Resolving the genera Aloysia and Acantholippia within tribe Lantaneae (Verbenaceae), using chloroplast and nuclear sequence data

Abstract

Species belonging to the genera Aloysia and Acantholippia are difficult to place within Lantaneae due to gene tree incongruence and limited sampling in previous studies. We use an expanded sample of both genera, and DNA sequence data from six loci, to reveal that Aloysia and Acantholippia species occur in five consistently inferred, well-supported clades. The precise relationships of these clades to one another are still enigmatic, due to gene tree incongruence. However, coalescent-based species tree inference supports the inclusion of most of Acantholippia in an expanded Aloysia sensu lato, with a 4-lobed calyx as its defining feature. Five new combinations are proposed to reflect this relationship: Aloysia deserticola, Aloysia riojana, Aloysia salsoloides, Aloysia tarapacana, and Aloysia trífida. Geographic range shifts from subtropical South America to North America have occurred at least twice in Aloysia. Shifts between determinate and indeterminate inflorescence arrangement have occurred at least twice independently. The elongate, lax inflorescence, which is characteristic of most of Aloysia, is hypothesized to be derived from a condensed inflorescence.