Variação morfológica e comportamento reprodutivo em Pagamea coriacea sensu lato, uma Rubiaceae endêmica de campinarana

Abstract

Few studies have investigated the differences between closely related taxa by comparing intraspecific and interspecific variation in the population. The aim of this study was to test if there are two discrete entities within the species-complex Pagamea coriacea using morphological and ecological evidence in a local context in Presidente Figueredo, Central Amazon, Brazil. A total of 147 individuals of P. coriacea s.l. were sampled for morphological, ecological and phonological data in three nearby sites. Morphometric analyses of flowers, inflorescences and leaves separated individuals in two distinct and non-overlapping clusters. Flowers of both were dimorphic: pistillate flowers with long pistil and sterile stamens and staminate flowers with well-developed stamens and reduced pistils. All pistillate plants produced fruits, on the other hand, 36% of the staminate plants for morphotype B and only 5% of morphotype A also produced fruits, although in lower quantities than pistillate plants. However, we found one individual with hermaphrodite homostylous flowers. There was overlap in flowering and fruiting between both, but the pattern of floral maturation differed: in morphotype B flowers matured continuously, while in morphotype A flowers matured more or less at once. In relation to habitat variation, morphotype B appeared associated with shallow soils overlaying a sandstone bedrock, while morphotype A was prevalent in deeper soils. All the morphological and ecological differences found for two groups in P. coriacea complex that coexist in sympatry indicate that they correspond to distinct species.