PUBLICATIONS

Looy CV and Stevenson R 2014. Earliest occurrence of autorotating seeds in conifers: the mid-Permian (Kungurian-Wordian) Manifera talaris sp. nov. International Journal of Plant Sciences 75: 841-854.

Abstract

Abstract.—Manifera talaris, a voltzian conifer from the late early to middle Permian (~270 Ma) of Texas, is the earliest known conifer to produce winged seeds indicative of autorotating flight. In contrast to autorotating seeds and fruits of extant plants, the ones of M. talaris are exceptional in that they have variable morphology. They bore two wings that produced a range of wing configurations, from seeds with two equal-sized wings to single-winged specimens, via various stages of underdevelopment of one of the wings. To examine the effects of various seed morphologies on aerodynamics and dispersal potential, we studied the flight performance of paper models of three morphotypes: symmetric double-winged, asymmetric double-winged, and single-winged. Using a high-speed camera we identified the mode of descent (plummeting, gliding, autorotation), quantified descent speed, autorotation frequency, and other flight characteristics. To validate such modeling as an inferential tool, we compared descent of extant analogs (kauri; Agathis australis) to descent of similarly constructed seed models. All three seed morphotypes exhibited autorotating flight behavior. However, double-winged seeds, especially symmetric ones, failed to initiate slow autorotative descent more frequently than single-winged seeds. Even when autorotating, symmetric double-winged seeds descend faster than asymmetric double-winged ones, and descent is roughly twice as fast compared to single-winged seeds. Moreover, the relative advantage that (effectively) single-winged seeds have in slowing descent during autorotation becomes larger as seed weight increases. Hence, the range in seed wing configurations in M. talaris produced a wide variation in potential dispersal capacity. Overall, our results indicate that the evolutionarily novel autorotating winged seeds must have improved conifer seed dispersal, in a time when animal vectors for dispersion were virtually absent. Due to the range in wing configuration, the early evolution of autorotative flight in conifers was a functionally imperfect one, which provides us insight into the evolutionary developmental biology of autorotative seeds in conifers.