Acoustic and micro-spatial organization of reproductive anurans aggregations from Atlantic forest: competition or confusion?

Author(s)

Lucas Rodriguez Forti

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2013-06-21

Examining board members

Jaime Aparecido Bertoluci; Rogério Pereira Bastos; Katia Maria Paschoaletto Micchi de Barros Ferraz; William Ernest Magnusson; Flávio Bertin Gandara Mendes

• Advisor: Jaime Aparecido Bertoluci

Abstract

Interspecific competition may represent a relevant force determining the distribution and abundance of organisms in nature. Natural communities composed by species that use the same resource in a similar fashion are, supposedly, structured by interspecific competition. This interactive force in the course of evolution may have led to niche differentiation among competitors in the past, and this is a relevant factor to explain the coexistence of ecologically similar species in the same habitat. Reproductive aggregations of tropical frogs are characterized by high diversity and large spatial species overlap, therefore they represent an excellent model to evaluate the importance of competition on local scale. In these communities the high density of breeding males of different species in calling activity could cause a masking effect on intraspecific acoustic communication. Therefore, considering the hypothesis that the acoustic environment could be shared, researchers have been evaluating, in most cases empirically, strategies employed by frogs to reduce competition for acoustic channels within the community, as the spectral separation (using different frequency bands) and spatial and/or temporal segregation. In this context, this paper studied the formation of anuran reproductive aggregations in 16 aquatic breeding sites belonging to six localities in the Atlantic Forest in the state of São Paulo, with the main objective of testing, using null models, whether niche partitioning occurs between species, considering spectral and spatial occupancy. It were recorded the advertisement calls of males from each species present in breeding sites, and their calling sites were characterized by their nature and height of the calling substrate. Tests for null models showed absence of significant patterns both on acoustic domain and the distribution on vertical gradient. Call duration did not reduce the species spectral overlap in the breeding sites and it is possible that reproductive females locate their specific males in heterospecific aggregations based on dominant frequency and not suffer with masking effect on acoustic communication. However, this is a hypothesis that should be tested within the anuran breeding aggregations in the Atlantic forest. All results support the idea that other factors, such as abiotic conditions, environmental heterogeneity and phylogenetic diversity, may be more decisive to explain the occurrence of species in the rich aggregations of breeding frogs in the Atlantic forest. (AU)

• FAPESP's process: 09/13987-2 - Acoustic and spatial niche partitioning among species of anuran communities from São Paulo Tropical Rain Forest
• Grantee: Lucas Rodriguez Forti
• Support Opportunities: Scholarships in Brazil - Doctorate