Evolutionary history of Manihot carthagenensis (Euphorbiaceae) and allied species in eastern South America

• Ano de defesa: 2018
• Autor(a) principal: Silveira, Thamyres Cardoso da
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Microssatélites (Genética); Manihot carthagenensis - Filogenia; Filogeografia; Ciências Agrárias
• Link de acesso: http://www.locus.ufv.br/handle/123456789/21588

Manihot Mill. (Euphorbiaceae) is a Neotropical genus with approximately 100 species. Manihot carthagenensis is a very polymorphic species and associated with dry environments, mostly the caatinga and the chaco. Currently, morphological criteria associated with geographic distribution distinguish three infraspecific taxa in M. carthagenensis: M. carthagenensis subsp. carthagenensis, M. carthagenensis subsp. glaziovii, and M. carthagenensis subsp. hahnii. Herein, we assembled multilocus datasets with DNA sequence data obtained from four nuclear genes (sts, ch_metE, g3pdh, and nia-i3) for 34 samples of the three subspecies of M. carthagenensis and 14 samples from 10 closely-related species and carried out Bayesian phylogenetic analyses. We also obtained microsatellite data from 19 representative populations sampled throughout most of the known range of M. carthagenensis to investigate genetic structure and diversity. Our phylogenetic study suggested that M. carthagenensis, as presently circumscribed, does not constitute a monophyletic clade, but represents three well-differentiated lineages: M. carthagenensis, M. glaziovii and M. hahnii. These three lineages were supported based on morphological differences, genealogical relationships, and vegetation associations. Microsatellite data suggest that M. carthagenensis consists of at least three distinct gene pools partly structured according to geography. We hyphothesized that these gene pools evolved in allopatry but remained interfertile and were able to produce hybrid zones after reconnecting. Thereby the genetic admixture is of recent origin and owing to population expansion.