ABSTRACT
The boreotropical flora concept suggests that relictual tropical disjunctions between Asia and the Americas are a result of the expansion of the circumboreal tropical flora from the middle to the close of the Eocene. Subsequently, temperate species diverged at high latitudes and migrated to other continents. To test this concept, we conducted a molecular phylogenetic analysis (using cpDNA) of the Magnoliaceae, a former boreotropical element that currently contains both tropical and temperate disjuncts. Divergence times of the clades were estimated using sequences of matK and two intergenic regions consisting of psbA-trnH and atpB-rbcL. Results indicate the tropical American section Talauma branched first, followed by the tropical Asian clade and the West Indies clade. Within the remaining taxa, two temperate disjunctions were formed. Assuming the temperate disjunction of Magnolia acuminata and Asian relatives occurred 25 mya (late Oligocene; based on seed fossil records), section Talauma diverged 42 mya (mid-Eocene), and tropical Asian and the West Indies clades 36 mya (late Eocene). These events correlate with cooling temperatures during the middle to late Eocene and probably caused the tropical disjunctions.
ABSTRACT
The full length gene encoding the D1 protein of photosynthesis (psbA) has been cloned and sequenced from Magnolia pyramidata (Magnoliaceae). Despite considerable investigation into psbA structure and function in many algal lineages and a few agricultural plants, there has been little effort invested toward characterizing a broader range of plant psbA genes. This is the first report of a psbA gene sequence from a primitive angiosperm. The DNA and deduced amino acid sequences maintain high overall conservation with other taxa, suggesting a role for psbA in broad based angiosperm phylogenetic reconstruction.
Subject(s)
Magnoliopsida/genetics , Photosynthetic Reaction Center Complex Proteins/genetics , Ribulose-Bisphosphate Carboxylase , Cloning, Molecular , Genes, Plant/genetics , Photosystem II Protein Complex , Plant Proteins/genetics , RNA, Ribosomal, 18S/genetics , Sequence HomologyABSTRACT
We studied the effect of four ant species on the reproductive fitness (number of fruits produced) of Schomburgkia tibicinis (Orchidaceae), in the coast of Yucatan, Mexico. Ants forage day and night for the nectar produced by the reproductive structures of the orchid. Ant size is: Camponotus planatus (3-4 mm), C. abdominalis (4-6 mm), C. rectangularis (7-9 mm), and Ectatomma tuberculatum (9-12 mm). The results indicate that ant efficiency in disrupting the activities of the main herbivore, (Stethobaris sp./Coleoptera) varies, and that it is apparently related to ant size, three tendencies are clear: (a) lowest fruit production and highest inflorescence damage are significantly associated with the smaller ants and the control; (b) maximum fruit production and minimum inflorescence damage are significantly associated with the larger ant species; and (c) the increase in ant size tends to have a positive effect on the plant's reproductive output (less dead spikes and more matured fruits). We discuss ant effect on the pollination of the orchid, and emphasize that ant presence should not be associated, in general, with benefit to plants.
ABSTRACT
The primitive and vesselless angiosperm Zygogynum (Winteraceae), which is restricted to New Caledonia, is pollinated by a moth, Sabatinca (Micropterigidae). Fossil records of both the moth and the plant families extend to the Early Cretaceous. Adult Sabatinca have grinding mandibles and usually feed on the spores of ferns and on pollen. The insects use the flowers as mating sites and eat the pollen which is immersed in a dense pollenkitt. This mode of pollination in which flowers serve as mating and feeding stations with floral odors acting as cues may have been common in the early evolution of flowering plants.