Unraveling the taxonomic knot of the monospecific Manihot anomala complex through an integrative systematic approach

Manihot stands out as a genus with notable variation in leaf morphology, a characteristic evidenced by the emergence of several complexes composed of a single species containing distinct morphotypes, many of which are treated at subspecies level. It is known that the environment can play an elementary role in the phenotypic expression of plants, without necessarily representing the presence of independent taxonomic entities. Hence, this work aimed to review the monospecific Manihot anomala complex through an integrative approach that involved leaf morphometry, descriptive taxonomy, and ecological analysis. Manihot anomala subsp. cuiabensis, M. anomala subsp. glabrata, M. anomala subsp. pavoniana and M. anomala subsp. pubescens, as well as Manihot warmingii, are here synonymized under M. anomala subsp. anomala after overlapping diagnostic characters and geographic distribution were found. Two leaf morphotypes stood out in the complex, separated from each other by the main lobe base width, as well as their apex shape, pubescence, petiole length and base angle, but these could not be elevated to species category due to the clear overlap between them. Among the three tested environmental attributes, precipitation was the most relevant, with significance values for six of 12 morphological characters. A treatment for M. anomala is provided at the end, containing descriptive analysis, taxonomic decisions, and occurrence update, in addition to four lectotypifications. The present work helps to resolve the status of M. anomala, whilst providing tools for future studies involving both Manihot and other plant groups known for their high plasticity, especially foliar.