Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Phenology

  • breeding phenology
  • floral phenology
  • flowering phenology
  • fruiting phenology
  • leaf phenology
  • plant phenology
  • reproductive phenology
  • seasonal phenology
  • vegetative phenology

  • Terms modified by Phenology

  • phenology trait

  • Selected Abstracts


    EVOLUTION, Issue 12 2007
    David Hall
    A correct timing of growth cessation and dormancy induction represents a critical ecological and evolutionary trade-off between survival and growth in most forest trees (Rehfeldt et al. 1999; Horvath et al. 2003; Howe et al. 2003). We have studied the deciduous tree European Aspen (Populus tremula) across a latitudinal gradient and compared genetic differentiation in phenology traits with molecular markers. Trees from 12 different areas covering 10 latitudinal degrees were cloned and planted in two common gardens. Several phenology traits showed strong genetic differentiation and clinal variation across the latitudinal gradient, with QST values generally exceeding 0.5. This is in stark contrast to genetic differentiation at several classes of genetic markers (18 neutral SSRs, 7 SSRs located close to phenology candidate genes and 50 SNPs from five phenology candidate genes) that all showed FST values around 0.015. We thus find strong evidence for adaptive divergence in phenology traits across the latitudinal gradient. However, the strong population structure seen at the quantitative traits is not reflected in underlying candidate genes. This result fit theoretical expectations that suggest that genetic differentiation at candidate loci is better described by FST at neutral loci rather than by QST at the quantitative traits themselves. [source]

    Phenology determines seasonal variation in ectoparasite loads in a natural insect population

    1. The extent to which individuals are parasitised is a function of exposure to parasites and the immune response, which in ectotherms may be associated with temperature. 2. We test the hypothesis that seasonal variation in ectoparasite burden is driven by temperature using an extensive mark-release-recapture study of adult Coenagrion puella (L.) (Zygoptera) as a model system. Mite counts were taken both at capture and on a subset of subsequent recaptures over two entire, consecutive breeding seasons. 3. Emergence date was the most significant factor in determining individual differences in mite burden, and mean counts for individuals emerging on the same days showed strong unimodal relationships with time of season. Subsequent recounting of mites on a subset of individuals showed that patterns of loss of mites were similar between seasons. 4. While temperature did not significantly affect mite burdens within seasons and ectoparasite prevalence was very similar across the two seasons, intensity of infection and rate of mite gain in unparasitised individuals were significantly higher in the cooler season. 5. We demonstrate that, while temperature may modulate the invertebrate immune response, this modulation does not manifest in variations in mite burdens in natural populations. [source]

    Host shifting by Operophtera brumata into novel environments leads to population differentiation in life-history traits

    Adam J. Vanbergen
    Abstract., 1. Operophtera brumata L. (Lepidoptera: Geometridae), a polyphagous herbivore usually associated with deciduous trees such as oak Quercus robur L., has expanded its host range to include the evergreen species heather Calluna vulgaris (L.) Hull and, most recently, Sitka spruce Picea sitchensis (Bong.) Carrière. 2. Phenology, morphology, and survival of O. brumata were measured at several life-history stages in populations from the three different host plant communities sampled from a range of geographical locations. The data were used to test for population differences, reflecting the marked differences in host-plant secondary chemistry, growth form, and site factors such as climate. The hypothesis that spruce-feeding populations originated from populations feeding on moorland, commonly sites of coniferous afforestation, was also tested. 3. Altitude, not host plant species, was the major influence on the timing of adult emergence. An effect of insect population independent of altitude was found, implying that additional unidentified factors contribute to this phenological variation. Larval survival and adult size varied between populations reared on different host plant species. Survival of larvae was affected negatively when reared on the novel host plant, Sitka spruce, versus the natal plant (oak or heather) but oak and heather-sourced insects did not differ in survivorship on Sitka spruce. 4. Host range extension into novel environments has resulted in population differentiation to the local climate, demonstrating that host shifts pose challenges to the herbivore population greater than those offered by the host plant alone. The hypothesis that Sitka spruce feeding populations have arisen predominantly from moorland feeding populations was not supported. [source]

    Phenology, ontogeny and the effects of climate change on the timing of species interactions

    ECOLOGY LETTERS, Issue 1 2010
    Louie H. Yang
    Abstract Climate change is altering the phenology of many species and the timing of their interactions with other species, but the impacts of these phenological shifts on species interactions remain unclear. Classical approaches to the study of phenology have typically documented changes in the timing of single life-history events, while phenological shifts affect many interactions over entire life histories. In this study, we suggest an approach that integrates the phenology and ontogeny of species interactions with a fitness landscape to provide a common mechanistic framework for investigating phenological shifts. We suggest that this ontogeny,phenology landscape provides a flexible method to document changes in the relative phenologies of interacting species, examine the causes of these phenological shifts, and estimate their consequences for interacting species. Ecology Letters (2010) 13: 1,10 [source]

    Phenology and climate: the timing of life cycle events as indicators of climatic variability and change

    Arnold J. H. van Vliet
    No abstract is available for this article. [source]

    Factors Influencing the Seasonal Phenology and Composition of Zooplankton Communities in Mountain Temporary Pools

    Silvia Tavernini
    Abstract In 2001 nine temporary pools of the northern Apennines (Italy) were visited on 13 occasions during the ice-free season (May to October). The aims of this research were to define the relationships between hydroperiod and other environmental variables and the zooplankton. In total, 49 zooplankton taxa were identified: 36 rotifers, 5 cladocerans, 6 copepods and 2 anostracans. Our results indicate that hydroperiod is a major determinant affecting zooplankton species richness. The highest number of taxa was found in the pond having the longest duration. Distinctive species assemblages were observed in different habitat types: pools with the shortest hydroperiod were characterised by organisms with brief life cycles (e.g. rotifers) and/or typical of temporary habitat (e.g. anostracans). Of the physical and chemical characteristics, pH and chlorophyll- a appeared to have the largest influence on zooplankton distribution in the studied pools. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Phenology of fine roots and leaves in forest and grassland

    JOURNAL OF ECOLOGY, Issue 6 2008
    Diego F. Steinaker
    Summary 1The phenology of temperate vegetation is advancing in association with climate warming. Most phenology data, however, comes from flowers and tree leaves. We tested the generality of results from shoot phenology by expanding data collection in two new directions. We related forest leaf phenology to root phenology, and to phenology in a second habitat, grassland. 2We measured leaf and root phenology simultaneously in aspen forest and adjacent native grassland. Root growth accounts for 80,90% of productivity in these habitats. Seasonal variation in soil moisture and temperature were also measured. 3Forest leaf production was greatest about 45 days before peak root production, resulting in a significant negative correlation between leaf and root production in forest. Grassland leaf production was greatest about 15 days before peak root production, and grassland leaf and root production were significantly positively correlated. The duration of root production was 40% greater than that of shoot production. 4Forest leaf production increased significantly with increasing soil moisture, but not temperature. In contrast, the production of forest roots, grassland roots and grassland leaves increased significantly with soil temperature. 5Synthesis. The most commonly measured aspect of phenology, forest leaves, is out of step with the majority of production in forest, as well as phenology in grassland. The invasion of grassland by woody vegetation is characterized by a decoupling of root and shoot phenology, a result that has not been reported previously. Given the global nature of woody plant encroachment, this decoupling may influence our general understanding of productivity and carbon sequestration in response to warming. [source]

    Energy density patterns of nectar resources permit coexistence within a guild of Neotropical flower-visiting bats

    JOURNAL OF ZOOLOGY, Issue 1 2004
    Marco Tschapka
    Abstract Neotropical rainforests support guilds of nectar feeding bats (Phyllostomidae: Glossophaginae) with up to six coexisting species. To analyse guild structure and mechanisms of coexistence in a Costa Rican tropical lowland rainforest, the resource use and morphology of bats were compared to the energetic characteristics of preferred nectar resources and their spatio-temporal distribution. The relative abundance of nectar-feeding bats was determined from mistnet captures over 26 months. Food items were identified by analysis of pollen loads and faecal samples. Phenology, flower density and nectar sugar content of resource plants permitted quantitative estimations of resource availability expressed as energy density (kJ ha,1 day,1) throughout the annual cycle. Four glossophagine bat species co-occurred at La Selva: two permanent residents (Glossophaga commissarisi, Hylonycteris underwoodi) and two seasonal species (Lichonycteris obscura, Lonchophylla robusta) that were found in small numbers during a period of high nectar availability. The two resident species differed in their abundance and in their temporal feeding strategies. After the main flowering peak, the common G. commissarisi shifted to a more frugivorous diet, while the rarer H. underwoodi fed on the few remaining bat-flowers. Resource plant species differed in their energy density by up to two orders of magnitude. Hylonycteris underwoodi visited more often plant species with a low energy yield than G. commissarisi. Because of its smaller body size and a wing morphology that promotes fast flight, H. underwoodi appears to be better adapted to low and scattered nectar resource levels. The two seasonal species differed greatly in body mass, which suggests different strategies for high-quality resource tracking. Large body mass in Lonchophylla robusta provides an energy buffer that permits daily commuting flights between a permanent roost and profitable foraging areas, while the small Lichonycteris obscura seems to track resources nomadically. It is proposed that energy density may be a major niche dimension that restricts access of species to certain habitats and that may profoundly influence the structure of nectar-feeding bat guilds. [source]

    Phenology of the environmental weed Achillea millefolium (Asteraceae) along altitudinal and disturbance gradients in the Snowy Mountains, Australia

    Frances Mary Johnston
    This study examined the phenology of the weed Achillea millefolium over a growing season in the Snowy Mountains. Vegetative and reproductive characteristics of plants in 1 m2 quadrats were compared among sites at four different altitudes (medium and high montane, low and high subalpine) and three types of infrastructure (primary road, secondary road and building, total 12 sites). Altitude, infrastructure and time of year did not affect percentage cover of vegetation. Flowering started earlier and lasted longer in the low montane sites compared to high subalpine sites. The type of infrastructure only affected the number of reproductive structures at the peak of flowering, with A. millefolium growing next to buildings having two to three times more inflorescences per m2 than along primary and secondary road verges. At the peak for each reproductive stage, there was an average of 1.47 developing inflorescences, 21 inflorescences in bud, 24 inflorescences in flower, 4 inflorescences setting seed, and 3 releasing seed. Based on the maximum number of inflorescences present at any time at each site, there was an average of 36 inflorescences, giving an estimate potential seed production of 51 400 seed per one m2 for A. millefolium in the Snowy Mountains. If the climate changes in the Snowy Mountains as predicted, then it is likely that yarrow will produce more inflorescences and seed in the higher altitude sites. [source]

    Phenology of neotropical pepper plants (Piperaceae) and their association with their main dispersers, two short-tailed fruit bats, Carollia perspicillata and C. castanea (Phyllostomidae)

    OIKOS, Issue 2 2004
    Wibke Thies
    To relate differences in phenological strategies of a group of closely related plants to biotic (pollinators, dispersers) and abiotic (water, light) factors, we studied leafing, flowering, and fruiting phenology of 12 species of Piper (Piperaceae) in a neotropical lowland forest in Panama for 28 months. We asked how Piper may partition time and vertebrate frugivores to minimize possible competition for dispersal agents. Based on habitat preferences and physiological characteristics we discriminate between forest Piper species (eight species) and gap Piper species (four species). Forest Piper species flowered synchronously mostly at the end of the dry season. Gap Piper species had broader or multiple flowering peaks distributed throughout the year with a trend towards the wet season. Both groups of Piper species showed continuous fruit production. Fruiting peaks of forest Piper species were short and staggered. Gap Piper species had extended fruiting seasons with multiple or broad peaks. Both groups of Piper species also differed in their time of ripening and disperser spectrum. Forest Piper species ripened in late afternoon and had a narrow spectrum consisting mainly of two species of frugivorous bats: Carollia perspicillata and C. castanea (Phyllostomidae). Fruits of gap Piper species, in contrast, ripened early in the morning and were eaten by a broader range of diurnal and nocturnal visitors, including bats, birds, and ants. We conclude that the differences in flowering phenology of forest and gap Piper species are primarily caused by abiotic factors, particularly the availability of water and light, whereas differences in fruiting patterns are mostly influenced by biotic factors. The staggered fruiting pattern of forest Piper species may reflect competition for a limited spectrum of dispersers. The long and overlapping fruiting periods of gap Piper species are associated with a larger spectrum of dispersers and may be a strategy to overcome the difficulty of seed dispersal into spatially unpredictable germination sites with suitable light conditions. [source]

    Seed Dispersal Phenology and Germination Characteristics of a Drought-Prone Vegetation in Southeastern Brazil

    BIOTROPICA, Issue 3 2010
    Maria Isabel Guedes Braz
    ABSTRACT Seed germination is determined by the environmental conditions typical of a habitat and also by the geographical origin of the source species pool. During the Quaternary, Brazilian Atlantic Rain Forest species expanded their distribution into the sandy coastal plains (restingas). Periods of water shortage, however, are frequent in the sandy substrate of the restinga. We investigated whether the germination characteristics of restinga species are more related to their biogeographical origin in the humid forest or to water shortage on sandy substrates. We characterized the seed dispersal phenology of a restinga community and conducted experiments to determine the water requirements for seed germination and the short-term seed dehydration sensitivity of different species. Species shed seeds throughout the year in the restinga. When subjected to ,=,0.37 MPa, seed germination percentage decreased and germination time increased in six of ten species when compared with ,=0 MPa. Most species showed high seed moisture content (MC>40 %) at seed dispersal. Seeds took 3,17 d to dehydrate when subjected to relative humidity,76 percent and only two of eight species had seeds sensitive to short-term dehydration. Thus, rather than a specific set of germination characteristics related to humid or dry habitats, we gathered evidence to show that the germination characteristics of restinga species represent a multiplicity of responses that may be found in both kinds of habitat. Abstract in Portuguese is available at [source]

    Staggered Flowering in Four Sympatric Varieties of Geonoma cuneata (Palmae),

    BIOTROPICA, Issue 4 2002
    Finn 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]

    Modification of Vegetative Phenology in a Tropical Semi-deciduous Forest by Abnormal Drought and Rain,

    BIOTROPICA, Issue 1 2002
    R. Borchert
    ABSTRACT The control of vegetative phenology in tropical trees is not well understood. In dry forest trees, leaf abscission may be enhanced by advanced leaf age, increasing water stress, or declining photoperiod. Normally, it is impossible to dissect the effects of each of these variables because most leaves are shed during the early dry season when day length is near its minimum and leaves are relatively old. The 1997 El-Niño Southern Oscillation caused a ten-week long, severe abnormal drought from June to August in the semi-deciduous forests of Guanacaste, Costa Rica. We monitored the effect of this drought on phenology and water status of trees with young leaves and compared modifications of phenology in trees of different functional types with the pattern observed during the regular dry season. Although deciduous trees at dry sites were severely water stressed (,stem < -7MPa) and their mesic leaves remained wilted for more than two months, these and all other trees retained all leaves during the abnormal drought. Many trees exchanged leaves three to four months earlier than normal during the wet period after the abnormal drought and shed leaves again during the regular dry season. Irrigation and an exceptional 70 mm rainfall during the mid-dry season 1998/1999 caused bud break and flushing in all leafless trees except dormant stem succulents. The complex interactions between leaf age and water stress, the principal determinants of leaf abscission, were found to vary widely among trees of different functional types. [source]

    Phenology of Atlantic Rain Forest Trees: A Comparative Study,

    BIOTROPICA, Issue 4b 2000
    L. Patnicia C. Morellato
    ABSTRACT This paper describes the phenology of leaf, flower, and fruit phenology in the Atlantic rain forests of southeastern Brazil. For 17 months, we observed the phenological patterns of trees from two Atlantic forest types at four sites: premontane forest (Sites I and IV; the "typical" Atlantic rain forest) and coastal plain forest (Sites II and III). All sites experience a nonseasonal, tropical wet climate, characterized by an annual rainfall usually > 2000 mm and lacking a dry season. We tested for the occurrence (or absence) of seasonal phenological patterns within each site and compared the patterns detected among the four different forest sites using circular statistics. The expected weakly seasonal phenological patterns were not observed for these forests. Flowering and leaf flush patterns of Atlantic rain forest trees were significantly seasonal, concentrated at the beginning of the wettest season, and were significantly correlated with day length and temperature. These results stress the influence that seasonal variation in day length has on ever-wet forest tree phenology. Fruiting phenologies were aseasonal in all four forests. Flowering patterns did not differ significantly among three of the four forest sites analyzed, suggesting the occurrence of a general flowering pattern for Atlantic rain forest trees. RESUMO Este estudo descreve, pela primeira vez, a fenologia reprodutiva (flora¸ão e frutifica¸ão) e a mudan¸a foliar em floresta pluvial atlãntica do sudeste do Brasil. Durante 17 meses foi observada a fenologia das árvores de dois tipos de floresta atlãntica: a floresta atlãntica de encosta (áreas I e IV; Floresta atlãntica "típica") e floresta de planície (áreas II c III). Todas ás áreas estão sob clima não-sazonal, tropical úmido, caracterizado por precipita¸ão anual geralmente superior a 2000 mm e ausência de esta¸ão seca. Foi testada a ocorrência (ou ausência) de padrões fenológicos sazonais dentro de cada área e comparados os padrões detectados entre as quatro diferentes áreas de floresta utilizando-se da análise estatística circular. O padrão fenológico fracamente sazonal, esperado neste tipo de vegeta¸ão, não foi observado para as florestas estudadas. A flora¸ão e o brotamento foram significativamente sazonais, concentrados durante o início da esta¸ão úmida, e apresentaram correla¸ão significativa com o comprimento do dia e temperatura. Estes resultados expressam a importãncia da luz na fenologia de árvores tropicais sob clima pouco sazonal. A frutifica¸ão não apresentou padrão sazonal para todas as áreas de floresta analisadas. Os padrões de flora¸ão não diferiram significativamente entre três das quatro áreas de floresta analisadas, sugerindo a ocorrência de um padrão de flora¸ão geral para as árvores de floresta atlãntica. [source]

    Reproductive Phenology of a Tropical Canopy Tree, Spondias mombin,

    BIOTROPICA, Issue 4a 2000
    Gregory H. Adler
    ABSTRACT We studied the reproductive phenology of isolated populations of Spondias mombin to determine the degree of flowering and fruiting synchrony among populations and to examine spatial and temporal variability in fruit production. The study was conducted on six small islands (1.8,3.5 ha) in the Panama Canal. All individuals (10 cm in diameter at breast height (DBH) were marked in 1991 and censused each year through 1994 to record recruits and deaths. All marked trees were censused monthly for flowering and fruiting activity from April 1992 through December 1995. Spondias mombin was seasonal and highly synchronous in flower and fruit production among islands and across years. Proportions of individuals fruiting varied among islands, years, and tree size classes. There was a positive relationship between probability of fruit production and tree size. Synchronous reproductive activity in S. mombin probably was due to responses to proximate environmental cues such as fluctuations in irradiance, but other factors must have been responsible for temporal and spatial variation in reproductive performance. We suggest that this variation may have been due partly to temporal and spatial differences in pollinator abundance. [source]

    Runoff and soil loss under individual plants of a semi-arid Mediterranean shrubland: influence of plant morphology and rainfall intensity

    E. Bochet
    Abstract The influence of plant morphology and rainfall intensity on soil loss and runoff was determined at the plant scale for three representative species of a semi-arid patchy shrubland vegetation of east Spain, representing contrasting canopy structures and plant phenologies (Rosmarinus officinalis, Anthyllis cytisoides and Stipa tenacissima). Twenty-seven microplots of less than 1 m2, each containing one single plant, were built to quantify runoff volume and sediment yield under the canopies of the three species. Runoff and rates of soil loss measured in these plots under natural rainfall conditions were compared with control microplots built in the bare inter-plant areas. Precipitation was automatic-ally recorded and rainfall intensity calculated over a two-year period. Results indicated that individual plants played a relevant role in interrill erosion control at the microscale. Compared with a bare soil surface, rates of soil loss and runoff reduction varied strongly depending on the species. Cumulative soil loss was reduced by 94·3, 88·0 and 30·2 per cent, and cumulative runoff volume was reduced by 66·4, 50·8 and 18·4 per cent under the Rosmarinus, Stipa and Anthyllis canopies, respectively, compared with a bare surface. Anthyllis was significantly less efficient than the two other species in reducing runoff volume under its canopy. Differences between species could only be identified above a rainfall intensity threshold of 20 mm h,1. The different plant morphologies and plant compon-ents explained the different erosive responses of the three species. Canopy cover played a major role in runoff and soil loss reduction. The presence of a second layer of protection at the soil surface (litter cover) was fundamental for erosion control during intense rainfall. Rainfall intensity and soil water status prior to rainfall strongly influenced runoff and soil loss rates. The possible use of these species in restoration programmes of degraded areas is discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Phenology, ontogeny and the effects of climate change on the timing of species interactions

    ECOLOGY LETTERS, Issue 1 2010
    Louie H. Yang
    Abstract Climate change is altering the phenology of many species and the timing of their interactions with other species, but the impacts of these phenological shifts on species interactions remain unclear. Classical approaches to the study of phenology have typically documented changes in the timing of single life-history events, while phenological shifts affect many interactions over entire life histories. In this study, we suggest an approach that integrates the phenology and ontogeny of species interactions with a fitness landscape to provide a common mechanistic framework for investigating phenological shifts. We suggest that this ontogeny,phenology landscape provides a flexible method to document changes in the relative phenologies of interacting species, examine the causes of these phenological shifts, and estimate their consequences for interacting species. Ecology Letters (2010) 13: 1,10 [source]

    Short and long term consequences of increases in exotic species richness on water filtration by marine invertebrates

    ECOLOGY LETTERS, Issue 8 2009
    Jarrett Byrnes
    Abstract Although recent research has considered the consequences of global declines in the number of species, less attention has focused on the aggregate effects of regional increases in species richness as a result of human-mediated introductions. Here we examine several potential ecosystem consequences of increasing exotic species diversity of suspension feeding marine invertebrates. First, we experimentally manipulated native and non-native suspension feeder richness and measured its effect on short-term phytoplankton clearance rates. Multispecies communities all performed similarly, regardless of whether they were dominated by natives, exotics, or an even mix of the two. Individual species varied considerably in filtration rates, but non-native species often filtered less than the most similar native. Second, we determined potential changes in integrated function over time by comparing seasonal patterns of recruitment as a proxy for the ability to quickly recover filtration capacity after a disturbance. We found that exotic species have complementary seasonal phenologies both to native species and each other. Our results suggest that the consequences of local increases in species richness due to invasions may be manifest over long (annual to interannual) time scales, even when short term changes in ecosystem function are negligible. [source]


    EVOLUTION, Issue 11 2007
    S. S. Renner
    The northern hemisphere tree genus Acer comprises 124 species, most of them monoecious, but 13 dioecious. The monoecious species flower dichogamously, duodichogamously (male, female, male), or in some species heterodichogamously (two morphs that each produce male and female flowers but at reciprocal times). Dioecious species cannot engage in these temporal strategies. Using a phylogeny for 66 species and subspecies obtained from 6600 nucleotides of chloroplast introns, spacers, and a protein-coding gene, we address the hypothesis (Pannell and Verdú, Evolution 60: 660,673. 2006) that dioecy evolved from heterodichogamy. This hypothesis was based on phylogenetic analyses (Gleiser and Verdú, New Phytol. 165: 633,640. 2005) that included 29,39 species of Acer coded for five sexual strategies (duodichogamous monoecy, heterodichogamous androdioecy, heterodichogamous trioecy, dichogamous subdioecy, and dioecy) treated as ordered states or as a single continuous variable. When reviewing the basis for these scorings, we found errors that together with the small taxon sample, cast doubt on the earlier inferences. Based on published studies, we coded 56 species of Acer for four sexual strategies, dioecy, monoecy with dichogamous or duodichogamous flowering, monoecy with heterodichogamous flowering, or labile sex expression, in which individuals reverse their sex allocation depending on environment,phenotype interactions. Using Bayesian character mapping, we infer an average of 15 transformations, a third of them involving changes from monoecy-cum-duodichogamy to dioecy; less frequent were changes from this strategy to heterodichogamy; dioecy rarely reverts to other sexual systems. Contra the earlier inferences, we found no switches between heterodichogamy and dioecy. Unexpectedly, most of the species with labile sex expression are grouped together, suggesting that phenotypic plasticity in Acer may be a heritable sexual strategy. Because of the complex flowering phenologies, however, a concern remains that monoecy in Acer might not always be distinguishable from labile sex expression, which needs to be addressed by long-term monitoring of monoecious trees. The 13 dioecious species occur in phylogenetically disparate clades that date back to the Late Eocene and Oligocene, judging from a fossil-calibrated relaxed molecular clock. [source]

    Terrestrial invertebrates inhabiting lowland river floodplains of Central Amazonia and Central Europe: a review

    FRESHWATER BIOLOGY, Issue 4 2002
    1.,Amazonian terrestrial invertebrates produce high population densities during favourable periods and may suffer a drastic decrease during occasional floods and droughts. However, the monomodal, predictable flood pulse of the larger Amazonian rivers favours the development of morphological (respiratory organs, wing-dimorphism), phenological (synchronization of life cycles, univoltine mode of life), physiological (flooding ability, gonad dormancy, alternating number of developmental stages), and behavioural adaptations (migration, temporal diving) with numerous interactions. 2.,In lowlands of Central Europe, the flood pulse of large rivers is less predictable than in Central Amazonia and is superimposed by the seasonal light/temperature pulse (summer/winter regime). Some terrestrial invertebrates show physiological resistance against inundation or drought, phenologies fitting the normal annual rhythm of water level fluctuation (quiescence or diapause of eggs or adult invertebrates), high dispersal ability and migration. However, most species survive simply using a `risk strategy', combining high reproduction rates, dispersal and reimmigration following catastrophic events. 3.,The diversity of species in terrestrial invertebrates is lower in lowland riverine ecosystems of Central Amazonia and Central Europe compared with the respective uplands because of flood stress in these systems. However, floodplains in Central Amazonia possess a greater number of endemic species in comparison with Central European floodplains because of long periods of fairly stable climatic conditions in comparison with large palaeoclimatic changes in Central Europe. [source]

    Population structure in the South American tern Sterna hirundinacea in the South Atlantic: two populations with distinct breeding phenologies

    Patrícia J. Faria
    The South American tern Sterna hirundinacea is a migratory species for which dispersal, site fidelity and migratory routes are largely unknown. Here, we used five microsatellite loci and 799,bp partial mitochondrial DNA sequences (Cytochrome b and ND2) to investigate the genetic structure of South American terns from the South Atlantic Ocean (Brazilian and Patagonian colonies). Brazilian and Patagonian colonies have two distinct breeding phenologies (austral winter and austral summer, respectively) and are under the influence of different oceanographic features (e.g. Brazil and Falklands/Malvinas ocean currents, respectively), that may promote genetic isolation between populations. Results show that the Atlantic populations are not completely panmictic, nevertheless, contrary to our expectations, low levels of genetic structure were detected between Brazilian and Patagonian colonies. Such low differentiation (despite temporal isolation of the colonies) could be explained by demographic history of these populations coupled with ongoing levels of gene flow. Interestingly, estimations of gene flow through Maximum likelihood and Bayesian approaches has indicated asymmetrical long term and contemporary gene flow from Brazilian to Patagonian colonies, approaching a source,sink metapopulation dynamic. Genetic analysis of other South American tern populations (especially those from the Pacific coast and Falklands,Malvinas Islands) and other seabird species showing similar geographical distribution (e.g. royal tern Thalasseus maximus), are fundamental in gaining a better understanding of the main processes involved in the diversification of seabirds in the southern hemisphere. [source]

    Is there limiting similarity in the phenology of fleshy fruits?

    K.C. Burns
    Abstract Question: Is there evidence for limiting similarity in the timing of fruit production by a bird-dispersed plant community? Is the rate of fruit removal in each plant species inversely related to fruit availability in other species? Can simple measurements of fruit phenologies (i.e. temporal changes in fruit availability) obscure important fruit attributes that influence their removal by birds? Location: Vancouver Island, British Columbia, Canada. Methods: Periods of fruit availability were measured in ten woody angiosperm species for two years. In the second year, the fate of individual fruits was quantified to disentangle dates of fruit maturation, removal and mortality from measurements of availability. Results: Null model analyses of fruit availability distributions showed no evidence for limiting similarity. However, fruit removal rates of most plant species were correlated with their relative abundance in the community, indicating fruits were removed more rapidly when other fruits were less abundant. Species with similar periods of fruit availability often had different dates of fruit maturation, rates of fruit removal and fruit persistence times, indicating fruit availability measurements can obscure important bird-fruit interactions. Conclusions: Competition for dispersers appears to occur. However, it has not resulted in limiting similarity in fruit availability distributions. A likely explanation for this discrepancy is that fruit availability distributions often confound several important fruit attributes that can independently influence fruit removal by birds. [source]

    Spatial and temporal variations in the timing of leaf replacement in a Quercus cornelius-mulleri population

    Martin L. Cody
    Nixon & Steele (1981) Abstract. The phenology of spring leaf replacement was studied in a population of 46 evergreen scrub oaks (Quercus cornelius-mulleri) at the edge of the Mojave Desert in each of five years over the period 1990,2001. The oaks occupied a site that spanned rocky slopes to sandy bajadas. The site receives variable annual rainfall (estimated 12-yr average 195 mm; range in study years 67,706 mm). The spatial coordinates of all individuals were recorded, and in April, when leaf replacement was underway, individual replacement phenologies were assessed. Shrub sizes were recorded in three separate years, and in 2001 water potentials were measured. Individuals vary greatly in their timing of leaf replacement within years, and also between years. Many individuals with an early phenology one year are significantly later in the following year, and vice versa. While we detected weak influences on leaf replacement phenology due to shrub size, position within the site, and a genetic component, stronger influences were attributable to the phenology of the shrub in prior years, and to the phenology of neighbours within years. Neighbouring individuals that are close and/or large are significantly disparate in phenology, with one early and the other late. A potential mechanism of local resource depletion associated with costs to an early phenology is discussed. [source]

    Effects of site and fruit size on the composition of avian frugivore assemblages in a fragmented Afrotropical forest

    OIKOS, Issue 2 2002
    M. Githiru
    Factors influencing the interaction between fruiting trees and their frugivorous seed dispersers in fragmented Afrotropical landscapes are poorly known. With the use of Mantel statistics we analysed assemblages of frugivorous birds on 58 individual trees belonging to 11 species growing in seven Kenyan cloud forest fragments. Overall, frugivores showed little specialization on particular trees. Fruit size explained a substantial amount of the variation in frugivore assemblages among different tree species at the same site. In addition, frugivore assemblages on conspecific trees were significantly more similar when the trees occurred at the same site. This location effect was attributable to the different sites and forest fragments (of different sizes and disturbance levels) varying in the densities and composition of their avian frugivores, vegetation composition and tree fruiting phenologies. It was consolidated further by the low mobility of most of these avian frugivores, particularly their reluctance to cross between forest fragments. Habitat disturbance and fragmentation may therefore have affected fruit selection, with implications for both seed dispersal and regeneration. [source]

    Pollinators, flowering phenology and floral longevity in two Mediterranean Aristolochia species, with a review of flower visitor records for the genus

    PLANT BIOLOGY, Issue 1 2009
    R. Berjano
    Abstract The pollination of Aristolochia involves the temporary confinement of visitors inside the flower. A literature review has shown that some species are visited by one or a few dipteran families, while others are visited by a wider variety of dipterans, but only some of these are effective pollinators. We observed flowering phenology and temporal patterns of pollinator attendance in diverse populations of Aristolochia baetica and A. paucinervis, two species that grow in SW Spain, frequently in mixed populations. The two species had overlapping floral phenologies, extended flowering periods and long-lived flowers. A. baetica attracted a higher number of visitors than A. paucinervis. Drosophilids and, to a lesser extent, phorids, were the main pollinators of A. baetica, whereas in A. paucinervis, phorids were the only pollinators. Attendance to A. paucinervis flowers by phorids in mixed populations was markedly lower than in pure populations. This effect was more evident in years with lower pollinator density. Our results suggest that A. baetica and A. paucinervis may compete for pollinators in mixed populations. [source]

    Relations between stomatal closure, leaf turgor and xylem vulnerability in eight tropical dry forest trees

    PLANT CELL & ENVIRONMENT, Issue 3 2003
    ABSTRACT This study examined the linkage between xylem vulnerability, stomatal response to leaf water potential (,L), and loss of leaf turgor in eight species of seasonally dry tropical forest trees. In order to maximize the potential variation in these traits species that exhibit a range of leaf habits and phenologies were selected. It was found that in all species stomatal conductance was responsive to ,L over a narrow range of water potentials, and that ,L inducing 50% stomatal closure was correlated with both the ,L inducing a 20% loss of xylem hydraulic conductivity and leaf water potential at turgor loss in all species. In contrast, there was no correlation between the water potential causing a 50% loss of conductivity in the stem xylem, and the water potential at stomatal closure (,SC) amongst species. It was concluded that although both leaf and xylem characters are correlated with the response of stomata to ,L, there is considerable flexibility in this linkage. The range of responses is discussed in terms of the differing leaf-loss strategies exhibited by these species. [source]

    Spatial and temporal variation in the fruiting phenology of palms in isolated stands

    Abstract Fruiting phenologies of two species of palms, Astrocaryum standleyanum L. H. Bailey and Attalea butyracea (Mutis ex L. f) Wess. Boer, isolated on eight small (1.7,3.7 ha) forested islands in the Panama Canal were studied over a 33-month period. Individual palms were permanently marked with numbered aluminum tags and censused each month for the presence of ripe fruits. The dataset consisted of 1106 monthly observations of palms with ripe fruits among the 634 marked individuals. Mean densities of palms of reproductive size varied widely among islands, ranging from a low of 0.3 ha,1 for A. standleyanum and 3.5 ha,1 for A. butyracea to a high of 44.9 ha,1 for A. standleyanum and 33.7 ha,1 for A. butyracea. Both species showed distinctly seasonal periods of fruiting activity that varied in duration between the two species and among years. The timing of fruiting by A. standleyanum was highly synchronous among islands, whereas inter-island synchrony in A. butyracea was less pronounced. The percentages of marked individuals that fruited varied widely among islands and years. Results indicated that these palms responded to both spatially and temporally variable conditions that promoted fruit production. We suggest that pollinator abundances are a crucial factor affecting reproductive output. Conditions that favor successful reproduction and seed dispersal, such as pollinator activity and the attraction of dispersal agents, may be the ultimate factors that have influenced the reproductive phenologies of these two species of palms. [source]

    Woody Encroachment Removal from Midwestern Oak Savannas Alters Understory Diversity across Space and Time

    Lars A. Brudvig
    Recovering biodiversity is a common goal during restoration; however, for many ecosystems, it is not well understood how restoration influences species diversity across space and time. I examined understory species diversity and composition after woody encroachment removal in a large-scale savanna restoration experiment in central Iowa, United States. Over a 4-year time series, restoration had profound effects across space and time, increasing richness at local and site-level scales. Restoration sites had increased , (within sample) Simpson's diversity and , and , (site level) species richness relative to control sites, although , and , (among sample) Simpson's diversity, , richness, and , species evenness were not affected. Changes in richness were driven by graminoids at the , and , scales and woody species (and some evidence for forbs) at the , scale. Interestingly, indicator species analysis revealed that at least some species from all functional groups were promoted by restoration, although no species were significant indicators of pre-treatment or control sites. Both savanna and nonsavanna species were indicators of restored sites. Restoration promoted exotic species at both scales, although species with spring phenologies were unaffected. Woody encroachment removal may be a means to promote species establishment in savannas; however, in this study, it resulted in establishment and proliferation of native and exotic and savanna and nonsavanna species. Future work might consider reintroduction of key savanna species to supplement those that have established. Work like this demonstrates the utility of restoration experiments for conducting research on large- and multiscale processes, such as species diversity. [source]

    Avian fruit consumption and seed dispersal in a temperate Australian woodland

    AUSTRAL ECOLOGY, Issue 2 2002
    Margaret C. Stanley
    Abstract The effectiveness of avian fruit consumers as seed dispersers of fleshy-fruited plants was studied in a temperate woodland community. As a consequence of the short and overlapping fruiting phenologies of fleshy-fruited plant species in temperate regions of Australia, there are very few avian species that are true specialist frugivores. The relative importance of bird species as fruit consumers was investigated, and how their foraging activities, movements and gut treatment of seeds affected dispersal of viable seeds away from the parent plant was examined. Fruit consumption and consumer seed dispersal capacity were assessed in this study through faecal analyses and by testing the viability of seeds that had passed through the gut of avian consumers. Behavioural observations enabled us to determine the consumption rates of, and quantities of fruit consumed by, various bird species and the amount of time spent feeding. Silvereyes (Zosterops lateralis) were the dominant fruit consumers in the community, although 19 bird species were either observed consuming fruit or provided faecal samples that contained fruit. Silvereyes had a high local abundance at the site and more than 90% of silvereyes'faecal samples contained the seeds of fruiting plants (n = 409). Large numbers of fruit were consumed per visit by silvereyes, particularly for Rhagodia parabolica (fragrant saltbush). Silvereyes consumed an average of four R. parabolica fruit per 5 s and up to a maximum 40 fruit per visit. Viability was high for seeds recovered from silvereyes'faeces (R. parabolica, 94.4% viable; Hymenanthera dentata, 100% viable). However, the number of seeds per faecal sample was high for R. parabolica, which may result in density-dependent seed mortality. Gut passage rate for silvereyes fed R. parabolica fruit in captivity was 31.5 ± 1.9 min. Silvereyes remained at fruiting plants for very short periods (average 50-60 s) and in most cases moved away from the parent plant, primarily toward canopy trees. Given the short visit duration of silvereyes, individuals would have left the parent plant well before seeds passed through the gut. Rhagodia parabolica fruit was consumed by a large number of bird species in the community, including species often thought of as exclusively insectivorous or nectarivorous. These species are likely to disperse viable R. parabolica seeds into microhabitats different from those visited by silvereyes. [source]

    Colonization Strategies of Two Liana Species in a Tropical Dry Forest Canopy

    BIOTROPICA, Issue 3 2007
    Gerardo Avalos
    ABSTRACT Lianas impose intense resource competition for light in the upper forest canopy by displaying dense foliage on top of tree crowns. Using repeated access with a construction crane, we studied the patterns of canopy colonization of the lianas Combretum fruticosum and Bonamia trichantha in a Neotropical dry forest in Panama. Combretum fruticosum flushed leaves just before the rainy season, and its standing leaf area quickly reached a peak in the early rainy season (May,June). In contrast, B. trichantha built up foliage area continuously throughout the rainy season and reached a peak in the late rainy season (November). Both species displayed the majority of leaves in full sun on the canopy surface, but C. fruticosum displayed a greater proportion of leaves (26%) in more shaded microsites than B. trichantha (12%). Self-shading within patches of liana leaves within the uppermost 40,50 cm of the canopy reduced light levels measured with photodiodes placed directly on leaves to 4,9 percent of light levels received by sun leaves. Many leaves of C. fruticosum acclimated to shade within a month following the strongly synchronized leaf flushing and persisted in deep shade. In contrast, B. trichantha produced short-lived leaves opportunistically in the sunniest locations. Species differences in degree of shade acclimation were also evident in terms of structural (leaf mass per area, and leaf toughness) and physiological characters (nitrogen content, leaf life span, and light compensation point). Contrasting leaf phenologies reflect differences in light exploitation and canopy colonization strategies of these two liana species. RESUMEN Las lianas imponen una competencia intensa por la luz en el dosel superior al desplegar un denso follaje encima de las copas de los árboles. Usando acceso repetido al dosel a través de una grúa de construcción, estudiamos los patrones de colonización del dosel de las lianas Combretum fruticosum y Bonamia trichantha en un bosque neotropical seco en Panamá. Combretum fruticosum produjo hojas nuevas justo antes de la estación lluviosa, y su área foliar total alcanzó rápidamente un pico a inicios de la estación lluviosa (mayo-junio). En contraste, B. trichantha construyó su área foliar de forma continua a través de la estación lluviosa alcanzando un pico al final de esta (noviembre). Ambas especies desplegaron la mayoría de sus hojas bajo alta irradiación en la superficie del dosel, aunque C. fruticosum desplegó una mayor proporción de follaje (26%) en micrositios más sombreados que B. trichantha (12%). El auto sombreo dentro de los parches de hojas de lianas dentro de los primeros 40-50 cm del dosel superior redujo el nivel de radiación medido con fotodiodos colocados directamente sobre las hojas a 4-9% de la luz recibida por las hojas de sol. Muchas hojas de C. fruticosum se aclimataron a la sombra luego de un mes después de la producción inicial de hojas altamente sincronizada y persistieron en sombra profunda. En contraste, B. trichantha produjo hojas de corta longevidad de forma oportunística bajo las condiciones de mayor irradiación. Las diferencias entre especies en el grado de aclimatación a la sombra fueron evidentes en términos de caracteres estructurales (masa foliar por unidad de área, y dureza foliar) y fisiológicos (contenido de nitrógeno, longevidad foliar, y punto de compensación lumínica). Estas fenologías foliares tan contrastantes reflejan diferencias en las estrategias de explotación de luz y colonización del dosel por parte de estas dos lianas. [source]