Survey of the fruits and endocarps of Icacinaceae (Lamiids, Icacinales)

Abstract

Icacinaceae Miers are a well-described family. However, the family lacks a comprehensive guide to endocarp morphology, which would be an important tool for interpreting the family’s extensive fossil record of endocarp remains. In this survey, we describe fruits and endocarps of 88 species of Icacinaceae s. str., four of Icacinaceae s. lat. (now Metteniusaceae) and one of Oncothecaceae. We investigated the value of the endocarp in species recognition. In addition, we generated an Xper3 database with an associated e-key to increase the availability of raw data and the understanding of the characters used. This study documents great diversity in epicarp hairs, mesocarp thickness, endocarp ornamentation, tubercle shape (if present), endocarp structure and thickness, and the locule lining. Some morphological features appear diagnostic for individual genera. In particular, the genus Iodes Blume, which is very common in the fossil record, is the only clade with the three following characters: papillae on the inner locule lining, ridged ornamentation on the endocarp surface, and a vascular bundle embedded within the endocarp wall. Finally, we discuss issues related to the preservation of fruit material in herbarium collections.