High genetic connectivity of the two main cold-water scleractinian framework engineers from the Southwestern Atlantic

Abstract

Cold-water coral reefs (>150 m) are highly biodiverse ecosystems mainly engineered by few scleractinian and Porifera species. Due to the low number of framework building scleractinian species combined with their low growth rates, cold-water reefs are considered vulnerable marine ecosystems susceptible to human impacts such as demersal fisheries. Apart from their occurrence, a seminal information that subsidizes best practices for their conservation is related to gene flow/population genetics. However, research on the latter is hampered by the expensive sampling logistics and, to date, most studies have focused on the North Atlantic. Here we use microsatellite markers to understand the genetic diversity and population structure of the most important cold-water framework builders in the Southwestern Atlantic, Desmophyllum pertusum and Solenosmilia variabilis. The genotyping of 285 specimens belonging to both species showed low clonality rates, high levels of genetic diversity with no evidence of inbreeding, and no population structure along a latitudinal gradient of nearly 700 km, similar to what has been previously observed for the sympatric species Madrepora oculata and M. piresae. The recurrent absence of population structure for cold-water corals in the Southwestern Atlantic along latitudinal and depth ranges, suggests that oceanographic factors, such as the direction and speed of the Western South Atlantic Central Water and of the Antarctic Intermediate Water, combined with the spawning "window" and the pelagic larval duration (PLD) of these species play crucial roles in their dispersion and connectivity patterns.