Time after time: flowering phenology and biotic interactions.
ABSTRACT The role of biotic interactions in shaping plant flowering phenology has long been controversial; plastic responses to the abiotic environment, limited precision of biological clocks and inconsistency of selection pressures have generally been emphasized to explain phenological variation. However, part of this variation is heritable and selection analyses show that biotic interactions can modulate selection on flowering phenology. Our review of the literature indicates that pollinators tend to favour peak or earlier flowering, whereas pre-dispersal seed predators tend to favour off-peak or later flowering. However, effects strongly vary among study systems. To understand such variation, future studies should address the impact of mutualist and antagonist dispersal ability, ecological specialization, and habitat and plant population characteristics. Here, we outline future directions to study how such interactions shape flowering phenology.
SourceAvailable from: Richard J. Smithers[Show abstract] [Hide abstract]
ABSTRACT: 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. © 2015 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.Global Change Biology 03/2015; DOI:10.1111/gcb.12896 · 8.22 Impact Factor
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ABSTRACT: Organisms develop through multiple life stages that differ in environmental tolerances. The seasonal timing, or phenology, of life-stage transitions determines the environmental conditions to which each life stage is exposed and the length of time required to complete a generation. Both environmental and genetic factors con-tribute to phenological variation, yet predicting their combined effect on life cycles across a geographic range remains a challenge. We linked submodels of the plasticity of individual life stages to create an in-tegrated model that predicts life-cycle phenology in complex envi-ronments. We parameterized the model for Arabidopsis thaliana and simulated life cycles in four locations. We compared multiple "ge-notypes" by varying two parameters associated with natural genetic variation in phenology: seed dormancy and floral repression. The model predicted variation in life cycles across locations that quali-tatively matches observed natural phenology. Seed dormancy had larger effects on life-cycle length than floral repression, and results suggest that a genetic cline in dormancy maintains a life-cycle length of 1 year across the geographic range of this species. By integrating across life stages, this approach demonstrates how genetic variation in one transition can influence subsequent transitions and the geo-graphic distribution of life cycles more generally. Plant life cycles are composed of multiple life stages (e.g., seed, vegetative, reproductive) that differ in environmental sensitivities and tolerances. In seasonal environments, the timing, or phenology, of life-stage transitions (e.g., germi-nation, flowering, seed dispersal) may have importantThe American Naturalist 02/2015; 93513(4). DOI:10.1086/679439 · 4.45 Impact Factor
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ABSTRACT: Plant-pollinator interactions have traditionally been a hot topic in ecology and evolutionary biology due to both the ecological services it offers and its complexity as a system. Plants generally show a high diversity of floral visitors, making generalism a more common condition than expected. Fur- thermore floral visitor community seems to have spatio-temporal fluctuations in diversity and composition. Those variations respond to plant intrinsic and extrinsic factors and can affect to evolutionary and ecological aspects of plant populations. Here we assess the temporal variation in the floral visitor assemblage of the generalist plant Erysimum mediohispanicum Polatschek (Brassicaceae). We set up two experimental plots homogenizing for spatial and microenvironmental conditions to ascertain only the temporal variations in the floral visitors assemblage. During the flowering season we did daily censuses of the floral visitors, determining them to morpho-species level and clumped them in 16 functional groups based on morpho- logical and behavioral characteristics. We found a high diversity for the whole assemblage in both experimental plots with high temporal fluctuations during the flowering season. Our results suggest an important species turnover with high fluctuations in relative abundance for some functional groups, which may turn into important ecological and evolutionary consequences.