MCA: Deciphering an Invasion: Understanding how invasive traits shape genomic structure and adaptive potential during rapid population growth and range expansion

Grand Valley State University, Allendale MI

Investigators

Abstract

A population’s ability to adapt to new or changing environmental conditions can be an important factor impacting species success. Adaptation is frequently associated with high levels of genetic variation, and when populations with limited genetic variation experience new or changing environments, it may be difficult to respond to these conditions. Nevertheless, many species not only survive, but thrive after a small group of individuals are introduced to new habitats. This can be the case for invasive species; one of the primary threats to biodiversity due to their impacts on native biota and their ability to alter ecosystems. Invasive species provide an optimal system to study evolutionary processes since they are ‘real-life’ experiments allowing researchers to assess mechanisms shaping how species respond to environmental change. Hemlock woolly adelgid (Adelges tsugae) is one of the top invasive threats to forest ecosystems in eastern North America. Hemlock woolly adelgid populations in eastern North America are invasive and display rapid population growth and range expansion, while western North American populations are native, and population growth is limited by natural predation. This research project compares eastern and western hemlock woolly adelgid populations to explore how invasive traits, such as rapid range expansion and population growth, influence genomic structure and adaptive potential as invasive populations expand their distribution range. The data collected will improve hemlock woolly adelgid management by identifying dispersal patterns and improving future range expansion models. This project will also result in the development of advanced genomic-based courses for undergraduates. The specific goals of this project are to (i) assess the population structure of invasive and native HWA populations in North America, (ii) evaluate how population demographics influence genetic diversity and genetic load, and (iii) understand the molecular processes contributing to increased cold tolerance of some northern invasive populations. For the first goal, the researchers will collect individuals from across the western and eastern North American distribution ranges and use low coverage whole genome sequencing (lcWGS) to evaluate genetic diversity and population structure. For the second goal, the researchers will use the genomic data to evaluate how range distribution patterns and differences in selection processes impact the accumulation of deleterious mutations throughout invasive populations. For the third goal, individuals will be collected across different climate regions where populations differ in their cold tolerance. The researchers will evaluate differences in cold-induced mortality among populations and use RNA-sequencing to identify differentially expressed genes associated with variation in cold tolerance. The combined datasets will evaluate how population dynamics impacts novel mutation accumulation, genetic load, and adaptive responses to new selection pressures. Overall, this project will increase our understanding of the genomic mechanisms influencing the rapid success of invasive species to novel ecosystems. 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.