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The Various Contrivances by Which Orchids Are Fertilized by Insects
... Floral traits of angiosperms, such as colour, odour, shape, and size, usually have functional roles in pollinator attraction and pollen transfer, evolving in response to directional pollinatormediated selection and maintained similarly by stabilizing selection (Darwin 1877;Stebbins 1951;Harder & Johnson 2009;Caruso et al. 2019). A key trait that has attracted recent attention is flower orientation, which is the angle of a flower in relation to the ground (e.g. ...
... It is a basal and genetically dominant condition in the Orchidaceae and, despite some reversals, is almost ubiquitous in the family (Dressler 1981;Kim et al. 2010;Christenhusz & Byng 2016). Because of its lowermost position resulting from resupination, the labellum serves as a landing platform and is the most modified perianth segment of the orchids, often being extended into a spur or pouch (Darwin 1877;Ames 1938;Hill 1939 During field studies with the lady's slipper orchid, Phragmipedium vittatum (Vell.) Rolfe (Cypripedioideae), we noted that some flowers fail to resupinate and remain trapped between the bract and the stem Fig. 1). ...
... For instance, in the basal subfamily Apostasioideae of the Orchidaceae, resupination does not occur in the actinomorphic genus Apostasia but is present in the zygomorphic Neuwiedia (Kocyan & Endress 2001). In orchids, zygomorphy is closely linked with the position of the median petal, known as the labellum (Darwin 1877;Ames 1938;Van der Pijl & Dodson 1966; Mondrag on-Palomino & Theißen 2009). Although the labellum can attract and reward pollinators, one of its major functions in the classic orchid 'bauplan' is that it serves as a landing platform in resupinate flowers (Darwin 1877;Ames 1938;Van der Pijl & Dodson 1966; Mondrag on-Palomino & Theißen 2009). ...
• In many families, plants undergo floral resupination by twisting through approximately 180º during floral development so that the flower is effectively positioned upside down. In most orchids, resupination results in the median petal (i.e. the labellum) becoming lowermost, which plays a crucial role in pollination by serving as a landing platform or as a trapping device or both. Incomplete resupination is predicted to lead to reduced pollination, although tests of this assumption are still lacking.
• We investigated the effect of resupination using Phragmipedium vittatum, a rare lady's slipper orchid whose specialized labellum forms a trapping device. First, we surveyed the natural occurrence of incomplete resupination. Then, we manipulated flowers into non- (≈ 0º), half- (≈ 90º), and fully resupinate (≈ 180º) positions to test the effect of orientation on pollen smear removal and deposition by pollinators (female hoverflies).
• We found that ca. 10 % of flowers in the natural population were not fully resupinate, being either non- (upward, 0º - 60º) or half-resupinate (sideward, 60º - 120º). The change in orientation prevented the effectiveness of pollination by hoverflies since no pollen smear removal or deposition were found in flowers from non- and half-resupinate treatments. Although these flowers still attracted hoverflies, they were not trapped effectively.
• As this orchid is incapable of autonomous self-pollination, flowers that do not resupinate fail to set fruits. These results highlight the importance of correct floral orientation provided by resupination to ensure pollination in orchids and other resupinate flowers.
... These morphological changes have occurred in concert with ecological changes in principal pollinators or evolutionary changes in pollinator morphology (usually proboscis length). The ecological and evolutionary significance of changes in nectar-spur length was examined in detail by Darwin (1862) and has been investigated extensively in subsequent years (e.g., Nilsson 1998;Maad 2000;Whittall and Hodges 2007;Sletvold andÅgren 2010, Boberg et al. 2014). Changes in spur length may reflect plant-pollinator coevolution (Darwin 1862;Wallace 1867), adaptive responses to shifts in pollinator species mediating se lection (Whittall and Hodges 2007), or a combination of the two (Boberg et al. 2014). ...
... The ecological and evolutionary significance of changes in nectar-spur length was examined in detail by Darwin (1862) and has been investigated extensively in subsequent years (e.g., Nilsson 1998;Maad 2000;Whittall and Hodges 2007;Sletvold andÅgren 2010, Boberg et al. 2014). Changes in spur length may reflect plant-pollinator coevolution (Darwin 1862;Wallace 1867), adaptive responses to shifts in pollinator species mediating se lection (Whittall and Hodges 2007), or a combination of the two (Boberg et al. 2014). The development of spurs and increases in their lengths reflect localized cell proliferation and/or cell elongation over developmental time (see Wessinger and Hileman 2020, fig. ...
... That flowers can change their orientation "behaviorally" (i.e., exhibit rapid phenotypic plasticity in response to an external or internal stimuli) has been known at least since Darwin's descriptions of the phenomenon (e.g., petal closure in response to cold or nightfall; Darwin, 1862Darwin, , 1880. Prob ably the best-known floral be hav ior is floral heliotropism: movement in response to the sun's position (see review in van der Kooi et al. 2019). ...
Essays on evolvability from the perspectives of quantitative and population genetics, evolutionary developmental biology, systems biology, macroevolution, and the philosophy of science.
Evolvability—the capability of organisms to evolve—wasn't recognized as a fundamental concept in evolutionary theory until 1990. Though there is still some debate as to whether it represents a truly new concept, the essays in this volume emphasize its value in enabling new research programs and facilitating communication among the major disciplines in evolutionary biology. The contributors, many of whom were instrumental in the development of the concept of evolvability, synthesize what we have learned about it over the past thirty years. They focus on the historical and philosophical contexts that influenced the emergence of the concept and suggest ways to develop a common language and theory to drive further evolvability research.
The essays, drawn from a workshop on evolvability hosted in 2019–2020 by the Center of Advanced Study at the Norwegian Academy of Science and Letters, in Oslo, provide scientific and historical background on evolvability. The contributors represent different disciplines of evolutionary biology, including quantitative and population genetics, evolutionary developmental biology, systems biology, and macroevolution, as well as the philosophy of science. This plurality of approaches allows researchers in disciplines as diverse as developmental biology, molecular biology, and systems biology to communicate with those working in mainstream evolutionary biology. The contributors also discuss key questions at the forefront of research on evolvability.
Contributors:J. David Aponte, W. Scott Armbruster, Geir H. Bolstad, Salomé Bourg, Ingo Brigandt, Anne Calof, James M. Cheverud, Josselin Clo, Frietson Galis, Mark Grabowski, Rebecca Green, Benedikt Hallgrímsson, Thomas F. Hansen, Agnes Holstad, David Houle, David Jablonski, Arthur Lander, Arnaud LeRouzic, Alan C. Love, Ralph Marcucio, Michael B. Morrissey, Laura Nuño de la Rosa, Øystein H. Opedal, Mihaela Pavličev, Christophe Pélabon, Jane M. Reid, Heather Richbourg, Jacqueline L. Sztepanacz, Masahito Tsuboi, Cristina Villegas, Marta Vidal-García, Kjetil L. Voje, Andreas Wagner, Günter P. Wagner, Nathan M. Young
... The diversity of flowers and inflorescences within the Orchidaceae family demonstrates the extreme evolutionary variability of its reproductive structures [19,20]. The impressive morphological diversity of tropical orchid flowers has been well known since the time of the great geographical discoveries, and their pollination mechanisms were even studied by Charles Darwin [21]. Despite this, the morphology of orchid inflorescences has ...
... The diversity of flowers and inflorescences within the Orchidaceae family demonstrates the extreme evolutionary variability of its reproductive structures [19,20]. The impressive morphological diversity of tropical orchid flowers has been well known since the time of the great geographical discoveries, and their pollination mechanisms were even studied by Charles Darwin [21]. Despite this, the morphology of orchid inflorescences has received less attention compared to flowers, despite their crucial role in pollinator attraction and increasing seed propagation [21]. ...
... The impressive morphological diversity of tropical orchid flowers has been well known since the time of the great geographical discoveries, and their pollination mechanisms were even studied by Charles Darwin [21]. Despite this, the morphology of orchid inflorescences has received less attention compared to flowers, despite their crucial role in pollinator attraction and increasing seed propagation [21]. The architecture, orientation, and lifespan of orchid inflorescences are determined not only by environmental and genetic factors, but also by selective pressure from pollinators [22]. ...
The morphostructure of inflorescences in the genus Coelogyne Lindl. was studied for the first time using a structural-rhythmological approach. Three species of Coelogyne were used to describe one-season, intercalary, and all-season inflorescences. In C. monilirachis, a new type of all-season inflorescence was identified, characterized by a prolonged sympodial growth of the rachis, lack of a pronounced dormant period, and thickening of all rachis internodes except the first. This inflorescence has been determined to be a compound monochasial cyme, with each floral unit represented by a separate flower. C. ovalis has a one-season inflorescence, with the floral unit being a determinate bracteous spike (stachyoid), and C. prolifera developed intercalary inflorescences united in an indeterminate bracteous spike.
... Pollinarium bending occurres in many orchid species, it will result in a time delay before the pollinium assumes a position from which it can strike a stigma (Darwin, 1877;Johnson Edwards, 2000). The phenomenon will decrease geitonogamy when pollinators visit fewer flowers and stay for shorter time per visit. ...
... The phenomenon will decrease geitonogamy when pollinators visit fewer flowers and stay for shorter time per visit. Some case studies confirm that pollinarium bending is an anti-selfing mechanism (Darwin, 1877;Johnson et al., 2004). These results suggest that pollinarium bending may increase orchid fitness under certain conditions. ...
... Besides, the proportions of full seeds and seed viability after nectar addition were significantly lower than that under natural conditions (Table 1; Figure 5). These results indicated that P. teres is similar to most deceptive orchids that avoid geitonogamy by the two mechanisms of deception and pollinarium bending (Darwin, 1877;Dafni Ivri, 1979;Johnson Edwards, 2000;Johnson et al., 2004), and deception contributes to pollinarium bending functioning in the aspect of anti-selfing. ...
Though some hypotheses have obtained theoretical and empirical supports, it remains largely unknown in the aspect that how deception increases orchid fitness. This study used food-deceptive Papilionanthe teres as experimental material to explore the ecological significance of orchid deceptive pollination. Deception together with obvious pollinarium bending increases P. teres fitness by means of decreasing geitonogamy under the natural conditions. The proportions of full seeds, single fruit weight and seed weight per fruit after self-pollination and nectar addition were significantly lower than that after cross-pollination and natural conditions (all p ＜ 0.05). Seed viability (seed growth and development rate) after cross-pollination and natural condition were significantly higher than that after self-pollination and nectar addition (all p ＜ 0.05). However, there was no significant difference in all the above parameter values of fruits and seeds between cross-pollination and natural conditions (all p ＞ 0.05). These results confirmed that P. teres has high level of genetic load, and self-fertilization or geitonogamy will cause serious inbreeding depression. These conclusions support the outcrossing hypothesis that ecological significance of P. teres deception is to promote outcrossing and improve the ability of the offspring to adapt to the environment.
... The genus Bonatea consists of 10 species and is phylogenetically nested within Habenaria (Ponsie et al. 2007, Ngugi et al. 2020. Contemporary studies indicate that both moth and butterfly pollination systems are represented in Bonatea ( Johnson and Liltved 1997, Balducci et al. 2019a, b, 2020, but the function of the complex floral morphology in this orchid group, which was highlighted by Darwin (1877), remains poorly understood. Trimen (1865) speculated that a tooth-like structure in the entrance to the flowers of Bonatea speciosa (Fig. 1E) would compel insects to make their 'approach to the nectary a little to one side or the other' . ...
... It is clear that flowers of B. antennifera are functionally subdivided into two pollination units (meranthia) by the wedge-shaped rostellum chamber and the tooth in the spur mouth. As originally suggested by Trimen (1865) and discussed by Darwin (1877), these traits force moths to probe from either side of the entrance to the spur. The result is that only one of the two pollinaria is removed in a single visit, whereas pollen is deposited on both stigma lobes in a single visit. ...
One explanation for the evolution of complex floral morphology in orchids is that it can function as a component of ‘lock-and-key’ mechanisms that ensure pollen transfer by specific flower visitors. We investigated the roles of floral morphology and scent in the pollination of Bonatea antennifera, an African orchid that is phylogenetically embedded in the hyper-diverse Habenaria clade. Using camera traps and direct observations, we established that B. antennifera is pollinated by an assemblage of short-tongued hawkmoths with proboscides ~4 cm in length, corresponding to the spur length of the orchid. Pollinaria are attached between the palps of these hawkmoths via an intricate mechanism involving a wedge-shaped rostellum chamber and a tooth in the floral spur that deflect the head and proboscis of the hawkmoth to either side of the spur entrance. This functional subdivision of the flower results in removal of a single pollinarium per visit. Scent production is synchronized with the peak activity of hawkmoths at dusk, and electrophysiology experiments showed that hawkmoth antennae respond to several of the dominant volatile terpenoid compounds [e.g. R-(−)-linalool, caryophyllene epoxide, and (E)-nerolidol] emitted by the flowers. These results illustrate the functional significance of complex floral morphology and scent for pollen transfer in orchids.
... Broadly speaking, we could divide the books written by Darwin into two types. Those in which he defends general frameworks of a more speculative or philosophical char-acter, on the one hand, and those and those in that, in a minute way, he studies a specific empirical problem in detail: Origin representing the former and the book on orchids, the latter (Darwin 1877a). What about Descent? ...
... Of course, this idea does not make sense in the Darwinian framework, a matter of which Darwin is fully aware (Darwin 1872a, pp.159-164). Darwin dedicated much of his writings to showing that the end pursued by flowers involves not beautifying creation but promoting cross-fertilization (Darwin 1876(Darwin , 1877a(Darwin , 1877b, and he dedicated a large part of Descent to showing that many other traits that seem merely ornamental arose by sexual selection. Interestingly, this does not imply that beauty has no explanatory role. ...
Desmond and Moore point out that the key to understanding Darwin’s The Descent of Man is his abolitionist motivation and his advocacy that races constitute subspecies. Roberta Millstein raises some doubts about the importance of this motivation. She points out that the inclusion of the extensive section devoted to non-human animals is not justified by Darwin’s treatment of humans per se, because his explanation of the origin of races is peculiar. In this sense, she argues that Darwin’s specific explanation of the origin of races does not confirm the central importance that Desmond and Moore give to Darwin’s abolitionism. In this paper I have two different aims. On the one hand, to show that the human case actually is based on the treatment of nonhuman animals, and consequently, Darwin’s argument is not as poor as Millstein believes. My second goal, taking Millstein’s challenge seriously, is to show that Darwin’s explanation of the origin of races does confirm the Desmond and Moore thesis in a deeper sense than the one they propose themselves. For the anti-slavery motivation could not only explain the fact that Darwin sees all humans as forming the same species, but the specific explanation he gives for the origin of races.
... More than half of all known insects on Earth-over 500,000 species-are fluid feeders (1). Among them, nectar feeders have attracted the attention of scientists since Darwin predicted, well before its discovery, the existence of a specific orchid corresponding to the extraordinarily long proboscis of sphinx moth (2,3). How nectar-feeding insects use their elaborate mouthparts to interact with the great variety of flower structures remains an important question in evolutionary biology, ecology, and biomechanics (4-7). ...
... When the liquid distance x (Fig. 2D) increases beyond a critical value x * = L , the flow rate in the free surface region becomes smaller than Q 1 and thus will thus determine the global flow rate (SI Appendix, Fig. S1), which writes [2] Hence, the effective sucking flow rate of the whole process can be expressed as Q suck = min Q 1 , Q 2 (x) . In order to apply Eqs. 1 and 2 to describe suction by honey bees, we need to know the pressure difference, ΔP , generated by the head pump. ...
The feeding mechanisms of animals constrain the spectrum of resources that they can exploit profitably. For floral nectar eaters, both corolla depth and nectar properties have marked influence on foraging choices. We report the multiple strategies used by honey bees to efficiently extract nectar at the range of sugar concentrations and corolla depths they face in nature. Honey bees can collect nectar by dipping their hairy tongues or capillary loading when lapping it, or they can attach the tongue to the wall of long corollas and directly suck the nectar along the tongue sides. The honey bee feeding apparatus is unveiled as a multifunctional tool that can switch between lapping and sucking nectar according to the instantaneous ingesting efficiency, which is determined by the interplay of nectar-mouth distance and sugar concentration. These versatile feeding mechanisms allow honey bees to extract nectar efficiently from a wider range of floral resources than previously appreciated and endow them with remarkable adaptability to diverse foraging environments.
... We also recorded pollinia fragmentation (loss of pollen units) on insect bodies as fragmentation may indicate earlier contact with receptive stigmas (Tao et al. 2018b). This also required recording stipe position on insect bodies as sterile connectives (caudicles and stipes) change in position as they dry in the open air (see Darwin 1862Darwin , 1877. Some pollinaria-bearing specimens were observed and photographed at the Australian Museum, Sydney, using a Leica M205A stereomicroscope with a Leica DFC500 digital camera (Leica microsystems, Switzerland). ...
... Dorsal thorax deposition of pollinaria is described in other non-resupinate orchids including Catasetum (Romero and Nelson 1986) Calopogon (Argue 2012) and Prasophyllum (Bernhardt & Burns-Balogh 1986b;Kuiter 2016Kuiter , 2018. Darwin (1862Darwin ( , 1877 was the first to show that caudicles and stipes of various orchid species bend slowly as they dry following removal by pollinators. This delayed development is usually interpreted as a trait that lowers the frequency of pollinator-mediated self-pollinations. ...
Corunastylis species produce some of the smallest, fly-pollinated flowers of Australian orchids to offer liquid rewards. We observed and collected pollinarium vectors of four Corunastylis species (C. filiformis, C. fimbriata, C. rufa and C. ruppii) with overlapping flowering periods during the summer-autumn months at five sites in New South Wales (NSW), Australia. The most common pollinarium vectors of all species were females of a single morphotype in the genus Conioscinella (Dip-tera: Chloropidae). This morphotype was less than 3 mm in length and carried dorsal depositions of pollinaria on its thorax. A chloropid could carry as many as two pollinaria and 25-50% of attached pollinia showed erosion, suggesting previous contact with receptive stigmas. Bagging experiments on three species showed low rates of mechanical self-pollination and no fruit set in C. filiformis, C. fimbriata and C. ruppii. The conversion rate of insect-pollinated flowers into fruit varied from 35 to 91% among these three species in NSW versus C. ciliata in Victoria. Seed development also varied with > 42-70% of seeds in the three species in NSW containing fully developed embryos. High levels of reproductive success in these three species in NSW and C. ciliata in Victoria were the same as for fruit sets in other orchid species in other genera with nectar-secreting flowers. As flowering periods, distributions and primary pollinators of four Corunastylis species in NSW overlapped so broadly there appears to be a lack of pre-zygotic interspecific isolation mechanisms. This study provided important pollination and reproductive information towards future conservation management of these orchid species.
... It is fascinating to note the wide range of floral traits that animalpollinated flowering plants exhibit, which has been a source of interest for many evolutionary biologists, including Darwin (1862). The natural environment is rarely homogeneous and predictable, and flowering plants, more than most organisms, exhibit extreme variations in colour, shape, size, life span, distribution, reproductive structures and sexual strategies (Willmer 2011;Torezan-Silingardi, Silberbauer-Gottsberger, and Gottsberger 2021). ...
The intricate web of interactions in nature has led to unexpected partnerships between plants and animals, greatly influencing ecosystem dynamics. In this discussion, we'll explore the Pollination Syndrome Hypothesis and consider a scenario where a partnership with unexpected pollinators emerges. We suggest that ant pollination has been largely overlooked, but ants can surprisingly play a crucial role and have a history of success in pollinating dry system plants. We will present both negative and positive aspects that must be observed in ant-pollination syndrome. Additionally, we aim to explore the often-underestimated phenomenon of ant pollination and the overlooked tiny, discreet, unnoticed flowers found in our fields and forests, especially in dry ecosystems, savannas and mountain fields, which may hold numerous undiscovered secrets about these interactions. We encourage young biologists to engage in natural history observations and to perform manipulative experiments directly in the field to understand the true nature of these successful ant-pollinations.
... This subject aroused the particular interest of Charles Darwin, among other authors, who found in the pollination systems of orchids one of his most remarkable demonstrations of the theory of biological evolution (Fay & Chase, 2009). For this reason, one of the main groups studied by Charles Darwin was the genus Ophrys L. (Darwin, 1877), the most diverse of the European orchidoflora (see Baumann & Künkele, 1982;Buttler, 1991;Devillers & Devillers-Terschuren, 1994;Devey et al., 2008;Delforge, 2016). Delforge (2016), one of the most analytical specialists, indicates the presence of 354 species for the European continent, the Mediterranean and North Africa. ...
... The interest in plant-hawkmoth interactions as a model system to understand coevolution has been 47 notorious since the 1800s (Darwin, 1862). However, only recently the advances in concepts and analytical tools 48 derived from complex networks approaches (Vázquez et al., 2009a) have allowed to understand more deeply 49 ...
... In a broader context, dual seed dispersal systems by passerine birds and carnivores represent a novel addition to the seed dispersal mechanisms in the family Orchidaceae. Although biologists have long been captivated by the remarkable diversity of pollination biology in orchids (Darwin 1862;Nilsson 1992), the mechanisms of orchid seed dispersal have not been as thoroughly studied. However, these dispersal mechanisms might also be fundamental to understanding ecological success and morphological diversity. ...
Cyrtosia septentrionalis , an orchid species, is notable for its sausage‐shaped red fleshy fruits, which can reach up to 10 cm in length. Previous research identified frugivorous and omnivorous birds, especially the brown‐eared bulbul Hypsipetes amaurotis (Pycnonotidae, Passeriformes), as key seed dispersers of C. septentrionalis in natural habitats. This finding challenges conventional belief that orchid seeds are primarily wind‐dispersed. Moreover, given the rarity of specialized co‐evolutionary relationships between fruits and frugivores, C. septentrionalis may also rely on mammals for seed dispersal in certain regions.
We aimed to explore the fruit consumption habits of animals other than birds. Motion sensor‐equipped cameras were used to observe interactions with the fruits of C. septentrionalis and assess the viability of seeds post‐consumption.
The observations revealed three animal species consuming the fruits, with the masked palm civet Paguma larvata (Viverridae, Carnivora) identified as a dominant consumer in the investigated population. Microscopy analysis of seeds retrieved from P. larvata faeces indicated that the seeds remained intact and viable after passing through the digestive system of this carnivorous mammal.
The above discovery suggests a potential role for carnivorous mammals in seed dispersal of C. septentrionalis , alongside birds, thus broadening our understanding of the complex seed dispersal strategies employed by orchids.
... Trades-offs between pollinator attraction and florivore defense maximize reproductive success in the self-incompatible Rivea ornata (Convolvulaceae) Background Floral specialization reflects evolutionary diversification that is driven by selective pressures associated with reproduction, such as specific plant-pollinator interactions [1][2][3][4]. Concepts to classify floral traits (e.g., morphology, chemistry, phenology) that are linked to specific functional groups of pollinators are known as pollination syndromes [5][6][7][8][9][10][11]. These pollination syndromes allow researchers to test hypotheses about the predicted pollinators of specific plant species. ...
Background
Rivea ornata, a rare species from the morning glory family, exhibits uncommon characteristics compared to other typical morning glories, including nocturnal flowers that fit the classic moth pollination syndrome. However, the accuracy of its predicted pollination syndrome and its mating system have never been assessed. Additionally, R. ornata flowers attract not only pollinators but also florivores, potentially reducing plant reproductive success. Therefore, this study examined two populations of R. ornata in Thailand and assessed traits related to pollinator attraction and reward, determined its mating system, identified floral visitors and effective pollinators, and investigated the effect of florivory on reproductive success.
Results
Rivea ornata is highly fertile but self-incompatible and an obligate outcrosser, rendering it highly dependent on pollinators. Lepidopterans, particularly nocturnal hawk moths, were found to account for a significant proportion of all visits and were the sole effective pollinators of this plant species, in correspondence with its predicted pollination syndrome. Surprisingly, florivory did not significantly reduce reproductive success. This phenomenon may be explained by the strategies employed by R. ornata, which align with the optimal defense hypothesis and functional trade-offs. Specifically, R. ornata appears to invest resources in defending key floral structures while, simultaneously, guard ants are conspicuously absent from flowers, resulting in some florivore damage to non-vital floral organs but ensuring that pollinators are not deterred by ants and thus maintaining high pollinator visitation rates.
Conclusions
Our findings indicate that reproduction-related traits in R. ornata, including those involved in pollinator attraction and reward and florivore defense, are highly effective and work in concert to maximize plant reproductive success. Therefore, a main risk that R. ornata faces is the decline or disappearance of hawk moths and other lepidopterans given its extreme specialization and high dependence on pollinators, and conservation efforts should include habitat protection for both R. ornata and its pollinators.
Supplementary Information
The online version contains supplementary material available at 10.1186/s12862-024-02301-7.
... Mutualism represents one of the primary mechanisms for determining the life histories of animals and plants [13]. When we read that Charles Darwin first noticed mutualism while traveling, he said, 'If such great moths were to become extinct in Madagascar, undoubtedly the Angraecum would become extinct' to demonstrate how some species would have perished if they had not found mutualistic mates [14]. A study on explosive predators and mutualistic prey has been investigated by Batabyal et al. [15]. ...
For this study, a three-species food chain model that considers interactions between small fish, remora fish, and large fish has been developed. It is assumed that large fish consume small fish through the functional response of Holling type II. Remora fish are considered to benefit from eating the remaining parts of small fish hunted by larger fish. Remora fish may benefit from eating the parasites found in the bodies of large fish. The non-negativity and boundedness of the solution of the model are investigated. In addition, each potential stable state for the model has been determined. We also investigated the local stability of the model, which is close to the steady state. The Lyapunov function and geometric technique are used to investigate the global stability of the model. It has been found that the increase in the refuge rate for small fish contributes to the instability of the model. It has been observed that the model may show unstable behaviour due to an increase in the rate of consumption of small fish by big fish. It has been found that the density of remora fish may rise because of their mutualistic relationship with large fishes.
... Pollination has been the subject of study for over 200 years (Darwin, 1877;Mayr, 1986;Vogel, 1996;Waser & Ollerton, 2006). ...
The patterns and drivers of pollen transport on insect bodies can have important consequences for plant reproductive success and floral evolution; however, they remain little studied. Recently, pollinator bodies have been further described as pollen competitive arenas, where pollen grains can compete for space, with implications for the evolution of pollen dispersal strategies and plant community assembly. However, the identity, strength, and diversity of pollen competitive interactions and how they vary across pollinator functional groups is not known. Evaluating patterns and drivers of the pollen co‐transport landscape and how these vary across different pollinator groups is central to further our understanding of floral evolution and co‐flowering community assembly.
Here, we integrate information on the number and identity of pollen grains on individual insect pollen loads with network analyses to uncover novel pollen co‐transport networks and how these vary across pollinator functional groups (bees and bee flies). We further evaluate differences in pollen load size, species composition, diversity and phylogenetic diversity among insect groups and how these relate to body size and gender.
Pollen co‐transport networks were diverse and highly modular in bees, with groups of pollen species interacting more often with each other on insect bodies. However, the number, identity and frequency of competitors that pollen grains encounter on insect bodies vary between some pollinator functional groups. Other aspects of pollen loads such as their size, richness and phylogenetical diversity were shaped by bee size or gender, with females carrying larger but less phylogenetically diverse pollen loads than males.
Synthesis. Our results show that the number, identity and phylogenetic relatedness of pollen competitors changes as pollen grains travel on the body of different pollinators. As a result, pollinator groups impose vastly different interaction landscapes during pollen transport, with so far unknown consequences for plant reproductive success, floral evolution and community assembly.
... E.g., in his preface to a new edition of Darwin's work on orchids Michael Ghiselin argues that Darwin's (1959) theory succeeded in "getting rid of teleology and replacing it with a new way of thinking about adaptation." (Darwin, 1862(Darwin, /1877(Darwin, [1984, p. 409). Similarly, theories of selected effects, extensively developed by Neander, Millikan, Griffith, Godfrey-Smith, and others, assume that the apparent end-directedness of biological functions is not an intrinsic feature of organisms, but rather an observer's projection of whatever properties past replicas of that trait contributed to its current presence in the population. ...
To naturalize the concept of teleological causality in biology it is not enough to avoid assuming backward causation or positing the existence of an inscrutable teleological essence like the élan vital. We must also specify how the causality of organisms is distinct from the causality of designed artifacts like thermostats or asymmetrically oriented processes like the ubiquitous increase of entropy. Historically, the concept of teleological causality in biology has been based on an analogy to the familiar experience of purposeful action. This is experienced by us as a disposition to achieve a general type of end that is represented in advance, and which regulates the selection of efficient means to achieve it. Inspired by this analogy, to bridge the gap between biology and human agency we describe a simple molecular process called autogenesis that shows how two linked complementary self-organizing processes can give rise to higher-order relations that resemble purposeful dispositions, though expressed in terms of constraints on molecular processes. Because the autogenic model is described in sufficient detail to be empirically realizable, it provides a proof of principle demonstrating a simple form of teleological causality.
... We also observed a pollination foraging behavior from the bottom of the inflorescence toward the apex, in a spiral path, in both bumblebee species and hummingbirds. This behavior was already described in European and North American Spiranthes (Spiranthinae) pollinated by bumblebees (Catling, 1983;Darwin, 1862) and is influenced by inflorescence architecture and flower features (Iwata et al., 2012). These Spiranthes species are normally protandrous, that is, justopened flowers can only act as pollen donors and, a few days later, as pollen receivers. ...
... The interest on plant-hawkmoth interactions as a model system to understand coevolution has been 45 notorious since the 1800s (Darwin, 1862). However, only recently the advances in concepts and analytical 46 tools derived from complex networks approaches (Vázquez et al., 2009a) have allowed to understand more 47 ...
... All Spiranthes other than S. lucida (H.H. Eaton) Ames are protandrous, however the observed differences in column foot morphology and length between S. stylites and other members of the S. sinensis species complex are not related to the maturation of the flower from functionally male to functionally bisexual. Protandry in Spiranthes is related to the expansion of the abaxial column foot cells, causing the column to flex upwards, exposing the stigmatic surface, rather than elongation of the column (Gray 1862;Darwin 1904;Colman 1933;Catling 1983). ...
We reexamine the taxon Spiranthes stylites , currently synonymized under S . australis , finding multiple lines of evidence from molecular phylogenetics, phenology, morphology, and habitat differences to support its distinction from other members of the Spiranthes sinensis species complex. Compared to its closest relative S . australis , S . stylites blooms earlier (June ‐ early July vs. mid July ‐ September), has consistently white tubular flowers (vs. commonly pink and pseudocampanulate), a distinctly long-clawed labellum (vs. shortly clawed), slender labellum nectar callosities (vs. globose), a proportionally larger column foot (ca. 50% of the length of the entire column vs. ca. 25%), and occurs in closed canopy woodlands (vs. open graminoid habitats). Spiranthes stylites is the only Spiranthes in the Eastern Hemisphere to have a woodland habitat. The recognition of S . stylites helps support white colored flowers as the plesiomorphic and most common floral condition in the complex, and indicates pink colored flowers likely arose independently in S . australis and S . sinensis s.s.
... Pollinators commonly drive floral diversity through floral specialization, providing an effective barrier to gene flow and/or acting as an agent of hybridization (Darwin 1862;Stebbins 1970;Rezende et al. 2020;Turchetto et al. 2022). Both processes, floral specialization and hybridization, contributed to angiosperm diversification (van der Niet and Johnson 2012; Chase et al. 2010), making clear the dual role of pollinators as a primary driver of plant diversity involving microevolution and macroevolution processes. ...
Plant-pollinator relationships drive floral diversity. Among many floral signals, floral scent attracts and ensures efficient pollination, like benzyl acetone and its derivatives are important for hawkmoth species to detect flowers. Nicotiana is a diverse genus in terms of floral phenotypes. Its evolution was driven by the close relationship with pollinators through floral specialization and hybridization, causing the emergence of new species. Nicotiana has a wide variety of floral shapes and colors. Hybridization is prevalent in the group, resulting in transgressive phenotypes impacting pollination-related visual traits. This study investigated the diversity of floral Volatile Organic Compounds (VOCs) of Nicotiana species and discussed the data according to pollinator functional groups and the known phylogenetic relationships of the species. A bibliographic review was carried out, including 30 years of floral volatile emissions studies. The results of 18 studies investigating floral volatiles in 19 species of Nicotiana were revised and organized by temporal emissions, day and night emissions. We retrieved information concerning methodology, volatile compounds, day/night emissions, and pollinator functional groups for each study and species. In total, 179 compounds were found, including mono- and sesquiterpenoids, nitrogenous compounds, and benzenoids. Most allopolyploid species lack floral emissions data, and total temporal emissions in Nicotiana are still underrepresented. The results suggest that night-pollinated species of Nicotiana have high emission blends’ similarity to each other, compound-wise and class-wise. However, phylogeny still plays an important role in scent emission for species with different pollinators functional groups, considering the known phylogenetic relationship in the genus. Species known to be closely related by current phylogeny, like N. forgetiana and N. alata, share similar blends even though their pollinator functional groups are entirely different and opposite, suggesting a phylogenetic relationship in this phenotype and/or other processes, such as hybridization.
... The interest on plant-hawkmoth interactions as a model system to understand coevolution is notorious 45 since the 1800s (Darwin, 1862). However, only recently advances in concepts and analytical tools derived 46 from complex networks approaches (Vázquez et al., 2009a) have allowed to understand more deeply what 47 Charles Darwin defined as a "tangled bank of organisms that interact with each other according to laws that 48 determine their associations" (Darwin, 1859). ...
... The interest on plant-hawkmoth interactions as a model system to understand coevolution is notorious 45 since the 1800s (Darwin, 1862). However, only recently advances in concepts and analytical tools derived 46 from complex networks approaches (Vázquez et al., 2009a) have allowed to understand more deeply what 47 Charles Darwin defined as a "tangled bank of organisms that interact with each other according to laws that 48 determine their associations" (Darwin, 1859). ...
Multiple non-exclusive neutral or niche-based processes influence species interactions and shape the structure of ecological networks. Although evolutionary processes may influence interactions via shared inherited traits, their relative importance in comparison to ecological processes remain poorly understood. Here we investigate the effects of evolutionary history compared to ecological processes on both interaction frequencies and the emergence of modularity in a plant-hawkmoth interaction network. Finally, we tested the phylogenetic signals on hawkmoth ecological traits relevant to pollination interactions. We analyzed a plant-hawkmoth network on Pampa grasslands for which we collected morphological, phenological, abundance and phylogenetic data for every species in the network to evaluate neutral-based processes (i.e., random chance of encounter dictated by species abundances) or niche-based processes (i.e., morphological matching). The best model predicting interactions indicated that, beyond increasing interaction frequencies with increased morphological matching and phenological overlap, distantly related hawkmoth species also tended to interact with plants more frequently. Further, by evaluating whether hawkmoth composition differed among interaction modules, we found that modules encompassed phylogenetically distant and functionally distinct hawkmoth species. Thus, module composition suggests that, despite evolutionary history and ecological traits influencing interactions’ frequency, modules emergence may be also potentially modulated by processes such as environmental filtering or stochastic factors acting on other traits than the ones evaluated here. Such processes may have influenced hawkmoths’ species composition in the community and ultimately also shape the observed interaction patterns.
... We also observed a pollination foraging behavior from the bottom of the inflorescence toward the apex, in a spiral path, in both bumblebee species and hummingbirds. This behavior was already described in European and North American Spiranthes (Spiranthinae) pollinated by bumblebees (Catling, 1983;Darwin, 1862) and is influenced by inflorescence architecture and flower features (Iwata et al., 2012). These Spiranthes species are normally protandrous, that is, justopened flowers can only act as pollen donors and, a few days later, as pollen receivers. ...
Floral features, the pollination process, the breeding system, and fruiting success are documented in the Andean terrestrial orchid Gomphichis valida. Studies were performed at the Department of Ancash, Peru, at ca. 4250 m a.s.l., from June to November 2022. The breeding system was studied through controlled pollina-tions in plants excluded from pollinators (bagged). Natural pollination was studied in the field and through photos and videos. The flowers are nectariferous and non-protandrous and present the longest lifespan reported so far for a neotropical terrestrial orchid (53-80 days). This species is pollinator dependent (unable to set fruit and seed without the agency of pollinators) and self-compatible. The observed pollinators belong to three functional groups that appeared successively (in order of appearance): hummingbirds (Chalcostigma stanleyi), bumblebees (Bombus coccineus and Bombus rubicundus), and solitary Halictidae bees (Augo-chlorella sp.). All recorded pollinators probe the flowers for nectar. The pollinaria adhere to the bee mouthparts and onto the lateral side of the hummingbird bill. Bumblebees were the most frequent and efficient functional group (up to 62.07% of the observed pollination events), followed by Halictidae (31.03%) and hum-mingbirds (6.90%). Natural fruiting success is high (66.66%-94.49%). Such high natural fruiting success is unexpected at high altitudes, but it is likely explained by a combination of factors, including the long floral lifespan, nectar secretion, and self-compatibility. This is the first report of hummingbirds as pollinators of Cranichidinae orchids, and G. valida is, to the best of our knowledge, a neotropi-cal orchidoid orchid with the most generalist pollination biology recorded so far. K E Y W O R D S bumblebees, hummingbirds, Peru, Polylepis woodlands, solitary bees
... The repeated nature of floral evolution is evident from the scattered phylogenetic distribution of many floral traits 1-6 , of pollination modes and syndromes 3,7-10 as well as of sexual, breeding and mating systems 11-18 . A major paradigm, supported by evidence at micro-and meso-evolutionary time scales, is that such convergences have evolved in response to selection for increased pollination and reproductive efficiency in different lineages with a common selection regime [19][20][21][22] . According to the pollination-precision hypothesis, reproductive efficiency is increased by floral traits improving the fit of pollinators to flowers and their reliable contact with sex organs, thus improving pollen deposition on precise areas of pollinators' bodies [23][24][25] . ...
Since the insights by Charles Darwin, heterostyly, a floral polymorphism with morphs bearing stigmas and anthers at reciprocal heights, has become a model system for the study of natural selection. Based on his archetypal heterostylous flower, including regular symmetry, few stamens and a tube, Darwin hypothesised that heterostyly evolved to promote outcrossing through efficient pollen transfer between morphs involving different areas of a pollinator’s body, thus proposing his seminal pollination-precision hypothesis. Here we update the number of heterostylous and other style-length polymorphic taxa to 247 genera belonging to 34 families, notably expanding known cases by 20%. Using phylogenetic and comparative analyses across the angiosperms, we show numerous independent origins of style-length polymorphism associated with actinomorphic, tubular flowers with a low number of sex organs, stamens fused to the corolla, and pollination by long-tongued insects. These associations provide support for the Darwinian pollination-precision hypothesis as a basis for convergent evolution of heterostyly across angiosperms.
... Likewise, the entrance hole size in domatia provided by epiphytic Rubiaceae to symbiotic ants -which screens which symbiont can access specific domatia -is highly constrained in specialised plant species . Second, another model, dating back to Darwin (1862), posits that selection may favour reciprocal increase in mutualistic trait values in interacting species. However, as Darwin was careful to point out, any seemingly matching traits might have arisen for reasons unrelated to the interaction. ...
Mutualisms have driven the evolution of extraordinary structures and behavioural traits, but their impact on traits beyond those directly involved in the interaction remains unclear. We addressed this gap using a highly evolutionarily replicated system – epiphytes in the Rubiaceae forming symbioses with ants. We employed models that allow us to test the influence of discrete mutualistic traits on continuous non‐mutualistic traits. Our findings are consistent with mutualism shaping the pace of morphological evolution, strength of selection and long‐term mean of non‐mutualistic traits in function of mutualistic dependency. While specialised and obligate mutualisms are associated with slower trait change, less intimate, facultative and generalist mutualistic interactions – which are the most common – have a greater impact on non‐mutualistic trait evolution. These results challenge the prevailing notion that mutualisms solely affect the evolution of interaction‐related traits via stabilizing selection and instead demonstrate a broader role for mutualisms in shaping trait evolution.
... He recognized that the two most significant events in the history of floral biology were the realization that many features of flowers facilitate cross-fertilization (Sprengel 1793), and that the progeny from crossfertilization generally perform better than those from self-fertilization (Knight 1799). As Darwin had shown from extensive studies of floral mechanisms that promote outcrossing (Darwin 1862(Darwin , 1877 and experiments on inbreeding depression (Darwin 1876), these two concepts could explain the function of flowers. As indicated by the quotation preceding this paragraph, Lloyd embraced the developing perspective (e.g., Willson 1979Willson , 1994) that traits controlling mating in angiosperms are subject to sexual selection, even though most species are hermaphroditic. ...
The reproductive organs and mating biology of angiosperms exhibit greater variety than those of any other group of organisms. Flowers and inflorescences are also the most diverse structures produced by angiosperms, and floral traits provide some of the most compelling examples of evolution by natural selection. Given that flowering plants include roughly 250,000 species, their reproductive diversity will not be explained easily by continued accumulation of case studies of individual species. ınstead a more strategic approach is now required, which seeks to identify general principles concerning the role of ecological function in the evolution of reproductive diversity. The Ecology and Evolution of Flowers uses this approach to expose new insights into the functional basis of floral diversity, and presents the very latest theoretical and empirical research on floral evolution. Floral biology is a dynamic and growing area and this book, written by the leading internationally recognized researchers in this field, reviews current progress in understanding the evolution and function of flowers. Chapters contain both new research findings and synthesis. Major sections in turn examine functional aspects of floral traits and sexual systems, the ecological influences on reproductive adaptation, and the role of floral biology in angiosperm diversification. Overall, this integrated treatment illustrates the role of floral function and evolution in the generation of angiosperm biodiversity. This advanced textbook is suitable for graduate level students taking courses in plant ecology, evolution, systematics, biodiversity and conservation. ıt will also be of interest and use to a broader audience of plant scientists seeking an authoritative overview of recent advances in floral biology.
... The contrast of this general removal disadvantage with the transport benefits suggests that pollinia evolved in angiosperms under sexual selection for enhanced pollen transport rather than enhanced pollen removal [14]. Darwin [98] and Dressler [46] argued that the evolution of numerous ovules in orchids associated with their small seeds precipitated the evolution of pollinia because this packaging allows numerous pollen grains to be delivered simultaneously to stigmas for ovule fertilization. However, this hypothesis cannot apply in the case of pollinium evolution in milkweeds, as they produce relatively large seeds. ...
Mating success of flowering plants depends strongly on the efficiencies of pollen removal from flowers and its subsequent dispersal to conspecific stigmas. We characterized the economy of pollen dispersal in flowering plants by analysing pollen fates and their correlates for 228 species. The mean percentage of pollen removed from flowers (removal efficiency) varied almost twofold according to the type of pollen-dispersal unit, from less than 45% for orchids and milkweeds with solid pollinia, to greater than 80% for species with granular monads or sectile (segmented) pollinia. The mean percentage of removed pollen reaching stigmas (pollen transfer efficiency, PTE) varied from 2.4% for species with separate monads to 27.0% for orchids with solid pollinia. These values tended to be higher in plants with single pollinator species and in those with non-grooming pollinators. Nectar production increased removal efficiency, but did not influence PTE. Among types of pollen-dispersal units, the net percentage of produced pollen that was dispersed to stigmas varied negatively with removal efficiency and positively with PTE, indicating the relative importance of the latter for overall pollen economy. These findings confirm the key importance of floral traits, particularly pollen packaging, for pollen dispersal outcomes and highlight the under-appreciated pollination efficiency of non-grooming pollinators.
... Ever since Charles Darwin predicted that an orchid with an extraordinarily long nectar spur might be pollinated by a moth with an equally long proboscis (Arditti et al., 2012;Darwin, 1877), and Alfred Russel Wallace (Arditti et al., 2012;Wallace, 1867) subsequently suggested that hawkmoths (Lepidoptera, Sphingidae) were likely candidates, hawkmoths have been popular models for understanding ecomorphological consequences in biology (Krenn and Kristensen, 2000;Kristensen, 1984;Kristensen et al., 2014) and bio-inspired engineering applications (Dudley, 2002;Stöckl and Kelber, 2019;Zhang et al., 2019). The family Sphingidae comprises more than 1460 species (Goldstein, 2017;Lees and Zilli, 2019). ...
Hovering hawkmoths expend significant energy while feeding, which should select for greater feeding efficiency. Although increased feeding efficiency has been implicitly assumed, it has never been assessed. We hypothesized that hawkmoths have proboscises specialized for gathering nectar passively. Using contact angle and capillary pressure to evaluate capillary action of the proboscis, we conducted a comparative analysis of wetting and absorption properties for 13 species of hawkmoths. We showed that all 13 species have a hydrophilic proboscis. In contradistinction, the proboscises of all other tested lepidopteran species have a wetting dichotomy with only the distal ∼10% hydrophilic. Longer proboscises are more wettable, suggesting that species of hawkmoths with long proboscises are more efficient at acquiring nectar by the proboscis surface than are species with shorter proboscises. All hawkmoth species also show strong capillary pressures which, together with the feeding behaviors we observed, ensure that nectar will be delivered to the food canal efficiently. The patterns we found suggest that different subfamilies of hawkmoths use different feeding strategies. Our comparative approach reveals that hawkmoths are unique among Lepidoptera and highlights the importance of considering the physical characteristics of the proboscis to understand the evolution and diversification of hawkmoths.
... The interest on plant-hawkmoth interactions as a model system to understand coevolution is notorious 42 since the 1800s (Darwin, 1862). However, only recently advances in concepts and analytical tools derived 43 from complex networks approaches (Vázquez et al., 2009a) have allowed to understand more deeply what 44 Charles Darwin defined as a "tangled bank of organisms that interact with each other according to laws that 45 determine their associations" (Darwin, 1859). ...
... and not via directional selection exerted by specialized pollinators (Darwin, 1862), such as those with extreme trait adaptations. In addition, the local bee adaptation hypothesis stated that if there is a low bee visitation rate in the highest site, we should see an exaggeration of bee attraction traits there. ...
Different populations of plant species can adapt to their local pollinators and diverge in floral traits accordingly. Floral traits are subject to pollinator-driven natural selection to enhance plant reproductive success. Studies on temperate plant systems have shown pollinator-driven selection results in floral trait variation along elevational gradients, but studies in tropical systems are lacking. We analyzed floral traits and pollinator assemblages in the Neotropical bee-pollinated taxon Costus guanaiensis var. tarmicus across four sites along a steep elevational gradient in Peru. We found variations in floral traits of size, color, and reward, and in the pollinator assemblage along the elevational gradient. We examined our results considering two hypotheses, (1) local adaptation to different bee assemblages, and (2) the early stages of an evolutionary shift to a new pollinator functional group (hummingbirds). We found some evidence consistent with the adaptation of C. guanaiensis var. tarmicus to the local bee fauna along the studied elevational gradient. Corolla width across sites was associated with bee thorax width of the local most frequent pollinator. However, we could not rule out the possibility of the beginning of a bee-to-hummingbird pollination shift in the highest-studied site. Our study is one of the few geographic-scale analyses of floral trait and pollinator assemblage variation in tropical plant species. Our results broaden our understanding of plant-pollinator interactions beyond temperate systems by showing substantial intraspecific divergence in both floral traits and pollinator assemblages across geographic space in a tropical plant species.
... The work of Sprengel was "rediscovered" by Darwin, who was particularly interested in orchid pollination as a model system for his ideas of natural selection (see also the papers this symposium). Darwin rejected the idea that many orchids are deceptive and argued strongly in the second edition of his book that the bees release a "nectar" reward from the tissue of the spurs of the flowers (Darwin, 1877). ...
Despite being one of the two largest families of flowering plants and the fact that pollinators are undoubtedly responsible for generating much of the diversity in this family, details of pollination biology have been documented for less than five percent of species in the Orchidaceae. Published work on orchid pollination was surveyed to determine the importance of different groups of animals effecting pollination; the number of species pollinating each species to determine degrees of specialisation; and the presence or absence of a reward in each species. This analysis shows that approximately 40% of orchid species are bee-pollinated. Surprisingly, the second most frequent category is autonomous self-pollination occurring in 31% of species although this likely an over-representation as auto-pollinating species are easily recognised and observations are required only on the flowers. Other important pollinators include wasps (7%), flies (5%), birds (4%), settling moths (4%), sphingid moths (3%), butterflies (2.0%) and beetles (1.0%). Generalists, species pollinated by two or more of these groups of animals, represent 3% of species. Of the species for which data on rewards are available (including fragrance compounds, oils, wax and other exudates as well as nectar), 42% are deceptive. This is comparable with, but higher than the earlier estimates for the family.
... Consumption of nutrients and subsequent waste elimination are hallmark functionalities of a living organism. Although fluid feeding in insects (moths, mosquitoes, leafhoppers) has received considerable attention since Darwin's time 1 , little is known about the science and biofluid dynamics phenomena associated with waste elimination, despite having important ecological, morphological and evolutionary implications 2 . Specifically, we focus on how excretion influences smallbodied animals' behavior, morphology, and energetics since they face unique challenges due to their high metabolic rate 3 and physical limits set by the natural world 4 . ...
Food consumption and waste elimination are vital functions for living systems. Although how feeding impacts animal form and function has been studied for more than a century since Darwin, how its obligate partner, excretion, controls and constrains animal behavior, size, and energetics remains largely unexplored. Here we study millimeter-scale sharpshooter insects (Cicadellidae) that feed exclusively on a plant’s xylem sap, a nutrient-deficit source (95% water). To eliminate their high-volume excreta, these insects exploit droplet superpropulsion, a phenomenon in which an elastic projectile can achieve higher velocity than the underlying actuator through temporal tuning. We combine coupled-oscillator models, computational fluid dynamics, and biophysical experiments to show that these insects temporally tune the frequency of their anal stylus to the Rayleigh frequency of their surface tension-dominated elastic drops as a single-shot resonance mechanism. Our model predicts that for these tiny insects, the superpropulsion of droplets is energetically cheaper than forming jets, enabling them to survive on an extreme energy-constrained xylem-sap diet. The principles and limits of superpropulsion outlined here can inform designs of energy-efficient self-cleaning structures and soft engines to generate ballistic motions.
... The evolution of orchids has fascinated many biologists, with some of the earliest studies described in a book by Charles Darwin soon after the publication of his theory of evolution (Darwin, 1877). According to recent systematics, Orchidaceae are divided into five subfamilies, Apostasioideae (~15 species), Vanilloideae (~180 species), Cypripedioideae (~160 species), Orchidoideae (~5,000 species), and Epidendroideae (~22,000 species) . ...
Orchidaceae (with >28,000 orchid species) are one of the two largest plant families, with economically and ecologically important species, and occupy global and diverse niches with primary distribution in rainforests. Among orchids, 70% grow on other plants as epiphytes; epiphytes contribute up to ~50% of the plant diversity in rainforests and provide food and shelter for diverse animals and microbes, thereby contributing to the health of these ecosystems. Orchids account for over two‐thirds of vascular epiphytes and provide an excellent model for studying evolution of epiphytism. Extensive phylogenetic studies of Orchidaceae and subgroups have ;been crucial for understanding relationships among many orchid lineages, although some uncertainties remain. For example, in the largest subfamily Epidendroideae with nearly all epiphytic orchids, relationships among some tribes and many subtribes are still controversial, hampering evolutionary analyses of epiphytism. Here we obtained 1,450 low‐copy nuclear genes from 610 orchid species, including 431 with newly generated transcriptomes, and used them for the reconstruction of robust Orchidaceae phylogenetic trees with highly supported placements of tribes and subtribes. We also provide generally well‐supported phylogenetic placements of 131 genera and 437 species that were not sampled by previous plastid and nuclear phylogenomic studies. Molecular clock analyses estimated the Orchidaceae origin at ~132 million years ago (Ma) and divergences of most subtribes from 52 to 29 Ma. Character reconstruction supports at least 14 parallel origins of epiphytism; one such origin was placed at the most recent common ancestor of ~95% of epiphytic orchids and linked to modern rainforests. Ten occurrences of rapid increase in the diversification rate were detected within Epidendroideae near and after the K‐Pg boundary, contributing to ~80% of the Orchidaceae diversity. This study provides a robust and the largest family‐wide Orchidaceae nuclear phylogenetic tree thus far and new insights into the evolution of epiphytism in vascular plants.
Explanation of the epistemological presuppositions to which an evolutionary explanation of the origin of language must adhere and of the more general explanatory resources that could contribute to articulating this explanation.
Proponents of the concepts of plant intelligence and plant neurobiology often use historical sources as “evidence” and argue that eminent past scientists have supported ideas of plant intelligence, memory, learning, decision-making, agency, and consciousness. Historical sources include writings by Charles Darwin, Julius von Sachs, F. W. Went, K. V. Thimann, Barbara McClintock, and J. B. Lamarck. Advocates of plant neurobiology also argue that the ideas of J. C. Bose, an Indian scientist who is considered an important forerunner of plant neurobiology, were suppressed chiefly because of racism. Plant neurobiology has been criticized on scientific grounds, but there has not been close scrutiny of the use of historical sources as a form of evidence. We provide the first in-depth analysis of how historical sources have been used and misused, and conclude that there is a consistent pattern of distortion of these sources. Distortions include the use of erroneous quotations, alteration of quotations, selective quotations without context, and misinterpretation and exaggeration of historical statements. In the case of Bose, we show that there were legitimate scientific reasons for questioning his interpretations of botanical experiments and argue that this context cannot be ignored in evaluating contemporary responses to Bose. Overall, the common practice by proponents of plant intelligence and plant consciousness of uncritically citing the words of eminent scientists of the past, taken out of their historical context to bolster their arguments, should not be confused with scientific evidence supporting these concepts, even when the quotations, themselves, are accurate.
If Charles Darwin’s work opened up the possibility of a true natural history, the significance of time in evolutionary processes was left unresolved. This ambiguity has led to various interpretations of what evolutionary history is, some seeing it as the pure unfolding of processes, others as a flow marked by contingency and unpredictability. These interpretations reflect underlying differences in the perception of causality: mechanical and uniform on the one hand, transformative and multifaceted on the other. This tension affects not only our understanding of the Darwinian text, but also our contemporary conception of evolutionary theory. Although many challenges in evolutionary biology are linked to time (the historicity of evolution, path-dependent processes, biological rhythms, the contingency of certain evolutionary events etc.), the importance attributed to time in biology remains unspecified. The aim of this chapter is to study the contradictions regarding the conception of history and causality in Darwin’s writings and to analyse how they have permeated the different interpretations of evolutionary theory from the turn of the twentieth century to the present day. This analysis of the tensions within the different interpretations of Darwinism in history will lead me to address both the conception of biological time(s) and the approach to causality in contemporary evolutionary biology. I will conclude this chapter by proposing some clarifications about the significance of time in contemporary evolutionary biology.
Premise
Evolution of cross‐pollination efficiency depends on the genetic variation of flower traits, the pollen vector, and flower trait matching between pollen donors and recipients. Trait matching has been almost unexplored among nonheterostylous species, and we examined whether the match of anther length in pollen donors and stigma length in pollen recipients influences the efficiency of cross‐pollination. To explore potential constraints for evolutionary response, we also quantified genetic variation and covariation among sepal length, petal length and width, stamen length, style length, and herkogamy.
Methods
We created 58 experimental arrays of Turnera velutina that varied in the extent of mismatch in the position of anthers and stigmas between single‐flowered plants. Genetic variation and correlations among flower traits were estimated under greenhouse conditions.
Results
Style length, but not herkogamy, influenced the efficiency of cross‐pollination. Plants with stamen length that matched the style length of other plants were more efficient pollen donors, whereas those with the style protruding above the stamens of other plants were more efficient pollen recipients. Significant broad‐sense heritability (0.22 > h B ² < 0.42) and moderate genetic correlations (0.33 > r < 0.85) among floral traits were detected.
Conclusions
Our results demonstrated that anther‐stigma mismatch between flowers contributed to variation in the efficiency of cross‐pollination. The genetic correlations between stamen length and other floral traits suggests that any change in cross‐pollination efficiency would be driven by changes in style rather than in stamen length.
Background and aims – The study of factors and processes involved in evolutionary divergence can inform how biodiversity is generated and maintained. We evaluate shifts in phenology or in pollination systems as potential barriers to gene exchange and thus promoters of divergence at the population-species boundary in the plant ring-species Euphorbia tithymaloides in the Caribbean.
Material and methods – Combining collections-based and field-based observations and measurements, we evaluate evidence supporting that shifts in tempo of reproductive activity (floral phenology) or pollinator guilds (using visitation as a proxy) could be acting as mechanisms promoting divergence in E. tithymaloides . We focus on the geographic region where evolutionary divergence in this species has been documented: Greater and Lesser Antilles. Phenology data were derived from herbaria and online databases, for a total of 376 records across the Greater and Lesser Antilles. We quantified and characterized reward (nectar n = 13 sites) and gathered visitation data using direct observation (n = 12 sites) for a total of over 133 hours of observation/site.
Key results – The peak of floral activity of E. tithymaloides is in winter, when days are short (~late October–late May). Under natural conditions, plants in the Antilles produce up to 22.4 µL of nectar, with mean sugar concentrations of ~ 46.5 ºBrix that amount to up to 10.3 mg of total sugars, with no significant differences observed between plants of the Lesser and Greater Antilles. Hummingbirds are the main floral visitors of E. tithymaloides in both areas: Greater Antilles: 61%, Lesser Antilles: 85%, and network analyses support a floral visitor community turnover across islands/countries.
Conclusion – Evolutionary divergence in Caribbean E. tithymaloides along the Greater and Lesser Antilles is not accompanied by shifts in floral phenology or pollinator systems. Other factors, like pollinator turnover or pollinator-plant trait matching, might be at play. We outline hypotheses to this effect.
The use of exaptation's definition in architecture supports the heuristic value of cross-disciplinary studies on biology and architecture, which seem even more relevant in times of global environmental crises. This book aims to make a critique of the pre-existing and extensive paternalistic literature. Exaptation will be described as a functional shift of a structure that already had a prior, but different, function. In architecture, a functional shift of a structure that already had a function may apply to forms of decorative elements embedded in architectural components, and to both change of function of tectonic elements and the change of use of an architectural space. The book illustrated with examples from around the globe, including China, Italy, Mexico, New Zealand, the USA and the UK, and looks at different civilisations and diverse historical periods, ranging from the urban to the architectural scale. Such examples highlight the potential and latent human creative capacity to change the use and functions, something that cities and buildings could consider when facing disturbances. Exaptation is shown as an alternative narrative to the simplifications of evolutionary puritanism. It also offers an innovative perspective and presents an opportunity to re-think the manner in which we design and redesign our cities.
Florivory, i.e., flower herbivory, of various types is common and can strongly reduce plant fitness. Flowers suffer two very different types of herbivory: (1) the classic herbivory of consuming tissues and (2) nectar theft. Unlike the non-reversibility of consumed tissues, nectar theft, while potentially reducing a plant’s fitness by lowering its attraction to pollinators, can, in various cases, be fixed quickly by the production of additional nectar. Therefore, various mechanisms to avoid or reduce florivory have evolved. Here, I focus on one of the flowers’ defensive mechanisms, aposematism, i.e., warning signaling to avoid or at least reduce herbivory via the repelling of herbivores. While plant aposematism of various types was almost ignored until the year 2000, it is a common anti-herbivory defense mechanism in many plant taxa, operating visually, olfactorily, and, in the case of nectar, via a bitter taste. Flower aposematism has received only very little focused attention as such, and many of the relevant publications that actually demonstrated herbivore repellence and avoidance learning following flower signaling did not refer to repellence as aposematism. Here, I review what is known concerning visual-, olfactory-, and nectar-taste-based flower aposematism, including some relevant cases of mimicry, and suggest some lines for future research.
In angiosperms, diverse floral traits are adaptations to various selective pressures and ecological functions. So far, studies of floral traits in orchids have focused primarily on the labellum but never on bracts. A bumblebee-pollinated and rewarding terrestrial or epiphytic herb, Thunia alba (Lindley) H. G. Reichenbach (Orchidaceae), has conspicuously large and curly bracts that enclose the spur and pedicel of flowers. We hypothesized that these large bracts could protect spurs against nectar robbers. To confirm this hypothesis, we experimentally removed the bracts to record the changes in visiting behavior of mutualistic pollinators and antagonistic nectar robbers and evaluated their effects on reproduction success. Our result revealed that Bombus breviceps, the only pollinator of T. alba, shifts to nectar robbery when the bracts are removed, and the proportion of robbed flowers also significantly increased. T. alba was found to be pollinator-limited, whether in intact treatment or removed bract treatment. Removal of bracts had no effect on the visiting frequency of B. breviceps, but it reduced male and female reproductive success. Under complex environmental pressures with limited pollination, large bracts can protect against nectar robbers and enhance the fitness of T. alba.
This paper makes a phenomenological distinction between constitutive intentional movements and intentional actions. A phenomenological understanding of embodied and situated relations between living beings and their worlds shows that intentional movements do not imply an implicit or explicit experienced “what for” that organizes and directs what an organism does. We question the immanent teleology of autopoietic enactivism and the agentive semiotics theory. This discussion allows us to separate the idea of intentionality from objectives, goals, and agendas. This yields a different way of understanding the behavior of living beings based on the phenomenological notions of intentional body, intentional movement, animation, and the time-consciousness structure.
The concluding chapter of On the Origin of Species presents a comprehensive overview of the “one long argument” expounded by Darwin throughout the book. This chapter highlights critical elements of his exposition and the underlying objectives. It follows a detailed examination of the insights offered by the text concerning Darwin’s historical context and the humble way in which he submits his theory for scrutiny, not only by experts but also by his general readership. Building upon the Nature of Science (NOS) pedagogical construct, particular emphasis will be placed on aspects that embody the values inherent in scientific inquiry.
Two alternative views of an economy are combined and studied. The first view is that of technological evolution as a process of combinatorial innovation. Recently a simple mathematical model (TAP) was introduced to study such a combinatorial process. The second view is that of a network of product transformations forming an autocatalytic set. Autocatalytic (RAF) sets have been studied extensively in the context of chemical reaction networks. Here, we combine the two models (TAP and RAF) and show that they are compatible. In particular, it is shown that product transformation networks resulting from the combinatorial TAP model have a high probability of containing autocatalytic (RAF) sets. We also study the size distribution and robustness of such “economic autocatalytic sets”, and compare our results with those from the chemical context. These initial results strongly support earlier claims that the economy can indeed be seen as an autocatalytic set, and reconcile seemingly opposing views of evolution vs. mutualism in economics.
Significant fluctuations in the specific flux of CO2 from the soil surface within the experimental plot of old–growth forests were found, which is probably due to the spatial heterogeneity of the influence of factors related to the oxidative mineralization of organic matter. In all the studied cases, the presence of forest litter reduces the specific flux of CO2 by 1,07 to 2,18 times. The probability of obtaining an adequate indicator of the average specific CO2 flux without taking into account the phytogenic field of the tree or a certain coenogenic field won’t be informative enough. Therefore, in order to assess the Carbon balance, it is necessary to determine the amount of CO2 fixation and emissions during its destruction in a particular place, and then decide to which area this indicator can be extended.
Remarks are made on bee-pollinator dependency and autogamy of Spiranthes australis, the Australian member of a cosmopolitan orchid-genus found mainly in temperate zones of the northern hemisphere. Photographic evidence is provided showing pollination of S. australis by 5 different native bee taxa of the Apidae and Megachilidae families as primary and secondary vectors, and members of the Halictidae as secondary vectors.
Nineteenth-century final causes were ‘barren virgins’, an aphorism attributed to Francis Bacon, but twentieth-century teleology was a ‘mistress’, an adage of uncertain provenance. A study of historical uses of these gendered metaphors is used to probe changing attitudes toward teleological reasoning in biology. At the beginning of the nineteenth-century, invocations of final causes were commonplace but such idioms are rarely used at its end. This change is commonly attributed to publication of the _Origin of Species_ in 1859 which completed the ejection of final causes from biology. Charles Darwin, however, openly and unashamedly uses teleological reasoning and language in his botanical research. He believed he had naturalized, rather than eliminated, the concept of final cause. A more important reason for the eclipse of final causes was the shift within physiology toward the explanatory modes of the physical sciences which had long held final causes in disrepute. The rejection of final causes as explanatory principles occurred despite a persistence of teleological reasoning that was experienced as a ‘guilty secret’ likened to a mistress that a physiologist could not give up but would not acknowledge in public. Biology’s ambivalent attitude toward teleological explanations persists in the twenty-first century.
Perfume making in male orchid bees is a unique behavior that has given rise to an entire pollination syndrome in the neotropics.1,2 Male orchid bees concoct and store species-specific perfume mixtures in specialized hind-leg pockets3 using volatiles acquired from multiple environmental sources, including orchid flowers.4,5 However, the function and the ultimate causes of this behavior have remained elusive.2,6 Although previous observations suggested that male perfumes serve as chemical signals, the attractiveness for females has not be shown.7,8 Here, we demonstrate that the possession of perfume increases male mating success and paternity in Euglossa dilemma, a species of orchid bees recently naturalized in Florida. We supplemented males reared from trap-nests with perfume loads harvested from wild conspecifics. In dual-choice experiments, males supplemented with perfumes mated with more females, and sired more offspring, than untreated, equal-aged, control males. Although perfume supplementation had little effect on the intensity of male courtship display, it changed the dynamics of male-male interactions. Our results demonstrate that male-acquired perfumes are sexual signals that stimulate females for mating and suggest that sexual selection is key in shaping the evolution of perfume communication in orchid bees.
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