Preliminary Insights into the Genome of Flowering Dogwood (Cornus florida L.) – Implications for the Study of Local Adaptation in the Eastern North American Hardwood Forest Ecosystem

The hardwood forests of eastern North America represent one of the most diverse temperate forests in the world. Over 120 tree species inhabit this region and have diversified into numerous niches defined by geoclimatic variables and biotic interactions. This diversification has occurred over evolutionary timescales that also included dramatic shifts in historical climate regimes. These forests, therefore, are ideal for the study of the interaction between phylogeographic history, historical climate change, and local adaptation. We have targeted a subset of eight species that largely represents this niche diversity: (1) yellow-poplar (Liriodendron tulipifera L.), (2) black tulepo (Nyssa sylvatica), (3) American beech (Fagus grandifolia), (3) green ash (Fraxinus pennsylvanica), (4) eastern redbud (Cercis canadensis L.), (6) flowering dogwood (Cornus florida), (7) boxelder (Acer negundo), and (8) American hophornbeam (Ostrya virginiana). Using flowering dogwood as a test case, we developed a genotype-by-sequencing (GBS) pipeline for a reference genotype of this species, the first step of which included the creation of a set of reference contigs. These contigs were assembled from Illumina short read data generated on the HiSeq2000 platform using a novel mixture of standard bioinformatics tools and custom scripts. Contigs were subsequently annotated and a GBS approach based on restriction digestion was conducted on 100 samples collected across the natural range of flowering dogwood. Preliminary data are being used to construct null models of the historical phylogeography of this species, with goals of scaling up to a full landscape genomic study of local adaption in the targeted eight species.