation Type: Oral Paper
Session: 20, Anatomy and Morphology
Location: Fort Worth Ballroom 7/Omni Hotel
Date: Tuesday, June 27th, 2017
Time: 10:45 AM
Number: 20011
Abstract ID:334
Candidate for Awards:None