ArticlePDF Available

The Pollinators of the Malagasy Star Orchids Angraecum sesquipedale, A. sororium and A. compactum and the Evolution of Extremely Long Spurs by Pollinator Shift

Authors:

Abstract

Abstract: The pollination process of the extremely lang-spurred orchids Angraecum sesquipedale and A. sororium is described and documented here for the first time. The pollinaria and viscidia Ioad was examined in moths captured in central and south Madagascar. Visits to orchids by hawkmoths were rarely observed in the field and were therefore systematically recorded in !arge flight tents using a night-vision video technique and fla shlight photography. Angraecum sesquipedale in Fort Dauphin is pollinated by Xanthopan morgoni proedieta and A. sororium on Mt. Angavokely by Coelonia solani. By combining a deep nectar spur of extraordinary length with a protruding labellum functioning as a landing platform, these orchids overcome the moth's Stereotypie swing-hovering flight thus enabling full Insertion of the long tongue. Angroecum compaetum in Foret d'Ambohitantely is pollinated by both the shorter and longertongued forms of Ponogeno lingens which never swing-hover but is also exploited by X. morgani and C. solani with wastage of pollinaria. The duration of tongue Insertion, nectar exploitation and tongue withdrawal were analyzed: legitimate and illegitimate visito rs differ in their time budget and approach to the flower. Nectar volume, nectar Ievei and sugar concentration of A. sesquipeda/e and A. sororium were compared with the nectar requirements of the pollinating hawkmoths. The evolution of very long spurs in these orchids is likely to have involved a series of pollinator shifts. The orchids adapted to different hawkmoth species with increasingly long tongues which primarily evolved to avoid predator attacks during vis its to less specialized flowers. This "pollinator s hift" model modifies the dassical "coevolutionary race" model. The relevance of the taxon Angroecum bosseri Senghas is questioned.
A preview of the PDF is not available
... Hawkmoths of the genus Macroglossum are major effective pollinators for plants in tropical and temperate areas and usually pollinate white or creamy-white flowers with a tubular corolla, a strong scent, and low nectar sugar concentration [22,23]. Habenaria epipactidea (Orchidaceae) has a long nectar spur and hawkmoths insert their proboscides into the spur and remove pollinaria on their legs [24]. ...
... Floral traits reflect adaptation to a certain group of pollinators [26,27]. The nectar spur of Angraecum sesquipedale (Orchidaceae) is 30-40 cm long and it is pollinated by a hawkmoth whose tongue is about 30 cm long [22]. Long-tongued insects are also important pollinators for distylous plants. ...
Article
Full-text available
Background Floral morphs are characterized differentiations in reciprocal positions of sexual organs and ancillary floral traits in heterostylous plants. However, it remains unclear how differential floral morphs ensure reproductive success between morphs using the same pollinator. Results Measurements of floral traits in white-flowered Tirpitzia sinensis with long corolla tubes indicated that it is typically distylous, long-styled (L-) morph producing more but smaller pollen grains per flower than short-styled (S-) morph. Both morphs secreted more nectar volume at night than in the day and the sugar composition was rich in sucrose, potentially adaptive to pollination by hawkmoths ( Macroglossum spp.) which were active at dusk. A bumblebee species functioned as the nectar robber in both morphs and a honeybee as the pollen feeder in the S-morph. The L-morph secreted more nectar volume but relatively lower sucrose/hexose ratio than the S-morph. Floral visitation rate by hawkmoths was higher but its pollination efficiency was lower in the S-morph than the L-morph. Hand pollination treatments indicated self-incompatibility in T. sinensis and seed set of open-pollinated flowers did not differ between morphs. Conclusions Our findings suggest that the two morphs differ with respect to traits relevant to pollination. The L-morph, with its exserted stigma, has more pollen grains per anther and a greater volume of nectar, which may prolong the foraging time and increase the pollination efficiency of hawkmoths. The S-morph has a higher sucrose/hexose ratio in its nectar which can be more attractive to hawkmoths and increase the visit rates. Ancillary polymorphic floral traits between two morphs are adaptive to hawkmoth and ensure reproductive success in distylous plant T. sinensis .
... The novelty of the finding of this study of hawkmoth pollination in Erica cylindrica may reflect the relative difficulty involved in documenting nocturnal insect pollinators (e.g. Amorim et al., 2014;Johnson et al., 2020a;Wasserthal, 1997) but it may also reflect genuine rarity of hawkmoth pollination in the CFR (but see Goldblatt et al., 2005;Goldblatt and Manning, 2002a;Van der Niet et al., 2015), possibly due to the absence of suitable host plants for the larval stages of the life cycle (cf. Cottrell, 1985;Johnson, 1997;Johnson and Raguso, 2016). ...
Article
The predictive power of pollination syndromes has been demonstrated for many South African plant species with specialized pollination systems, but has rarely been tested in the florally diverse genus Erica. Here we evaluate the hypothesis that Erica cylindrica is moth-pollinated, based on its tubular, pale, and strongly scented flowers. Pollinator observations revealed exclusive nocturnal flower visitation by several hawkmoth species, and assessment of pollen loads confirmed that two hawkmoth species carried Erica pollen grains on their proboscises. Floral scent showed no clear periodicity in emission, but was dominated by benzenoid scent compounds including benzaldehyde, benzyl alcohol, benzyl acetate, and eugenol that are known to elicit antennal responses in hawkmoths. The pale cream flower colour was characterized by uniform reflectance across the human-visible light spectrum and a small secondary peak in the UV region. The volume of nectar produced was small, but the intermediate sugar concentration and sucrose:hexose ratio of 0.7 are consistent with hawkmoth pollination. More than three-quarters of flowers in an inflorescence are oriented upwards, which is highly unusual among South African ericas but has been shown to be adaptive in other hawkmoth-pollinated flowers. Anther-ring disruption indicated that at least 62% of flowers received visits and was associated with pollen deposition in 68% of visited flowers, suggesting that visitors are effective pollinators. Our study provides evidence for hawkmoth pollination of an Erica species, a system hitherto rarely recorded in Ericaceae. Several floral traits are consistent with the hawkmoth pollination syndrome, but further work is required to confirm the functional significance of these traits and the level of specialization in this hawkmoth pollination system.
... Among the moths, the settling moths (mainly of families other than Sphingidae, which hover when feeding from flowers) are extremely common and diverse flower visitors 19 but are less studied for their role in pollination. Many studies have focused on pollination by Sphingidae (i.e. the Sphingophily) [20][21][22][23][24][25][26][27][28][29][30][31] . The role of settling moths as pollinators i.e. the Phalaenophily 29 has also been studied, but arguably to a lesser degree 19,27 . ...
Article
Full-text available
Majority of the pollination related studies are based on the diurnal pollinators, and the nocturnal pollinators received less scientific attention. We reveal the significance of settling moths in pollination of angiosperm families in Himalayan ecosystem of North-East India. The refined and novel method of pollen extraction from the proboscides provides a more robust assessment of the pollen carrying capacity. The study is based on one of the largest data sets (140 pollen transporter moth species (PTMS)), with interpretation based on seasonal as well as altitudinal data. In the present study about 65% moths (91 species) carried sufficient quantities of pollen grains to be considered as potential pollinators (PPMS). Teliphasa sp. (Crambidae) and Cuculia sp. (Noctuidae) are found to carry the highest quantity of pollen. We found pollen grains of 21 plant families and the abundant pollen are from Betulaceae, Fabaceae, Rosaceae and Ericaceae. Species composition of PTMS and PPMS in pre-monsoon, monsoon, and post-monsoon revealed the dominance of Geometridae. Maximum diversity of PTMS and PPMS is found from 2000 to 2500 m altitude. The nocturnal pollen transfer network matrices exhibited high degree of selectivity (H2ʹ = 0.86).
... Pollination was the most common biotic interaction found in the abstracts in our systematic review, with approximately 36 % of articles (109) discussing pollination in the abstract (Fig. 1). Flower morphology of some epiphytic orchids mimics insect pollinators, and several examples exist of coevolution between epiphytic orchid flowers and pollinator traits, such as tongue length (Baguette et al., 2020;Micheneau et al., 2009;Wasserthal, 1997). Likewise, epiphytic and hemiepiphytic figs engage in an unusual mutualism with wasps, wherein figs attract female wasps into their closed inflorescence (the fig), which pollinate and lay an egg into the inflorescence (e.g., Harrison, 2005). ...
Article
Biotic interactions are widely accepted as an important driver of ecological and evolutionary patterns, contributing to the structure of systems as diverse as tropical tree seedlings, intertidal barnacles, and wildflower-pollinator networks. Species interactions within a trophic level, such as competition and facilitation, can drive patterns of community change over time, yielding both fundamental ecological theories of succession as well as insight vital to predicting biodiversity conservation priorities. One system in which biotic interactions are poorly explored is epiphytes, or structurally dependent, non-parasitic organisms. This is a topic of broad interest because epiphytes—including vascular plants, bryophytes, and lichens—exist in practically all terrestrial ecosystems throughout the world. From lichens acting as pollution-sensitive indicator species in urbanized landscapes, to the multimillion-dollar commercial market for horticultural bromeliads, to tropical orchids representing striking examples of rapid speciation, epiphytes make substantial contributions to theory, biodiversity, ecosystem services, and the global economy. This review is the first to broadly synthesize the underlying biotic interactions important to epiphyte ecology and evolution. We first draw from theory to discuss where and when biotic or abiotic processes are likely stronger drivers of epiphyte dynamics. We then systematically review the literature across the major interaction modes, highlighting areas where different groups of epiphytes (e.g., vascular versus nonvascular) and ecosystems have contrasting patterns or expectations. Throughout, we illustrate where research efforts have focused and where large gaps in knowledge exist. Our review is organized around the major biotic interactions, rather than the specific organisms interacting with the epiphytes, to highlight general processes and set epiphytism within the framework of ecological and evolutionary theory. Our review encompasses pollination and dispersal, intratrophic facilitation and competition, mycorrhizal mutualisms, epiphyte-host interactions, parasitism and pathogens, and herbivory, focusing on the impact of these interactions on the epiphyte. Finally, we provide a simple conceptual framework distilling open questions in the field, expand our findings to the community and ecosystem level, and summarize the biodiversity conservation implications of ignoring biotic interactions in epiphytes. Our synthesis brings together currently disparate literature from tropical and temperate systems on vascular and nonvascular plants and lichens. We hope our review stimulates further research and inspires cross-disciplinary collaboration.
... These pollination syndromes or combination of floral traits are known to have independently evolved to attract hawkmoths (Ashworth et al. 2015). In tropical Africa, several studies on this pollination syndrome have been performed in its eastern part (see Martins & Johnson 2007, 2013, its southern part (see Luyt & Johnson 2001;Johnson & Raguso 2016;Johnson et al. 2017), and in Madagascar (see Nilsson et al. 1985Nilsson et al. , 1987Nilsson et al. , 1992Nilsson 1992Nilsson , 1998Wasserthal 1997); yet such studies are missing for Central Africa. Most of these previous studies on angraecoid orchids pollination have demonstrated that the long nectar spurs of orchids and the proboscis of pollinators are involved in evolutionary processes resulting in the remarkable angraecoid floral specialization. ...
Article
Full-text available
Background and aims-A recent taxonomic and molecular study of the genus Cyrtorchis revealed three new species. Here, we describe one of these new species, endemic to the Cameroon Volcanic Line (CVL), and compare it to its closest relatives. Its conservation status is provided along with detailed information on its ecology and reproductive biology. Material and methods-A detailed examination of 21 herbarium specimens was performed using standard practices of herbarium taxonomy. The conservation status of the new species was assessed using the IUCN Red List Categories and Criteria. Furthermore, we investigated the reproductive biology of the new species in an easily accessible subpopulation in Cameroon and tested the hypothesis of hawkmoth pollination in the genus Cyrtorchis. Key results-The newly discovered species, here named C. okuensis, is restricted to the montane forest (1600 to 2500 m elevation) of the CVL and is currently assessed as Near Threatened (NT). Among angraecoid orchids in which hawkmoth pollination is recorded (~16 species), C. okuensis has the shortest nectar spur (19-40 mm). In situ observations revealed hawkmoths with short proboscis of the genus Hippotion (H. celerio, H. eson, and H. osiris) as the main pollinators. The rate of pollination and fruiting under natural conditions was low and among the 448 surveyed flowers only 38.8% (174/448 flowers) had their pollinia removed, 19% produced fruits (87/448 flowers), and 16% (70/448 flowers) set mature fruits. Conclusion-Cyrtorchis okuensis is clearly differentiated from C. submontana by its longer and wider floral bracts, longer anther caps, and wider triangular dorsal sepal.
... Par exemple, le pays présente un taux d'endémisme très élevé en espèces d'abeilles (90% d'espèces endémiques et cinq genres endémiques) (Eardley et al., 2009). Des cas d'interactions spécifiques entre des insectes et des orchidées ont été reportés à plusieurs reprises dans la grande île (Nilsson et al., 1992(Nilsson et al., , 1986Petersson, 2015;Wasserthal, 1997). Comme les insectes ont un schéma de distribution varié à Madagascar allant d'une très large répartition (ex : Halictus jucundus) à une seule localité (ex : Nubenomia luridipes) (Pauly et al., 2001), cela aurait probablement joué un rôle dans la spéciation écologique entre les espèces d'orchidées appartenant à des écorégions très différentes de l'île. ...
Thesis
Full-text available
La diversité biologique est inégalement répartie sur la planète, étant majoritairement concentrée sur quelques points chauds appelées « hotspots de la biodiversité ». La région Sud-Ouest de l’océan Indien (SOOI) figure parmi les régions prioritaires pour la conservation de la biodiversité et des orchidées. Leader mondial en production de gousses de vanille, cette région abrite également une diversité importante en espèces aphylles endémiques appartenant au genre Vanilla Plum. ex. Miller (Orchidaceae), majoritairement distribuées à Madagascar. Les vanilliers aphylles, par leur capacité d’adaptation à la sècheresse et leurs potentialités médicinales, présentent un intérêt économique et scientifique majeur. Ces espèces forment un groupe monophylétique différencié récemment à partir d’un ancêtre folié africain. Elles ont des traits morphologiques similaires et sont indissociables à partir de marqueurs chloroplastiques, rendant leur statut taxonomique douteux. A Madagascar, elles sont réparties principalement dans les forêts sèches de la côte Ouest, classées parmi les écosystèmes les plus menacés de l’île. Dans l’objectif de contribuer à leur conservation, des prospections suivies d’échantillonnages ont été réalisés dans plusieurs localités de Madagascar. Ensuite, une approche intégrative combinant la génétique, la biologie et l’écologie a été réalisée pour résoudre la taxonomie de ces espèces et déterminer leur statut de conservation. D’après les analyses des données microsatellites et morphologiques, la différenciation des sept groupes génétiques identifiés à Madagascar résulterait de plusieurs facteurs dont principalement les barrières géographiques (rivières), l’isolement par les facteurs environnementaux (IBE) (température, élévation, pH du sol) fortement corrélé à la géographie (IBD), et l’isolement par adaptation (IBA) de traits floraux (résultant soit de l’IBE soit d’une sélection divergente par les pollinisateurs). L’étude taxonomique intégrative (phylogénie ITS, analyse populationnelle microsatellite et morphologique) divise les vanilliers du SOOI en deux grands clades : espèces à fleurs blanches versus espèces à fleurs jaunes. Dans le clade des espèces à fleurs blanches, V. decaryana (Madagascar) et V. roscheri (Afrique de l’Est) forment chacune un groupe monophylétique tandis que V. madagascariensis (Madagascar), V. bosseri (Madagascar) et V. phalaenopsis (Seychelles) apparaissent conspécifiques (ITS), mais récemment différenciées (microsatellites). L’étude révèle également la présence de deux nouvelles espèces, réparties à l’Est, qui ont été nommées V. allorgii et V. atsinananensis et décrites. Dans le clade des aphylles à fleurs jaunes, V. perrieri (Madagascar) semble s’être différenciée de V. humblotii (Madagascar et Comores). La configuration de l’arbre ITS soutient une origine malgache de ces deux grands clades, suivie de trois colonisations indépendantes vers l’Afrique de l’Est, l’Archipel des Comores et les Seychelles. D’après les tests de pollinisations réalisés, les espèces aphylles sont auto-compatibles mais dépendent de pollinisateurs et peuvent se croiser entre elles. Les analyses de la diversité génétique, de la biologie de la reproduction et la modélisation spatiale et temporelle des niches écologiques des sept espèces malgaches suggèrent que V. allorgii et V. atsinananensis sont menacées respectivement par la faible densité des populations et une perte d’interaction avec les pollinisateurs. La fragmentation des populations naturelles de V. decaryana a entrainé une perte de diversité génétique ainsi qu’une forte consanguinité. V. madagascariensis et V. humblotii ont des zones de distribution restreintes dans le Nord, pouvant menacer leur survie à long terme. V. perrieri et V. bosseri semblent être les moins vulnérables car largement réparties le long de la côte Ouest. Des mesures de conservation ex situ et in situ sont proposées pour optimiser la conservation de ces vanilliers sauvages à Madagascar.
Article
The morphology of the proboscis and associated feeding organs was studied in several nectar‐feeding hawk moths, as well as a specialized honey‐feeder and two supposedly non‐feeding species. The proboscis lengths ranged from a few millimeters to more than 200 mm. Despite the variation in proboscis length and feeding strategy, the principle external and internal composition of the galeae, the stipes pump and the suction pump were similar across all species. The morphology of the smooth and slender proboscis is highly conserved among all lineages of nectar‐feeding Sphingidae. Remarkably, they share a typical arrangement of the sensilla at the tip. The number and length of sensilla styloconica are independent from proboscis length. A unique proboscis morphology was found in the honey‐feeding species Acherontia atropos. Here, the distinctly pointed apex displays a large subterminal opening of the food canal, and thus characterizes a novel type of piercing proboscis in Lepidoptera. In the probably non‐feeding species, the rudimentary galeae are not interlocked and the apex lacks sensilla styloconica; galeal muscles however, are present. All studied species demonstrate an identical anatomy of the stipes‐ and suction pump, regardless of proboscis length and diet. Even supposedly non‐feeding Sphingidae possess all organs of the feeding apparatus, suggesting that their proboscis rudiments might still be functional. The morphometric analyses indicate significant positive correlations between galea lumen volume and stipes muscle volume as well as the volume of the food canal and the muscular volume of the suction pump. Size correlations of these functionally connected organs reflect morphological fine‐tuning in the evolution of proboscis length and function. This article is protected by copyright. All rights reserved.
Article
Full-text available
Since Darwin, very long and narrow floral tubes have been known to represent the main floral morphological feature for specialized long-tongued hawkmoth pollination. However, specialization may be driven by other contrivances instead of floral tube morphology. Asclepiads are plants with a complex floral morphology where primary hawkmoth pollination had never been described. We detailed here the intricate pollination mechanism of the South American asclepiad Schubertia grandiflora, where functional specialization on long-tongued hawkmoth pollinators occurs despite the short floral tube of this species. We studied two plant populations in the Brazilian Cerrado and recorded floral visitors using different approaches, such as light-trapped hawkmoths for pollen analysis, direct field observations, and IR motion-activated cameras. Finally, using a community-level approach we applied an ecological network analysis to identify the realized pollinator niche of S. grandiflora among the available niches in the pollinator community. Throughout a period of 17 years, long-tongued hawkmoths were consistently recorded as the main floral visitors and the only effective pollinators of S. grandiflora. Flowers rely on highly modified corona and gynostegium, and enlarged nectar chambers, to drive visitors and pollination mechanism. Despite relatively short-tube, network analysis placed S. grandiflora in the module including exclusively long-tongued hawkmoth pollinators and the most phenotypically specialized sphingophilous plants in the community. These results represent the first example of functional specialization in long-tongued hawkmoths in an asclepiad species. However, this specialization is uncoupled from the long floral tubes historically associated with the sphingophily syndrome.
Chapter
Pollination is a multi-million-year-old co-evolutionary process involving flowering plants and pollinators. It is one of the most important mechanisms in preservation and promotion of biodiversity as well as life on Earth. Pollinator diversity is essential for maintaining overall biological diversity in many habitats including agro-ecosystems. Pollinators are responsible for assisting reproduction in over 80% of the world’s flowering plants. In their absence, humans and wildlife would go hungry. Insects are the most efficient pollinators as they play a crucial part in pollination ecology. Pollinators and their habitats have ecological, economic, cultural and social benefits. Pollination efficiency is highly dependent on certain attributes and characteristics of pollinators such as vision, anatomy, food preferences, olfaction, behaviour and learning ability. With the rapid growth of human population, our demand for food has also risen. Our agricultural systems will need to produce more food in a sustainable manner in the future to cope with this. Pollinators play an important role in these ecosystems and will continue to do so in the future. Because pollinators are so important to agriculture, we need to learn more about which crops require specific pollinators and how to best maintain and promote both wild and controlled species. Their diversity needs protection because there are specific relationships between certain crops and pollinators. Pollinator communities are suffering as a result of man-made habitat disruptions, including severe biodiversity loss. This diversity must be protected by combining conservation measures with sustainable farming practices which could increase crop yields while protecting insect pollinator species.
Article
Narrative is increasingly promoted for improving science communication and thus combatting misinformation and facilitating fact-based education and policy (Dahlstrom 2014; ElShafie 2018). This instrumental use of narrative is laudable, but current approaches tend to be reductive and therefore potentially counterproductive. Most proponents of narrative science view narrative as a mere formula, often derived from entertainment (Luna 2013; Olson 2015; Loverd et al. 2018). Sceptics rightly worry that using narrative formats in this way oversimplifies and distorts scientific information. Given the social, medical, and environmental urgency of effective and accurate scientific communication, the shortcomings and promise of narrativizing science represent a limit-case for the applicability and scope of narrative theory and practice. In the context of narrative science, this essay begins by examining two valences of the term “limits of narrative.” First, it criticizes the current project of narrativizing science for failing to recognize narrative’s limited capacity to handle complex scientific models and phenomena, which H. Porter Abbott has upheld as exemplary cases of the “unnarratable” (2008: 227). The second valence of “limits” emerges as a response to the first. Although scientific information often eludes narrativity, what is unnarratable now may become narratable tomorrow. As Robyn Warhol suggests, attempts to render the unnarratable can create newly narratable ground, which she calls “neonarrative” (2005: 221). That is, new narrative forms arise at the limits of the narratable. This is a territory where scientists, like experimental novelists, struggle to express new, counterintuitive models, theories or results. What biologist Lewis Wolpert calls “the unnatural nature of science” (1998)—its resistance to commonsense notions of causality and ontology—could just as well be called the unnarratable nature of science. The essay argues that an effective use of narrative in science would need to accept the limits of narrative, probing for neonarrative footholds at those limits; those neonarrative forms would likely be challenge or violate the narrative templates audiences bring to texts of various kinds. By way of illustration, the article analyzes willfully artificial elements in diagrams depicting coevolution between pollinators and plants (Nilsson 1988; Pauw et al. 2009), a narrative whose agents and events are relative statistical values rather than discrete entities. By foregrounding the “synthetic aspect” of their characters (Phelan 1989), these diagrams showcase how scientific texts use the communicative efficacy of narrative without sacrificing accuracy or complexity.
Article
Full-text available
Virtually all flower-visiting insect groups had already existed at the time of early angiosperm differentiation; beetles, flies, thrips, and moths were available as potential pollinators. Unspecific interactions with these insect groups are found in the Winteraceae, archaic Magnoliidae. Winteraceae are often weedy species for which an open pollination system may be advantageous in view of the different insect faunas of newly invaded habitats. Winteraceous pollination modes and life strategies are here interpreted as close to the ancestral condition of the angiosperms. The Annonaceae provide examples of more economic and effective plant/pollinator interactions. Within this family a range exists of different adaptations for pollination by beetles. Flowers in several genera provide pollination chambers resulting from enfolding petals in which beetles stay for long periods of time. In the dark chambers the beetles are protected against environmental changes and predators. The permanently recurved microsporophylls of the flowers of the late bennettitalean genus Cycadeoidea, evolving during the early Cretaceous, may be a comparable adaptation to beetle pollination.
Article
Full-text available
The baobabs comprise eight species with large, spectacular, nocturnal flowers. The African baobab, Adansonia digitata, has long been known to be bat-pollinated. In this paper I document the floral biology and pollination systems of the remaining seven species. The two species in section Brevitubae, both endemic to Madagascar, are pollinated by nocturnal mammals (fruit bats and lemurs). In contrast, the five species in section Longitubae, four endemic to Madagascar and one to Australia, are pollinated by long-tongued hawkmoths. In all cases, animals besides the legitimate pollinators also exploited nectar and pollen. The two pollination systems occurring in the genus correlate closely with differences in the floral morphology, phenology, and nectar production.
Article
Studies on hawkmoth pollination in a primary forest in central Madagascar indicated that at least five of six flowering, long-spurred angraecoid species exploited the same hawkmoth, Panogena lingens. as a pollen vector. Several other long-tongued hawkmoth species were present, but no evidence was found that they participated in orchid pollination. The pollinaria of Angraecum arachnites, A. compactum, Neobathiea grandidierana, and Jumellea teretifolia were deposited on the basal portion of the proboscis. The latter three species utilized the same dorsal portion of the proboscis, whereas attachment by A. arachnites was ventral. The pollinaria of Aerangis fuscata were deposited on the frons and palps. Hawkmoths frequently carried mixed loads, but at least ethological and mechanical mechanisms seemed to restrict interspecific pollination. The P. lingens-angraecoid orchid relationship may have reached a specialized state before progenitors of other long-tongued Sphingidae colonized or evolved in central Madagascar.
Article
Some plants have evolved flowers of extraordinary depth, a phenomenon which puzzled Darwin1. Darwin suggested that the evolution of deep flowers could be a response to a kind of 'race' with pollinating insects: the length of the tongues of pollinating insects could increase as a result of a general size increase, or because it increased their nectar foraging efficiency. As this occurred, plants with relatively shallow flowers could be disadvantaged since pollen transfer, which is effected by physical contact between the pollinator and the anthers or stigma of the plant, could be reduced when the insect tongue is long relative to flower depth. This could lead to the evolution of increasing flower depth which in turn could drive the evolution of a further increase in insect tongue length. Various predictions of Darwin's proposal were tested here for orchid species with deep flowers that are pollinated by moths. It was found that insects do indeed insert their probosces no further than necessary to obtain nectar; that an experimental reduction in flower depth reduces both the male and female components of fitness; and that in natural populations there is a correlation between flower depth and female fitness measured by fruit set. These results all support Darwin's hypothesis to explain the evolution of flower depth.
Article
Native species with hawkmoth flowers in temperate North America north of Mexico contains 105 species in 16 families; hawkmoth pollination records are available for 38 species in 12 families. The most important single group contributing hawkmoth flowers is Oenothera (40 species) followed by Nyctaginaceae (13 species in the Southwest), Amaryllidaceae (15 species in the South and Southeast) , and Datura (5 widely distributed species). Temperate North American sphingophilous plant species fall into 2 classes in terms of their floristic affinities: 1) subtropical or tropical species that extend north into the southern part of the United States, and 2) new indigenous species that have evolved in temperate North America. The floral tube in most of these sphingophilous species is moderately long, 2-7 cm, corresponding to the proboscis length of common and widespread sphingids such as Hyles lineata. A number of sphingophilous species in the southern part of the United States have floral tubes of 9 cm or more. The SW sphingophilous species with very long tubes are associated with Manduca moths with correspondingly long proboscides. A comparable association may occur in the south-central and southeastern United States. -from Author
Article
Examined the "glint" hypothesis (e.g., R. Kober, 1982), which postulates that the wings of insects are perpendicular to impinging sound waves at the moment of amplitude peak (i.e., glint) of constant frequency (CF) echoes produced by echolocating bats. Data were obtained from insects mounted 40 cm in front of an ultrasonic loudspeaker and ensonified with either an 80-kHz CF or a short frequency modulation (FM) signal sweeping from 82 to 18 kHz in 2 msec. Data are presented on the information found in FM echoes and on the echo sound pressure levels of insects at different sizes and ranges. Findings have implications for the relationship between type of echolocation call and hunting behavior. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
The pollination biology of the epilithic endemic Aerangis ellisii (Reichenb. fil.) Schltr. (Orchidaceae) was studied on an inselberg in the Antananarivo region, central Madagascar. The flowers exhibit long nectariferous spurs indicative of hawk-moth pollination, the mechanism evidently involving pollinia transfer via the frons and palpi of the vectors. Analysis of hawk-moth scales on naturally pollinated stigmas showed that the principal pollinators were Agrius conuolvuli (Linnaeus) and Panogena lingens (Butler). Proboscis morphology of long-tongued Malagasy Sphingidae in relation to nectar position and spur morphology in A. ellisii also indicated that A. conuolvuli and P. lingens were best suited to interact with the plant's floral adaptation. Aerangis ellisii seems to display a relatively moderate specialization versus the Malagasy hawk-moth guild since its nectar is accessible even to those long-proboscis hawk-moth species which are not able to act as pollinators.