Secondary sexual dimorphism in biomass production of Ilex paraguariensis progenies associated with their provenances and morphotypes

Abstract

Summary Secondary sexual dimorphism (SSD) in flowering plants is expressed as differences in sexual characteristics that are not directly related to gamete production, involving a wide variety of morphological and physiological traits. Yerba mate (Ilex paraguariensis) is an evergreen dioecious tree native to South America. It was hypothesized that: (1) in early years, the two yerba-mate genders would segregate with lower frequency in biomass production than during later years; (2) in the case of SSD, higher biomass production would be seen for female plants when compared to male plants at a more advanced age; (3) higher SSD would appear in morphotypes that represent leaf adaptations to full sunlight cultivation; and (4) progenies originated from provenances from higher altitudes will show greater SSD in biomass production. One experiment with 135 progenies originated from six provenances with different altitudes was established in 1997 in a monoculture (under full sunlight conditions). Biomass production (leaves and thin twigs) per plant was evaluated during four harvests (1999, 2001, 2003, and 2015). The frequency of SSD in biomass production did not change throughout the plant’s life. Males were more productive than females in 1999, 2001, and 2003, while the increased frequency of more productive female plants was observed during the most recent harvest (2015), resulting in an equal frequency of female and male progenies. Sexual segregation was observed in dully green, sassafras, and gray morphotypes that are characterized by their waxy leaf structures, an adaptation to elevated irradiance and UV. As a result of adaptative responses to stressful conditions and elevated interplant variability, the relationship between SSD and biomass production of progenies originated from the highest altitudes segregated with higher frequency when compared to the lowest altitudes.