Polyembryony and apomixis in Cerrado Brazilian savannas: type, phylogenetic constraints, and ecological implications

Abstract

Polyembryony, characterized by the formation of multiple embryos within a single seed, and apomixis, a seed production process involving asexual embryos, are reproductive strategies that may confer adaptive advantages to plants, particularly in disturbed environments. This study evaluated the occurrence and association of these traits in the Cerrado, a megadiverse Neotropical savanna region in central Brazil. We analyzed data from the literature (125 species) and new records (91 species), counting embryos and emerging seedlings per seed to evaluate the presence and number of polyembryonic seeds. Plants were classified as monoembryonic or polyembryonic, and thresholds were established to distinguish between low and high polyembryony. Breeding systems were examined to establish the relationship between polyembryony and apomixis, and the origin of extranumerary embryos was investigated, whenever possible, using literature sources. Phylogenetic signals and evolutionary transitions for both traits were also assessed. Polyembryony was observed in one-third of the studied species (72/216), with widely variable polyembryonic seed percentages (PSPs) and percentages of seeds with extranumerary seedlings (PSES). Polyembryony ≥ 5% in PSP or PSES was a reliable indicator of apomixis, and the 31 species exceeding this limit were predominantly apomictic, mainly with sporophytic apomixis, although exceptions were noted. Despite frequent family associations, neither polyembryony nor apomixis showed a clear phylogenetic signal. These traits are common among Cerrado plants, indicating their adaptive advantage in this threatened biome. Both strategies contribute to the reproductive success of widely distributed Cerrado plants, highlighting their ecological and conservation significance.

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