Summary1. Climate change is causing the growing season to expand and many plants are flowering earlier.However we know less about whether other components of reproductive phenology are altered or whether these changes in phenology are adaptive. 2. We evaluated reproductive phenology and fitness components for populations of Campanulastrum americanum sampled across an elevation gradient and reciprocally transplanted into common gardens at high and low elevations. 3. The low-elevation planting site had an expanded growing season that induced the advance of bolting, flowering, average flower date, and time to fruit maturity relative to the high-elevation site for transplants. With the exception of flowering initiation, each successive stage of reproduction was advanced more than the previous one, resulting in a compressed phenology in the warmer environment. 4. In contrast, populations from low elevation had a longer reproductive cycle when grown at both sites, with each phenological component extended relative to populations from high elevation. Fruit production indicated populations were locally adapted to elevation, suggesting these differences in phenology are adaptive. 5. Selection on phenological characters was stronger on transplants in the expanded low-elevation growing season, favouring delayed bolting and advanced flowering. Plastic response to the longer growing season was adaptive for flowering time but maladaptive for bolt initiation. 6. Synthesis. The compressed reproductive phenology favoured in the expanded growing season expected under climate change will largely be achieved with adaptive plasticity of individual phenological traits. Traits under selection in the longer growing season were genetically differentiated between populations that currently differ in growing season length, suggesting evolutionary malleability and likely modification of reproductive phenology in response to climate change.

We selected on divergent photoperiodic response in three separate lines from a natural population of the pitcher-plant mosquito, Wyeomyia smithii. Line crosses reveal that there exists within a population, diverse epistatic variation for a fitness trait that could contribute to adaptive potential following founder events or rapid climate change.

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Definitions 1Phenological event: A precisely defined point in the annual life cycle of a plant or animal, generally marking the start or end point of a phenophase. The occurrence of a phenological event can be pinpointed to a single date and time (in theory, if not in practice). Examples include the opening of the first flower, or the end of leaf fall on a plant. 2Phenophase: An observable stage or phase in the annual life cycle of a plant or animal that can be defined by a start and end point. A phenophase generally has a duration of a few days or weeks. Examples include the period over which newly emerging leaves are visible, or the period over which open flowers are present on a plant. For definitions of specific phenophases, please see the accompanying handout or visitA new approach to generating research-quality phenology data:The USA National Phenology Monitoring System Using the Data for AnalysisData collected by the phenophase status monitoring approach can be valuable for many analyses in its raw state. However, it is also very important to be able to compare this contemporary data with historical phenological event data collected by the traditional approach. The translation of this new data to the traditional format is very straightforward.Many important phenological events can be calculated from the transitions from "No" to "Yes" and "Yes" to "No" in the observation of phenophase status:To make the calculation, the range of dates on which the event could have occurred is determined. Then a midpoint can be calculated and reported as the estimated date of occurrence with an uncertainty of + x number of days:*Note the first instance of budburst and the second instance of flowering have been ignored to simplify this example. The New Approach ("Phenophase Status Monitoring")How to do it: 1. Plan to make regular observations (every 2-3 days is ideal) 2. Record the date every time an observation is made 3. At each observation, record the status of each of several "phenophases" 2 4. Continue making observations throughout the year This approach solves many of the shortcomings of the traditional method:This approach is also well-suited to irregular sampling intervals, one-time observations of a plant, and the observation of animal phenology. 2Calculation of uncertainty in the date a phenophase began or ended can be done with the recording of phenophase "absence" Future EnhancementsThese features greatly enhance the utility of the resulting data for statistical analyses addressing questions such as how phenological events vary in time and space in response to global change. This new approach is an important step forward, and its widespread adoption will increase the scientific value of data collected by citizen scientists and others. The USA-NPN EffortThe USA National Phenology Network has recently initiated a national effort to encourage people at different levels of expertise-from backyard naturalists to professional scientists-to observe phenological events and contribute to a national database that will ...