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Stridulations reveal cryptic speciation in neotropical sympatric ants.

Ferreira RS, Poteaux C, Delabie JH, Fresneau D, Rybak F - PLoS ONE (2010)

Bottom Line: In order to understand the potential of acoustics and to improve consistency in the conclusions by comparing different approaches, phylogenetic relationships of all the morphs considered were assessed by the analysis of a fragment of the mitochondrial DNA cytochrome b.Congruent morphological, acoustic and genetic results constitute sufficient evidence to propose each morph studied here as a valid new species, suggesting that P. apicalis is a complex of at least 6 to 9 species, even if they present different levels of divergence.Finally, our results highlight that ant stridulations may be much more informative than hitherto thought, as much for ant communication as for integrative taxonomists.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire d'Ethologie Expérimentale et Comparée, LEEC EA 4443, Université Paris 13, Villetaneuse, France. ronara@leec.univ-paris13.fr

ABSTRACT
The taxonomic challenge posed by cryptic species underlines the importance of using multiple criteria in species delimitation. In the current paper we tested the use of acoustic analysis as a tool to assess the real diversity in a cryptic species complex of Neotropical ants. In order to understand the potential of acoustics and to improve consistency in the conclusions by comparing different approaches, phylogenetic relationships of all the morphs considered were assessed by the analysis of a fragment of the mitochondrial DNA cytochrome b. We observed that each of the cryptic morph studied presents a morphologically distinct stridulatory organ and that all sympatric morphs produce distinctive stridulations. This is the first evidence of such a degree of specialization in the acoustic organ and signals in ants, which suggests that stridulations may be among the cues used by these ants during inter-specific interactions. Mitochondrial DNA variation corroborated the acoustic differences observed, confirming acoustics as a helpful tool to determine cryptic species in this group of ants, and possibly in stridulating ants in general. Congruent morphological, acoustic and genetic results constitute sufficient evidence to propose each morph studied here as a valid new species, suggesting that P. apicalis is a complex of at least 6 to 9 species, even if they present different levels of divergence. Finally, our results highlight that ant stridulations may be much more informative than hitherto thought, as much for ant communication as for integrative taxonomists.

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Stridulatory signal of a Pachycondyla apicalis species complex worker.(A) Oscillogram of a series of chirps, showing the chirp duration (CD), the inter-chirp interval (ICI), the number of pulses (NP) in a chirp and the inter-pulse interval (IPI). (B) Spectrogram of a chirp, showing the dominant frequency (DM) and the quartiles of frequencies at 25, 50 and 75% of the signal energy (Q25, Q50 and Q75 respectively).
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pone-0015363-g002: Stridulatory signal of a Pachycondyla apicalis species complex worker.(A) Oscillogram of a series of chirps, showing the chirp duration (CD), the inter-chirp interval (ICI), the number of pulses (NP) in a chirp and the inter-pulse interval (IPI). (B) Spectrogram of a chirp, showing the dominant frequency (DM) and the quartiles of frequencies at 25, 50 and 75% of the signal energy (Q25, Q50 and Q75 respectively).

Mentions: Ants from the P. apicalis species complex produce stridulations which result in both airborne sound and substrate vibrations. Airborne sound presents audible and ultrasound components, and in the following we refer to the audible component only. A total of 40 workers from 5 colonies (Table 2) were recorded. All recordings were carried out in a low-noise room where the ambient temperature was kept at 25±1°C and the relative humidity at 65±10%. The recording setup consisted of an omnidirectional Sennheiser K6 microphone (frequency response: 30 to 20000 Hz±1 dB) connected to a Marantz PMD 671 digital recorder with sampling frequency at 48 kHz. We did not consider frequencies superior to 20 KHz, due to technical limitations of the microphone. Ants were held with forceps 1 cm from the microphone during recording. The following temporal parameters were analysed using the software Avisoft-SASLab Pro, version 4.40 [64]: the chirp duration, the inter-chirp interval, and for each chirp we measured the number of pulses, the pulse repetition rate, the mean inter-pulse interval as well as the inter-pulse interval in the 1st, 2nd and 3rd thirds of the chirp. The frequency parameters considered for each chirp were: the dominant frequency, the frequencies at 25, 50 and 75% of the signal energy, and the percentage of energy below 14 kHz. The maximal and minimal intra-pulse frequencies were also calculated for each individual, by the zero-crossing method [65]. For each chirp analysed, we calculated the maximal and minimal intra-pulse frequencies for 10 pulses and the mean value was computed (Figure 2). A series of ten chirps was analyzed for each ant, and the mean value was computed.


Stridulations reveal cryptic speciation in neotropical sympatric ants.

Ferreira RS, Poteaux C, Delabie JH, Fresneau D, Rybak F - PLoS ONE (2010)

Stridulatory signal of a Pachycondyla apicalis species complex worker.(A) Oscillogram of a series of chirps, showing the chirp duration (CD), the inter-chirp interval (ICI), the number of pulses (NP) in a chirp and the inter-pulse interval (IPI). (B) Spectrogram of a chirp, showing the dominant frequency (DM) and the quartiles of frequencies at 25, 50 and 75% of the signal energy (Q25, Q50 and Q75 respectively).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3008743&req=5

pone-0015363-g002: Stridulatory signal of a Pachycondyla apicalis species complex worker.(A) Oscillogram of a series of chirps, showing the chirp duration (CD), the inter-chirp interval (ICI), the number of pulses (NP) in a chirp and the inter-pulse interval (IPI). (B) Spectrogram of a chirp, showing the dominant frequency (DM) and the quartiles of frequencies at 25, 50 and 75% of the signal energy (Q25, Q50 and Q75 respectively).
Mentions: Ants from the P. apicalis species complex produce stridulations which result in both airborne sound and substrate vibrations. Airborne sound presents audible and ultrasound components, and in the following we refer to the audible component only. A total of 40 workers from 5 colonies (Table 2) were recorded. All recordings were carried out in a low-noise room where the ambient temperature was kept at 25±1°C and the relative humidity at 65±10%. The recording setup consisted of an omnidirectional Sennheiser K6 microphone (frequency response: 30 to 20000 Hz±1 dB) connected to a Marantz PMD 671 digital recorder with sampling frequency at 48 kHz. We did not consider frequencies superior to 20 KHz, due to technical limitations of the microphone. Ants were held with forceps 1 cm from the microphone during recording. The following temporal parameters were analysed using the software Avisoft-SASLab Pro, version 4.40 [64]: the chirp duration, the inter-chirp interval, and for each chirp we measured the number of pulses, the pulse repetition rate, the mean inter-pulse interval as well as the inter-pulse interval in the 1st, 2nd and 3rd thirds of the chirp. The frequency parameters considered for each chirp were: the dominant frequency, the frequencies at 25, 50 and 75% of the signal energy, and the percentage of energy below 14 kHz. The maximal and minimal intra-pulse frequencies were also calculated for each individual, by the zero-crossing method [65]. For each chirp analysed, we calculated the maximal and minimal intra-pulse frequencies for 10 pulses and the mean value was computed (Figure 2). A series of ten chirps was analyzed for each ant, and the mean value was computed.

Bottom Line: In order to understand the potential of acoustics and to improve consistency in the conclusions by comparing different approaches, phylogenetic relationships of all the morphs considered were assessed by the analysis of a fragment of the mitochondrial DNA cytochrome b.Congruent morphological, acoustic and genetic results constitute sufficient evidence to propose each morph studied here as a valid new species, suggesting that P. apicalis is a complex of at least 6 to 9 species, even if they present different levels of divergence.Finally, our results highlight that ant stridulations may be much more informative than hitherto thought, as much for ant communication as for integrative taxonomists.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire d'Ethologie Expérimentale et Comparée, LEEC EA 4443, Université Paris 13, Villetaneuse, France. ronara@leec.univ-paris13.fr

ABSTRACT
The taxonomic challenge posed by cryptic species underlines the importance of using multiple criteria in species delimitation. In the current paper we tested the use of acoustic analysis as a tool to assess the real diversity in a cryptic species complex of Neotropical ants. In order to understand the potential of acoustics and to improve consistency in the conclusions by comparing different approaches, phylogenetic relationships of all the morphs considered were assessed by the analysis of a fragment of the mitochondrial DNA cytochrome b. We observed that each of the cryptic morph studied presents a morphologically distinct stridulatory organ and that all sympatric morphs produce distinctive stridulations. This is the first evidence of such a degree of specialization in the acoustic organ and signals in ants, which suggests that stridulations may be among the cues used by these ants during inter-specific interactions. Mitochondrial DNA variation corroborated the acoustic differences observed, confirming acoustics as a helpful tool to determine cryptic species in this group of ants, and possibly in stridulating ants in general. Congruent morphological, acoustic and genetic results constitute sufficient evidence to propose each morph studied here as a valid new species, suggesting that P. apicalis is a complex of at least 6 to 9 species, even if they present different levels of divergence. Finally, our results highlight that ant stridulations may be much more informative than hitherto thought, as much for ant communication as for integrative taxonomists.

Show MeSH