Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Appleton, Andrea [1], Schenk, John [2].

Patterns of Staminode Evolution in Paronychia (Caryophyllaceae).

Staminodes are infertile stamens that have evolved numerous times across angiosperms and exhibit a vast array of forms and functions. The variation in staminodial structures and functions suggests complex evolutionary processes underlie their origins, but to understand how and why these processes occur, comparative studies are needed in groups of closely related species. Identifying structures as staminodes, however, is not always straightforward and at times requires supporting phylogenetic and developmental approaches. Staminodial structures in Paronychia (Caryophyllaceae), for example, vary in shape and size across the species in which they are present, and they have been referred to as both petals and staminodes, rendering their identity uncertain. We used Paronychia as a model system to compare the evolution and development of staminodes across closely related species. We tested the hypotheses that these structures are either petals or staminodes by evaluating the floral development of fourteen North American species of Paronychia with scanning electron and light microscopy and conducted ancestral state estimations across phylogenies to infer when staminodes evolved. Staminodes developed between the outer androecial whorl and the carpel, indicating an androecial origin. In eight species, staminodes developed similar to the filaments of fertile stamen in shape, length, and time, suggesting homology to stamen filaments. In four species, staminodes are lost or highly reduced through heterochronic termination of development shortly following initiation. In two species, a change to broader staminodes compared to filaments of stamen in the same flower was interpreted as functional co-option. A vascular strand was not observed in any species examined, perhaps indicating that staminodes are vestigial prior to co-option. Staminodes evolved prior to the origin of Paronychia and were lost at least three times. We argue that staminodes in Paronychia began as vestigial structures following the loss of anthers and were either lost, remained vestigial, or coopted, which we refer to as the vestigial intermediate hypothesis. Our results illustrate a dynamic history of staminodial evolution in Paronychia, and that selection on the function of staminodes differs across closely related species.

1 - Georgia Southern University, Department of Biology, 4324 Old Register Road, Statesboro, GA, 30460, United States
2 - Ohio University, Department of Environmental and Plant Biology, 401 Porter Hall, Athens, OH, 45701-2979, USA

Keywords:
ancestral character estimation
androecium
Caryophyllaceae
development
evo-devo
evolution
floral development
floral evolution
Paronychia
Phylogenetics
staminodes.

Presentation Type: Oral Paper
Session: EVDV1, Evolutionary Developmental Biology (Evo-Devo)
Location: Virtual/Virtual
Date: Thursday, July 30th, 2020
Time: 12:30 PM
Number: EVDV1010
Abstract ID:297
Candidate for Awards:None