Journal Article

Dormancy as exaptation to protect mimetic seeds against deterioration before dispersal

Pedro H. S. Brancalion, Ana D. L. C. Novembre, Ricardo R. Rodrigues and Júlio Marcos Filho

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 105, issue 6, pages 991-998
Published in print June 2010 | ISSN: 0305-7364
Published online March 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq068
Dormancy as exaptation to protect mimetic seeds against deterioration before dispersal

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Mimetic seeds simulate the appearance of fleshy fruits and arilled seeds without producing nutritive tissues as a reward for seed dispersers. In this strategy of seed dispersal, seeds may remain attached to the mother plant for long periods after maturity, increasing their availability to naïve seed dispersers. The hypothesis that seed coat impermeability in many tropical Fabaceae with mimetic seeds serves as an exaptation to protect the seeds from deterioration and rotting while awaiting dispersal was investigated.

Methods

Seed coat impermeability was evaluated in five mimetic-seeded species of tropical Fabaceae in south-eastern Brazil (Abarema langsdorffii, Abrus precatorius, Adenanthera pavonina, Erythrina velutina and Ormosia arborea) and in Erythrina speciosa, a ‘basal’ species in its genus, which has monochromatic brown seeds and no mimetic displays. Seed hardness was evaluated as a defence against accelerated ageing (humid chamber at 41 °C for 144 h). Seed development and physiological potential of O. arborea was evaluated and the effect of holding mature seeds in pods on the mother plant in the field for a period of 1 year under humid tropical conditions was compared with seeds stored under controlled conditions (15 °C and 40 % relative air humidity).

Key Results

All five mimetic-seeded species, and E. speciosa, showed strong coat impermeability, which protected the seeds against deterioration in accelerated ageing. Most O. arborea seeds only became dormant 2 months after pod dehiscence. Germination of seeds after 1 year on the plant in a humid tropical climate was 56 %, compared with 80 % for seeds stored in controlled conditions (15 °C, 45 % relative humidity). Seedling shoot length after 1 year did not differ between seed sources.

Conclusions

Dormancy acts in mimetic-seeded species as an exaptation to reduce seed deterioration, allowing an increase in their effective dispersal period and mitigating the losses incurred by low removal rates by naïve avian frugivores.

Keywords: Ormosia arborea; seed coat impermeability; seed hardness; seed development; seed adaptive traits; seed physiology; adaptation; frugivory

Journal Article.  5515 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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