Systematics of the Tribe Astronieae Based on Morphology: Prospects for Resurrecting Bamlera and Incorporating Tessmannianthus

Abstract

The Astronieae, as traditionally circumscribed, comprise 136 woody species in four genera, Astrocalyx, Astronia, Astronidium, and Beccarianthus, and are endemic to the Malesian, Papuasian, and Pacific Island rainforests. Initial molecular phylogenetic analyses suggested the monophyly of some genera and the closer relationship between the Neotropical Tessmannianthus and the Astronieae, but sparse sampling has left generic circumscriptions and relationships between genera and species uncertain. This chapter presents the first phylogenetic analysis of the tribe with broad sampling based on morphological data. Parsimony analyses of 57 taxa (as traditionally defined) with 205 discrete and continuous morphological characters were conducted to test the support for the monophyly of each genus and explore the morphological relationships with Tessmannianthus. The analysis of combined discrete and continuous characters shows that Astrocalyx, Astronia, and Astronidium are each monophyletic with varying degrees of support. Beccarianthus is biphyletic, comprising one clade with oblong and another with linear anthers, with the latter comprising the genus Bamlera that is restricted to New Guinea. Tessmannianthus is resolved as sister to the Astronieae (excluding T. cereifolius), when including partitioned discrete characters, and as sister to the Merianieae when including continuous characters. The phylogeny of Astronieae s.s. suggests an evolutionary change of placentae from axile to basal-axile and, ultimately, collapsed.