Hernandiaceae

Abstract: Molecular and morphological phylogenetic studies in the Laurales have found that Hernandiaceae, Lauraceae, and Monimiaceae sensu stricto form a monophyletic group. Because of the paucity of phylogenetically informative substitutions, however, relationships among families within this clade remain unclear. In general, molecular phylogenies may conflict because of a variety of factors, including substitution rate variation among sites and lineages, taxon sampling, outgroup choice, and base compositional biases. We analyzed a total of 2846 aligned nucleotides from a plastid intron, three spacers, and a portion of the nuclear 26S rRNA gene in a sample of Hernandiaceae, Lauraceae, and Monimiaceae; we used four outgroups with differing substitution rates. Despite obtaining single best topologies with maximum likelihood, minimum evolution, and parsimony approaches, family relationships remained as poorly supported as they were in the previous molecular studies. Exploration of the data indicates that varying subst...

Abstract: Heterodichogamy is reported for the first time in the family Hernandiaceae (Laurales); furthermore, this heterodichogamy is of a novel type hitherto not reported in angiosperms. In Hernandia nymphaeifolia, which has unisexual flowers and is monoecious, two kinds of individuals were found: one kind with exclusively female flowers open in the morning and male flowers open in the afternoon and the other kind with the reverse behavior. The flowers are arranged in compound thyrses with cymes of two male and one female flower. Developmental studies confirm an earlier interpretation of these triads as monochasia with the sequence male‐male‐female. Surprisingly, though, the sequence is reversed at anthesis: most triads flower with the sequence male‐female‐male. Flower development shows that the gynoecium is unicarpellate (and not pseudomonomerous). In male flowers there are three rudimentary mounds (as yet overlooked) alternating with the stamens, which may correspond to those mounds in the female flowers that ar...

Abstract: Two representative genera of Hernandiaceae,Gyrocarpus andHernandia, were investigated embryologically to contribute to a better understanding of their respective evolutionary position. Comparisons with other lauralean families using Chloranthaceae or Annonaceae (as a representative of Magnoliales) as an outgroup of Laurales (if present, plus other related taxa) support a lauraceous affinity for the two genera because of the presence of ramified raphal vascular bundles at the chalaza (a synapomorphy), but do not provide evidence for the separation of Hernandiaceae from Lauraceae.Hernandia rather shares with Lauraceae two apomorphies (i.e., the seed pachychalazy and the ruminate seed) which may be homoplasies judged from results of cladistic and molecular studies published elsewhere.Hernandia is greatly divergent from an ancestral line common withGyrocarpus and is even diversified within the genus. Based on evidence from embryology as well as from other sources, it seems best to accept two separate subfamilies in Hernandiaceae as usually have been accepted: one is a derived subfamily Hernandioideae, and the other a less specialized Gyrocarpoideae.