Evolution and Coexistence of Pollination Ecotypes in an African Gladiolus (Iridaceae)

Anderson, Bruce; Alexandersson, Ronny; Johnson, Steven D.

doi:10.1111/j.1558-5646.2009.00880.x

Cited by 101 publications

(116 citation statements)

References 64 publications

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“…By contrast, short-tubed flowers visited by long proboscid insects may be expected to evolve longer tubes to maximize pollen transfer efficiency. This Darwinian explanation for the elongation of floral tubes has been demonstrated in numerous plantpollinator relationships [20,26,27,[62][63][64][65], and when measured it is usually associated with strong positive directional selection coefficients [20,27,64]. Thus, our finding of apparent dramatic reductions in tube length in some populations is contrary to expectations.…”

Section: Discussioncontrasting

confidence: 85%

Intraspecific divergence and convergence of floral tube length in specialized pollination interactions

et al. 2014

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Floral tubes are often thought to be a consequence of adaptive specialization towards pollinator morphology. We explore floral tube length evolution within Tritoniopsis revoluta (Iridaceae), a species with considerable geographical tube length variation. We ask whether tube lengths of T. revoluta populations are associated with pollinator proboscis lengths, whether floral divergence occurs in the presence of different pollinators and whether floral convergence occurs between distantly related populations pollinated by the same pollinator. Finally, we ask whether tube length evolution is directional. Shifts between morphologically different pollinators were always associated with shifts in floral morphology, even when populations were very closely related. Distantly related populations had similar tube lengths when they were pollinated by the same pollinator. Shifts in tube length tended to be from short to long, although reversals were not infrequent. After correcting for the population-level phylogeny, there was a strong positive, linear relationship between floral tube length and pollinator proboscis length, suggesting that plants are functionally specialized on different pollinators at different sites. However, because tube length evolution in this system can be a bidirectional process, specialization to the local pollinator fauna is unlikely to result in evolutionary or ecological dead-ends such as canalization or range limitation.

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Section: Discussioncontrasting

confidence: 85%

Intraspecific divergence and convergence of floral tube length in specialized pollination interactions

et al. 2014

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“…Divergent selection on floral display in the primrose studied was largely explained by spatial variation in the relative strength of interactions with mutualist pollinators and antagonist grazers, and manipulation of the selection regime resulted in rather rapid changes in scape morph frequency. The results indicate that interactions with mutualists and antagonists can drive adaptive differentiation not only across broad geographic scales (2,11,12), but also among plant populations across relatively short distances. This kind of information is fundamental to link environmental heterogeneity to mosaic selection and adaptive evolution.…”

Section: Discussionmentioning

confidence: 96%

Mutualists and antagonists drive among-population variation in selection and evolution of floral display in a perennial herb

Ågren

Hellström

Toräng

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

117

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Spatial variation in the direction of selection drives the evolution of adaptive differentiation. However, few experimental studies have examined the relative importance of different environmental factors for variation in selection and evolutionary trajectories in natural populations. Here, we combine 8 y of observational data and field experiments to assess the relative importance of mutualistic and antagonistic interactions for spatial variation in selection and short-term evolution of a genetically based floral display dimorphism in the short-lived perennial herb Primula farinosa. Natural populations of this species include two floral morphs: long-scaped plants that present their flowers well above the ground and short-scaped plants with flowers positioned close to the ground. The direction and magnitude of selection on scape morph varied among populations, and so did the frequency of the short morph (median 19%, range 0-100%; n = 69 populations). A field experiment replicated at four sites demonstrated that variation in the strength of interactions with grazers and pollinators were responsible for among-population differences in relative fitness of the two morphs. Selection exerted by grazers favored the short-scaped morph, whereas pollinator-mediated selection favored the long-scaped morph. Moreover, variation in selection among natural populations was associated with differences in morph frequency change, and the experimental removal of grazers at nine sites significantly reduced the frequency of the shortscaped morph over 8 y. The results demonstrate that spatial variation in intensity of grazing and pollination produces a selection mosaic, and that changes in biotic interactions can trigger rapid genetic changes in natural plant populations.patial variation in the intensity of biotic interactions is an integral part of the geographic mosaic model of coevolution (1, 2), and may result in divergent selection and the maintenance of genetic variation in traits influencing the strength and outcome of interactions (3, 4). However, few studies have presented quantitative estimates of spatiotemporal variation in selection on traits influencing the outcome of biotic interactions across more than a handful of populations. In plants, variation in the composition of the mutualist and antagonist assemblages may result in spatially varying selection on morphology, phenology, and lifehistory traits (e.g., 5-12). Of particular interest are traits such as floral display that may be subject to conflicting selection from mutualists and antagonists, and where the magnitude and direction of net selection should depend on the relative strength of these interactions (13)(14)(15)(16)(17)(18)(19)(20).Experimental manipulation of environmental conditions is a powerful approach to identify agents of selection and to determine the evolutionary consequences of changes in the selection regime (21,22). Experimental manipulation of pollen deposition (6,23,24) and interactions with herbivores (25-28) can be used to assess the roles of p...

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“…Although intra-specific scent differences can play a role in pollinator choices [16], this is unlikely to be the case for D. ferruginea because butterflies choose between paper flowers using colour alone. Furthermore, models and mimics in this system have no scent discernible to the human nose.…”

Section: Discussionmentioning

confidence: 99%

Flower colour adaptation in a mimetic orchid

2012

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Although the tremendous variability in floral colour among angiosperms is often attributed to divergent selection by pollinators, it is usually difficult to preclude the possibility that floral colour shifts were driven by non-pollinator processes. Here, we examine the adaptive significance of flower colour in Disa ferruginea, a non-rewarding orchid that is thought to attract its butterfly pollinator by mimicking the flowers of sympatric nectar-producing species. Disa ferruginea has red flowers in the western part of its range and orange flowers in the eastern part-a colour shift that we hypothesized to be the outcome of selection for resemblance to different local nectar-producing plants. Using reciprocal translocations of red and orange phenotypes as well as arrays of artificial flowers, we found that the butterfly Aeropetes tulbaghia, the only pollinator of the orchid, preferred both the red phenotype and red artificial flowers in the west where its main nectar plant also has red flowers, and both the orange phenotype and orange artificial flowers in the east, where its main nectar plant has orange flowers. This phenotype by environment interaction demonstrates that the flower colour shift in D. ferruginea is adaptive and driven by local colour preference in its pollinator.

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Evolution and Coexistence of Pollination Ecotypes in an African Gladiolus (Iridaceae)

Cited by 101 publications

References 64 publications

Intraspecific divergence and convergence of floral tube length in specialized pollination interactions

Intraspecific divergence and convergence of floral tube length in specialized pollination interactions

Mutualists and antagonists drive among-population variation in selection and evolution of floral display in a perennial herb

Flower colour adaptation in a mimetic orchid

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