A perfect storm: ploidy and preadaptation facilitate Saccharum spontaneum escape and invasion in the Republic of Panama
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ORIGINAL PAPER
A perfect storm: ploidy and preadaptation facilitate Saccharum spontaneum escape and invasion in the Republic of Panama Kristin Saltonstall
. Graham D. Bonnett
. Karen S. Aitken
Received: 18 February 2020 / Accepted: 6 November 2020 The Author(s) 2020
Abstract Polyploidy may contribute to invasive ability as it can lead to high survival and fitness during establishment and enhance the processes of adaptation to novel environments by increasing genetic diversity in invading propagules. Many grasses are polyploid and many are aggressive invaders, making them persistent problems in disturbed environments worldwide. Today, vast areas of central Panama are dominated by Saccharum spontaneum, a perennial grass that originates from Asia. While widely regarded as invasive, it is not known when or how it arrived in Panama. We explore hypotheses regarding the timing and origins of this invasion through literature review and comparisons of genetic diversity in Panama with accessions from available sugarcane germplasm collections, highlighting historical accessions that were likely brought to Panama in 1939 as part of a USDA sugarcane germplasm collection. Samples were haplotyped at
two chloroplast loci and genotyped using eight microsatellite markers. All sequenced individuals from Panama belong to a single chloroplast lineage which is common worldwide and was common in the Historic germplasm collection. Although genotypic diversity was extremely high in all samples due to high ploidy, samples from Panama had reduced diversity and clustered with several accessions in the Historic collection which had the same haplotype and high ploidy levels. Our results suggest that accidental escape from the historical sugarcane germplasm collection is the likely origin of the S. spontaneum invasion in Panama. Intraspecific hybridization among several historical accessions and pre-adaptation to local conditions may have facilitated its rapid spread and persistence. We discuss the implications of our findings for biosecurity of germplasm collections. Keywords Saccharum spontaneum Sugarcane germplasm Polyploidy Phylogeography Microsatellites Biosecurity
Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/ s10530-020-02421-3. K. Saltonstall (&) Smithsonian Tropical Research Institute, Apartado, 0843-03092 Balboa, Ancon, Panama e-mail: [email protected] G. D. Bonnett K. S. Aitken CSIRO Agriculture and Food, QBP, 306 Carmody Road, St Lucia, QLD 4067, Australia
Introduction Grasses have been identified as a particularly invasive plant group and are overly represented in ‘‘invasive alien plant’’ lists globally (D’Antonio et al. 2011; Holm et al. 1977). Invasive grasses are a persistent
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problem in tropical ecosystems worldwide as many have been introduced for forage and as improved pasture grasses and have escaped agricultural settings, now occupying many disturbed habitats
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