A biogeography‐based management forMytilus chilensis: The genetic hodgepodge of Los Lagos versus the pristine hybrid zone of the Magellanic ecotone

Abstract

This study was intended to identify mussel species from the Magellanic ecotone, quantifying interspecific hybridization within Mytilus and depicting the genetic architecture of Mytilus chilensis in its South Pacific range. The analysis comprises the sub‐Antarctic Magallanes Province as a rich ecotone of climates, ecosystems and admixed faunas embedded among the biogeographic regions of the Pacific, the Atlantic, and Antarctica. Highly conserved molecular sequences within species were used to identify species, and polymorphic microsatellites were used to calculate the genetic architecture of M. chilensis. The absence of the invasive species Mytilus galloprovincialis from the M. chilensis range clarifies previous doubts on its expansion southward from the Arauco Gulf. The ubiquitous presence of the typical Glu‐5′‐Me‐15/16 PAP allele of Mytilus trossulus in the Northern Hemisphere might come from hull biofouling, but rather it seems to be an ancient polymorphism conserved in M. chilensis as occurs in blue mussels from other regions of the Southern Hemisphere. There is a very limited connectivity (FST = 0.167) between two latitudinal gene pools of M. chilensis that are highly divergent in composition, architecture, and ecological relevance. Fifty years of aquaculture enhancement in Los Lagos explains its high diversity and genetic heterogeneity among patches, so its mussel management should seek a balance between exploitation and environmental sustainability. The Magellanic ecotone bears a pristine M. chilensis × Mytilus edulis platensis hybrid zone around the Southern Cone, larger (450 km) than previously thought. Such a hybrid zone permeates one of the last remaining wilderness areas in the world (Cape Horn Biosphere Reserve) and is a natural laboratory for addressing introgression, hybridization, and evolution of Mytilus spp. genomes in their last southern frontier.

SNP genotyping revealed a hybrid zone between Mytilus chilensis and M. platensis in southern South America (the Strait of Magellan, Isla Grande de Tierra del Fuego and the Falkland Islands)

“…Despite this, we observe in their works a gradient in species composition in the Strait of Magellan between the Atlantic and Pacific Oceans: Closer to the Atlantic, pure M. platensis are more frequent, and near the Pacific Ocean, pure M. chilensis are predominant (Figure1). This taxa distribution is concordant with the study ofDíaz-Puente et al (2020) describing the coexistence of M. platensis (formerly named M. edulis platensis) with M. chilensis and showing hybridisation between both species in this area. The presence of M. platensis in the Strait of Magellan is not surprising and makes sense because this species inhabits the Atlantic coast of South America(Zbawicka et al, 2018).We do not find any M. edulis individuals nor hybrids involving this taxon in the studied area.…”

“…Interestingly, the hybrid zone is detected only in the Strait and not in the Beagle Channel, suggesting that vessel traffic is not a contributing factor in M. chilensis and M. platensis hybridisation. Nevertheless, maritime traffic can help explain the presence of M. galloprovincialis and M. trossulus alleles in the zone, as reported by other authors using mono-locus markers (Díaz-Puente et al, 2020;Oyarzún et al, 2016).…”

“…Previous studies of taxa composition in the Strait of Magellan were performed using mono-locus DNA molecular markers such as ITS, Glu-5′/Glu-3′, Me15/16 (Díaz-Puente et al, 2020;Illesca et al, 2018;Larraín et al, 2012;Oyarzún et al, 2016;Toro et al, 2005), sequencing the cytochrome c oxidase subunit 1 gene (Borsa et al, 2012). However, the use of mono-locus markers gave conflicting results because they target genomic regions with different evolutionary histories, and not all markers are diagnostic for every species among the Mytilus genus.…”

Seasonal differences in the timing of flight between the invasive winter moth and native Bruce spanworm promotes reproductive isolation

“…The introduction of non-native invasive species into naïve habitats has the potential to result in catastrophic changes in ecosystem function and resilience (Mack et al 2000), and can result in the reductions or even extinctions of native species (Brockerhoff et al 2006, Murrell et al 2011, Gallien and Carboni 2017). Studying invasion events can provide important opportunities to observe evolutionary and ecological processes (Alpert 2006, Prentis et al 2008, Ward et al 2008, Jones and Gomulkiewicz 2012), and these have long been viewed as “natural laboratories” (Herder et al 2012, Paillex et al 2017, Diaz-Puente et al 2020, Ejsmont-Karabin et al 2020, Valencia-Montoya et al 2020). One way in which species invasions can alter evolutionary trajectories and ecological interactions is through hybridization (Havill et al 2012, Zemanova et al 2017, Correa et al 2019, Cordeiro et al 2020, Popovic et al 2021, Andersen et al 2022).…”

Evaluation of Prezygotic Barrier Using Laboratory Crosses Between Three Species of Blue Mussels of The Genus Mytilus, Present Along the Chilean Coast

“…Unfortunately, among some of the main features of these Mytilus species is the well-known capability to naturally hybridize among them in locations where their distributions overlap [8,9], therefore, these alien mussel species could have also the potential for natural hybridization with the native mussel M. chilensis.…”