Ana Paula Moraes1, Thaissa Brogliato Junqueira Engel2, Eliana R Forni-Martins2, Fábio de Barros3, Leonardo P Felix4, Juliano Sarmento Cabral5. 1. Universidade Federal do ABC - UFABC, Centro de Ciências Naturais e Humanas, São Bernardo do Campo, 09606-070, São Paulo, Brazil. 2. Universidade de Campinas - UNICAMP, Instituto de Biologia, Departamento de Biologia Vegetal, Programa de Pós Graduação em Biologia Vegetal, Campinas, 13083-970, São Paulo, Brazil. 3. Instituto de Botânica, Núcleo de Pesquisa Orquidário do Estado, São Paulo, 04045-972, São Paulo, Brazil. 4. Universidade Federal da Paraíba - UFPB, Campus II, Departamento de Ciências Biológicas, Areia, 58397-000, Paraíba, Brazil. 5. University of Würzburg, Ecosystem Modeling, Center for Computational and Theoretical Biology (CCTB), Klara-Oppenheimer-Weg 32, D-97074, Würzburg, Germany.
Abstract
BACKGROUND AND AIMS: The entangled relationship of chromosome number and genome size with species distribution has been the subject of study for almost a century, but remains an open question due to previous ecological and phylogenetic knowledge constraints. To better address this subject, we used the clade Maxillariinae, a widely distributed and karyotypically known orchid group, as a model system to infer such relationships in a robust methodological framework. METHODS: Based on the literature and new data, we gathered the chromosome number and genome size for 93 and 64 species, respectively. We built a phylogenetic hypothesis and assessed the best macroevolutionary model for both genomic traits. Additionally, we collected together ecological data (preferences for bioclimatic variables, elevation and habit) used as explanatory variables in multivariate phylogenetic models explaining genomic traits. Finally, the impact of polyploidy was estimated by running the analyses with and without polyploids in the sample. KEY RESULTS: The association between genomic and ecological data varied depending on whether polyploids were considered or not. Without polyploids, chromosome number failed to present consistent associations with ecological variables. With polyploids, there was a tendency to waive epiphytism and colonize new habitats outside humid forests. The genome size showed association with ecological variables: without polyploids, genome increase was associated with flexible habits, with higher elevation and with drier summers; with polyploids, genome size increase was associated with colonizing drier environments. CONCLUSIONS: The chromosome number and genome size variations, essential but neglected traits in the ecological niche, are shaped in the Maxillariinae by both neutral and adaptive evolution. Both genomic traits are partially correlated to bioclimatic variables and elevation, even when controlling for phylogenetic constraints. While polyploidy was associated with shifts in the environmental niche, the genome size emerges as a central trait in orchid evolution by the association between small genome size and epiphytism, a key innovation to Neotropical orchid diversification.
BACKGROUND AND AIMS: The entangled relationship of chromosome number and genome size with species distribution has been the subject of study for almost a century, but remains an open question due to previous ecological and phylogenetic knowledge constraints. To better address this subject, we used the clade Maxillariinae, a widely distributed and karyotypically known orchid group, as a model system to infer such relationships in a robust methodological framework. METHODS: Based on the literature and new data, we gathered the chromosome number and genome size for 93 and 64 species, respectively. We built a phylogenetic hypothesis and assessed the best macroevolutionary model for both genomic traits. Additionally, we collected together ecological data (preferences for bioclimatic variables, elevation and habit) used as explanatory variables in multivariate phylogenetic models explaining genomic traits. Finally, the impact of polyploidy was estimated by running the analyses with and without polyploids in the sample. KEY RESULTS: The association between genomic and ecological data varied depending on whether polyploids were considered or not. Without polyploids, chromosome number failed to present consistent associations with ecological variables. With polyploids, there was a tendency to waive epiphytism and colonize new habitats outside humid forests. The genome size showed association with ecological variables: without polyploids, genome increase was associated with flexible habits, with higher elevation and with drier summers; with polyploids, genome size increase was associated with colonizing drier environments. CONCLUSIONS: The chromosome number and genome size variations, essential but neglected traits in the ecological niche, are shaped in the Maxillariinae by both neutral and adaptive evolution. Both genomic traits are partially correlated to bioclimatic variables and elevation, even when controlling for phylogenetic constraints. While polyploidy was associated with shifts in the environmental niche, the genome size emerges as a central trait in orchid evolution by the association between small genome size and epiphytism, a key innovation to Neotropical orchid diversification.
Authors: Maïté S Guignard; Richard A Nichols; Robert J Knell; Andy Macdonald; Catalina-Andreea Romila; Mark Trimmer; Ilia J Leitch; Andrew R Leitch Journal: New Phytol Date: 2016-02-15 Impact factor: 10.151