In populations of four species of Palicourea and Psychotria, we quantified reciprocity using adaptive inaccuracy and measured the stigmatic lobe length to estimate how these traits influenced legitimate pollen deposition.
Deviations from reciprocity can negatively affect the rates of legitimate pollen deposition, but other floral traits or the pollination environment might contribute to the function of distyly. The function of the reciprocal position of anthers and stigmas of the floral morphs in distylous flowers is to promote cross-pollination between morphs (legitimate pollination).
The partitioning of morphological traits between syntopic species might facilitate the differential placement of pollen on the body of the pollinator and reduce the chances of interspecific interference. legitimate organ correspondence) in comparison to intraspecific intra-morph, interspecific syntopic and interspecific non-syntopic combinations. Additionally, reciprocity of sexual organs was more accurate in intraspecific inter-morph combinations (i.e. However, we found a higher overlap involving the non-syntopic species, especially between Palicourea rigida and Palicourea marcgravii. The position of sexual organs was, in most cases, partitioned between syntopic populations, with low overlap in anther and stigma heights. The three species overlapped in their distributions and flowering periods. We compared the distribution, flowering phenology, floral measurements and reciprocity of sexual organ heights of two syntopic species (Palicourea rigida and Palicourea coriacea) and one non-syntopic congener (Palicourea marcgravii). We tested these assumptions using a set of Palicourea (Rubiaceae) species as a model system. This led us to hypothesize that such partitioning should be more accurate among distylous syntopic species in comparison to combinations with other related plants that do not co-occur. Owing to differences in the heights of stigmas and anthers, each floral morph must place pollen onto two distinct parts of the body of the pollinator. Morphological niche partitioning between related syntopic plants that are distylous (with short- and long-styled morphs) is complex. padifolia resulted in significant differences in fruit production between floral morphs, independent of pollination treatment and pollinator species short-styled flowers proportionately developed almost twice the number of fruits developed by long-styled flowers. However, the species of hummingbird was marginally significant in explaining variation in pollen deposition on stigmas. Stigmatic pollen loads under field conditions and those after controlled hummingbird visitation, along with rates of pollen accumulation through the day indicated that stigmas of short-styled flowers receive proportionately more legitimate (intermorph) pollen grains than did those of long-styled flowers. Hummingbird visitation rates did not differ significantly between floral morphs, and foraging movements from focal plants towards neighboring plants were independent of floral morph. The shape and orientation of the stigma lobes differed between morphs and were significantly longer among short-styled flowers. Anthers of long-styled flowers contained significantly more and smaller pollen grains than those of short-styled flowers, independently of corolla and anther lengths. A pollination experiment with stuffed hummingbirds that varied in bill size was done to evaluate the contribution of bill variation toward differences between floral morphs in pollen receipt and pollen transfer and female reproductive output. Differences in pollen and stigma morphology, pollen flow, rates of pollen deposition, and/or stigmatic pollen loads were then evaluated for their contribution toward differences in reproductive output between floral morphs. To determine the effectiveness of hummingbirds as pollen vectors between floral morphs and the consequences in terms of male (pollen transfer) and female function (pollen receipt) in Palicourea padifolia (Rubiaceae), floral visitors, their foraging modes, and temporal patterns of floral visitation were observed and documented. However, pollen loads on stigmas can only provide moderate support for Darwin's hypothesis of the promotion of legitimate crosses. The adaptiveness of distyly has been typically investigated in terms of its female function, specifically pollen receipt.
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