Investigating Baraminology in an Iconic Group of Desert Plants, Family Cactaceae

Cacti (family Cactaceae) are an intriguing group of plants which thrive in arid environments such as Arizona’s Sonoran Desert. Most of the 1750 species in family Cactaceae are native to the Western Hemisphere, including 122 species reported in Arizona (USA) (Christenhusz 2016). This diverse family is home to giants such as the iconic saguaro cactus (Carnegiea gigantea) as well as the unassuming, shrub-like Barbados gooseberry (Pereskia aculeata). Whether the plants within family Cactaceae represent one, more than one, or less than one created kind has never been thoroughly investigated. Baraminology, the study of created kinds, has historically relied upon hybridization and morphological data to identify discontinuities between groups of organisms (Wood 2003). More recently, the use of molecular baraminology has sought to clarify these discontinuities between groups of organisms by comparing protein and DNA sequences (Cserhati 2023). With the growing availability of complete chloroplast genomes (cpDNA), molecular baraminology is a potentially powerful tool for resolving plant baramins. By leveraging morphological, hybridization, and molecular data we aim to use a three-pronged approach to reconstruct the baraminological history of family Cactaceae. Fifty-four species of cacti from three separate subfamilies (Cactoideae, Opuntioideae, and Pereskoideae) for which complete cpDNA sequences are available were used for this analysis. Complete cpDNA sequences (~110-160 kbp) were aligned using MAFFT, pairwise distances were calculated between species, and these distances were used to group species based on sequence similarities following previously published protocols (Cserhati 2023). Based on gross morphological analysis and hybridization data we hypothesize that the 54 cacti species represent 3 separate holobaramins. Multiple alignment of cpDNA from these 54 species clustered them into two different putative holobaramins which do not correlate with the holobaramins proposed by the morphological analysis. The conflict between the morphological and molecular analyses is due to the sequence similarities being disproportionately impacted by inversions, duplications, and deletions in cpDNA. These large-scale genetic rearrangements strongly affect the similarity scores between pairwise alignments, thereby generating spurious groupings that do not necessarily reflect baraminic relationships. This study identifies potential pitfalls in using global cpDNA analysis for baraminological comparisons and highlights important considerations to make before drawing baraminology conclusions from molecular data. References: Christenhusz, Maarten J. M., and James W. Byng. “The Number of Known Plants Species in the World and Its Annual Increase.” Phytotaxa 261, no. 3 (May 20, 2016): 201–17. Wood, Todd Charles, Kurt P. Wise, Roger Sanders, and Neal Doran. “A Refined Baramin Concept.” Baraminology Study Group (2003): 1-14. Cserhati, Matthew. "Chloroplast Genome-Based Baraminology Study of Liliales." Creation Research Society Qtr 60, no. 2 (2023): 84-96.