Embryology of Eusideroxylon (Cryptocaryeae, Lauraceae) and character evolution in the family

Abstract

Lauraceae are relatively well-known embryologically and embryological data are available for 23 of about 50 genera. In this paper we present the embryology of Eusideroxylon, an unstudied and key genus within Cryptocaryeae, which are positioned basally in the evolution of Lauraceae, and discuss the evolution of embryological characters in the family. Based on comparisons of over 50 characters, it was found that Eusideroxylon is consistent with Aspidostemon, the core Cryptocaryeae (Beilschmiedia, Cryptocarya, Endiandra and Potameia), Caryodaphnopsis and Cassytha in having a glandular anther tapetum. The core Cryptocaryeae further agrees with both Caryodaphnopsis and Cassytha in having an embryo sac protruding from the nucellus. In light of the phylogenetic trees available, both the glandular tapetum and the embryo sac protruding from the nucellus have evolved as homoplasies in Lauraceae, once each in a clade of Cryptocaryeae, and the Caryodaphnopsis and Cassytha clade, respectively. Such character-state distributions suggest that it is better to place both Caryodapnopsis and Cassytha in the same clade as the core Cryptocaryeae. Embryologically, Eusideroxylon appears to have an intermediate state between Hypodaphnis, a genus positioned basal-most in the family, and the core Cryptocaryeae. Supplementary data on the anther and seed of Hypodaphnis are also provided.