Pinpointing genetic breaks in the southeastern Pacific: Phylogeography and genetic structure of a commercially important tunicate

Abstract

Aim Accurate characterization of evolutionary units (species or populations) underlies all ecological and evolutionary studies and is crucial to conservation planning. Seascapes have long been thought to be highly permeable to gene flow, yet over the last decade building evidence has shown that barriers to gene flow in marine environments are much more common than previously thought. Here, we precisely characterize two barriers to gene flow in the tunicate Pyura chilensis across 26° of latitude in the southeastern Pacific, assess their magnitude and explore their congruence with current biogeographical patterns of this region. Location The southeastern Pacific (SEP), from Ilo, Perú (17°S) to Chiloé, Chile (43°S). Taxon Pyura chilensis. Methods We used a combination of highly polymorphic microsatellite markers and a 540 bp fragment of the Cytochrome Oxidase subunit I (COI) to compare individuals sampled at 26 localities spanning approximately 2500 km of the SEP. Genetic diversity was analysed using Bayesian clustering, haplotype networks, Isolation by Distance and cline models. A Coalescent simulator was used to estimate migration rates. Results The results from both the microsatellite and COI markers indicate the presence of two genetic discontinuities: one at 34°S and one at 39°S which coincide with genetic breaks reported for other species. Interestingly, we were able to determine that genetic transitions occur abruptly and within short geographical distances (~30 km) compared with previous studies of this tunicate. Coalescent simulations indicate the 34°S break is less permeable than the 39°S break, and gene flow appears to be mostly from north to south. Main conclusions Our results support other studies that show that seascapes are complex, and also highlight the importance of accurately sampling distribution ranges when making conclusions about gene flow. Overall, the two main biogeographical barriers to gene flow characterized in the southeastern Pacific are not homogeneously permeable and can be narrow (<30 km). These results are relevant for the management of fisheries in this region and specifically for this commercially important species.

Population genomic analyses reveal hybridization and marked differences in genetic structure of Scurria limpet sister species with parapatric distributions across the South Eastern Pacific

“…zebrina , the genetic break occurs between 31 and 34°S and close to the biogeographic break around 35°S previously reported for benthic macroinvertebrates (Lancellotti & Vásquez, 1999) and that appears to be associated with major Andean river outflows (Lara et al, 2019). A phylogeographic break at 35°S has been reported in the ascidian Pyura chilensis (Quesada‐Calderón et al, 2021) and in the beach‐dwelling isopod Excirolana hirsuticauda (Haye et al, 2019). The latter species, E .…”

Comparative population genetics of congeneric limpets across a biogeographic transition zone reveals common patterns of genetic structure and demographic history

“…The shared break occurs further south in the IA for S. scurra and S. araucana , between 31 and 34° S (HU and PU sites, Figure 2c). This second shared break is also common to Scurria zebrina and other invertebrates, such as the gastropod Acanthina monodon , the tunicate Pyura chilensis , the beach‐dwelling brooder Excirolana hirsuticauda and the barnacle Notochthamalus scabrosus (Barahona et al, 2019; Haye et al, 2019; Quesada‐Calderón et al, 2021; Saenz‐Agudelo et al, 2022; Sánchez et al, 2011). A previous study also estimated a genetic break around 30° S for S. scurra , but it did not have the spatial resolution to separate it from the break at 31–34° S (Haye et al, 2014).…”

Impact of persistent barrier to gene flow and catastrophic events on red algae evolutionary history along the Chilean coast

“…Along the coast located in between the two main biogeographic breaks, genetic breaks have been observed in some species. However, both the divergence time and the position of the genetic breaks seem to be more species specific (Montecinos et al, 2012;Haye et al, 2014;Guillemin et al, 2016;Morales-González et al, 2019;Quesada-Calderón et al, 2021). The coastline located between 36 °S and 42 °S has been regularly affected by earthquakes and coastal uplift that generated large but local mortality of intertidal organisms (Castilla, 1988;Castilla et al, 2010;Jaramillo et al, 2012;Hernández-Miranda et al, 2014;Brante et al, 2019).…”