An international team of researchers has studied 324 islands in tropical and temperate zones of the planet, including the Canary Islands, to determine how sea fluctuations have shaped the evolution of marine life, and how some of them connect or separate depending on sea level.
This study, titled Extending the sea-level sensitive dynamic model of marine island biogeography to include fusion-fission islands, was led by researcher Sérgio Ávila, from the University of the Azores, and among its participants is Esther Martín-González, curator of the Museum of Natural Sciences of Tenerife.
This is a work that reveals how sea level fluctuations during glacial-interglacial cycles have shaped the evolution of marine life on the islands and provides a novel perspective on how shallow-water marine species originate, disperse and become extinct.
The team has developed an extension of the marine island biogeography model, integrating for the first time the dynamics of fusion and fission of islands, that is, how some islands connect or separate depending on sea level, according to information provided by the Museum of Natural Sciences of Tenerife.
This new perspective allows us to understand how these physical changes in the environment directly influence key biological processes such as speciation or extinction.
Thus, the researchers propose an original classification of islands according to their behavior in the face of sea level variations, so that there would be "Solum islands", which never connect with other neighboring islands, not even during extreme sea declines.
Another category is that of "Soror Islands", which merge and separate cyclically depending on changes in sea level, and "Moliones Islands", which are permanently connected by shallow waters, no matter what happens with sea level.
The study analyzes a total of 324 islands located in tropical and temperate zones of the planet, and among them are the Canary Islands, which gives a special local relevance to this research.
In total, the set was divided into 50 Solum islands, 77 islands grouped into 20 Soror sets, and 197 islands belonging to 34 Moliones groups.
One of the strengths of the study is the analysis of the island coastal area, the submerged coastal zone where much of the marine biodiversity is concentrated.
The authors identify five general types of curves of change in this area over time, depending on factors such as the geological age of the islands, their tectonic structure, the presence of underwater terraces and coral reefs.
The work allows us to anticipate more accurately how marine populations fragment, disappear or merge again over time, which has direct implications for the conservation of marine biodiversity in island contexts.
This study highlights that islands are not simply isolated points in the ocean, but dynamic systems whose geological history and behavior in the face of the sea profoundly condition the life that inhabits them.
"We discuss the variations in the coastal area due to Pleistocene sea level changes and their effect on the evolutionary rates of division, extinction and fusion of populations, as well as on the speciation rates of shallow-water marine organisms," the researchers note in the article.
They also point out that the study provides several predictions about the frequencies of events of division, extinction and fusion of marine populations, as well as about the speciation rates of shallow-water marine organisms, according to the respective types of islands.