Association between rainfall seasonality and the flowering of epiphytic plants in a Neotropical montane forest

The association between the reproductive phenology of epiphytic communities with environmental and ecological factors remains largely unexplored. Because epiphytes depend on environmental moisture, seasonal changes in moisture conditions likely act as the primary determinants of their reproductive timing. We examined whether water limitation or pollinator competition structures the flowering phenologies of an epiphytic community in a seasonal mountain forest in Costa Rica. Additionally, we addressed the environmental factors that might trigger floral induction. Using a 24‐month dataset of bimonthly flowering records from 104 species, we found high seasonality of flowering at the species level but somewhat lower seasonality at the community level. The flowering mid‐dates of most epiphytes, particularly from monocotyledonous species, occurred during the wettest months, as predicted if water limitation structures flowering. The increased moisture and nutrient availability during the rainy season give epiphytes the resources needed to complete floral development and anthesis, and later fruit and seed maturation. The observed flowering pattern of epiphytes coincides with reproductive patterns of terrestrial herbs and shrubs from seasonal tropical ecosystems, and suggests shared constraints to sexual reproduction in both ecological guilds under similar climatic conditions. In contrast, flowering patterns of congeneric epiphytes in the same pollination guild mostly did not follow the expectations of a pollinator competition scenario. Finally, we discuss the possible combined effect of precipitation, temperature, and daily insolation on floral induction of epiphytic plants.     

Reproductive phenology, life-forms, and habitats of the Venezuelan Central Plain

Reproductive phenology of 171 plant species belonging to 57 families of angiosperms was studied according to life-forms in four habitat types in a savanna-forest mosaic on the Venezuelan Central Plain. Flowering, unripe fruit, and mature fruit patterns were affected significantly according to life-forms and habitats respectively. Production of flowers, unripe fruits, and mature fruits showed marked seasonality for all habitats except for the forest. Flowering peaked during the rainy season, and fruiting peaked toward the end of the rainy season. The savanna and the disturbed area had similar proportions of species that flowered over the year. The percentage of species with unripe fruits produced throughout the year was more seasonal for the disturbed area than for the other habitats. Mature fruit patterns showed an increase during the late rainy season for the ecotone and savanna. A large number of herbaceous (annual and perennial) and liana species flowered during the wet season, and a smaller fraction flowered during the dry season; and trees, shrubs, and epiphytes increased flowering activity during the dry season. Unripe fruit patterns were similar to those of flowering for all life-forms, however, tree species were less seasonal. Mature fruit production by shrubs peaked in the period of maximum rainfall, while the peak for perennial herbs was in the late rainy season and the peak for annual herbs was during the transition between the rainy season and the dry season. The largest proportion of tree and liana species with ripe fruits occurred during the dry season. Differences among phenological patterns in habitats were caused mainly by life-forms and promote a wider distribution of reproductive events in habitats and overall community in the Venezuelan Central Plain.     

Exploring the causes of variation in phenology and morphology in Mediterranean geophytes: a genus-wide study of Cyclamen

The phenology and morphology of Mediterranean plants are constrained by drought in summer and cold temperatures in winter. In this study we examine how climatic factors and phylogenetic constraints have shaped variation in the phenology and morphology of 17 species of the genus Cyclamen cultivated in uniform garden conditions. We quantify the extent to which traits differ among subgenera and thus represent conserved traits within evolutionary lineages. We also explore whether leaf, flowering and seed-release phenology are correlated among species, and thus whether variation in flowering phenology results from selection on dispersal phenology. Our results show a significant influence of subgenus membership on leaf and flowering phenology but not on morphological traits or the timing of seed release. Among-species variation in foliage height, leaf size and seed mass (but not in floral traits) is correlated with chromosome number. Leaf traits show that species with a shorter vegetative period have a higher capacity for resource acquisition. Major phenological shifts, i.e. spring vs. autumn flowering and a decoupling of leaf and flower phenology in autumnal flowering species, thus occurred prior to the diversification of species in each subgenus and not as a response to selection on dispersal timing. Leaf and flowering phenology illustrate a gradient of strategies from autumn flowering in the absence of leaves (hysteranthous species) to spring flowering with fully developed foliage (synanthous species). In the former, flowering is uncoupled from resource acquisition by simultaneous photosynthesis, indicative that hysteranthy is a response to temporal unpredictability in the onset of rain after the summer drought. Our results support the idea that whereas leaf development is controlled primarily by moisture availability and secondarily by temperature, flowering is temperature dependent, above a minimum moisture threshold. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 145 , 469–484.     

Variable flowering phenology and pollinator use in a community suggest future phenological mismatch

Recent anthropogenic climate change is strongly associated with average shifts toward earlier seasonal timing of activity (phenology) in temperate-zone species. Shifts in phenology have the potential to alter ecological interactions, to the detriment of one or more interacting species. Recent models predict that detrimental phenological mismatch may increasingly occur between plants and their pollinators. One way to test this prediction is to examine data from ecological communities that experience large annual weather fluctuations. Taking this approach, we analyzed interactions over a four-year period among 132 plant species and 665 pollinating insect species within a Mediterranean community. For each plant species we recorded onset and duration of flowering and number of pollinator species. Flowering onset varied among years, and a year of earlier flowering of a species tended to be a year of fewer species pollinating its flowers. This relationship was attributable principally to early-flowering species, suggesting that shifts toward earlier phenology driven by climate change may reduce pollination services due to phenological mismatch. Earlier flowering onset of a species also was associated with prolonged flowering duration, but it is not certain that this will counterbalance any negative effects of lower pollinator species richness on plant reproductive success. Among plants with different life histories, annuals were more severely affected by flowering–pollinator mismatches than perennials. Specialized plant species (those attracting a smaller number of pollinator species) did not experience disproportionate interannual fluctuations in phenology. Thus they do not appear to be faced with disproportionate fluctuations in pollinator species richness, contrary to the expectation that specialists are at greatest risk of losing mutualistic interactions because of climate change.     

Seed structure and germination in buriti (Mauritia flexuosa), the Swamp palm

Associations of recalcitrance and dormancy are rare, and little information is available concerning the structure of seeds demonstrating this type of behavior or their ecological implications. Mauritia flexuosa is a palm tree associated with swampy environments in the Amazon rainforest and areas of Cerrado (neotropical savanna), the latter biome having marked climatic seasonality. We describe the structures and physiological aspects of the seeds and seedlings of this species to examine its adaptations to swampy environments and its germination control mechanisms, as well as the relationship between recalcitrance and dormancy in terms of reproductive success. Morphoanatomy and histochemistry of the seeds and seedlings were evaluated using standard methodologies, and the effects of temperature and operculum removal on germination were investigated. Differentiated tracheal elements in the embryo are associated with recalcitrance, and presence of numerous stomata on the embryo and the abundance of secondary metabolite compounds in the seedling indicate their adaptations to swampy environments. The inability of the embryo to overcome the resistance of the adjacent tissues determines dormancy of the physiological type, thus the removal of the operculum is an efficient method for promoting propagation. Cellular elongation in the cotyledon promotes seedling protrusion. Mobilization of endosperm reserves is achieved by symplastic flux and is associated with overcoming of dormancy by weakening the tissues adjacent to the embryo. The association between recalcitrance, which favors adaptation to swampy environments, and dormancy, which favors dispersal, is crucial for the reproductive success of this species and its broad geographical distribution.     

Marine influence controls plant phenological dynamics in Mediterranean Mexico

Aims To assess the role of moisture in phenological timing in the mediterranean coastal flora of Baja California, and specifically to assess the role of coastal fog and ocean-derived moisture in plant phenology. Moisture seems to be the primary driver of flowering times and durations at the arid end of the mediterranean-climate region, where rainfall is often sporadic (temperature and day length can be expected to play a much lesser role as they are not growth limiting). We aimed to understand: What factors drive climatic variation between sites? Are there general flowering patterns allowing us to identify phenological categories? Do flowering patterns vary in relation to site-specific weather? and most importantly, does maritime influence on weather affect flowering dynamics in coastal mediterranean ecosystems?Methods The southernmost extent of the California Floristic Province (in Baja California, Mexico) is a biological diversity hotspot of high endemism and conservation value, with two steep moisture gradients: rainfall (N–S) and coastal fogs (W–E), providing an ideal study system. We installed five weather stations across the moisture gradients, recording data hourly. We monitored flowering phenology in the square kilometer surrounding each weather station from 2010 to 2013. About 86 plant taxa were monitored across the five sites, every 6–8 weeks. Averaged climatic data is presented with general trends in flowering, and specific flowering syndromes were observed. Data for flowering intensity across the sites was analyzed using a principal components analysis.Important findings Data analysis demonstrates a general seasonal pattern in flowering times, but distinct differences in local weather and phenology between the five study sites. Three flowering syndromes are revealed in the flora: (i) water responders or spring bloomers, (ii) day-length responders or fall-blooming taxa and (iii) aseasonal bloomers with no seasonal affinity. The two moisture gradients are the strongest drivers of flowering times. Inland sites showed higher phenological variation than coastal sites where seasonality is dampened by ocean-derived moisture, which extends and buffers perennial plant phenology and is a probable driver of local endemism. Phenological controls vary globally with climate and geography; moisture is the primary driver of phenology in mediterranean climates and fog is an important climatic variable in coastal Mexico.     

Links between plant species’ spatial and temporal responses to a warming climate

To generate realistic projections of species’ responses to climate change, we need to understand the factors that limit their ability to respond. Although climatic niche conservatism, the maintenance of a species’s climatic niche over time, is a critical assumption in niche-based species distribution models, little is known about how universal it is and how it operates. In particular, few studies have tested the role of climatic niche conservatism via phenological changes in explaining the reported wide variance in the extent of range shifts among species. Using historical records of the phenology and spatial distribution of British plants under a warming climate, we revealed that: (i) perennial species, as well as those with weaker or lagged phenological responses to temperature, experienced a greater increase in temperature during flowering (i.e. failed to maintain climatic niche via phenological changes); (ii) species that failed to maintain climatic niche via phenological changes showed greater northward range shifts; and (iii) there was a complementary relationship between the levels of climatic niche conservatism via phenological changes and range shifts. These results indicate that even species with high climatic niche conservatism might not show range shifts as instead they track warming temperatures during flowering by advancing their phenology.     

Plant functional traits mediate reproductive phenology and success in response to experimental warming and snow addition in Tibet

Global climate change is predicted to have large impacts on the phenology and reproduction of alpine plants, which will have important implications for plant demography and community interactions, trophic dynamics, ecosystem energy balance, and human livelihoods. In this article we report results of a 3‐year, fully factorial experimental study exploring how warming, snow addition, and their combination affect reproductive phenology, effort, and success of four alpine plant species belonging to three different life forms in a semiarid, alpine meadow ecosystem on the central Tibetan Plateau. Our results indicate that warming and snow addition change reproductive phenology and success, but responses are not uniform across species. Moreover, traits associated with resource acquisition, such as rooting depth and life history (early vs. late flowering), mediate plant phenology, and reproductive responses to changing climatic conditions. Specifically, we found that warming delayed the reproductive phenology and decreased number of inflorescences of Kobresia pygmaea C. B. Clarke, a shallow‐rooted, early‐flowering plant, which may be mainly constrained by upper‐soil moisture availability. Because K. pygmaea is the dominant species in the alpine meadow ecosystem, these results may have important implications for ecosystem dynamics and for pastoralists and wildlife in the region.     

Phenological patterns of <Emphasis Type="Italic">Ficus citrifolia</Emphasis> (Moraceae) in a seasonal humid-subtropical region in Southern Brazil

Year-round flowering is widely reported in fig trees and is necessary for the survival of their short-living, specialized Agaonid pollinators. However, seasonality in both fig and leaf production has been noted in almost all published phenological studies. We have addressed the following questions in the present study: (1) Are reproductive and vegetative phenologies seasonal and, consequently, related to climate? (2) Does Ficus citrifolia produce ripe figs year round? (3) Is the fig development related to climate? And, (4) Are reproductive and vegetative phenologies independent? By investigating these questions with a F. citrifolia population over a two-year period, at the southern edge of the tropical region in Brazil, we detected phenological seasonality that was significantly correlated with climate. Our findings can be summarized as follows: (1) Trees became deciduous during the cold and dry months; (2) The flowering onset was asynchronous among individuals, but with moderate concentration during the hot and rainy months; (3) There was a correlation between the onset of flowering and vegetative phenology, with significantly higher crop initiations in individuals with full-leaf canopy; (4) Fig developmental time was longer in cold months; and (5) Ripe fig production occurred year-round and was not correlated with climate. Our results suggest that there are strong selection pressures that maintain the year-round flowering phenology in figs, for we have observed little seasonality in the phenology of such species despite the strong seasonality in the environment.     

Flowering and Fruiting Patterns in a Subtropical Rain Forest,Taiwan

Reproductive patterns of tropical and temperate plants are usually associated with climatic seasonality, such as rainfall or temperature, and with their phylogeny. It is still unclear, however, whether plant reproductive phenology is influenced by climatic factors and/or phylogeny in aseasonal subtropical regions. The plant reproductive phenology of a subtropical rain forest in northern Taiwan (24°45′ N, 121°35′ E) was monitored at weekly intervals during a 7‐yr period (2002–2009). The flowering patterns of 46 taxa and fruiting patterns of 26 taxa were examined and evaluated in relation to climatic seasonality, phylogenetic constraints, and different phenophases. Our results indicated that most of the studied species reproduced annually. Additionally, both community‐wide flowering and fruiting patterns exhibited distinct annual rhythms and varied little among years. The community flowering peak matched seasonal changes in day length, temperature, and irradiance; while the community fruiting peak coincided with an increase in bird richness and the diet‐switching of resident omnivorous birds. In addition, phylogenetically closely related species tended to reproduce during the same periods of a year. Neither the mean flowering dates nor seasonal variation in solar radiation, however, was related to the fruit development times. Our results indicate the importance of abiotic, biotic, and evolutionary factors in determining the reproductive phenology in this subtropical forest.     

Habitat preferences as related to the prolonged dormancy of perennial herbs and ferns

Prolonged dormancy (hereafter dormancy), a phenomenon in which a perennial herbaceous plant does not sprout for one or more years, is examined. The phenomenon may be more frequent than stated so far and discovery of its role in plant life history and performance is still underway. Data from published papers was reviewed and all known species exhibiting dormancy were analysed from the aspect of species ecological values. Adaptation to environmental factors (light, moisture, pH and nitrogen as estimated by Ellenberg indicator values) influences the maximum duration of dormancy. A higher proportion of plants are dormant in species that prefer to grow in good light conditions, dry sites and infertile soil. The duration of dormant period is longer in species that prefer to grow in dry sites and/or calcareous soils. A range of factors, we believe, control plant behaviour, however, it is suggested that environmental stress is the principal factor inducing dormancy.     

Flowering phenology and reproduction of a forest understorey plant species in response to the local environment

Temperate forest understorey plants are subjected to a strong seasonality in their optimal growing conditions. In winter and early spring, low temperatures are suboptimal for plant growth while light becomes limited later in spring season. We can thus expect that differences in plant phenology in relation to spatiotemporal environmental variation will lead to differences in reproductive output, and hence selection. We specifically studied whether early flowering, a paradoxical pattern that is observed in many plant species, is an adaptive strategy, and whether selection for early flowering was confounded with selection for flower duration or was attributable to environmental variables. We used Geum urbanum as a study species to investigate the effect of relevant environmental factors on the species’ flowering phenology and the consequences for plant reproductive output. We monitored the phenology of four to six plants in each of ten locations in a temperate deciduous forest (Belgium). We first quantified variation in flowering time within individuals and related this temporal variation to individual flower reproductive output. Then, we studied inter-individual variation here-in and linked this to reproduction at the plant level, hence studying the selection differential. We found that flowering within individual plants of Geum urbanum was spread over a long period from June to October. Reproductive output of individual flowers, measured as total seed mass per flower, declined during the season. We found no indication for selection for early flowering but rather for longer flower duration. Larger plants had an earlier flowering onset and a higher seed mass, which suggests that these factors covary and are condition dependent. None of the studied environmental variables could explain plant size, although soil pH and to a lesser extent light availability had a positive direct effect on seed mass per plant. Finally, we suggest that the high intra-individual variation in flowering time, which might be a risk spreading strategy of the plant in the presence of seed predation, limits the potential for selection on flowering phenology.

     

Understanding chilling responses in Arabidopsis seeds and their contribution to life history

Winter chilling is of central importance in the phenology of temperate annual and perennial plants. Chilling accelerates flowering through the process of vernalization and breaks both bud and seed dormancy, permitting the onset of growth in the spring. The quantitative effects of chilling in floral promotion in winter annual Arabidopsis accessions are well-documented, but very little is known about the basic physiology underlying summer annual responses to winter chilling, which acts on seeds within the soil seed bank. Here, we analyse the response of wild accessions to extended chilling in seeds, and explore the interaction between seed-maturation temperature and chilling responses. We show that two weeks of chilling induces secondary dormancy, and that this time period is not dependent on seed-maturation temperature. In addition, we found that seeds for most accessions set under simulated summer conditions in the laboratory are unable to overwinter in the soil seed bank, as they germinate without light during extended chilling treatments. This shows that these seeds are committed to re-establishment in the same growing season. Understanding how winter chilling affects the timing of Arabidopsis phenology will enable us to explore the genetics behind adaptation to changing climates, and inform rational approaches to breeding crops with improved performance under new climate scenarios and develop a systems ecology of Arabidopsis.     

Burning grasses,poor seeds: post-fire reproduction of early-flowering Neotropical savanna grasses produces low-quality seeds

Fire is a key factor triggering ecological processes in old-growth grasslands and savannas and could have strong implications for reproduction via seeds for the herbaceous layer. In the Neotropical savannas, grasses show strong synchronous post-fire flowering, and their reproduction is often considered fire-dependent, with their massive post-fire seed production being suggested as a source of population maintenance. However, literature lacks studies to provide evidence of fire-dependent flowering and no study has assessed the quality of the post-fire seed production. Therefore, we aimed to describe a phenological pattern across early-flowering Neotropical savanna grasses in both recently burnt and unburnt cerrado communities addressing three questions: (1) Do the early-flowering species rely on fire for reproduction via seeds? (2) If no, what are the effects of fire on their reproductive phenology? (3) Does the massive seed production in post-fire cerrado communities lead to high-quality seeds? We recorded the reproductive phenology of nine early-flowering grasses for 17 weeks in unburnt and recently burnt cerrado communities. We collected the seeds, estimated the production of fertile seeds, and tested germination. No species showed a pattern of fire-dependent reproduction. Fire stimulated earlier flowering while reproduction in the unburnt community was related to continuous rainfall. Seed production following fire was of low quality, and no species produced?>?7% fertile seeds. Seed germination remained below 50% for most species. Post-fire seed production of early-flowering species led to poor seed quality, suggesting a constraint to the recruitment of new individuals of early-flowering Neotropical savanna grasses in recently burnt cerrados.

     

Male-biased sex allocation in late-blooming flowers driven by resource limitation in the clonal perennial Aconitum kusnezoffii (Ranunculaceae)

Flowering phenology and clonal growth are known to affect resource and pollen availability, and therefore select for adaptive or constrained sex allocation strategies to some degree. However, the consequences of temporal sex allocation patterns for reproductive fitness across the flower, inflorescence, and genet levels have rarely been examined. Moreover, experimental tests of the underlying regulatory mechanisms are scarce. We examined the association of flowering phenology and inflorescence position with temporal sex allocation and reproductive success in the protandrous perennial clonal herb, Aconitum kusnezoffii, over four consecutive growing seasons by examining more than 39 000 flowers. We also conducted controlled experiments to test the effects of resource and pollen limitation on the female reproductive success of lateral inflorescences. We found that some male functions were positively correlated with flowering phenology, whereas female reproductive success was negatively correlated with flowering phenology and inflorescence position. Lateral inflorescences invested more in male function than terminal inflorescences and therefore yielded fewer and smaller seeds. Resource limitation may serve as the key mechanism underlying this differentiated pattern. Decreased female reproductive success was consistently observed at the flower and inflorescence levels as flowering occurred later in the growth season. Late-blooming lateral inflorescences specialized in the male function, and their female reproductive success was constrained by early-blooming terminal inflorescences. This might be the first attempt to systematically demonstrate sex allocation strategy differentiation in a protandrous plant species at the inflorescence level. In addition, our study provides empirical evidence of dichogamy selecting for specialized sex allocation strategies among inflorescences.     

Distribution of seed dormancy classes across a fire-prone continent: effects of rainfall seasonality and temperature

Background and AimsDifferent seed dormancy classes control the timing of germination via different cues. The ecological dissimilarities between classes therefore suggest that they are likely to be subject to different selective pressures, and that species within each class will have diverse functional responses. We aimed to investigate this by assessing how variation in the distribution of dormancy classes is correlated with regional environmental factors, in particular rainfall seasonality and temperature. Additionally, we compare the relative proportions of species with physiological (PD) or physical (PY) dormancy to assess whether dormancy class influences their ability to persist under different rainfall seasonality regimes.MethodsDormancy class was assigned for 3990 species from 281 genera occurring across two climate regions, with either winter or aseasonal rainfall, across temperate fire-prone Australia. All regions have similar vegetation and fire regimes. Using a Bayesian framework, we compared the distribution of dormancy classes across temperature and rainfall climate gradients, for threatened and common species.Key ResultsA high dormant:non-dormant species ratio highlighted the critical role of dormancy across our study regions. Critically, species showing PD were more likely to be threatened in aseasonal rainfall climate regions.ConclusionsOur results support the assumption that dormancy is favoured in environments with stochastic disturbance     

Predicting a change in the order of spring phenology in temperate forests

The rise in spring temperatures over the past half‐century has led to advances in the phenology of many nontropical plants and animals. As species and populations differ in their phenological responses to temperature, an increase in temperatures has the potential to alter timing‐dependent species interactions. One species‐interaction that may be affected is the competition for light in deciduous forests, where early vernal species have a narrow window of opportunity for growth before late spring species cast shade. Here we consider the Marsham phenology time series of first leafing dates of thirteen tree species and flowering dates of one ground flora species, which spans two centuries. The exceptional length of this time series permits a rare comparison of the statistical support for parameter‐rich regression and mechanistic thermal sensitivity phenology models. While mechanistic models perform best in the majority of cases, both they and the regression models provide remarkably consistent insights into the relative sensitivity of each species to forcing and chilling effects. All species are sensitive to spring forcing, but we also find that vernal and northern European species are responsive to cold temperatures in the previous autumn. Whether this sensitivity reflects a chilling requirement or a delaying of dormancy remains to be tested. We then apply the models to projected future temperature data under a fossil fuel intensive emissions scenario and predict that while some species will advance substantially others will advance by less and may even be delayed due to a rise in autumn and winter temperatures. Considering the projected responses of all fourteen species, we anticipate a change in the order of spring events, which may lead to changes in competitive advantage for light with potential implications for the composition of temperate forests.     

澳门九澳山海滨群落10种植物盛花期物候对极端气候事件的响应

为探究极端气候事件对植物的影响,对澳门九澳山海滨群落10种植物2012-2017年盛花期物候进行了观察。结果表明,植物的盛花期一般在3-9月,其中有4种植物为5月。2013和2016年早春澳门的极端强降水使植物的盛花期出现了明显的提前或者推迟。9种植物的盛花期与盛花期前0～2个月和上一年的秋冬季的月均温度或月降水存在显著相关性。温度和降水对植物盛花期的影响差异不大,但晚花植物对降水更加敏感。这为澳门和邻近岛屿的生态恢复和园林树种选材提供参考。     

Continental-scale patterns of Cecropia reproductive phenology: evidence from herbarium specimens

Plant phenology is concerned with the timing of recurring biological events. Though phenology has traditionally been studied using intensive surveys of a local flora, results from such surveys are difficult to generalize to broader spatial scales. In this study, contrastingly, we assembled a continental-scale dataset of herbarium specimens for the emblematic genus of Neotropical pioneer trees, Cecropia, and applied Fourier spectral and cospectral analyses to investigate the reproductive phenology of 35 species. We detected significant annual, sub-annual and continuous patterns, and discuss the variation in patterns within and among climatic regions. Although previous studies have suggested that pioneer species generally produce flowers continually throughout the year, we found that at least one third of Cecropia species are characterized by clear annual flowering behaviour. We further investigated the relationships between phenology and climate seasonality, showing strong associations between phenology and seasonal variations in precipitation and temperature. We also verified our results against field survey data gathered from the literature. Our findings indicate that herbarium material is a reliable resource for use in the investigation of large-scale patterns in plant phenology, offering a promising complement to local intensive field studies.