Evolutionary Genetics of Cacti: Research Biases, Advances and Prospects

Abstract

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.

Keywords: Cactaceae; evolutionary genetics; genomics; literature survey.

Figure 1

The number of evolutionary studies in Cactaceae, tabulated by main topics described in the text (a), and cumulative curve of major molecular markers used in the studies (b), conditioned on survey data spanning 1992–2021.

Figure 2

Distribution of evolutionary studies on the cactus backbone phylogeny (Adapted from [19] permission has been obtained).

Figure 3

Distribution of species richness within the Cactaceae family according to the dominion classification of Morrone et al. [33]. The number of studies in the main regions is shown in blue circles.

Figure 4

Network showing connections among the main topics addressed in evolutionary studies of Cactaceae. Circle sizes are proportional to the number of studies in each category (see Table S1), and line thickness is proportional to the number of connections between categories.