Low population genetic structure is consistent with high habitat connectivity in a commercially important fish species (Lutjanus jocu)

Abstract

The level of habitat availability influences genetic divergence among populations and the genetic diversity within populations. In the marine environment, near-shore species are among the most sensitive to habitat changes. Knowledge of how historical environmental change affected habitat availability and genetic variation can be applied to the development of proactive management strategies of exploited species. Here, we modeled the contemporary and historical distribution of Lutjanus jocu in Brazil. We describe patterns of genomic diversity to better understand how climatic cycles might correlate with the species demographic history and current genetic structure. We show that during the Last Glacial Maximum, there were ecological barriers that are absent today, possibly dividing the range of the species into three geographically separated areas of suitable habitat. Consistent with a historical reduction in habitat area, our analysis of demographic changes shows that L. jocu experienced a severe bottleneck followed by a population size expansion. We also found an absence of genetic structure and similar levels of genetic diversity throughout the sampled range of the species. Collectively, our results suggest that habitat availability changes have not obviously influenced contemporary levels of genetic divergence between populations. However, our demographic analyses suggest that the high sensitivity of this species to environmental change should be taken into consideration for management strategies. Furthermore, the general low levels of genetic structure and inference of high gene flow suggest that L. jocu likely constitutes a single stock in Brazilian waters and, therefore, requires coordinated legislation and management across its distribution.

Integration of genomic and ecological methods inform management of an undescribed, yet highly exploited, sardine species

“…In accordance with our ENM showing continuous suitability along the 3700 km of the coastal range sampled here, we find low genetic differentiation between coastal localities ( F ST < 0.04; electronic supplementary material, table S4) and significant isolation by distance (figure 4 a ). These levels of genetic differentiation are similar to values found in other pelagic species with large dispersal capacity, such as the dog snapper ( F ST = 0.037) [75]. Thus, our results suggest that continuous habitat allows gene flow along the coastal range, but limited dispersal rate of this species also resulted in clinal divergence along the coast.…”

“…Some co-distributed coastal species likely originally from the Brazilian coast that colonized FNO also show this genetic divergence, as in the case of corals [71], lobster [72] and the reef-associated rockpool blenny [73]. However, other species that colonized FNO do not show this pattern of divergence, such as parrotfishes [74], octopuses [70] and snappers [75], indicating that species occurring in similar habitats can have different evolutionary responses to the same oceanographic barriers. Future studies can clarify if such idiosyncratic patterns of genetic divergence are related to dispersal traits, such as the duration of larval stage, type of reproduction and body size.…”

Too young to die: Mapping nursery areas for early juveniles of the endangered sandbar shark (Carcharhinus plumbeus) to inform conservation in the Mediterranean Sea

“…Given that the occurrence of this species is represented in the dataset by a relatively small number of observations and that these are not randomly distributed across environmental variables, we estimated favourability instead of suitability using the probability of occurrence. Environmental favourability reflects the variation of the occurrence probability and is less affected by the presence/absence ratio (Tovar Verba et al, 2023). It can vary between 0 (location unsuited for the species) and 1 (an ideal location for the occurrence of the species).…”