From rivers to ocean basins: The role of ocean barriers and philopatry in the genetic structuring of a cosmopolitan coastal predator

Abstract

Understanding the population structure of a species and the barriers that disrupt dispersal is important to accurately assess the global conservation status and manage the risk of local extinction. This is especially true for species of commercial importance (Begg et al., 1999) or conservation concern (Moritz, 1994), which are impacted disproportionally by anthropogenic or environmental pressures. Dispersal

Ontogenetic shifts in body form in the bull shark Carcharhinus leucas

“…When sorted by sex, negative caudal allometry is only recovered in females (Figure 4; Table 4), with males exhibiting isometric growth (Figure 3; Table 3). Male bull sharks are typically thought to have greater dispersal potential than females (Devloo‐Delva et al, 2023), and thus, this result would appear to contradict the allometric niche shift hypothesis, as the sex exhibiting greater long‐distance movements exhibits isometry (Gayford, Whitehead, et al, 2023). We might expect male bull sharks, with greater dispersal potential, to exhibit greater allometry as they will rely more upon the lift generated by a less‐heterocercal tail for efficient long‐distance locomotion.…”

“…It is possible that these differences are adaptive and result from ecological differences between these geographically and genetically isolated C. leucas populations. Indeed, these populations are reproductively isolated from one another (Devloo‐Delva et al, 2023). Due to the bathymetry surrounding Reunion bull sharks here likely inhabit a more pelagic‐like environment compared with the shallow shelf environments in which bull sharks are found in the Western Atlantic.…”

“…It is possible that these differences are adaptive and result from ecological differences between these geographically and genetically isolated C. leucas populations. Indeed, these populations are reproductively isolated from one another (Devloo-Delva et al, 2023).…”

“…The well-documented use of nursery areas by juveniles (as opposed to speculation as with other species) should allow for more robust ecomorphological inferences regarding functional/selective explanations for scaling coefficients observed over individual life stages (Froeschke et al, 2010;Heupel & Simpfendorfer, 2011). Moreover, there are known sexual differences in spatial ecology and habitat, with females exhibiting philopatry and reduced dispersal compared to males (Devloo-Delva et al, 2023). For this reason, we expect to detect sexual dimorphism in scaling coefficients, as recovered in recent studies of other shark species (Gayford, Godfrey, et al, 2023).…”

Photographic evidence from a recreational angler of the northernmost record of the bull shark Carcharhinus leucas (Elasmobranchii: Carcharhinidae) in the western Pacific Ocean

“…occasional visitor or resident) at known distribution limit for the avoidance of shark-bite incidents in temperate latitude under ongoing climate change. In addition, a recent molecular approach has also revealed that this species has a local population; the population of the Ryukyu Islands, including Iriomote Island, is genetically distinct (Devloo-Delva et al ., 2023). Bull sharks occurring in the temperate latitudes of Japan need to be genetically examined to reveal population matching from the viewpoint of future conservation in the western Pacific regions.…”