Diversidade e estrutura genética de Pilosocereus jauruensis : uma cactácea restrita aos enclaves de vegetação xérica no entorno do bioma Pantanal

Abstract

Studies focusing on genetic diversity and population structure of naturally fragmented taxa are of conservation concern. Such fragmented populations are more subject to endogamy and genetic diversity erosion due to the pronounced effects of isolation and genetic drift. Pilosocereus jauruensis is a columnar cactus species restricted to patches of xeric vegetation on rock outcrops occurring around the Pantanal biome in southwestern South America. This species has been recently resurrected from synonymy with P. machriisi in the P. AURISETUS species group, and three taxa (P. paraguayensis, P. saudadensis e P. densivillosus) are synonymized with P. jauruensis in the current taxonomy. The present study aims to investigate the genetic population structure of P. jauruensis and identify possible distinct population segments within this species. We used data from four SSR markers in 157 individuals of six P. jauruensis populations and 49 individuals of two populations of P. vilaboensis, a related species occurring close to P. jauruensis populations in central Brazil. Furthermore, nucleotide variation in two plastid intergenic spacers (trnSGCU-trnGUCC and trnT-trnL) was investigated in four to five samples of each population. The indices FST e G”ST for SSR data in P. jauruensis was 0.201 and 0.559 respectively, revealing high levels of genetic differentiation among populations. Three haplotypes (Hd 0.663) of P. jauruensis with six polymorphic sites were found in the cpDNA. NJ dendograms showed similar relationships using SSR and cpDNA markers. Two populations, occurring in the same geographic region of the invalid taxa P. saudadensis were highly differentiated from other P. jauruensis populations. The cpDNA haplotype found in the northernmost P. jauruensis population was closely related with P. vilaboensis haplotypes. Also, two populations, occurring in the same geographic region of the invalid taxa P. densivillosus were highly differentiated from other P. jauruensis populations. These results were incongruent with the current taxonomic circumscription of P. jauruensis and suggest the presence of distinct taxa within this species.