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Psyche
Volume 2012 (2012), Article ID 791395, 9 pages
http://dx.doi.org/10.1155/2012/791395
Research Article

Might Heterostyly Underlie Spider Occurrence on Inflorescences? A Case Study of Palicourea rigida (Rubiaceae), a Common Shrub from Brazilian Cerrado

1Programa de Pós-Graduação em Ecologia, Instituto de Biologia, UNICAMP, Caixa Postal 6109, 13083-970 Campinas, SP, Brazil
2Unidade Universitária de Morrinhos, Universidade Estadual de Goiás, 75650-000 Morrinhos, GO, Brazil
3Laboratório de Ecologia ComportamentaL e de Interações—LECI, Instituto de Biologia, Universidade Federal de Uberlândia, CP 593, 38400-902 Uberlândia, MG, Brazil
4UNICEUB/FACES, 70790-075, Brasília, DF, Brazil
5Instituto de Ciências Naturais, Humanas e Sociais, Universidade Federal de Mato Grosso, Campus Universitário de Sinop, 78557-267 Sinop, MT, Brazil

Received 3 August 2012; Revised 15 October 2012; Accepted 16 October 2012

Academic Editor: Kleber Del-Claro

Copyright © 2012 Suzana Diniz et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We carried out a research on the Palicourea rigida (Rubiaceae) inflorescences, a distylous shrub of Brazilian Cerrado. Our objective was to compare the inflorescence architectural complexity and its quality in the two floral morphs and search for any relationship with spider occurrence. In order to assess the quality of inflorescence resources, we quantified the nectar volume and its sugar concentration and the number of fruits and flowers (intact and aborted) for both inflorescence morphs with and without spiders. For the architectural heterogeneity, we quantified floral structures and inflorescence levels of branching. Spider occurrence was higher in longistylous inflorescences than in brevistylous ones. The sampled spiders were classified into the guilds ambushers, jumpers, or orb-weavers. Ambushers, jumpers, and total richness were much higher among longistylous inflorescences. We found no difference between morphs neither in volume or nectar concentration nor in amount of fruits and flowers. However, longistylous inflorescences presented greater architectural heterogeneity than brevistylous ones. Therefore, we suggested that architectural heterogeneity is an important factor underlying the occurrence of cursorial spiders on P. rigida inflorescences, which possibly arose from the relationship between refuge availability and inflorescence architecture.