Changes in oceanographic fronts affect the gene flow among marine crab populations
In the Mediterranean and Atlantic Oceans, the intensity and location of the oceanographic fronts that limit gene connectivity between populations of marine crabs vary over time. These dynamic changes, described in an article published in the journal Scientific Reportsalter the gene structure of the populations of marine crabs of commercial and gastronomic importance.
The new study is led by experts Francesc Mestres, from the Faculty of Biology and Biodiversity Research Institute at the UB (IRBio), and Pere Abelló, from the Institute of Marine Sciences (ICM-CSIC), and provides data of scientific interest. to improve conservation and commercial exploitation policies for these crustaceans.
Among the co-authors of the study are Concepción Arenas lecturer and bachelor’s and master’s students Víctor Ojeda, Bruna Serra, Clàudia Lagares, Eva Rojo-Francàs and Maria Sellés, from the Faculty of Biology at the UB, as well as other experts from the Spanish Institute of Oceanography (IEO-CSIC).
Oceanographic fronts are dynamic and changing
Ocean currents can modulate gene flow – ie the passing of genes between populations of the same species – in the oceanic environment. This genetic connectivity is a fundamental factor in biological evolution.
In terrestrial animals, the various natural barriers – mountains, rivers, deserts, etc. – can reduce this gene migration between populations. In the case of the marine environment, the classical view was that organisms, in adult or larval stages, could move freely in the water and transfer their genes without interference. However, there is growing evidence for the role of oceanographic fronts – marine discontinuities resulting from the movement of water bodies – in limiting the movement and distribution of marine species.
Ocean currents can move the organisms to great distances, but they can produce eddies and eddies, which generate oceanographic fronts and restrict gene flow between populations, even if they are geographically close to each other, notes Professor Francesc Mestres of the Department of Genetics, Microbiology and Statistics of the University Library.
“The study,” he continues, “emphasizes that the intensity and location of these fronts can vary over time, generating these oceanographic dynamics and a large transient variability in the connection patterns between species.”
Harbor crabs as a study model
The team focused their research on the harbor crab (Liocarcinus depurator), a commercially important decapod crustacean – a common element in fish soup and rice dishes – that lives in the muddy seabeds of the continental shelf, between 50 and 200 meters deep.
The populations of this crab were sampled from 2014 to 2019 during the IEO-CSIC MEDITS and ARSA fishing and oceanographic campaigns, totaling seven marine populations from the Atlantic-Mediterranean transition: Cadiz, Western and Eastern Alboran Sea, Alicante , Valencia, Ebro Delta and Northern Catalonia. Some crab populations were located on both sides of the oceanographic barriers of the western Mediterranean basin: most notably the Strait of Gibraltar (GS), the Almeria-Oran Front (AOF) and the Ibiza Chanel (IC).
To analyze gene flow and genetic variability of populations, the team studied a fragment of the mitochondrial gene cytochrome oxidase subunit I (COI), one of the most widely used in ecological and evolutionary studies. A total of 966 sequences of the gene were analyzed in sea crabs from the above populations.
“In particular, the adult crabs analyzed in a given year were dispersed the previous year, when they were in larval form, so that they could provide information about the state of currents and fronts from the previous year,” notes the expert Pere Abello (ICM) op. -CSIC).
The analysis of the temporal series data shows that there are two well-defined hablogroups of gene sequences in the study area: the Atlantic Ocean (ATL) and the Mediterranean Sea (MED), which are more prevalent in the Atlantic and Mediterranean, respectively.
“The population distribution of haplotypes (combinations of alleles) varies over the time period analyzed due to the existence of oceanographic barriers. For example, in the case of the Strait of Gibraltar, a statistically significant effect on gene flow reduction was found in four of the six years studied. The Almeria-Oran front is also a major barrier, but its location and effects on gene flow varied over the years, notably only in the year when the front moved toward the center of the Alboran Sea, a significant effect on gene flow reduction was detected in the Ibiza Channel, another oceanographic front,” says Francesc Mestres.
Therefore, the joint study of all populations over the different years has made it possible to define three areas based on the genetic content of the crabs found in the Atlantic-Mediterranean transition zone: the Gulf of Cadiz, the Alboran Sea and the Levantine Sea. Catalan populations.
“These results are of particular importance for the proper definition of the Marine Protected Areas and also for improving conservation and fisheries management policies for this sea crab. Especially in a context of global change with increasing temperatures that could threaten these animal populations.” the research team concluded.
Study analyzes the distribution of fish larvae in the western Mediterranean
Víctor Ojeda et al, Annual fluctuations in connectivity among crab populations (Liocarcinus depurator) along the Atlantic-Mediterranean transition, Scientific Reports (2022). DOI: 10.1038/s41598-022-13941-4
Quote: Changes in oceanographic fronts affect gene flow among marine crab populations (2022, June 29) retrieved June 29, 2022 from https://phys.org/news/2022-06-oceanographic-fronts-affect-gene-marine.html
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