Abstract
Evaluating species diversity and patterns of population genetic variation is an essential aspect of conservation biology to determine appropriate management strategies and preserve the biodiversity of native plants. Habitat fragmentation and potential habitat loss are often an outcome of a reduction in naturally occurring wildfires and controlled prescribed burning, as seen in Helianthus verticillatus (whorled sunflower). This endangered, wild relative of the common sunflower, Helianthus annuus, is endemic to four locations in Alabama, Georgia, and Tennessee, United States. Despite its endangered status, there is no recovery plan for H. verticillatus, and knowledge related to its basic plant biology and importance in ecosystem services is mostly unknown. In this study, we utilized 14 microsatellite loci to investigate fine-scale population structure and genetic diversity of H. verticillatus individuals found on two sampling sites within the Georgia population. Our results indicated moderate genetic diversity and the presence of two distinct genetic clusters. Analyses of molecular variance indicated that the majority of variance was individually based, thus confirming high genetic differentiation and limited gene flow between H. verticillatus collection sites. The evidence of a population bottleneck in these sites suggests a recent reduction in population size that could be explained by habitat loss and population fragmentation. Also, high levels of linkage disequilibrium were detected, putatively suggesting clonal reproduction among these individuals. Our study provides a better understanding of fine-scale genetic diversity and spatial distribution of H. verticillatus populations in Georgia. Our results can underpin an original recovery plan for H. verticillatus that could be utilized for the conservation of this endangered species and to promote its persistence in the wild.
Highlights
We focused on fine-scale population structure and genetic diversity of H. verticillatus growing on privately owned land
H. verticillatus individuals were divided into 14 different collection zones based on location and quadrant in which samples were gathered (C1–5 corresponded to the first collection site where five different quadrants were sampled; R1–9 corresponded to site two and the nine different rows from the sampling grid)
Our results indicated moderate genetic diversity, high levels of clonality, the presence of spatial structure, and evidence of recent bottleneck among H. verticillatus individuals, supporting our hypothesis of clonality and population structure
Summary
Helianthus verticillatus (Small), commonly known as the whorled sunflower, is a herbaceous perennial endemic to four locations in the southeast United States (Matthews et al, 2002; Chafin and Owers, 2010). Tennessee, United States (Seiler and Gulya, 2004), the plant was initially labeled as Helianthus schweinitzii, and later annotated as H. verticillatus by Small (1898) (Matthews et al, 2002). The vigorous growth and showy yellow flowers of H. verticillatus may render the species a potential valuable ornamental plant and presumably a useful pollinizer in the wild as well as in the home garden, which is common for other Helianthus spp. (Schmidt et al, 1995; Chafin and Owers, 2010)
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