Genomics reveals the role of admixture in the evolution of structure among sperm whale populations within the Mediterranean Sea

Abstract

In oceanic ecosystems, the nature of barriers to gene flow and the processes by which populations may become isolated are different from the terrestrial environment, and less well understood. In this study we investigate a highly mobile species (the sperm whale, Physeter macrocephalus) that is genetically differentiated between an open North Atlantic population and the populations in the Mediterranean Sea.We apply high-resolution single nucleotide polymorphism (SNP) analysis to study the nature of barriers to gene flow in this system, assessing the putative boundary into the Mediterranean (Strait of Gibraltar and Alboran Sea region), and including novel analyses on structuring among sperm whale populations within the Mediterranean basin. Our data support a recent founding of the Mediterranean population, around

Threatened cetaceans off the coast of Israel and long‐range movement of a sperm whale

“…Significant research effort to better understand sperm whale abundance, population trends, social behaviour, connectivity and specific localized threats has been undertaken in several regions of the Mediterranean (Boisseau et al, 2024;Frantzis et al, 2014;Gannier et al, 2002;Laran et al, 2017;Lewis et al, 2018;Panigada et al, 2024;Rendell et al, 2014). Genetic data show that there is a distinct subpopulation in the Mediterranean that is listed as Endangered by the IUCN, with fewer than 2500 mature animals (Pirotta et al, 2021;Violi et al, 2023). Threats in the Mediterranean include ship strikes, interactions with fisheries, underwater noise from seismic surveys or military operations and ingestion of marine debris (Blasi et al, 2021;Frantzis et al, 2019;Notarbartolo di Sciara & Gordon, 1997;Notarbartolo-Di-Sciara, 2014;Rendell & Frantzis, 2016).…”

“…Threats in the Mediterranean include ship strikes, interactions with fisheries, underwater noise from seismic surveys or military operations and ingestion of marine debris (Blasi et al, 2021; Frantzis et al, 2019; Notarbartolo di Sciara & Gordon, 1997; Notarbartolo‐Di‐Sciara, 2014; Rendell & Frantzis, 2016). In many regions, particularly the eastern Mediterranean, sperm whale numbers, distribution and threats remain poorly understood, and more research effort is needed considering that some degree of isolation between western and eastern Mediterranean has been recently assessed (Violi et al, 2023).…”

“…Rendell et al (2014) concluded that west–east movements between the populations off the coast of Italy and Greece are rare in the Mediterranean (~1% of whales). Estimates of gene flow from western to eastern Mediterranean indicate a recent and low rate from west to eastern basins (Violi et al, 2023). However, movements between the western Basin and eastern or Levantine Basin have not yet been recorded although this may be due to low research effort.…”