Abstract Detail

Symbioses: Plant, Animal, and Microbe Interactions

Novel molecular phylogeny of Passifloraceae reveals highly labile coevolutionary interactions with Heliconius butterflies.

Coevolution of plants and phytophagous insects is considered one of the major phenomena shaping biodiversity, yet the extent of its impact on speciation rates in either group remains controversial. Quantitative understanding of the coevolutionary process requires model systems that combine deep understanding of ecology with robust systematics. One such case is the predation of the cyanogenic Passifloraceae by the passion vine butterflies Heliconius, but long-standing hypotheses about the evolution of their ecological interplay cannot be verified in the absence of a quality, dated host phylogeny. Here I present a comprehensive chronogram of the family Passifloraceae and use it to address fundamental questions about the evolution of this charismatic group.Molecular data from several previous studies was synthesized, including 12 nuclear, mitochondrial and plastid genes from 283 species (out of approximately 750 Passifloraceae). Recovered topologies were robust to changes in the composition of heterogeneous sequence matrices, and the choices of optimality criteria. New placement of many groups (Multiflora, Cieca, Bryonioides) and polyphyly of major supersections suggest the need for a taxonomic revision. Known fossil material was reviewed to select highly reliable calibration points for Bayesian estimation of split times, which showed a Neotropical origin in the Eocene (95% HPD: 34.0-42.23 MYA) and a rapidly increasing rate of diversification in the late Miocene. However, biogeographic reconstructions demonstrate a complex history involving several invasions of Africa and Australasia, as well as re-invasions of Neotropics by African lineages.The novel phylogeny includes the majority of species attacked by Heliconius. Explicit comparisons of host and butterfly topologies revealed a pattern of partial cospeciation (event-based model, p<0.0001), whereby 138 of 502 ecological interactions documented in the wild were predicted by the phylogeny (AxParafit randomization, p<0.01). Close codivergence is largely limited to butterfly species in the clade of H. erato, characterized by their unique ability to sequester monoglycoside cyclopentenyl toxins from Passiflora. Contrary to earlier speculation, I find no evidence for increases in butterfly speciation rates driven by particular host shifts, even though the diversification of the two groups took place simultaneously. Morphological defenses against the butterflies arose independently and recently in multiple plant lineages, and no specific clade within Passifloraceae shows an increased rate of predation.The comprehensive phylogenetic reanalysis reveals that despite many ecological associations and mutual adaptations, passion vines and their butterflies have been surprisingly decoupled in their evolution.

1 - Smithsonian Tropical Research Institute, 401 Roosevelt Ave, Ancon Hill, Panama City, Panama, NA, Panama

Keywords:
Passifloraceae
Heliconius
host specificity
coevolution
macroevolution.

Presentation Type: Oral Paper
Session: SYMB1, Symbioses: Plant, Animal, and Microbe Interactions I
Location: Virtual/Virtual
Date: Tuesday, July 28th, 2020
Time: 1:00 PM
Number: SYMB1003
Abstract ID:825
Candidate for Awards:None