AUTHOR=Sapkota Shiwani , Boggess Sarah L. , Trigiano Robert N. , Klingeman William E. , Hadziabdic Denita , Coyle David R. , Nowicki Marcin 

TITLE=Microsatellite Loci Reveal High Genetic Diversity, Mutation, and Migration Rates as Invasion Drivers of Callery Pear (Pyrus calleryana) in the Southeastern United States

JOURNAL=Frontiers in Genetics

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2022.861398

DOI=10.3389/fgene.2022.861398

ISSN=1664-8021

ABSTRACT=Pyrus calleryana Decne. (Callery pear) is a deciduous pear tree native to China, Japan, Korea, and Taiwan. It is a popular ornamental tree in the United States (U.S.) with early spring blooms and vibrant fall color. There are at least 26 cultivars of P. calleryana available of which ‘Bradford’ is the most well-known in the U.S. Open-pollinated P. calleryana escapees are becoming one of the most common invasive tree species across the eastern U.S. Developing better management practices for invasive P. calleryana requires detailed knowledge about reproductive biology and genetic diversity of the species, however, little is currently known about genetic variability within open-pollinated trees. We investigated the genetic diversity and population structure of non-cultivated, escaped P. calleryana populations collected within a ~177 km radius in the southeastern U.S. Because P. calleryana exhibits a range of morphological variation with great evolutionary potential, we hypothesized that a high genetic diversity would be manifested among escaped P. calleryana. Using 15 previously developed microsatellite loci, we genotyped 180 open-pollinated P. calleryana individuals that were collected across six naturally occurring sites in Tennessee, Georgia, and South Carolina, U.S. Our results revealed the presence of a population structure with high genetic diversity, high gene flow, and high genetic differentiation between individuals across collection sites. Our results revealed that P. calleryana populations had differentiated shortly after the introduction to the U.S., most likely from specimens imported from China, consistent with historical records and our prior findings. The high invasive potential of the species is perhaps best underscored by transformation of P. calleryana specimens introduced from China into escape populations at continental scale across the U.S. Our data also provided novel insight into potential issues that could be problematic for the future as P. calleryana may pose a potential threat to the economy, ecology, and native biodiversity in invaded areas.