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Flowering Season (flowering + season)
Selected AbstractsStaggered Flowering in Four Sympatric Varieties of Geonoma cuneata (Palmae),BIOTROPICA, Issue 4 2002Finn Borchsenius ABSTRACT Phenology, flowering biology, and pollination were studied for one year in four sympatric varieties of the polymorphic palm Geonoma cuneata in Ecuador. Flowering seasons of the three most common varieties were significantly staggered resulting in minimal temporal overlap. No marked differences were found with respect to flowering biology or pollination. The implication of these findings for explaining the complicated morphological variation pattern found in G. cuneata and similar species complexes is discussed. [source] Nectar ,theft' by hummingbird flower mites and its consequences for seed set in Moussonia deppeanaFUNCTIONAL ECOLOGY, Issue 1 2001Lara C. Summary 1,Mites (Acari: Mesostigmata: Ascidae) that live and feed in the flowers of about 100 plant species are transported in the nares of hummingbirds (Trochilidae). Mites may compete with hummingbirds for nectar secreted by the host plants, and this could affect the dynamics and reproductive outcomes of the mutualism between plants and their pollinating hummingbirds. 2,Here we combined field observations and experimental manipulations to assess the role of hummingbird flower mites (Tropicoseius sp. nov.) on nectar secretion and reproductive output of protandrous Moussonia deppeana (Schlecht. & Cham.) Hanst. (Gesneriaceae) during their flowering period in a cloud forest remnant. 3,During the 4 days that the flowers of M. deppeana last, flowers were visited exclusively by hummingbirds (Lampornis amethystinus). Bud production per inflorescence peaked in December. There were few open flowers per inflorescence in November, but numbers increased as the flowering season progressed (December and January). 4,The availability of each flower phase differed over the flowering season. Staminate-phase flowers were more abundant over the flowering season than pistillate-phase flowers. These differences were statistically significant over time. 5,Nectar availability was reduced by up to 50% in the presence of hummingbird flower mites. Over the 4 days of observation, significantly more nectar was secreted to flowers from which mites were excluded than to flowers with no mite exclusion. The same effect was observed during flowering, but mites consumed a greater percentage of the total nectar secreted in December. 6,Significantly more nectar was secreted during the staminate phase than in the pistillate phase, independent of time and treatment. 7,A manual pollination experiment suggested that mites act like secondary pollinators in this self-compatible, non-autogamous plant, at least in flowers that were not pollinated manually and had no access to pollinating hummingbirds. 8,Although seed production was not reduced significantly by flower mites, our results suggest that the presence of floral mites can affect pollen transmission, as the amount of nectar available to hummingbirds was reduced drastically. This can directly affect hummingbird foraging patterns and reduce the fitness of the host plants. [source] The role of rainfall and predators in determining synchrony in reproduction of savanna trees in Serengeti National Park, TanzaniaJOURNAL OF ECOLOGY, Issue 1 2007SIMON A. R. MDUMA Summary 1We examined the factors determining synchrony in reproduction in nine Acacia and six other tree species in the Serengeti ecosystem. 2We test two hypotheses: (i) an abiotic hypothesis where the primary determinant of synchrony is an adaptation to water availability; and (ii) biotic hypotheses where these adaptations to water can be further refined by additional adaptations to avoid predators, or attract seed and fruit dispersers. 3Flowering and fruiting were recorded monthly for individually marked trees during 1997,2004. Flowering in different species occurs semi-annually, annually or, in the case of one species, once every 2 years. For most species synchrony of flowering was correlated with seasonal rainfall, with lags related to the mean height of the species; small species flowered during the rains while larger species flowered in the dry season. Fruiting seasons occurred at the end of the rains irrespective of the flowering season. 4Most species showed flowering synchrony greater than expected from the distribution of rainfall. This may be related to avoidance of insect seed predators through predator satiation. Two Acacias showed multi-annual fruiting (masting), possibly as a predator avoidance mechanism. Acacia tortilis has two flowering seasons: a dry season flowering with early abortion of pods and a wet season flowering producing successful fruits. 5Two species of Commiphora appeared to be synchronized so as to attract birds that disperse seeds. Acacia tortilis produced indehiscent pods attractive to ungulates, possibly to kill bruchid beetles during digestion and so increase seed viability. 6Our results suggest that synchrony in these trees is caused by a strong interaction between abiotic and biotic factors. Closely related species have different reproductive patterns of synchrony that seem to be adapted to different combinations of rainfall, predators and dispersers. Rainfall is the primary determinant but the activities of predators and dispersers increase the degree of synchrony. [source] Seasonal changes in pollinator activity influence pollen dispersal and seed production of the alpine shrub Rhododendron aureum (Ericaceae)MOLECULAR ECOLOGY, Issue 4 2006A. S. HIRAO Abstract In alpine ecosystems, microscale variation in snowmelt timing often causes different flowering phenology of the same plant species and seasonal changes in pollinator activity. We compared the variations in insect visitation, pollen dispersal, mating patterns, and sexual reproduction of Rhododendron aureum early and late in the flowering season using five microsatellites. Insects visiting the flowers were rare early in the flowering season (mid-June), when major pollinators were bumblebee queens and flies. In contrast, frequent visitations by bumblebee workers were observed late in the season (late July). Two-generation analysis of pollen pool structure demonstrated that quality of pollen-mediated gene flow was more diverse late in the season in parallel with the high pollinator activity. The effective number of pollen donors per fruit (Nep) increased late in the season (Nep = 2.2,2.7 early, 3.4,4.4 late). However, both the outcrossing rate (tm) and seed-set ratio per fruit were smaller late in the season (tm = 0.89 and 0.71, seed-set ratio = 0.52 and 0.18, early and late in the season, respectively). In addition, biparental inbreeding occurred only late in the season. We conclude that R. aureum shows contrasting patterns of pollen movement and seed production between early and late season: in early season, seed production can be high but genetically less diverse and, during late season, be reduced, possibly due to higher inbreeding and inbreeding depression, but have greater genetic diversity. Thus, more pollinator activity does not always mean more pollen movement. [source] Reaction norms of life history traits in response to zinc in Thlaspi caerulescens from metalliferous and nonmetalliferous sitesNEW PHYTOLOGIST, Issue 1 2007Caroline Dechamps Summary ,,We examined phenotypic plasticity of fitness components in response to zinc (Zn) in the Zn hyperaccumulator, Thlaspi caerulescens. ,,Two populations from Zn-enriched soils (M) and two populations from normal soils (NM) were grown in pots at three Zn concentrations (0, 1000 and 8000 mg kg,1 Zn), for an entire life cycle. Growth, Zn accumulation and fitness components were assessed. ,,Based on vegetative growth, M and NM populations had similar Zn tolerance at 1000 mg kg,1 Zn. However, reproductive output was markedly decreased in NM at 1000 and 8000 mg kg,1 Zn. In M populations, Zn did not affect fitness. However, low Zn status enhanced reproductive output in year 1 compared with year 2 and decreased survival after the first flowering season. ,,M populations are able to achieve equal fitness across a broad range of Zn concentrations in soil by different combinations of fecundity and longevity. No cost of higher tolerance was demonstrated in M populations. Reproductive traits appeared to be a more sensitive indicator of tolerance than vegetative growth. [source] Seedling establishment, mortality, tree growth rates and vigour of Acacia nilotica in different Astrebla grassland habitats: Implications for invasionAUSTRAL ECOLOGY, Issue 3 2002Ian J. Radford Abstract A demographic study was conducted in the northern Australian Astrebla grasslands to determine the importance of habitat type in influencing invasion patterns of Acacia nilotica, an exotic leguminous tree from Africa and Asia. One of the repeated patterns observed for A. nilotica is that denser populations are often associated with riparian habitats. Data available on this species do not enable us to determine which of a number of processes has lead to the formation of this pattern. Several explanations were tested for patterns in tree abundance: (i) that more seedlings emerge in wetter habitats; (ii) that mortality is lower in wetter habitats; (iii) that growth rates are faster in wetter habitats; and (iv) that plants are more vigorous (as indicated by leaf cover, flowering intensity and predation rates) over longer periods in wetter habitats. The study was stratified across three habitat types, perennial and ephemeral riparian and non-riparian, which are characteristic of Astrebla grasslands and differentiated by the availability of water. In addition to testing for habitat-linked differentiation in demography, data were also used to test whether seedling emergence, mortality, growth and vigour varied between sites with cattle versus sheep. The data collected indicated that seedling emergence, determined primarily by livestock dispersal, was likely to be the dominant influence on patterns of A. nilotica invasion. Mortality and growth rates were similar in ephemeral riparian and non-riparian habitats, whereas perennial riparian habitats had more rapid growth rates, which may increase the rate of invasion in these areas. Plant vigour was also greater over longer periods in perennial riparian habitats with greater leaf cover, longer flowering season and fewer insect borer holes. Livestock species were found to have little influence on the demography of A. nilotica plants in this study. Very low growth rates and high mortality in A. nilotica populations are likely to lead to net decline in ephemeral riparian and non-riparian habitats in the long term. The importance of episodic recruitment in the maintenance of A. nilotica populations is discussed. [source] Fitness consequences of floral variation in Senecio jacobaea (Asteraceae): evidence from a segregating hybrid population and a resource manipulation experimentBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2001STEFAN ANDERSSON The present study examines some of the ecological factors that might exert selection on floral morphology in Senecio jacobaea, a self-sterile composite which exhibits geographic variation in the frequency of rayed and discoid individuals. Regression analyses of phenotypic data from a large, segregating hybrid population, established in a semi-natural (garden) environment and studied over a 2-year period, revealed a negative relationship between the size of the rays and the average germination rate of the maternal seed crop, a pattern that can be attributed to the reduced germination speed of achenes from ray florets. There was no effect of ray size on the amount of cross-pollination achieved, the proportion of heads infested by larvae of seed flies (Pegohylemyia) and the amount of resources retained for the next flowering season. The lack of resource costs was also apparent in a manipulation experiment with greenhouse-grown plants of the rayed phenotype: artificial removal of all rays at the early bud or flowering stage had no detectable effect on subsequent flower and fruit development, regardless of whether the plants experienced high or low water stress. Given these and other observations, I hypothesize that plant-animal interactions and resource costs sometimes play a minor role in exerting selection on flower morphology and that spatially varying selection on germination behaviour accounts for some of the morph frequency variation in S. jacobaea. [source] Seed ecology of a Mediterranean perennial herb with an exceptionally extended flowering and fruiting seasonBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2003F. XAVIER PICÓ Lobularia maritima is a Mediterranean short-lived herb with a flowering and fruiting season that lasts for ten months. Previous studies have shown that recruitment in periods other than autumn of the flowering season has few demographic implications; that is contributes little to the population growth rate. Since environmental conditions in periods other than autumn would allow recruitment, we examined to what extent the seed ecology of L. maritima accounts for recruitment shortage for the greater part of the year. To this end, we studied the effects of selfing and outcrossing on seed production and germination, within- and between-year variation in seed mass and germination, seed characteristics in the soil seed bank throughout the year, and the effect of temperature as a factor controlling seed germination. Results indicate that selfing does not decrease recruitment, and thus the observed changes in visitation rate and pollinator composition throughout the year cannot account for differences in recruitment. Germinability decreases throughout the year, suggesting a possible cost in reproduction associated with extended flowering. L. maritima has a transient seed bank whose seeds also experience a decrease in their germination throughout the year. Finally, temperature affects seed germination patterns, indicating the existence of quiescence mechanisms that prevent germination in the months prior to the summer drought. Overall, the results obtained support and, at least partly, explain the recruitment patterns of L. maritima observed in the field. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142, 273,280. [source] The role of rainfall and predators in determining synchrony in reproduction of savanna trees in Serengeti National Park, TanzaniaJOURNAL OF ECOLOGY, Issue 1 2007SIMON A. R. MDUMA Summary 1We examined the factors determining synchrony in reproduction in nine Acacia and six other tree species in the Serengeti ecosystem. 2We test two hypotheses: (i) an abiotic hypothesis where the primary determinant of synchrony is an adaptation to water availability; and (ii) biotic hypotheses where these adaptations to water can be further refined by additional adaptations to avoid predators, or attract seed and fruit dispersers. 3Flowering and fruiting were recorded monthly for individually marked trees during 1997,2004. Flowering in different species occurs semi-annually, annually or, in the case of one species, once every 2 years. For most species synchrony of flowering was correlated with seasonal rainfall, with lags related to the mean height of the species; small species flowered during the rains while larger species flowered in the dry season. Fruiting seasons occurred at the end of the rains irrespective of the flowering season. 4Most species showed flowering synchrony greater than expected from the distribution of rainfall. This may be related to avoidance of insect seed predators through predator satiation. Two Acacias showed multi-annual fruiting (masting), possibly as a predator avoidance mechanism. Acacia tortilis has two flowering seasons: a dry season flowering with early abortion of pods and a wet season flowering producing successful fruits. 5Two species of Commiphora appeared to be synchronized so as to attract birds that disperse seeds. Acacia tortilis produced indehiscent pods attractive to ungulates, possibly to kill bruchid beetles during digestion and so increase seed viability. 6Our results suggest that synchrony in these trees is caused by a strong interaction between abiotic and biotic factors. Closely related species have different reproductive patterns of synchrony that seem to be adapted to different combinations of rainfall, predators and dispersers. Rainfall is the primary determinant but the activities of predators and dispersers increase the degree of synchrony. [source] Spatial repartition and genetic relationship of green and albino individuals in mixed populations of Cephalanthera orchidsPLANT BIOLOGY, Issue 4 2010V. Tranchida-Lombardo Abstract Several green orchids of the Neottieae tribe acquire organic carbon both from their mycorrhizal fungi and from photosynthesis. This strategy may represent an intermediate evolutionary step towards mycoheterotrophy of some non-photosynthetic (albino) orchids. Mixed populations of green and albino individuals possibly represent a transient evolutionary stage offering opportunities to understand the evolution of mycoheterotrophy. In order to understand the emergence of albinos, we investigated patterns of spatial and genetic relationships among green and albino individuals in three mixed populations of Cephalanthera damasonium and one of C. longifolia using spatial repartition and Amplified fragment length polymorphism (AFLP) markers. Two of these populations were monitored over two consecutive flowering seasons. In spatial repartition analyses, albino individuals did not aggregate more than green individuals. Genetic analyses revealed that, in all sampled populations, albino individuals did not represent a unique lineage, and that albinos were often closer related to green individuals than to other albinos from the same population. Genetic and spatial comparison of genets from the 2-year monitoring revealed that: (i) albinos had lower survival than green individuals; (ii) accordingly, albinos detected in the first year did not correspond to the those sampled in the second year; and (iii) with one possible exception, all examined albinos did not belong to any green genet from the same and/or from the previous year, and vice versa. Our results support a scenario of repeated insurgence of the albino phenotypes within the populations, but unsuccessful transition between the two contrasting phenotypes. Future studies should try to unravel the genetic and ecological basis of the two phenotypes. [source] | ||||||||||||||||||||||