Hummingbird pollination in Salvia haenkei (Lamiaceae) lacking the typical lever mechanism (original) (raw)
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Ecoscience, 2007
Distylous polymorphisms represent a useful model system for studying the functioning of flower morphology because floral morphs have reciprocal flower developmental pathways and co-occur in the same environment such that they share the same pollinators. Distylous plants typically display both reciprocal herkogamy and a heteromorphic incompatibility system, which allows mating only between morphs. In this paper, we document morph-specific patterns in floral morphology and pollen receipt of Palicourea padifolia, a hummingbird-pollinated shrub. Floral traits typically associated with the functioning of distyly, reciprocal herkogamy, and population morph ratios of flowering individuals from 10 populations were measured and quantified. Pollen receipt on stigmas of the same measured flowers was then used to determine the effectiveness of distyly in promoting disassortative pollen transfer. Pollen of long-styled flowers was more effective in reaching legitimate stigmas, while short-styled morphs were more successful in the reception of legitimate pollen across populations. Variation in pollen receipt across populations was not explained by reciprocal herkogamy, which typically promotes legitimate pollination. Natural pollination resulting in a higher proportion of legitimate pollen in short-styled flowers increased with stigma-anther separation (promotion of outcross pollination) and width of corolla entrance (avoidance of self-pollination).
Annals of botany, 2010
The period between the beginning of anthesis and flower senescence modulates the transport of pollen by pollinators among conspecific flowers, and its length may therefore influence reproductive success. This study evaluated whether floral longevity favours pollen removal from the anthers over fecundity (seed set) in an ornithophilous species that does not undergo pollen limitation. Field investigations were conducted on floral longevity, nectar production, pollinator behaviour, and variations in fruit set (FS), mean number of seeds per fruit (MSF) and pollen removal by hummingbirds (PR) during the anthesis of Salvia sellowiana in south-east Brazil. Anthesis of flowers exposed to pollinators lasted 4 d, as well as on flowers with pollen removed from the anthers or deposited on the stigma. The longevity of bagged flowers was significantly higher (approx. 9 d). FS and PR reached 87.2 and 90 %, respectively, in natural conditions. PR increased gradually over the period of anthesis; how...
Rodriguésia, 2016
Hummingbirds are the most important group of pollinating birds in the Neotropics and tend to use, concomitantly, more than one plant species as food source. Pollen may be mixed on hummingbirds' body due to the visits to different plant species; therefore, these birds may promote heterospecific pollen deposition (HPD). The hummingbirds potential to promote HPD, the occurrence of HPD and its implications in plant reproduction are scarcely known in the Atlantic Forest. We have studied the transport of pollen by three hummingbird species from the Brazilian Atlantic Forest. We have also checked the actual HPD occurrence under natural conditions in two plant species, namely Canistropsis seidelii and Psychotria nuda. Moreover, we investigated Nidularium innocentii reproductive system evaluating the effect of HPD on its reproduction by simulating a pollen mixture pollination. We found hummingbirds transporting heterospecific pollen mixtures on their bodies, which in turn were deposited ...
Oecologia, 1987
In the Monteverde (Costa Rica) cloud forest, the distylous treelet Palicourea lasiorrachis (Rubiaceae) is pollinated by the hummingbird Lampornis calolaema. Only intermorph pollinations result in seed set. In a series of 47 experimental trials, we compared pollen carryover from thrum (short-styled) flowers to pin (long-styled) flowers with carryover from pin to thrum flowers. In one experiment, captive L. calolaema first probed 2 flowers of one style morph, then a series of 20 flowers of the other style morph. In the second experiment, 2 flowers of a frequent associate of P. lasiorrachis, the treelet Cephaelis elata (Rubiaceae), intervened between donor and recipient Palicourea flowers. We assessed intermorph pollinations by counting pollen tubes in recipients' styles. Without Cephaelis intervening, thrum donors transferred many fewer total grains to pins than did pin donors to thrums. However, thrum grains were dispersed more evenly among recipient pin flowers than were pin grains among thrum recipients. As a result, the potential for paternal reproductive success was at least as great for thrum flowers as for pins. With insertion of Cephaelis flowers into the foraging sequence, the magnitude of differences between carryover patterns declined.
Pollen Transfer by Hummingbirds and Bumblebees, and the Divergence of Pollination Modes In Penstemon
Evolution, 2003
We compared pollen removal and deposition by hummingbirds and bumblebees visiting bird-syndrome Penstemon barbatus and bee-syndrome P. strictus flowers. One model for evolutionary shifts from bee pollination to bird pollination has assumed that, mostly due to grooming, pollen on bee bodies quickly becomes unavailable for transfer to stigmas, whereas pollen on hummingbirds has greater carryover. Comparing bumblebees and hummingbirds seeking nectar in P. strictus, we confirmed that bees had a steeper pollen carryover curve than birds but, surprisingly, bees and birds removed similar amounts of pollen and had similar per-visit pollen transfer efficiencies. Comparing P. barbatus and P. strictus visited by hummingbirds, the bird-syndrome flowers had more pollen removed, more pollen deposited, and a higher transfer efficiency than the bee-syndrome flowers. In addition, P. barbatus flowers have evolved such that their anthers and stigmas would not easily come into contact with bumblebees if they were to forage on them. We discuss the role that differences in pollination efficiency between bees and hummingbirds may have played in the repeated evolution of hummingbird pollination in Penstemon.
Functional implications of the staminal lever mechanism in Salvia cyclostegia (Lamiaceae)
Annals of botany, 2011
Flower morphology and inflorescence architecture affect pollinator foraging behaviour and thereby influence the process of pollination and the reproductive success of plants. This study explored possible ecological functions of the lever-like stamens and the floral design in Salvia cyclostegia. Flower construction was experimentally manipulated by removing either the lower lever arms or the upper fertile thecae of the two stamens from a flower. The two types of manipulated individuals were intermixed with the control ones and randomly distributed in the population. Removing the sterile lower lever arms significantly reduced handling time per flower of the main pollinator, Bombus personatus. Interestingly, this manipulation did not increase the number of flowers probed per plant visit, but instead reduced it, i.e. shortened the visit sequence of the bumble-bees. Both loss of staminal lever function by removing lower lever arms and exclusion of self pollen by removing upper fertile th...
Specialized use of pollen vectors by Caesalpinia gilliesii, a legume species with brush-type flowers
Biological Journal of the Linnean Society, 2006
The pollination of Caesalpinia gilliesii (Fabaceae) , a legume species with long, brush-type flowers, was studied in wild populations in Argentina. A total of 341 hawkmoths (Sphingidae), belonging to 10 species, with tongues ranging from 1.5 to 13.5 cm in length, were captured by means of light traps. Hawkmoths could be classified in four significantly different tongue-length classes or guilds: short (15.35 ± 1.11 mm), medium (30.23 ± 2.24 mm), long (55.85 ± 4.98 mm) and very long (95.61 ± 13.63 mm). A total of 133 of the hawkmoths, belonging to seven species, carried pollen of Cae. gilliesii , mainly on their venter. Successful contact with anthers while drinking nectar depended upon hawkmoth tongue length. The relative frequency of pollen-carriage and the mean tongue length of each species were positively and significantly correlated. Considering a null hypothesis of nonspecialization, in which hawkmoths carrying pollen are distributed at random among individuals of the four guilds, long-tongued hawkmoths carried Cae. gilliesii pollen more frequently than would be expected by chance. In contrast, short-and medium-tongued guilds carried pollen less frequently than is predicted by random expectation. Individuals with short tongues accessed nectar from below without touching the anthers, whereas very long-tongued hawkmoths, with tongues longer than the length range of the flower reproductive organs, can probably reach nectar without touching the fertile organs. Results show that a pterotribic pattern of pollen deposition on the body of long-tongued hawkmoths is operating in this species. This suggests that brush-type blossoms are not necessarily unspecialized, despite popular belief.
American Journal of Botany, 2004
The adaptiveness of distyly has been typically investigated in terms of its female function, specifically pollen receipt. However, pollen loads on stigmas can only provide moderate support for Darwin's hypothesis of the promotion of legitimate crosses. 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. 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. 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. Anthers of long-styled flowers contained significantly more and smaller pollen grains than those of short-styled flowers, independently of corolla and anther lengths. The shape and orientation of the stigma lobes differed between morphs and were significantly longer among short-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. 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. However, the species of hummingbird was marginally significant in explaining variation in pollen deposition on stigmas. Lastly, intermorph pollinations of P. 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.
New insights into the functional morphology of the lever mechanism of Salvia pratensis (Lamiaceae)
Annals of botany, 2007
The functional morphology of Salvia pratensis flowers was re-investigated, after new insights revealed that pollen dispensing is one of the main functions of the staminal lever. In particular, no detailed information was available regarding the process of pollen transfer and the forces arising between the pollen-bearing thecae and the pollinating bee's body. The assumption was made that these forces play a significant role in pollen dispensing. The functional morphology of S. pratensis flowers and the interaction between flowers and bees (Apis mellifera) were studied by reconstructing stress and strains by using qualitative and semi-quantitative theoretical analysis. Flowers were manipulated to study the spatial arrangement of the filament and lever, and of the head and proboscis of the visiting bee inside the tube. Photographs and films of bee visits on flowers were used to analyse the interaction of pollinator and staminal lever. The spoon-shaped lower lever of S. pratensis ha...