-
Emerging Topics in Life Sciences Jul 2020Plant induced responses to herbivory have long been found to function as plant direct and indirect defenses and to be major drivers of herbivore community and population... (Review)
Review
Plant induced responses to herbivory have long been found to function as plant direct and indirect defenses and to be major drivers of herbivore community and population dynamics. While induced defenses are generally understood as cost-saving strategies that allow plants to allocate valuable resources into defense expression, it recently became clear that, in particular, induced metabolic changes can come with significant ecological costs. In particular, interactions with mutualist pollinators can be significantly compromised by herbivore-induced changes in floral morphology and metabolism. We review recent findings on the evidence for ecological conflict between defending against herbivores and attracting pollinators while using similar modes of information transfer (e.g. visual, olfactory, tactile). Specifically, we discuss plant traits and mechanisms through which plants mediate interactions between antagonists and mutualist and present functional hypotheses for how plants can overcome the resulting conflicts.
Topics: Ecology; Flowers; Herbivory; Host-Parasite Interactions; Phenotype; Plant Physiological Phenomena; Plants; Pollination; Secondary Metabolism; Symbiosis
PubMed: 32537636
DOI: 10.1042/ETLS20190121 -
PloS One 2023Generalist honey bees grant significant pollination services worldwide. Although honey bees can provide compensatory pollination services, their service to...
Generalist honey bees grant significant pollination services worldwide. Although honey bees can provide compensatory pollination services, their service to buzz-pollinated crops, compared to specialized pollinators, is not clear. In this study, we assessed the contribution of Africanized honey bees (AHB) and native sonicating bees (NBZ) to the pollination of eggplant (Solanum melongena) and annatto (Bixa orellana) in Yucatan, Mexico, one of the largest producers of these crops in the Americas and a region with one of the largest densities of honey bees in the world. We first compared the relative frequency and abundance of both bee types on flowers of both crops. Secondly, we controlled access to flowers to compare the number and weight of fruit and number of seed produced after single visits of AHB and native bees. For a better assessment of pollination services, we evaluated the productivity of individual flowers multiply visited by AHB. The results were compared against treatments using pollinator-excluded flowers and flowers that were supplied with additional pollen, which allowed an overall measure of pollination service provision (PSP). Our results showed that AHB were the predominant flower visitors in both crops and that were poorly efficient on individual visits. Notably, fruit quantity and seed number increased concomitantly with the number of AHB visits per flower on eggplant, but not on annatto. Estimation of PSP revealed no pollination deficit on eggplant but that a deficit existed on the pollination services to annatto. We found that AHB numerical predominance compensates their poor individual performance and can complement the services of native bees on eggplant, but not on annatto. We discuss possible explanations and implications of these results for buzz-pollinated crops in the neotropics an area with little assessment of pollination services and a high density of honey bees.
Topics: Bees; Animals; Pollination; Flowers; Fruit; Seeds; Pollen; Crops, Agricultural; Solanum melongena
PubMed: 36696409
DOI: 10.1371/journal.pone.0280875 -
BMC Ecology and Evolution Apr 2022Keel flowers are bilaterally symmetrical, pentamerous flowers with three different petal types and reproductive organs enclosed by keel petals; generally there is also...
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.
Topics: Animals; Bees; Fabaceae; Flowers; Humans; Magnoliopsida; Phylogeny; Pollination
PubMed: 35413792
DOI: 10.1186/s12862-022-02003-y -
Plant Biology (Stuttgart, Germany) Jan 2022Pollination of the pantropical Vanilla has been linked to melittophily and food deception. Here we investigated the role of flower traits on the reproduction of...
Pollination of the pantropical Vanilla has been linked to melittophily and food deception. Here we investigated the role of flower traits on the reproduction of Neotropical Vanilla. We also studied the evolution of pollination systems in order to understand the origin of production of flower resources and the diversification of pollinators in this orchid genus. Our study was founded on data of adaptations in flower morphology, production of resources, scent release, pollinators and breeding systems of Vanilla and presenting new data on reproductive biology of V. palmarum. Data on reproductive biology of Vanilla were mapped onto a phylogeny to address our queries on the evolution of pollination systems in this genus. Vanilla palmarum shows a mixed mating system, with its facultative autogamous flowers being pollinated by hummingbirds. Its yellow flowers are scentless and produces nectar. Mapping of the pollination system onto trees resulted in one origin for bird pollination and at least two origins for autogamy in Vanilla. Nectar secretion has a single origin in the Neotropical thick-leafed lineage. Bird pollination of Vanilla is shown for the first time. The origin of ornithophily within a bee-pollinated clade is supported by flower morphology. Floral transitions to ornithophily have been favoured by the occupation of a distinct niche from that of the other thick-leafed Vanilla species. Despite its specialized pollination, V. palmarum is autogamous. A mixed mating system can promote reproductive assurance in the case of a decline in pollinator populations, or in areas where pollinator services are irregular or absent.
Topics: Animals; Bees; Flowers; Orchidaceae; Plant Breeding; Plant Nectar; Pollination; Vanilla
PubMed: 34724285
DOI: 10.1111/plb.13356 -
Biological Reviews of the Cambridge... Jun 2024Floral bracts (bracteoles, cataphylls) are leaf-like organs that subtend flowers or inflorescences but are of non-floral origin; they occur in a wide diversity of... (Review)
Review
Floral bracts (bracteoles, cataphylls) are leaf-like organs that subtend flowers or inflorescences but are of non-floral origin; they occur in a wide diversity of species, representing multiple independent origins, and exhibit great variation in form and function. Although much attention has been paid to bracts over the past 150 years, our understanding of their adaptive significance remains remarkably incomplete. This is because most studies of bract function and evolution focus on only one or a few selective factors. It is widely recognised that bracts experience selection mediated by pollinators, particularly for enhancing pollinator attraction through strong visual, olfactory, or echo-acoustic contrast with the background and through signalling the presence of pollinator rewards, either honestly (providing rewards for pollinators), or deceptively (attraction without reward or even trapping pollinators). However, studies in recent decades have demonstrated that bract evolution is also affected by agents other than pollinators. Bracts can protect flowers, fruits, or seeds from herbivores by displaying warning signals, camouflaging conspicuous reproductive organs, or by providing physical barriers or toxic chemicals. Reviews of published studies show that bracts can also promote seed dispersal and ameliorate the effects of abiotic stressors, such as low temperature, strong ultraviolet radiation, heavy rain, drought, and/or mechanical abrasion, on reproductive organs or for the plants' pollinators. In addition, green bracts and greening of colourful bracts after pollination promote photosynthetic activity, providing substantial carbon (photosynthates) for fruit or seed development, especially late in a plant's life cycle or season, when leaves have started to senesce. A further layer of complexity derives from the fact that the agents of selection driving the evolution of bracts vary between species and even between different developmental stages within a species, and selection by one agent can be reinforced or opposed by other agents. In summary, our survey of the literature reveals that bracts are multifunctional and subject to multiple agents of selection. To understand fully the functional and evolutionary significance of bracts, it is necessary to consider multiple selection agents throughout the life of the plant, using integrative approaches to data collection and analysis.
Topics: Magnoliopsida; Flowers; Pollination; Biological Evolution; Animals
PubMed: 38291834
DOI: 10.1111/brv.13060 -
Plant Biology (Stuttgart, Germany) Oct 2023Pollinator shifts are often related to speciation in angiosperms, and the relationship between them has been discussed in several plant taxa. Although limited... (Review)
Review
Pollinator shifts are often related to speciation in angiosperms, and the relationship between them has been discussed in several plant taxa. Although limited information on plants pollinated by non-flying mammals in Central and South America and Africa is available, related research has not been conducted in Asia. Herein, I summarize the available knowledge of pollination in Asian Mucuna (Fabaceae), a genus mainly distributed in the tropics, and discuss the evolution of plants pollinated by non-flying mammals in Asia. Nineteen pollinator species have been recorded and pollination systems have been categorized into four types. An examination of the relationship between Mucuna species and their pollinators from the lineage perspective revealed that all species in Mucuna, subgenus Macrocarpa, which are distributed in Asia, are pollinated exclusively by non-flying mammals. Additionally, plants pollinated by non-flying mammals were found to have diverged from bat-pollinated and non-flying mammal-pollinated plants, while plants pollinated by non-flying mammals have evolved multiple times. This is a unique example of evolutionary transition. I hypothesize that the diversification of squirrel species in tropical Asia may have led to the speciation and diversification of Mucuna in Asia. Furthermore, the behavioural and ecological characteristics of bats and birds in Asia differ from the characteristics of those in other regions, implying that Asian Mucuna species do not rely on bat or bird pollinators. The adaptation of floral characteristics to pollinators is not well understood in Asia. Mammal-pollinated plants in Asia may have evolved differently from those in other regions and have unique pollination systems.
Topics: Animals; Pollination; Fabaceae; Mucuna; Chiroptera; Flowers; Mammals; Plants
PubMed: 37408380
DOI: 10.1111/plb.13557 -
Journal of Economic Entomology Aug 2021Worldwide, there is increasing evidence that shows a decline in pollinators, limiting crop pollination and production. However, it is unclear to what extent Chinese...
Worldwide, there is increasing evidence that shows a decline in pollinators, limiting crop pollination and production. However, it is unclear to what extent Chinese agriculture could be impacted by pollinator deficits. Data for 84 major crops in China between 1961 and 2018 were analyzed for the temporal trends in crop area and production, agricultural economic contribution of pollination, crop yield deficits, and honey bee pollination demand. We found a rapid increase in agricultural dependence on insect pollinators: both the cultivated area and total production of pollinator-dependent crops increased faster than those of pollinator-independent crops during 1961-2018. The total economic value of pollination amounted to US$ 106.08 billion in 2010, representing 19.12% of the total production value of Chinese agriculture, approximately twice the 9.5% value estimated for global agriculture. Crops with higher pollinator dependence showed greater mean growth in cultivated area than those with lower dependence, but lower mean growth of crop production and yield. Crop yield growth was also more unstable with increasing pollinator dependence. The minimum pollination demand for honey bee colonies was about three times the stock of honey bee colonies available in 2018. Furthermore, we found a decline in crop yield deficit with the increase in honey bee colony pollination service capacity. We considered that the shortage of pollinators resulted in the yield deficits for pollinator-dependent crops. Future increase in the area of pollinator-dependent crops will increase the need for more pollinators, suggesting the importance of implementing measures to protect pollinators to ensure a better-secured future for agricultural production in China.
Topics: Agriculture; Animals; Bees; China; Crops, Agricultural; Insecta; Pollination
PubMed: 34050664
DOI: 10.1093/jee/toab100 -
Oecologia Oct 2023Pollinators mediate interspecific and intraspecific plant-plant indirect interactions (competition vs. facilitation) via density-dependent processes, potentially shaping...
Pollinators mediate interspecific and intraspecific plant-plant indirect interactions (competition vs. facilitation) via density-dependent processes, potentially shaping the dynamics of plant communities. However, it is still unclear which ecological drivers regulate density-dependent patterns, including scale, pollination niches (i.e., the main pollinator functional group) and floral attractiveness to pollinators. In this study, we conducted three-year field observations in Hengduan Mountains of southwest China. By gathering data for more than 100 animal-pollinated plant species, we quantified the effect (positive vs. negative) of conspecific and heterospecific flower density on pollination at two scales: plot-level (4 m) and site-level (100-5000 m). Then, we investigated how pollination niches and floral attractiveness to pollinators (estimated here as average per-flower visitation rates) modulated density-dependent pollination interactions. Pollinator visitation depended on conspecific and heterospecific flower density, with rare plants subjected to interspecific competition at the plot-level and interspecific facilitation at the site-level. Such interspecific competition at the plot-level was stronger for plants pollinated by diverse insects, while interspecific facilitation at the site-level was stronger for bee-pollinated plants. Moreover, we also found stronger positive conspecific density-dependence for plants with lower floral attractiveness at the site-level, meaning that they become more frequently visited when abundant. Our study indicates that the role of pollination in maintaining rare plants and plant diversity depends on the balance of density-dependent processes in species-rich communities. We show here that such balance is modulated by scale, pollination niches and floral attractiveness to pollinators, indicating the context-dependency of diversity maintenance mechanisms.
Topics: Bees; Animals; Pollination; Plants; Flowers; Insecta; China
PubMed: 37823959
DOI: 10.1007/s00442-023-05461-3 -
PloS One 2022Cross-pollination can increase fruit production in both self-incompatible and self-compatible fruit crops. However, it is often unclear what proportions of the fruit...
Cross-pollination can increase fruit production in both self-incompatible and self-compatible fruit crops. However, it is often unclear what proportions of the fruit crop result from cross-pollination. We quantified the proportion of cross-pollinated seeds and the proportion of fertilised seeds in two strawberry cultivars, Red Rhapsody and Sundrench, at increasing distances from a cross-pollen source. We assessed whether fully self-pollinated fruit and partly cross-pollinated fruit differed in fruit size, colour, firmness, Brix and acidity. We also assessed whether fruit size and quality were affected by the number or percentage of fertilised seeds. Almost all seeds of both cultivars resulted from self-pollination (~98%), even at only 1 m from a cross-pollen source. Distance from a cross-pollen source did not affect the proportion of partly cross-pollinated fruit or the proportion of cross-pollinated seeds per fruit. The mass and diameter of fully self-pollinated Sundrench fruit, and the redness and Brix of fully self-pollinated Red Rhapsody fruit, were higher than partly cross-pollinated fruit. Fruit mass, length and diameter increased, and acidity decreased, with increasing numbers of fertilised seeds in both cultivars. Fruit mass also increased with the percentage of fertilised seeds. Our results show that cross-pollination was not required for Red Rhapsody and Sundrench fruit production, and that cross-pollination was a rare occurrence even close to cross pollen source. Self-pollen deposition on stigmas is required to maximise the number of fertilised seeds, and consequently fruit size and quality. Our research indicates that bees improve strawberry fruit size by increasing the number of stigmas that receive pollen. Our results suggest that placing bee hives on strawberry farms during flowering and establishing nearby pollinator habitat to support wild pollinators could improve strawberry yield and fruit quality.
Topics: Animals; Bees; Fragaria; Fruit; Paternity; Pollination; Seeds
PubMed: 36099262
DOI: 10.1371/journal.pone.0273457 -
Ecological Applications : a Publication... Dec 2022Urbanization poses a major threat to biodiversity and food security, as expanding cities, especially in the Global South, increasingly compete with natural and...
Urbanization poses a major threat to biodiversity and food security, as expanding cities, especially in the Global South, increasingly compete with natural and agricultural lands. However, the impact of urban expansion on agricultural biodiversity in tropical regions is overlooked. Here we assess how urbanization affects the functional response of farmland bees, the most important pollinators for crop production. We sampled bees across three seasons in 36 conventional vegetable-producing farms spread along an urbanization gradient in Bengaluru, an Indian megacity. We investigated how landscape and local environmental drivers affected different functional traits (sociality, nesting behavior, body size, and specialization) and functional diversity (functional dispersion) of bee communities. We found that the functional responses to urbanization were trait specific with more positive than negative effects of gray area (sealed surfaces and buildings) on species richness, functional diversity, and abundance of most functional groups. As expected, larger, solitary, cavity-nesting, and, surprisingly, specialist bees benefited from urbanization. In contrast to temperate cities, the abundance of ground nesters increased in urban areas, presumably because larger patches of bare soil were still available beside roads and buildings. However, overall bee abundance and the abundance of social bees (85% of all bees) decreased with urbanization, threatening crop pollination. Crop diversity promotes taxonomic and functional diversity of bee communities. Locally, flower resources promote the abundance of all functional groups, and natural vegetation can maintain diverse pollinator communities throughout the year, especially during the noncropping season. However, exotic plants decrease functional diversity and bee specialization. To safeguard bees and their pollination services in urban farms, we recommend (1) preserving seminatural vegetation (hedges) around cropping fields to provide nesting opportunities for aboveground nesters, (2) promoting farm-level crop diversification of beneficial crops (e.g., pulses, vegetables, and spices), (3) maintaining native natural vegetation along field margins, and (4) controlling and removing invasive exotic plants that disrupt native plant-pollinator interactions. Overall, our results suggest that urban agriculture can maintain functionally diverse bee communities and, if managed in a sustainable manner, be used to develop win-win solutions for biodiversity conservation of pollinators and food security in and around cities.
Topics: Bees; Animals; Farms; Pollination; Biodiversity; Urbanization; Crops, Agricultural; Ecosystem
PubMed: 35751512
DOI: 10.1002/eap.2699