The role of parasites and mutualists in generating and maintaining host species diversity
The Role of Parasites on Species Diversity
Parasites have, for a long time been regarded as pests to the hosts they infect. However, studies have shown that they have positive impacts on generating and maintaining the host species diversity. There are parasites in all ecosystems, which play different roles. For instance, they have the ability to influence the properties and the food web structure. According to Marcogliese and Cone (1997), parasites are part of the food web, and they thus alter the diversity of species, productivity, biochemical cycles, and changes in the topology.
One of the roles of parasites and mutualists is that they affect the dynamics of the food web, and thus the energy flow is also affected. Parasites affect the variation of the host species over time through changing the predation of the host species, their herbivore, and also the competition, which in turn affects the biodiversity of the ecosystem(Forrester et al., 2019). In maintaining hosts species diversity, parasites and mutualists dependence is reliant on the complexity of the ecosystem. Biodiversity refers to the whole variety of all living organisms, which is inclusive of among-systems, among-species, and within-species. The value of biodiversity thus can be translated to the benefits that the world gets form it (Xu et al., 2005).
Parasites will also affect the host species diversity when they are consumed by the hosts. The parasite will thus contribute significantly to the diet of the host. Whether as pry or predators, the parasite plays the role of ensuring that a lot of energy will flow to the [parasites through food webs. For instance, parasites that move from one host to the other through trophic transmission change the behavior of the host, making them at risk of predation. This works to ensure that the parasite moves on to the next host and continue with its cycle(Combes, 2001). For instance, the endoparasite found in amphibians, Ribeiroia ondatrae, makes them have severe deformities of the limbs, thus exposing them to predation by birds who are the next hosts of the parasite.
A parasite can also alter the result of competitive interactions, thus affect the species. For instance, if one species is tolerant of a parasite and another is not, it means that the less tolerant species will be affected by reducing in number. The susceptible specie is thus easy to get extinct due to the biological invasion. This phenomenon leads to a reduction in biodiversity and the diversity of the species. The role of the parasite, in this case, is to maintain host species diversity through control of the host species population. Through parasites, an inferior species can coexist with another dominant species. This means that the parasite plays the role of living in two species hosts, and in so doing, the parasite enables the weak species to live with the dominant species without the weak one dying. The other role of parasites in control of the diversity of the host is through regulating the host population. Since they cause disease, they ensure that the number of host species is controlled but not eliminated. For instance, the parasite found in snails, Schistosomes, does not eliminate the human species, yet it will affect the bodily functions of the human body.
The Impact of Mutualisms on Species Diversity
Mutualism refers to the cooperative interaction between different species. It is important in that it influences global biodiversity. There are many studies that have shown that mutualisms influence the diversity of the host species. Depending on the function that the mutualism plays, the extent to which there are dependence and the species of the mutualism. These aspects affect the diversity of the host through extinction, coexistence in the community, and modulation of speciation.
Mutualisms allow diversity as they allow organisms to have access to crucial functions like nutrition, defense, cleaning, or transport. This means that mutualism is what maintains the diversity of the host species by ensuring that the host species thrive (Boucher et al., 1982). This function is responsible for the evolutionary diversity of the species and also morphological diversity. Mutualisms allow diversification through decreasing the rate of extinction of the species and also through increasing speciation. The effects may occur through a clade, making the diversification of the species to increase in that clade. Another way is through an effect on the dynamics of a mutualistic clade. For instance, the dependence of the interactions can change, or there can be new partners in the mutualism. Partner shifts drive diversity in species, especially when the mutualistic partner is different in functionality. For example, in the case where a bee benefits form the plant by getting nectar while the plant benefits from pollination mutualism. The acquisition of a new partner in pollen transfer like birds or moths will lead to a change in the flower structure. The shift will affect speciation through an interruption in the genes and affect reproductive isolation. The result is that there will be increased speciation, thus diversity.
Through acquiring a new partner through a shift, there will be an increase in the ecological opportunity that impacts on speciation (Losos and Mahler, 2010). The speciation comes about when a species gets access to a previous inaccessible resource, which allows it to have adaptive radiation. For instance, in primates, the evolution of one species led to the diversity of the primates. The increase in ecological opportunity can arise from a shift in a partner, as in the previous example given by a pollinator.
Another example of mutualism is through the symbiosis of insects. For instance, herbivorous insects feeding on plants with symbionts that have pectin degradation is significant as the insects can only access the nutrients through their endosymbionts.
The fourth way there can be diversification through mutualism is through an increase in range sizes, thus a decrease in extinction rates. The size of the range is a valid indicator of extinction. According to Davison (2008), a taxon is deemed extinct if there is no reasonable doubt that the last individual has died. For instance, where a proficient disperser is concerned, the dispersion is over a bigger range geographically, which increases the chances of that taxon increasing and a decrease in the chances that it might go extinct. The other way that extinction risk is reduced is through increasing the survival of the individual species. For this, there are defense mutualisms that protect their partners against mortality through damage or consumption. An example of this is the relationship of the aphid species and the ants. The aphids give honeydew to the ants while the ants take the aphids into their nests at night for protection. They both benefit from the mutualistic relationship. The ants ensure that the aphids do not go extinct out of predation through providing protection (Way, 1963). Sometimes the ants will help the aphids in storing their eggs for winter this mutualistic relationship ensures the survival of both species from extinction.
Conclusion
The prominent roles of mutualists and parasites in host species and, in extension, biodiversity patterns, is a clear indication that they contribute to the shape of the ecological community. There is thus a need to further dissect mutualism and parasitism to understand their nature, besides generating and maintaining host species diversity.
