Abstract Detail

Anatomy and Morphology

L. Cunha Neto, Israel [1], Pace, Marcelo [2], Douglas, Norman [3], H. Nee, Michael [4], C. F. de Sá, Cyl [5], Moore, Michael [6], Angyalossy, Veronica [7].

Stele diversity and evolution in Nyctaginaceae: medullary bundles across the family.

Distantly related plant groups have independently evolved medullary bundles - vascular units dispersed within the pith. This anatomical feature is called a polycyclic eustele, as opposed to the regular eustele common to most gymnosperms and eudicots. The large and diverse order Caryophyllales has several families with a polycyclic eustele, with some families displaying medullary bundles in a few representatives, while in others they are widespread (e.g., Nyctaginaceae). In this study, we performed a broad comparative study for Nyctaginaceae combining stem ontogeny with phylogenetic comparative methods to investigate the diversity and evolution of the primary vascular system within the family. We described two eustele subtypes, the regular eustele - consisting of a single ring of vascular bundles -, and the polycyclic eustele, characterized by medullary bundles and a continuous concentric procambium, that later forms an extra ring of vascular bundles delimiting the pith. Medullary bundles developed by a single shared ontogenetic pathway, i.e., originating as vascular traces from lateral appendages (e.g., leaves, thorns, inflorescences). Nevertheless, different arrangements emerged considering their number and organization in stem cross section, which are unrelated to phyllotaxy, habit, and habitat. The polycyclic eustele was shown to be a symplesiomorphy for Nyctaginaceae, while the regular eustele emerged as a synapomorphy of Leucastereae. If this character is reconstructed in a larger phylogenetic context, including Nyctaginaceae and its sister families, i.e., Agdestidaceae, Phytolaccaceae, and Sarcobataceae, the most recent common ancestor of this entire clade is similarly reconstructed as having a polycyclic eustele. In this scenario, the regular eustele in tribe Leucastereae reconstructs as a reversal (an independent evolution) to the character state ancestral for all lignophytes (the clade including extinct progymnosperms, gymnosperms, and angiosperms, all having a bifacial vascular cambium), which is thought to be a regular eustele. On the other hand, the presence of a polycyclic eustele in Nyctaginaceae and close-related families likely constitutes a synapomorphy for the phytolaccoid clade and symplesiomorphy for Nyctaginaceae. Whether the same developmental genetic pathways are responsible for the presence of medullary bundles in these Caryophyllalean families is something to be addressed in future studies. 

1 - University Of São Paulo, Departamento De Botânica, Rua Do Matão, 277, Instituto De Biociências, Cidade Universitária, São Paulo, SP, 05508-090, Brazil
2 - Universidad Nacional Autónoma De México, Botánica, Circuito Zona Deportiva Sn De Ciudad Universitaria, Ciudad De Mexico, DIF, 04510, Mexico
3 - University Of Florida, Biology, PO Box 118525, Gainesville, FL, 32611, United States
4 - New York Botanical Garden, USA
5 - Jardim Botânico do Rio de Janeiro, RJ, Brasil
6 - Oberlin College, Department Of Biology, 119 Woodland St., Science Center K111, Oberlin, OH, 44074, United States
7 - Universidade De São Paulo, Botany, Rua Do Matao 277, Sao Paulo, SP, 05508-090, Brazil

Ancestral character state reconstruction
stem anatomy
vascular system.

Presentation Type: Oral Paper
Session: AM1, Anatomy and Morphology
Location: Virtual/Virtual
Date: Wednesday, July 29th, 2020
Time: 1:15 PM
Number: AM1013
Abstract ID:244
Candidate for Awards:Katherine Esau Award,Maynard F. Moseley Award

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