Characterization of 25 new microsatellite markers for the fin whale (Balaenoptera physalus) and cross-species amplification in other cetaceans

Characterization of 25 new microsatellite markers for the green turtle (Chelonia mydas) and cross-species amplification in other marine turtle species

BACKGROUND

The green sea turtle, Chelonia mydas, is a migratory species with a strong natal homing behavior leading to a complex population structure worldwide. The species has suffered severe declines in local populations; it is therefore crucial to understand its population dynamics and genetic structure to adopt appropriate management policies. Here, we describe the development of 25 new microsatellite markers specific to C. mydas and suitable for these analyses.

METHODS AND RESULTS

They were tested on 107 specimens from French Polynesia. An average allelic diversity of 8 alleles per locus was reported and observed heterozygosity ranged from 0.187 to 0.860. Ten loci were significantly deviant from the Hardy-Weinberg equilibrium, and 16 loci showed a moderate to high level of linkage disequilibrium (4-22%). The overall F_is was positive (0.034, p-value < 0.001), and sibship analysis revealed 12 half- or full-sibling dyads, suggesting possible inbreeding in this population. Cross-amplification tests were performed on two other marine turtle species, Caretta caretta and Eretmochelys imbricata. All loci successfully amplified on these two species, though 1 to 5 loci were monomorphic.

CONCLUSION

These new markers will not only be relevant for further analyses on the population structure of the green turtle and the two other species, but they will also be invaluable for parentage studies, for which a high number of polymorphic loci are necessary. This can provide important insight into male reproductive behavior and migration, an aspect of sea turtle biology that is of critical importance for the conservation of the species.

Development of 16 novel EST-SSR markers for species identification and cross-genus amplification in sambar, sika, and red deer

Deer genera around the globe are threatened by anthropogenic interference. The translocation of alien species and their subsequent genetic introgression into indigenous deer populations is particularly harmful to the species of greatest conservation concern. Products derived from deer, including venison and antler velvet, are also at risk of fraudulent labeling. The current molecular markers used to genetically identify deer species were developed from genome sequences and have limited applicability for cross-species amplification. The absence of efficacious diagnostic techniques for identifying deer species has hampered conservation and wildlife crime investigation efforts. Expressed sequence tag-simple sequence repeat (EST-SSR) markers are reliable tools for individual and species identification, especially in terms of cross-species genotyping. We conducted transcriptome sequencing of sambar (Rusa unicolor) antler velvet and acquired 11,190 EST-SSRs from 65,074 newly assembled unigenes. We identified a total of 55 unambiguous amplicons in sambar (n = 45), which were selected as markers to evaluate cross-species genotyping in sika deer (Cervus nippon, n = 30) and red deer (Cervus elaphus, n = 46), resulting in cross-species amplification rates of 94.5% and 89.1%, respectively. Based on polymorphic information content (>0.25) and genotyping fidelity, we selected 16 of these EST-SSRs for species identification. This marker set revealed significant genetic differentiation based on the fixation index and genetic distance values. Principal coordinate analysis and STRUCTURE analysis revealed distinct clusters of species and clearly identified red-sika hybrids. These markers showed applicability across different genera and proved suitable for identification and phylogenetic analyses across deer species.

Novel and Broadly Applicable Microsatellite Markers in Identified Chromosomes of the Philippine Dengue Mosquitoes, Aedes aegypti (Diptera: Culicidae)

Dengue is the leading arboviral infection in the Philippines. Its endemicity in the country is due to the presence of its primary mosquito vector, Aedes aegypti (L.). This species has limited microsatellite markers. This study characterized microsatellite markers screened in silico from intergenic regions of the updated reference genome of Ae. aegypti from Liverpool, U.K. Criteria for good markers are: polymorphic, inherited in a Mendelian codominant manner, no null alleles, selectively neutral, randomly associated, and broadly applicable across different regions. Genotypes were scored using ABI Peak Scanner and were screened for the presence of null alleles. Hardy-Weinberg equilibrium, linkage disequilibrium, and robustness of the markers were determined by GENEPOP using Ae. aegypti samples from selected highland and lowland sites (n = 30 each) in the Philippines and outgroups (Thailand and Vietnam). Mendelian codominant inheritance was examined using F1 offspring of Ae. aegypti family (n = 30 each) derived from samples collected from Cebu city highlands and Maramag, Bukidnon. From the 63 randomly selected markers, nine were polymorphic. Two markers (Aaeg1-3D of chromosome 1 and Aaeg3-4C of chromosome 3) satisfied all criteria, hence, are good broadly useful microsatellite markers. Two other markers (Aaeg2-2E of chromosome 2 and Aaeg3-2A of chromosome 3) met all criteria but deviated from Mendelian codominant inheritance. These new markers of the Philippine Ae. aegypti with their chromosomal locations relative to the other published markers are presented, and will ultimately be useful in a variety of population genetic studies of Ae. aegypti to protect the public health.