This dissertation focuses on understanding the evolutionary and diversification dynamics of Sabal, a lineage of neotropical palms. In my first chapter, I use molecular dating and ancestral range reconstruction to investigate the historical biogeography of Sabal. I also collected floral volatile (scent) data from select species and analyze those data to investigate the role that species interactions, specifically pollination, may have played in shaping modern species distributions of Sabal. Molecular dating suggests a divergence event ~14 million years ago that split the most recent common ancestor (MRCA) of temperate southeastern United States Sabal species from a population that would become a clade of tropical Mexican distributed species. This divergence event further coincides with regional cooling characteristic of the Mid-Miocene Climatic Optimum. Floral scent data indicates a lack of interspecific volatile diversity suggesting generalist rather than specialist pollination. Clustering analysis of the scent profiles indicates some phylogenetic signal consistent with the molecular data (particularly the clustering of S. miamiensis, S. palmetto, S. etonia) as well as some environmental signal that divides the temperate southeastern United States species of Sabal (S. minor, S. x brazoriensis, S. miamiensis, S. palmetto, S. etonia) from the tropical species (S. mauritiiformis, S. causiarum, S. mexicana); the latter adds some reinforcement to the molecular dating work and suggests an important role for climatic cooling in shaping modern species distributions in Sabal. My second chapter is a phylogeographic investigation of S. minor, a species which is polymorphic in the growth form of its stem. I used genome-wide single nucleotide polymorphism (SNP) data from individuals of Sabal minor collected from across its native distribution to characterize extant genetic diversity within and between populations, and to elucidate any evolutionary processes underpinning the geographic patterning of the stem growth form along the North American Coastal Plain. The SNP data strongly indicate that S. minor is indeed a single widespread species (i.e. genetic clustering does not correspond to stem type), and that populations polymorphic for stem growth form are restricted in distribution to central Texas and Louisiana. Analyses show genetic clustering of individuals into 4-5 geographically distinct populations that are united by historical gene flow (or incomplete lineage sorting) but show patterning of historical isolation along regional geographic barriers. The results of this chapter also reveal that populations of S. minor collected from northeastern Mexico are actually best recognized as a separate species. I describe this new species of Sabal as S. tamaulipensis in my third chapter. In the last chapter of my dissertation, I investigate species relationships among all 19 described species of Sabal and test species monophyly for widespread and taxonomically challenging species. Using target capture sequencing data, I leveraged 969 putatively single copy nuclear genes to reconstruct the phylogenetic history of Sabal. I found that species grouped into clades corresponding broadly with three geographic regions: Mexico, southeastern United States, and the Caribbean. I then reconstruct the evolutionary history of habit and inflorescence posture and orders of branching across Sabal. I found that bearing an arcuate inflorescence with three orders of branching is ancestral in Sabal, with convergent reductions of inflorescence branching in 75% of the acaulescent species (S. minor, S. tamaulipensis, and S. etonia) possibly indicating a physiological constraint to branching associated with acaulescence. Reconstructing the evolution of habit, in this case stature or stem growth form, suggests caulescence is ancestral and acaulescence evolved at least twice in Sabal.