Functional diversity in marine ecosystems
Definition of Functional diversity:
Functional diversity is the variety and distribution of functional traits represented by the organisms in a community.[1]
This is the common definition for Functional diversity, other definitions can be discussed in the article
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Functional diversity can influence ecosystem functioning because organisms with different effect traits contribute differently to processes such as production, filtration, nutrient cycling and sediment mixing. Whether greater functional diversity increases a particular process depends on which traits and processes are considered. Functional diversity often increases the overall productivity of an ecosystem by allowing for an increase in niche occupation - the way a species matches the specific environmental conditions within a habitat in interaction with other species. However, functional diversity has no unique ecological meaning independent of the traits chosen. Diversity of response traits tells us about ecological adaptation strategies and vulnerabilities, while diversity of effect traits tells us more about the contributions to ecosystem functioning.
Functional diversity
Functional diversity describes the variety and distribution of functional traits represented by the organisms in a community. It expresses how different the organisms are in characteristics that influence their ecological responses or their effects on ecosystem processes. Functional diversity adds information that species richness does not provide: species may be numerous but functionally similar, or relatively few but functionally very different. Unlike taxonomic measures based on species identity and abundance, functional diversity focuses on differences among species in their traits.
Functional diversity reflects the biological complexity of an ecosystem[2]. For management, functional diversity can be particularly useful because it focuses on ecological characteristics and processes rather than only on species identity. A complete inventory of marine species is often impractical, whereas changes in important functions or functional groups may be easier to detect and more directly related to ecosystem condition. Protecting key ecological functions can therefore help protect many of the species that contribute to them. However, this approach has limitations because the functional roles of many species are still poorly known.
As explained in the article Functional groups, functional diversity can be represented in a multidimensional functional trait space, in which each axis represents a trait and each species occupies a position according to its trait values. Communities with species spread widely through this space have greater functional trait diversity than communities whose species have very similar traits.
Functional diversity in monitoring data can be analyzed from the functional traits of recorded species, optionally weighted by their abundance or biomass, using several complementary metrics[3] (see Measurements of biodiversity):
- Functional richness – the range of trait values present. A metric for functional richness is the sum of differences among observations in trait space;
- Functional regularity or evenness – how regularly species and their abundances are distributed within the occupied functional trait space. A metric for functional regularity is how regular the differences among observations are;
- Functional divergence – the degree of functional difference among recorded species. A metric for functional divergence is the average difference among observations.
These metrics describe different aspects of functional diversity and should be selected and interpreted according to the ecological question. This scheme is general because it can be applied to abundance, presence/absence or other observational data, and provides a simple and intuitive rationale for grouping functional metrics[4].
Functional groups
Functional groups (FGs) are sets of species that share similar ecological roles within an ecosystem. They are commonly defined as groups of species that have similar effects on ecosystem processes and/or similar responses to environmental conditions[5][6].
Functional redundancy occurs when several species have similar functional traits or perform similar ecological functions. Redundancy can buffer some ecosystem functions against species loss, but high overall species richness does not guarantee that all functions are redundant. Functional redundancy can increase resilience when several species capable of maintaining the same function respond differently to disturbance. In a functionally redundant group, loss of one species may leave the represented ecosystem function largely unchanged because other species have similar traits. However, functions represented by only one or a few species remain vulnerable. High species richness does not guarantee functional security: some ecological functions may depend on only one or a few species, including rare species[7].
Feeding mode and trophic position are examples of functional characteristics that can be used to distinguish ecological roles. Feeding mode examples include (Fig. 1):
- grazer-scrapers feed upon attached algae or biofilms;
- scavengers consume dead organic matter;
- suspension or filter feeders remove particles from the water column;
- deposit feeders pick particles from the sediment surface or subsurface;
- predators consume other living animals;
- parasites obtain resources from living hosts.
Feeding traits often vary with sediment and hydrodynamic conditions. Suspension feeding is favored where currents supply suspended particles, whereas deposit feeding is common where organic matter accumulates in or on the sediment. These relationships are gradual rather than rigid classifications.
Feeding mode is only one functional dimension. Modern trait analyses usually combine it with traits such as body size, mobility, burrowing depth, longevity and sediment-reworking behavior.
Related articles
- Functional groups
- Functional traits
- Biological Trait Analysis
- Measurements of biodiversity
- Marine Biodiversity
- Biodiversity, ecosystem functioning and ecosystem function
References
- ↑ Reiss, J., Bridle, J.R., Montoya, J.M. and Woodward, G. 2009. Emerging horizons in biodiversity and ecosystem functioning research. Trends Ecol. Evol., 24: 505-514
- ↑ Thorne-Miller Boyce (1999) The living ocean: understanding and protecting marine biodiversity. United States of America 213p
- ↑ Villéger, S., Mason, N.W.H. and Mouillot, D. 2008. New multidimensional functional diversity indices. Ecology 89: 2290–2301
- ↑ Mammola, S., Carmona, C.P., Guillerme, T. and Cardoso, P. 2021. Concepts and applications in functional diversity. Functional Ecology 35: 1869–1885
- ↑ Steneck, R.S. 2001. Functional groups. In: Encyclopedia of Biodiversity, Vol. 3 (ed. Levin SA), pp. 121–139. Academic Press, San Diego.
- ↑ Lavorel, S. and Garnier, E. 2002. Predicting changes in community composition and ecosystem functioning from plant traits. Functional Ecology 16: 545–556
- ↑ Mouillot, D., Villéger, S., Parravicini, V., Kulbicki, M., Arias-González, J.E., Bender, M., Chabanet, P., Floeter, S.R., Friedlander, A., Vigliola, L. and Bellwood, D.R. 2014. Functional over-redundancy and high functional vulnerability in global fish faunas on tropical reefs. PNAS 111(38): 13757-13762
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