Geographic origin and timing of colonization of the Pacific Coast of North America by the rocky shore gastropodLittorina sitkana

Abstract

The demographic history of a species can have a lasting impact on its contemporary population genetic structure. Northeastern Pacific (NEP) populations of the rocky shore gastropod Littorina sitkana have very little mitochondrial DNA (mtDNA) sequence diversity and show no significant population structure despite lacking dispersive planktonic larvae. A contrasting pattern of high mtDNA diversity in the northwestern Pacific (NWP) suggests that L. sitkana may have recently colonized the NEP from the NWP via stepping-stone colonization through the Aleutian-Commander Archipelago (ACA) following the end of the last glacial 20,000 years ago. Here, we use multi-locus sequence data to test that hypothesis using a combination of descriptive statistics and population divergence modeling aimed at resolving the timing and the geographic origin of NEP populations. Our results show that NEP populations share a common ancestor with a population of L. sitkana on the Kamchatka Peninsula ∼46,900 years ago and that NEP populations diverged from each other ∼21,400 years ago. A more recent population divergence between Kamchatka and NEP populations, than between Kamchatka and other populations in the NWP, suggests that the ACA was the most probable dispersal route. Taking into account the confidence intervals for the estimates, we conservatively estimate that L. sitkana arrived in the NEP between 107,400 and 4,100 years ago, a range of dates that is compatible with post-glacial colonization of the NEP. Unlike other congeners that are relatively abundant in the Pleistocene fossil record of the NEP, only one report of L. sitkana exists from the NEP fossil record. Although broadly consistent with the molecular data, the biogeographic significance of these fossils is difficult to evaluate, as the shells cannot be distinguished from the closely-related congener L. subrotundata.

The impact of marine heatwaves on rocky intertidal communities: evidence of accumulative carryover effects of marine heatwaves

“…In previous studies, thermal niches were estimated by defining northern (i.e., cold-affinity) species and southern (i.e., warmer-water) species using species occurrence reports (Smale et al, 2017;Sanford et al, 2019). Thus, we obtained occurrence reports for each species from Hayashi (1943;1947);Toyokokujigyo Corporation (1980);Pasco Corporation (1988); Korn and Kulikova (1995); Yoshida (1998); Higo et al (1999); Okutani (2000); Selivanova (2002); Kado (2003); Latypov and Kasyanov (2003); Nishi (2003) Marko and Zaslavskaya (2019); Klochkova et al (2020;; Ohira (2020), andIshida et al (2021). Here, we focused on the distribution of each species in four ecoregions along the coastal northwest Pacific within the temperate northern Pacific realm: Kamchatka Shelf and Coast, Oyashio Current, Northeastern Honshu, and Central Kuroshio Current.…”

Phylogeography of sugar kelp: Northern ice‐age refugia in the Gulf of Alaska

“…Unlike terrestrial refugia, the sizes, number, and locations of coastal refugia, and postglacial dispersal pathways were limited by the more or less linear nature of shorelines. Survival in northern marine glacial refugia has been suggested for several intertidal and shallowwater species of algae (Lindstrom et al, 1997) and a variety of invertebrates (Marko et al, 2010;Marko & Zaslavskaya, 2019).…”

Genetic variation of <i>Littorina horikawai</i> endemic to the western coast and the adjacent islands around Kyushu, Japan inferred by mtDNA analyses

“…For phylogeographic and population genetic studies, these Littorina species with low dispersal ability have been treated as a suitable study model system because they tend to accumulate genetic differentiation among populations (e.g., Mäkinen et al 2008, Sotelo et al 2020). In the north Pacific region, previous studies focused on Littorina sitkana Philippi, 1846 which is distributed from Oregon to the Bering Sea and the northern part of Japan and Russia demonstrated that the process of genetic structuring and colonization pattern of it (Azuma et al 2017, Marko & Zaslavskaya 2019.…”