Habitat cascade explained

A habitat cascade is a common type of a facilitation cascade.^[1] where “indirect positive effects on focal organisms are mediated by successive formation or modification of biogenic habitat”.^[2]

A habitat cascade is composed of at least three organisms: a primary habitat former or modifier; a secondary habitat former or modifier; and a focal organism that utilizes the secondary habitat former or modifier. For example, primary habitat forming trees can provide habitat for secondary habitat forming epiphytes, lianas, or vines that again can provide habitat to focal organisms like insects and birds.^{[3] [4]}

The primary vs. secondary habitat formers are sometimes referred to as ultimate vs. proximate habitat formers,^[5] basal vs. intermediate habitat formers,^[2] primary vs. secondary ecosystem engineers,^[6] primary vs. secondary foundation species,^[7] basibionts vs. epibionts,^[8] basizoids (if animal) or basiphytes (if plant) vs. epizooids (if animal) or epiphytes (if plant),^[8] or hosts vs. structural parasites.^[9] Focal organisms have been referred to as clients, end-users, habitat-users, inhabitants or hyperepibionts^{[2] [10] [11]}

Secondary habitat formers are typically attached to,^{[3] [12] [13] [14]} entangled around,^{[15] [16]} or embedded within^{[17] [18]} the primary habitat former. Habitat cascades are strongest when the secondary habitat former is more effective than the primary habitat former at allowing focal organisms to avoid stress and enemies, and find resources and other facilitators.^[11]

Habitat cascades promote increased biodiversity in ecosystems dominated by large and long-lived sessile or slow-moving structural organisms.^{[2] [11]} For example, habitat cascades have been documented in tropical forests,^{[4] [14] [15] [19] [20]} temperate forests,^{[3] [13] [21] [22]} salt marshes,^{[1] [23]} coral reefs,^{[24] [25]} seagrass beds,^{[26] [27] [28] [29]} mangrove stands,^{[15] [30]} polychaete gardens,^[2] seaweed covered rocky coasts^[12] and mollusc reefs^[31]

Notes and References

1. Altieri, A.H., B. Silliman, and M.D. Bertness, Hierarchical organization via a facilitation cascade in intertidal cordgrass bed communities. The American Naturalist, 2007. 169: p. 195-206.
2. Thomsen, M.S., et al., Habitat cascades: The conceptual context and global relevance of facilitation cascades via habitat formation and modification. Integrative and Comparative Biology, 2010. 50(2): p. 158-175.
3. Angelini, C. and B.R. Silliman, Secondary foundation species as drivers of trophic and functional diversity: evidence from a tree-epiphyte system. Ecology, 2014. 95(1): p. 185-196.
4. Cruz-Angon, A. and R. Greenberg, Are epiphytes important for birds in coffee plantations? An experimental assessment. Journal of Applied Ecology, 2005. 42: p. 150-159.
5. Thomsen, M.S. and K. McGlathery, Facilitation of macroalgae by the sedimentary tube forming polychaete Diopatra cuprea. Estuarine, Coastal and Shelf Science, 2005. 62: p. 63-73.
6. Gribben, P.E., et al., Behavioural interactions between ecosystem engineers control community species richness. Ecology Letters, 2009. 12: p. 1127-1136.
7. Angelini, C., et al., Interactions among foundation species and their consequences for community organization, biodiversity, and conservation. BioScience, 2011. 61: p. 782-789.
8. Wahl, M., Epibiosis Ecology, Effects and Defences Ecological Studies, Marine Hard Bottom Communities, Part 1, 2009. 206: p. 61-72.
9. Stevens, G.C., Lianas as structural parasites: the Bursera simaruba example. Ecology, 1987: p. 77-81.
10. Fernandez-Leborans, G., et al., Epibiosis and hyperepibiosis on Pagurus bernhardus (Crustacea: Decapoda) from the west Coast of Scotland. Journal of the Marine Biological Association of the United Kingdom, 2013. 93(5): p. 1351-1362.
11. Thomsen, M.S. and T. Wernberg, On the generality of cascading habitat-formation. Proceedings of the Royal Society B: Biological Sciences, 2014. 281(1777):20131994.
12. Thomsen, M.S., et al., A host-specific habitat former controls biodiversity across ecological transitions in a rocky intertidal facilitation cascade. Marine and Freshwater Research, 2016. 67: p. 144-152.
13. Watson, D.M. and M. Herring, Mistletoe as a keystone resource: an experimental test. Proceedings of the Royal Society B: Biological Science, 2012. 279(1743):p.3853-3860.
14. Yanoviak, S.P., et al., Effects of an epiphytic orchid on arboreal ant community structure in Panama. Biotropica, 2011. 43(6): p. 731-737.
15. Bishop, M.J., et al., Density-dependent facilitation cascades determine epifaunal community structure in temperate Australian mangroves. Ecology, 2012. 93(6): p. 1388-1401.
16. Thomsen, M.S., Experimental evidence for positive effects of invasive seaweed on native invertebrates via habitat-formation in a seagrass bed. Aquatic Invasions, 2010. 5(4): p. 341-346.
17. Altieri, A., et al., Facilitation cascade explains positive relationship between native biodiversity and invasion success. Ecology, 2010. 91: p. 1269–1275.
18. Angelini, C., et al., Foundation species’ overlap enhances biodiversity and multifunctionality from the patch to landscape scale in southeastern US salt marshes. Proceedings of the Royal Society B: Biological Sciences, 2015. 282(1811).
19. Cruz-Angon, A., M.L. Baena, and R. Greenberg, The contribution of epiphytes to the abundance and species richness of canopy insects in a Mexican coffee plantation. Journal of Tropical Ecology, 2009. 45: p. 453–463.
20. Stuntz, S., et al., Do non-myrmocophilic epiphytes influence community structure of arboreal ants? Basic and Applied Ecology, 2003. 4(4): p. 363-373.
21. Díaz, I., et al., A field experiment links forest structure and biodiversity: epiphytes enhance canopy invertebrates in Chilean forests. Ecosphere, 2012. 3(1): p. 3:art5.
22. Watson, D.M., Effects of mistletoe on diversity: a case-study from southern New South Wales. Emu, 2002. 102(3): p. 275-281.
23. Dijkstra, J.A., J. Boudreau, and M. Dionne, Species‐specific mediation of temperature and community interactions by multiple foundation species. Oikos, 2012. 121(5): p. 646-654.
24. Bergsma, G.S., Coral mutualists enhance fish abundance and diversity through a morphology-mediated facilitation cascade. Marine Ecology Progress Series, 2012. 451: p. 151-161.
25. Bergsma, G.S., Mutualists alter coral susceptibility and response to biotic disturbance through cascading trait-mediated indirect interactions. Coral Reefs, 2012.
26. Edgar, G.J. and A.I. Robertson, The influence of seagrass structure on the distribution and abundance of mobile epifauna: pattern and processes in a Western Australian Amphibolis bed. Journal of Experimental Marine Biology and Ecology, 1992. 160: p. 13-31.
27. Hall, M. and S. Bell, Response of small motile epifauna to complexity of epiphytic algae on seagrass blades. Journal of Marine Research, 1988. 46: p. 613-630.
28. Thomsen, M.S., et al., Harmful algae are not harmful to everyone. Harmful Algae, 2012. 16(0): p. 74-80.
29. Thomsen, M.S., Experimental evidence for positive effects of invasive seaweed on native invertebrates via habitat-formation in a seagrass bed. Aquatic Invasions, 2010. 5: p. 341–346.
30. Bishop, M.J., J. Fraser, and P.E. Gribben, Morphological traits and density of foundation species modulate a facilitation cascade in Australian mangroves. Ecology, 2013. 94: p. 1927–1936.
31. Thomsen, M.S., et al., Effects of the invasive macroalgae Gracilaria vermiculophylla on two co-occurring foundation species and associated invertebrates. Aquatic Invasions, 2013. 8: p. 133-145.