NASCENT INFLORESCENCES IN XYLOCOCCUS AND ORNITHOSTAPHYLOS AND THEIR POTENTIAL ECOLOGICAL ROLE

The shift from fleshy to dry fruit in phylogenetic lineages is assumed to be an adaptation to climates in which plants experience dry, potentially stressful conditions during fruit maturation. Arctostaphylos Adans. (Ericaceae) is a good example of this, and the transition to dry fruit is accompanied by earlier flowering that permits earlier fruit development. Earlier flowering in Arctostaphylos is accomplished by dormant inflorescences produced the previous year. These dormant inflorescences, termed nascent inflorescences, are immature rachises and flower buds that develop at the end of the previous season's new stem growth, facilitating the earlier flowering and fruiting phenology. Recent work has shown that two other related genera in the Arbutoideae, Xylococcus Nutt. and Ornithostaphylos Small, share similar traits of earlier phenology in flowering and fruit production as well as dry fruit at maturity. The current study investigates whether Xylococcus and Ornithostaphylos also produce nascent inflorescences like Arctostaphylos. Nascent inflorescences are used as an important taxonomic character in Arctostaphylos, but there has been no discussion of their ecological role, and current hypotheses are provided for context. Field observations confirmed the presence of nascent inflorescences in the two sister Arbutoid genera, suggesting a larger ecological role as part of a reproductive trait syndrome.