Abstract Detail

Macroevolution

Koehler, Samantha [1], Gomes, Shaiany [2], Campacci, Thiago [1], Costa, Gleicyanne [1], Moura, Yohans [1], Mayer, Juliana [1], Viccini, Lyderson [2].

Unraveling the role of apomixis and polyploidization in the diversification of Neotropical Zygopetalum orchids.

Polyploidization is a central process in plant diversification. Several studies have shown whole genome duplication events can favor reproductive isolation, morphological differentiation, and genomic and ecological changes leading to speciation. The orchid genus Zygopetalum emerges as a potential model to study the role of polyploidy in species diversification in the Neotropics, considering that apomixis and polyploidy have been described for this group. Species occur as epiphytes or on rocky outcrops in mountaintops in South-Southeastern Brazil and in the Andes. As a first step to understand processes of diversification within Zygopetalum, we propose to answer the following questions: (1) What is the taxonomic and geographical extension of polyploidization within this group? (2) Is apomixis restricted to polyploids? (3) Does pollen origin affect the production of apomictic seeds? (4) Is there a correlation between habitat and polyploidy? We described patterns of cytotype variation within and among populations and species. We compared fruit set, seed viability and embryo development between self- and cross-pollinated flowers, considering different cytotypes within the 'Z. maculatum' complex. We also inferred phylogenetic relationships within Zygopetalum based on matK, trnL-F and nrITS sequence data. DNA content consistent with tetraploidy was observed in two species from rocky outcrops, the 'Z. maculatum' complex and Z. pedicelatum. The observed chromosome numbers were 2n=48, 72 and 96, each one with an average amount of 7.3, 10.5 and 14.0 pg of DNA, respectively. All species from forested areas and most specimens in marginal rocky outcrop populations have DNA content consistent with diploidy. In the 'Z. maculatum' complex, the number of apomictic seeds is greater in self-pollinated flowers, but there is no difference in viability between self- and cross-pollinated polyembryonic seeds, suggesting sexual reproduction has an important role in this group. Z. maxillare, Z. microphytum and Pabstia are phylogenetically more distant related than other species of Zygopetalum and Neogardneria murrayana, but phylogenetic relationships among species from forest areas and rocky outcrops were inconclusive. Additional studies on population genetics, cytogenetics, and embryogenesis are being developed to better understand processes of diversification within this group.

1 - Universidade Estadual de Campinas, Plant Biology, Rua Monteiro Lobato 255, Campinas, SP, 13083970, BRAZIL
2 - Universidade Federal de Juiz de Fora, Biology, Juiz de Fora, MG, 36036900, Brazil

Keywords:
polyploid diversification
asexual reproduction
Orchidaceae
rocky outcrops
DNA content.

Presentation Type: Poster
Session: P, Macroevolution Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PME001
Abstract ID:252
Candidate for Awards:None