Genetic diversity of Halodule wrightii is resistant to large scale dieback: a case study from the Indian River Lagoon

Abstract

There is a reciprocal relationship between disturbance and diversity such that disturbance can result in changes to diversity that in turn impact a population’s response to disturbance. Seagrasses are systems that are experiencing increasing disturbances and loss, and it is therefore important to understand this diversity–disturbance relationship. In this study, we observe changes in diversity and population differentiation of shoal grass (Halodule wrightii) during a large scale dieoff in the Indian River Lagoon, Florida USA. While allelic richness and heterozygosity were relatively high and do not change over time, population differentiation increased (estimated using FST), indicating genetic drift. This maintenance of diversity is important since seagrasses with high genetic diversity have been shown to withstand several environmental disturbances (grazing, low light, and high temperature) better than meadows with low diversity. This small increase in differentiation was only detectable because of replicate collection over time, which is rare in the literature and in monitoring programs. However, it is important since it indicates potential dispersal limitation which could hinder large scale recovery. We recommend plant nurseries as management tools in this system to preserve existing diversity and to aid in large scale restoration.