Flower reshaping in the transition to hummingbird pollination in Loasaceae subfam. Loasoideae despite absence of corolla tubes or spurs.

STRELIN, M.; BENITEZ-VIEYRA, S.; ACKERMAN, M.; COCUCCI A. A.

EVOLUTIONARY ECOLOGY

SPRINGER

Lugar: Berlin; Año: 2016

0269-7653

p { margin-bottom: 0.25cm; line-height: 120%; }Many angiospermlineages present transitions from bee to hummingbird pollination. Theflower design in most of these lineages includes either corolla tubesor nectar spurs, structures that commonly experienced an elongationwith the acquisition of hummingbird pollination. It is proposed thatthis increases the fit between the bird head and flower structures,and isolates or partially blocks bees from the interaction. But canthis transition occur if the ancestral flower design lacks tubes orspurs? Here we focus on the transition from bee to hummingbirdpollination in the Loasaceae subfamily Loasoideae. Loasoideae flowershave radial corollas with separated petals; therefore, they do notdisplay corolla tubes nor nectar spurs. These flowers also present awhorl of nectar scales and staminodes, unique to the subfamily, whichis involved in flower?pollinator fit and in nectar harvesting. Toexplore flower shape adaptation to hummingbird pollination, we testedfor correspondence between pollinators and flower shape inLoasoideae. In order to achieve this, we first compared theevolutionary history of flower phenotype and pollination mode, andthen used stochastic character mapping and geometric-morphometricvariables in a comparison of alternative evolutionary models. Theresults of our study suggest that the transition from bee to birdpollination was accompanied by changes in the shape of thestaminodial complex, along with the evolution of relatively closedcorollas. Moreover, while bird pollination seems to be the endpoint in the evolution of pollination syndromes in many angiospermlineages, rodent pollinated flowers probably evolved from ancestralbird pollinated flowers in Loasoideae. Our findings suggest that theevolution of bird pollinated flowers from ancestral bee pollinatedflowers does not require the presence of corolla tubes or spurs, andcan take place as long as the flower design includes structuresparticipating in flower?pollinator fit.