Zooming in and out on population connectivity picture: Describing genetic patterns at 100 m and 136 km in a broad-cast spawner and its application for the assessment of marine managed areas

Humanity’s prosperity currently relies on sustainably exploiting natural resources. In marine environments, marine managed areas (MMA) are an effective and efficient conservation strategy, especially when they are based on ecological processes and balancing between biological goals and socio-economic constraints. Including connectivity data in the design and assessment of MMA networks has proven crucial for reaching conservation and socio-economic goals, but it is infrequently used in network design. It is imperative to develop pragmatic methods for determining population connectivity dynamics and posteriorly incorporating the information in the design and assessment of MMA. In this dissertation, we estimated the genetic connectivity patterns of an ecologically, culturally, and economically important shellfish species, Cellana exarata, endemic to the Hawaiian archipelago. The study was focused within Maui, estimating genetic connectivity at a fine (~6.5km, ~25 km) and small (whole island) spatial scales. The sampling design included two sampling years (2014, 2017), adults and juveniles, three classes of management (open areas, government enforced no take areas, and community managed voluntary no take Rest Areas). The connectivity patterns were inferred from analyses of genetic structure, relatedness, and assignment tests using >1000 single-nucleotide polymorphisms. There was high connectivity at fine spatial scales within 6.5-25 km of coastline, a low level of chaotic genetic patchiness, and an impact of Rest Areas on increased levels of relatedness after 2.5 years within and up to 100m from their boundaries. Spatio-temporal variation in the connectivity patterns were likely driven by ecological and oceanographic stochasticity as well as management activities. On the island scale, there was significant, but slight, genetic structure between North and South shore samples with differences in the probability of assignment to one of two genetic clusters. Assignments of juveniles back to adult samples indicated net dispersal from the South to the North shore of Maui, with North-South mixing along the East tip of the island. Deeper analysis of genetic identity revealed that the genetic clusters exhibited substantial reproductive isolation (FST = 0.03-0.10) and 93.5% of individuals were either pure or F1 hybrids, indicative of two diverging, locally adapted populations. Further, the locations of MMA result in a bias towards the protection of one of the genetic clusters (South region cluster), highlighting the importance of establishing managed areas on North shores to protect the genetic diversity of C. exarata and promote higher sustainable yields.