UC Merced

Analyzing the relationship between evolutionary forces in a dynamic environment has been a challenge for marine population genetics. We explored this issue using a reference genome and population genomic analyses of the California ribbed mussel, Mytilus californianus—an ecosystem engineer that inhabits an intertidal zone shaped by marine and terrestrial weather and climate. Seventeen samples were collected at the upper and lower limits of intertidal environments from five sites across California. A chromosome-scale reference genome was assembled, and population genomic analyses were conducted to investigate genetic differentiation across latitudinal and intertidal gradients. The reference genome is 1.65 Gb long, with N50 sequence length of 118 Mb, and 86% complete. Low population differentiation aligned with previous studies, indicating very high migration (FST ≤ 0.0003). Nonetheless, allele frequencies at a small number (48–103) of outlier loci are differentiated alongside the many environmental factors that change across latitudinal and intertidal gradients.