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.

AimTo investigate how the potential bias from isolation by distance (IBD) in inferences of population structure has been addressed, in studies aiming biodiversity conservation.LocationGlobal.MethodsWe reviewed the literature on the impact of IBD on the performance of the widely used software structure. We also performed a literature survey in the Web of Knowledge to assess how data have been analysed in biodiversity conservation studies when IBD is detected.ResultsBy reviewing the literature on structure performance in IBD data sets, we found a high number of studies showing that structure outputs are extremely affected by IBD. This misleading inference results principally in the detection of artificial genetic clusters. The literature survey showed that IBD was present in most data sets (60.56%) and that a substantial number of the articles only tested IBD by Mantel tests (82.21%). The most concerning result is that several articles have been using structure even after detecting IBD (57.99%), and a substantial number of them are drawing formal conservation strategies, notwithstanding the potentially biased results (51.49%).Main conclusionsOur results are of great concern, as conservation strategies may be distinct under different population structure, and its success can be affected by the incorrect identification of populations. We recommend possible stages to be considered in the presence of IBD, which can help conservation investigators before the proposition of explicit conservation strategies.

Aim: Climatic oscillations have been suggested to promote speciation and changes in species distributions, mostly in connection with the Last Glacial Maximum (LGM).However, the LGM is just the most recent of the 20+ glacial-interglacial periods that characterise the Quaternary. Here, we investigate the role of climatic changes and geomorphological features in shaping the evolution, distribution and population dynamics of the South American cactus Cereus hildmannianus.Location: South-eastern South America. Methods:We built a large fossil-calibrated phylogeny for cacti (family Cactaceae), comprising 128 species distributed in all subfamilies, using a Bayesian relaxed clock.We used the results to derive a secondary calibration for a population-level phylogeny in C. hildmannianus. We amplified two plastid (trnQ-5 0 rps16 and psbJ-petA) and one nuclear marker (PhyC) for 24 populations. We estimated population dynamics, ancestral areas, and species distribution models to infer the clade's evolutionary history in time and space.Results: Our results show a major population divergence of C. hildmannianus at c. 2.60Ma, which is strikingly coincident with the transition of the Pliocene-Pleistocene and onset of Quaternary glaciations. This was followed by a complex phylogeographic scenario involving population expansions across ecologically diverse regions.Main conclusions: Contrary to the dominant research focus on the LGM, our study indicates a major impact of the first Quaternary glaciation on the distribution and population divergence of a South American plant species. Further intraspecific events seem related to successive climatic changes and geomorphology, including the development of the coastal plain and its peculiar diversity. We propose that the first Quaternary glaciation acted as a major evolutionary bottleneck, whereby many warm-adapted lineages succumbed, while those that survived could diversify and better cope with subsequent climatic oscillations.

Aim  The aim of this study was to assess the causal mechanisms underlying populational subdivision in Drosophila gouveai, a cactophilic species associated with xeric vegetation enclaves in eastern Brazil. A secondary aim was to investigate the genetic effects of Pleistocene climatic fluctuations on these environments. Location  Dry vegetation enclaves within the limits of the Cerrado domain in eastern Brazil. Methods  We determined the mitochondrial DNA haplotypes of 55 individuals (representing 12 populations) based on sequence data of a 483‐bp fragment from the cytochrome c oxidase subunit II (COII) gene. Phylogenetic and coalescent analyses were used to test for the occurrence of demographic events and to infer the time of divergence amongst genetically independent groups. Results  Our analyses revealed the existence of two divergent subclades (G1 and G2) plus an introgressed clade restricted to the southernmost range of D. gouveai. Subclades G1 and G2 displayed genetic footprints of range expansion and segregated geographical distributions in south‐eastern and some central highland regions, east and west of the Paraná River valley. Molecular dating indicated that the main demographic and diversification events occurred in the late to middle Pleistocene. Main conclusions  The phylogeographical and genetic patterns observed for D. gouveai in this study are consistent with changes in the distribution of dry vegetation in eastern Brazil. All of the estimates obtained by molecular dating indicate that range expansion and isolation pre‐dated the Last Glacial Maximum, occurring during the late to middle Pleistocene, and were probably triggered by climatic changes during the Pleistocene. The current patchy geographical distribution and population subdivision in D. gouveai is apparently closely linked to these past events.