Abstract Detail

Molecular Ecology

Cang, Alice [1], Welles, Shana [2], Dlugosch, Katrina [3].

Causes and consequences of genome size variation in an invasive plant, Centaurea solstitialis.

The evolutionary drivers responsible for the extraordinary genome size variation across angiosperms are still largely unknown and biological invasions may present unique opportunities to clarify the population-level processes that shape this variation. Shifts towards smaller genome sizes have occurred in association with successful colonization events in other plants, suggesting phenotypic consequences of genome size variation, possibly due to cell size effects. If genome size imposes functional constraints, a potential invader may benefit from reduced genome sizes that promote ecological traits of the “ideal weed”, such as faster early growth and rapid development. However, variation in genome size may also result from selection along environmental gradients regardless of where populations are in the range. Conversely, founder effects and drift in small populations may have allowed neutral or detrimental increases in genome size in recently established populations at the leading edge of expansion. Centaurea solstitialis (Asteraceae) is an invasive thistle in North America, and previous work in this system has demonstrated rapid phenotypic evolution since introduction. We investigated the causes and consequences of intraspecific genome size variation in C. solstitialis across an invasion in California to ask: (1) Is trait variation associated with genome size variation? (2) Does selection for faster growth and reproduction at the leading edge of the expansion select for smaller genomes, or do founder effects and drift in recently founded populations allow genome sizes to increase? (3) Does selection on growth and reproduction along environmental clines select for variation in genome size? We conducted a common garden and estimated genome size by flow cytometry for 333 plants across 14 populations. We found larger genomes were significantly associated with slower vegetative growth and later flowering times, with lower lifetime biomass and flower production. We also observed a negative relationship with elevation, suggesting support for a hypothesis of selection for earlier flowering time, potentially due to shorter growing seasons at higher elevations. Despite these potential ecological consequences, we found no evidence of selection for smaller genomes during range expansion. Instead, we saw a significant, negative relationship with population age, consistent with the prediction that small founding populations allowed neutral or detrimental increases in genome size to rise to high frequency. This is one of the first demonstrations that small population sizes during range expansion might impact genome architecture. Future work concerns identifying the molecular mechanisms that underlie patterns of genome size variation, such as differences in transposable element content.

1 - University of Arizona, Department of Ecology and Evolutionary Biology, P.O. Box 210088, Tucson, AZ, 85721, USA
2 - Chapman University, SCST, One University Dr, Orange, CA, 92866, United States
3 - University Of Arizona, ECOL AND EVOL BIOLOGY, P.O. Box 210088, Tucson, AZ, 85721, United States

Keywords:
Genome size
Invasive species
Evolutionary Ecology
flow cytometry.

Presentation Type: Oral Paper
Session: MOL1, Molecular Ecology
Location: San Pedro 2/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 1:30 PM
Number: MOL1001
Abstract ID:1045
Candidate for Awards:None