Climatic niches and geographical ranges of sugarcane wild relatives: a comparative and evolutionary approach

• Ano de defesa: 2020
• Autor(a) principal: Carvalho, Igor Araujo Santos de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Climatic niches; Distribuição geográfica; Geographical ranges; Nicho climático; Parentes selvagens da cana-de-açúcar; Sugarcane wild relatives
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/11/11137/tde-05052020-103150/

Species distributions are the result of the interplay between ecological requirements and evolutionary mechanisms, which are studied by ecological and historical biogeography, respectively. Although these fields have been historically separate, the concept of ecological niche has allowed their integration. The modelling of ecological niches and species distributions in light of the evolutionary processes has allowed the filling of considerable gaps of scientific knowledge about biodiversity. These gaps are especially relevant for a group of plants known as crop wild relatives (CWR), which are a valuable genetic resource with a crucial role in guaranteeing food security. In this dissertation, we used available occurrence data and bioclimatic variables to model the potential geographic distribution of 15 species of the sugarcane relatives and to characterize their niches in a bidimensional environmental space. We also reconstructed a recently published phylogeny and used it to investigate the predominant mechanism of speciation and the mechanisms shaping niche evolution in the group. The results showed that sugarcane relatives are potentially distributed worldwide and that range models can be used to inform future collection expeditions, considering that the relatives of this crop is one of the most underrepresented in genebanks. Closely related species show a high degree of sympatry with asymmetrical ranges, whilst species from different clades occur in total allopatry. We found a significant negative correlation between age of divergence between clades and pairwise level of sympatry, which suggests that the current geographical distribution may be a result of long-distance dispersion followed by recent events of sympatric speciation. Characterization of niches showed that climatic variables related to minimum temperatures and aridity were the ones that most contributed to variation among climatic niches of theses species. Whilst most species show narrow climatic niches, two show a very broad niche. In general, sugarcane relatives\' climatic niches are not identical and are just similar as expected by chance, even though closely related species showed the highest levels of niche overlap. Additionally, models of evolution suggests that different processes acted to shape the climatic tolerances of sugarcane wild relatives, the first dimension of climatic niches related to minimum temperature was best modelled by a Ornstein-Uhlenbeck model with two optima and the dimension related to aridity is best modelled by a Brownian Motion model. Therefore, our study shows the importance of using already available data to analyse the ecological attributes and evolutionary aspects of CWR, which can be used to foment conservation initiatives and a more efficient use of these species in breeding.