Reconstructing the Evolutionary History of Pinna nobilis: New Genetic Signals from the Past of a Species on the Brink of Extinction

Abstract

Pinna nobilis, commonly known as the noble pen shell, is a marine bivalve endemic to the Mediterranean Sea. Unfortunately, due to a multifactorial disease that began affecting its populations in 2016, the species is currently facing the threat of extinction. To gain insights into the evolutionary history of P. nobilis before the mass mortality event (MME), and to obtain a comprehensive understanding of how evolutionary processes led to the adaptation of the species into the Mediterranean Sea, phylogenetic and phylogeographic analyses were carried out. The dataset analysed includes 469 sequences of COI gene fragment both from GenBank and the present study (100). The analysis performed evidenced that P. nobilis diverged about 2.5 mya, after the entrance of its ancestor into the Mediterranean Sea following the Zanclean flood (5.33 mya). Moreover, our results suggest that the starting point of colonisation was the central part of the western Mediterranean basin, with the eastern basin being populated subsequently. From a conservational viewpoint, these results provide important hints for present and future restocking plans, helping to reconstruct the pre-existing genetic variability in sites where the species became extinct.

A Tale of Two Sisters: The Southerner Pinna rudis Is Getting North after the Regional Extinction of the Congeneric P. nobilis (Mollusca: Bivalvia)

“…The large fan-shell genus Pinna is represented by two species in the Mediterranean Sea: the endemic P. nobilis Linnaeus 1758 [1], and the (sub)tropical Atlantic P. rudis Linnaeus 1758 [2]. P. rudis is recognised as the sister taxon of P. nobilis [3], and hybrids nobilis × rudis are also known [4]. Notwithstanding its broader geographical range, in the Mediterranean Sea P. rudis is less common than P. nobilis, being mainly restricted to the warmest southwestern regions of the basin [5].…”