To be or not to be fragrant: floral scent of some bat-pollinated cacti.

Floral scent is a key olfactory cue in both diurnal and nocturnal pollination systems. In the case of nocturnal systems, such as bat-pollinated flowers, odour seems to play a more important role than visual cues. Cactaceae include many bat-pollinated species; however, few studies have investigated the olfactory cues in this family. We analysed and compared the chemical composition of the floral bouquet of three chiropterophilous cactus species, among which are a pair of congeners that differ considerably in scent intensity. Our research presents novel findings regarding the floral scent chemistry of chiropterophilous cactus species. We documented the first case of a bat-pollinated cactus whose flowers lack perceptible floral scent and in which no volatile compounds were detected in our chemical analyses. Additionally, we provide a comprehensive analysis of the chemical composition of the floral bouquet of the other two bat-pollinated species, revealing a resemblance among closely related species within the same genus. We highlight the need for further studies using biotests to investigate the mechanisms through which bats find flowers lacking scent.

Usefulness of cpDNA markers for phylogenetic and phylogeographic analyses of closely related cactus species.

Although plastid DNA has been widely explored as a marker of choice for phylogeny and phylogeography studies, little is known about its utility for examining relationships between closely related species. The slow evolutionary rates inherent to chloroplast (cp) DNA make it difficult to perform lower level taxonomic analyses, particularly at the population level. We characterized the nucleotide variation and investigated the utility of eight noncoding cpDNA regions in four closely related species of the Pilosocereus aurisetus group (Cactaceae), an endemic taxon of eastern South America. The plastid intergenic spacers 5'-trnS-trnG, 3'-trnS-trnG and trnT-trnL were the most variable regions and were the most useful for lower level taxonomic comparisons, especially when used together. We conclude that an adequate combination of regions alongside indels as an additional character improves the usefulness of cpDNA for phylogenetic studies.