Biology subjects

Pereyra, R. T.

Publications and source records attributed to Pereyra, R. T..

4 recordsLinked to original sources

bioRxiv2026

Establishing a baseline for standardised genetic monitoring of Atlantic cod (Gadus morhua) in Sweden

Protecting populations and genetic diversity within them is critical to conserving the resilience and adaptive potential of species. Fisheries management has long had the ambition of managing species at the population level, but mainly define "fish stocks" based on geographical limits, which can lead to overfishing of sensitive populations in areas where many different populations coexist. Modern genetic methods are now sufficiently cost-effective, fast, and accurate to be integrated into fisheries management, enabling genetic identification and monitoring of fish populations. Here, we establish a genetic baseline for the commercially important fish Atlantic cod (Gadus morhua) in the waters surrounding Sweden, by using standardised sampling procedures and developing a genetic panel of 4000 single nucleotide polymorphisms (SNPs) for cost-effective assignment of population-of-origin and inversion genotypes. Using the SNP panel, we resolve the geographical distribution of three genetically distinct cod populations in the region: offshore, coastal/Western Baltic, and Eastern Baltic cod. While there is considerable spatial overlap between the three populations, they are genetically differentiated across the entire genome, as well as in genomic regions associated with chromosomal inversions. In addition, heterozygosity and effective population size estimates suggest differences in genetic diversity and rates of genetic erosion, underscoring the need to monitor the genetic diversity within each population separately. Repeating this methodology across years provides a first suggestion for establishing spatiotemporally resolved genetic monitoring of Atlantic cod in Sweden - simultaneously accounting for both population structure within the species and the genetic diversity within populations.

genomics↗

bioRxiv2022

Mixed origin of juvenile Atlantic cod (Gadus morhua) along the Swedish west coast

Cryptic population structure in exploited fish species poses a major challenge for fisheries management. Atlantic cod (Gadus morhua) is a species in which the presence of sympatric ecotypes has been known for a long time, for instance off the coast of Northern Norway. More recently, two sympatric ecotypes of cod have also been documented in the Skagerrak and Kattegat; one ecotype is of an apparent offshore origin and undertakes spawning migrations to the North Sea, and the other is resident at the coast throughout its life. However, their relative contributions of juveniles to the Swedish west coast remain poorly understood. The lack of adult cod along the Skagerrak and Kattegat coasts in recent years has led to the hypothesis that the offshore ecotype is the main source of juveniles to the area, but recent studies have shown large proportions of coastal cod inside Norwegian Skagerrak fjords. In this study, juvenile cod were collected at a high spatial resolution along the Swedish west coast, and genetically assigned to each of the two ecotypes. The results reveal that there is a considerable proportion of juvenile coastal cod in the southern Kattegat, Oresund, and in inshore Swedish Skagerrak, but that the offshore ecotype dominates in offshore areas. Model selection suggests that differences in bottom depth, rather than distance from the open sea, may explain the heterogenous spatial distribution of the two ecotypes. In addition, the two ecotypes displayed differences at loci known to be associated with environmental adaptation, suggesting that their spatial distribution is maintained by natural selection in response to specific environmental conditions.

genomics↗

bioRxiv2022

Clones on the run - the genomics of a recently expanded facultative asexual species

Why, in facultative asexual species, marginal populations are often richer in clones than are core populations, remains unclear. Cloning freezes genotypes but hampers recombination and local adaptation. During expansion, clones are favoured over non-selfing sexuals by uniparental reproduction. To better understand the dynamics of clones and sexual lineage, we used genome-wide sequencing to analyse a recently expanded seaweed. We found large clones and sexual populations mixed close to range margins. Clones had evolved repeatedly from sexual populations but were unexpectedly low in genetic variation. Modelling suggested clones form from sexual populations after repeated bottlenecks at the expansion front. A clonal wave of depauperate genotypes thereafter spread ahead of the sexual population. As we observed, these early formed clones may survive side-by-side sexual individuals, which suggests they lost their sexual capacity. Our study illustrates how range expansion can result in complex and dynamic patterns of genetic variation in facultative asexual species. TeaserWe use genome data and modelling to find out why large clones are only found at range margins in a recently expanded seaweed

evolutionary biology↗

bioRxiv2019

Strong spatial genetic structure in a Baltic Sea herbivore due to recent range expansion, multiple bottlenecks and low connectivity

In the Baltic Sea, recent range expansions following the opening of the Danish straits have resulted in a low-diversity ecosystem, both among and within species. However, relatively little is known about population genetic patterns within the basin, except for in a few commercially caught species and some primary producers thought to be ecosystem engineers. Here, we investigate the population genetic structure of the ecologically important crustacean Idotea balthica throughout the Baltic Sea using an array of 33,774 genome-wide SNP markers derived from 2b-RAD sequencing. We also generate a biophysical connectivity matrix, with which we compare the genomic data. We find strong population structure on small scales across the Baltic Sea, and that genomic patterns in most cases closely match biophysical connectivity, suggesting that current patterns are important for dispersal of this species. We also find a strong signal of multiple bottlenecks during the initial range expansion, in the form of reduced heterozygosity along the historical expansion front. The lack of gene flow among sampling sites in the Baltic Sea environmental gradient potentiates local adaptation, while at the same time also increasing genetic drift in low-diversity areas.

evolutionary biology↗