Analysis of Phenotypic Variability in Natural Populations of Cereus fernambucensis Lem. (Cactaceae).

Genetic diversity is essential for species adaptation, evolution, and conservation and is a determining factor in plants of ecological and agronomic interest, such as Cereus fernambucensis (Cactaceae). This study evaluated phenotypic variability and the relative importance of morphophysiological traits in two natural populations of the species located in restinga areas in Paraíba, Brazil. Twenty subpopulations were analyzed in a completely randomized design with four replicates and 15 traits. Genetic divergence was estimated by the Mahalanobis distance and grouped via the Tocher method, whereas the relative contribution of the characters was determined via the Singh method, which is associated with a selection index to identify promising genotypes. The results indicated the formation of nine distinct groups, with the mean germination time and germination speed index being the most relevant variables for differentiation. Subpopulations 4 and 13 (area I) and 15, 16, 17, and 18 (area II) stood out as strategic genetic reservoirs for conservation and improvement. Thus, this study reinforces the importance of maintaining the genetic diversity of C. fernambucensis, especially in the face of habitat fragmentation, ensuring evolutionary resilience, enriching germplasm banks, and supporting programs for the sustainable use and valorization of the genetic resources of columnar cacti in coastal ecosystems.