Evidence of Interspecific Hybridization or Incomplete Lineage Sorting in River Cane (Arundinaria gigantea)

River cane (Arundinaria gigantea) is an ecologically valuable species of temperate woody bamboo endemic only to the southeastern United States. This species typically grows in dense, monotypic stands along river banks, and clonal growth within stands is expected to be high. Since European settlement of North America, River cane has seen significant population decline, and there is currently growing interest in restoration of River cane populations in their natural range. In order to better inform both field collection and restoration efforts, it is important to understand the genotypic and clonal make up of existing stands. In this study, three natural populations of River cane were investigated for genotypic diversity. Thirty-five SSR loci from other bamboo species were applied in River cane and six were found to produce informative alleles. Genotypes from SSR data allowed the discernment of 15 multilocus genotypes. Each stand contained a dominant multilocus genotype, and two geographically distinct populations shared identical multilocus genotypes. Additionally, three plastid loci were sequenced in a subset of individuals to gain more genotypic resolution. The plastid sequencing yielded four distinct haplotypes. Similarly, each stand contained a dominant haplotype and two populations shared a haplotype. Interestingly, comparing these multilocus genotypes and plastid haplotypes to known samples of River cane and the closely related Switch cane (Arundinaria tecta) showed that one population phylogenetically clustered between the two species. Sequence analysis of the plastid regions showed that this population shared some, but not all, SNPs and indels with Switch cane. These results suggest either incomplete lineage sorting of plastid diversity or interspecific hybridization with biparental chloroplast inheritance.