Genetic differentiation in the Mexican endemic Rufous-backed Robin, <br />Turdus rufopalliatus (Passeriformes: Turdidae)

Abstract

The Rufous-backed Robin (Turdus rufopalliatus) is endemic to deciduous and semideciduous tropical forests of western Mexico. Of the currently recognized subspecies, T. r. graysoni, from the Tres Marías Islands and nearby coastal Nayarit, has been considered a separate species; however, this treatment has been challenged due to an apparent contact zone on the mainland, although no hybrids have ever been recorded. Here, we use mitochondrial DNA sequences from individuals sampled across the species' range to assess their phylogeographic relationships. We found reciprocal monophyly between Tres Marías Islands and mainland populations, which share no haplotypes between them. Evolutionary divergence detected within T. rufopalliatus suggests that mainland and island populations have been isolated from each other, and divergence decreases if insular populations are excluded. Demographic parameters suggest that populations are in the process of a rapid expansion from ancestral populations with a lower population size. These results are consistent with morphometric and plumage differences that have been used to recognize the Tres Marías Islands populations from the mainland ones, thus suggesting species status of the island form.

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“…Morphometrics.-Larger in all external measurements, especially tarsus length and bill length (score 2). Montaño-Rendón et al (2015), based on 268 adult specimens from throughout the range of T. rufopalliatus (sensu lato), confirmed the existence of marked morphometric differences.…”

“…Additional information. -Montaño-Rendón et al (2015) and Ortiz-Ramírez et al (2018) found reciprocal monophyly and deep genetic divergence between graysoni and rufopalliatus.…”

“…99 and p. 206 in Pompa-Mera 2014). The islands were submerged until the Late Pliocene; they must have emerged above sea level well before the Late Pleistocene (contra Zweifel 1960, Smith et al 2011, Arbeláez-Cortés et al 2014, Montaño-Rendón et al 2015 as there are Late Pleistocene terrace deposits in the lowerlying areas of both Isla María Madre (McCloy et al 1988, Pompa-Mera et al 2013, Pompa-Mera 2014 and Isla María Cleofas (Foose 1962), and hundreds of metres of uplift must have occurred for that to be the case.…”

“…The absence of clear distinctions in plumage between some graysoni and other races (see above) makes it particularly difficult to identify potential hybrids based on plumage, and there is slight overlap in morphometrics, especially bill length of females (Grant 1965a). Montaño-Rendón et al (2015) and Ortiz-Ramírez et al (2018) apparently did not include DNA of graysoni from the mainland, nor indeed of any rufopalliatus from the Nayarit coastal plain, where hybrids, if any, would be expected (all of their Nayarit rufopalliatus were from a single locality in the foothills). Because the extent of hybridisation, if any, is presently unknown, we recommend further studies before concluding whether graysoni represents a species.…”

Aves del Alto Balsas de Guerrero: diversidad e identidad ecológica de una región prioritaria para la conservación

“…En cuanto a endemismos e identidad biológica mexicana, la riqueza de especies endémicas registrada hace del Alto Balsas un área prioritaria para la conservación a escala global (Arizmendi, 2002;Bertelli et al, 2017; Navarro-Sigüenza y Peterson, 2004;Peterson y Navarro-Sigüenza, 2000). En términos históricos, la evolución de endemismos en los bosques tropicales secos del occidente de México se explica por varios factores: el efecto de aislamiento que la Faja Volcánica Transmexicana y la sierra Madre del Sur producen sobre la cuenca del Balsas (Becerra, 2005;Morrone, 2014); el levantamiento del istmo de Tehuantepec durante el Mioceno (Mason et al, 2018;Navarro-Sigüenza et al, 2017) y los cambios paleoclimáticos derivados del avance y retroceso de glaciares del Pleistoceno (Arbeláez-Cortés, Milá et al, 2014;Arbeláez-Cortés, Roldán-Piña et al, 2014;Montaño-Rendón et al, 2015;Navarro-Sigüenza et al, 2017). En conjunto, estos procesos moldearon la distribución de los bosques templados y tropicales, generando efectos de aislamiento y contacto periódicos que elevaron las tasas de diversificación de las aves (Lovette, 2005).…”