The Functional Role of Biodiversity

Biodiversity is broadly defined as the “degree of variation of life.” Biodiversity arguably adds great intrinsic value to our planet, but biodiversity is also important because it’s indicative of ecosystem health, function, and service. For example, high levels of biodiversity can point to a resilience from disturbance, presence of complex wildlife habitat, and effective air and water purification. Tilman (2014) summarized 100 biological studies and found that biodiversity was positively correlated with productivity, indicating a strong relationship between biota and ecosystem processes. Because of the strong connection between wildlife and our environment and natural resources, changes in biodiversity frequently lead to shifts in ecosystem processes and services that we all rely on. Focus on biodiversity therefore is vital for promoting a healthy human population and world.

Biodiversity is most commonly measured and discussed using taxonomic diversity (e.g., species identity), however, there are several other ways biodiversity can be assessed. One such axis is functional diversity. A variety of functional categorizations have been used such as behavioral habits (e.g., activity mode; Merritt, 2008), morphological features (e.g., body size; Hein, Hou & Gillooly, 2012), habitat occupation (e.g., littoral zone), life history traits (e.g., reproduction events per year; Olden, Poff & Bestgen, 2006), and feeding groups (EPA, 2014). Overall, this trait-based research focus came about as ecologists realized that not all species affect ecosystem processes equally or in the same manner; therefore, attention to what species do ecologically, instead of simply what species are taxonomically, has become a key component of biodiversity studies.

Such functional assessments can capture features of the biotic assemblage that would not be acknowledged with only taxonomic evaluations (Giller et al., 2004; Setala, 2002). Functional diversity has offered various benefits for researching specific aspects of community investigation, including assemblage structure and composition, chemical breakdown and accumulation, and non-native invasion. For example, assessing functional diversity of fishes according to their feeding groups (e.g., piscivore, insectivore, parasite, etc. [EPA, 2014]), such as shown in Figure 1 can indicate level of competition, resource availability, niche availability, and habitat characteristics. When assessing the degree of variation of life, unique axes of assessing organisms and plants, such as functional diversity, can give unique and informative insights of the community which lead to effective investigations of biotic communities.

Figure 1. Examples of Lake Erie fish species categorized according to their functional feeding groups: Bowfin (Amia calva) Piscivore; Pumpkinseed Sunfish (Lepomis gibbosus) Insectivore; American Brook Lamprey (Lampetra appendix) Parasite; White Sucker (Catostomus commersonii) Omnivore.

References:

EPA. 2014. 2014 Updates to Biological Criteria for the Protection of Aquatic Life. In: Users Manual for Biological Field Assessment of Ohio Surface Waters. Ohio Environment Protection Agency: Division of Surface Water.

Giller P.S., Hillebrand H., Berninger U.G., Gessner M.O., Hawkins S., Inchausti P., Inglis C., Leslie H., Malmqvist B., Monaghan M.T., Morin P.J. & O'mullan G. 2004. Biodiversity effects on ecosystem functioning: emerging issues and their experimental test in aquatic environments. Oikos, 104, 423-436.

Hein A.M., Hou C. & Gillooly J.F. 2012. Energetic and biomechanical constraints on animal migration distance. Ecology Letters, 15, 104-110.

Merritt R.W., K. W. Cummins, and M. B. Berg (Editors). 2008. An introduction to the aquatic insects of North America, Kendall/Hunt Publishing Company, Dubuque, Iowa

Olden J.D., Poff N.L. & Bestgen K.R. 2006. Life-history strategies predict fish invasions and extirpations in the Colorado River Basin. Ecological Monographs, 76, 25-40.

Setala H. 2002. Sensitivity of ecosystem functioning to changes in trophic structure, functional group composition and species diversity in belowground food webs. Ecological Research, 17, 207-215.

Tilman D. 2014. Biodiversity and Ecosystem Functioning: Annual Review of Ecology Evolution and Systematics. (Ed I. Forest), pp. 471-493. Annual Review of Ecology, Evolution, and Systematics.

-- Jenna Odegard, Wildlife Specialist