Intraspecific divergence and convergence of floral tube length in specialized pollination interactions

Floral tubes are often thought to be a consequence of adaptive specialization towards pollinator morphology. We explore floral tube length evolution within Tritoniopsis revoluta (Iridaceae), a species with considerable geographical tube length variation. We ask whether tube lengths of T. revoluta po...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2014-11, Vol.281 (1795), p.20141420-20141420
Main Authors: Anderson, B., Ros, P., Wiese, T. J., Ellis, A. G.
Format: Article
Language:English
Subjects:
Animals
Bees - anatomy & histology
Bees - physiology
Biological Evolution
Cape Flora
Diptera - anatomy & histology
Diptera - physiology
Directional Evolution
Flowers - anatomy & histology
Iridaceae
Iridaceae - anatomy & histology
Iridaceae - physiology
Phylogeny
Pollination
Pollinator Ecotype
Pollinator Specialization
South Africa
Special Feature
Trait Matching
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Summary:Floral tubes are often thought to be a consequence of adaptive specialization towards pollinator morphology. We explore floral tube length evolution within Tritoniopsis revoluta (Iridaceae), a species with considerable geographical tube length variation. We ask whether tube lengths of T. revoluta populations are associated with pollinator proboscis lengths, whether floral divergence occurs in the presence of different pollinators and whether floral convergence occurs between distantly related populations pollinated by the same pollinator. Finally, we ask whether tube length evolution is directional. Shifts between morphologically different pollinators were always associated with shifts in floral morphology, even when populations were very closely related. Distantly related populations had similar tube lengths when they were pollinated by the same pollinator. Shifts in tube length tended to be from short to long, although reversals were not infrequent. After correcting for the population-level phylogeny, there was a strong positive, linear relationship between floral tube length and pollinator proboscis length, suggesting that plants are functionally specialized on different pollinators at different sites. However, because tube length evolution in this system can be a bidirectional process, specialization to the local pollinator fauna is unlikely to result in evolutionary or ecological dead-ends such as canalization or range limitation.
ISSN:0962-8452
1471-2945
1471-2954
DOI:10.1098/rspb.2014.1420