Seed sourcing for ecological restoration in an era of climate change: Impacts of source latitude and hybridization

Abstract

In Minnesota, tallgrass prairie ecosystems currently occupy less than 1% of their former range. The importance of maintaining and restoring this dwindling ecosystem is well recognized but the ecological restoration process is complex, particularly in the current era of climate change. Successful establishment and persistence of restoration populations depends in large part on seed source selection. Previous research and discussion have explored the importance of maintaining local adaptation and genetic diversity. There has also been discussion of intentionally translocating populations in specific directions in response to ongoing climate change. In an effort to inform seed sourcing guidelines, the research presented here investigates (1) the implications for restoration of translocating populations across latitudes, (2) the phenological and fitness outcomes of hybridization between distinct populations, and (3) genetic effects contributing to differences between divergent populations. Chapter 1 focuses on the phenological and fitness impacts of translocation along a latitudinal gradient within the state of Minnesota using a common garden style approach and three perennial prairie species. Chapters 2 and 3 expand upon this work and investigates the impact of translocation on an annual prairie species sampled across a latitudinal span from Minnesota to Missouri, as well as investigating the outcome of hybridization between these divergent populations. Our results highlight the importance of latitude of origin to both phenology and fitness of translocated populations, as plants from more northern locations tended to have earlier timing of flowering and fruiting in the common gardens, as well as higher fitness for all of our study species. In addition, Chapters 2 and 3 demonstrate the potential positive impacts of hybridization across a range of geographic distances with no indication of outbreeding depression, as hybrid generations tended to have higher mean fitness in the common gardens than the parental generations. However, phenological mismatch between seed source and planting site in populations translocated across large latitudinal distances can result in low fitness and limit hybridization with local populations. Taken together, these results highlight the benefits of hybridization between populations, while demonstrating the potential drawbacks of translocating populations across large latitudinal distances.