Marlon C. Machado

Interglacial microrefugia and diversification of a cactus species complex: phylogeography and palaeodistributional reconstructions for Pilosocereus aurisetus and allies

The role of Pleistocene climate changes in promoting evolutionary diversification in global biota is well documented, but the great majority of data regarding this subject come from North America and Europe, which were greatly affected by glaciation. The effects of Pleistocene changes on cold‐ and/or dry‐adapted species in tropical areas where glaciers were not present remain sparsely investigated. Many such species are restricted to small areas surrounded by unfavourable habitats, which may represent potential interglacial microrefugia. Here, we analysed the phylogeographic structure and diversification history of seven cactus species in the Pilosocereus aurisetus complex that are restricted to rocky areas with high diversity and endemism within the Neotropical savannas of eastern South America. We combined palaeodistributional estimates with standard phylogeographic approaches based on two chloroplast DNA regions (trnT‐trnL and trnS‐trnG), exon 1 of the nuclear gene PhyC and 10 nuclear microsatellite loci. Our analyses revealed a phylogeographic history marked by multiple levels of distributional fragmentation, isolation leading to allopatric differentiation and secondary contact among divergent lineages within the complex. Diversification and demographic events appear to have been affected by the Quaternary climatic cycles as a result of isolation in multiple patches of xerophytic vegetation. These small patches presently harbouring P. aurisetus populations seem to operate as microrefugia, both at present and during Pleistocene interglacial periods; the role of such microrefugia should be explored and analysed in greater detail.

Spirotheca elegans (Malvaceae: Bombacoideae), a New Species from Bahia, Brazil

Abstract Spirotheca elegans , a new species of Malvaceae subfamily Bombacoideae from the state of Bahia, Brazil, is described and illustrated. It is considered to be endemic to an area of Caatinga vegetation bordering the Chapada Diamantina mountain range, in the central region of the state. Notes on its distribution, ecology, phenology, and comments on its conservation status are given. Furthermore, a discussion of the relationship of the new taxon to other species of Spirotheca and an updated key are provided.

Capanemia Barb. Rodr. (Orchidaceae: Oncidiinae), a new record from Bahia state, Brazil

Capanemia Barb. Rodr. is recorded for the first time from Bahia state. The presence of two species broadens the known area of occurrence of the genus, establishing a new setentrional distribution limit.

Chromosome numbers in Brazilian Melocactus (Cactaceae)

Summary: The genus Melocactus has c.35 species distributed in Central and South America, the centre of diversity of the genus being the Brazilian state of Bahia, where 14 species occur. Here 11 are endemic, 5 of which are classified as Critically Endangered. In this work chromosome counts are recorded for 11 species: Melocactus bahiensis (subsp. amethystinus), M. conoideus, M. ernestii (subsp. ernestii, subsp. ernestii f. erythracanthus and subsp. ernestii f. azulensis), M. oreas (subsp. cremnophilus and subsp. oreas), M. concinnus, M. glaucescens, M. salvadorensis, M. violaceus (subsp. margaritaceus), M. zehntneri, M. xalbicephalus (a naturally occurring hybrid between M. ernestii subsp. ernestii and M. glaucescens) and M. paucispinus. M. violaceus subsp. margaritaceus presented 2n = 22, M. ernestii and M. zehntneri both had cytotypes with 2n = 22 and 2n = 44, and the remaining species had 2n = 44. The interspecific hybridization observed in the genus is discussed in relation to its reproductive biology and cytogenetic data.

A new subspecies of Tacinga inamoena (Cactaceae) from eastern Bahia, Brazil

Summary: A new subspecies of Tacinga inamoena, T. inamoena subsp. subcylindrica M. Machado & N. P. Taylor, is described. The new subspecies differs from the typical subspecies in its erect habit, by its oblong stem-segments and by being smaller in all its parts.

Extreme population subdivision or cryptic speciation in the cactus Pilosocereus jauruensis? A taxonomic challenge posed by a naturally fragmented system

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 = 0.557 to 0.725; HO = 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.