Contrasting bee pollination in two co-occurring distylic species of Cordia (Cordiaceae, Boraginales) in the Brazilian semi-arid Caatinga: generalist in C. globosa vs. specialist in C. leucocephala

Isabel C Machado,Marlies Sazima,Ariadna V Lopes

doi:10.1590/s0001-37652010000400010

Abstract

In this study we compare the reproductive biology of Cordia globosa and C. leucocephala (Cordiaceae, Boraginales; formerly referred to Boraginaceae) to understand the functioning of the floral morphs and the relations with their effective pollinators. The species are synchronopatric, distylic, and self-incompatible. Though they share melittophilous traits, the main visitor and pollinator of C. globosa was the generalist and exotic bee Apis mellifera, while the only one of C. leucocephala was the oligoletic bee Ceblurgus longipalpis. These two latter species are restricted to the Caatinga of NE Brazil, contrasting with the wide distribution of Cordia globosa. While the fruit-set for C. globosa was high, independently if the pollen donor/stigma receptor was a pin (long-styled) or thrum (short-styled) individual, in C. leucocephala the fruit-set was low and occurred only when a thrum individual was the pollen donor. This raises the possibility of this species moving towards dioecy. The high natural fruit-set of C. globosa confirms the generalist bee as its effective pollinator. The low fruit-set after manual crosses in C. leucocephala may be due to low pollen viability. Additionally, the low natural fruit-set (two times lower than after crosses) may be related with the foraging behavior of the specialist pollinator.

Highlights

Many species in the Boraginaceae are known to have heteromorphic self-incompatibility system
Because of the specific relations between Cordia leucocephala and Ceblurgus longipalpis, and the total lack of information about the pollinators of C. globosa, we aimed to study the floral biology and the reproductive system of these two synchronopatric species
At the main study site (Alagoinha), isolated individuals of C. globosa occurred near C. leucocephala, which grows in clumps of 3-4 individuals

Summary

Introduction

Many species in the Boraginaceae are known to have heteromorphic self-incompatibility system. Is a prominent part of the reproductive system in the genus (Opler et al 1975, Taroda and Gibbs 1986a, Boshier 1995, Machado and Loiola 2000), homostylic and functionally dioecious species are known (Bawa 1974, Opler et al 1975, Gibbs and Taroda 1983). Cordia globosa is widely distributed, occurring in Florida, the Caribbean region, and from Central America to the ISABEL C. In Brazil it is only found in the Caatinga (Taroda and Gibbs 1986a, b, Melo and Sales 2005). Cordia leucocephala is endemic to northeastern Brazil and is restricted to the Caatinga areas and sandy soils (Taroda and Gibbs 1986b, Giulietti et al 2002, Melo and Sales 2005). It has commercial potential as a grazing and ornamental species (Andrade-Lima 1989)

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