Unveiling the unknown phylogenetic position of the scallop Austrochlamys natans and its implications for marine stewardship in the Magallanes Province

Sebastián Rosenfeld,Camille Detrée,Claudia S Maturana,Zambra López,Elie Poulin,Francisco Bahamonde,Cristian Aldea,Andrés Mansilla,Karin Gérard,Jaime Ojeda

doi:10.1038/s41598-021-86492-9

Abstract

Two species of scallop, Austrochlamys natans (“Ostión del Sur”) and Zygochlamys patagonica (“Ostión patagonico”) are presently exploited in the southern part of the Magallanes Province (MP). The lack of clarity in taxonomic identification and ecological aspects is generating both erroneous extraction statistics and an unperceived harvesting pressure on A. natans and Z. patagonica. We aim to discriminate these Magallanes scallops accurately, improve our understanding of their complex natural history and discuss possible implications for their management and conservation status, given the current fisheries statistics. To achieve these goals, we present a complete review of the historical identification of the Magallanes scallop and a multi-locus molecular phylogeny which allowed us to recover the phylogenetic position of A. natans. We sampled 54 individuals from five localities across the southern Pacific coast of the MP. We calculated the depth of the byssal notch (BND) and shell height (VH) ratio from morphological characters and conducted phylogenetic reconstructions with mitochondrial (12S and 16S) and nuclear markers (28S) using Bayesian and maximum likelihood analyses. Both morphology and molecular phylogeny identified two distinct entities, Z. patagonica and a distinct, highly divergent lineage that corresponds to A. natans. Our study provides integrative evidence to alert the current fishery management and the need for further conservation studies.

Highlights

The Pectinidae are one of the most morphologically, behaviourally and biologically diverse families in the class Bivalvia[1]
Ar. purpuratus, A. natans and Z. patagonica have been exploited commercially[12]. Both A. natans and Z. patagonica are distributed from the Chiloé Archipelago (42°S) to Cape Horn (55°S)[13], but only Z. patagonica extends its distribution along the Atlantic coast up to Uruguay[14]
In the 1990s the Chilean National Fishing Service (SERNAPESCA) established a criterion for the scallop fishery based on the maximum length and established the minimum catch size as 75 and 55 mm, respectively for A. natans and Z. patagonica

Summary

Introduction

The Pectinidae (scallops) are one of the most morphologically, behaviourally and biologically diverse families in the class Bivalvia[1]. Waloszek[19,20] performed a comparative morphological study of the two species, concluding that they differ in spermatozoid head shape, shell texture and growth parameters, conclusive evidence was not provided mainly because of the overlapping of morphological c haracters[16] This lack of clarity is generating a complex scenario in which the characters traditionally used would not be discriminating between the species; A. natans has not been included in any current p hylogeny[3,4,7,11] so its phylogenetic position is unknown. Stakeholders of the fishing industry and artisanal fishermen have suggested reducing the minimum catch size 23 All this historical background indicates a complex scenario in which banks of Z. patagonica could be considered as banks of small A. natans and fisheries reports are considering mixed banks as monospecific. It is very relevant to be able to identify the two species correctly and to know the phylogenetic position of A. natans in the context of the regional fisheries and future conservation strategies

Objectives

Methods

Results

Conclusion