Ecological niche and facilitation

Background

An ecological niche is the position a species can inhabit in the environment based on biotic and abiotic factors (Peterson 2003). Niche is generally separated into two categories: the “fundamental niche” that restricts a plants distribution through physically limitations such as temperature or precipitation, and the “realized niche” that restricts by biotic restrictions such as competition or consumer pressure (Magnuson et al. 1979; Bruno et al. 2003; Silvertown 2004). Generally the realized niche is viewed as the smaller of the two areas where a plant could inhabit (figure 1), however positive interactions have the capacity to increase the realized niche of plants species (figure 2; Bruno et al. 2003). At the edge of the abiotic range for an annual species, individuals may become associated with shrubs because the favourable microclimate acts as an “island” surrounded by an “ocean” of inhabitability (Walker et al., 2001; Wang et al., 2011). In high stress environments, these positive interactions may be responsible for maintaining the biodiversity in the area by expanding the potential distribution of plant species (McIntire & Fajardo, 2014). Thus, current models predicting plant distributions in arid ecosystems may not be realizing that they have been considering an inflated niche area due to positive interactions. This is concerning because should the positive interactions be removed due to anthropogenic disturbance of shrubs or other processes, areas predicted to have a plant present may not have any present because of a reduced niche size.

barnacles

Figure 1. The spread of Chthamalus when Balanus was removed indicates that competitive exclusion makes the realized niche of Chthamalus much smaller than its fundamental niche (Connell 1961).

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Figure 2. When facilitation is considered, the realized niche (green circle) can be larger than the spatial range predicted by the fundamental niche (dashed line). Incorporating facilitation into the niche concept recognizes processes that can expand the amount of space that meets the requirements of the fundamental niche and can mitigate the effects of niche-shrinking factors (Bruno et al. 2003)

Proposed project

My next project intends to examine the shrub-mediated distribution of annual plants in desert systems. I am hoping to predict the fundamental niche of a plant species based on abiotic factors and examine in what way shrubs extend this to the observed realized niche. Finally, I would like to conduct a manipulation to confirm the capacity of shrubs to extend the distribution of a plant species to an area typically uninhabitable to it.

Niche citations

Bruno, J.  F., Stachowicz, J.  J., & Bertness, M.  D.  (2003).  Inclusion of facilitation into ecological theory. Trends in ecology & evolution, 5347, 1–7.

Connell, J. H. (1961). The influence of interspecific competition and other factors on the distribution of the barnacle Chthamalus stellatus. Ecology, 42(4), 710-723.

Magnuson, J. J., Crowder, L. B., & Medvick, P. A. (1979). Temperature as an ecological resource. American Zoologist, 19(1), 331-343.

McIntire, E. J., & Fajardo, A. (2014) Facilitation as a ubiquitous driver of biodiversity. New Phytologist, 201, 403-416.

Peterson, A. T. (2003). Predicting the geography of species’ invasions via ecological niche modeling. The quarterly review of biology, 78(4), 419-433.

Silvertown, J. (2004). Plant coexistence and the niche. Trends in Ecology & Evolution, 19(11), 605-611.

Wang, Y., Bao, W., & Wu, N. (2011) Shrub island effects on a high-altitude forest cutover in the eastern Tibetan Plateau. Annals of forest science, 68, 1127-1141.