Using citizen science to test for acoustic niche partitioning in frogs

Slade Allen-Ankins,Lin Schwarzkopf

doi:10.1038/s41598-022-06396-0

Abstract

The acoustic niche hypothesis proposes that to avoid interference with breeding signals, vocal species should evolve to partition acoustic space, minimising similarity with co-occurring signals. Tests of the acoustic niche hypothesis are typically conducted using a single assemblage, with mixed outcomes, but if the process is evolutionarily important, a pattern of reduced acoustic competition should emerge, on average, over many communities. Using a continental-scale dataset derived from audio recordings collected by citizen scientists, we show that frogs do partition acoustic space. Differences in calls were predominately caused by differences in spectral, rather than temporal, features. Specifically, the 90% frequency bandwidths of observed frog assemblages overlapped less than expected, and there was greater distance between dominant frequencies than expected. To our knowledge, this study is the first to use null models to test for acoustic niche partitioning over a large geographic scale.

Highlights

The acoustic niche hypothesis proposes that to avoid interference with breeding signals, vocal species should evolve to partition acoustic space, minimising similarity with co-occurring signals
Species are typically surrounded by many interspecific s ignals[1], which may interact acoustically, impeding the detection and localisation of conspecific s ignals[2], or may lead to signal confusion, causing inappropriate behaviours or lack of responses detrimental to fitness, including reduced mating or accidental matings with heterospecifics[3,4]
This idea has been formalised in the acoustic niche hypothesis, in which acoustic space can be viewed as a niche axis that can be partitioned to avoid negative impacts of co-occurring s ignals[8,9]

Summary

Introduction

The acoustic niche hypothesis proposes that to avoid interference with breeding signals, vocal species should evolve to partition acoustic space, minimising similarity with co-occurring signals. Species are typically surrounded by many interspecific s ignals[1], which may interact acoustically, impeding the detection and localisation of conspecific s ignals[2], or may lead to signal confusion, causing inappropriate behaviours or lack of responses detrimental to fitness, including reduced mating or accidental matings with heterospecifics[3,4] To avoid these costs, we expect that animals should employ strategies that reduce acoustic competition[5,6,7]. The ability to achieve acoustic niche partitioning through signal divergence may be limited by the strong relationship between call frequency and body s ize[28] All of this suggests that competition for acoustic space will be high in frog assemblages, assemblages with many different species, and one would expect partitioning of the acoustic space. If frogs were partitioning acoustic space, we expected lower acoustic similarity among species calls in observed assemblages when compared to random assemblages

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