Abstract Detail

Systematics

Donoghue, Michael [1], Srivastav, Mansa [2], Clement, Wendy [3].

Morphological evolution and diversification in the Dipsacales.

Over the past several decades, significant advances have been made in resolving evolutionary relationships within the Dipsacales, a clade of ca. 1,100 campanulid angiosperms. Most recently, we have reconstructed the Dipsacales phylogeny with Hyb-Seq data using the Angiosperms353 probe kit as well as plastomes recovered from off-target reads. Further, we have scored ~80 morphological characters across the Dipsacales and used these data to reconstruct a phylogeny to compare with nuclear and plastid trees, and also to infer morphological evolution. Using our current understanding of Dipsacales phylogeny in combination with these morphological data and a carefully vetted set of Dipsacales fossils, we present a detailed account of the evolution of the clade and highlight the remaining questions that depend on the resolution of contentious relationships of a few key lineages. First, we find much congruence among tree topologies recovered from nuclear, plastid, and morphological data, but also a few persistent differences that have consequences for understanding the evolution of key flower and fruit traits. We can confidently infer that the first Dipsacales were woody plants with simple opposite leaves and sympetalous flowers with five stamens alternating with five corolla lobes. Fruit evolution is less certain, but we favor the view that the first Dipsacales had septicidal capsules, which were retained in the Diervilla+Weigela lineage. Adoxaceae likely evolved somewhat smaller, rotate corollas, and fleshy fruits with a reduced number of seeds enclosed in endocarps, while Caprifoliaceae, in contrast, evolved long, tubular, bilaterally symmetrical corollas, a long style with a capitate stigma, and nectaries of hairs at the base of the corolla tube. The more difficult morphological inferences concern the much-contested positions of Heptacodium and Zabelia, which, regardless of their placement, imply significant homoplasy. For instance, the best-supported placement of Heptacodium with the Caprifolieae implies that inflorescence form in these groups is homologous, while there must have been homoplasy in carpel abortion, fruit type, and calyx lobes. The possibility that Zabelia is related to Morina and its relatives implies homoplasy in plant habit and calyx lobes, but this may be supported by a suite of pollen and corolla characters. With respect to the timing of diversification, we infer an older age for crown Dipsacales than most prior studies, but it appears that age estimates for a number of included clades are heavily influenced by differences in rates of evolution that are linked to plant life history.

1 - Yale University, Department Of Ecology And Evolutionary Biology, 21 Sachem St., New Haven, CT, 06511, United States
2 - Yale University, Ecology And Evolutionary Biology, 420 Temple Street, Helen Hadley Hall, Environmental Science Center, Room Number 356, New Haven, CT, 06511, United States
3 - The College Of New Jersery, Dept. Of Biology, 2000 Pennington Road, Ewing, NJ, 08628, United States

Keywords:
phylogeny
homoplasy
Heptacodium
Zabelia
Morinoideae
floral evolution
fruit evolution.

Presentation Type: Oral Paper
Session: SYSTI, Systematics I: Euasterids II
Location: Virtual/Virtual
Date: Tuesday, July 20th, 2021
Time: 11:30 AM(EDT)
Number: SYSTI007
Abstract ID:926
Candidate for Awards:None