Here, we present a review of the studies of evolutionary genetics (phylogenetics, population genetics, and phylogeography) using genetic data as well as genome scale assemblies in Cactaceae (Caryophyllales, Angiosperms), a major lineage of succulent plants with astonishing diversity on the American continent. To this end, we performed a literature survey (1992–2021) to obtain detailed information regarding key aspects of studies investigating cactus evolution. Specifically, we summarize the advances in the following aspects: molecular markers, species delimitation, phylogenetics, hybridization, biogeography, and genome assemblies. In brief, we observed substantial growth in the studies conducted with molecular markers in the past two decades. However, we found biases in taxonomic/geographic sampling and the use of traditional markers and statistical approaches. We discuss some methodological and social challenges for engaging the cactus community in genomic research. We also stressed the importance of integrative approaches, coalescent methods, and international collaboration to advance the understanding of cactus evolution.

The molecular phylogenies of Cactaceae have enabled us to better understand their systematics, biogeography, and diversification ages. However, most of the phylogenetic relationships within Cactaceae major groups remain unclear, largely due to the lack of an appropriate set of molecular markers to resolve its contentious relationships. Here, we explored the genome and transcriptome assemblies available for Cactaceae and identified putative orthologous regions shared among lineages of the subfamily Cactoideae. Then we developed a probe set, named Cactaceae591, targeting both coding and noncoding nuclear regions for representatives from the subfamilies Pereskioideae, Opuntioideae, and Cactoideae. We also sampled inter- and intraspecific variation to evaluate the potential of this panel to be used in phylogeographic studies. We retrieved on average of 547 orthologous regions per sample. Targeting noncoding nuclear regions showed to be crucial to resolving inter- and intraspecific relationships. Cactaceae591 covers 13 orthologous genes shared with the Angiosperms353 kit and two plastid regions largely used in Cactaceae studies, enabling the phylogenies generated by our panel to be integrated with angiosperm and Cactaceae phylogenies, using these sequences. We highlighted the importance of using coalescent-based species tree approaches on the Cactaceae591 dataset to infer accurate phylogenetic trees in the presence of extensive incomplete lineage sorting in this family.

A total of twenty-one taxa of Cactaceae, including hybrids, are newly recognised or reevaluated for the area defined for the Cacti of Eastern Brazil, some being described for the first time. Other taxonomic changes are noted together with various range extensions and many of the plants concerned are illustrated.

Background and Aims: Understanding how plant traits mediate adaptation and diversification across contrasting environments remains a major challenge in evolutionary ecology. This gap is especially evident in the Neotropics, where savannahs and seasonally dry tropical forests (SDTFs), represented here by the Cerrado and Caatinga phytogeographic domains, differ markedly in climate and ecological filters, yet remain under-represented in trait-based evolutionary studies. Here we investigated the evolutionary history of Discocactus (Cactaceae) to identify which morphological characters are associated with species occurrence across these contrasting biomes and to place these patterns within a phylogenetic and temporal framework. Methods: We generated a time-calibrated phylogenomic hypothesis for Discocactus using the Cactaceae591 probe set and integrated predictive machine learning, ancestral state reconstruction and phylogenetic comparative analyses to identify morphological characters associated with species occurrence in the savannah and SDTF biomes. Key Results: We recovered the first dated phylogeny for Discocactus, providing evidence for the recognition of 16 distinct species, including the reinstatement of D. boomianus. Divergence-time analyses indicate that the genus originated in the Pliocene and diversified rapidly during the Plio–Pleistocene transition, particularly within a major savannah-associated clade. Across analyses, flower length and stem diameter emerged as the main morphological characters associated with biome occupancy. Both characters also showed significant associations with climatic variation in phylogenetically informed regression analyses, with SDTF species tending to have shorter flowers and smaller stems than savannah species. Conclusions: Our results provide a robust phylogenomic framework for interpreting diversification in Discocactus and show that morphological differentiation within the genus is associated with ecological contrasts between Neotropical SDTF and savannah biomes. By integrating phylogenomics, predictive modelling and phylogenetic comparative methods, this study highlights how genomic and trait-based approaches can help explain character evolution and diversification across contrasting environments.