Characterizing background heterogeneity in visual communication

Author(s)

Camargo, Maria Gabriela G. ^[1] ; Cazetta, Eliana ^[2] ; Morellato, Leonor Patricia C. ^[1] ; Schaefer, H. Martin ^[3]

Affiliation

^[1] UNESP Univ Estadual Paulista, Lab Fenol, Dept Bot, Grp Fenol & Dispersao Sementes, BR-13506900 Rio Claro, SP - Brazil

^[2] Univ Estadual Santa Cruz, Dept Ciencias Biol, BR-45662900 Ilheus, BA - Brazil

^[3] Univ Freiburg, Fac Biol, Dept Evolutionary Biol & Anim Ecol, D-79104 Freiburg - Germany

• Document type: Journal article
• Source: BASIC AND APPLIED ECOLOGY; v. 15, n. 4, p. 326-335, 2014.
• Web of Science Citations: 2

Abstract

How is a visual signal effectively transmitted through an environment triggering a response by a perceiver? Experimental and theoretical works in disparate fields, such as sexual selection and plant animal interactions, have demonstrated selection based on signal conspicuousness. However, to properly describe the conspicuousness of a signal, it is necessary to quantify the spatial and temporal heterogeneity of background coloration of a signaler. We intend to compare the effectiveness of four methods developed to characterize background heterogeneity. To describe the background in a seasonal vegetation, we collected reflectance data in dry and wet seasons of (i) target leaves (those leaves against which a signal is predominantly displayed); (ii) overall leaves (leaves from the most common plant species in the community); (iii)frames in a limited area in space, by measuring the reflectance of all material found in the background; and (iv) background items from the most common species, based on their abundance along transects. We analyzed seasonal color changes in terms of hue, chroma and brightness and described the conspicuousness of fruit coloration according to avian vision. All methods found significant differences in the background coloration between seasons, with higher reflectance values in the dry season. Hue values were higher in the dry season, and chroma values were higher in the wet season. Only the methods most restricted in space (target leaves and frames) recorded seasonal differences in fruit conspicuousness. The transects and frames methods are useful for describing the backgrounds of non-stationary signals (i.e., those of most animals). For plant signals, which are displayed against a fixed background in space, we recommend specific sampling of target leaves. Our results support the importance of measuring the seasonal heterogeneity of the background but also indicate that a monthly sampling design is not necessary to evaluate the conspicuousness of fruit signals. (AU)

• FAPESP's process: 10/51307-0 - Floristic diversity and seasonal patterns of rupestrian fields and cerrado
• Grantee: Leonor Patricia Cerdeira Morellato
• Support Opportunities: Research Grants - Research Partnership for Technological Innovation - PITE
• FAPESP's process: 10/52113-5 - e-phenology: the application of new technologies to monitor plant phenology and track climate changes in the tropics
• Grantee: Leonor Patricia Cerdeira Morellato
• Support Opportunities: Research Program on Global Climate Change - Regular Grants
• FAPESP's process: 12/19827-0 - Seasonal patterns in production, chemical composition, color and fruit contrast in the Cerrado
• Grantee: Maria Gabriela Gutierrez de Camargo
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 10/01762-3 - Fruiting patterns and diversity in production, color and chemical composition of cerrado fruits: an integrated view
• Grantee: Maria Gabriela Gutierrez de Camargo
• Support Opportunities: Scholarships in Brazil - Doctorate