Filogeografia, ecologia e parasitologia de Bothrops erythromelas (Amaral, 1923) (Squamata: Viperidae) : serpente endêmica da Caatinga

Abstract

The Neotropical region encompasses the Amazon Forest (AM) and the Atlantic Forest (AF), both renowned for their high levels of endemism and rich biodiversity. These biomes are separated by a dry forest corridor known as the Dry Diagonal (DD), which traverses Brazilian territory in a northeast-southwest orientation. The Dry Diagonal is characterized by a semi-arid climate, reduced vegetation density, and is formed by the Chaco, Cerrado, and Caatinga biomes. A Caatinga is characterized as the largest of the Seasonally Dry Tropical Forests (SDTFs) and one of the major biodiversity hotspots in South America. This region is characterized by dry deciduous tropical forests, open rocky areas, and interfaces with humid tropical forests. The low availability of water and the high diversity of soils characterize the Caatinga, a biome that nonetheless hosts a rich diversity of flora and fauna, including numerous endemic groups and species. Bothrops erythromelas, also known as Jararaca-da-Caatinga, is one of the smallest snakes in its genus, measuring around 54 cm. It has a wide distribution across the Caatinga, including states like Alagoas, Bahia, Ceará, Paraíba, Pernambuco, Piauí, Rio Grande do Norte, and Sergipe. Additionally, it is notably recognized in medicine and pharmacology. This study integrates taxonomy, evolution, ecology, and parasitism of Bothrops erythromelas. We analyze a dataset of mitochondrial DNA (COI and CytB) with the aim of identifying the historical and contemporary processes influencing landscape evolution and species diversification, as well as assessing its geographic distribution limits. We used samples from six Brazilian states (Bahia, Ceará, Paraíba, Pernambuco, Piauí, and Rio Grande do Norte) for molecular analyses, and samples from seven Brazilian states (Alagoas, Bahia, Ceará, Paraíba, Pernambuco, Rio Grande do Norte, and Sergipe) for morphological analyses, in which the occurrence of Bothrops cf. erythromelas was observed. Our sampling includes a total of 112 mtDNA gene sequences, of which 89 belong to B. cf. erythromelas, 20 sequences are from the sister species Bothrops lutzi, and three sequences are used as an outgroup group (B. jararaca, B. diporus, and B. pubescens). We conducted the construction of a dated concatenated genetic tree with posterior probability, haplotype network analysis, tests of population structure, spatial- temporal inference of geographic origin (RRW), as well as assessments of climatic suitability areas and niche overlap for Bothrops erythromelas. The study also resulted in the description of a new snake species within the studied genus, with findings indicating a separation between Bothrops sp. nov. and B. erythromelas based on mitochondrial genes (COI and CytB) and morphology. The differentiation is evidenced by at least ten discrete variables, with low overlap (1.5%) of characters, and further supported by a genetic distance of 2.5% for COI and 1.6% for CytB. A total of 247 individuals were studied, including 107 specimens (63 females and 44 males) for diet description, 200 specimens (116 females and 84 males) for sexual dimorphism analysis, 225 specimens (124 females and 101 males) for recruitment and reproductive studies, and 112 specimens (69 females and 43 males) for other related assessments. The collected data are crucial for understanding the biological and ecological aspects, serving as essential tools to develop strategies aimed at the conservation of the species. Finally, we analyzed the gastrointestinal tract of 127 specimens and found that 76 individuals were infected with at least one endoparasite, representing 17 helminth taxa: two Acanthocephala, three Cestoda, and 12 Nematoda. These findings hold significant importance in advancing the understanding of Brazilian biodiversity, addressing existing gaps in knowledge. This is particularly noteworthy as it represents a pioneering study on the helminth fauna of B. erythromelas, in which the occurrence of the species Physaloptera lutzi and Parapharyngodon hispidus is described for the first time in snakes.