Reexamining Phylloscopus trochiloides complex as a ring species: a refugial counter‐hypothesis

Abstract

The idea of ring species has been viewed as a demonstration of the potential for species‐level differentiation produced by isolation by distance in otherwise continuous populations. Although the concept is attractive, the list of empirical examples has narrowed significantly as detailed studies have been carried out. One of the few examples still cited among birds is the warbler species complex Phylloscopus trochiloides, which comprises P. trochiloides sensu stricto, P. plumbeitarsus, and P. nitidus. The ring comprises a series of populations surrounding the Tibetan Plateau in which a species‐level break is apparent at the north end of the ring. Although recent theoretical treatments have indicated that such differentiation is possible in theory, recent genomic analyses indicated multiple differentiated populations around the ring unlikely to have resulted from isolation by distance. Here, we complement the genomic studies to date with paleodistributional projections of ecological niche models that provide further evidence for multiple, isolated refugia around the ring during and since the Late Pleistocene. As such, this group should not be interpreted as exemplifying an isolation‐by‐distance mechanism of speciation, and should no longer be considered as a ring species: genomic and geographic evidence coincide in indicating that its differentiation took place in allopatry.

Spatial variability in species' potential distributions during the Last Glacial Maximum under different Global Circulation Models: Relevance in evolutionary biology

“…To assess variability in projected past distributions likely attributed to the use of different GCMs, we used estimates from three scenarios: the Community Climate System Model (CCSM; Collins et al, 2006), the Model for Interdisciplinary Research on Climate (MIROC; Hasumi & Emori, 2004), and the Max-Planck-Institute für Meteorologie model (MPI; Giorgetta et al, 2013). We focused on these GCMs as they have been widely used in current literature (Peterson & Anamza, 2017;Schidelko, Wüstenhagen, Stiels, van den Elzen, & Rödder, 2013) and because our main goal was to illustrate the difference due to the idiosyncrasies of each GCM, which should apply to any pair of available GCMs. We used four bioclimatic variables that have proven to be ecologically informative for mammals (Guevara, Gerstner, et al, 2018): BIO 05 (max.…”

Avian SDMs: current state, challenges, and opportunities

“…For example, it is possible to test whether past potential distributions correspond to the contemporary distribution of phylogroups (Peterson and Nyári 2007). In a recent example, Peterson and Anamza (2017) hindcasted SDMs to test the ring species concept in the greenish warbler Phylloscopus trochiloides. Their SDM hindcast provided further evidence for multiple, isolated refugia around the ring during and since the Late Pleistocene, leading to the conclusion that this warbler should no longer be considered as a ring species as both genomic and geographic evidence coincide in indicating that its differentiation took place in allopatry.…”

Modeling Avian Distributions and Niches: Insights into Invasions and Speciation in Birds

“…An analysis of potential Pleistocene refugial areas for members of the thrush-like Schiffornis complex revealed broad congruence with current phylogroups identified by molecular methods (Peterson and Nyári 2007). Recently, SDMs were also applied to test the ring-species concept in Greenish Warblers Phylloscopus trochiloides (Peterson and Anamza 2017). The range of this species forms a ring around the Tibetan plateau, but the existence of Pleistocene refugia revealed by paleodistribution models questions the validity of the ring-species concept (Peterson and Anamza 2017).…”

“…Recently, SDMs were also applied to test the ring-species concept in Greenish Warblers Phylloscopus trochiloides (Peterson and Anamza 2017). The range of this species forms a ring around the Tibetan plateau, but the existence of Pleistocene refugia revealed by paleodistribution models questions the validity of the ring-species concept (Peterson and Anamza 2017). Hypotheses on former refugia can also be addressed by multispecies approach.…”