Phylogeny of the AustralianSolanum dioicumgroup using seven nuclear genes: Testing Symon’s fruit and seed dispersal hypotheses

AbstractThe dioecious and andromonoeciousSolanumtaxa (previously described as the “S. dioicumgroup”) of the Australian Monsoon Tropics have been the subject of phylogenetic and taxonomic study for decades, yet much of their basic biology is still unknown. This is especially true for plant-animal interactions, including the influence of fruit form and calyx morphology on seed dispersal. We combine field/greenhouse observations and specimen-based study with phylogenetic analysis of seven nuclear regions obtained via a microfluidic PCR-based enrichment strategy and high-throughput sequencing, and present the first intron-containing nuclear gene dataset in the genusSolanumand the first species-tree hypothesis for theS. dioicumgroup. Our results suggest that epizoochorous trample burr seed dispersal (strongly linked to calyx accrescence) is far more common among AustralianSolanumthan previously thought and support the hypothesis that the combination of large fleshy fruits and endozoochorous dispersal represents a reversal in this study group. The general lack of direct evidence related to biotic dispersal (epizoochorous or endozoochorous) may be a function of declines and/or extinctions of vertebrate dispersers. Because of this, some taxa might now rely on secondary dispersal mechanisms (e.g. shakers, tumbleweeds, rafting) as a means to maintain current populations and establish new ones.