Comparative floral morphology and anatomy of Anacardiaceae and Burseraceae (Sapindales), with a special focus on gynoecium structure and evolution

摘要

Anacardiaceae and Burseraceae are traditionally distinguished by the number of ovules (1 vs. 2) per locule and the\uddirection of ovule curvature (syntropous vs. antitropous). Recent molecular phylogenetic studies have shown that\udthese families are sister groups in Sapindales after having been separated in different orders for a long time. We\udpresent a comparative morphological study of the flower structure in both families. The major clades, usually\udsupported in molecular phylogenetic analyses, are well supported by floral structure. In Anacardiaceae, there is a\udtendency to gynoecium reduction to a single fertile carpel (particularly in Anacardioideae). The single ovule has a\udlong and unusually differentiated funicle, which connects with the stylar pollen tube transmitting tract in all\udrepresentatives studied. In Anacardiaceae–Spondiadoideae, there is a tendency to form an extensive synascidiate\udzone, with a massive remnant of the floral apex in the centre; these features are also present in Beiselia\ud(Burseraceae) and Kirkiaceae (sister to Anacardiaceae plus Burseraceae) and may represent a synapomorphy or\udapomorphic tendency for the three families. In core Burseraceae, gynoecium structure is much less diverse than\udin Anacardiaceae and has probably retained more plesiomorphies. Differences in proportions of parts of the ovules\udin Anacardiaceae and Burseraceae are linked with the different direction of ovule curvature.