Can a flower color ancestral polymorphism transcend speciation?

Sánchez-Cabrera, Mercedes; Narbona, Eduardo; Arista, Montserrat; Ortiz, Pedro L.; Jiménez-López, Francisco J.; Fuller, Amelia; Carter, Benjamin; Whittall, Justen B.

doi:10.1101/2023.11.14.566988

Cited by 3 publications

(2 citation statements)

References 70 publications

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“…Diplacus (Short & Streisfeld, 2023 ), which could provide one hypothesis explaining how yellow flowers in C. sessiliflora may have arisen, especially in areas of range overlap with C. citrina . Alternatively, ancestral polymorphisms in floral color that precede speciation events (Sánchez‐Cabrera et al., 2023 ) or convergent shifts in floral color among related species (Stone & Wessinger, 2024 ; Thomson & Wilson, 2008 ; Wenzell et al., 2024 ) provide alternate explanations which require further study.…”

Section: Discussionmentioning

confidence: 99%

Adaptive generalization in pollination systems: Hawkmoths increase fitness to long‐tubed flowers, but secondary pollinators remain important

Wenzell,

Zhang,

Skogen

et al. 2024

Ecology and Evolution

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Selection on floral traits by animal pollinators is important in the evolution of flowering plants, yet whether floral divergence requires specialized pollination remains uncertain. Longer floral tubes, a trait associated with long‐tongued pollinators, can also exclude other pollinators from accessing rewards, a potential mechanism for specialization. Across most of its range, Castilleja sessiliflora displays much longer corollas than most Castilleja species, though tube length varies geographically and correlates partially with hawkmoth visitation. To assess whether long corolla tubes reflect adaptation to hawkmoth pollinators, we performed a day/night pollinator exclusion experiment in nine natural populations that varied in corolla length across the range of C. sessiliflora and short‐tubed members of the parapatric C. purpurea complex. We compared the fitness contributions of nocturnal and diurnal visitors, revealing that long‐tubed populations visited predominantly by hawkmoths experienced greater fruit set at night, in contrast with short‐tubed populations or those visited mainly by diurnal pollinators. Next, leveraging a range‐wide multiyear dataset of pollinator visitation to these species, we identify that hawkmoth visitation is associated with increased fitness in long‐tubed populations overall, and that long tubes are associated with less diverse visitor assemblages. Thus, long corollas represent an adaptation to hawkmoth pollination at the exclusion of diverse pollinators. Nonetheless, while hawkmoths were scarce in the northern range, secondary diurnal pollinators contributed to fruit set across the range, providing reproductive assurance despite possible trait mismatch. This study illustrates adaptive generalization in pollination systems and that floral divergence may proceed along a continuum of generalized and specialized pollinator interactions.

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Section: Discussionmentioning

confidence: 99%

Adaptive generalization in pollination systems: Hawkmoths increase fitness to long‐tubed flowers, but secondary pollinators remain important

Wenzell,

Zhang,

Skogen

et al. 2024

Ecology and Evolution

View full text Add to dashboard Cite

show abstract

“…Diplacus (Short and Streisfeld, 2023), which could provide one hypothesis explaining how yellow flowers in C. sessiliflora may have arisen, especially in areas of overlap with C. citrina. Alternatively, ancestral polymorphisms in floral color that precede speciation events (Sánchez-Cabrera et al, 2023) or convergent shifts in floral color among related species (Thomson and Wilson, 2008;Wenzell et al, 2023a;Stone and Wessinger, 2024) provide alternate explanations which require further study.…”

Section: Discussionmentioning

confidence: 99%

Adaptive generalization in pollinators: hawkmoths increase fitness to long-tubed flowers, but secondary pollinators remain important

Wenzell,

Zhang,

Skogen

et al. 2024

Preprint

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Selection on floral traits by animal pollinators is important in the evolution of flowering plants, yet whether floral divergence requires specialized pollination remains uncertain. Longer floral tubes, a trait associated with long-tongued pollinators, can also exclude other pollinators from accessing rewards, a potential mechanism for specialization. Across most of its range, Castilleja sessiliflora displays much longer corollas than most Castilleja species, though tube length varies geographically and correlates partially with hawkmoth visitation. To assess if long corolla tubes reflect adaptation to hawkmoth pollinators, we performed a day/night pollinator exclusion experiment in nine natural populations that varied in corolla length across the range of C. sessiliflora and short-tubed members of the parapatric C. purpurea complex. We compared the fitness contributions of nocturnal and diurnal visitors, revealing that long-tubed populations visited predominantly by hawkmoths experienced greater fruit set at night, in contrast with short-tubed populations or those visited mainly by diurnal pollinators. Next, leveraging a range-wide multi-year dataset of pollinator visitation to these species, we identify that hawkmoth visitation is associated with increased fitness in long-tubed populations overall, and that long tubes are associated with less diverse visitor assemblages. Thus, long corollas represent an adaptation to hawkmoth pollination at the exclusion of diverse pollinators. Nonetheless, while hawkmoths were scarce in the northern range, secondary diurnal pollinators contributed to fruit set across the range, providing reproductive assurance despite possible trait mismatch. This study illustrates adaptive generalization in pollination modes and that floral divergence may proceed along a continuum of generalized and specialized pollinator interactions.

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Within-species floral evolution reveals convergence in adaptive walks during incipient pollinator shift

Wenzell,

Neequaye,

Paajanen

et al. 2023

Preprint

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Pollinators are important in the evolution of flowering plants, but questions remain about how early stages of pollinator-mediated speciation arise. Studying intraspecific variation in floral traits can shed light on early stages of floral trait divergence and identify how traits evolve as signals to novel pollinators, either acting separately or in concert. Among two hummingbird- pollinated species of monkeyflowers (Mimulussection Erythranthe),M. cardinalisandM. verbenaceus, yellow floral morphs have arisen from more common, red-flowered morphs and have become well-established in several populations. To identify 1) whether these floral transitions involve additional floral traits beyond color and 2) if they represent incipient pollinator shifts, we characterized yellow-flowered morphs ofM. verbenaceusandM. cardinalisand their more common red-flowered forms across numerous floral traits (reflectance, pigmentation, volatile organic compounds, morphology, and nectar) and assessed pollinator perception and preference of floral signals by a novel bumblebee pollinator (Bombus terrestris ssp. audax). The two yellow morphs appeared to follow independent evolutionary paths, resulting in distinct hues of yellow that varied in reflectance, pigmentation, and perception by bees. For floral scent, both yellow forms differed from their red conspecific forms: in one case increasing total emissions of a similar scent profile (M. verbenaceus), and in the other, emitting a distinct scent profile at similarly low levels (M. cardinalis). In both species, yellow morphs had wider, less restrictive corolla openings and greater herkogamy than red flowers but produced similar nectar rewards. Collectively, these floral trait differences resulted in a clear preference for yellow floral morphs in both species, with naïve bumblebees choosing yellow flowers twice as often as red forms. Despite the increased attractiveness of yellow morphs, bumblebees had difficulty handling flowers to access rewards, suggesting they may be ineffective pollinators to current floral phenotypes. This study reveals that parallel transitions in floral color in two monkeyflower species involve a suite of changes to other floral traits which directly impacts interactions with potential pollinators. This work highlights the value of integrative studies of intraspecific floral phenotypes and behavioral responses of pollinators to understand incipient pollinator shifts and the potential for future pollinator-mediated floral evolution.

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Can a flower color ancestral polymorphism transcend speciation?

Cited by 3 publications

References 70 publications

Adaptive generalization in pollination systems: Hawkmoths increase fitness to long‐tubed flowers, but secondary pollinators remain important

Adaptive generalization in pollination systems: Hawkmoths increase fitness to long‐tubed flowers, but secondary pollinators remain important

Adaptive generalization in pollinators: hawkmoths increase fitness to long-tubed flowers, but secondary pollinators remain important

Within-species floral evolution reveals convergence in adaptive walks during incipient pollinator shift

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