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Distyly has been interpreted as a mechanism that promotes cross-pollination between floral morphs. According to this hypothesis, pollen from anthers positioned at different heights could adhere to different body parts of the pollinator that would correspond to those points where stigmas of compatible morph contact the animal. In this regard, hummingbird species with different bill sizes may play different roles as pollinators of each morph. If pollinators mobilize more legitimate pollen towards one of the two morphs, gender specialization may occur. This work aimed to assess experimentally the role of long- and short-billed hummingbirds as pollinators of short-style (SS) and long-style (LS) flowers of Palicourea demissa, a distylous, hummingbird-pollinated treelet in Venezuelan cloud forests. Flowers were emasculated and exposed to a single visit of the hummingbird Coeligena torquata (long-billed), Heliangelus spencei (short-billed) or Adelomyia melanogenys (short-billed). Later, stigmas were removed, and pollen load counted under a microscope to calculate the probability of legitimate- and illegitimate-pollen transfer by hummingbirds. The probability analyses of pollen transference showed that short-billed hummingbirds have higher pollination probabilities from SS-anthers to LS- and SS-stigmas, and from LS-anther to LS-stigmas than from LS-anther to SS-stigmas. In contrast, long-billed hummingbirds have higher probabilities of pollen transference from LS-anthers to SS-stigmas than in other directions. A deeper view of the sexual expression of each morph in P. demissa will depend on future studies that determine possible morpho-differences in the biological function of male and female floral structures, and the role played by less frequent floral visitors as mediators of legitimate pollination between floral morphs. [ABSTRACT FROM AUTHOR]

Pigment patterns in corollas are common, and act as nectar guides for pollinators. We discovered multiple floral morphs of Justicia adhatoda L. (Acanthaceae) with variable extents of corolla vein pigmentation in a population in Sariska, Rajasthan. Two floral morphs, one completely white and the other white with dark purple vein pigmentation, were compared in order to investigate any possible differences relating to: (a) corolla surface structure, (b) pollinator visitation, (c) reward for the pollinator, and (d) fitness parameters in the morphs. Both morphs showed similar UV reflectance, had distally located conical cells in petals, indicated similar pollinator visitation and had similar nectar content. Contrastingly, seed germination and seed weight were significantly higher in the purple-veined morph, while fruit set and seed set were higher in the white morph which also showed higher amounts of saturated fatty acids in the seeds. The results about aborted seeds differed inconsistently. Thus, variation in corolla pigmentation in J. adhatoda suggests fitness trade-off between the morphs with higher fruit and seed set, but lower seed germination and seed weight in the white morph compared to the purple-veined. We are led to the possibility of different selective pressures acting on the morphs and resulting in adaptive polymorphism. [ABSTRACT FROM AUTHOR]

Oxalis pes- caprae, a tristylous flowering plant native to South Africa, is described in the western Mediterranean basin as an asexual-only 5 x short-styled morph (5 x S-morph) invasive weed losing all mating partners after introduction. The objective of this study was to reassess the patterns of floral morph and cytotype distribution and the sexual reproduction ability in this invaded range. For that, floral morph and cytotype composition were evaluated in 39 populations of O. pes- caprae in a methodical sampling. The reproductive success of natural populations was assessed as fruit and seed production and seed germination for all floral morphs and cytotypes detected. Self- and morph-incompatibility were also studied with controlled hand pollinations. A remarkable diversity in floral morph and cytotype composition was observed. Furthermore, we observed successful sexual reproduction in several localities across the surveyed area. The S-morph is still dominant in this invaded area, and although it was mostly 5 x, an additional cytotype (4 x) was also recorded. Records of both a mid-styled morph (M-morph) and an area with trimorphic populations of this species are reported here for the first time in the invasive range of the Mediterranean basin. The long-styled morph appears to occur randomly across the surveyed area, while the M-morph is concentrated mainly in Estremadura province (Portugal), where a breakdown in the incompatibility system was observed. These distribution patterns may result from events of sexual reproduction after incompatibility breakdown and/or from multiple introduction events from the native area. The ability to reproduce sexually, undetected so far, may have important impacts in the population dynamics and major consequences for the adaptation and selection potential of O. pes- caprae in this invaded area. [ABSTRACT FROM AUTHOR]