Plant Reproductive Strategies Research Articles

Dactyliform appendage contributes to delayed selfing in the diminutive orchid Stigmatodactylus sikokianus

Societal Impact StatementUnderstanding plant reproductive strategies is vital for conserving endangered species. This study reveals a novel self‐pollination mechanism in the diminutive orchid Stigmatodactylus sikokianus, facilitated by the movement of a finger‐like appendage beneath the stigma. While this less‐than‐1‐mm‐long structure inspired the name Stigmatodactylus, its ecological function remained unknown for over 130 years—until now. The findings suggest that this appendage facilitates delayed self‐pollination, likely ensuring reproductive success under conditions of pollinator scarcity. Furthermore, the research highlights the value of integrating taxonomy with functional morphology to advance our understanding of pollination ecology.Summary Orchidaceae is one of the largest and most morphologically diverse plant families, largely due to intricate relationships with pollinators. However, autonomous self‐pollination is relatively common, likely as an adaptation to limited pollinator availability. This study examines the reproductive mechanism of the diminutive orchid Stigmatodactylus sikokianus, focusing on the finger‐like appendage beneath the stigma. The reproductive biology of S. sikokianus was investigated through pollination observations, artificial pollination experiments, and detailed studies of column morphology. Pollination experiments demonstrated that S. sikokianus primarily relies on autonomous self‐pollination, as indicated by high fruit set in bagged flowers and no fruit set in emasculated ones. Microscopic analysis revealed that the dactyliform appendage arcs toward the stigma, maintaining its straight structure, and eventually adheres to the stigma surface, allowing contact between the appendage apex and pollinia. UV microscopy showed thick bundles of pollen tubes penetrating the appendage adhered to the stigma and reaching the base of the column. The absence of pollen tube formation before contact between the appendage apex and pollinia suggests that autogamy occurs exclusively through the appendage at a later flowering stage. This study uncovers a novel self‐pollination mechanism in orchids, where the movement of the stigma appendage likely facilitates delayed selfing. This mechanism ensures seed production and likely reproductive success in S. sikokianus, enabling it to thrive in shaded environments with limited pollinator availability. The discovery highlights the value of integrating taxonomic and ecological approaches, as morphological traits provide valuable insights into species life histories.

Use of woody species in the Caatinga dry forest may lead to higher vulnerability to extirpation: An assessment based on ethnobiological, reproductive and conservation criteria

Tropical forests play an important role in maintaining, replenishing and conserving a large portion of the planet's biodiversity. However, these forests have been converted into anthropic landscapes, threatening the persistence of wildlife. The exploitation of forest products can result in different ecological impacts at different levels of biological organization. In this study, we propose a vulnerability index to examine the susceptibility of woody plants used by locals in a human-modified landscape of the Caatinga dry forest (i.e., the Catimbau National Park). We contrasted patterns of (1) plant use by local people (risk of use, collection risk, local importance, and diversity of use), (2) plant reproductive strategies (pollination, sexual and reproductive systems, dispersal mode, flowering and fruiting phenology), and (3) the conservation status of the plant species. We combined this information to propose a vulnerability index expressing species sensitivity to human disturbances in 14 regenerating and 14 old-growth forest stands. We tested the hypothesis that regenerating forest stands will harbor more vulnerable plant species compared to old-growth forest stands. Among the 119 plant species registered in regenerating and old-growth forest stands, 80 species (67.2 %) were recorded as useful for local people in Caatinga. Specifically, about 71.8 % and 70.5 % are exploited by the rural population for some type of use in regenerating and old-growth forest stands, respectively. The most frequent type of use was medicinal, followed by construction and fuel in both regenerating and old-growth forest stands. Regarding the potentially collected plant parts, the total removal of the individual and collection of leaves exhibited similar and higher relevance in regenerating, while leaves were the most collected part in old-growth forest stands. Of the 80 plant species analyzed, 62 % and 58.5 %, respectively, were classified as exhibiting moderate and high vulnerability to extirpation in regenerating and old-growth forest stands; thus not supporting our hypothesis. Our results suggest that in the Caatinga dry forest, (1) woody plant species responsible for forest regeneration in the context of slash-and-burn agriculture are exploited for multiple uses, (2) medicinal use is the main type of use of woody plants occurring in regenerating and old-growth forest stands, (3) total removal of the individual and collection of leaves were the most collected plant parts, and (4) both regenerating and old-growth forest stands showed a high vulnerability to human disturbances in the study area. In the long term, the exploitation of vulnerable plant species may negatively affect the composition and structure of the community and, consequently, the rate and trajectory of succession. It can be expected that as populations of vulnerable plant species are reduced or extirpated from the community, ecological interactions such as pollination and dispersal, which are key to ecosystem maintenance, will change along with the services provided.

Responses of soil seed bank and its above-ground vegetation to various reclamation patterns

Coastal land reclamation has become a primary strategy for alleviating conflicts between human development and land resource utilization. However, anthropogenic activities associated with land reclamation inevitably result in significant changes to coastal wetland ecosystems. Previous studies have mainly focused on the ecological consequences of land reclamation on above-ground vegetation, while overlooking the distinctions between different reclamation patterns and the critical role of soil seed bank in maintaining ecosystem stability. In this study, the responses of soil seed bank and vegetation to various reclamation patterns, as well as the factors influencing changes in seed bank characteristics, were analyzed in a natural coastal wetland (NCW), a reclaimed wetland with sea embankments constructed on native wetland (SEW), and another reclaimed wetland formed through land reclamation from the sea (LRW). These findings suggest that seed banks and their vegetation adopt different adaptation strategies under various reclamation patterns. In the NCW, the proportion of non-halophytes (1.39%), diversity, and density of the seed bank were at their lowest levels, whereas the species compositions derived from the seed bank and vegetation were very similar (similarity coefficient = 0.67). Conversely, the seed bank in the SEW demonstrated the highest species diversity, which differed significantly from the species composition of its above-ground vegetation (similarity coefficient = 0.21). However, the highest proportion of non-halophytes (36.60%), vegetation diversity, and seed bank density occurred in LRW. Furthermore, differences in seed bank characteristics under different reclamation patterns may be related to changes in soil salinity and plant reproductive strategies after reclamation. Adjusting reclamation patterns and restoring soil properties could potentially optimize the types of local plant species and their distribution in reclaimed areas.

Seed predation-induced Allee effects, seed dispersal and masting jointly drive the diversity of seed sources during population expansion.

The environmental factors affecting plant reproduction and effective dispersal, in particular biotic interactions, have a strong influence on plant expansion dynamics, but their demographic and genetic consequences remain an understudied body of theory. Here, we use a mathematical model in a one-dimensional space and on a single reproductive period to describe the joint effects of predispersal seed insect predators foraging strategy and plant reproduction strategy (masting) on the spatio-temporal dynamics of seed sources diversity in the colonisation front of expanding plant populations. We show that certain foraging strategies can result in a higher seed predation rate at the colonisation front compared to the core of the population, leading to an Allee effect. This effect promotes the contribution of seed sources from the core to the colonisation front, with long-distance dispersal further increasing this contribution. As a consequence, our study reveals a novel impact of the predispersal seed predation-induced Allee effect, which mitigates the erosion of diversity in expanding populations. We use rearrangement inequalities to show that masting has a buffering role: it mitigates this seed predation-induced Allee effect. This study shows that predispersal seed predation, plant reproductive strategies and seed dispersal patterns can be intermingled drivers of the diversity of seed sources in expanding plant populations, and opens new perspectives concerning the analysis of more complex models such as integro-difference or reaction-diffusion equations.

Propagation strategies of Deyeuxia angustifolia in heterogeneous habitats

Plants utilize different strategies in different environments to maximize population expansion. Understanding plant reproductive strategies in heterogeneous habitats is therefore important for explaining plant ecological adaptability, and for effectively managing and conserving ecosystems. We wanted to explore the reproductive strategy transformation of D. angustifolia in heterogeneous habitats, as well as the environmental factors driving and affecting its reproductive characteristics. To do this we measured the reproductive characteristics of D. angustifolia, as well as the soil physical and chemical properties of these heterogeneous habitats. The density, biomass per unit area, and proportion of aboveground biomass in swampy meadows were significantly higher compared to other habitats. The proportion of rhizome node buds gradually increased from swampy to typical to miscellaneous grass meadows, while the proportion of tillering node buds decreased. The allocation of sexual reproduction within D. angustifolia populations was significantly and positively correlated with plant rhizome biomass and negatively correlated with the number of tillering node buds. The propagation strategies of D. angustifolia in heterogeneous habitats were consistent with CSR theory (Competitor, Stress-tolerator, and Ruderal). The proportions of inflorescence (2.07 ± 0.52%; 1.01 ± 0.15%) and root (23.8 ± 1.5%; 19.6 ± 1.4%) biomass in miscellaneous and typical meadows were high, which tended toward the “Ruderal” adaptation strategy. In swampy meadow, D. angustifolia invested mostly in vegetative growth to produce tiller node buds (14426.67 buds/m2; 46%) and ramets (1327.11 ± 102.10 plants/m2), which is characteristic of the “Competitor” strategy. Swamp D. angustifolia resisted flooding by maintaining a resource balance in its body, and was therefore biased toward the “Stress-tolerator” strategy. Environmental factors accounted for 74.63% of reproductive characteristic variation, in which the interpretative proportions of soil water content, dissolved organic carbon, ammonia nitrogen, and nitrate nitrogen were significant (p < 0.01). When soil water content, dissolved organic carbon, and nitrate nitrogen increased, D. angustifolia tended toward the C strategy; in contrast, when soil water content decreased, amine nitrogen and available phosphorus increased, and D. angustifolia tended toward the R strategy. In a stressful environment, the escape mechanism constitutes an increased rhizome and sexual reproduction investment. In contrast, for suitable habitats, tillering node buds increased in order to expand the population via new plant production, which was the propagation strategy of D. angustifolia in heterogeneous habitats.

Latitudinal variations of seed functional traits of Phragmites australis in Chinese coastal marsh

Functional traits of seeds reflect plant reproductive strategies adapting to environmental changes, which is an evolutionary behavior in natural selection and genetics. Study on seed functional traits is of great significance to deeply understand the long-term adaptive evolution of plants and seeds. We measured seed functional traits of a main indigenous species Phragmites australis, including seed size, seed weight, seed set, and seed production, in nine coastal marshes of the six provinces/cities along the coastal zone of China (21°29'-40°57' N), and analyzed latitudinal variations of functional traits. The results showed that seed functional traits of P. australis in Chinese coastal marshes varied significantly with latitude and that there were significant correlations among different traits. Seed size (including seed length, seed width, seed shape index, aspect ratio, and seed surface area), and 100-seed weight showed significant quadratic function relation with latitude, which firstly decreased and then increased with the increases of latitude, while seed setting rate firstly increased and then reduced. There was a trade-off between the number and size of P. australis seeds. Seed production per unit area significantly increased with latitude. Results of stepwise regression analysis showed that climatic factors were the main driver resulting in the difference of seed functional traits of P. australis between latitudes, followed by pH and salinity of soil porewater.

Understanding the appearance of heterospory and derived plant reproductive strategies in the Devonian

AbstractThe evolution of different spore size classes, or heterospory, is a fundamental reproductive innovation in land plants. The appearance of heterospory is particularly notable during the Devonian, when most known origins of the trait occur. Here we provide a perspective on the evolution of heterospory during this time interval, particularly from the late Early Devonian through the Middle Devonian (Emsian to Givetian Stages; 408–383 Ma), which shows an unusually high concentration of heterospory origins. We use theoretical considerations and compilations of fossil and extant spore sizes to suggest that the basic features of most heterosporous lineages, large spores and gametophytes that mature within the spore wall, are difficult to evolve in combination, because large spores disperse poorly but small spores cannot support a functional gametophyte developing within their walls; evolving spores between 100 and 200 microns in diameter appears to represent a particularly important barrier for the evolution of heterospory. We then discuss why this barrier may have been lower in the Devonian, noting that the appearance and spread of heterospory is coincident with the emergence of peat-accumulating wetland habitats. We suggest that more widespread wetland habitats would have generally lowered barriers to the evolution of heterospory by reducing dispersal limitation in larger spores. Ultimately, we suggest that the initial evolution of heterospory may be explained by major changes in sedimentology, thought to have been driven by plant evolution itself, that increased the diversity of terrestrial depositional environments and led to a greater number of habitats where large spores could be successful.

Ecological importance of the Myrtaceae in New Zealand's natural forests

AbstractAimsThe Myrtaceae is a woody family that plays an important role in forest ecosystems globally. The recent spread of myrtle rust, caused by a fungal pathogen (Austropuccinia psidii), from its native South America into New Zealand (NZ), highlights the need to quantify the ecological importance of Myrtaceae in NZ woody ecosystems.LocationNew Zealand.MethodsUsing NZ nationwide forest and shrubland inventory data, collected from 2009 to 2014, we quantified the ecological importance of Myrtaceae based on its richness and abundance relative to co‐occurring woody families. We then explored how climate and forest stand structure affect Myrtaceae importance in general and by tribe and growth form. Finally, we compared functional traits associated with plant growth and reproductive strategies with other dominant woody families and determined Myrtaceae's contributions to community‐weighted mean (CWM) trait values.ResultsMyrtaceae occurred in 74% of the study plots and its importance value was the second highest across the woody families. It was the only one in which climbers substantially contributed to the importance value (17%). Greater Myrtaceae importance values were associated with warmer and more mesic climates and early forest successional stages. Climate associations were similar within tribes and growth forms, whereas forest structure effects varied. Myrtaceae was functionally distinct from most co‐occurring woody families. Contributions to CWM wood density, maximum height, and specific leaf area values were significantly greater than expected from its importance value.ConclusionsMyrtaceae is the second most ecologically important woody family in NZ woody ecosystems. The family has a distinctive functional trait spectrum associated with high wood density and tall stature, ensuring large and enduring carbon stocks. There will potentially be large and deleterious outcomes in forest ecosystems if taxon‐specific pathogens, such as Austropuccinia psidii, spread and significantly reduce Myrtaceae importance.

Fire history and weather interact to determine extent and synchrony of mast-seeding in rhizomatous scrub oaks of Florida.

In disturbance-prone ecosystems, fitness consequences of plant reproductive strategies are often determined by the relative timing of seed production and disturbance events, but the role of disturbances as proximate drivers of seed production has been overlooked. We use long-term data on seed production in Quercus chapmanii, Q. geminata and Q. inopina, rhizomatous oaks found in south central Florida's oak scrub, to investigate the role of fire history and its interaction with weather in shaping acorn production and its synchrony. Acorn production increased with the time since last fire, combined with additive or interactive effects of spring precipitation (+) or drought (-). Furthermore, multiple matrix regression models revealed that ramet pairs with shared fire history were more synchronous in seed production than ones that burned in different years. Long-term trends suggest that increasingly drier spring weather, in interaction with fire frequency, may drive a decline of seed production. Such declines could affect the community of acorn-reliant vertebrates in the Florida scrub, including endangered Florida scrub-jays (Aphelocoma coerulescens). These results illustrate that fire can function as a proximate driver of seed production in mast-seeding species, highlighting the increasingly recognized importance of interactions among reproductive strategies and disturbance regimes in structuring plant populations and communities. This article is part of the theme issue 'The ecology and evolution of synchronized seed production in plants'.

Long-distance dispersal events rather than growth habit and life-history traits affect diversification rate in tribe Apieae (Apiaceae)

AbstractFactors influencing diversification rates may be of intrinsic (e.g. morphological novelties) or extrinsic (e.g. long-distance dispersal, availability of ecological niches) nature. Growth habit may influence diversification rates because herbaceous plants often have shorter generation times and a more pronounced r reproductive strategy than their woody relatives. We examined life history and habit evolution, wood anatomy and biogeographical history of Apiaceae tribe Apieae in conjunction with diversification rate analysis to explore which factors may have affected clade species richness and to elucidate the constraints on the evolution of secondary woodiness in this group. We demonstrate that diversification rates are similar in morphologically homogeneous and diverse clades and in herbaceous and woody lineages. The only clade with a significantly elevated diversification rate is Southern Hemisphere Apium, in which diversity probably resulted from several long-distance dispersal events. We also show that wood anatomy in herbaceous and woody species does not differ considerably regardless of their continental or insular origin, but it is affected by stem architecture and plant reproductive strategy. As the taxonomy of Apieae suffers from inflation with numerous monotypic genera, we propose to include Canaria in Rutheopsis, and Foeniculum, Schoenoselinum, Ridolfia and Pseudoridolfia in Anethum.

Prior disturbance legacy effects on plant recovery post‐high‐severity wildfire

AbstractLarge, high‐severity wildfires are an important component of disturbance regimes around the world and can influence the structure and function of forest ecosystems. Climatic changes and anthropogenic disturbances have altered global disturbance patterns and increased the frequency of high‐severity wildfires worldwide. While the recovery of plant communities at different successional stages after fire is well known, the influence of prior disturbances and stand age is poorly understood. Despite this, high‐intensity wildfires can produce long‐lasting legacy effects, which can influence the resistance and resilience of ecosystems. Here, we quantified the influence of prior stand age and disturbance history on the recovery of plant communities in the Mountain Ash and Alpine Ash forests of south‐eastern Australia after high‐severity wildfire. Specifically, controlling for stand age, we compared the abundance (percent cover) of different plant life forms and reproductive strategies in forests that were, at the time of high‐severity wildfire in 2009, “young” (28–35 yr old and previously logged), “mixed” age (26, 70–83, >150 yr old), “mature” (70–83 yr old), and “old‐growth” (>150 yr old). We uncovered evidence that the legacy of prior disturbance and stand age at the time of high‐severity wildfire can influence the recovery of plant communities in early successional forests. Specifically, we found that “young” forests burnt in 2009 had a higher abundance of ruderal and graminoid species, but had a lower abundance of persistent, onsite seeders, including Acacia and eucalypt species, relative to “old‐growth” forests burnt in 2009. “Mature” aged forests burnt in 2009 also had a lower abundance of Acacia, eucalypt, and shrub species, relative to “old‐growth forests” burnt in 2009. Our findings provide evidence of advanced recovery in forests that were older when burnt by high‐severity wildfire, relative to younger forests burnt by the same wildfire. Further, we also demonstrate the influence of different environmental conditions on plant communities. In a period of rapid, global, environmental change, our study provides insights into the recovery of plant communities post‐wildfire with implications for forest management. Further, our findings suggest that predicted increases in the frequency of high‐severity wildfires may have consequences for forest regeneration.

Omniastrobus gen. nov., an Emsian Plant with Implications for the Evolution of Heterospory in the Early Devonian

Premise of research. Heterospory, or the production of different spore size classes, is a key aspect of advanced vascular plant reproductive strategies. Heterospory is widespread across plant linea...

Reproductive biology of Syagrus coronata (Arecaceae): sex-biased insect visitation and the unusual case of scent emission by peduncular bracts.

Several monoecious species of palms have developed complex strategies to promote cross-pollination, including the production of large quantities of floral resources and the emission of scents that are attractive to pollinators. Syagrus coronata constitutes an interesting model with which to understand the evolution of plant reproductive strategies in a monoecious species adapted to seasonally dry forests. We monitored blooming phenology over 1year, during which we also collected and identified floral visitors and putative pollinators. We identified potential floral visitor attractants by characterizing the scent composition of inflorescences as well as of peduncular bracts, during both male and female phases, and the potential for floral thermogenesis. Syagrus coronata produces floral resources throughout the year. Its inflorescences are predominantly visited by a diverse assortment of small-sized beetles, whose richness and abundance vary throughout the different phases of anthesis. We did not find evidence of floral thermogenesis. A total of 23 volatile compounds were identified in the scent emitted by the inflorescences, which did not differ between male and female phases; whereas the scent of the peduncular bracts was composed of only 4-methyl guaiacol, which was absent in inflorescences. The composition of floral scent chemistry indicates that this palm has evolved strategies to be predominantly pollinated by small-sized weevils. Our study provides rare evidence of a non-floral scent emitting structure involved in pollinator attraction, only the second such case specifically in palms. The peculiarities of the reproductive strategy of S. coronata might play an important role in the maintenance of pollination services and pollen dispersion.

Phenotypic plasticity in resource allocation to sexual trait of alligatorweed in wetland and terrestrial habitats

Environmental heterogeneity in resource availability affects invasive plant reproductive strategies and resource allocation to reproduction. Here, we conducted two field surveys to examine the effect of wetland and terrestrial habitats on inflorescence production and resource allocation to inflorescence of the amphibious invasive plant Alternanthera philoxeroides in its invasive range (China). We also specifically examined the effects of water availability, fertilizer application, and plant density (space) in a greenhouse experiment. In field surveys, inflorescence biomass, normal monoclinous flowers and ratio of inflorescences to shoots of plants from wetlands were about 2.4-, 0.8- and 1.3-fold higher than those from terrestrial habitats, respectively. In greenhouse experiment, plants with higher fertilizer application and lower competition conditions produced more inflorescences, and had a lower ratio of roots to shoots and a comparable ratio of inflorescences to shoot and root. Furthermore, water availability had a significant interactive effect when combined with fertilizer level or plant density on inflorescence production and resource allocation. Together, our results indicate that high resources, such as those found in wetland habitats, favor both vegetative growth and sexual trait in A. philoxeroides. However, in terrestrial habitats where resources are relatively poor, the invader can adapt to the environment by allocating more resources to vegetative growth for clonal reproduction and less resources for sexual trait. This phenotypic plasticity in resource allocation likely facilitates the plant to invade heterogeneous wetlands and terrestrial environments.

A subterranean ecosystem-engineering rodent influences plant emergence and reproductive strategy in a high-altitude cold desert

AbstractPlant emergence from seed banks and from asexual reproduction could be strongly influenced by environmental and biological factors. Among environmental factors, animal disturbances deserve special consideration. In this study we test the hypothesis that disturbances resulting from the burrowing activity of Ctenomys affect plant emergence (sexual and asexual) in the south of the cold Puna desert. Richness and abundance of seedlings and sprouts growing in areas disturbed or undisturbed by Ctenomys were recorded at the beginning and at the end of the vegetative season. In general terms, the activity of Ctenomys does not affect richness of emerging species, but does have a significant influence on the type of emergence. Analyses between areas revealed that seedling emergence was significantly higher than sprout emergence in areas showing Ctenomys activity, whereas no significant differences were found between types of emergence in undisturbed areas. Although vegetative emergence was important, plant emergence from seeds appears to be relevant to the recolonization of areas disturbed by Ctenomys.

Macroevolutionary patterns in seed component mass and different evolutionary trajectories across seed desiccation responses.

Seed coat and seed reserve show substantial mass variation, play different roles in plant life strategies and are shaped by different selective forces. However, remarkably little is known about the macroevolution of the relative allocation in seed components and its influence on important ecophysiological processes. Using phylogenetic comparative methods and evolutionary modelling approaches, we modelled mass changes in seed components along individual lineages for 940 species and compared the patterns across seed desiccation responses. Seed component allocation was driven primarily by changes in reserve mass rather than coat mass, as evolutionary rates in reserve mass significantly outpaced those in coat mass. Although the scaling patterns between reserve mass and coat mass were similar across desiccation responses, desiccation-sensitive seeds allocated more and evolved faster in reserve compared to desiccation-tolerant seeds. The findings emphasize the relative importance of reserve to coat in the evolution of plant reproductive strategies, revealing potential ecological advantages gained by enlarged reserve. As the first quantification of the evolutionary tempo and mode of seed component mass, our study allows a detailed interpretation of evolutionary pathways underlying seed storage behaviours and advances the understanding of the evolution of desiccation sensitivity in seeds.

Physical dormancy and soil seed bank dynamics in seeds of Melilotus albus (Fabaceae)

Information on seed germination and the soil seed bank of a species is important because it contributes to a better understanding of plant reproductive strategies. Melilotus albus (Fabaceae) is considered valuable for honey production and is frequently cultivated as livestock forage. However, it is difficult to germinate M. albus seeds. The primary goal of the present study was to determine the environmental requirements for breaking seed dormancy and the dynamics of soil seed bank. The results indicate that seeds of M. albus have a water impermeable seed coat which can be penetrated by scarification or alternating wet heat and ice water cycles; however, wet heat or dry heat alone were ineffective. After receiving 30 cycles of alternating wet heat and ice water treatments, cracks formed in the lens of seeds. Under natural precipitation and temperature, > 60% of the seedlings emerged in spring. A persistent soil seed bank formed and most seeds were found in the 0–2 cm soil layer. Our findings indicate that seeds of M. albus have physical dormancy; persistence of the seed bank might spread risks associated with a specific seed cohort over multiple years.

Morphological specialization of heterantherous Rhynchanthera grandiflora (Melastomataceae) accommodates pollinator diversity.

The tropical Melastomataceae are characterized by poricidal anthers which constitute a floral filter selecting for buzz-pollinating bees. Stamens are often dimorphic, sometimes with discernible feeding and pollinating functions. Rhynchanthera grandiflora produces nectarless flowers with four short stamens and one long stamen; all anthers feature a narrow elongation with an upwards facing pore. We tested pollen transfer by diverse foraging bees and viability of pollen from both stamen types. The impact of anther morphology on pollen release direction and scattering angle was studied to determine the plant's reproductive strategy. Medium-sized to large bees sonicated flowers in a specific position, and the probability of pollen transfer correlated with bee size even among these legitimate visitors. Small bees acted as pollen thieves or robbers. Anther rostrum and pore morphology serve to direct and focus the pollen jet released by floral sonication towards the pollinator's body. Resulting from the ventral and dorsal positioning of the short and long stamens, respectively, the pollinator's body was widely covered with pollen. This improves the plant's chances of outcrossing, irrespective of which bee body part contacts the stigma. Consequently, R. grandiflora is also able to employ bee species of various sizes as pollen vectors. The strategy of spreading pollen all over the pollinator's body is rather cost-intensive but counterbalanced by ensuring that most of the released pollen is in fact transferred to the bee. Thus, flowers of R. grandiflora illustrate how specialized morphology may serve to improve pollination by a functional group of pollinators.

Parallel evolution of arborescent carrots (Daucus) in Macaronesia.

PremiseDespite intensive research, the pathways and driving forces behind the evolution of derived woodiness on oceanic islands remain obscure. The genus Daucus comprises mostly herbs (therophytes, hemicryptophytes) with few rosette treelets (chamaephytes) endemic to various Macaronesian archipelagos, suggesting their independent evolution. To elucidate the evolutionary pathways to derived woodiness, we examined phylogenetic relationships and the habit and secondary xylem evolution in Daucus and related taxa.MethodsSixty taxa were surveyed for molecular markers, life history, and habit traits. Twenty‐one species were considered for wood anatomical characters. A dated phylogeny was estimated using Bayesian methods. The evolution of selected traits was reconstructed using parsimony and maximum likelihood.Results Daucus dispersed independently to the Canary Islands (and subsequently to Madeira), Cape Verde, and the Azores in the late Miocene and Pleistocene. Life span, reproductive strategy, and life form were highly homoplastic; the ancestor of Daucus was probably a monocarpic, biennial hemicryptophyte. Rosette treelets evolved independently in the Canarian‐Madeiran lineage and in Cape Verde, the latter within the last 0.13 Myr. Treelets and hemicryptophytes did not differ in wood anatomy. Pervasive axial parenchyma in wood occurred more often in polycarpic rather than monocarpic species.ConclusionsLife span and life form in Daucus are evolutionarily labile and may change independently of wood anatomy, which is related to plant reproductive strategy rather than to life form. Insular woodiness may evolve rapidly (as demonstrated in D. bischoffii), and in Daucus, it does not seem to be an adaptation to lower the risk of xylem embolism.

Nectar features, diurnal and nocturnal pollinators, and male fitness in Qualea grandiflora (Vochysiaceae)

Nectar production in flowers has been associated with pollination systems and seen as part of plant reproductive strategies. But other factors may have a role on nectar features and its efficacy as reward. We investigated pollination system of Qualea grandiflora, the most widespread woody species of Cerrado, the Neotropical savannas in Central Brazil, focusing on nectar features, their relationship with nocturnal and diurnal pollinators and how nectar affects male fitness, measured through pollen removal. Qualea grandiflora flowers during rainy season; anthesis starts at dusk, with a slightly sweet scent, pollen release and receptive stigma. Flowers remained opened until next evening and were visited and pollinated by a wide range of nocturnal and diurnal animals. Hawk moths were more frequent and responsible for most Q. grandiflora male fitness. Nectar was secreted during the night and early morning, with maximum accumulated volume up to 20.9 μl. Sugar concentration (23.12%) and amount (1.79 mg) remained constant during flower lifespan. No signals of active nectar resorption were observed. Nectar sugar composition was sucrose dominant during the night, and sucrose and hexose rich during the day. Standing crop measurements indicated an important proportion of nectar intake by flower visitors. Qualea grandiflora seemed to synchronize its floral and nectar features with hawk moths. However, nectar composition encompasses general preferences by both diurnal and nocturnal pollinators, assuring a mixed pollination system which seems well adapted to the species continental-scale distribution.