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Geographic variation and divergence of songs in the Olive Sparrow species complex

2020; Association of Field Ornithologists; Volume: 91; Issue: 1 Linguagem: Inglês

10.1111/jofo.12320

1557-9263

Ronald A. Fernández‐Gómez, Jorge É. Morales‐Mávil, J. Roberto Sosa‐López,

Genetic diversity and population structure

Phenotypic traits such as songs are important in species recognition. Variation in acoustic traits can form barriers to gene flow and promote speciation. Therefore, understanding song divergence is crucial in groups with controversial taxonomy such as Olive Sparrows (Arremonops rufivirgatus), a widespread Neotropical species of songbird with multiple allopatric populations. Taxonomic authorities disagree on the number of Olive Sparrow subspecies, placing them into either two or three main groups. These groups may represent separate species based on morphological traits, but trait divergence within the complex has not been examined. We studied geographic variation in the characteristics of the songs of Olive Sparrows at two geographical levels: among three proposed groups and among five allopatric populations. In a second analysis, we evaluated the strength of acoustic divergence within the complex by comparing acoustic distances among groups and allopatric populations of Olive Sparrows with the acoustic distance among three recognized species in the genus Arremonops. We analyzed 802 songs from 174 individuals across 81 locations and measured 12 variables to describe the fine structural characteristics of the songs of Olive Sparrows, Green-backed Sparrows (A. chloronotus), Black-striped Sparrows (A. conirostris), and Tocuyo Sparrows (A. tocuyensis). We found significant acoustic variation in the Olive Sparrow complex at both geographical levels. Our divergence analysis also revealed that vocal divergence within the complex is similar to or greater than that found between recognized species in the genus. Together, these results suggest that acoustic diversity within the Olive Sparrow complex probably originated by isolation in tandem with selective and/or non-selective factors. Variación geográfica y divergencia del canto del Rascador Oliváceo (Arremonops rufivirgatus) Los caracteres fenotípicos, como los cantos, son importantes para el reconocimiento de especies. La variación en caracteres acústicos puede formar barreras que previenen el flujo genético y promueven especiación. Por lo tanto, es crucial entender la divergencia en el canto en grupos en los cuales la taxonomía es controversial como en Arremonops rufivirgatus, una especie de ave canora Neotropical, ampliamente distribuida con múltiples poblaciones alopátricas. Las autoridades taxonómicas están en desacuerdo con respecto al número de subespecies de Arremonops rufivirgatus, ubicándolas en dos o tres grupos principales. Estos grupos pueden representar especies diferentes basado en caracteres morfológicos, pero la divergencia dentro del complejo no ha sido evaluada. Nosotros estudiamos la variación geográfica en las características del canto de Arremonops rufivirgatus en dos niveles geográficos: a través de los tres grupos propuestos y a través de cinco poblaciones alopátricas. En un segundo análisis, evaluamos la magnitud de la divergencia acústica dentro del complejo, comparando distancias acústicas entre los grupos y las poblaciones alopátricas de Arremonops rufivirgatus con la distancia acústica entre tres especies reconocidas en el género Arremonops. Analizamos 802 cantos de 174 individuos a través de 81 localidades y medimos 12 variables para describir las características estructurales finas de los cantos de Arremonops rufivirgatus, A. choloronotus, A. conirostris y A. tocuyensis. Nosotros encontramos variación acústica significativa en el complejo de Arremonops rufivirgatus en los dos niveles geográficos. Nuestros análisis revelaron que la divergencia local dentro del complejo es similar o mayor que la encontrada entre especies reconocidas en el género. Estos resultados sugieren que la diversidad acústica dentro del complejo de Arremonops rufivirgatus se originó probablemente por aislamiento geográfico en tándem con factores selectivos y/o no-selectivos. Table S1. Recording localities for Olive Sparrows, Green-backed Sparrows, Black-striped Sparrows, and Tocuyo Sparrows showing the source of recordings, the taxonomic group, the identity of the allopatric population (for Olive Sparrows only), and the geographic coordinates. The total number songs included in the analyses are shown. Table S2. Recordings used from libraries and private collections for the acoustic analysis of the Olive Sparrow complex and three other Arremonops species. Numbers refer to catalogue identity of each recording file in the analysis. Table S3. Results of Bonferroni post hoc test for pairwise comparisons between groups in the Olive Sparrow complex and between allopatric populations, showing the principal components with significant differences. Fig. S1. Spectrograms showing within song variation in eight individuals of the different populations. We depict exemplars for allopatric populations of Olive Sparrows (A-E) and exemplar for the three species of the Arremonops (F-H) genus used in the acoustic divergence analysis. Each row shows three songs sang for a single individual: (A) Gulf population (RON_170340, RON_170341; Chavarrillo, Emiliano Zapata, Veracruz, Mexico), (B) Pacific population (RON_170131, RON170353; Chamela, E.B., La Huerta, Jalisco, Mexico), (C) Chiapas population (RON_170259, RON_170260; Cañon del Sumidero, P.N., Tuxtla Gutiérrez, Chiapas, Mexico), (D) Central America population (ML_209299; Lomas de Barbudal, R.B., Liberia, Guanacaste, Costa Rica), (E) Peninsula population (RON_180213; MAPSA, área de recuperación; Mérida; Yucatán; Mexico), (F) Green-backed Sparrow (XC219088; Bonampack, Chiapas, Mexico), (G) Black-striped Sparrow (XC273704; Mana Dulce, Cundinamarca, Colombia), and (H) Tocuyo Sparrow (XC353183; Rioacha, La Guajira, Colombia). Intra-individual variation shows changes in the number of elements or subtle variation in bandwidth of the song o sections. Fig. S2. Spectrogram (A) and power spectrum (B) of an Olive Sparrow song generated with "frange" function in "warbleR," showing some of the acoustic variables analyzed in our study. The power spectrum shows the distribution of amplitude as an average calculated over the entire signal. The dashed line marks a threshold of 15% of the amplitude used to identify the minimum and maximum point of the signal. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.