Agave × hidrocalida (Asparagaceae, Agavoideae), a new putative hybrid from Aguascalientes, Mexico

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Background and Aims: Hybridization is a common phenomenon in Agave and is considered an important component of the evolution of the genus. Recent botanical explorations in the state of Aguascalientes, Mexico, led to the discovery of populations of an Agave exhibiting morphological characters intermediate between A. angustifolia and A. filifera. The aims of this study are to describe these populations as a new nothospecies, compare it with its putative parental species and morphologically similar taxa, and document its geographic distribution. Methods: Field expeditions conducted in Aguascalientes between 2020 and 2022 resulted in the collection of a new putative hybrid of Agave. Morphological comparisons with the putative parental species and related taxa were conducted. A distribution map was generated from herbarium and field records, and the conservation status was assessed following IUCN criteria. Key results: Agave × hidrocalida is described as a new intersubgeneric nothospecies endemic to Aguascalientes, Mexico. Morphological and ecological evidence supports its origin from hybridization between A. angustifolia (subg. Agave) and A. filifera (subg. Littaea). The nothospecies exhibits characters intermediate between its putative parental species, including entire leaf margins and a raceme-like paniculate inflorescence. A preliminary conservation assessment places it in the Vulnerable (VU) category. Conclusions: Agave × hidrocalida expands the diversity of known nothospecies in Agave and provides additional evidence of the role of hybridization in the evolution of the genus. The occurrence of multiple, morphologically homogeneous populations across its distribution range warrants further studies to determine whether hybrid speciation has taken place.