Adaptation refers to when a species changes to become better fitted to the environment as a result of natural selection. Adaptations generally occur in order to increase the fitness and thus survival of organisms. By being able to adapt to the changing environment, organisms are better able to survive and reproduce.
can be considered at the species level, but a recent study
, performed by Kelly et al., involving Tigriopus californicus
shown that that may not be sufficient to accurately predict the effects of climate change on a species. T. californicus
has isolated populations scattered through a wide latitudinal range. These populations have great disparities in terms of their thermal tolerance and their ability to adapt to a new thermal tolerance. This data suggests that in order to accurately predict the effects that a changing temperature and climate will have on a species, it is necessary to look at the variance in adaptation potential in different populations of that species.
Many people are under the impression that species require thousands or even millions of years to adapt. This article
by Carl Zimmerman explains how evolution can actually occur in surges, a feature of evolution that proves very useful during periods of climate change. It is important to also note that evolution continues to occur long after climate change has stabilized. Delayed reactions continue to change allele frequencies and compositions of populations.
and the rate of climate change are important factors in determining if a species will be able to adapt.
- The phenotypic plasticity of species of brown trout are heritable. If the rate of climate change is slow enough that organisms at the upper range of tolerance can survive, then there is a chance that the species can adapt over time by inheriting this tolerance.
- The rate that a species can adapt is related to how drastic of a temperature change it could survive and adapt to. In the case of T. californicus, the fragmented population means that there is large variation in the species (and thus large potential for adaptation), but lower opportunity for adaptation within the individual populations.
- A greater amount of variation is indicative of a population that can more readily adapt, as evidenced by this article showing that S. franciscamus,a species of sea urchin, is more likely to be able to adapt to increased carbon dioxide levels than the mussel species M. trossulus over the next 50 years.
- A review published this year reiterated the idea that most organisms, marine or terrestrial, have only limited temperature ranges in which they can live, representing their plasticity. Evolutionary changes to this range are considered long-term. In this review, the focus is on Arctic marine organisms, which have extended their temperature ranges to include very cold temperatures.
An organism at the edge of its thermal tolerance may have more difficulty adapting.
- Among congeneric invertebrates, those adapted to the warmest environments are most susceptible to local extinction. In contrast, some Arctic marine ectotherms have lost the ability to adapt to rising temperature.
- The lowering pH of the oceans affects the ability of certain marine organisms to calcify their skeletons.
- Some corals have the ability to up-regulate the pH at calcification, thus increasing calcification rates with relatively low energetic cost. Even though there is some loss of fitness among these coral, those species of coral without this mechanism will be at a disadvantage if ocean pH levels continue to lower.
Regulation of gene expression is an important consideration, as it could lead to adaptation.
- In the review previously mentioned, it was shown that of 189 up-regulated genes in carp, 94% were as a result of adaptation to colder temperatures. In D. mawsoni, 101 protein-coding genes were duplicated.
Evolutionary responses to climate change
- We looked at a very interesting article for week 9. Although the entire article was very alarming, the most fascinating part of the article was at the end.
- "Moreover, these threats will not be fully realized until all the extinction and evolutionary debts are paid long after climates stabilize. Future biodiversity changes will spur additional and less predictable impacts on ecosystem services, global food production and human health."
- Many articles have been published to discuss the current effects of climate change on current populations or future populations if climate change continues. Unfortunately, as this article points out, it is extremely possible that threats will continue long after the climate stabilizes. This being said, it is important that more studies are published similar to this one. These studies need to go into more depth about projecting how long it will take after the climate stabilizes to fully realize the extinction and evolutionary debts that have occurred due to climate change.
According to the Willis and MacDonald paper, adaptation is considered as a mechanism for responding to climate change much less frequently than extirpation and migration. However, recent studies of past periods of extreme climate change have yielded results that may help predict how current species will adapt to the changing climate. During the Paleocene-eocene Thermal Maximum (PETM), one of the most pronounced periods of warmth in the last several hundred million years, it appears that persistence was the most common response in plant life. Three adaptive features may help to explain this:
- Many of these species had a very wide ecological tolerance and thus are able to adapt to greater temperature variance.
- The increase in CO2 during the PETM actually increased the ability of photosynthetic species to adapt and survive.
- The plants that were unable to adapt were restricted to very small environments that they could survive in and persisted there.
These adaptations in plants may give us some idea of how and which marine species, particularly aquatic plant-like species, may adapt to future climate change.
Adaptation should be distinguished from acclimation:
- One of the difficulties with studying adaptation is that it can often be confused with plasticity (acclimation). In this paper, Hoffman states that when these two responses to climate change can be separated, plasticity is often the more important factor. There is also an emphasis on the difference between adaptions in time and space. Adaptations can occur in one location over a period of time, through moving to a different location, or a combination of the two.
Species that adapt most effectively often have specific qualities:
- In most of the studies we've read, the adaptations of smaller organisms were discussed. These smaller organisms frequently have larger population sizes and higher rates of mutation. Pyenson's paper, however, looks at the responses of whales to climate change during the Pleistocene and finds that they actually have the ability to acclimate to the changing environment. They do this by shifting to a filter-feeder mode when their primary feeding ground disappears. However, because this is an acclimation as opposed to an adaptation, the ability of whales to evolve novel traits is not completely known.
- An important consideration for the topic of adaptation is when species actually fail to adapt. In the Nature Climate Change paper concerning an endangered marine turtle population, climate change was found to be likely to decrease the hatchling success and emergence rates. These consequences were mainly due to a 2.5 degree temperature increase on the nesting beach as predicted by climate change models, but changes in the marine environment did not make as much of a difference. These marine turtles apparently lack the diversity to adapt to different terrestrial conditions.
- It is important to be able to identify species at the greatest risk of extinction in order to focus conservation methods. These species are often ones with a low ability to adapt. This could be caused by the species having DNA decay in important genes, having low genetic variance, or phyletically conservative. Many threatened species are geographically isolated with limited options for dispersal with this new climate change. Many isolated species are stuck where they are because they are small populations with low genetic variance. In these situations, conservationists need to concentrate on increasing these species' adaptive potentials. This could include connecting these isolated groups to other populations in order to increase genetic variance and, as a result, their adaptability.