Reproductive biology of an endangered lithophytic shrub and implications for its conservation.

BACKGROUND: Plants in cliff habitats may evolve specific reproductive strategies to cope with harsh environments, and unraveling these reproductive characteristics can improve our understanding of survival strategies and lithophyte evolution. This understanding is especially important for efforts to protect rare and endemic plants. Here, we investigated the reproductive biology of Lonicera oblata, an endangered lithophytic shrub that is scattered in highly fragmented and isolated cliff habitats of the Taihang and Yan mountains in North China. RESULTS: Flowers of L. oblata are herkogamous and protandrous, characteristics that can prevent autogamy at the single-flower level, and insects are necessary for pollination. The outcrossing index, pollen/ovule ratio, and the results of hand pollination were measured and all revealed a mixed mating system for L. oblata, that combines cross-fertilization and partial self-fertilization. The floral traits of L. oblata of zygomorphic and brightly yellowish corolla, heavy fragrance, and rich nectar, suggest an entomophilous pollination system. Sweat bees were observed as the most effective pollinators but their visiting frequencies were not high. Pollen limitation may limit the reproductive success of L. oblata. CONCLUSIONS: We determined the reproductive characteristics of L. oblata, a critically endangered species endemic to cliffs in North China, providing insight into its endangerment and suggesting conservation strategies. L. oblata has highly pollinator-dependent self-fertilization as part of a mixed mating system. Floral features such as low-flowering synchrony, asynchronous anthers dehiscence, and high duration of stigma receptivity, improve pollination efficiency in the case of low pollinator service. Our work provides reference information to understand the survival strategies and conservation of L. oblata and other lithophytes.

Floral adaptations of two lilies: implications for the evolution and pollination ecology of huge trumpet-shaped flowers.

PREMISE: Evolutionary transitions among floral morphologies, many of which provide evidence for adaptation to novel pollinators, are common. Some trumpet-shaped flowers are among the largest flowers in angiosperms, occurring in different lineages. Our goal was to investigate the role of pollinators in the evolution of these flowers using Lilium. METHODS: We investigated floral traits and pollinators of L. primulinum var. ochraceum and L. brownii var. viridulum and reviewed reports of visitors to huge trumpet-shaped flowers. Using a published phylogeny of Lilium, we reconstructed ancestral floral morphological states in Lilium to elucidate the origins of trumpet-shaped lilies. RESULTS: Both lilies are largely self-incompatible and show floral syndromes indicative of hawkmoth pollination. The short trumpet-shaped lily can be pollinated by short-tongued (<40 mm) but not long-tongued hawkmoths (>65 mm), while the huge trumpet-shaped lily can be pollinated by both. A literature review including 22 species of trumpet-shaped flowers suggests that their pollinator guilds commonly include both short- and long-tongued moths. A phylogenetic reconstruction indicates that trumpet-shaped lilies possibly have multiple origins from tepal-reflexed ancestors, at least six of which have evolved huge flowers (>50 mm). CONCLUSIONS: Adaptation to short-tongued hawkmoths may have initiated the evolution of trumpet-shaped lilies. Huge trumpet-shaped lilies may have evolved as a response to selection by long-tongued hawkmoths, without excluding the short-tongued ones. This evolutionary pathway leads to a functionally more generalized pollination system instead of an increasingly specialized one and is not necessarily associated with pollinator shifts.

Adaptation for rodent pollination in Leucospermum arenarium (Proteaceae) despite rapid pollen loss during grooming.

BACKGROUND AND AIMS: Plants are adapted for rodent pollination in diverse and intricate ways. This study explores an extraordinary example of these adaptations in the pincushion Leucospermum arenarium (Proteaceae) from South Africa. METHODS: Live trapping and differential exclusion experiments were used to test the role of rodents versus birds and insects as pollinators. To explore the adaptive significance of geoflory, inflorescences were raised above ground level and seed production was compared. Captive rodents and flowers with artificial stigmas were used to test the effect of grooming on the rate of pollen loss. Microscopy, nectar composition analysis and manipulative experiments were used to investigate the bizarre nectar production and transport system. KEY RESULTS: Differential exclusion of rodents, birds and insects demonstrated the importance of rodents in promoting seed production. Live trapping revealed that hairy-footed gerbils, Gerbillurus paeba, and striped field mice, Rhabdomys pumilio, both carried L. arenarium pollen on their forehead and rostrum, but much larger quantities ended up in faeces as a result of grooming. Terrarium experiments showed that grooming exponentially diminished the pollen loads that they carried. The nectar of L. arenarium was found to be unusually viscous and to be presented in a novel location on the petal tips, where rodents could access it without destroying the flowers. Nectar was produced inside the perianth, but was translocated to the petal tips via capillary ducts. In common with many other rodent-pollinated plants, the flowers are presented at ground level, but when raised to higher positions seed production was not reduced, indicating that selection through female function does not drive the evolution of geoflory. CONCLUSIONS: Despite the apparent cost of pollen lost to grooming, L. arenarium has evolved remarkable adaptations for rodent pollination and provides the first case of this pollination system in the genus.

Gradual pollen presentation in Vaccinium corymbosum 'Bluecrop': an adaptive mechanism to improve pollination efficiency and outcrossing.

Gradual pollen presentation is a plant reproductive mechanism to improve pollination efficiency and accuracy and promote outcrossing. Vaccinium corymbosum 'Bluecrop' has a typical gradual pollen presentation mechanism. 'Bluecrop' exhibits an inverted bell-shaped flower with a white coloration. By investigating the flower syndrome, pollination characteristics, pollination efficiency, and breeding system of 'Bluecrop', this study aims to explore the adaptive significance of these traits. The results showed 'Bluecrop' released pollen gradually through anther poricidal dehiscence. Among different pollinators, Apis mellifera and Bombus can pollinate effectively, and the mechanism of gradual pollen presentation significantly improved the efficiency of pollen transfer. This characteristic limits the amount of pollen removed by the pollinators and prolongs pollen presentation, thus attracting more pollinators and thereby increasing male fitness. The nectar secretion of 'Bluecrop' is gradual, with a large nectar production and a long phase of nectar secretion, enhance visitation frequencies and the chances of successful pollination. At the same time, campanulate corolla can protect pollen as well as nectar from waste due to environmental factors and other effects. The breeding system of 'Bluecrop' relies mainly on outcrossing because of its low affinity for self-fertilization and good interaction with pollinating insects. Thus, the special floral syndrome and the mechanism of secondary pollen presentation are significant in improving pollination efficiency and promoting the reproductive success of 'Bluecrop' by outcrossing. It can provide a certain theoretical basis for the future propagation breeding of 'Bluecrop'.

Reproductive Biology and Breeding Systems of Two Opisthopappus Endemic and Endangered Species on the Taihang Mountains.

Opisthopappus is a perennial, endemic herb of the Taihang Mountains in China. Two species of this genus (O. longilobus and O. taihangensis) are important wild genetic resources for Asteraceae; however, their reproductive biology has been lacking until now. This study is the first detailed report on the reproductive biology and breeding systems of two Opisthopappus species. Through field observations, the floral syndromes of O. longilobus and O. taihangensis were found to possess a similar pattern, although O. taihangensis has a relatively larger capitulum, more ray ligules, and disc florets. The flowers of both O. longilobus and O. taihangensis are protandrous, a character that can prevent autogamy at the single-flower level, and insects are required for pollination. Further, brightly ligules, brightly bisexual florets, unique fragrance, and amount of nectar suggest that these species propagate via an entomophilous pollination system. Hymenopteran and Diptera species were observed as the effective pollinators for these two species. The outcrossing index, pollen/ovule ratio and the results of hand pollination indicated that these Opisthopappus species might have a mixed mating system that combines cross-fertilization and partial self-fertilization for O. longilobus and O. taihangensis, outcrossing predominated in the breeding system, while self-pollination played an important role in seed production when insect pollination was unavailable, particularly in a harsh environment, such as the Taihang Mountains cliffs. Meanwhile, O. taihangensis might better adapt to severe surroundings with relatively complex floral syndromes, specifically through the attraction of visiting insects and a high seed set rate. The above results not only provide reference information toward a better understanding of the survival strategies of O. longilobus and O. taihangensis in the Taihang Mountains but also lay a solid foundation for further exploring the molecular mechanisms that underly their adaptation under cliff environments.

Evolution of Bird and Insect Flower Traits in Fritillaria L. (Liliaceae).

Pollinators are often perceived as a primary selective agent influencing flower traits such as colour, size, and nectar properties. The genus Fritillaria L. (Liliaceae), comprising approximately 150 species, is described as generally insect pollinated. However, there are at least three exceptions: two hummingbird-pollinated North American species and one passerine-pollinated Asian species. Despite this variation in pollination, little is known about flower traits that may accompany this shift in fritillaries. In this study, we aimed to assess the attractiveness of the floral traits for (new) pollinators and track the evolution of flowers traits in the context of a shift in the principal pollinator. Therefore, we studied 14 flower traits related to the pollination in 60 Fritillaria species and traced the evolutionary trajectory of these traits. We used a phylogenetic tree of the genus, based on five DNA markers (matK, rpl16, and rbcL, 18S, and ITS) to reconstruct the ancestral state of studied flower traits. The results show that in bird-pollinated species several new traits evolved. For example, flower colouration, nectar sugar, and amino acid concentration and composition fulfil the criteria of ornithophilous flowers, although flower traits do not exclude insect pollinators in bird-pollinated fritillaries. Interestingly, we recorded potential reversals from bird to insect pollination. Our analysis, showing a broad study of flower traits among closely related species in the context of pollinator shift, serves as a starting point for future work exploring the genetic and physiological mechanisms controlling flower traits in the genus Fritillaria.

How specialised is bird pollination in the Cactaceae?

Many cactus species produce 'bird' flowers; however, the reproductive biology of the majority of these species has not been studied. Here, we report on a study of the pollination of two species from the Cleistocactus genus, cited as an ornithophilous genus, in the context of the different ways in which they are specialised to bird pollination. In addition, we re-evaluate the level of specialisation of previous studies of cacti with bird pollination and evaluate how common phenotypic specialisation to birds is in this family. Both Cleistocactus species exhibited ornithophilous floral traits. Cleistocactus baumannii was pollinated by hummingbirds, whereas Cleistocactus smaragdiflorus was pollinated by hummingbirds and bees. Pollination by birds has been recorded in 27 cactus species, many of which exhibit ornithophilous traits; however, they show generalised pollination systems with bees, bats or moths in addition to birds being their floral visitors. Of all cactus species, 27% have reddish flowers. This trait is associated with diurnal anthesis and a tubular shape. Phenotypic specialisation to bird pollination is recognised in many cactus species; however, it is not predictive of functional and ecological specialisation in this family.

Fenología reproductiva y anatomía floral de las plantas Aloe vera y Aloe saponaria (Aloaceae) en Cumaná, Venezuela

Reproductive phenology and flower anatomy of the plants Aloe vera and Aloe saponaria (Aloaceae) in Cumana, Venezuela. The reproductive phenology and the floral anatomy of two species of Aloe kept under nursery conditions were analized in eastern Venezuela from September 2001 to September 2002. A. vera flowered between December and May; A. saponaria from November through August. In both species, the anthesis lasted 48 h., the anther dehiscence coincided with the opening of the perianth, the stigma receptivity was higher on the second day of anthesis and nectar production reached 0.34 ml/flower. In A. vera 228±77 yellow flowers on long scapes of 76±11 cm and with 1 - 3 shafts were observed; A. saponaria had 94 ± 33 orange flowers on more compact scapes with 3-5 shafts. The pollen/ovule ratio was 4 115.2 in A. vera and 3 247.1 in A. saponaria, thus they can be classified as compulsory xenogams. Frequent visits of Apis mellifera, Trigona sp., Poliste sp., Eumenes sp., Vespa sp., Leucippus fallax and Amazilia tobaci were recorded. Although both species showed a high production of pollen and nectar, and the presence of potential pollinators, by the end of the flowering period, fruits were only observed in A. saponaria, with a 12 % reproductive efficiency. Coupled with the stigmatic receptivity results and the preliminary intra and interspecific crossing experiments, this suggests the existence of protandry and self-incompatibility as reproductive barriers reducing endogamy in these species. Rev. Biol. Trop. 56 (3): 1109-1125. Epub 2008 September 30.

Se analizó la fenología reproductiva y aspectos anatómicos florales en dos especies de Aloe conservadas en condiciones de vivero en el oriente de Venezuela, de septiembre 2001 a septiembre 2002. A. vera floreció de diciembre a mayo; A. saponaria de noviembre a agosto. En ambas especies, la antesis duró 48 h, la dehiscencia de la antera coincidió con la apertura del perianto, la receptividad del estigma fue mayor al segundo días de antesis y la producción de néctar alcanzó 0.34 ml/flor. En A. vera se observaron 228±77 flores de color amarillo sobre escapos extensos de 76±11 cm y 1-3 ejes; a diferencia de A. saponaria con 94±33 flores anaranjadas en escapos más compactos de 62±5 cm y 3-5 ejes. La relación polen/óvulo fue de 4 151.2 en A. vera y 3 247.1 en A. saponaria, clasificándose como xenógamas obligatorias. Se registraron visitas frecuentes de Apis mellifera, Trigona sp., Poliste sp., Eumenes sp., Vespa sp., Leucippus fallax y Amazilia tobaci. A pesar de que ambas especies manifestaron una elevada producción de polen, néctar y la presencia de potenciales polinizadores, al término de la floración, sólo se observaron frutos en A. saponaria, con una eficiencia reproductiva de 12%, lo cual, junto a los resultados de la receptividad estigmática y los ensayos preliminares de cruzamientos intra e interespecíficos, sugiere la existencia de protandría y autoincompatibilidad como barreras reproductivas que reducen la endogamia en estas especies.