Stabilizing selection on nectar concentration in wild Petunia axillaris, as revealed by genetic analysis of pollen dispersal

GABRIELA GLEISER; ANTONINA I. INTERNICOLA; FRÉDÉRIC AUSTERLITZ; GIORGINA BERNASCONI

EVOLUTIONARY ECOLOGY

SPRINGER

Año: 2014 vol. 28 p. 869 - 884

0269-7653

Most animal-pollinated plants produce nectar as a pollinator reward. Despitethe main role that nectar plays in plant-pollinator interactions, the impact of natural variation in nectar traits on realized male fitness is poorly known. Here, we assessed thisrelation for a wild Petunia axillaris population using paternity-based direct selectiongradient analysis, which allowed us also to infer pollen dispersal patterns. Because malefecundity may depend on other traits which could be associated with nectar characteristics(i.e. volume and concentration), we also considered selection on other key reproductivetraits. The analysis revealed that P. axillaris was a strict outcrosser, but that successfulpollination occurred mainly among neighbours. Individual plants varied greatly in theirmale fecundity. Nectar concentration, a key feature of nectar that determines its profitability,was subjected to stabilizing selection. Selection through male function also affectedcorolla area (positive directional selection), corolla tube length (negative directionalselection), and floral display size (stabilizing selection), but none of these traits werephenotypically correlated with nectar characteristics. Because nectar concentration affectsthe ability and foraging efficiency of different flower visitors to feed on nectar, stabilizingselection may reflect either the preference of the most effective pollinators, or antagonisticselection driven by pollinators and non-pollinating nectar consumers.