{"id":1937,"date":"2021-05-21T15:46:50","date_gmt":"2021-05-21T22:46:50","guid":{"rendered":"https:\/\/coral.org\/news\/new-research-turns-basic-ecological-theory-on-its-head\/"},"modified":"2021-11-02T10:27:44","modified_gmt":"2021-11-02T17:27:44","slug":"new-research-turns-basic-ecological-theory-on-its-head","status":"publish","type":"post","link":"https:\/\/coral.org\/en\/blog\/new-research-turns-basic-ecological-theory-on-its-head\/","title":{"rendered":"New Research Turns Basic Ecological Theory on its Head"},"content":{"rendered":"

In a lot of ways, corals are like trees\u2014they stay rooted in one spot their whole lives, and they disperse their young into the environment. With many trees, their young typically fall to the ground and stay relatively close. But with corals, their young are moved by ocean currents that can carry them thousands of miles away. No squirrel can carry an acorn that far!<\/span><\/p>\n

Understanding how coral reefs are connected to each other through the movement of coral larvae (baby corals) is vital to our work saving coral reefs.\u00a0<\/span><\/p>\n

\"Beautiful
Corals are sessile species, meaning they spend their whole lives in one spot and find ways to breed without moving. Photo: Hitoshi Namura via Unsplash<\/figcaption><\/figure>\n

Research shows that corals are adapting to the effects of climate change, like warming ocean temperatures. And when a coral adapts to become more heat tolerant, it can spread those heat tolerant traits by sending its coral babies to other reefs. We can encourage that evolutionary process by keeping coral reefs healthy.\u00a0<\/span><\/p>\n

But how do we prioritize one location over another? How do we know where to focus our efforts, and where to keep coral reefs healthy? We start by looking at population connectivity\u2014or in this case, the way coral reefs are connected to each other by ocean currents.\u00a0<\/span><\/p>\n

Basic ecological theory tells us that in sessile species (species that don\u2019t move, like corals), a population will be better off if it has random connections to other populations. For example, coral reefs that can send and receive coral larvae from a random mix of other coral reefs\u2014near or far, in hot or cold water\u2014will have more abundant populations of corals.\u00a0<\/span><\/p>\n

\"Diverse
Having diverse networks of coral reefs helps make a reef more resilient to widespread diseases. Photo: Francesco Ungaro via Unsplash<\/figcaption><\/figure>\n

The theory makes sense: having networks that are more random likely leads to more diversity, which lowers the chance of something like a disease wiping out a population.<\/span><\/p>\n

But new research by our partner, Dr. Lisa McManus of the Hawai’i Institute of Marine Biology, says that\u2019s not necessarily true when you add evolution and climate change into the mix.\u00a0<\/span><\/p>\n

McManus and team created two mathematical models to simulate two different ways populations could be connected to each other. The first was one with random connections\u2014this was called the random network model. The second, called the regular network model, represented a network where populations were only connected to other populations that had similar temperatures and environments.\u00a0<\/span><\/p>\n

\"Regular<\/p>\n

\u201c<\/span>This study was not about any particular organism,\u201d says McManus. \u201cBut we can translate these results to corals by thinking of populations as reefs that are experiencing relatively hot or cold temperatures within a reef network.\u201d<\/span><\/p>\n

When they first ran the models without evolution, basic ecological theory was correct: the random network did lead to a larger average population over time.\u00a0<\/span><\/p>\n

But then they allowed populations to evolve in the model and got very different results. When natural selection was thrown into the mix, the regular networks performed better. McManus says that\u2019s because the types of connections influenced whether evolution helped or hindered adaptation.\u00a0<\/span><\/p>\n

\u201cThe random networks didn\u2019t perform as well,\u201d says McManus. \u201cAs temperatures increased, the reefs in cooler waters did well because they were receiving already-adapted heat-tolerant corals from the reefs in hotter waters. But you also had the coldest individuals arriving in the warmest sites, and they didn\u2019t do so well. Overall, the populations ended up declining.\u201d\u00a0<\/span><\/p>\n

She refers to the influx of corals from cold locations arriving in warm locations as gene swamping, where poorly adapted individuals spread genes that don\u2019t help a population thrive.<\/span><\/p>\n

In contrast, in the regular networks, the warmer reefs were more isolated from cold sites and so were able to adapt without an influx of cold-water corals, leading to higher population abundance overall.\u00a0<\/span><\/p>\n

\u201cThe warmer patches of reefs weren\u2019t reliant on this immigration of pre-adapted individuals,\u201d says McManus. \u201cThey were already in warmer water, so there were no other individuals that could save them. The only way they could survive is if they evolved on their own. In the regular networks, the warmer patches were able to adapt because they were relatively isolated from the colder patches.\u201d\u00a0\u00a0<\/span><\/p>\n

McManus recognizes that this research is based on a very simplistic view of coral reef connectivity, but that doesn\u2019t take away from its importance.\u00a0<\/span><\/p>\n

\u201cReal reef systems are probably a combination of these two types of networks,\u201d she says. \u201cIn our models, you have one extreme where coral reefs are only connected to reefs that are similar to them, and you have another extreme where coral reefs are only connected to reefs that are really different. In the real world, coral reefs are probably connected to both.\u201d\u00a0<\/span><\/p>\n

\"coral
In nature, coral reefs likely have a combination of random and regular connections to other coral reefs. Photo: Daniel Pelaez Duque via Unsplash<\/figcaption><\/figure>\n

For McManus, the biggest takeaway from this project is that it highlights the importance of considering evolution when building a conservation strategy.\u00a0<\/span><\/p>\n

\u201cThis study points to the importance of evolutionary capacity,\u201d says McManus. \u201cThere\u2019s an interaction between evolution, connectivity, and environmental heterogeneity\u2014those three components all intersect. This allows us to understand that relationship better and move forward with more realistic and more complex applications of this model that better represent real life.\u201d\u00a0<\/span><\/p>\n

That next level, applying these models to more complex and realistic scenarios in specific coral reef regions around the world, is work that McManus has also completed and has just been accepted for publication at Global Change Biology. That study focuses on reefs in the Caribbean, the Indo-Pacific, and the Southwest Pacific to better understand the regional coral reef characteristics that lead to a population\u2019s persistence or decline.\u00a0<\/span><\/p>\n

The results will help us, and coral scientists and conservationists around the world, determine the most effective ways to protect coral reefs in those three geographic regions and create the conditions that will allow them to adapt to climate change.\u00a0<\/span><\/p>\n

For Dr. Madhavi Colton, our Executive Director and one of the founding members of this research group that is exploring how corals adapt to climate change, this new study helps prove something we\u2019ve suspected all along.\u00a0<\/span><\/p>\n

\u201cIf you take a view of the world in which these systems are not actively evolving, then the conclusions you draw about the future and the conservation actions that are needed are likely to be wrong,\u201d says Colton. \u201cThese systems are actively evolving, and once you start thinking about evolution, it changes everything.\u201d\u00a0<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

In a lot of ways, corals are like trees\u2014they stay rooted in one spot their whole lives, and they disperse their young into the environment. With many trees, their young typically fall to the ground and stay relatively close. But with corals, their young are moved by ocean currents that can carry them thousands of… Continue Reading →<\/a><\/p>\n","protected":false},"author":1,"featured_media":685,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","_genesis_transparent_header":false,"_genesis_hide_siblings_nav":false,"_genesis_hide_flyout":false,"_genesis_subtitle":"","_genesis_subheading":"","footnotes":""},"categories":[293],"tags":[300,361,309],"class_list":{"0":"post-1937","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science-news","8":"tag-global","9":"tag-lookback","10":"tag-science","11":"entry"},"acf":[],"template_part":"\n

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