| Field experiments and genetic markers were used to study the reproductive ecology and phylogeography of Trillium erectum and T. grandiflorum (Melanthiaceae), two spring woodland herbs in eastern North America. First, mating systems and determinants of fertility were investigated using controlled pollinations and allozyme assays. Both species possessed leaky self-incompatibility systems although T. erectum practiced more self-fertilization than T. grandiflorum . Pollen and resources limited seed fertility in T. grandiflorum . Second, phylogeographic approaches were used to investigate the history of both species following the Wisconsin glaciation. Based on variability in chloroplast DNA markers, a possible post-glacial migration route was proposed for T. grandiflorum. No variation in the chloroplast genome was detected in T. erectum. Analysis of allozyme variation indicated that gene flow is greater among populations of T. grandiflorum than of T. erectum. There was no loss of genetic diversity at allozyme loci in northern compared to southern populations of either species. |
