Invasive alien species are currently considered one of the main threats to global biodiversity. One of the most rapidly expanding invasive plants in recent times is Kalanchoe × houghtonii (Crassulaceae), an artificial hybrid created in the 1930s in the United States by experimental crossings between K. daigremontiana and K. tubiflora, two species endemic to Madagascar. Thanks to its large colonizing capacity (mainly derived from the production of asexual plantlets), K. × houghtonii soon escaped from cultivation and quickly spread in many parts of the world. However, its actual range is not well known due to the lack of a formal description until recent times (2006) and its strong morphological resemblance with one of its parentals (K. daigremontiana). The present study was aimed, in the first instance, to delimit the present distribution area of K. × houghtonii at the global scale by gathering and validating all its occurrences and to track its colonization history. Currently, K. × houghtonii can be found on all continents except Antarctica, although it did not reach a global distribution until the 2000s. Its potential distribution, estimated with MaxEnt modelling software, is mainly centered in subtropical regions, from 20° to 40° of both northern and southern latitudes, mostly in areas with a high anthropogenic activity. Unexpectedly, concomitant to a poleward migration, future niche models suggest a considerable reduction of its range by up to one-third compared to the present, which might be related with the Crassulaceaean Acid Metabolism (CAM) of K. × houghtonii. Further research may shed light as to whether a decrease in potential habitats constitutes a general pattern for crassulaceae and CAM plants.

Challenges in the collection of vouchers, either because of the physical properties of the material (species difficult to collect or to press, e.g., palms, cycads, toxic plants, and cacti) or because drying may have a negative effect on taxonomic characters (e.g., colour), recommend the use of photographs to complement herbarium specimens. In a series of cases (enumerated in the present contribution), however, it may be impossible to collect material and, thus, photographs may be the only option to document the presence of a plant in a given locality. We propose in this paper some guidelines for the standardization of photographs intended for deposit in herbaria.

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Muchas especies del género Kalanchoe se cultivan ampliamente por su valor ornamental, hecho que junto a la alta capacidad de muchas de ellas a naturalizarse ha causado que algunas crezcan en zonas geográficas distantes de sus áreas de distribución natural. En los últimos 65 años el número de especies de Kalanchoe reportadas para Cuba ha ascendido de dos a cinco, según publicaciones recientes. La falta de un trabajo actualizado que recoja las especies naturalizadas de este género en Cuba y que aporte unas claves para su correcta identificación ha conducido a la existencia de discrepancias en cuanto a algunos de los nombres citados en estas publicaciones. A la vista de dichos precedentes creímos oportuno realizar la presente investigación que tuvo como objetivos definir el número real de especies de Kalanchoe que crecen de manera silvestre en Cuba, ofrecer una clave para su identificación, así como descripciones e información sobre las localidades donde han sido encontradas. Se estima que en Cuba crecen espontáneamente seis taxones de este género, de los que tres se reportan por primera vez, uno de los cuales, K. laetivirens, también es novedad mundial. Aportamos también imágenes y mapas que permiten una mejor comprensión de los resultados.