Home > Environmental studies essays > Stability of obligate-facultative mutualisms (coral)

Essay: Stability of obligate-facultative mutualisms (coral)

Essay details and download:

  • Subject area(s): Environmental studies essays
  • Reading time: 17 minutes
  • Price: Free download
  • Published: 27 March 2022*
  • File format: Text
  • Words: 5,067 (approx)
  • Number of pages: 21 (approx)

Text preview of this essay:

This page of the essay has 5,067 words. Download the full version above.

Introduction

Mutualisms are defined as the interaction between at least two species where all participating species benefit from the interaction. These interactions hold ecological, conservational, and economical importance. Mutualisms can function as keystone species1, and some provide ecosystem services, such as the insect pollination, which is not only ecologically but also economically important. 2, 3. As for conservation, there is growing evidence that mutualisms are essential for the support of most of the biodiversity on Earth.4, 5 Given their importance and prevalence, it is perhaps surprising that mutualisms in of themselves are inherently unstable. This is because it is preferable for mutualists to minimize the cost related in providing benefits while maximizing the benefits they obtain from their partner. That is, being a parasite is preferable to a mutualist.6 The maintenance of stable mutualism is thus a constant struggle, and failure to do so, for whatever reason, results in mutualism breakdown.

In an evolutionary context, mutualism breakdown is the loss of a mutualist relationship between two former partner lineages. Three mechanisms for mutualism breakdown have been identified: extinction of one or more partners, shift to parasitism, and reversion to autonomy.7 The tendency for a mutualism to breakdown is related to many factors, which also affect the path of breakdown, should it occur. A good example of this is different levels of dependence on the mutualism.

Obligate mutualists, which cannot survive without their partner, are usually treated as similar to facultative mutualists in terms of processes that explain mutualism breakdown, expect they are unable to revert to autonomy. However, there is a difference in the freedom that obligate and facultative mutualists enjoy. Specifically, since their survival depends on the normal functioning of the mutualism, obligate mutualists are under more evolutionary pressure to maintain the established mutualistic relationship. This could have a positive or negative impact on the stability of the mutualism: Obligate mutualists are under pressure to regulate the mutualism more rigorously so that it remains functional. However, they are also more defenseless against partner parasitism or autonomy, should it arise and persist. In these scenarios, the obligate mutualist has neither the ability to leave the symbiosis nor to survive with a now parasitic or autonomous former partner.

Mutualisms that involve both obligate and facultative partners are particularly interesting in this regard, since partners are experience unequal pressure to maintain and thus regulate the mutualist relationship. Maintenance of the mutualism thus depends on the delicate balance of differing pressures to maintain the mutualism, which involves intricate mechanisms for partner control. A well-known example of this is reef-building corals.

Scleractinian corals construct and provide a habitat for a wide variety of marine species via their reef-building ability, and are also important for fishing and tourism industries.8 Scleractinians form symbiosis with a wide variety of organisms, but most intensely studied is the mutualism with a variety of species of zooxanthellae from the family Symbiodiniaceae, where the coral is an obligate mutualist and the symbionts are facultative mutualists.9 The level of cooperativeness and dependence on the mutualist partner varies among both hosts and symbionts,10, 11 but all Scleractinian-Symbiodiniacean mutualisms have a similar basic set-up. The dinoflagellate symbiont provides the host with photosynthetic products, while the host provides symbionts with protection from predators and substrates for photosynthesis, most importantly ammonium.12 This increases the fitness of both mutualists in nutrient-poor environments. The host is more involved in the set-up and maintenance of the symbiosis, being in control of symbiont infection, nutrient transfer, and symbiont selection.12 Exact mechanisms vary among host species, but can involve recognition and active recruitment of symbionts, degradation of unsuitable symbionts, sequestering of nutrients from symbionts, control of symbiont growth rate, and expulsion of symbionts.13

Anthropogenic changes to the environment such as increasing seawater temperatures and eutrophication are causing what is likely the start of a breakdown of this mutualism.12 This occurs through several processes, the most well-known of which is coral bleaching, where the coral host expels its dinoflagellate symbionts. The host is unable to be re-infected until conditions become more desirable, and dies if it fails to regain symbionts for an extended period of time.14 Apart from this, symbionts become more parasitic,15 and hosts are more susceptible to infection by parasitic strains of symbionts under high temperatures.11

Using corals as an example, this paper discusses the stability of obligate-facultative mutualisms in reference to the resistance to set-up of the mutualism provides, both in an evolutionary context and in the rapidly changing environment that characterizes the Anthropocene. Considering the inherent stability of the mutualism under these two conditions, this paper then seeks to predict the outcome of the Scleractinian-Symbiodiniacean mutualism, and assess the effectiveness of proposed conservation measures.

Factors affecting mutualism breakdown

Based on results from both theoretical and empirical studies, several factors have been found to affect susceptibility of mutualism breakdown. The following section will discuss how, if any, these affect the resistance of the mutualism of corals, in general as well as specifically under the rapid global change that corals, like all other organisms, currently face.

Inherent to set up of symbiosis

Not all mutualisms are created equal, inherent in the set-up of mutualisms, there are four factors identified by Sachs et al that could affect susceptibility of mutualism breakdown. These factors stabilize the mutualism by counteracting the incentive of mutualist partners to parasitize each other, and have the most influence when the environment is not significantly affecting the mutualism. To this end, each of these provide incentive for partners to continue providing benefits to each other, or allow for the discouragement of cheating by partners.

The first is by-product mutualism, which is where providing benefits to partner is not costly for a mutualist. Thus, there would be little pressure for parasitism to evolve since there is not much to gain, and potentially more to lose should the mutualism terminate. The coral symbiosis, however, is not one that involves low cost. Under the normal set-up of the symbiosis, 95% of all photosynthetic products produced by symbionts are transported to the host, which of course comes at an enormous energy cost to symbionts.16 For the host, the cost is less significant since the photosynthetic substrates it provides its partners, CO2 and ammonium, are waste products.17 Thus, unlike with by-product mutualism, in corals there is something to be gained in conversion to parasitism by the symbiont: a significant cost is removed while the benefits could be reaped still. The host in contrast is more stabilized in the relationship by this factor.

The second is reciprocity – having more to gain from benefiting the partner, than from not doing so. In corals, the host has control over symbiont fitness, allowing for the selection of cooperative symbionts which translates into reciprocity for symbionts. This is done by multiple mechanisms at different stages of establishment of the symbiosis. At the infection stage, some coral hosts recognize specific symbiont species.13 Even if infection is undiscriminating, hosts digest undesirable symbionts before stable symbiosis is established.12, 13 Under the normal operation of the mutualism, the host controls symbiont access to nutrients and continuously expels symbionts selectively, which could allow for the favoring of more cooperative symbionts.13 Reciprocity for the host arises from its status as an obligate mutualist. The host depends on the symbiont to fulfill most, if not all, of its energy requirements.13 Since the host receives the vast majority of photosynthetic products,16 it must provide the symbiont with the sufficient substrates for efficient photosynthesis. It is worth noting that there is no mutually specific pair of host-symbiont association in corals, but locally corals generally associate with one type of symbiont,13 so the linkage of host and symbiont fitness is likely significant,6 meaning reciprocity stabilizes this mutualism.

The third is the cost-benefit ratio. For there to be pressure against mutualism breakdown, the benefits of engaging in mutualism must outweigh the costs, while mutualism breakdown must confer more costs than benefits.6 As discussed above, the benefit the host provides the symbiont does not involve a great cost. However, the host incurs additional costs involved in the maintenance of the mutualism – control of the symbiont via recruitment, selection, husbandry, and expulsion all involve energy-demanding active processes. However, as an obligate mutualist, mutualism breakdown is clearly disastrous, so benefit of the mutualism outweighs costs. This may not be the case for the facultative symbiont. Symbionts mainly gain access to nutrients in the host, as well as some protection, but at the cost of the energy from the vast majority of the useful products formed through photosynthesis.12, 13 If nutrients become readily available in the environment, the cost-benefit ratio for symbionts may be unfavorable for the continuation of mutualism, consistent with symbiont overgrowth in corals in polluted waters.18 The host controls access of some but not all forms of nutrients from the symbiont,19 thus under eutrophic conditions the cost-benefit ratio may be too large for the symbiont for mutualism to be “worth it”. Regardless, under normal conditions the cost-benefit ratio is favorable for the mutualism.

The fourth and last factor is partner-switching ability.6 As we will later discuss, this is also important for adapting to changing abiotic and biotic environments in the Anthropocene. The ability to switch partners allows for the formation of mutualism with more cooperative partners, under two conditions: the availability of more a cooperative partner and the ability of the host to select for them. Partner switching ability is only possessed by the host, since the symbiont is incorporated into host cells and cannot leave the host unless expelled.12 While it was previously thought that corals were specific in their association, with differences in symbiont composition arising from regional availability and/or adaptation to local environment, recent studies show that most corals are in fact able to associate with more than one species of symbiont, and that mixed infections were more common than previously believed, albeit at very skewed ratios.13 This opens the possibility of partner switching. Under the adaptive bleaching hypothesis, bleaching is a process through which the host can replace symbionts, potentially gaining better symbionts for adaptation to the environment.20 Symbiont shuffling, where the coral is not bleached but the relative abundance of symbionts already present inside the coral changes, has also been implicated in partner switching.13 However, coral bleaching, even under this hypothesis, is essentially a gamble. There is no guarantee that a better community of symbionts will re-infect the coral host, and there are studies that suggest that the weakened bleached state of the host allows for the infection of parasitic symbionts from genus Symbiodinium (formerly Clade A).21 Regardless, this risk is inherent in all partner switching, and since partner switching is possible in corals, it at least theoretically increases resilience of the coral mutualism.

Considering the above four factors, we see that the inherent set-up of coral symbiosis is relatively stable, with by-product mutualism, reciprocity, a favorable cost-benefit ratio, and partner-switching all working in part to maintain the mutualism. It comes as no surprise, then, that despite the existence of corals since the Paleocene and the incredible divergence since,22 the Scleractinian-Symbiodinian mutualism is maintained across most, if not all, Scleractinian species. However, the not insignificant cost of mutualism coupled with a possibility of change in cost-benefit ratio of symbionts and the inherent risk of partner switching puts pressure on the maintenance of the mutualistic relationship.

Factors in changing environment

A stable mutualism over evolutionary time is not necessarily one that is stable in the face of environmental change. Although there are of course environmental changes throughout the eons, the main destabilizing factor is that of evolutionary pressure on mutualists since most changes were gradual in nature. In contrast, the rapid human-induced changes that mark the current epoch places a different stress on the mutualism. Some possible mechanisms identified include the appearance of parasitic niches, new found availability of nutrients provided previous by the host, etc.7 In a sense, the essence of the stressors themselves are largely similar – they all contribute to the continual struggle between the maintenance of the mutualism and the evolutionary pressure to take advantage of partner(s). The critical difference here is time – unlike evolution or gradual climate changes, which happens over generations, stressors now operate on a greatly shortened time scale and the induced shift in the balance in the mutualism is sudden. Against these sudden challenges, a different cast of resistance factors must be invoked.

The first of these is a strict control of partner. The ability to control one’s partner allows for the mutualist to associate with beneficial partners, maintaining a functional mutualism with pre-existing partners that confer better fitness under the new or changing environment.7 This is essentially an extension of reciprocity and partner-switching criteria above. It is unsurprising that the ability to identify and selectively associate with more cooperative partners functions under rapid environmental changes as well. However, as discussed earlier, partner switching involves inherent risk of infection by parasitic varieties of symbionts or the lack of superior symbionts in the environment. In addition, the process of partner switching in corals comes at a great cost to the host. Coral bleaching is not only energy intensive, it can also involve the death of host cells and the loss of a vast energy source in the form of symbiont-produced substances. In addition to this, corals have been found to be unable to become re-infected under bleaching conditions,14 so successful partner switching requires relaxation of environmental stress. The relief of this stress may eventually be impossible, particularly considering that global carbon emissions show no signs of deceleration, let alone decline.23 Modeling studies also suggest that while coral association with different symbionts allows the host to acclimate to environmental changes, it does not necessary lead to the adaptation to said changes.24

The second is the lack of strict dependence. Dependence on mutualist partner for survival, which is absolute for obligate mutualists such as the Scleractinian host, is destabilizing in the face of rapid change.7 Obligate mutualists require the benefits extended by their mutualist partner for their continued survival, so even short-term reductions of benefits extended may prove to be intolerable. On the other hand, while facultative mutualists may suffer a reduction in fitness, their ability to survive in a less productive or unproductive mutualism essentially buys time for the mutualism to adapt to changes in the environment. In the case of corals, under unfavorable conditions bleaching occurs on the scale of days or weeks, which indicates the intolerance of the host toward unproductive symbionts.

The third is rapid evolution. When one of the partners evolves quickly, it may be able to adapt to the changing environment, and this rapid adaptation could confer benefits to slower mutating partners.7 In the case of corals, symbionts evolve much more rapidly than hosts. However, symbionts are not obliged to evolve in a way that benefits the host, and it is also possible for the rapid evolving mutualist to take advantage of a weakened host or novel niches in the changing environment to parasitize its partner. Indeed this appears to be the case. Under heat stress, symbionts become more parasitic and provide their hosts with less nutrients, instead diverting the extra energy to reproduction.13

The fourth is the ability to take advantage of novel niches. Environmental changes can create novel niches as well as modify existing ones. While the niche of the mutualism may also be modified unfavorably, if novel niches can be taken advantage of, mutualisms may be able to shift from their now unfavorable niche and maintain the mutualism in a new niche.7 The coral-symbiont mutualism evolved to take advantage of a very specific environment, one with scarce dissolved nutrients, in a specific temperature range, specific turbidity, etc. The shift to a niche with completely novel abiotic parameters is unlikely since the mutualism evolved to be competitive under specific abiotic conditions.25 However, following a trend that is seen among a wide variety of species, there is evidence that suggests the range of corals are shifting towards higher altitudes, where temperatures are more favorable.26 However, this shift also involves change in other important abiotic factors such as the availability of light and nutrients, as well as suitable substrate, etc.24 Furthermore, under continuously increasing global temperatures this shift is unsustainable.

The fifth is resistance to changes in environmental conditions. If a mutualist can buffer itself against environmental changes, it would be able to buy time for the mutualism as a whole to adapt to changing environments, or maintain optimal conditions for mutualism maintenance.7 While corals are generally seen as sensitive to environmental changes, there are actually several mechanisms in both the host and the symbiont that could contribute to resistance towards environmental stressors. One such example is the production of DMSP by both host and symbionts when under heat stress, which has been speculated to in part be related to cloud seeding, allowing for the temporary lowering of temperatures.27 Hosts also produce pigments that absorb excess radiation, protecting against UV damage.12 Another is the control of symbiont access of nutrients by the host, which allows the maintenance of mutualism in spite of readily available nutrients from eutrophication.19 This explains the ability of the coral symbiosis to survive through the eons despite being seen as sensitive to environmental changes. However, in face of the many rapid environmental changes that define the Anthropocene, the prevalence of coral bleaching suggests that these mechanisms are unlikely sufficient to resist rapid environmental changes in the Anthropocene.

The sixth is tolerance to short term costs. This is extended from a lack of strict dependence. In the same that that toleration towards decreased benefits allows the mutualism more time to adapt and evolve, the tolerance for increased costs also buys time for adaptation of the mutualism to rapid changes. Over evolutionary time tolerance to short term costs is not desirable, since it contradicts strict control of partner. Thus as mentioned earlier, corals bleach rapidly in the face of temperature changes. Since the host requires symbionts for survival, this is particularly problematic, indicating that there is little tolerance to any increase in short term cost or decrease in short term benefits.

In conclusion, the coral symbiosis is likely not stable under the current rapid global change in climate and reshaping of abiotic and biotic factors by humans. The only stabilizing factors in face of the challenges the Anthropocene are partner control and resistance to changing conditions, both of which provide at best minimally robustness to the mutualism against, if at all. Thus, the mutualism is likely to become destabilized and eventually breakdown in the face of climate change and the human re-shaping of the biosphere.

Likely conclusion of the coral mutualism

Assuming now that the Scleractinian-Symbiodinian mutualism is likely to undergo mutualism breakdown in face of anthropogenic changes to the environment, it is possible to predict, based on the set-up of the mututalism and differences in evolutionary pressure on partners, the ultimate outcome of the coral mutualism under rapidly changing environments.

Since the Scleractinian host is an obligate mutualist, it is unlikely to convert to autonomy. The main benefit gained from the mutualism by the host is photosynthetic products which range from sugars to amino acids to lipids.16,17 Theoretically, it is possible for corals to obtain these nutrients via heterotrophic means, and indeed there are coral host species that supplement their diet in this way. 28 However, nutrients from symbionts take up a large proportion of the corals nutrition requirements, and there are no known cases of corals, or indeed any obligate mutualist reverting to autonomy. It is possible that the symbiont, which is facultative, would to convert to autonomy. In that case, the host, having lost its partner, would inevitably go extinct since it is unable to survive independent of its mutualist parner.

Despite the possibility of reversion to autonomy, the more likely scenario is evolution of the symbiont into a parasite. From a theoretical stand-point, it is clearly more favorable for the symbiont to be able to parasitize its host rather than convert to autonomy if possible, since it would be able to receive the benefits of a mutualism without incurring the associated costs. With an obligate partner, it may be possible to take advantage of the inherent pressure to maintain the symbiosis to parasitize the host. Indeed, a phylogenetic analysis of mutualisms found obligate mutualisms were more susceptible to parasitism than facultative mutualisms.6 This may do with the fact that facultative mutualists are able to dissociate from parasitic partners and converting to autonomy too quickly for parasitism to appear in the phylogenetic record, or that parasitism is more likely to appear in obligate mutualisms.6 In any case, the evolution of somewhat stable parasitism seems more common in obligate mutualisms than facultative ones, although it may eventually lead to host extinction. This tendency to parasitize the host has in fact been observed in zooxanthellae, which were found to become more “selfish” when conditions becomes unfavorable, for example at higher temperatures.15 There is also a genus of symbionts, Symbiodinium, that are parasitic and take advantage of weakened hosts.19

When parasitism arises from a formerly obligate mutualisms, it is rarely stable. Instead, it usually leads to the extinction of at least one partner and thus the breakdown of symbiosis after mutualism breakdown. In support of this idea phylogenetic evidence suggests that extinction is especially prevalent in obligate mutualisms.6 As discussed earlier, the stabilizing mechanisms Scleractinian hosts employ in the mutualism to guard against symbiont parasitism or the otherwise lack of symbiont cooperation is coral bleaching, the sustained state of which the host cannot survive. Re-infection also cannot occur when under heat stress,14 which under increasing global temperatures is undoubtedly going to occur. So, the likely response of the host towards symbiont parasitism is the death of the host. On the scale of a population, this translates into local or even global extinction. Symbionts, which are facultative mutualists, will likely survive this ordeal, albeit with reduced fitness.

In conclusion, if indeed the likely breakdown as discussed in previous sections occurs in the Scleractinian-Symbiodinian mutualism, the result is most likely parasitism of the host by the symbiont followed closely by host extinction and decreased symbiont fitness. In view of this, it is seems unlikely that this symbiosis, which has endured multiple mass extinction events, will survive this rapid re-structuring of its habitat by humans.

Implications for conservation

In response to the threat that corals are facing in the rapid change in environment that characterizes the Anthropocene, various proposals have been made to conserve this group of species. The importance of conservation is clear given the immense value of coral reefs that not only intrinsically but practically also in terms of ecology, heritage, and the economy. To this end, four major types of conservation strategies have been proposed. 29 In order for conservation efforts to be effective they must conserve not only the host and symbiont species, but also a functional mutualism relationship between the two.

The first of the strategies is a traditional approach where reserves are set up to prevent direct human damage of the habitat. Essentially, it aims to isolate a portion of the habitat away from human influence so it can recover and/or avoid further damage. 30 In addition, recovery has been shown to be promoted by the presence of organisms outside of the mutualism, such as parrotfish that consume algae, providing substrate that corals can grow on. 31 However, positive results are not always achieved, as the effect depends on the community present in the reserve. 32 More importantly, the threat to corals is not only direct human damage to their habitat, but also anthropogenic changes to the environment that the reserve fails to shield corals from. Although it may be easier for corals to recover in marine reserves, their continued survival ultimately depends on the stability of the mutualism itself, which marine reserves cannot ensure. Marine reserves address neither the rapid environmental changes nor the inability of the mutualism to adapt to these changes. Thus, the traditional approach is unlikely sufficient.

The second aims to remove stressors or reduce the intensity of stress on the mutualism. Ideally, it would of course be preferable to control and limit the human impact on the environment, but there is little reason to be optimistic in this regard. Of particular import to corals is carbon emissions, which increases both sea temperatures and acidity. Despite repeated international attempts to curb carbon emissions, little progress has been made.21 Thus in lieu of managing the root cause of the problem, some have suggested instead focusing instead on the “symptoms” of increased carbon emissions, mainly that of increased temperatures. Examples of this include covering reefs with a shade, generating artificial upwelling to lower water temperatures, or geoengineering to control the climate.29 However, these proposals are mostly theoretical, with only the shading method being tested in an extremely limited capacity.33 More importantly, in view of the long-term stability of the mutualism, is that proposed methods would affect more than just temperature, for example shading affects availability of light, which also destabilizes the mutualism since it affects photosynthesis rate. 34 The essential problem is that the coral symbiosis requires multiple aspects of the abiotic environment to fall within their respective acceptable ranges. Thus, recreating an optimal or tolerable environment for corals by targeting various effects of carbon emission is, if possible at all, likely extremely difficult.

The third strategy is increasing resilience of the mutualism. This usually involves genetic engineering, artificial infections, or selective breeding. This method targets the problem of lack of resilience of the coral mutualism by engineering more resilient combinations of host and symbiont. However, coral hosts and symbionts not only differ in resilience to temperature, but also in their cooperativeness. It is important to note that a stable association does not imply a stable or productive mutualism, it could instead be an instance of an unstable parasitism that will eventually lead to host death. For instance, symbionts from the genus Durusdinium (formerly clade D) are more temperature resistant, but also less productive in terms of photosynthesis.35 Indeed, even photobleached Durusdinium symbionts that are unable to conduct photosynthesis have been found continuing to associate with their Scleractinian hosts.36 This suggests that Durusdinium symbiont may in fact be an opportunistic parasite that is normally outcompeted by coorperative symbionts and/or selected against by the host but outcompetes cooperative symbionts when experiencing temperature stress. Thus, selective breeding or artificial infections may not actually aid in the preservation of the mutualism, since more parasitic variants, not more resilient symbionts could be selected for. Also, the specificity of host-symbiont association varies greatly.37 More specific associations, which as discussed are less stable in face of rapid change, are unlikely to be able to be conserved in this way, which lowers the diversity of reef-building corals, which in turn affects the structure of the coral reef habitat. In the case of genetic engineering, the current knowledge of how or why resilience is conferred is inadequate for genetic engineering of symbiont or host. Another complication that may arise is that, as discussed, the fragility of the mutualism in the face of rapid change in related to the mode of maintenance employed by the host, which could make protecting the mutualism from both rapid environmental changes and inherent tendencies toward parasitism a challenge.

As a last resort, it is proposed that preserving the genetic material could allow for artificial re-introduction of corals into the environment in the future. While possible in theory, it is unclear how the introduction would be conducted, and in any case the re-introduction would only be possible after conditions once again become favorable to the coral mutualism. This is unlikely going to happen in the near future, if at all.

In conclusion, except in greatly disturbed habitats, the fragility of corals in the Anthropocene does not originate from direct human destruction, rather the failure of the mutualism to adapt to rapid environmental changes without a fundamental shift in the symbiosis partners engage in. As such, traditional conservation strategies, which seek to limit direct effects of human actives, while important, are unlikely to be sufficient or effective. Other strategies that focus on either reducing the stress or increasing the resilience of the mutualism may be more promising, but there has yet to be a proposal that is feasible with the current technology and knowledge. As a last resort, conservation of genetic material is a possible method to at least conserve genetic material of the mutualists.

Future directions

While the implications of rapid change in environment on the coral mutualism are clear, more knowledge is needed to determine the best way forward to conserve corals and other similar mutualisms.

For one, not enough is currently known about what the subtle but specific differences in the large variety of host-symbiont combinations. As we have seen, the stability of a mutualism is a delicate balance, thus different combinations of host and symbionts likely have different resilience under the rapidly changing environment. Understanding how or why these differences are could illuminate possible options for genetically engineering corals, but more practically allows for the focusing on conservation of more fragile host-symbiont combinations.

In addition to this, most research on the fragility of the coral symbiosis focuses on the effect of temperature. In reality, while temperature is of course a very important factor in the stability of mutualism, there are other changes humans are bringing onto the environment that are stressors to corals. These range from UV radiation from ozone depletion, to eutrophication from pollution, to ocean acidification from carbon emissions. The maintenance of a mutualism does not depend on the optimization of one environmental variable, so research into these human effects could also be helpful in guiding future conservation efforts.

Conclusion

Obligate-facultative mutualisms face the challenge of controlling an uneven evolutionary pressure to parasitize partners. Using corals as an example, this paper discussed how various factors affect the ability of the mutualism to control the tendency towards parasitism in this kind of symbiosis. It is noted that stable mutualisms under stable and rapidly changing environmental conditions have different set-ups. As a result, the previously stable coral mutualism is destabilized in the Anthropocene. While traditional conservation efforts are inadequate in face of this change, new conservation efforts, while still in the early stages of development, have the potential to succeed if they successfully take into account all the intricacies of a mutualism. Thus, more research into how and why mutualisms have different stabilities under various conditions is needed to guide conservation efforts.

2018-12-15-1544891889

...(download the rest of the essay above)

About this essay:

If you use part of this page in your own work, you need to provide a citation, as follows:

Essay Sauce, Stability of obligate-facultative mutualisms (coral). Available from:<https://www.essaysauce.com/environmental-studies-essays/stability-of-obligate-facultative-mutualisms-coral/> [Accessed 27-03-24].

These Environmental studies essays have been submitted to us by students in order to help you with your studies.

* This essay may have been previously published on Essay.uk.com at an earlier date.