Parentage Analysis in Giant Grouper (Epinephelus lanceolatus) Using Microsatellite and SNP Markers from Genotyping-by-Sequencing Data

Establishment of Parentage Identification Method for Sea Urchin Strongylocentrotus intermedius Based on SSR-seq Technology

To establish a parentage identification method for Strongylocentrotus intermedius, 15 microsatellite loci and simple sequence repeat sequencing (SSR-seq) technology were used to perform SSR sequencing and typing of the validation population with known pedigree information and the simulation population. Cervus v3.0 was used for gene frequency statistics, simulated analysis, and parentage identification analysis. The results showed that, in validation population, using 15 microsatellite loci, the highest success rate of parent pairs identification was 86%, the highest success rate of female parent identification was 93%, and the highest success rate of male parent identification was 90%. The simulated population was analyzed using 12-15 loci, and the identification rate was up to 90%. In cases where accurate parentage was not achieved, individuals could exhibit genetic similarities with 1-3 male or female parents. Individuals identified as lacking a genetic relationship can be selected as parents to prevent inbreeding. This study shows that parent pairs or single parents of most offspring can be identified successfully using these 15 selected loci. The results lay a foundation for the establishment of a parentage identification method for S. intermedius.

Genetics reveals shifts in reproductive behaviour of the invasive bird parasite Philornis downsi collected from Darwin’s finch nests

Due to novel or dynamic fluctuations in environmental conditions and resources, host and parasite relationships can be subject to diverse selection pressures that may lead to significant changes during and after invasion of a parasite. Genomic analyses are useful for elucidating evolutionary processes in invasive parasites following their arrival to a new area and host. Philornis downsi (Diptera: Muscidae), the avian vampire fly, was introduced to the Galápagos Islands circa 1964 and has since spread across the archipelago, feeding on the blood of developing nestlings of endemic land birds. Since its discovery, there have been significant changes to the dynamics of P. downsi and its novel hosts, such as shifting mortality rates and changing oviposition behaviour, however no temporal genetic studies have been conducted. We collected P. downsi from nests and traps from a single island population over a 14-year period, and genotyped flies at 469 single nucleotide polymorphisms (SNPs) using restriction-site associated DNA sequencing (RADSeq). Despite significant genetic differentiation (FST) between years, there was no evidence for genetic clustering within or across four sampling years between 2006 and 2020, suggesting a lack of population isolation. Sibship reconstructions from P. downsi collected from 10 Darwin’s finch nests sampled in 2020 showed evidence for shifts in reproductive behaviour compared to a similar genetic analysis conducted in 2004–2006. Compared with this previous study, females mated with fewer males, individual females oviposited fewer offspring per nest, but more unique females oviposited per nest. These findings are important to consider within reproductive control techniques, and have fitness implications for both parasite evolution and host fitness.

AutomAted RepeaT Identifier (AARTI): A tool to identify common, polymorphic, and unique microsatellites

Here we are presenting an automated computational pipeline used to mine 5976 mitochondrial genomes to identify common, polymorphic, and unique microsatellites also known as simple sequence repeats (SSRs). Microsatellites are repetitive motifs of 1-6 bases in a DNA sequence. Due to their abundance and highly polymorphic nature, microsatellites have become one of the widely used molecular/genetic markers valuable for many studies including gene tagging, genetic diversity, and species identification. Several computational tools dedicated to mine and categorize microsatellites in nucleotide sequences were developed; however, there is no tool which can identify unique, common and polymorphic microsatellites between each pair of nucleotide sequences. To explore such microsatellites, we have developed a fully automated computational pipeline named AutomAted RepeaT Identifier (AARTI). The AARTI is the only tool till date, which identifies common, polymorphic, and unique microsatellites between each pair of nucleotide sequences. The computational pipeline was constructed using the PERL programming language and the web server for the pipeline was developed with the help of PHP, HTML, CSS, and JavaScript. It was successfully tested to reproduce the results of previous study on 7 mitochondrial genomes of genus Orthotrichum. Moreover, the pipeline was also applied on 5846 (Metazoa) and 130 (Viridiplantae) mitochondrial genomes. The AARTI is freely available at https://lms.snu.edu.in/aarti/ and will certainly accelerate the studies of length variation in microsatellites between species. Additionally, it will be useful in comparative genomic studies, for the computational characterization of microsatellites, and has the potential to be a routine genome analysis pipeline for mitochondrial genomes.

Maintenance of Genetic Diversity of Black Sea Bream despite Unmonitored and Large-Scale Hatchery Releases

Stock enhancement, used for replenishing depleted wild finfish populations, is an aggressive approach. Stock enhancement projects in Taiwan involve black sea bream (Acanthopagrus schlegelii), a major commercial species. During 2004-2015, even management agencies conducted stock enhancement projects, leading to numerous private releases that have not been recorded. Stock enhancement by a private hatchery without accurate genetic records may lead to a genetic structure change in wild populations. Using allele frequencies at nine microsatellite loci, we studied the genetic effects of stock enhancement in 19 samples collected from populations in the hatcheries and the wild. In 458 individuals from nine hatchery samples, most populations showed weak but significant genetic differences and complex clusters in structure analysis, indicating dramatic stock change within and among hatcheries. The 10 wild populations (n = 773) also had a complex genetic composition and were genetically different among sampling sites and times. However, a simple and clear cluster in structure analysis was found for only one sampling site, which had no release history. Thus, stock enhancement with complex genetic sources helps maintain genetic diversity but dramatically changes the genetic structure within and among wild populations, especially when stock enhancement is successful.

Microsatellite-Based Genetic Structure and Hybrid Detection in Alpacas Bred in Poland

This study aimed to characterize the population structure and genetic diversity of alpacas maintained in Poland using 17 microsatellite markers recommended by the International Society for Animal Genetics. The classification of llamas, alpacas, and hybrids of both based on phenotype is often difficult due to long-term admixture. Our results showed that microsatellite markers can distinguish alpacas from llamas and provide information about the level of admixture of one species in another. Alpacas admixed with llamas constituted 8.8% of the tested individuals, with the first-generation hybrid displaying only 7.4% of llama admixture. The results showed that Poland hosts a high alpaca genetic diversity as a consequence of their mixed origin. More than 200 different alleles were identified and the average observed heterozygosity and expected heterozygosity values were 0.745 and 0.768, respectively, the average coefficient of inbreeding was 0.034, and the average polymorphism information content value was 0.741. The probability of exclusion for one parent was estimated at 0.99995 and for two parents at 0.99999.