Showing papers by "Andrew L. Johnson published in 2023"
TL;DR: In this paper , the authors investigated whether the bivalve Angulus benedeni benedai is suitable as a climate archive and found that it is pristine and not affected by diagenetic processes.
Abstract: Abstract. Bivalves record seasonal environmental changes in their
shells, making them excellent climate archives. However, not every bivalve
can be used for this end. The shells have to grow fast enough so that micrometre-
to millimetre-sampling can resolve sub-annual changes. Here, we investigate
whether the bivalve Angulus benedeni benedeni is suitable as a climate archive. For this, we use ca.
3-million-year-old specimens from the Piacenzian collected from a
temporary outcrop in the Port of Antwerp area (Belgium). The subspecies is
common in Pliocene North Sea basin deposits, but its lineage dates back to
the late Oligocene and has therefore great potential as a high-resolution
archive. A detailed assessment of the preservation of the shell material by
micro-X-ray fluorescence, X-ray diffraction, and electron backscatter
diffraction reveals that it is pristine and not affected by diagenetic
processes. Oxygen isotope analysis and microscopy indicate that the species
had a longevity of up to a decade or more and, importantly, that it grew
fast and large enough so that seasonally resolved records across multiple
years were obtainable from it. Clumped isotope analysis revealed a mean
annual temperature of 13.5 ± 3.8 ∘C. The subspecies likely
experienced slower growth during winter and thus may not have recorded
temperatures year-round. This reconstructed mean annual temperature is
3.5 ∘C warmer than the pre-industrial North Sea and in line with
proxy and modelling data for this stratigraphic interval, further
solidifying A. benedeni benedeni's use as a climate recorder. Our exploratory study thus reveals
that Angulus benedeni benedeni fossils are indeed excellent climate archives, holding the potential
to provide insight into the seasonality of several major climate events of
the past ∼ 25 million years in northwestern Europe.
TL;DR: In this article , three Appalachian populations were sampled: two native populations (Rockcastle River, KY and New River, VA) and one population founded from the Great Lakes strain (Tygart Lake, WV).
Abstract: Walleye Sander vitreus have been stocked throughout the Appalachian region to augment or restore populations of this economically and ecologically important species. Prior to the genetic identification of a native Eastern Highlands strain, Walleye from the Great Lakes were often used to supplement populations and create new populations. To assess the effect of stocking of Great Lakes-strain Walleye, three Appalachian populations were sampled: two native populations (Rockcastle River, KY and New River, VA) and one population founded from the Great Lakes strain (Tygart Lake, WV). Walleye from Lake Erie were used as a reference for the Great Lakes strain. Utilization of a genotype-by-sequencing approach supported genome-wide estimates of genetic diversity, population structure, and creation of two SNP assays that can be used to rapidly identify Great Lakes strain, native Eastern Highland strain, and F1 hybrid Walleye. Results indicate that the four populations we evaluated were genetically distinct from one another and that each population contains varying degrees of genetic differentiation relative to its source population. The stocked Tygart Lake population displayed lower genetic diversity in metrics such as nucleotide diversity (0.172 vs. 0.184), private alleles (4057 vs. 7623), and observed heterozygosity (0.163 vs. 0.204), likely indicative of genetic drift stemming from a founder effect. The two native populations displayed varying levels of genetic diversity. The New River population was found to have a higher ancestry of the Great Lakes strain in their genome than the Rockcastle River population, reflecting the known admixture of New River Walleye following historic stocking of Great Lakes-derived Walleye. Our results provide molecular tools and show the need for further sampling across the region to identify Great Lakes strain ancestry in local populations and to identify pure native Eastern Highland populations that can be used for future augmentation and restoration of native Walleye.