Abstract
Phenotypic traits, such as the frog advertisement call, are generally correlated with interspecific genetic variation, and, as a consequence of strong sexual selection, these behaviors may carry a phylogenetic signal. However, variation in acoustic traits is not always correlated with genetic differences between populations (intraspecific variation); phenotypic plasticity and environmental variables may explain part of such variation. For example, local processes can affect acoustic properties in different lineages due to differences in physical structure, climatic conditions, and biotic interactions, particularly when populations are isolated. However, acoustic traits can be used to test phylogenetic hypotheses. We analyzed the advertisement calls of Dendropsophus elegans males from 18 sites and compared them with those of four closely related congeneric species, in order to test for differences between inter and intraspecific variation. We analyzed 451 calls of 45 males of these five species. Because males from distant sites were grouped together without population congruence, differences found in advertisement calls among individuals were not correlated with phylogeographical clades. Phylogenetic and cluster analyses of the D. elegans clades and those of closely related species grouped all five species into the same topology, as reported by previous molecular and morphological phylogenies. However, the topology of the D. elegans phylogeographical clades did not match the topology previously reported. Acoustic communication in D. elegans seems to be conserved among populations, and the phylogeographical history of the species does not explain the variation among lineages in call properties, despite some congruent phylogenetic signals evident at the species level. Based on molecular clocks retrieved from the literature, it seems that more than 6.5 million years of divergence (late Miocene) are necessary to allow significant changes to occur in the acoustic properties of these treefrog calls, making it possible to recover their phylogenetic history only based on acoustic evidence.
Highlights
Acoustic communication is crucial during the anuran life cycle, and is used by males of many species for mate attraction, territory defense, and predator avoidance [1, 2]
The advertisement call of D. elegans was composed of two notes that were separated by a short interval, which varied from 12 to 43 ms (n = 37)
The use of acoustic traits has been avoided in amphibian systematics, mainly because acoustic traits consist of several continuous characters and a few discrete ones, and because there is an assumption that calls could substantially be influenced by extrinsic factors such as environmental and social conditions
Summary
Acoustic communication is crucial during the anuran life cycle, and is used by males of many species for mate attraction, territory defense, and predator avoidance [1, 2]. It contains phylogenetic information that may be useful in evolutionary studies Such phylogenetic signals are generally detected when comparing closely related species, or higher taxa, of the same clade [7,8,9]. Previous studies have shown that geographical variation in advertisement calls could result in divergence and consequent speciation [13,14,15] In this context, as for any species with populations that are limited by geographical barriers, the variation in acoustic properties of different populations may be strongly influenced by genetic features [16]. The fact that most anurans do not disperse over long distances [17,18,19] supports this hypothesis
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