Community Phenology

by

David W. Inouye, Amy M. Iler

• LAST REVIEWED: 23 May 2012
• LAST MODIFIED: 23 May 2012
• DOI: 10.1093/obo/9780199830060-0015

Introduction

Phenology is the study of the timing of seasonal events. The Greek root phainomai means to appear, and the most commonly used metric of phenology is timing of first appearance. Humans have been recording phenological events perhaps back to the time of hunter and gatherer societies for the purpose of tracking availability of important resources. For example, the common name of some Amelanchier (Rosaceae) species is shadbush, because their flowering was an indicator of the timing of shad spawning runs in local rivers in eastern North America. Phenology is applied in agriculture; an old farmer’s saying is to plant corn when oak leaves are as large as a squirrel’s ear. Phenology comprises the basic biology of ecological communities, because the timing of life stages of various organisms determines the potential for interspecific interactions and the duration of their overlap within the community. Phenology has garnered increasing attention, because it is one of the best ways to assess the impacts of climate change. This is because environmental cues, such as snowmelt or growing degree days, are commonly used by organisms to time life-history events, such as emergence from hibernation, beginning of the growing season, and flowering or migration dates. In addition, phenological data are typically simple to collect, and citizen scientists are increasingly contributing data via infrastructure established by scientific networks of observers in several countries. Although many studies have focused on individual species, there are significant advantages to adopting a multispecies, or community, perspective. As studies have begun to consider multiple interacting species, it has become clear that a community perspective on phenology is vital to understanding how ecological communities will be impacted by climate change, which can break down the historical synchrony of interacting species. Species with mutualistic relationships, such as pollination, and antagonistic relationships, such as herbivory or predation, have typically coevolved many traits, including phenology. Migratory predators arriving after the period of availability of prey items or herbivores that have lost temporal synchrony with their host plants are unlikely to succeed. Species whose reproductive periods are longer than the availability of any single resource are dependent on the phenology of multiple species for their success—for example, a bumblebee colony that must have access to multiple species of flowers blooming across the growing season. Because of the flourish of publishing activity on phenology and climate change, most late-20th- and early 21st-century phenological research entails a climate change perspective.

General Overviews

The references in this section are overviews and introductions to studies of phenology. It is perhaps unsurprising that some of the earliest studies of community phenology pertain to plant communities and flowering phenology because of the ease of flower identification and study relative to mobile organisms. The early ecological study of phenology was largely descriptive. Carolus Linnaeus proposed in 1751 the idea of a flower clock by planting species that open or close their flowers at particular times of the day. Clarke 1893 was perhaps the first paper devoted to patterns of the timing of flowering in plant communities, proposing a general pattern of seasonal flowering according to evolutionary history: flowering progresses from spring through autumn, beginning with more ancestral taxa and culminating with derived taxa (an outdated hypothesis). Phenological sequences are still generally considered to be repeatable from year to year in temperate habitats (i.e., the seasonal progression from spring to summer to fall communities). Robertson 1895 provides a thorough record of such a repeatable sequence in a plant-pollinator community. Henry David Thoreau’s journals, not published until 1962, represent a thorough record of community phenology (Thoreau 1962). Leopold and Jones 1947 reports one of the first examples of advancing spring events and provides an impressive record of phenology for a multitude of organisms. Jackson 1966 provides an alternative approach to long-term phenological records: measuring variation in local environmental factors and relating this environmental variability to variation in phenology. More recent papers address the question of genetic and environmental influences on phenology, reviewed in Rathcke and Lacey 1985. The timing of species’ phenology within a community seems to be maintained by natural selection and phylogenic constraints, but phenological events are also plastic and can respond quickly to environmental variation. Kochmer and Handel 1986 elaborates on Charles Robertson’s competition hypothesis. Alford 1989 provides a model experimental approach for testing the effects of phenological variation on species interactions within communities, another topic important to community phenology (also see Phenological Mismatches).

• Alford, Rose A. 1989. Variation in predator phenology affects predator performance and prey community composition. Ecology 70:206–219.

  DOI: 10.2307/1938427

  An experimental approach that demonstrates how species interactions are affected by the phenology of at least one of the participants in the interaction. An example of a sound experimental design to test the effects of variation in phenology on the occurrence and outcomes of species interactions that in turn impact the community. Available online for purchase or by subscription.

• Clarke, Henry L. 1893. The philosophy of flower seasons. American Naturalist 27.321: 769–781.

  DOI: 10.1086/275791

  Descriptions of flowering times for plants in the northeastern United States. Peak bloom time of different communities is outlined: early spring in deciduous forests, late spring to early summer in marshes, summer in freshwater plant communities, and midsummer to autumn in meadows. A good read for perspective on the inception of the field, but taxonomic knowledge is necessary to understand detailed descriptions. Available online for purchase or by subscription.

• Jackson, Marion T. 1966. Effects of microclimate on spring flowering phenology. Ecology 47.3: 407–415.

  DOI: 10.2307/1932980

  At the time, a new approach to phenological research: relating local environmental factors to phenology. This paper investigates the relationship among air temperature, north- versus south-facing slopes, and phenology of the wildflower community. Available online for purchase or by subscription.

• Kochmer, John P., and Steven N. Handel. 1986. Constraints and competition in the evolution of flowering phenology. Ecological Monographs 56.4: 303–325.

  DOI: 10.2307/1942549

  The authors discuss potential ways phenological overlap within communities is determined by phylogenetic constraints, life form, and competitive interactions. An elaboration on Charles Robertson’s competition hypothesis (Robertson 1924, cited under Ultimate Causes) in light of more current research.

• Leopold, Aldo, and Sara Elizabeth Jones. 1947. A phenological record for Sauk and Dane Counties, Wisconsin, 1935–1945. Ecological Monographs 17.1: 81–122.

  DOI: 10.2307/1948614

  This provides 328 phenological events presented in twelve tables, organized by month and species. Includes a brief introduction of the history of phenology and discussion of some phenological records from the 1800s. Results are summarized; also includes a discussion of what factors may affect the accuracy of phenological data. Available online for purchase or by subscription.

• Rathcke, Beverly, and Elizabeth P. Lacey. 1985. Phenological patterns of terrestrial plants. Annual Review of Ecology and Systematics 16:179–214.

  DOI: 10.1146/annurev.es.16.110185.001143

  This is a comprehensive review of the literature on plant phenology pertaining to data on seasonal timing of events within years. The framework of the review is evolutionary causes and consequences of the timing of germination, flowering, fruiting, and ecological and evolutionary factors constraining life cycle events. Suitable for undergraduates. Available online for purchase or by subscription.

• Robertson, Charles. 1895. The philosophy of flower seasons and the phaenological relations of the entomophilous flora and the anthophilous insect fauna. American Naturalist 29:97–117.

  DOI: 10.1086/276089

  A comprehensive description of flowering phenophases and pollinating-insect phenophases for a plant-pollinator community in Illinois. Robertson proposed the idea of competition for pollinators determining the bloom time of co-occurring plant taxa, which is now part of current ecological theory. A foundational record of natural history for phenology and pollination biology. Available online for purchase or by subscription.

• Thoreau, Henry David. 1962. The journal of Henry D. Thoreau. Edited by Bradford Torrey and Francis H. Allen. New York: Dover.

  An example of a historical description of community phenology particularly valuable for its outreach potential to nonscientists.