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Breeding system and pollination of Gesneria pauciflora (Gesneriaceae), a threatened Caribbean species
... Colonies of Gesneria pauci ora appear to be associated with shaded environments (Pérez et al. 2018). Hurricane María defoliated most forests across Puerto Rico massively (Miller et al. 2019). ...
... Also, even when the number of plants detected for the species could be considered high (> 7,000 individuals), and that 11 "new" colonies were added to previous surveys, only a quarter of plants sampled were owering and capable of sexual reproduction. Even when this species is capable of some autogamy (i.e., autonomous pollination), fruit production is o en pollination limited (Pérez et al. 2018). Pollen limitation on sexual reproduction may be even stronger if these natural phenomena also a ected populations of pollinators like hummingbirds, which are the main visitor to individuals of G. pauci ora (Pérez et al. 2018). ...
... Even when this species is capable of some autogamy (i.e., autonomous pollination), fruit production is o en pollination limited (Pérez et al. 2018). Pollen limitation on sexual reproduction may be even stronger if these natural phenomena also a ected populations of pollinators like hummingbirds, which are the main visitor to individuals of G. pauci ora (Pérez et al. 2018). ...
The Caribbean was recently struck by two hurricanes (Irma and María) considered among the most powerful since 1928 in that region. !ese hurricanes brought intense and continuous rainfall, which likely impacted plants inhabiting riparian areas through flash floods and landslides. We conducted a post-hurricane assessment of Gesneria pauci!ora, an endemic riparian species of conservation concern in Puerto Rico, to determine the number of individuals of this species, their distribution and their response to the infuence of these natural phenomena across its distribution range; also, the assessment was an opportunity to survey additional sites within and outside of the Maricao Forest Reserve. A total of 79 colonies were surveyed during the study period (56 known colonies and 23 new records), yet seven of the known colonies were extirpated due to landslide or flood-driven habitat modifications. The survey yielded 7,853 plants distributed across three sub-watersheds with non-reproductive plants comprising 65.2% of the plants surveyed, followed by reproductive adults (25.3%) and seedlings (9.5%). Plants were found in a variety of habitats associated with riparian environments. Results from colonies that had pre-hurricane information suggest that plant mortality could have been as high as 89% with variation likely resulting from differences in their location within the riverine system (higher mortality for colonies in the main channel of the watershed). There was approximately an 11% reduction in estimated canopy cover at the site, and percent plant mortality showed a negative association with canopy cover after the hurricanes. While the number of individuals is higher than expected for a threatened species, the patchy distribution of its populations justifies the continuation of monitoring activities for the species at larger spatiotemporal scales to examine potential delayed responses to these hurricanes.
... Gesneria pauciflora (Gesneriaceae) is a stemmed plant with a woody basal stem; branches are erect or decumbent (Liogier, 1995), and large plants tend to form creeping mats with fragile branches. Plants produce orange, tubular flowers that are about 2 cm long and are pollinated by hummingbirds (Pérez et al., 2018). Gesneria pauciflora is a self-compatible species capable of producing fruits and seeds via autogamy (Pérez et al., 2018). ...
... Plants produce orange, tubular flowers that are about 2 cm long and are pollinated by hummingbirds (Pérez et al., 2018). Gesneria pauciflora is a self-compatible species capable of producing fruits and seeds via autogamy (Pérez et al., 2018). In the wild, individual plants produce an average of 140.3 (±26.2) healthy seeds with a germination rate in vitro estimated at 67.5% (±8.1%; ...
... Gesneria pauciflora is a self-compatible species capable of producing fruits and seeds via autogamy (Pérez et al., 2018). In the wild, individual plants produce an average of 140.3 (±26.2) healthy seeds with a germination rate in vitro estimated at 67.5% (±8.1%; Pérez et al., 2018). Even though flowering and fruiting occur throughout the year, these processes peak during the wet and dry season, respectively (M. ...
Premise:
Gesneria pauciflora is a rare, threatened plant in riparian forests. Periodic disturbances, expected in this habitat, could influence demographic dynamics on plant populations, yet their impact may not be the same across the watershed. We hypothesized that differences in disturbances between the main channel and tributaries may lead to spatial dissimilarities in population growth rate (λ), structure, and fecundity.
Methods:
In the Maricao River Watershed in Puerto Rico, 1277 plants were tagged and monitored for 1.5 years. Every 6 months, we measured plant size and recorded survival, fecundity, and appearance of seedlings. These variables were used in integral projection models to assess the population status of G. pauciflora.
Results:
Plants in the main channel were smaller but more likely to flower and fruit than those in the tributaries. Overall mortality was greater in the main channel and greater during the rainy season. At both sites, λ ranged from 0.9114 to 0.9865, and survival/growth of larger plants had a greater effect on λ (>0.90) regardless of site.
Conclusions:
Values for population growth rates suggest that G. pauciflora is declining across the watershed. Higher mortality rates in the main channel (more-perturbed sites) might drive G. pauciflora to reproduce at smaller sizes, while tributaries (less-perturbed sites) might be better for growth and lead to larger plant sizes. Extreme climatic events are expected to increase in the Caribbean and might decrease the population if the population is left unmanaged. Management strategies that reduce the time plants require to reach larger sizes might be necessary to increase λ, and reintroduction using cuttings might be a possible solution.
... The assessment of breeding systems of rare or endemic species may be critical for the development of successful conservation strategies (Pérez & al. 2018). Since mixed mating systems may reduce species vulnerability (Yates 8 Anales del Jardín Botánico de Madrid 79 (2): e131. ...
The breeding system of Anacyclus linearilobus, an annual and endemic species restricted to dune ecosystems of the Algerian coast were assessed through the effect of self-fertilization and intra- and inter-population artificial crosses on the probability of producing viable seeds in 20 individuals from two populations in a common garden. The breeding system was determined for each individual by the self-incompatibility index (ISI). These results were compared with those published for other species of the genus, A. clavatus, A. homogamos and A. valentinus. Results of experimental crosses showed that there was high variation in the female reproductive success between individuals of A. linearilobus, like that found in its sister species, A. valentinus. Unlike the other species in the genus that are self-incompatible, A. linearilobus showed a mixed mating system, with a majority of self-incompatible individuals, others partially self-incompatible and some self-compatible. We argue that this strategy may be related to reproductive assurance in this endemic, annual species whose effective population size has been reduced probably due to individual mating incompatibilities.
... The assessment of breeding systems of rare or endemic species may be critical for the development of successful conservation strategies (Pérez & al. 2018). Since mixed mating systems may reduce species vulnerability (Yates 8 Anales del Jardín Botánico de Madrid 79 (2): e131. ...
The breeding system of Anacyclus linearilobus, an annual and endemic species restricted to dune ecosystems of the Algerian coast were assessed through the effect of self-fertilization and intra- and inter-population artificial crosses on the probability of producing viable seeds in 20 individuals from two populations in a common garden. The breeding system was determined for each individual by the self-incompatibility index (ISI). These results were compared with those published for other species of the genus, A. clavatus, A. homogamos and A. valentinus. Results of experimental crosses showed that there was high variation in the female reproductive success between individuals of A. linearilobus, like that found in its sister species, A. valentinus. Unlike the other species in the genus that are self-incompatible, A. linearilobus showed a mixed mating system, with a majority of self-incompatible individuals, others partially self-incompatible and some self-compatible. We argue that this strategy may be related to reproductive assurance in this endemic, annual species whose effective population size has been reduced probably due to individual mating incompatibilities.
... These natural events may lower dramatically the abundance of local pollinators and create periods of low pollinator availability and thus lead to pollenlimitation conditions (Wunderle 1995;Rathcke 2000Rathcke , 2001Rivera Marchand & Ackerman 2006;Rojas Sandoval & Meléndez-Ackerman 2011). Conditions of low pollinator abundance may favour and select for self-compatibility as a mechanism of reproductive assurance which may be advantageous in these unstable environments and depauperate pollinators communities that are Caribbean islands (Martén-Rodriguez & Fenster 2008;Martén-Rodríguez et al. 2010;Pérez et al. 2018). ...
Insular pollination systems are more extinction-prone and vulnerable to invasive species than mainland ones. They often have plants with reproductive mechanisms allowing for self-compatibility and low species-rich communities of pollinators. Here, we document different reproductive traits of the tropical tree Guaiacum sanctum on two insular populations with contrasting pollinator assemblages: Guánica in Puerto Rico with alien honeybees and Mona Island where honeybees do not occur. Using field observations and pollination experiments, we evaluated pollinator species richness, visitation rates, breeding system, and the fitness of selfed- vs. crossed-progenies. We found that flowers are pollinated by insects on both islands, but while the species richness of pollinators was higher on Mona, the visitation rates were considerably higher in Guánica where trees are almost exclusively visited by the introduced Apis mellifera. Flowers are not apomictic, and autogamy is negligible indicating that pollinators are required to set fruits. Outcrossing yielded nearly twice the number of fruits and seeds than selfing and these differences were consistent between populations, which might reflect early acting inbreeding depression, partial self-incompatibility, or differences in resource allocation between selfed and outcrossed fruits. Our combined results suggest that the substantial reduction in pollinator visitors in areas dominated by A. mellifera may add an additional level of vulnerability to these threatened populations. Although reproductive fitness is higher in Guánica, mostly due to the pollination services provided by A. mellifera, this population may be more susceptible to environmental changes and large-scale disturbances affecting pollinator abundance given the reduced diversity of flower visitors.
... The majority of insects visiting the M. indica cultivars are native to the Caribbean region and probably have, through their evolutionary history, developed adaptations that could make them highly resilient to these systems regardless of taxa. Second, the effects of hurricane-related changes in pollinator faunas on plant reproduction (regardless of the plant system) may depend whether or not pollination systems are generalized or specialized (Dalsgaard et al., 2009) or whether or not plant species have alternative mechanisms of plant reproductive assurance (Jones et al., 2001;Rivera-Marchand and Ackerman, 2006;Pérez et al., 2018). While most cultivars of M. indica depend on animal pollination to set fruit (Anderson et al., 1982;De Siqueira et al., 2008;Fajardo et al., 2008;Corredor and García, 2011;Kumar et al., 2012), it is apparent that globally mangos have a highly generalized pollination system, a condition that is likely favorable where extreme weather events are common such as in the Caribbean. ...
Mangifera indica is a widespread economically important tropical fruit. An ongoing study at the Juana Diaz Experimental Station in Puerto Rico aims to understand the factors that influence local pollination success and fruit yields in four fields each hosting a different mango cultivar (Keitt, Kent, Tommy Atkins, and Julie) at different temporal scales. Here we describe the results of insect collection campaigns that evaluated flower visitor communities of these fields (from January to April) in the seasons of 2017 (before Hurricane Maria), 2018 (after Hurricane Maria) and 2019 (2 years after Hurricane Maria). We expected a reduction in diversity, abundance and yields and even changes in composition following the hurricane events of 2017. Over the 3 years, plants were visited by a combined total of 50 insect species, mostly Diptera (also the most abundant), Hymenoptera, Coleoptera, and Lepidoptera. The relative abundances of insect communities changed but overall species richness of insect communities appeared to be recovering by 2019. A clear decline in overall crop yields for two of the four fields (hosting Kent and Tommy Atkins) was seen in 2018 but then recovered in one and surpassed pre-hurricane levels in another in 2019. Mango trees experienced an increase in the abundance for all insect groups in 2019 following the 2018 decline and only one field (hosting Kent) experienced significant species richness declines in 2018. Two of the most dominant insects, Palpada vinetorum (Diptera) and Apis mellifera (Hymenoptera), showed a “reduction-recovery” pattern for the period of 2018–2019 but not so for Cochliomyia minina which was very abundant in 2018 in three out of four cultivars but then returned to pre-hurricane levels in 2019. In 2017, the trees exposed to higher richness and abundance of species experienced higher yields regardless of cultivars but these relationships when present were often weaker in 2018 (post-hurricane) and 2019 and not all cultivars were equally successful at attracting the same levels of diversity and abundance of insects. Our results do support the importance of pollinator diversity and abundance to improve agricultural yields. They also emphasize that within the context of future extreme atmospheric events, that there needs to be an understanding of not only how these pollinator communities may recover from these events but also of how individual pollinators (vs. other factors) may influence plant yields to develop informed management strategies following such events.
... Plant traits that directly determine the means by which a plant produces seeds (i.e., the modes of reproduction) constitute its breeding system (Neal and Anderson, 2005;Barrett, 2014). For threatened and rare plants, breeding system studies are an essential first step to identify factors that reduce seed production (Johnson and Steiner, 2000;Davidson et al., 2014;Pérez et al., 2018), particularly for species living in harsh environments, where pollinators are scarce or their abundance variable (Castro et al., 2008). Moreover, knowledge of the breeding system of threatened plants can allow managers to infer how changes in the pollinator environment may affect their reproductive output (Larson and Barrett, 2000;Young et al., 2012), their risk of inbreeding depression (Bellanger et al., 2015) and ultimately, their population viability (Richardson et al., 2016). ...
Many plants can produce seeds via multiple reproductive modes, such as selfing and outcrossing. Having multiple reproductive modes can be advantageous if it assures seed production when outcrossing fails, which is important for species inhabiting environments where pollinators are scarce or variable. However, it can also be disadvantageous due to the fitness costs associated to selfing. Consequently, plants have mechanisms to reduce the incidence of selfing. Here we examined the breeding system of Myrcianthes coquimbensis; this threatened Atacama Desert shrub is the last species to bloom in the community and exhibits low visitation rates per flower because pollinators are less abundant. Our aim was to determine whether this plant can produce fruits by modes other than outcrossing, and whether it possesses floral traits to prevent sexual interference. We conducted experimental flower treatments in two localities to determine whether fruits were produced by outcrossing, selfing, autonomous selfing and agamospermy. We also evaluated stigma receptivity and pollen viability during a flower’s lifespan. M. coquimbensis developed fruits and seeds by all the reproductive modes assessed, including selfing and agamospermy. Flowers presented partial segregation of sexual functions, with the peak of pollen viability occurring before the peak of stigma receptivity. Selfing is unavoidable in M. coquimbensis and likely interferes with outcrossing. Coupled with possible early inbreeding depression, it probably results in a cost for seed production. Our results suggest that this species may be vulnerable in scenarios where pollinators are scarce; however, agamospermy may provide an alternative route of seed production in these scenarios.
... Though our most-sampled bird was the generally nectarivorous bananaquit, two lines of evidence suggest that bananaquits in LEF rely considerably on animal food sources and thus their low blood Hg is not solely a reflection of low trophic position. LEF is frequently impacted by tropical cyclones, which limit energetically expensive Fig. 4 a Bird blood Hg concentration in 31 birds sampled in Luquillo Experimental Forest; b relation of bird blood Hg concentration to δ 15 N in these samples nectar production, as was found at similar elevations in other Puerto Rican forests (Ackerman et al. 1994;Meléndez-Ackerman et al. 2000;Pérez et al. 2011). In Jamaica's Blue Mountains at a similar elevation to our study, Cruz (1980) found that invertebrates constituted 24% of the bananaquit diet. ...
At a “clean air” trade winds site in northeastern Puerto Rico, we found an apparent paradox: atmospheric total mercury (THg) deposition was highest of any site in the USA Mercury Deposition Network, but assimilation into the local food web was quite low. Avian blood THg concentrations (n = 31, from eight species in five foraging guilds) ranged widely from 0.2 to 32 ng g⁻¹ (median of 4.3 ng g⁻¹). Within this population, THg was significantly greater at a low-elevation site near a wetland compared to an upland montane site, even when the comparison was limited to a single species. Overall, however, THg concentrations were approximately an order of magnitude lower than comparable populations in the continental U.S. In surface soil and sediment, potential rates of demethylation were 3 to 9-fold greater than those for Hg(II)-methylation (based on six radiotracer amendment incubations), but rates of change of ambient MeHg pools showed a slight net positive Hg(II)-methylation. Thus, the resolution of the paradox is that MeHg degradation approximately keeps pace with MeHg production in this landscape. Further, any net production of MeHg is subject to frequent flushing by high rainfall on chronically wet soils. The interplay of these microbial processes and hydrology appears to shield the local food web from adverse effects of high atmospheric mercury loading. This scenario may play out in other humid tropical ecosystems as well, but it is difficult to evaluate because coordinated studies of Hg deposition, methylation, and trophic uptake have not been conducted at other tropical sites.
Comparettia falcata is an epiphytic, neotropical orchid that produces nectar as a pollinator reward. In Puerto Rico, C. falcata is allogamous and pollinated by the endemic hummingbird Chlorostilbon maugaeus. Autogamous pollinations are possible, but may result in reduced fruit set. For the 1989 and 1990 flowering seasons, the probability of pollinarium removals and natural pollinations increased with individual inflorescence display size. However, the frequency of effective pollinator visits was independent of flowering phenology in both years. A positive correlation between inflorescence size and reproductive success occurred in 1990 but not in 1989. In 1990 plants produced longer spurs, a higher standing crop of nectar, and a more concentrated nectar than in 1989. There was no relation between nectar availability (= standing crop of nectar) and sugar concentration in either year. Nectar availability and sugar concentration did not vary among the first four flowers of an inflorescence in either season. Nectar availability was not a good predictor of effective visitation. Comparettia falcata has a higher natural fruit set than tropical deceptive orchids, suggesting that pollinator visitation may be enhanced by nectar reward. The small, dilute nectar volumes secreted by C. falcata may benefit the plant by increasing interplant pollinator movement and pollen dispersal.
Planted meadows are increasingly used to improve the biodiversity and aesthetic amenity value of urban areas. Although many 'pollinator-friendly' seed mixes are available, the floral resources these provide to flower-visiting insects, and how these change through time, are largely unknown. Such data are necessary to compare the resources provided by alternative meadow seed mixes to each other and to other flowering habitats. We used quantitative surveys of over 2 million flowers to estimate the nectar and pollen resources offered by two exemplar commercial seed mixes (one annual, one perennial) and associated weeds grown as 300m 2 meadows across four UK cities, sampled at six time points between May and September 2013. Nectar sugar and pollen rewards per flower varied widely across 65 species surveyed, with native British weed species (including dandelion, Taraxacum agg.) contributing the top five nectar producers and two of the top ten pollen producers. Seed mix species yielding the highest rewards per flower included Leontodon hispidus, Centaurea cyanus and C. nigra for nectar, and Papaver rhoeas, Eschscholzia californica and Malva moschata for pollen. Perennial meadows produced up to 20x more nectar and up to 6x more pollen than annual meadows, which in turn produced far more than amenity grassland controls. Perennial meadows produced resources earlier in the year than annual meadows, but both seed mixes delivered very low resource levels early in the year and these were provided almost entirely by native weeds. Pollen volume per flower is well predicted statistically by floral morphology, and nectar sugar mass and pollen volume per unit area are correlated PLOS ONE |
The evolution of self‐pollination has long been considered an adaptive strategy to cope with low or variable pollinator service; however, alternative reproductive strategies, such as generalized pollination (>1 pollinator functional group), may also ensure plant reproductive success in environments with inadequate pollinator visitation.
Island–mainland systems provide ideal settings to assess the interaction between pollination and breeding systems in response to pollinator visitation because islands are often pollinator‐depauperate. This study compared 28 insular and 26 mainland species of C aribbean G esneriaceae to test the hypothesis that low diversity and possibly low pollinator service on islands would lead to a greater frequency of generalized plant–pollinator interactions and/or a higher potential for autonomous self‐pollination in insular than in mainland species. We also assessed the hypothesis that epiphytic species should have greater autofertility than species occurring in other habitats.
Pollinator observations conducted in the field from 2004 to 2014 revealed bat, bee, butterfly, hummingbird, moth, and generalized pollination systems. Functional specialization in pollination systems was high in insular (71% of the species) and mainland sites (all species), but generalized and bat‐pollinated species were more common on islands. Overall, pollinator visitation rates did not differ between island and mainland; however, for hummingbird‐pollinated species, visitation rate was on average three times higher in mainland than island species. Autofertility indices (fruit set of bagged/outcross flowers) ranged from 0 to 1 and did not differ between island and mainland species. Species growing on rocks (rupiculous) and trees (epiphytic) had on average higher autofertility than terrestrial species.
Synthesis . This study revealed that alternative reproductive strategies are used in pollinator‐depauperate environments. Pollinator visitation is lower in insular hummingbird‐pollinated species (the ancestral pollination system of insular G esneriaceae); therefore, generalized pollination may be considered a reproductive assurance mechanism evolved primarily on island environments. Contrary to the long‐standing tenet, however, autonomous self‐pollination was similar in island and mainland G esneriaceae suggesting that: (i) generalized pollination provides a viable alternative to selfing in pollinator‐depauperate environments, (ii) autofertility as a reproductive assurance mechanism may be frequent in plant species from mainland regions in environments with unpredictable pollinator visitation and resource availability.
Bird populations in a subtropical wet forest were monitored every two to three weeks with mist nets and point counts beginning two weeks after the passage of Hurricane Hugo in September 1989. The results were compared with those of a pre-hurricane study in the same locations in which birds were sampled in forest understory and openings. Capture rates were initially higher than in the previous study, due to displaced canopy dwellers foraging in the understory. The shift of canopy dwellers may have obscured expected declines in nectarivores and fruit/seedeaters and contributed to increased detections of omnivores and insectivores. Bird captures and fruit production peaked 93-156 days after the storm in pre-existing gaps, where higher capture rates and a distinct assemblage of birds occurred in contrast to sites without fruit (forest understory and a powerline opening). Captures in pre-existing gaps decreased as fruit production ceased, and overall captures declined to baseline levels after 198 days. After one year of recovery, new gaps and forest understory became distinguishable on the basis of their unique foliage profiles. Although different bird assem-blages had been found in forest understory and in gaps prior to the hurricane, these assem-blages lost their distinctiveness after the storm. It may take many years after a hurricane for forest understory and gaps to become sufficiently distinct in structure and resources before birds differentiate between the two habitats.
Observations of the life history of a plume moth, Postplatyptilia caribica Gielis are presented along with an adult diagnosis and descriptions of the final instar larva and pupa. The species was previously known only from two female specimens. Illustrations are provided for the adults and immatures, including both male and female genitalia. Morphological characters of the adults and immatures are discussed and compared with other members of the tribe Platyptiliini. Identification of adults and immatures is especially important because one of the larval hostplants, Gesneria pauciflora Urb., is a threatened endemic species of Puerto Rico. The plant family Gesneriaceae is a new addition to the known plant families used by Pterophoridae.
Plant defense against herbivores may compromise attraction of mutualists, yet information remains limited about the mechanisms underlying such signaling tradeoffs.
Here, we investigated the effects of foliar herbivory by two herbivore species on defense compounds, floral signaling, pollinator and parasitoid attraction, and seed production.
Herbivory generally reduced the quantity of many floral volatile organic compounds VOC s) in B rassica rapa . By contrast, floral color, flower diameter, and plant height remained unaffected. The decreased amounts of floral volatiles led to reduced attractiveness of flowers to pollinators, but increased the attractiveness of herbivore‐infested plants to parasitoids. Plants infested with the native butterfly P ieris brassicae produced more flowers during early flowering, effectively compensating for the lower olfactory attractiveness. Herbivory by the invasive S podoptera littoralis increased the amounts of glucobrassicanapin, and led to delayed flowering. These plants tended to attract fewer pollinators and to produce fewer seeds.
Our study indicates a tradeoff between pollinator attraction and indirect defense (parasitoid attraction), which can be mitigated by reduced floral VOC emission and production of more early flowers. We suggest that this compensatory mechanism is specific to plant–herbivore associations with a coevolutionary history.
Flowers with highly specialized pollination systems sometimes have the ability to self-pollinate, contradicting our notion that pollination specialization reflects selective pressures to ensure high maternal outcrossing rates. We survey the literature (80 species representing 38 families) for the simultaneous study of pollination and breeding systems. We demonstrate that pollination specialization is often associated with a variety of floral traits that facilitate delayed autonomous selfing at the end of the flower's life span. While the potential autonomous selfing rate can be high, the actual autonomous selfing rate is often much lower, indicating that species in our survey are facultative selfers. Autonomous selfing was more commonly associated with protandry than with protogyny and was found in both herkogamous and nonherkogamous species. We conclude that pollination specialization can evolve independently of the ability to autonomously self-pollinate and that the presence of floral traits that promote pollination specialization and autonomous selfing in the same flower is not paradoxical. Pollination specialization can be reconciled with autonomous self-pollination when selective forces other than high maternal outcrossing rates are considered. The whole case is perplexing in an unparalleled degree for we have in the same flower elaborate contrivances for directly opposed objects. (C. Darwin 1877, p. 57)
Using experimental manipulations, we examined pollen and resource limitations to seed production and their interaction in a natural population of a monocarpic plant, Ipomopsis aggregata. Our design crossed two factors, pollen level (hand-pollinated or control) and resource level (water added, water and fertilizer added, or control). Both hand-pollination and fertilizing during the blooming season increased total seed production, while watering alone had no effect on any component of reproductive success. Hand-pollination boosted number of seeds per flower, with no effect on flower number. In contrast, fertilizing had its primary effect on the number of flowers produced, while also increasing the number Of seeds per mature fruit in hand-pollinated plants. Fertilizing increased nectar volume, but path analysis detected no indirect effect of this increased reward rate on seed production, suggesting instead that fertilizing had a slight, but direct, effect on seeds per flower. These results argue against a strict dichotomy between pollen limitation and resource limitation of female reproductive success in plants.
* Many flowering plant species have a facultative or obligate dependence on insect pollination for reproductive success. Anthropogenic disturbance may alter these species interactions, but the extent to which structural changes to plant-pollinator networks affect plant species mating systems is not well understood. * We used long-term livestock grazing of a birch wood ecosystem to test whether disturbance of this semi-natural habitat altered floral resources, the structure of plant-insect visitation networks and the mating system of a focal plant species, Cirsium palustre. * Grazed habitat had a higher species richness of floral resources for pollinators. Visitation networks in grazed habitats were larger, more diverse, with an increase in the number of pollinators per plant species. Controlling for sampling effects, however, showed networks in grazed habitats were less nested and revealed a positive correlation between network connectance and floral species richness. * Network connectance was negatively related to C. palustre outcrossing rate within grazed and ungrazed sites. However, on average the effects of grazing, including greater mean connectance, produced higher overall outcrossing rates and more pollen donors compared with ungrazed habitat. The number of different pollen donors, spatial genetic structure and mating among close relatives were all correlated with greater extent of suitable C. palustre habitat in the landscape, consistent with the effects of increasing plant population size but limited seed dispersal. * Pre-adaptation of C. palustre to disturbance coupled with a preponderance of highly dispersive flies attracted to the greater food resources in grazed habitat are likely mechanisms underpinning this increased pollen transport. * Habitat modification by long-term mammalian grazing fundamentally shifted visitation network structure and the state of a plant mating system, indicating how ecosystem disturbance can cascade across levels of biological organisation through altered interspecific interactions. Cirsium palustre retains flexibility to bias reproduction toward selfing where pollen donor diversity is limited; such reproductive flexibility may be an important mechanism structuring plant populations in human-modified landscapes.
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The Pterophoridae (Ochyroticinae, Deuterocopinae, Pterophorinae (Tribus: Platyptiliini, Exelastini, Oxyptilini)) species of the Neotropical fauna are reviewed. The species are redescribed. Moths are illustrated in colour for the first time, their genitalia are illustrated in line drawings. The examination of type specimens revealed the presence of four new synonyms: Platyptilia juanvinas Gielis, 1999, is a junior synonym of Platyptilia gravior Meyrick, 1932; Platyptilia jonesi Gielis, 1996, is a junior synonym of Platyptilia semnopis Meyrick, 1931; Oxyptilus maleficus Meyrick, 1926, is a junior synonym of Leptodeuterocopus neales (Walsingham, 1915); Lioptilus parvus Walsingham, 1880, is a junior synonym of Lioptilodes albistriolatus (Zeller, 1871). During the study of much new material 40 new species were discovered: Leptodeuterocopus tungurahue, L. angulatus, L. panamaensis, L. duchicela, Sochchora mulinus, Melanoptilia nigra, Platyptilia spicula, Stenoptilodes maculatus, S. agricultura, S. heppneri, S. medius, S. altiaustralis, Postplatyptilia nebuloarbustum, P. antillae, P. caribica, P. uruguayensis, P. pluvia, P. seitetazas, P. transversus, P. carchi, P. boletus, P, ugartei, P. drechseli, P. corticis, P. zongoensis, P. vorbecki, Amblyptilia landryi, A. kosteri, Lioptilodes altivolans, L. arequipa, L. yungas, L. salarius, L. cocodrilo, Michaelophorus margaritae, M. bahiaensis, Geina integumentum, Capperia browni, Buckleria brasilia, Megalorhipida paraiso, M. dubiosa. In the larger genera the species are arranged in groups. For a distinct group of species a new genus: Melanoptilia is proposed. A comprehensive checklist of the species has been made. To facilitate identification a key is presented to the genus level.
Hurricane Georges crossed the island of Puerto Rico on 21-22 September 1998. Maricao State Forest, a montane reserve in southwestern Puerto Rico, was struck by Georges after being spared by hurri- canes since 1932. I documented the changes in relative abundance of Maricao resident bird species caused by the impact of the hurricane by comparing baseline mist netting capture rates with data 33 days after the hurricane, and point counts records with data up to 22 months after Georges. Total capture rates increased after the storm (26.8 individuals/net hr pre-hurricane vs. 57.9 individuals/net hr post-hurricane). Capture rates classified according to foraging guilds did not differ, but showed significant increases according to foraging level (canopy vs. understory). Increases in capture rates were related to the displacement of birds into lower forest strata after canopy loss. While most species recorded in point counts declined after Georges (16/21), only the relative abundance of six species differed significantly among years. Just one species (Elfin Woods Warbler, Dendroica angelae) recovered by the end of the study. Two species were not observed after the hurricane, including one of the five most abundant (Ruddy Quail-Dove, Geotrygon montana) and a new species was observed in the study area after the hurricane (White-winged Dove, Zenaida asiatica). Only the population of the Gray Kingbird (Tyrannus dominicensis) remained unchanged throughout the study. Results demonstrated that even common species in montane habitats can be highly susceptible to hurricanes, and thus, long-term monitoring of avian communities at different elevations is needed to understand the effects.
Fruit production in interoparous flowering plants can be limited by a variety of conditions that need not be mutually exclusive nor immediately evident. We examined short- and long-term constraints to fruit production in a Puerto Rican population of the infrequently pollinated orchid Epidendrum ciliare. Average natural fruit maturation rate ranged from 5 to 15% over 4 yr. To evaluate limitations to fruit production, pollinations were augmented for a randomly chosen experimental portion of a population for two consecutive years. During this period, only 10 and 15% of flowers on control plants were naturally pollinated. Hand-pollinations of nearly all flowers produced by experimental plants increased fruit production to 33 and 49%, compared to 5 and 8% for controls. Thus, fruit production within seasons was partially limited by pollinations. Fruit predation also was heavy for both control (28 and 29% of fruits initiated) and pollinations-augmented (20 and 32%) groups. No clear relationship existed between treatment and predation frequency. Furthermore, undamaged fruits often aborted (controls 11 and 37%, experimentals 15 and 28%), but frequencies were independent of self vs. outcrossed pollination and treatment. Seed crop mass declined as fruit set increased, suggesting that resources were limited. Long-term effects of heavy fruit loads were evident. Over 2 yr, the number of inflorescences, flowers, and flowers per inflorescence declined for experimentals relative to the controls. Moreover, plant size and vegetative proliferation decreased for experimentals relative to controls. Thus, through elevated fruit production the plant incurs future cost and lifetime fitness of E. ciliare might be more affected by resource constraints than by the other factors studied.
In Puerto Rico, Comparettia falcata, a hummingbird-pollinated epiphytic orchid, produces an average one-time secretion of 3.3-4.0 μl of nectar (12.9-15.1% sugar) per flower. In contrast, nectar sugar concentrations of other hummingbird flowers on Caribbean islands are 17-37% and those of Puerto Rico visited by the C. falcata pollinator have standing crops averaging 2.0-6.2 μl and daily secretion rates of 3.1-10.6 μl. In the Toro Negro Forest Reserve, in 1991, the authors clipped the spur tips of all flowers at one site rendering them nectarless. Visitation frequencies and measures of male and female fitness were adjusted for site differences in pollinator activity, and all were significantly lower at the site where flowers were nectarless. In 1992, the authors abandoned one site and manipulated the other by clipping the floral spurs of a randomly chosen subset of plants so that 25% of the flowers in the population were nectarless. Pollinarium removals from intact flowers were significantly different from those with cut spurs and total visits were nearly significant as well. However, the difference in female success was not significant between the two treatments. Number of visits per flower dropped dramatically from previous years despite the highest level of bird activity yet censused. Data are consistent with the hypothesis that the pollinator (Puerto Rican emerald Chlorostilbon maugaeus) perceives the nectar reward despite its small quantity and low sugar content, this to the advantage of Comparettia flacata. -from Authors
The pink, tubular, nectariferous flowers of Melocactus intortus (Cactaceae) in Puerto Rico are visited by native hummingbirds (Anthracothorax dominicus), but also by invasive honeybees (Apis mellifera) and ants (Solenopsis sp.). We sought to determine if the bees and ants significantly alter the pollination of M. intortus by measuring pollinator effec-tiveness. Using traditional estimates of effectiveness (visitation rate and seed set), our results show that hummingbirds were the most effective pollinators as expected. Bees and ants were less effective, and their contributions were one-fourth to one-tenth of that observed for hummingbirds. We then modified this measure of effectiveness by adding two components, fitness of progeny and temporal availability of visitors, both of which refine estimates of flower visitor effectiveness. With these new estimations, we found that the effectiveness values of all three animal visitors decreased; however, the role of hummingbirds as the principal pollinator was maintained, whereas the effectiveness values of bees and ants approached zero. By these new measures of overall pollinator effectiveness, the invasive honeybees and ants have little effect on the reproductive success of M. intortus.
Unlabelled:
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Premise of the study:
Climate change threatens to alter the timing and magnitude of abiotic cues that synchronize mast flowering, such as temperature and precipitation. Climate change may therefore alter the frequency of masting, in turn affecting species in the community that use pulsed resources. •
Methods:
We used 29-yr (1984-2012) records of climate and flowering to investigate proximate flowering cues for the clonal, mast-flowering herb Veratrum tenuipetalum. Because clonal reproduction is tied to flowering in Veratrum, we used a parallel record of ramet abundance to examine the effects of masting on long-term ramet abundance. •
Key results:
Cool summer temperatures 2 years before flowering were associated with a higher percentage of flowering in Veratrum populations, consistent with its life history. Ramet abundance increased by 9.5% ± 5.6% on average following mast years compared to an average loss of 0.73% ± 1.1% in nonmast years, and ramet abundance increased over the time frame of our records. •
Conclusions:
Ramet abundance has increased over the time frame of our records mainly because of clonal reproduction in masting years. If summer temperatures continue to increase at our site and Veratrum does not alter its climate thresholds, we predict that masting will become less frequent in this species, with consequent reduction in opportunities for both sexual and clonal reproduction.
Experimental hand pollinations have revealed that the Australian proteaceous shrub Grevillea barklyana is fully self-compatible, although one study suggested that when both self- and outcross pollen were presented to different flowers on the same inflorescence significantly greater seed set resulted from the outcrossed flowers. This study used single-locus electrophoretic surveys of maternal plants and their progeny arrays to test the prediction that this apparent 'preference' for outcross pollen would produce high levels of outcrossing within natural populations. We found instead that plants within three of four populations were almost completely selfed. Outcrossing rates (t) in each of these populations (based on the progeny arrays of a minimum of nine plants) ranged from 0.07 0.03 to only 0.33 0.08 and showed little variation among years, ranging from 0.07 0.03 to 0.10 0.03 for a population sampled in each of two breeding seasons. Furthermore, examination of the progeny arrays from plants in the most intensively studied population revealed virtually no exchange of genes between immediately adjacent plants. Three pairs of alternative homozygotes were near neighbours (separated by less than 2 m) and yet detectable outcrosses comprised only seven of the 108 seeds sampled. In contrast, the fourth population of G. barklyana appeared highly outcrossed (t = 0.85 0.2) which is typical of the realized mating system reported for other Australian Proteaceae. These data show that the realized mating system may vary widely among populations and may often be less than optimal. The occurrence of very low outcrossing rates within some populations may reflect the presence of introduced pollinators or other disturbances.Keywords: inbreeding, mate choice, mating system, pollination, selfing
Generalized pollination systems may be advantageous on island systems or regions of substantial disturbance. We examined whether or not specialization breakdown has occurred in a presumably bat-pollinated columnar cactus, Pilosocereus royenii, on Puerto Rico, an island subjected to periodic hurricanes. The flowers show characteristics related to bat pollination including nocturnal anthesis, morphology, and amount and quality of nectar reward. The cactus produces flowers whose styles are temporally and mechanically separated from its anthers and do not self-pollinate. Hand manipulations indicated that it is partially self-incompatible or suffers some inbreeding depression. In 217 h of observations conducted biweekly over the course of 1 yr, P. royenii received visits from bats, moths, bees, and birds, but the only effective pollinator was the carpenter bee, Xylocopa mordax. Only four bat visits were recorded, all prior to stigma receptiveness. Floral morphology of P. royenii was significantly more variable than that of other bat-pollinated species of the genus. We propose that infrequent bat visits are a consequence of a population crash and that floral variability is due to either relaxed selection for bat pollination or a transitional stage from bat pollination to bee pollination.
Quantifying the extent to which seed production is limited by the avail-ability of pollen has been an area of intensive empirical study over the past few decades. Whereas theory predicts that pollen augmentation should not increase seed production, numerous empirical studies report significant and strong pollen limitation. Here, we use a variety of approaches to examine the correlates of pollen limitation in an effort to understand its occurrence and importance in plant evolutionary ecology. In particular, we examine the role of recent ecological perturbations in influencing pollen limita-tion and discuss the relation between pollen limitation and plant traits. We find that the magnitude of pollen limitation observed in natural populations depends on both historical constraints and contemporary ecological factors.
Current views about the predominance of generalization of pollination systems have stimulated controversy concerning the validity of pollination syndromes. In order to assess the extent to which floral characters reflect selection by the most important pollinators we evaluated pollination syndromes in a florally diverse plant group, the tribe Gesnerieae, a monophyletic plant radiation from the Antillean islands.
The study species include representatives of three groups of floral phenotypes, two of which chiefly correspond to ornithophilous and chiropterophilous syndromes. The third group includes subcampanulate flowers (characterized by a corolla constriction above the nectar chamber) with combinations of traits not fitting classic pollination syndromes.
Pollination systems were characterized for 19 Gesnerieae species in five Antillean islands between 2003 and 2007 and supplemented with observations of four Gesneriaceae species from Costa Rica. Pollinator visitation and frequency of contact with anthers or stigmas were used to calculate an index of pollinator importance. Eleven floral traits including morphology, phenology and rewards were used to assess clustering patterns in phenotype space.
Multidimensional scaling analysis of floral traits resulted in two clusters comprising: (i) tubular, red to yellow‐flowered species with diurnal anthesis, (ii) bell‐shaped‐flowered species; two groups of floral phenotypes were evident within the latter cluster, campanulate nocturnal and subcampanulate flowers. Correlations between pollinator importance values and floral axes revealed strong associations with the expected pollinators, hummingbirds for tubular flowers, and bats for campanulate flowers; subcampanulate‐flowered species had generalized pollination systems including bats, hummingbirds and insects. Discriminant analysis of the multivariate set of floral traits correctly classified 19 out of 23 species into the predicted pollination categories.
Synthesis . This study provides support for classic hummingbird and bat pollination syndromes, demonstrating the importance of pollinator‐mediated selection in the floral diversification of Antillean Gesnerieae. However, there was evidence for generalized pollination systems in species characterized by a unique morphological trait (corolla constriction), but with variable combinations of other floral traits. These findings suggests that floral phenotypes might also evolve under selection by various functional groups of pollinators, and underscores the importance of considering the presence and effectiveness of all floral visitors in pollination studies.
Polygala vayredae is a narrow endemic species from the oriental pre-Pyrenees. Despite its conservation status and rarity, no information is available on its reproductive biology. As the flower is the structure directly involved in pollinator attraction, its morphological and functional traits have major effects on the reproductive success of the plant. In this work, the flower biology and breeding system of P. vayredae were studied to evaluate how they affect the reproductive outcome in natural populations. Flower morphology, flower rewards, and male and female functioning throughout the lifespan of the flower were assessed. Pollination experiments, involving pollinator exclusion and pollen from different sources, were conducted, and the pollen ovule index was determined. Female fitness and the occurrence of pollen limitation were assessed in three natural populations over 2 years by observing the presence of pollen on the stigma, pollen tube development, and fruit production. Polygala vayredae flowers are elaborate and long-lived with nectar rewards. The floral traits are well adapted to xenogamy and entomophily, which are in accordance with the observed breeding system and auto-incompatibility system. No mechanism of reproductive assurance was observed and P. vayredae strictly depends on pollinators to set fruit. Low fruit production was observed in the studied populations, which was largely the result of scarce, unreliable, and/or inefficient pollinators and poor pollen quality. In addition, available resources may be a limiting factor. The reproductive strategy of P. vayredae prevents inbreeding depression by a self-incompatibility system, which in years of scarce pollinators is overcome by the plant habit. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157, 67–81.
Aim This research investigates changes in orchid species composition and diversity, plant breeding system and floral traits along an elevational gradient spanning 2300 m (200–2500 m).
Location The study was conducted on Réunion Island (Mascarene Islands, Indian Ocean).
Methods Data on the distribution of 135 orchid species from 35 genera were gathered from 121 localities situated between 200 and 2500 m a.s.l. For each locality, 500-m transects were walked and each orchid species was recorded. Measures of species diversity (species richness, a modified Shannon diversity index and the modified Shannon equitability index) were related to altitude using ordinary least-squares regression. Species turnover and elevational gradients in species composition were determined by: (1) relating scores of detrended correspondence analysis to altitude using ordinary least-squares regression, and (2) relating Sørensen similarity indices to differences in altitude using Mantel tests. Finally, the average proportion of species displaying similar floral traits or showing the same breeding system were compared among altitudinal zones.
Results Species richness per transect ranged from 1 to 36 species (mean 14.3) and decreased significantly with increasing altitude. Similarly, species evenness decreased significantly with increasing altitude. Around 50% of all orchid species were rare (occurred in fewer than 5% of all localities), and only a few occurred in more than 50% of all localities. Orchid species composition changed continuously with altitude, indicating turnover of species with increasing altitude. Analogously, orchid breeding systems and floral traits also changed with altitude. Relatively more auto-pollinating species were found at high altitudes compared with mid- and low-altitude sites where animal-pollinated species were most abundant. Species characterized by a cleistogamous pollination system were found almost exclusively in high-altitude sites, whereas the proportion of species displaying floral traits related to pollination by long-tongued moths (sphinx) and flies sharply decreased with increasing altitude.
Main conclusions Environmental conditions associated with altitude exert a large influence on orchid species composition and the distribution of orchid breeding systems. Our results revealed a high proportion of auto-pollinating species, and confirm earlier findings that auto-pollinating species are more frequent in high-altitude sites.
Rivers are conduits for materials and energy; this, the frequent and intense disturbances that these systems experience, and their narrow, linear nature, create problems for conservation of biodiversity and ecosystem functioning in the face of increasing human influence. In most parts of the world, riparian zones are highly modified. Changes caused by alien plants — or environmental changes that facilitate shifts in dominance creating novel ecosystems — are often important agents of perturbation in these systems. Many restoration projects are underway. Objective frameworks based on an understanding of biogeographical processes at different spatial scales (reach, segment, catchment), the specific relationships between invasive plants and resilience and ecosystem functioning, and realistic endpoints are needed to guide sustainable restoration initiatives. This paper examines the biogeography and the determinants of composition and structure of riparian vegetation in temperate and subtropical regions and conceptualizes the components of resilience in these systems. We consider changes to structure and functioning caused by, or associated with, alien plant invasions, in particular those that lead to breached abiotic- or biotic thresholds. These pose challenges when formulating restoration programmes. Pervasive and escalating human-mediated changes to multiple factors and at a range of scales in riparian environments demand innovative and pragmatic approaches to restoration. The application of a new framework accommodating such complexity is demonstrated with reference to a hypothetical riparian ecosystem under three scenarios: (1) system unaffected by invasive plants; (2) system initially uninvaded, but with flood-generated incursion of alien plants and escalating invasion-driven alteration; and (3) system affected by both invasions and engineering interventions. The scheme has been used to derive a decision-making framework for restoring riparian zones in South Africa and could guide similar initiatives in other parts of the world.
Morphological and functional characteristics of flowers may have major effects on their reproductive success. Here, we report a study on the characteristics of flowers of Petrocoptis viscosa, a herb species endemic to the northwest Iberian Peninsula, restricted to crevices in limestone outcrops, and currently occurring in only three populations within an area of less than 30 km2. We also investigated the effects of pollen source on indicators of reproductive success. The results show that Petrocoptis viscosa flowers are well adapted to autogamy. Inbreeding depression (as determined by comparison of results obtained after selfing and outcrossing) was negligible for fruit production (δ=−0.05) and mean seed number (δ=−0.11), low for seed germination percentage (δ=0.08), but relatively high for mean seed weight (δ=0.23). The spatial structure and small size of population of Petrocoptis viscosa may mean that inbreeding is frequent in natural habitats. Adaptation of plants to autogamy may therefore be energetically beneficial (i.e. less wasted expenditure on rewards and flowers).
We studied hummingbirds and their food plants in an area of caatinga vegetation. We specifically examined their seasonal use of this habitat, migratory and non-migratory status, their foraging strategies and community roles The study was conducted in an area of arboreal-shrub caatinga, located in the Serra do Pará, municipality of Santa Cruz do Capibaribe, state of Pernambuco in northeastern Brazil. Field work was undertaken during 12 expeditions on a monthly basis between June, 2007 and May, 2008. Five species of hummingbirds were recorded visiting flowers in the community studied. Three were considered residents: Chlorostilbon lucidus (Shaw, 1812), Eupetomena macroura (Gmelin, 1788), and Heliomaster squamosus (Temminck, 1823). Hummingbirds visited 31 species of plants, of which only five presented attributes related to ornithophily. C. lucidus visited 29 plant species, including all ornithophilous species, and it was the most aggressive, defending territories. Among hummingbirds, C. lucidus may be considered the principal pollinator. Hummingbirds may also be acting as pollen vectors for some of the plant species not identified as ornithophilous. The hummingbird guilds varied among the plant species used as floral resources, as well as in their frequency of visits. Differences in plant species abundance, hummingbird preference, competitive exclusion or flowering seasonality are factors likely to influence those variations.
Determining whether seed production is pollen limited has been an area of intensive empirical study over the last two decades. Yet current evidence does not allow satisfactory assessment of the causes or consequences of pollen limitation. Here, we critically evaluate existing theory and issues concerning pollen limitation. Our main conclusion is that a change in approach is needed to determine whether pollen limitation reflects random fluctuations around a pollen–resource equilibrium, an adaptation to stochastic pollination environments, or a chronic syndrome caused by an environmental perturbation. We formalize and extend D. Haig and M. Westoby’s conceptual model, and illustrate its use in guiding research on the evolutionary consequences of pollen limitation, i.e., whether plants evolve or have evolved to ameliorate pollen limitation. This synthesis also reveals that we are only beginning to understand when and how pollen limitation at the plant level translates
into effects on plant population dynamics. We highlight the need for both theoretical and empirical approaches to gain a deeper understanding of the importance of life-history characters, Allee effects, and environmental perturbations in population declines mediated by pollen limitation. Lastly, our synthesis identifies a critical need for research on potential effects of pollen limitation at the community and ecosystem levels.
Variation in interspecific interactions across geographic space is a potential driver of diversification and local adaptation. This study quantitatively examined variation in floral phenotypes and pollinator service of Heliconia bihai and H. caribaea across three Antillean islands. The prediction was that floral characters would correspond to the major pollinators of these species on each island. Analysis of floral phenotypes revealed convergence among species and populations of Heliconia from the Greater Antilles. All populations of H. caribaea were similar, characterized by long nectar chambers and short corolla tubes. In contrast, H. bihai populations were strongly divergent: on Dominica, H. bihai had flowers with short nectar chambers and long corollas, whereas on Hispaniola, H. bihai flowers resembled those of H. caribaea with longer nectar chambers and shorter corolla tubes. Morphological variation in floral traits corresponded with geographic differences or similarities in the major pollinators on each island. The Hispaniolan mango, Anthracothorax dominicus, is the principal pollinator of both H. bihai and H. caribaea on Hispaniola; thus, the similarity of floral phenotypes between Heliconia species suggests parallel selective regimes imposed by the principal pollinator. Likewise, divergence between H. bihai populations from Dominica and Hispaniola corresponded with differences in the pollinators visiting this species on the two islands. The study highlights the putative importance of pollinator-mediated selection as driving floral convergence and the evolution of locally-adapted plant variants across a geographic mosaic of pollinator species.
Serpentine-derived soils create stressful conditions for the establishment and growth of plants, and their associated floras are characterized by high diversity and endemism. A review of floristic literature and herbarium holdings, along with field work, showed that 12 endemic plant species are restricted to serpentine soils in Puerto Rico. An additional 28 non-endemic species are known only from serpentine in Puerto Rico. Reports on associated substrates outside Puerto Rico were found for 25 of these 28 species, limestone and serpentine being the most common. Only Thelypteris brittonae was found to be restricted to serpentine soils on and off the island. Another 35 species, of which 13 are endemic to Puerto Rico, are limited to extreme substrates on the island (i.e., serpentine, limestone, silicaceous sands, chert, and hydrothermally altered soils); all but one occur on both serpentine and limestone. All the endemic serpentine-restricted species are rare, uncommon or very localized within their limited distribution. However, only two have been placed on the United States Federal list as threatened or endangered.
The proposition in two recently published papers that the concentration of sugar in nectars of flowers adapted to hummingbird pollination tends to be unusually high compared with that for most insect-pollinated flowers is contradicted, with evidence. Increased cross-pollination when hummingbirds are forced to visit many flowers, difficulties in rapidly ingesting viscous nectar, and need for water as a dietary article are suggested factors in keeping down nectar-sugar concentrations.
Species flowering during the dry season (late December to early April) form three main pollinator groups, namely, butterfly, solitary bee, and hummingbird flowers. The animal vectors present match these three flower syndromes. The daily and seasonal rhythms of flower opening and pollination activity are synchronized. Butterflies and solitary bees, active chiefly in the morning, visit flowers blooming only half a day. The number of seeds per fruit and the pollen-carrying capacity of the pollen vector are correlated. Butterflies, carrying few pollen grains, chiefly pollinate flowers with one to four seeds. Solitary bees, carrying many grains, chiefly pollinate flowers with many seeds per flower. These close links between the flowers and their visitors result in a high degree of successful pollination and a high percentage fruit set. A group of species, attracting no visitors, was characterized by a very narrow 'pollination gap,' making self-pollination almost inevitable. Heavy fruiting indicated self-fertility. Heterocorollary in Cordia sebestena, a double keel in Stylosanthes hamata, and several examples of andromonoecy are recorded for the first time. The presence of the adventive honeybee, Apis mellifera, in the association appeared detrimental to the native pollinators when forage was scarce. The whole scrub association appears balanced with a distinctive pattern of floral ecology. This circumstance, in terms of pollinators, is designated a Butterfly-Solitary bee-Hummingbird association.
The author combined the results of a two year pollination experiment and a three year demographic assessment of a population of Tolumnia variegata in a matrix model of population dynamics, and by means of simulations evaluated the effect of pollination intensity and frequency, fruit production, and cost of fruiting on the asymptotic population growth rate. Mean natural fruit set in this population was <1%, whereas intermediate and high pollination intensity resulted in mean fruit set of 35 and 72%, respectively. In any given year, c98% of all flowering individuals fail to set fruit under natural conditions. Despite the dramatic increase in fruit set after hand-pollination, only plants in the high pollination intensity treatment showed a statistically significant reduction in future growth and flowering. A small seedling production per fruit would be enough to overcome the cost of fruiting; plants in the population should thus experience strong selection for increased pollination. This does not seem to explain nonautogamous orchids. Results suggest an alternative explanation: pollinator limitation could be evolutionarily stable if the correlation between fruit or seed production and seedling recruitment is sufficiently low. If an increase in fruit or seed production does not translate into an increase in fitness, then selection for increased pollination would not occur or would be too weak. -from Author
Background and aims:
Evolutionary transitions from outcrossing to self-fertilization are thought to occur because selfing provides reproductive assurance when pollinators or mates are scarce, but they could also occur via selection to reduce floral vulnerability to herbivores. This study investigated geographic covariation between floral morphology, fruit set, pollen limitation and florivory across the geographic range of Camissoniopsis cheiranthifolia, a Pacific coastal dune endemic that varies strikingly in flower size and mating system.
Methods:
Fruit set was quantified in 75 populations, and in 41 of these floral herbivory by larvae of a specialized moth (Mompha sp.) that consumes anthers in developing buds was also quantified. Experimental pollen supplementation was performed to quantify pollen limitation in three large-flowered, outcrossing and two small-flowered, selfing populations. These parameters were also compared between large- and small-flowered phenotypes within three mixed populations.
Key results:
Fruit set was much lower in large-flowered populations, and also much lower among large- than small-flowered plants within populations. Pollen supplementation increased per flower seed production in large-flowered but not small-flowered populations, but fruit set was not pollen limited. Hence inadequate pollination cannot account for the low fruit set of large-flowered plants. Floral herbivory was much more frequent in large-flowered populations and correlated negatively with fruit set. However, florivores did not preferentially attack large-flowered plants in three large-flowered populations or in two of three mixed populations.
Conclusions:
Selfing alleviated pollen limitation of seeds per fruit, but florivory better explains the marked variation in fruit set. Although florivory was more frequent in large-flowered populations, large-flowered individuals were not generally more vulnerable within populations. Rather than a causative selective factor, reduced florivory in small-flowered, selfing populations is probably an ecological consequence of mating system differentiation, with potentially significant effects on population demography and biotic interactions.
Several floral microbes are known to be pathogenic to plants or floral visitors such as pollinators. Despite the ecological and economic importance of pathogens deposited in flowers, we often lack a basic understanding of how floral traits influence disease transmission. Here, we provide the first systematic review regarding how floral traits attract vectors (for plant pathogens) or hosts (for animal pathogens), mediate disease establishment and evolve under complex interactions with plant mutualists that can be vectors for microbial antagonists. Attraction of floral visitors is influenced by numerous phenological, morphological and chemical traits, and several plant pathogens manipulate floral traits to attract vectors. There is rapidly growing interest in how floral secondary compounds and antimicrobial enzymes influence disease establishment in plant hosts. Similarly, new research suggests that consumption of floral secondary compounds can reduce pathogen loads in animal pollinators. Given recent concerns about pollinator declines caused in part by pathogens, the role of floral traits in mediating pathogen transmission is a key area for further research. We conclude by discussing important implications of floral transmission of pathogens for agriculture, conservation and human health, suggesting promising avenues for future research in both basic and applied biology.
Nectar robbers may have direct and indirect effects on plant reproductive success but the presence of nectar robbing is not proof of negative fitness effects. We combined census data and field experiments to disentangle the complex effects of nectar robbing on nectar production rates, pollinator behavior, pollen export, and female reproductive success of Pitcairnia angustifolia. Under natural conditions flowers were visited by four different animal species including a robber-like pollinator and a secondary robber. Natural levels of nectar robbing ranged from 40 to 100%. Natural variation in nectar robbing was not associated with fruit set in any year whereas seed set was weakly positively associated for 1 year only. Artificial nectar robbing did not increase nectar production or concentration, did not affect the behavior of long-billed hummingbirds, and when faced with artificially robbed flowers, these visitors behaved as secondary nectar robbers. The number of stigmas within a patch that received pollen dye analogs and the average distance traveled by these analogs were not significantly different between robbing treatments (robbed flowers versus unrobbed flowers), but the maximum distance traveled by these pollen analogs was higher when nectar robbing was not prevented. Overall, the proportion of robbed flowers on an inflorescence had a neutral effect to a weak positive effect on the reproduction of individual plants (i.e. positive association between nectar robbing and fruit set in 2002) even when it clearly changed the behavior of its most efficient pollinator potentially increasing the frequency of nectar robbing within a plant.
Island and mainland populations of plants often differ in their reproductive biology and genetics. The differences become more pronounced the further islands are from mainland sources. Altered pollination conditions have influenced the floral biology and mating systems of island plants in distinct ways. Insufficient pollination has favoured selection of floral traits promoting selfing. In contrast, inferior pollinator service resulting in selfing and inbreeding depression appears to be a factor involved in the evolution of sexual dimorphisms. Stochastic forces play a major role in governing patterns of genetic variation. Island populations are usually more differentiated and contain less diversity than comparable mainland samples. Many general issues in evolutionary biology can be addressed by studies of reproduction and genetics in island plants.
Procedures are described for partitioning the selfing rate into contributions resulting from the different modes of chasmogamous selfing (geitonogamous, facilitated, prior, competing, and delayed) and for examining several functional aspects of self-fertilization associated with the different modes (reproductive assurance, degree of seed and pollen discounting, and relative abilities of cross- and self-pollen to fertilize ovules). The procedures involve floral manipulations, eg exclusion of pollinators, emasculation, and covering of stigmas. The method of partitioning selfing into modes is illustrated using data from a natural population of the annual plant Impatiens pallida. Selfing in the chasmogamous flowers of this species results primarily from geitonogamy. -from Authors
Theory predicts that nectarivores respond to changes in profitability of patches of flowers or feeders by adjusting visitation rate to increase reward size. We conducted a set of experiments in an outdoor enclosure with seven feeders to determine how Phaethornis longirostris, a traplining hummingbird, adjusts its visitation rates in response to changes in sucrose solution delivery rates. Each experiment tested the response of P. longirostris to the following changes in the timing and volume of sucrose solution delivery: (1) increases in sucrose solution abundance at all feeders (mimicking seasonal increases in numbers of open flowers or nectar output); (2) large changes in sucrose solution availability at one feeder (mimicking increases or decreases of parch profitability); and (3) sudden unexpected decreases in sucrose solution availability at one feeder (mimicking loss of nectar to competitors). We found that P. longirostris (1) decreased visitation rates when the sucrose solution delivery rate was higher at all feeders, (2) increased visitation rates to individual feeders when their profitability increased for whole days but did not significantly decrease visitation rates when feeder output decreased; and (3) responded to sudden food losses at a feeder (due to simulated competition) by increasing use of that feeder for 1 or 2 h after the loss.
Astrophytum asterias es una cactácea amenazada que se distribuye en el sur de Texas y noreste de México. En este estudio intentamos proporcionar datos básicos sobre la biología reproductiva de esta especie. Los experimentos en el sistema reproductivo de esta especie se realizaron en un sitio en el condado de Starr, Texas. Se aplicaron diferentes tratamientos de polinización a las flores de diferentes individuos para conocer si la especie es autocompatible o autoincompatible, y para saber si está experimientando limitación por polinizadores. En cada tratamiento y en los controles, calculamos el número promedio de frutos viables producidos y se calculó la producción promedio de semillas por individuo. Los controles presentaron 18.3% de producción de frutos con un promedio de 13.3 ± 14.7 semillas. El tratamiento de polinización cruzada tuvo como resultado 88.6% de producción de frutos, con una producción promedio de 95.8 ± 5.9 semillas. La media de la producción de frutos y semillas en el tratamiento de polinización cruzada fue un fruto y el promedio de la media de producción de semillas fue de 92.7. Si bien algunos de los controles produjeron frutos y semillas, el promedio de la media de producción de frutos y semillas fue 0. No hubo producción de frutos y semillas para los tratamientos de autofertilización. Estos resultados muestran que Astrophytum asterias posee cruzamiento exógeno obligado. El éxito reproductivo entonces depende de vectores externos para el transporte del polen y la consecuente producción de semillas. Nuestros resultados indican que, debido a que la especie es autoincompatible, A. asterias pudiera experimentar restricciones reproductivas en función de la disponibilidad o la eficacia de los polinizadores.
The variation of floral sex allocation with flower position within inflorescences was investigated in the spring ephemeral, Corydalis ambigua . Investment in female function (pistil), attraction (corolla) and nectar production decreased from bottom to top flowers, whereas male investment (stamen) did not differ.
This self‐incompatible species appears to set seeds as a result of visitation by nectar robbing bumblebee queens. The tendency of bees to visit lower flowers first and then move upwards within an inflorescence should result in directional pollen flow from bottom to top flowers.
Naturally pollinated upper flowers set fewer seeds than intermediate and lower flowers due to pollen limitation. The lack of differences in seed set and seed mass per pod following artificial outcrossing indicated that resource limitation did not explain the variation in seed production of flowers in different positions. Pollen viability also did not differ significantly between flower positions.
A model of pollination was developed that incorporated the visitation pattern of bumblebees and observed variations in nectar distribution between flower positions. This predicted that receipt of outcross pollen would decrease from bottom to top flowers, but that pollen export to other plants would not differ between flower positions provided that the pollen exchange rate of pollinators was either small or positively correlated with nectar content of each flower position. The observed pattern of floral sex allocation would then be parallel to relative success of pollen export and import between flower positions within inflorescences.
Summary 1 Phenological patterns of flowering and fruiting are presented for 5800 trees of a Philip- pine submontane forest community during a 4-year period. Circular vector algebra allowed species to be grouped into annual (34 species), supra-annual (3), irregular (7), and continuous (13) reproducers. 2 Wind- and gravity-dispersed species had extended fruiting periods coinciding with the typhoon season (July to November), whereas fleshy fruited trees showed peaks matching those of solar irradiance. Most species flowered at the beginning and fruited at the end of the first peak (April), or they flowered during the first peak and fruited during the second peak (September), indicating that solar irradiance may be a strong selective factor in shaping community-wide phenology patterns. 3 An El Niño and a La Niña climate anomaly occurred during the study period. Prin- cipal component analysis showed that 95% of intraspecific variation of flowering and fruiting dates could be explained by delayed or advanced flowering and fruiting of a limited number of species. Mast-fruiting of dipterocarp species could not be correlated with El Niño and La Niña events. 4 Large climate-induced variation in phenology was demonstrated for the percentage of trees that reproduce, while the timing of phenology remained unaffected for most species, suggesting that climatic factors are not directly responsible for triggering and synchronization of phenological events.
Most orchids studied thus far show long-term resource adjustments to increases in fruit production within a flowering season, but none of these offers rewards to their potential pollinators. If nectar production is energetically expensive, then resources utilized to produce fruits and seeds may be even more limited in pollinator-rewarding orchids than in non-rewarding ones. Thus, resource adjustments may be more dramatic or entirely different in nectar producing plants. In this study, we performed artificial hand-pollinations for two consecutive flowering seasons in die nectar producing orchid Comparettia falcata, and tested whether or not fruit set, seed set, and seed viability were limited by the quantity of pollinations or by resources. In addition, we compared mechanisms of short-term (fruit abortion within seasons) and long-term consequences (percent change in leaf length and change in flower number per plant between seasons, probability of shoot and inflorescence production, and mortality) between hand- pollinated and unmanipulated plants. The relationships among plant traits related to vegetative size and reproduction also were examined. Hand-pollinations showed some negative effects. Fruit set was higher in hand-pollinated plants in the first season but was similar to the controls in the second. Seed set was significantly lower and abortions were higher than in unmanipulated plants. On the other hand, some of our measurements were unaffected by die hand-pollination treatment. Unexpectedly, there were no significant differences between groups in percent change in leaf length, change in flower number per plant between seasons, or die probability of shoot and inflorescence production. Although there was a strong correlation between leaf size and die number of flowers produced within a season, associations between leaf size and traits related to current or future reproduction were not consistent. Like other epiphytic orchids, pollination limitation occurred within a single season in C. falcata., but increases in fruit production also resulted in reduced lifetime fitness as estimated by a compounded fitness index. Contrary to all other epiphytic orchids studied, long-term adjustments to increased fruit production in C. falcata through reduction in future growth or flower and inflorescence production were either minor or lacking. Our results suggest that the nature of plant strategies associated with resource constraints during sexual reproduction may be dependent on whether or not plants have evolved traits that are costly.
La mayoría de las orquideas estudiadas hasta el presente presentan ajustes a aumentos en producción de frutos dentro de una temporada de floración pero ninguna de estas ofrece recompensas a sus polinizadores potenciales. Si la producción de nectar es energyéticamente costosa, entonces los recursos utilizados para producir frutos y semillas podrian estar aún más limitados en las orquideas que ofrecen recompensa que en las que no las ofrecen. Asi, los ajustes de recursos podrían ser aún más dramáticos o totalmente diferentes. En este estudio realizamos polinizaciones artificiales por dos temporadas consecutivas en la orquídea productora de nectar Comparettia falcata y comprobamos si la producción de frutos y la producción y viabilidad de las semillas estaba limitada por la cantidad de polinizadores o de recursos. Además, comparamos las consecuencias a corto plam (aborto de frutos dentro de una temporada) y a largo plazo (porciento de cambio en el largo de la hoja, cambio en el número de flores por planta entre temporadas, probabilidad de producción de tallo e inflorescencia y mortalidad) entre plantas polinizadas manualmente y plantas no manipuladas. La relación entre caracteristicas de la planta relacionas con el tamaño vegetativo y la reproducción también fueron examinadas. Las polinizaciones manuales tuvieron effectos negativos. La producción de frutos fué mayor en las plantas polinizadas manualmente en la primera temporada pero fué similar en la segunda. La producción de semillas fué significativamente menor y el aborto de frutos fué significativamente mayor en plantas polinizadas manualmente. Por otro lado, algunas de nuestras medidas no pueron afectadas por el tratamiento de polinización. Inesperadamente, no hubo diferencias significativas en el porciento de cambio en tamaño de la hoja, en el cambio en número de Hores por planta entre temporadas, en la probabilidad de produccion de frutos o inflorescencias, ni en mortalidad. Apesar de que hubo una fuerte correlación entre el tamaño de la hoja y el número de flores producidas dentro de una temporada, las asociaciones entre el tamaño de la hoja y caracteristicas relacionadas con reproducción presente y futura no fueron consistentes. Al igual que otras orquídeas epifitas, la limitación por polinización ocurre dentro de una misnia temporada en C. fiLcata pero aumentos en producción de fruros también resultaron en una disminución en la adecuación en el transcurso de la vida de la planta según un índice compuesto de adecuacién estimado. Contrario a todas las demás orquídeas epífitas estudiadas, 10s ajustes a largo plam en forma de reducción de crecimento futuro y reducción de flores e inflorecencias futuras fueron mínimos o estuvieron ausentes en C. falcata. Nuestro resultados sugieren que la naturaleza de las estrategias asociadas a limitación de recursos durante la reproducción sexual podrían depender de que las plantas hayan evolucionado o no características que son costosas.
Sinojackia dolichocarpa, a species endangered and endemic to China, is distributed only in the regional area of Shimen and Sangzhi in Hunan Province. Inter-simple sequence repeat (ISSR) markers were used to investigate the genetic diversity within and among the four natural populations of S. dolichocarpa. Leaf samples were collected from 84 individuals. Thirteen ISSR primers selected from 80 primers gave rise to 137 discernible DNA bands of which 100 (72.99%) were polymorphic. On average each primer gave rise to 10.5 bands including 7.7 bands with polymorphic profile. At the species level, high genetic diversity was detected (PPB: 72.99%; HE: 0.2255; Ho: 0.3453). However, relatively low genetic diversity existed within populations. Population in Maozhuhe (MZH) exhibits the greatest level of variability (PPB: 40.38%, HE: 0.1566, Ho: 0.2330), whereas the population in Jingguanmen (JGM) finds its own variability at the lowest level (PPB: 30.66%; HE: 0.1078; Ho: 0.1601). A high level of genetic differentiation among populations was revealed by Nei's gene diversity statistics (45.30%), Shannon's information measure (45.24%) and analysis of molecular variance (AMOVA) (52.88%). The main factors responsible for the high level of differentiation among populations are probably related to the selfing reproductive system and the isolation of populations. The strong genetic differentiation among populations indicates that the management for the conservation of genetic variability in S. dolichocarpa should aim to preserve every population.