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Phenotype space and floral typology: towards an objective assessment of pollination syndromes
... We can often predict the pollinators of a flower from its floral biology (e.g. colour, scent, reward, opening time, etc.) (Ollerton & Watts 2000). This set of floral characteristics is called "pollination syndrome". ...
... They form large conspicuous flowers of five different floral types (trumpet, apron, open, short tube, collar) with one single floral type dominating (trumpet) (Ley & Harris 2014). Based solely on morphological characters and the concept of "pollination syndromes" (Ollerton & Watts 2000), first hypotheses about their pollinating species have been pronounced (Ley & Harris 2014). ...
Background and aims – Diversification in plant-pollinator interactions based on floral diversity is potentially a mechanism of coexistence in angiosperms. However, besides high floral diversity, some genera seemingly exhibit the same floral type in many of their species. This contradicts some expectations of competitive exclusion. We thus tested on a finer flower morphological scale whether five sympatric Aframomum species (61 spp., Zingiberaceae) in southeastern Gabon exhibiting the same general floral type (trumpet) were differentiated, and whether this resulted in different “pollinator niches”.Material and methods – We carried out a detailed survey measuring 18 flower morphological parameters as well as nectar volume (μl) and sugar concentration (% Brix) on five flowers per species and locality. Furthermore, we observed inflorescence phenology and pollinator activity from 8 am to 4 pm for 12 to 50 hours per species and conducted pollinator exclusion experiments.Key results – This study proves fine-scale flower morphological and resource differentiation within the trumpet floral type. Pollination-relevant parts of the flowers, however, remain constant across species. Our pollinator observations reveal the same broad bee pollinator spectrum for all observed simultaneously flowering sympatric species.Conclusion – As we could not detect a pollinator-based differentiation in the studied sympatric Aframomum species we assume that species boundaries developed randomly by genetic drift during geographic isolation in the past. The trumpet floral type and its pollinator guild, however, were maintained due to similar selection pressures in comparable habitats during isolation and are potentially an advantage for increased pollinator attraction through co-flowering.
... The feeding behaviour of moths (and other animal groups) is related to modifications of flowers or plant parts adapted to pollination in a particular way, termed "pollination syndrome" (Faegri and van der Pijl 1979). Two pollination syndromes are recognised for moths: sphingophily for hawkmoths (Sphingidae) and phalaenophily for other groups (Faegri and van der Pijl 1979;Willmer 2011), which are sometimes difficult to differentiate (Ollerton and Watts 2000). Another term for this latter type of pollinator is "settling moths" because, unlike sphinx moths that remain in flight to suck nectar from flowers, these other groups require settling down to feed. ...
Understanding the pollination mechanisms of “settling moths” (moths from families other than Sphingidae typically perched on corollas while feeding on flowers) in the Neotropics is crucial for assessing their contributions to plant reproduction and ecosystem resilience. Through extensive literature searches on Google Scholar and SCOPUS, this study identified 44 relevant studies from an initial pool of 410. These studies covered 37 ecoregions across over 30 million km ² , primarily focusing on natural habitats, with Brazil, Argentina, and Mexico as major contributors. The research on Neotropical moth pollination has surged since 2000, with Noctuoidea, Geometridae, and Pyraloidea as the most cited moth groups. Despite the significant progress in documenting moth pollination, our assessment of taxonomic resolution revealed a heavy reliance on field observations, underscoring the need for collaboration with taxonomists to improve species‐level identifications and enrich ecological interpretations. Our network analysis of interactions between 37 plant families and 14 nocturnal moth families or higher taxon groups indicated a matrix fill of approximately 18.7%, with significant nestedness pointing to generalist‐specialist dynamics among plant and moth families. Modularity analysis identified distinct clusters of interactions, suggesting that specific plant and moth families engage in compartmentalised relationships shaped by ecological and evolutionary factors. Dominant groups, such as Asteraceae and Fabaceae among plants, and Erebidae and Noctuidae among moths, played central roles within these modules, underscoring their importance in maintaining nocturnal pollination networks. These findings emphasise the importance of both diverse and dominant pollinator groups in supporting Neotropical pollination dynamics. Our work highlights the need for pollinator‐centred studies, the adoption of standardised methodologies, and deeper exploration of exclusive moth pollination to advance understanding of plant reproduction across the Neotropics. Future research should aim to bridge gaps in species‐level identification and further investigate the ecological and evolutionary significance of nocturnal pollination across diverse environments.
... Wasps can be found as pollinators of both generalist and specialized flowers (Heithaus, 1979;Nilsson, 1981;Kephart, 1983;Vieira & Shepherd, 1999;Ollerton et al., 2003;Johnson, 2005;Shuttleworth & Johnson, 2006;Shuttleworth & Johnson, 2009;Johnson, Ellis & Dötterl, 2007). While Faegri & Van der Pijl (1979) did not specifically describe a wasp pollination syndrome, evidence suggests that wasps often pollinate easily approachable flowers that have dull or cryptic coloration, a strong or unusual scent, and concentrated nectar (Heithaus, 1979;Proctor, Yeo & Lack, 1996;Ollerton & Watts, 2000;Johnson, Ellis & Dötterl, 2007;Shuttleworth & Johnson, 2009). According to Kingston & Mc Quillan (2000), flowers that are visited by wasps mainly have pale colors, followed by yellow and some purple flowers. ...
Three morning glory species in the genus Argyreia Lour., A. lycioides (Choisy) Traiperm & Rattanakrajang, A. mekongensis Gagnep & Courchet, and A. versicolor (Kerr) Staples & Traiperm, were found co-occurring and co-flowering. Argyreia mekongensis and A. versicolor are rare, while A. lycioides is near threatened and distributed throughout Myanmar and Thailand. We investigated key floral characters (floral morphology and phenology, as well as the micromorphology of the floral nectary disc and staminal trichomes) and screened for important chemical compounds hypothesized to contribute to pollinator attraction. Our findings demonstrate that some aspects of floral morphology ( e.g. , corolla size, limb presence, and floral color) of the three studied congeners exhibit significant differences. Moreover, pollinator composition appears to be influenced by floral shape and size; morning glory species with wider corolla tubes were pollinated by larger bees. The morphology of the floral nectary disc was similar in all species, while variation in staminal trichomes was observed across species. Glandular trichomes were found in all three species, while non-glandular trichomes were found only in A. versicolor . Histochemical results revealed different compounds in the floral nectary and staminal trichomes of each species, which may contribute to both floral attraction and defense. These findings demonstrate some segregation of floral visitors among sympatric co-flowering morning glory species, which appears to be influenced by the macro- and micromorphology of flowers and their chemical compounds. Moreover, understanding the floral morphology and chemical attractants of these sympatric co-flowering Argyreia species may help to maintain their common pollinators in order to conserve these rare and endangered species, especially A. versicolor .
... Keel flowers might have evolved to host these efficient pollinators (strong bees or long-tongued bees of Apidae and Megachilidae families) [63,67,70]. Indeed, Ruxton and Schaefer [71] suggested, instead of mimicry, that convergent evolution (i.e., pollination syndromes sensu Faegri andVan der Pijl [25]) driven by shared pollinators could be a more plausible explanation not only for the evolution of keel blossoms within unrelated lineages of angiosperms [9,58,62,[72][73][74] but also for most supposed plant mimics. Moreover, since the hymenopterans were already highly diversified at that time, a competition free space with similar morphologies would have helped Polygalaceae keel flowers to benefit this new area and radiate ( [54,75], Anonymous Reviewer 2, pers. ...
Background
Keel flowers are bilaterally symmetrical, pentamerous flowers with three different petal types and reproductive organs enclosed by keel petals; generally there is also connation of floral parts such as stamens and keel petals. In this study, the evolution of keel flowers within the order Fabales is explored to investigate whether the establishment of this flower type within one of the species-rich families, the Fabaceae (Leguminosae), preceded and could have influenced the evolution of keel flowers in the Polygalaceae. We conducted molecular dating, and ancestral area and ancestral state analyses for a phylogeny constructed for 678 taxa using published matK , rbcL and trnL plastid gene regions.
Results
We reveal the temporal and spatial origins of keel flowers and traits associated with pollinators, specifically floral symmetry, the presence or absence of a pentamerous corolla and three distinct petal types, the presence or absence of enclosed reproductive organs, androecium types, inflorescence types, inflorescence size, flower size, plant height and habit. Ancestral area reconstructions show that at the time keel flowers appeared in the Polygaleae, subfamily Papilionoideae of the Fabaceae was already distributed almost globally; at least eight clades of the Papilionoideae had keel flowers with a functional morphology broadly similar to the morphology of the first evolving Polygaleae flowers.
Conclusions
The multiple origins of keel flowers within angiosperms likely represent convergence due to bee specialization, and therefore pollinator pressure. In the case of the Fabales, the first evolving keel flowers of Polygaleae have a functional morphology that corresponds with keel flowers of species of the Papilionoideae already present in the environment. These findings are consistent with the keel-flowered Polygaleae exploiting pollinators of keel-flowered Papilionoideae. The current study is the first to use ancestral reconstructions of traits associated with pollination to demonstrate that the multiple evolutionary origins of the keel flower pollinator syndrome in Fabales are consistent with, though do not prove, mimicry.
... We selected floral traits commonly included in the pollination syndromes definitions (Ollerton et al., 2009;Ollerton & Watts, 2000; Table S1). Morphometric traits (size, tube length/width) were measured with an electronic calliper, whilst visual (shape, symmetry, colour, flower/anther position, nectar guides) and olfactory traits (odour strength) were recorded by the observer. ...
The pollination syndrome hypothesis predicts that plants pollinated by the same pollinator group bear convergent combinations of specific floral functional traits. Nevertheless, some studies have shown that these combinations predict pollinators with relatively low accuracy. This discrepancy may be caused by changes in the importance of specific floral traits for different pollinator groups and under different environmental conditions. To explore this, we studied pollination systems and floral traits along an elevational gradient on Mount Cameroon during wet and dry seasons. Using Random Forest (Machine Learning) models, allowing the ranking of traits by their relative importance, we demonstrated that some floral traits are more important than others for pollinators. However, the distribution and importance of traits vary under different environmental conditions. Our results imply the need to improve our trait-based understanding of plant-pollinator interactions to better inform the debate surrounding the pollination syndrome hypothesis.
... In fact, selection exerted by functionally equivalent pollinators is considered to be the main driver of the convergent evolution of floral traits in different plant species, the so-called pollination syndromes (Faegri & van der Pijl, 1980;Dellinger, 2020;Phillips et al., 2020;Wessinger & Hileman, 2020). All of this suggests that pollinators are an important motor shaping the pattern and geometry of occupation of floral phenotypic space (Ollerton & Watts, 2000;Ollerton et al., 2009;Chartier et al., 2014Chartier et al., , 2017Smith & Kriebel, 2018;Herv ıas-Parejo et al., 2019). ...
Many flowers exhibit phenotypic plasticity. By inducing the production of several phenotypes, plasticity may favour the rapid exploration of different regions of the floral morphospace. We investigated how plasticity drives Moricandia arvensis, a species displaying within‐individual floral polyphenism, across the floral morphospace of the entire Brassicaceae family.
We compiled the multidimensional floral phenotype, the phylogenetic relationships, and the pollination niche of over 3000 species to construct a family‐wide floral morphospace. We assessed the disparity between the two M. arvensis floral morphs (as the distance between the phenotypic spaces occupied by each morph) and compared it with the family‐wide disparity. We measured floral divergence by comparing disparity with the most common ancestor, and estimated the convergence of each floral morph with other species belonging to the same pollination niches.
Moricandia arvensis exhibits a plasticity‐mediated floral disparity greater than that found between species, genera and tribes. The novel phenotype of M. arvensis moves outside the region occupied by its ancestors and relatives, crosses into a new region where it encounters a different pollination niche, and converges with distant Brassicaceae lineages.
Our study suggests that phenotypic plasticity favours floral divergence and rapid appearance of convergent flowers, a process which facilitates the evolution of generalist pollination systems.
... Since angiosperm reproduction is highly selective, such variations in stigma traits are expected to be influenced by different selection forces to facilitate ovule fertilization (Edlund et al. 2004). It is known that selective pressures imposed by pollinators play an important role in floral evolution of flowering plants (Stebbins 1970;Schemske and Horvitz 1984;Ollerton 1996;Ollerton and Watts 2000;Harder and Johnson 2009). In this context, an adjustment of the arrangement of floral structures (e.g., gynoecium) to the morphological and/or behavioral traits of pollinators can also be expected to increase the formation of fruits and/or seeds (Johnson and Steiner 2000;Fenster et al. 2004). ...
Most species of Neotropical Malpighiaceae are pollinated by oil-collecting bees of diverse sizes, but the effect of pollinator size on their reproductive success has still not been addressed in the literature. We performed a comparative description of stigma arrangements, analyzing the reproductive system and reproductive success and assessing pollinator sizes in Stigmaphyllon bonariense and Stigmaphyllon jatrophifolium. We collected flowers in three natural populations, conducting pollinator censuses and captures and performing manipulative experiments to determine the plants breeding system. We analyzed the morphology of stigmas and their receptivity and calculated the perimeter of the triangle formed by the stigmas (ST). Pollinator sizes, potential area for pollen transfer (PAPT), and the frequency of visits were also calculated. Stigma arrangement resulted in inverted triangles, and the ST was smaller in S. jatrophifolium than in S. bonariense. The overlap between ST and PAPT suggests that pollinators of all sizes were efficient in pollinating S. jatrophifolium, whereas only large and very large pollinators where efficient in S. bonariense. Moreover, very large pollinators had the highest visit frequencies. Our results indicated that both species are obligate xenog-amous, pollinator-dependent, and present pollen limitation. We observed an increase in reproductive success related to the marked turnover in pollinator assemblage throughout the flowering season. These findings suggest that fruit and seed sets vary according to the context of the pollinators and that large pollinators would have the best performance.
... Since angiosperm reproduction is highly selective, such variations in stigma traits are expected to be influenced by different selection forces to facilitate ovule fertilization (Edlund et al. 2004). It is known that selective pressures imposed by pollinators play an important role in floral evolution of flowering plants (Stebbins 1970;Schemske and Horvitz 1984;Ollerton 1996;Ollerton and Watts 2000;Harder and Johnson 2009). In this context, an adjustment of the arrangement of floral structures (e.g., gynoecium) to the morphological and/or behavioral traits of pollinators can also be expected to increase the formation of fruits and/or seeds (Johnson and Steiner 2000;Fenster et al. 2004). ...
Most species of Neotropical Malpighi-aceae are pollinated by oil-collecting bees of diverse sizes, but the effect of pollinator size on their reproductive success has still not been addressed in the literature. We performed a comparative description of stigma arrangements, analyzing the reproductive system and reproductive success and assessing pollinator sizes in Stigmaphyllon bonariense and Stigmaphyllon jatrophifolium. We collected flowers in three natural populations, conducting pollinator censuses and captures and performing manipulative experiments to determine the plants breeding system. We analyzed the morphology of stigmas and their receptivity and calculated the perimeter of the triangle formed by the stigmas (ST). Pollinator sizes, potential area for pollen transfer (PAPT), and the frequency of visits were also calculated. Stigma arrangement resulted in inverted triangles, and the ST was smaller in S. jatrophifolium than in S. bonariense. The overlap between ST and PAPT suggests that pollinators of all sizes were efficient in pollinating S. jatrophifolium, whereas only large and very large pollinators where efficient in S. bonariense. Moreover, very large pollinators had the highest visit frequencies. Our results indicated that both species are obligate xenog-amous, pollinator-dependent, and present pollen limitation. We observed an increase in reproductive success related to the marked turnover in pollinator assemblage throughout the flowering season. These findings suggest that fruit and seed sets vary according to the context of the pollinators and that large pollinators would have the best performance.
Pollination syndromes have been widely used to predict the groups of pollinators of plants. Their predictability has been demonstrated for plant species pollinated by bees, birds, and bats. However, the importance of other aspects on the predictability of pollination syndromes still remain unknown. For instance, plant life cycle has not been considered in evaluations of the pollination syndrome predictability. The goal of this study was to evaluate the predictability of pollination syndromes in nine species with contrasting life cycles. Pollination syndromes were inferred based on floral traits of each plant species, whereas pollinator effectiveness of each group of floral visitors was established through pollen load analysis. Predictability of pollination syndromes was tested through the association between floral traits and the abundance of the most‐effective pollinators. Bees, flies, birds, beetles, and butterflies were the primary and secondary pollinators inferred from floral traits of each species. Although six out of the nine plant species studied were visited by effective pollinators; only four species were effectively pollinated by the groups of primary or secondary pollinators predicted from floral traits. However, Dahlia coccinea and Tigridia pavonia were the only species in which the predicted pollinator group was both effective and showed an association with floral traits. Pollination syndromes were not predictive of pollinators for any of the annual and perennial plant species. Although pollination syndromes are useful to understand some aspects of the reproductive biology of plant species, several other factors might have a role on their predictability.
Floral scent has been suggested to be a key factor both in the diversification of the angiosperms, and the evolution and intra-specific differentiation of plants. In this study, we determined the ploidy and nuclear DNA content of B. macrostachya plants from 14 different populations across Yunnan using flow cytometry. The components of the floral scent were also identified using gas chromatography and mass spectrometry (GC-MS). Within these 14 populations, two new ploidy levels, tetraploid (2n = 4x) and octaploid (2n = 8x) were detected and identified for the first time here. The mean 2C DNA content of the tetraploids ranged from 1.81 ± 0.01 to 1.92 ± 0.02 G, but was 3.52 ± 0.15 to 3.73 ± 0.04 G in the octaploids. In addition, thirty-two scent compounds were identified, most of which could be categorized into four major classes: fatty acid derivatives (49.60 ± 7.45%); benzenoids (21.24 ± 3.96%); monoterpenes (25.28 ± 3.70%) and sesquiterpenes (3.88 ± 1.05%). Both tetraploids and octaploids emitted large relative amounts of 4-hydroxy-4-methyl-2-pentanone (42.21 ± 3.52% and 21.57 ± 3.10%, respectively) and benzadehyde (20.42 ± 2.35% and 28.45 ± 2.37%, respectively). Multivariate analysis of floral scent chemistry revealed marked dissimilarity (49.49%) between tetraploids and octaploids, and 4-hydroxy-4-methyl-2-pentanone and benzadehyde contributed greatly to this divergence in chemical scent profile. Our results suggest that B. macrostachya is a species complex with four different ploidy levels (2n = 4x, 6x, 8x, 12x). We believe the complex is in a process of pollinator-mediated rapid divergence.