Weak connectivity and population cohesiveness in rudderfish Kyphosus sandwicensis (Teleostei: Kyphosidae) inhabiting remote oceanic islands

Abstract

1. Population connectivity has a fundamental role in metapopulation dynamics, with important implications in conservation. Easter Island (EI) and Salas y Gómez Island (SG) in the Pacific Ocean are ideal for the study of population connectivity because they are separated by 415 km and isolated from other islands in the Pacific Ocean by >2,000 km. 2. Considering that dispersal processes could play a critical role in the persistence of its populations, the connectivity pattern of the rudderfish Kyphosus sandwicensis was evaluated between EI and SG using both a population genetics and a biophysical modelling approach. 3. The variability in the control region of the mitochondrial DNA did not show a significant phylogeographical pattern, and the variability in 16 microsatellite loci suggested that individuals of K. sandwicensis located at EI and SG belong to the same genetic population. However, historical migration showed that 0.2% of the recruits at EI come from SG and that 0.15% at SG come from EI per year. 4. Using simulated larval release during September and a larval development of 30 days in the plankton, biophysical modelling did not detect migration between the islands. Furthermore, self-recruitment shows interannual variation ranging from 5 to 10% of the total released larvae. 5. Whereas the genetic data showed a lack of population genetic structure but low connectivity of K. sandwicensis between EI and SG, the biophysical modelling showed null movement of particles between the islands. Stochastic movement of larvae or adults could explain the pattern observed, with rafting as an example. These low-frequency and stochastic movements may be important in maintaining the cohesiveness between EI and SG.

Integrating genetic and biophysical approaches to estimate connectivity in an isolated, insular system: case of the culturally important marine gastropod Monetaria caputdraconis

“…This mechanism has also been suggested for other gastropod species that do not have free-swimming larvae but present populations with large geographic extensions (González-Wevar et al, 2018). It is possible that the rafting is involved in the movement of the juvenile or adult M. caputdraconis, as suggested by Valencia et al (2021) for the fish K. sandwicensis between the same islands. Additionally, Rech et al (2020) found that molluscs are frequently rafting taxa in anthropogenic debris in this area.…”

“…It is possible that the rafting is involved in the movement of the juvenile or adult M. caputdraconis , as suggested by Valencia et al . (2021) for the fish K. sandwicensis between the same islands. Additionally, Rech et al .…”

“…This species presents a larva that exceeds 10 months of planktonic life, which could explain the connectivity detected. On the other hand, for the rudderfish Kyphosus sandwicensis which has a larval stage of 1 month, it was not possible to detect particles migrating between both islands, but a historical migration rate of 0.15% from EI to SG and 0.2% from SG to EI was found (Valencia et al ., 2021). The authors suggested that stochastic processes such as rafting could be involved in the connectivity of K. sandwicensis between these islands.…”

Borderless conservation: Integrating connectivity into high seas conservation efforts for the Salas y Gómez and Nazca ridges

“…Recent studies have examined the connectivity of two reefassociated species, the Easter Island spiny lobster Panulirus pascuensis Reed, 1954 and the Easter island rudderfish Kyphosus sandwicensis (Sauvage, 1880), on the western end of the Salas y Goḿez Ridge using variability of microsatellite loci (Meerhoff et al, 2018;Valencia et al, 2021). These studies found weak connectivity amongst marine fauna populations located on Rapa Nui and Salas y Goḿez Island (415 km away), findings that are consistent with other studies that indicate weak connectivity within the ridges for many reef taxa (ComitéOceanografco Nacional de Chile, 2017;Friedlander et al, 2021).…”

Combined biophysical and genetic modelling approaches reveal new insights into population connectivity of New Zealand green-lipped mussels

“…To investigate potential pathways for larval transport and to test hypotheses about patterns of genetic structure, biophysical Lagrangian particle tracking experiments coupled with hydrodynamic models for a region of interest are increasingly employed (Swearer et al, 2019), and their results can be compared to analyses of connectivity reported by population genetic data (reviewed by Jahnke and Jonsson, 2022). Several studies have reported correlations between modelled particle transport rates and measures of genetic distance (such as FST) (e.g., Coleman et al, 2011;Coleman et al, 2013;Munguia-Vega et al, 2014;Jahnke et al, 2018), while others have found no such relationship (e.g., Lourenco et al, 2017;Sefbom et al, 2018;Valencia et al, 2021). Detailed explanations for why these relationships exist in certain species and/or regions and not others are not yet well developed, and further information about how best to interpret these two types of data together would be a valuable contribution to this novel multidisciplinary field.…”