Abstract Detail


Specht, Chelsea [1], Landis, Jacob [2], Valderrama, Eugenio [3], Andre, Thiago [4], Skinner, David [5], Maas, Paul J.M. [6], Maas-van de Kamer, Hiltje [6], Almeida, Ana Maria [7].

Genetic mechanisms underlying the convergent evolution of pollination syndromes in the Neotropical radiation of Costus L.

Selection can act to mold the characteristics of flowers and inflorescences driven by their predominant or most effective pollinators. Within the Zingiberales, the genus Costus L is known for having traits that are strongly associated with discrete pollinator guilds, resulting in species that are characterized as either bee pollinated (mellitophilous) or bird pollinated (ornithophilous). In this study, we investigate correlated trait evolution among floral and inflorescence traits associated with pollinator guilds in the Neotropical Costus clade. In order to investigate the evolution of pollination-associated traits among species and morphotypes, we estimated phylogenetic relationships across 175 accessions that include biogeographic and phenotypic variation for Neotropical Costus L. We use further analyze relationships of a subset of 20 closely-related species with differing pollination syndromes using a phylogenetic network approach with SNPs identified based on a newly assembled draft genome. Signatures of selection in candidate genes involved in shifts of pollination syndromes were estimated in PAML using dN/dS ratios to test for differences in these signatures between species with particular mellitophilous v. ornithophilous traits. We found that the recent radiation of Neotropical Costus encompasses unacknowledged diversity, and that the evolution of floral traits across the genus illustrates that several morphological traits associated with pollination syndromes and herbivory are correlated and are under selective pressures indicative of responses to involvement in complex ecological networks. Our results show that traits related to pollination syndromes (i.e. floral shape, floral patterns, bract color) are strongly correlated and have been gained and lost in concert several times throughout the evolution of the genus. In addition, the presence or absence of bract appendages, uncorrelated with floral traits, is correlated with two traits associated with defenses against herbivory. While labellum shape is strongly correlated with overall pollination syndrome, we tested the impact of labellum shape on diversification rates and found no significant association. Most of the loci used for phylogenetic inference show strong purifying selection, however many candidate genes associated with functional traits such as floral color, fusion, size, and symmetry show evidence of adaptive selection, providing evidence of the genetic underpinnings of these pollination-associated traits. The genome wide SNPs, along with the overall phylogeny highlight that multiple shifts in pollination strategy have occured in Costus, while also highlighting the potential for homoplasy in signatures of selection. Overall, evidence suggests an interplay of pollination success with other selective pressures shaping the evolution of the Costus inflorescence. The evidence presented here will guide many hypotheses, most likely to be tested at the population or species-pairs level, addressing the genomic mechanisms and the evolutionary ecology of these traits associated with the morphological diversity and evolution of pollination syndromes across this diverse lineage of the Neotropical Costaceae.

1 - Cornell University, Plant Biology, Plant Science, 236 Tower Road, Ithaca, NY, 14851, United States
2 - Cornell University
3 - Cornell University, Plant Biology, CALS, 510 Mann Library, Ithaca, NY, 14853, United States
4 - Universidade Federal do Oeste do Pará
5 - Le Jardin Ombragé, Tallahassee, FL, USA
6 - Naturalis Biodiversity Center, Botany Section, Leiden, Netherlands
7 - California State University East Bay, Department Of Biology, 25800 Carlos Bee Blvd, Hayward, CA, 94542, United States

Pollination syndrome
floral evolution
genetic mechanisms
correlated trait evolution
Costus L..

Presentation Type: Oral Paper
Number: MACRO II003
Abstract ID:331
Candidate for Awards:None

Copyright © 2000-2022, Botanical Society of America. All rights reserved