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