Atypical distyly in Psychotria goyazensis Mull. Arg. (Rubiaceae), an intramorph self-compatible species

Abstract

Distyly is a genetically controlled floral dimorphism, characterized by the reciprocal positioning of pin and thrum morphs, a heteromorphic incompatibility system and a balanced morph ratio (isoplethy). This study aimed to investigate the phenology, features of distyly, reproductive biology, and floral visitors of Psychotria goyazensis Mull. Arg. (Rubiaceae), an intramorph self-compatible species, in a tropical semideciduous forest in the municipality of Catalão, located in the state of Goiás, Brazil. The phenology was recorded for a sample of individuals, the floral morphology being described using fresh and fixed material. The incompatibility system was tested using controlled hand pollinations. Floral visitors were collected and identified. Blooming began in November 2009 and ended in April 2010. Fruits developed from December 2009 to March 2010. The population presented atypical distyly, because only plants with pin flowers were found. The intramorph and open pollinations set more fruits than did spontaneous self-pollinations. The main flower visitors were Systropus sp. (Diptera), as well as Hymenoptera and Lepidoptera species. Morphological variations in distyly can occur by breakdown/permutation of the gene that controls the polymorphism. However, some authors argue that, in Rubiaceae, genetic control of the incompatibility system can operate independently of the morphological factor, and species might respond in different ways to the same selective pressures.

Keywords

• heterostyly
• monomorphism
• cerrado
• reproductive biology