Positive Interactions and Mutualisms

Ecological investigations of the past several decades have focused on negative interactions (competition and predation) and how they affect population and community structure. Although positive interactions (interactions in which one at least one species benefits and neither is harmed were studied decades ago, there has been limited effort to factor them into our models or thinking about factors impacting populations and communities. My work tries to balance this by using experimental investigations of positive interactions to study the population biology of the participants and the effects of these interactions on communities as a whole.

My recent efforts in this area have been less in the area of empirical investigations and more in the area of conceptual ideas for integrating what we know about mutualism from experimental studies into community ecology more broadly.  This first took the form of integration of facilitation and mutualism in conceptual models of community ecology (Bruno et al. 2003), which I later elaborated on (Stachowicz 2012).  Our empirical studies in this area have focused on interactions among multiple mutualists and between these mutualists and their hosts (Stachowicz and Whitlatch 2005, Bracken, Dorantes-Gonzalez, and Stachowicz 2007). Most host species interact with multiple mutualists at once, many of which co-occur on the same host individual.  This leads to the following question: does having multiple mutualists benefit hosts, or do mutualists interact with one another in antagonistic ways?  Under at least some conditions mutualists are complentary to one another and having multiple mutualist benefits their hosts.  By analogy to the multiple predator effect literature, we have considered the conditions under which mutualists may interact synergistically vs antagonistically (Afkhami, Rudgers and Stachowicz 2014).  Most of these predictions, however, await empirical testing.

Relevant papers

Bruno, J. F., J. J. Stachowicz, and M. D. Bertness. 2003. Inclusion of facilitation into ecological theory. Trends in Ecology & Evolution 18:119-125. [-pdf-]

Afkhami, M.E., J. Rudgers, and J.J. Stachowicz. 2014. Multiple Mutualist Effects: Conflict and synergy in multispecies mutualisms. Ecology 95: 833-84 [-pdf-]

Stachowicz, J.J. 2012. Niche expansion by positive interactions: realizing the fundamentals: a comment on Rodriguez-Cabal et al. Ideas in Ecology and Evolution 5:42-43 [-pdf-]

Bulleri, F, J.F. Bruno, B. Silliman, and J.J. Stachowicz. 2015. Facilitation and the niche: implications for coexistence, range shifts and ecosystem functioning. Functional Ecology, In press

Stachowicz, J. J. 2001. Mutualism, facilitation, and the structure of ecological communities. BioScience 51:235-246. [-pdf-]

Stachowicz, J. J., and R. B. Whitlatch. 2005. Multiple mutualists provide complementary benefits to their seaweed host. Ecology 86:2418-2427. [-pdf-]

Bracken, M. E. S., C. A. Gonzalez-Dorantes, and J. J. Stachowicz. 2007. Whole-community mutualism: Associated invertebrates facilitate a dominant habitat-forming seaweed. Ecology 88:2211-2219. [-pdf-]