Abstract Detail

Development and Structure

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

Androecial Evolution in the Dioecious Species of Paronychia (Caryophyllaceae).

Staminodes are commonly studied in hermaphroditic flowers where a fraction of the stamens in the androecium evolve into infertile structures, but few studies address the evolution of staminodes as they occur through loss of staminate function in carpellate flowers of dioecious species. Flowers of Paronychia (Caryophyllaceae) are ancestrally hermaphroditic and staminodial, with the exception of the dioecious P. chartacea and P. minima. The derived unisexual flowers that contain symplesiomorphic staminodes at alternisepalous positions provides a unique opportunity to study the repeated evolution of androecial reduction and staminode evolution. Using scanning electron microscopy, we observed floral development in carpellate and staminate flowers in P. chartacea and P. minima to address the following questions: (1) Was the reduction of the antesepalous stamens in the carpellate flowers also associated with a further reduction or loss of the symplesiomorphic, alternisepalous staminodes, and (2) do the more recently derived, antesepalous staminodes in carpellate flowers develop similar to the alternisepalous staminodes? In carpellate flowers of both species, the antesepalous staminodes initiate after sepals but prior to when alternisepalous staminodes initiate. The antesepalous staminodes initiate as anther-like structures that develop similar to stamens of staminate or hermaphroditic flowers in shape and timing, but are soon arrested, leaving behind a broad, rudimentary anther with lateral lobes that would have corresponded to thecae. After the antesepalous staminodes stop developing, the alternisepalous staminodes initiate and are homologous with filaments. The alternisepalous staminodes of carpellate flowers are phenotypically and developmentally similar to the staminodes in the same positions in staminate flowers. We conclude that (1) as flowers evolved from bisexual to unisexual, only antesepalous stamens in carpellate flowers were reduced to staminodes and the alternisepalous staminodes were not further reduced, and (2) the two whorls of staminodes in carpellate flowers are not structurally homologous, as the antesepalous staminodes are rudimentary anthers and the alternisepalous staminodes are rudimentary filaments. The reduction of antesepalous stamens but not alternisepalous staminodes and the difference in the homology of the staminodes in the two positions together suggests separate developmental genetic controls of the two androecial whorls, but how the flowers partition the androecium to be controlled by separate genetic mechanisms is not understood.

1 - 17931 Highway 67 Apt 2801, Statesboro, GA, 30458, United States
2 - Ohio University, Department Of Environmental And Plant Biology, 22 Richland Ave., 401 Porter Hall, Athens, OH, 45701, United States

Keywords:
androecium
Caryophyllaceae
development
Dioecy
evo-devo
floral evolution
homology
heterochrony
Paronychia
stamen
staminode.

Presentation Type: Oral Paper
Session: DS1, Development and Structure I
Location: /
Date: Tuesday, July 20th, 2021
Time: 1:00 PM(EDT)
Number: DS1012
Abstract ID:184
Candidate for Awards:Developmental and Structural Section Undergraduate Student Registration Award