Seasonal patterns in species diversity across biomes

Abstract

Citation: Mellard, J. P., P. Audoye, and M. Loreau. 2019. Seasonal patterns in species diversity across biomes. Ecology 100(4):Abstract. A conspicuous season-diversity relationship (SDR) can be seen in seasonal environments, often with a defined peak in active species diversity in the growing season. We ask is this a general pattern and are other patterns possible? In addition, we ask what is the ultimate cause of this pattern and can we understand it using existing ecological theory? To accomplish this task, we assembled a global database on changes in species diversity through time in seasonal environments for different taxa and habitats and also conducted a modeling study in an attempt to replicate observed patterns. Our global database includes terrestrial and aquatic habitats, temperate, tropical, and polar environments, and taxa from disparate groups including vertebrates, insects, and plankton. We constructed nine alternative models that vary in assumptions on type of seasonal forcing, responses to that forcing, species niches, and types of species interactions. We found that most guilds of species exhibit a repeatable SDR across years. For north temperate ecosystems, active species diversity generally peaks mid-year. The peak for a guild is generally more pronounced in terrestrial habitats than aquatic habitats and more pronounced in temperate and polar regions than the tropics. We now have evidence that at least several different habitat and taxa types are likely to have multiple peaks in diversity in a year, for example, guilds of both aquatic microbes and desert vertebrates can show a bimodal or multimodal SDR. We compared all nine candidate models in their ability to explain the patterns and match their assumptions to the data. Some performed considerably better than others in being able to match the different patterns. We conclude that a model that includes both temperature niches and environmental feedbacks is necessary to explain the different SDRs. We use such a model to make predictions about how the SDR could be impacted by climate change. More effort should be put into documenting and understanding baseline seasonal patterns in diversity in order to predict future responses to global change.

Winter in water: differential responses and the maintenance of biodiversity

“…Contemporary theory asserts that temporal niche divergence in fluctuating environments can promote coexistence that would otherwise be impossible in a static environment (Chesson & Huntly ; Adler et al ; Angert et al ; Tredennick et al ). While much of this existing theory has focused on inter‐annual variation, seasonal variation is being increasingly recognised for its role in coexistence (Mathias & Chesson ; Shimadzu et al ; Tonkin et al ; Treddnick et al ; Mellard et al ). For example, competing species inhabiting the same environment and experiencing the same conditions can coexist by diverging in their annual patterns of metabolic activity (Szabo et al ).…”

Species coexistence and temporal environmental fluctuations: a quantitative comparison between stochastic and seasonal variations

“…For example, most systems are affected by both stochastic and periodic variations, although the amplitude of periodic variations (in temperature or precipitation between summer and winter, say) is usually much larger that the year to year stochastic fluctuations. The number of temporal niches under seasonal forcing may be larger than two: phenological differences may allow for a wide variety of temperature niches, as described by Mellard et al [25]. Still, we believe that the results presented in this work provide the essential insights required in assessing the relative importance of these effects and their potential contribution to the richness of life forms in our world.…”

“…Seasonality, and the temporal population variability associated with it, were observed in a wide variety of empirical systems [24][25][26]. Through this paper we provided a survey of its potential role in the maintenance of biodiversity in ecological communities.…”

“…Quantities like yearly precipitation or the mean yearly temperature indeed fluctuate stochastically, but the amplitude of these stochastic variations is usually much smaller than the amplitude of the variations associated with the seasonal cycle during the year. Seasonal effects on demographic rates and on abundance and frequency variations are well-documented, both for populations [25] and for genotypes [26].…”

Winter in water: Differential responses and the maintenance of biodiversity

“…Just as species select for different resources and habitats, and in doing so partition their niche in space, species can also diverge in the timing of their activity, partitioning their niche in time (Chesson 2000). Modern coexistence theory asserts that temporal niche divergence in fluctuating environments can promote coexistence that would otherwise be impossible in a static environment (Adler et al 2006;Angert et al 2009;Chesson & Huntley 1997;Tredennick et al 2017).While much of this existing theory has focused on inter-annual variation, seasonal variation is being increasingly recognized for its role in coexistence (Mathias & Chesson 2013;Mellard et al 2019;Shimadzu et al 2013;Tonkin et al 2017;Treddnick et al 2017). For example, competing species inhabiting the same environment and experiencing the same conditions can coexist by diverging in their annual patterns of metabolic activity (Szabo et al 2016).…”