Chronosequence of invasion reveals minimal losses of population genomic diversity, niche expansion, and trait divergence in the polyploid, leafy spurge

• Published in: bioRxiv
• Main Authors: Lake, Thomas A, Briscoe Runquist, Ryan D, Flagel, Lex E, Moeller, David A
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 06.07.2023
• Subjects: Divergence; Dormancy; Euphorbia virgata; Evolution; Genetic diversity; Genomics; Genotyping; Germination; Introduced species; Invasive species; Niche breadth; Polyploidy; Population structure; Range extension
• DOI: 10.1101/2023.04.04.535556

Rapid evolution may play an important role in the range expansion of invasive species and modify forecasts of invasion, which are the backbone of land management strategies. However, losses of genetic variation associated with colonization bottlenecks may constrain trait and niche divergence at leading range edges, thereby impacting management decisions that anticipate future range expansion. The spatial and temporal scales over which adaptation contributes to invasion dynamics remains unresolved. We leveraged detailed records of the ~130 year invasion history of the invasive polyploid plant, leafy spurge (Euphorbia virgata), across ~500km in Minnesota, U.S.A. We examined the consequences of range expansion for population genomic diversity, niche breadth, and the evolution of germination behavior. Using genotyping-by-sequencing, we found some population structure in the range core, where introduction occurred, but panmixia among all other populations. Range expansion was accompanied by only modest losses in sequence diversity, with small, isolated populations at the leading edge harboring similar levels of diversity to those in the range core. The climatic niche expanded during most of range expansion, and the niche of the range core was largely non-overlapping with the invasion front. Ecological niche models indicated that mean temperature of the warmest quarter was the strongest determinant of habitat suitability and that populations at the leading edge had the lowest habitat suitability. Guided by these findings, we tested for rapid evolution in germination behavior over the time course of range expansion using a common garden experiment and temperature manipulations. Germination behavior diverged from early to late phases of the invasion, with populations from later phases having higher dormancy at lower temperatures. Our results suggest that trait evolution may have contributed to niche expansion during invasion and that distribution models, which inform future management planning, may underestimate invasion potential without accounting for evolution.Competing Interest StatementThe authors have declared no competing interest.Footnotes* We have worked on better framing the Discussion section within the context of the species biology to draw inferences about evolutionary possibilities and applied implications. In the Discussion section, we have included how management practices can be influenced by the maintenance of genetic variation during invasion. We have revised figures and included additional supplementary information to clarify our approaches.