OCE-PRF- Deleterious mutational load in climate driven marine range expansions

Northeastern University, Boston MA

Investigators

Abstract

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Species range expansions are occurring across the globe at unprecedented rates as global warming continues to accelerate, and even more so in marine species. In general, range expansions occur by a series of colonization events in waves of a few dispersed individuals at a time. This leads to the establishment of a new population that originates from few individuals, resulting in a small non-random representation of the genetic variation from the original population – a process known as founder effect. As a result of founder effects, a deleterious mutation that arises at the range edge disperses to a newly expanded habitat and can rapidly increase in frequency within the new population (i.e., expansion load), leading to a loss in fitness. This process is enhanced during range expansion due to the small population sizes and low genetic variation present to select against the new mutation. Fishing triggers similar evolutionary dynamics of population declines and lower genetic diversity, similarly increasing expansion loads. Marine species experience faster range expansions than terrestrial species due to their high dispersal ability and are heavily impacted by fishing pressure, yet, the interaction of both these processes have yet to be elucidated in a marine species. Quantifying the load of deleterious mutations is critical for conservation and management, because they can limit a population’s adaptability and survival. With climate change expected to continue, more species will experience range-shifts at unprecedented rates, making it imperative to document current genetic diversity and understand the genetic basis of populations at the forefront of their expanded range. This project will fund the early career development of an NSF Ocean Sciences Postdoctoral Fellow and will support the research, training, mentorship, and professional development of the fellow. To enhance the broader impacts and utility of this work, the fellow will disseminate results to the scientific community, the local fishing community and fishery management officials (e.g., NOAA, Manomet, Atlantic States Marine Fisheries Commission). Additionally, this project will increase participation of traditionally underrepresented groups in science through: (1) undergraduate student mentorship, (2) outreach seminars for students in local community colleges, and (3) outreach with the local community. The rapid accumulation of genetic mutations – and in particular deleterious mutations in edge populations – remains largely understudied during range expansions. This study presents a unique opportunity to test the evolutionary theory of the accumulation of deleterious mutations in a rapid climate-driven range expansion and harvested marine fish, Black Sea Bass (Centropristis striata). Using a combination of genome-wide data, fitness tests, and quantitative modeling approaches, the following hypotheses will be tested: H1- (Higher load at range edge) C. striata will show a greater expansion load in coding regions at the range expansion front compared to the historical range center and edge populations; H2- (Decreased fitness at range edge) range expanding populations with a greater expansion load will show evidence of decreased fitness-related traits; H3- (Load exacerbated by fishing) overfishing will exacerbate the accumulation of deleterious mutational load in expanding populations. If results support the hypotheses (i.e., higher loads and decreased fitness are found at the expanding-front), as predicted by theory, they will have widespread implications for marine conservation strategies in a rapidly changing climate. However, if these hypotheses are rejected, the data will challenge existing scientific assumptions, suggesting marine systems undergo different processes. This integrative dataset will advance understanding of climate-driven range expansions and the interactive effects of climate change and fishing pressure on marine species, such as Black Sea Bass. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.