Functional Equivalence Hypothesis Definition
An example of functional equivalence is shown in plant-pollinator relationships, where a particular plant species may develop a floral morphology that selects pollination by a variety of taxonomically unrelated species to perform the same function (fruit production after pollination). [3] For example, the herbaceous plant Hermathophylla spinosa produces flowers that are shaped in such a way that taxonomically unrelated pollinators behave almost identically during pollination. From the plant`s point of view, each of these pollinators is functionally equivalent and is therefore not exposed to specific selection pressure [3] Variations in the shape and structure of flower and seed morphology can be a source of selection pressure for animal species to develop a variety of morphological traits, but also to give the plant the same function. [4] Kranczioch, C., Mathews, S., Dean, P. J., & Sterr, A. (2009). On the equivalence of executed and imagined movements: evidence of lateralized motor and non-motor potentials. Buzz. Brain Mapp. 30, 3275-3286.
doi: 10.1002/hbm.20748 Lafleur, M. F., Jackson, P. L., Malouin, F., Richards, C. L., Evans, A. C. and Doyon, J. (2002). Motor learning generates parallel dynamic functional changes when executing and presenting sequential foot movements.
Neuroimage 16, 142-157. doi: 10.1006/nimg.2001.1048 In perception, the assumption of functional equivalence is that images that occur without external stimulation of the sensory organs can be considered functioning and functioning as perception. Stippich, C., Ochmann, H., and Sartor, K. (2002). Somatotopic mapping of the primary human sensorimotor cortex during motor imaging and motor execution by functional magnetic resonance imaging. Neurosci. 331, 50–54. doi: 10.1016/s0304-3940(02)00826-1 More recently, biologists have used the idea of functional equivalence, sometimes referred to as functional redundancy, to make predictions about how best to manage ecosystems and their microcosms. It is a common misconception that a high degree of taxonomic diversity within an ecosystem ultimately leads to a healthier, highly functional system. [2] For example, an ecological microcosm of 30 legume species (which add solid nitrogen to the soil) performs only one ecosystem function (nitrogen fixation), although it is taxonomically rich.
On the other hand, an ecosystem with low taxonomic diversity but high functional diversity may be more sustainable. [6] Recent studies have argued that an ecosystem can maintain optimal health by representing each functional group of the ecosystem by many taxonomically unrelated species (functional equivalence). [6] [2] In other words, an ecosystem can potentially achieve its highest level of integrity if it is both functionally and taxonomically rich. Keywords: functional equivalence, inhibition, stop signal task, motor images, ERP, time-frequency EEG analyses Plant-animal interactions related to seed dispersal are another example of functional equivalence. Most plants have been shown to maintain the stability of their evolutionary traits in terms of fruit size and shape for millions of years. [3] However, the animal species that consume and distribute the seeds in the fruit have physically evolved faster than the plants they feed on. In other words, animal species have changed and evolved more than plants have their seed and fruit morphology. The functional equivalence of the animal species that consumes and spreads seeds may explain the ability of these plants to continue to survive without genetic changes in the morphology of their fruits and seeds. [3] As in the Hormathophylla example above, plant species are not subject to the same selection pressure as animals. Many cases of functional equivalence can exist within microbial symbionts and their associated host. Some examples include the wide variety of microbes in the digestive tract of termites and the human gut microbiome.
[5] In these environments, a large number of taxonomically diverse organisms perform the function of digesting food and breaking down cellulose. These microbial organisms most likely evolved under similar conditions but at different times, and it has now been discovered that they interact with each other, giving the same function to their host organism. [5] Porro, C. A., Francescato, M. P., Cettolo, V., Diamond, M. E., Baraldi, P., Zuiani, C., et al. (1996). Activation of the primary motor and sensory cortex during motor performance and motor images: a functional magnetic resonance imaging study. J. Neurosci. 16, 7688-7698.
Huster, R. J., Enriquez-Geppert, S., Lavallee, C. F., Falkenstein, M., and Herrmann, C. S. (2013). Electroencephalography of reaction inhibition tasks: functional networks and cognitive contributions. Int. J. Psychophysiol. 87, 217-233. doi: 10.1016/j.ijpsycho.2012.08.001 Some biologists have questioned the importance of functional equivalence theory.
For example, Loreau points out that in the actual examination of functional equivalence, due to the complexity and oversimplification of the theory itself, it is difficult to draw precise conclusions as to whether the theory is valid or not. For example, many studies that test the effects of species loss and functional redundancy rarely address the uncertainty about whether or not functionality works at the individual or population level, and the possibility of multiple niche dimensions overlapping. [7] In ecology, functional equivalence (or functional redundancy) is the ecological phenomenon whereby several species representing a variety of taxonomic groups can play similar, if not identical, roles in ecosystem functionality (p. e.g. nitrogen fixators, algae scrapers, scavengers). [1] This phenomenon can apply to both plant and animal taxa.