In a recent paper on ‘The evolution of mimicry of friarbirds by orioles (Aves: Passeriformes) in Australo-Pacific archipelagos', Jønsson et al.  use molecular phylogenies and plumage reflectance measurements to test several key predictions of the mimicry hypothesis. Jønsson et al.  show that friarbirds originated before brown orioles, and that the two groups did not co-speciate, although there is one plausible instance of co-speciation among species on the neighbouring Moluccan islands of Buru and Seram. Furthermore, Jønsson et al.  show that greater size disparity between model and mimic and a longer history of co-occurrence have resulted in a stronger plumage similarity (mimicry). One distinct outlier in this respect was the species-pair Philemon fuscicapillus and Oriolus phaeochromus. The two species have seemingly coexisted for approximately 3.7 Myr on the north Moluccan island of Halmahera. Diamond  described the species pair as ‘closely similar’ but the reflectance measurements do not show the expected high levels of plumage similarity (fig. 3 orange pin to the left). However, in a paper we had overlooked, by Besson , evidence based on museum specimens convincingly demonstrates that these two taxa do not co-occur. Rather, Philemon fuscicapillus is restricted to the island of Morotai, whereas Oriolus phaeochromus is restricted to the island of Halmahera. In light of this, we have re-analysed the data. As expected, the analyses show similar but stronger correlations between plumage similarity and coexistence time (phylogenetic regression; effect = −2.88, s.e. = 0.95, t = −3.04, p = 0.011, R2 = 0.4), and between plumage similarity and size differences (phylogenetic regression: effect = 25.65, s.e. = 9.71, t = 2.64, p = 0.023, R2 = 0.33) due to the removal of the outlier from fig. 3 in Jønsson et al.  (figure 1). The effect of the interaction between these two variables is, however, no longer significant (phylogenetic regression; effect = −13.05, s.e. = 17.98, t = −0.73, p = 0.48). Hence, our main conclusions that both coexistence time and size disparity between orioles and friarbirds contribute to the evolution of visual mimicry in orioles are upheld.
We declare we have no competing interests.
Fieldwork in the Moluccas was supported by a National Geographic Research and Exploration grant (no. 8853-10) and we are grateful to a number of Indonesian institutions that facilitated our fieldwork: the State Ministry of Research and Technology (RISTEK), the Ministry of Forestry, Republic of Indonesia, the Research Center for Biology, Indonesian Institute of Sciences (RCB-LIPI) and the Museum Zoologicum Bogoriense (MZB). From the MZB, we are particularly indebted to Tri Haryoko, Mohammed Irham and Sri Sulandari. K.A.J. acknowledges the Danish National Research Foundation for funding to the Center for Macroecology, Evolution and Climate (grant no. DNRF96). K.A.J. further acknowledges support from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no. PIEF-GA-2011-300924. K.D. was supported by the Australian Research Council (DECRA, DE120102323); G.S. was supported by a grant from Mark Constantine; M.I. was supported by the Swedish Research Council (grant no. 621-2014-5113) and P.E. was supported by the Swedish Research Council (grant no. 621-2013-561).
We would like to thank Ludovic Besson for pointing out the correct distribution of Philemon fuscicapillus, and thus that it does not coexist with Oriolus phaeochromus.
- © 2016 The Author(s)
Published by the Royal Society. All rights reserved.