文摘
Lactoridaceae are a monotypic family confined to the Juan Fernandez (= Robinson Crusoe) Islands, Chile, an archipelago four million years old. Interest in the lone species, Lactoris fernandeziana, has increased in recent years due to its suspected role in early angiosperm evolution, as well as its endangered conservation status. Reports of fossil pollen of Lactoris (as Lactoripollenites) from deep sea sediments of Cretaceous age off the western coast of South Africa provide evidence for southern hemisphere occurrence of the family 70–90 million years ago. This age, plus trimerous symmetry and simple morphology of the flower with three tepals, six stamens and three nearly free carpels with laminar placentation, involve the family with hypotheses regarding evolution of early angiosperms, especially paleoherb and monocot divergences. Based on cladistic analyses with morphological and nucleotide data, recommended taxonomic placement of Lactoris is as a monotypic order, Lactoridales, allied most closely to Aristolochiales, and also near Piperales. Approximately 1000 individuals of Lactoris are believed to exist, and genetic variation within and among populations as measured by isozymes and RAPDs is low. This, in part, could be due to the self-compatibility and geitonogamous breeding system of this wind-pollinated species. More efforts at ex situ conservation should be attempted so that this important angiosperm family is maintained for future evolutionary studies.
