SHORT COMMUNICATION Sexual system of Garcinia indica Choisy: geographic variation in trioecy and sexual dimorphism in floral traits K. S. Joseph • H. N. Murthy Received: 6 September 2013 / Accepted: 1 July 2014 Ó Springer-Verlag Wien 2014 Abstract Most flowering plants are hermaphroditic with both stamens and carpels in the same flower. Other sexual systems are derived from ancestral hermaphroditism through one of the following pathways namely via mono- ecy, directly from hermaprhoditism, via gynodioecy, via distyly or via androdioecy. Sexual system in the genus Garcinia is highly diverse and includes dioecious, gyno- dioecious, androdioecious, polygamodioecious, monoe- cious and andromonoecious species. Garcinia indica Choisy (kokum tree) is reported to be polygamodioecious or gynodioecious. In the present study, sexual variation was estimated in seven populations of Garcinia indica of Western Ghats to determine the extent of variation among the populations and 14 floral traits were studied to assess the sexual dimorphism in floral traits. Four basic kinds of flowers namely, male flowers, male flowers with pistillode, female flowers with staminodes and bisexual flowers, were found in G. indica. These basic kinds of flowers occurred individually on a particular tree, producing unisexual individuals, or in combination of two, forming cosexual individuals. Thus, this species is trioecious, although the percentage of cosexual trees varied in different geograph- ical locations. All the populations included cosexuals except one whereas pure hermaphroditic trees were present only in one. Significant differences were observed in 11 out of the 14 floral traits studied in the seven populations resulting in the diversity of sex forms. Male flowers had larger petal and female flowers were in general smaller than the other kinds. Interestingly, bisexual flowers were not always intermediate in size between male and female flowers. Keywords Garcinia indica Á Paths to dioecy Á Pistillode Á Staminodes Á Trioecy Introduction Dioecy is thought to evolve from hermaphroditism through five potential pathways (Ross 1980, 1982; reviewed in Webb 1999), i.e. (1) via monoecy, (2) directly from her- maphroditism, (3) via gynodioecy, (4) via distyly and (5) via androdioecy. Two main pathways, the gynodioecious and the monoecious, are considered prevalent in the evo- lution of dioecy (Webb 1999). The gynodioecious pathway (Lloyd 1975; Ross 1982) suggests that dioecy evolved from hermaphroditic or cosexual ancestors in a two step process. In the first step, a male sterile mutation first spreads through the population, rendering some individuals female, while others remain hermaphrodite (i.e. gynodioecy; Dar- win 1877; Charlesworth and Charlesworth 1978a). In the second step, the selection acting on the pollen-producing hermaphrodites favors specialization in the male function, and hermaphrodites gradually lose their female reproduc- tive function. The monoecious pathway suggests that dioecy evolved from hermaphroditic individuals through an intermediate stage of monoecy, i.e., separate male and female flowers on the same individual (Ross 1982), which gradually specialized toward the male or female functions. Empirical evidence indicates that production of only bisexual flowers is the ancestral conditions in angiosperms (Richards 1997; Doyle 1998; Endress 2001). Hence, all the diversity in the arrangement of bisexual and unisexual flowers has repeatedly evolved from a cosexual ancestor. K. S. Joseph Á H. N. Murthy (&) Department of Botany, Karnatak University, Dharwad 580 003, India e-mail: nmurthy60@yahoo.co.in 123 Plant Syst Evol DOI 10.1007/s00606-014-1120-y