Distribuição geográfica e respostas às mudanças climáticas no peixe rivulídeo Anablepsoides cearensis (Costa & Vono, 2009): uma abordagem integrativa entre conservação filogenética de nicho (CFN) e modelos de nicho ecológico (MNE)

Abstract

The Rivulidae family is the most threatened group of freshwater fish in Brazil. Species in this family are small, colorful, and can be classified into two groups based on their adaptations to shallow water bodies: annual species from seasonal environments, and non-annual species from swamps or perennial wetlands. Most rivulids from the Caatinga are annual, with few non-annual representatives. Among these, Anablepsoides cearensis (Costa & Vono, 2009) is the only non-annual rivulid endemic to the Brazilian semiarid region, belonging to a primarily Amazonian group and currently classified as 'critically endangered' due to its restricted and fragmented distribution, and potential threats. After its description in a shallow stream within a forest fragment in São Gonçalo do Amarante, Ceará (CE), the species was recorded 77 km to the west, raising questions about its extent of occurrence. Assuming the species distribution was broad but under-sampled along the coastal basins of CE, I sought a sampling optimization strategy based on Ecological Niche Models. To address the scarcity of occurrences (n=6), and based on phylogenetic niche conservation, I included phylogenetically closer species in the initial models. I determined the phylogenetic relationships of A. cearensis as sister to A. vieirai from the Cerrado, and in a clade with A. urophthalmus (Amazon) and A. bahianus (Atlantic Forest). Two expeditions were conducted based on this initial model, resulting in new records that fed back into the model with each collection. As a result, the distribution area expanded from three to nine occurrences, and from three to seven hydrographic basins. Specimen identity was confirmed by genetic distance using mitochondrial markers. I also created a final model using only A. cearensis and evaluated potential loss of climatic suitability in the future considering three climate change scenarios. Being originally adapted to humid forests, its occurrence seems limited to the coastal area of CE, a region with a more humid and milder climate. Depending on these environments makes the species more vulnerable to climate change, as projections indicate a loss of climatic suitability with warming by 2100. Threats to the species such as stream damming, pollution, and introduced species like Betta splendens Regan 1910 and Heros sp. were also identified. Considering these impacts, new records, including three conservation units, and using IUCN criteria, I recommend reclassification of the threat status to 'endangered'.