Characterizing North American Ipomoea grandifolia (Convolvulaceae), a member of Ipomoea series batatas

<p>Species in the genus <em>Ipomoea </em>are often difficult to identify due to their similar morphologies and their ability to hybridize with one another. An undescribed North American <em>Ipomoea </em>morphotype in series <em>Batatas</em>, referred here as <em>Ipomoea</em> Carolina morphotype, was found to be morphologically, genetically, and reproductively isolated from other locally co-occurring <em>Ipomoea </em>species. A previous phylogenetic analysis that included a broader sampling of species in <em>Ipomoea</em> series <em>Batatas</em> suggested that <em>Ipomoea </em>Carolina morphotype may be <em>Ipomoea grandifolia</em>, a species described as found only in South America<em>.</em> To evaluate these findings, we tested intrinsic cross-compatibility between <em>Ipomoea </em>Carolina morphotype and <em>I. grandifolia</em> as well as with three other co-localizing North American <em>Ipomoea </em>species – <em>Ipomoea cordatotriloba</em>,<em> Ipomoea lacunosa</em>, and <em>Ipomoea leucantha</em>. We also examined genetic differentiation using single nucleotide polymorphisms from leaf transcriptomes from multiple individuals of all five species and several outgroup species. We find no cross-incompatibility and little genetic differentiation between <em>Ipomoea </em>Carolina morphotype and <em>Ipomoea grandifolia</em>, suggesting that<em> Ipomoea </em>Carolina morphotype is a representative of <em>Ipomoea grandifolia</em>. This finding raises additional questions about the origins of <em>Ipomoea grandifolia</em> in North America and how its disjunct distribution could play a role in the divergence of <em>Ipomoea grandifolia</em> in the future.</p>