Restricted distribution

In allopatric systems, where gene flow is highly constrained, the distinction between intraspecific differentiation and
speciation is a challenging task. Pilosocereus jauruensis is a columnar cactus restricted to patchy dry habitats of Pantanal,
Cerrado, and Chaco biomes in south-western Brazil and neighbouring countries. This species was recently reinstated after
having been synonymized with P. machriisi, now including P. paraguayensis, P. saudadensis, and P. densivillosus as its
synonyms. These taxa have been placed within the informal AURISETUS group. The present study aimed to investigate the
genetic structure of P. jauruensis in order to identify possible distinct evolutionary lineages, and to support further
refinement of the taxonomy of this species. For this purpose, 10 microsatellite loci were genotyped for 156 individuals of
P. jauruensis. To provide a proxy for the expected interspecific differentiation level within this allopatric system, two
populations (49 individuals) of P. vilaboensis (a species closely related to P. jauruensis) were also included. Additionally,
two cpDNA markers (trnSGCU-trnGUCC and trnT-trnL) for a subsample of 44 individuals of both species were
sequenced. The results obtained showed that even though P. jauruensis populations are relatively small and isolated, they
still maintain a high level of genetic diversity (e.g., HE D 0.557 to 0.725; HO D 0.253 to 0.409). The study suggests the
existence of two distinct taxa/evolutionary lineages through their entire distribution. Two populations found in the same
geographic region of the now synonymized P. densivillosus showed significant genetic divergence when compared with
other populations of P. jauruensis. In contrast, our results did not support an evolutionary independence hypothesis for
populations that occur in the same geographic region of the synonymous P. saudadensis