Folk perception of sexual dimorphism, sex ratio, and spatial repartition: implications for population dynamics of Sclerocarya birrea [(A. Rich) Hochst] populations in Benin, West Africa

Abstract

In Sub-Saharan Africa, indigenous fruit trees play vital roles in nutrition and food security particularly, in food shortage times. Sclerocarya birrea subsp. birrea, an indigenous dioecious fruit tree is such a resource with strong multipurpose use characteristics in semi-arid zones of West Africa. We assessed sex ratio, spatial distribution among male and female adult trees using second-order spatial statistics and assessed folk perception of dioecism among the natural populations in protected areas and surrounding agroforestry systems. A field survey showed that 55% of interviewees were aware of sex separation in the species. Some used bark appearance to make distinction between sexes, but this morphological criterion was not consistent with statistical results. The sex ratio did not deviate significantly from 0.5 in any of the districts or land use types. Bivariate spatial analysis with pair correlation function revealed no spatial association between male and female individuals. Moreover, a strict spatial segregation of sexes was not observed even though some individuals of the same sex could sometimes be found together. Results confirmed the functional dioecy of the species and showed that the species did not display any apparent sex-specific dimorphism outside the reproduction period or any apparent sex-specific requirement for environment conditions.

Productivity characteristics and development strategies of <i>Sclerocarya birrea</i> in Burkina Faso

“…Field observations of hermaphrodite flowers and fruit on rare male plants, corroborated the allegation of some farmers that male plants produced rare fruits in some seasons. Gouwakinnou et al (2011) also noted that male plants of hermaphrodite flowers bore fruits. This study has specifically shown that there exist hermaphrodite plants that bear a few male flowers.…”

Mating System among Provenances of Sclerocarya birrea (A. Rich.) Hochst.

“…The development of fruits and viable seed through selfing treatment is an indication of hermaphrodite flowers with functional male and female organs on the same flower [15]. Even though S. birrea is generally described as dioecious tree species reports have indicated the existence of isolated cases of monoecy within the species [11,33].…”

“…Where there were more trees flowering, the tendency is towards unity. Nevertheless, a greater number of studies in dioecious plants have attributed sex biasness to sex-differentiated mortality to stressful habitats [22] with female's plants investing more in reproductive activities and less in growth and maintenance compared to male [15].…”

“…Furthermore, reports in subspecies birrea in Kenya [14] indicated a few female flowers having some pollen-bearing anthers but self-pollination studies were not conducted to confirm whether these suspected hermaphrodites' flowers were self-compatible or not. In addition, Gouwakinnou et al [15] also reported some individuals of male trees in an agroforestry system producing functionally hermaphroditic flowers with few fruits yet the flowers were different from those of female trees. The development of female flowers by male trees was previously documented in S. birrea subsp.…”

“…The presence of monoecy, occurrence of bisexual flowers in males, and sound pollen-bearing anthers in females of S. birrea [12,14] suggest the possibility of self-pollination within the species. Consequently, Gouwakinnou et al [15] recommended the need for further investigation on the breeding system of S. birrea specifically in the area of controlled pollination experiment combined with a parenthood analysis in order to ascertain the mating system of the species.…”