Abstract Detail



Macroevolution

Leslie, Andrew [1], Mander, Luke [2].

Functional diversity, transference of function, and complexity in vascular plant reproductive structures.

The complexity of vascular plant reproductive structures appears to have generally increased over time, from the simple sporangia of Silurian taxa to the intricate contraptions of angiosperms. This overarching pattern likely reflects more diverse functional demands on the reproductive structures of some lineages, combined with increased morphological and anatomical specialization in how these demands are met. But understanding exactly how complexity has changed through time, and how that may relate to differences in function, is challenging because plant groups produce disparate reproductive structures that are difficult to compare. Here we quantify changes in reproductive complexity across pteridophytes, gymnosperms, and angiosperms using two simple aspects that can be applied to any lineage: the total number of parts, or geometrically distinct morphological features, and the degree to which these parts are repeated. We ask how the number and arrangement of parts has changed over time and across lineages with different reproductive biology and functional demands. We find a rapid initial rise in complexity from the Late Silurian to the Late Devonian, as many lineages evolved a basic set of structures that support and protect sporangia, followed by a gradual rise in maximum part number to the Early Cretaceous associated with diversification in seed plant ovulate structures. Lastly, the appearance of derived angiosperm clades over the middle Cretaceous is association with an additional sharp rise in part number. Within this overarching pattern, complexity is generally associated with functional diversity; reproductive structures in both pteridophytes and seed plants that have simple functional roles, such as wind dispersal of spores or pollen, have relatively few parts. Seed plant ovulate structures, which perform a greater variety of functional roles, generally have more parts. These patterns reflect a basic tendency for reproductive functions in vascular plants to be transferred away from fertile organs and onto surrounding sterile organs, whose specialization then underlies the patterns of complexity that we identify here. The extent to which this process occurs, however, is determined by the overall functional diversity of the reproductive structures, resulting in different patterns of morphological complexity and disparity across plant lineages.  


1 - Stanford University, Geological Sciences, 450 Jane Stanford Way, Building 320, Room 118, Stanford, CA, 94305, United States
2 - The Open University, School of Environment, Earth & Ecosystem Sciences, Milton Keynes, UK

Keywords:
complexity
vascular plants
reproductive biology
reproductive morphology.

Presentation Type: Oral Paper
Number: MACRO1005
Abstract ID:820
Candidate for Awards:None


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