Abstract
Although Melocactus is the second-most diverse cactus genus in Cuba, there is still no consensus regarding species circumscription. Seed morphology has not been used for classifying species in this group in Cuba, despite the taxonomically useful data obtained in some other genera of Cactaceae. In this study, seeds were evaluated for all Melocactus taxa known from Cuba, and seed morphological variability was analysed. Seed descriptions for each studied taxon (or localities) are presented here. We analysed 10 quantitative, and 19 qualitative characters in 50 seeds of 14 accessions. Seeds of the native species of Melocactus of Cuba are small to medium-sized, which place them among the smaller in the Cactoideae, and their shape is circular to broadly oval. Our results show that seven quantitative and six qualitative characters evaluated were suitable to distinguish among taxa. Such characters allowed establishing a general seed pattern for the M. matanzanus and M. curvispinus group, however, seeds in the M. harlowii group were less distinguishable using these characters. Colliculate relief characterized seeds of the M. matanzanus group with the testa border not expanded, while the M. curvispinus group seeds were identified by their ventro-apical keel. The most useful characters for species delimitation in the M. curvispinus group were seed length, and hilum-micropylar region characters. Significant characters that reveal differences within the M. harlowii group are lustre, seed relief and testa border expansion. Citation: Lemus-Barrios H., Barrios D., Garcia-Beltran J. A., Arias S. & Majure L. C. 2021: Taxonomic implications of seed morphology in Melocactus (Cactaceae) from Cuba. – Willdenowia 51: 91–113. Version of record first published online on 5 April 2021 ahead of inclusion in April 2021 issue.
Highlights
Seed morphological characters have been considered significant traits for distinguishing among all taxonomic ranks in different plant families (Arroyo-Cosultchi & al. 2006; Ocampo 2013; Ocampo & Almeda 2013; Ullah & al. 2018; Dalavi & al. 2019)
Variation in seed shape occurs within most species between circular to broadly oval, but broadly oval were exclusively found in M. guitartii, M. harlowii and the three localities of M. acunae
Testa features — Testa was black in all species, glossy in Melocactus acunae subsp. acunae (Punta de Maisí), M. borhidii, M. evae, M. harlowii, M. holguinensis and M. perezassoi, but matte occurs in the remaining eight taxa evaluated
Summary
Seed morphological characters have been considered significant traits for distinguishing among all taxonomic ranks in different plant families (Arroyo-Cosultchi & al. 2006; Ocampo 2013; Ocampo & Almeda 2013; Ullah & al. 2018; Dalavi & al. 2019). Seed morphological characters have been considered significant traits for distinguishing among all taxonomic ranks in different plant families In Cactaceae, seed morphology has been used in the recognition of taxa in different genera, e.g. Ferocactus Britton & Rose (Taylor & Clarke 1983), Pachycereus Berger) Britton & Rose (Arias & Terrazas 2004), Stenocereus In this regard, Barthlott & Hunt (2000) and Anderson (2001) considered that seed characters are not strongly influenced by the environment, which denotes strong genetic control (Barthlott 1981). The use of seed morphology for taxonomic purposes must be taken with caution, because several authors have found variation at the population level, e.g. Melocactus Link & Otto (Taylor 1991), Crepis L. 2001), Lemus-Barrios & al.: Seed morphology in Melocactus from Cuba The use of seed morphology for taxonomic purposes must be taken with caution, because several authors have found variation at the population level, e.g. Melocactus Link & Otto (Taylor 1991), Crepis L. (Imbert & al. 1997), Aeschynomene Hutch. (Zhang 1998), Anigozanthos Labill. (Tieu & al. 2001), Lemus-Barrios & al.: Seed morphology in Melocactus from Cuba
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