A great new article about facilitation cascades has been published by Christine Angelini and Brian Silliman from the University of Florida. It is such an interesting contribution to our understanding of epiphyte ecology that I'm going to dedicate a few blogs to it. This week: the theory.
A facilitation cascade describes the order of species arrival in a given environment AND the interactions between these species. The example I’ll use does not involve epiphytes but is adapted from one of the original articles on this idea by Andrew Altieri, Brian Silliman, and Mark Bertness (2007).
A facilitation cascade describes the order of species arrival in a given environment AND the interactions between these species. The example I’ll use does not involve epiphytes but is adapted from one of the original articles on this idea by Andrew Altieri, Brian Silliman, and Mark Bertness (2007).
Facilitation cascade. Adapted from Angelini & Silliman (In Press).
Facilitation cascade theory applies when harsh environmental conditions are improved by the arrival of a foundation species. An example is the establishment of seagrass on rocky coastlines which stabilises rocks, softens the impact of breaking waves, and provides shade.
The foundation species provides habitat for a secondary foundation species. Seagrass provides stable substrate for the establishment of mussels that cannot successfully establish on bare rocks.
The combination of foundation and secondary foundation species provides the necessary conditions for many other species to establish and interact. In a coastal system the seagrass and mussels provide substrate and refuge for a diverse and abundant community that includes barnacles, snails and amphipods.
The foundation species provides habitat for a secondary foundation species. Seagrass provides stable substrate for the establishment of mussels that cannot successfully establish on bare rocks.
The combination of foundation and secondary foundation species provides the necessary conditions for many other species to establish and interact. In a coastal system the seagrass and mussels provide substrate and refuge for a diverse and abundant community that includes barnacles, snails and amphipods.
Facilitation cascade examples. Adapted from Altieri et al. (2007).
The key concepts here are that the seagrass does not require the presence of other species to establish but the mussels need the seagrass, and the other species need BOTH the mussels and seagrass.
The positive interactions between these species occur in a hierarchical order and, unlike successional theory, the foundation species is not replaced by subsequent species.
The positive interactions between these species occur in a hierarchical order and, unlike successional theory, the foundation species is not replaced by subsequent species.
A diverse community that has been facilitated by both the seagrass and mussels. Photo: A. Altieri.
The difference in community abudance and diversity with (left side) and without (right side) seagrass & mussels. Photo: Altieri et al. (2007).
Next week: an example of a facilitation cascade in the canopy!
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