Distribuição geográfica, modelagem de nicho ecológico e taxonomia de espécies endêmicas de Manihot Mill. no Nordeste do Brasil

Abstract

Among the taxa of Euphorbiaceae, Manihot Mill. stands out for its great cultural, economic and social importance for Brazil. The genus includes about 150 species and has a Neotropical distribution, with the Amazon being its probable center of origin. Brazil has approximately 120 species, of which approximately 100 are endemic. Endemic species of Manihot constitute a plant genetic heritage that can be used in breeding programs for the cultivable species Manihot esculenta, through the transfer of genes of interest, helping to solve several problems, such as intolerance to periods of drought, high temperatures, low protein and pest content. At the same time, wild populations, especially endemic species, are under constant threat due to habitat destruction and climate change. In this work, we aim to identify the distribution patterns of Manihot species endemic to the Brazilian Northeast under current and future climate scenarios (accentuation of climate change) associated with a taxonomic study, evaluate the potential effects of climate change on the geographical distribution of endemic species of genus Manihot in Northeast Brazil and confirm the presence of the suitability area in protected areas in the future. In the first chapter, the results of the taxonomic study are presented, including descriptions, illustrations, lectotypification, conservation status, distribution and richness of endemic species of Northeastern Brazil. Fifteen endemic species were recognized, five of which were lectotypified (M. dichotoma, M. jacobinensis, M. maracasensis, M. reniformis and M. zehntneri). Among the studied species, 80% are in some category of threat, 13% are near threatened and only 7% fit in the category of least concern. Bahia stands out for the high degree of endemism of Manihot with 14 species. Only one species was found to be endemic to the states of Sergipe and Alagoas. The Caatinga records the highest number of species (8), followed by Cerrado (6) and Atlantic Forest (4). The Serra do Espinhaço, in the Bahia sector, is home to the greatest richness of endemic species in Manihot, and they are especially associated with the Chapada Diamantina National Park. The second chapter presents the results of ecological niche modeling of 11 Manihot endemic species for the Northeast, of which we predict the current and future geographic distribution for the year 2100, using three different general circulation models (CNRM, MIROC and MRI) and two climate change scenarios. We found that 45% and 54% of species could have a partial reduction in their total range potential by the year 2100 in an optimistic and pessimistic scenario, respectively, but some other species will increase their distribution. We found that the area of future suitability for most species is within the boundaries of some protected area. However, species that currently have a restricted distribution, and that their potential range will be reduced in both the optimistic and pessimistic scenarios, need to be prioritized for conservation. This study provides valuable information on the future distribution of the endemic species of Manihot and shows that climate change can have a potential positive or negative effect on the geographic distribution of the species. They also help to understand the distribution of species and can provide subsidies for actions to develop public policies for the conservation of taxa and phytogeographic domains, especially those that are seriously threatened.