Long-Tongued Fly Pollination and Evolution of Floral Spur Length in the Disa draconis Complex (Orchidaceae)

Johnson, Steven D.; Steiner, Kim E.

doi:10.2307/2410959

Cited by 239 publications

(235 citation statements)

References 20 publications

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“…Nevertheless, it is possible that there has been adaptation of the cycads to cryptic weevil species, which would be a case of divergence driven by shifts in pollinators, rather than coevolution [49,50]. However, a recent molecular study of phylogenetic relationships within Porthetes spp.…”

Section: Discussionmentioning

confidence: 99%

Geographical matching of volatile signals and pollinator olfactory responses in a cycad brood-site mutualism

2015

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Brood-site mutualisms represent extreme levels of reciprocal specialization between plants and insect pollinators, raising questions about whether these mutualisms are mediated by volatile signals and whether these signals and insect responses to them covary geographically in a manner expected from coevolution. Cycads are an ancient plant lineage in which almost all extant species are pollinated through brood-site mutualisms with insects. We investigated whether volatile emissions and insect olfactory responses are matched across the distribution range of the African cycad Encephalartos villosus. This cycad species is pollinated by the same beetle species across its distribution, but cone volatile emissions are dominated by alkenes in northern populations, and by monoterpenes and a pyrazine compound in southern populations. In reciprocal choice experiments, insects chose the scent of cones from the local region over that of cones from the other region. Antennae of beetles from northern populations responded mainly to alkenes, while those of beetles from southern populations responded mainly to pyrazine. In bioassay experiments, beetles were most strongly attracted to alkenes in northern populations and to the pyrazine compound in southern populations. Geographical matching of cone volatiles and pollinator olfactory preference is consistent with coevolution in this specialized mutualism.

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Section: Discussionmentioning

confidence: 99%

Geographical matching of volatile signals and pollinator olfactory responses in a cycad brood-site mutualism

2015

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“…Many studies have demonstrated a close match between flower and pollinator morphology, such as correlations between proboscis length of pollinators and corolla depth of flowers on the scale of species-specific interactions, that have served as supposed examples of coevolution (Alexandersson and Johnson 2002;Grant andGrant 1965, 1983;Harder 1985;Johnson and Steiner 1997;Nilsson 1988Nilsson , 1998Nilsson et al 1985). Although our results showed that the proboscis lengths of skipper butterflies differed significantly between the visited flower species, we did not observe a close match between extremely long proboscides and deep tubes: Extremely long-proboscid skipper butterflies that used C. crotalifera and C. lutea as nectar source had a mean proboscis length of 43.4 mm, exceeding the corolla length of C. crotalifera by 18.4 mm and C. lutea by 12 mm.…”

Section: S Frantziimentioning

confidence: 99%

The ecological role of extremely long-proboscid Neotropical butterflies (Lepidoptera: Hesperiidae) in plant-pollinator networks

Bauder

Warren

Krenn

2015

Arthropod-Plant Interactions

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Extremely long proboscides of insect flower visitors have been regarded as an example of a coevolutionary arms race, assuming that these insects act as efficient pollinators for their nectar host plants. However, the effect of proboscis length on generalized or specialized flower use remains unclear and the efficiency of butterfly pollination is ambiguous. Neotropical Hesperiidae feature a surprising variation of proboscis length, which makes them a suitable study system to elucidate the role of extremely long-proboscid insects in plant-pollinator networks. The results of this study show that skippers with longer proboscides visit plant species with deep-tubed flowers to take up food, but do not pollinate them. Skippers equipped with extremely long proboscides seldom include short-tubed flowers in their diet nor visit more plant species than those with shorter proboscides. Our observations indicate that the extremely long-proboscid skippers steal nectar from their preferred nectar host plants, Calathea sp., instead of contributing to their pollination. Finally, we discuss the impact of nectar robbery by these butterflies on their nectar host plants and their legitimate pollinators, euglossine bees.

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“…For nearly all of these radiations, there exists an outlier species, with extremely long mouthparts, that visit plants with flowers of a corresponding length. Examples include the sword-billed hummingbird (Ensifera ensifera) with a 10 cm long bill (Snow & Snow 1980), the mega-nosed fly (Moegistorynchus longirostris) with a 5.7 cm long proboscis ( Johnson & Steiner 1997) and the giant hawkmoth (Xanthopan morgani praedicta) with a 25 cm long proboscis ( Nilsson et al 1985). Darwin (1862) and Wallace (1867) provided a possible explanation for such extreme elongation, suggesting that the long nectar spur of the Malagasy star orchid (Angraecum sesquipedale) evolved in a coevolutionary race with a giant hawkmoth.…”

Section: Introductionmentioning

confidence: 99%

“…Several studies have provided support for Darwin's hypothesis by demonstrating instances of pollinators imposing directional selection on flower length ( Nilsson 1988;Johnson & Steiner 1997;Alexandersson & Johnson 2002;Anderson & Johnson 2008). However, the hypothesis has also met with resistance since it was first published, and various alternative models have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Going to great lengths: selection for long corolla tubes in an extremely specialized bat–flower mutualism

2009

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In a hypothesis that has remained controversial since its inception, Darwin suggested that long-tubed flowers and long-tongued pollinators evolved together in a coevolutionary race, with each selecting for increasing length in the other. Although the selective pressures that flowers impose on tongue length are relatively straightforward, in that longer tongues allow access to more nectar, selective pressures that pollinators impose on flower length are less clear. Here, we test for such selective pressures in the highly specialized mutualism between the nectar bat Anoura fistulata, which can extend its tongue twice as far as other nectar bats, and Centropogon nigricans, which has flowers of a similar length (8-9 cm). We used flight cage experiments to examine the effects of artificially manipulated flower lengths on (i) bat behaviour and (ii) pollen transfer. Increased length produced longer visits, but did not affect the force bats applied during visits. In the second experiment, flower length increased both the male and female components of flower function: long male flowers delivered more pollen grains and long female flowers received more pollen grains. However, pollen transfer was not correlated with visit duration, so the mechanism behind differences in pollen transfer remains unclear. By demonstrating that bats select for increasing flower length, these results are consistent with the hypothesis that A. fistulata evolved its remarkable tongue in a coevolutionary race with long-tubed flowers similar to that envisioned by Darwin.

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Long-Tongued Fly Pollination and Evolution of Floral Spur Length in the Disa draconis Complex (Orchidaceae)

Cited by 239 publications

References 20 publications

Geographical matching of volatile signals and pollinator olfactory responses in a cycad brood-site mutualism

Geographical matching of volatile signals and pollinator olfactory responses in a cycad brood-site mutualism

The ecological role of extremely long-proboscid Neotropical butterflies (Lepidoptera: Hesperiidae) in plant-pollinator networks

Going to great lengths: selection for long corolla tubes in an extremely specialized bat–flower mutualism

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