Different Interspecies Demographic Histories within the Same Locality: A Case Study of Sea Cucumbers, Cuttlefish and Clams in Greek Waters

Abstract

Coalescent methods in population genetics aim to detect biodiversity patterns, evolutionary mechanisms, and signatures of historical changes in effective population sizes with respect to the species fidelity. Restriction site-associated DNA sequencing (RADseq) was used to evaluate the population dynamics of invertebrate species within the same localities. New sequencing technologies, such as the ones employed by population genetics, could be used to improve the management and sustainability of marine and aquaculture resources. Sea cucumbers (Holothuria tubolosa) showed genetic differentiation patterns favoring limited gene flow between studied areas. Similar results for clams (Venus verrucosa) suggest local adaptation and low-dispersal abilities for sessile organisms. On the contrary, cuttlefish (Sepia officinalis) exhibited a panmictic pattern, resulting in a single genetic stock in the area. The larvae settlement duration may be responsible for such interspecies variations. Interspecies demographic modeling revealed different environmental pressures of historical events’ signatures with respect to the three invertebrates. Sea cucumbers favor a post-glacial bottleneck event followed by a more recent recovery, whereas cuttlefish favor an expansion before the late glacial maximum. Lastly, clams showed a constant effective population size in the area. The results of historical demographic changes in natural populations provide opportunities for critical evaluation and management in terms of the conservation of the species in the area.

Population Dynamics of the Demosponge Aplysina Aerophoba (Nardo 1833) in the Mediterranean Sea Using MtDNA COI Gene

“…The high genetic diversity within each A. Aerophoba population contrasts with the high endemism index generally observed in Mediterranean sponge populations (Coll et al, 2010). This pattern of population differentiation between the eastern and western basin (Feidantsis et al, 2022;Pansini et al, 2003;), is also observed in other sponges such as Petrosia ficiformis (Riesgo et al, 2019), while in others such as the commercial Spongia officinalis shows minimal genetic flow (Νm) (Dallianis et al, 2011).…”

“…These environmental changes probably led to different evolutionary forces in the population dynamics of the species (Petit, 2003), and therefore speciation or even bottleneck effect phenomena may drove in species-specific population shrinks (Riesgo et al, 2016). The most important period was during the Pleistocene glaciations (Hewit et al, 2000), where barriers to gene flow and isolated refugia were created (Moura et al, 2014;Feidantsis et al, 2022;Konstantinidis et al, 2022). The later has been argued that, within the Mediterranean Sea various marine organisms show a differentiation pattern between the eastern and the western basin (Moura et al, 2013;Gkafas et al, 2017;Trajer et al, 2021).…”

Admixture of Holothurian Species in the Hellenic Seas (Eastern Mediterranean) as Revealed by RADseq

“…Previous molecular studies of H. tubulosa show a rather strong genetic differentiation between semi-enclosed areas in the eastern Mediterranean [32]. Signatures of historical population demography show a bottleneck event for the species approximately after the Last Glacial Maximum (LGM), revealing a massive loss of genetic diversity, followed by a more recent recovery of the population in the area.…”