Genetic affinity of the rare eastern Texas endemic Hibiscus dasycalyx (Malvaceae)

Hibiscus dasycalyx is a rare eastern Texas endemic that shares key morphologic traits with two widespread sympatric congeners, H. laevis and H. moscheutos. Working with an initial hypothesis that these taxa were possible ancestors of the endemic through diploid hybridization speciation, a ten‐enzyme electrophoretic screening was conducted to determine whether H. dasycalyx exhibits a hybrid genetic profile. The three taxa share predominant alleles for all enzyme systems except ADH, GPI, and PGM, for which H. dasycalyx and H. laevis display generally identical banding patterns that differ from those of H. moscheutos. An analysis of diagnostic leaf shape and calyx pubescence features of eastern Texas H. laevis revealed substantial variation among populations, including forms intermediate between typical H. laevis and H. dasycalyx. In greenhouse hand‐pollinations, H. dasycalyx plants serving as ovule parents were freely compatible with H. laevis. Due to the possession of identical isozymes, the occurrence of morphologically intermediate populations where the species cooccur and exhibit an apparent lack of reproductive isolation, the endemic H. dasycalyx may be best regarded as a subspecies or variety of H. laevis , the taxon it most resembles morphologically. Conservation efforts should consider the potential effects of contaminating gene flow with typical H. laevis.