The effect of phylogeographic history on species boundaries: a comparative framework in Hyla tree frogs

Abstract

Because it is indicative of reproductive isolation, the amount of genetic introgression across secondary contact zones is increasingly considered in species delimitation. However, patterns of admixture at range margins can be skewed by the regional dynamics of hybrid zones. In this context, we posit an important role for phylogeographic history: hybrid zones located within glacial refugia (putatively formed during the Late-Pleistocene) should be better defined than those located in post-glacial or introduced ranges (putatively formed during the Holocene and the Anthropocene). We test this hypothesis in a speciation continuum of tree frogs from the Western Palearctic (Hyla), featuring ten identified contacts between species spanning Plio-Pleistocene to Miocene divergences. We review the rich phylogeographic literature of this group and examine the overlooked transition between H. arborea and H. molleri in Western France using a multilocus dataset. Our comparative analysis supports a trend that contacts zones resulting from post-glacial expansions and human translocations feature more extensive introgression than those established within refugial areas. Integrating the biogeographic history of incipient species, i.e. their age since first contact together with their genetic divergence, thus appears timely to draw sound evolutionary and taxonomic inferences from patterns of introgression across hybrid zones.

Revisiting a speciation classic: Comparative analyses support sharp but leaky transitions betweenBombinatoads

“…Variation in the extent of introgression between replicate transects is often interpreted as differences in the strength of reproductive isolation, in respect to genetic and ecological factors, or a combination of both (Harrison & Larson, 2016). Based on observations between cryptic tree frog taxa, Dufresnes, Berroneau, et al (2020) proposed that hybrid zones from glacial refugia could be narrower than those from post-glacial or introduced ranges, as they presumably had more time to reach a selection-dispersal equilibrium and promote pre-mating barriers via reinforcement. Genetic incompatibilities emerging independently within single species can also differentially affect the outcome of hybridization (Barnard-Kubow & Galloway, 2017).…”

“…Based on observations between cryptic tree frog taxa, Dufresnes, Berroneau, et al. (2020) proposed that hybrid zones from glacial refugia could be narrower than those from post‐glacial or introduced ranges, as they presumably had more time to reach a selection‐dispersal equilibrium and promote pre‐mating barriers via reinforcement. Genetic incompatibilities emerging independently within single species can also differentially affect the outcome of hybridization (Barnard‐Kubow & Galloway, 2017).…”

“…As such, hybrid zone analyses have become useful models for speciation (Harrison, 1993), phylogeographical (Avise, 2000) and systematic studies (Dufresnes, Pribille, et al., 2020). However, hybrid zones can expand, collapse or become isolated from parental ranges, resulting in wide admixture or narrow tension zones for the same species pair (Dufresnes, Berroneau, et al., 2020). For instance, hybridization events during post‐glacial range expansions have left traces of introgression over extensive geographical areas (Wielstra & Arntzen, 2012; Wielstra, Burke, Butlin, Avcı, et al., 2017).…”

Phylogeography and systematics ofAlgyroides(Sauria: Lacertidae) of the Balkan Peninsula

“…Alexandri et al., 2012, 2016; Tryfonopoulos et al., 2010), amphibians (e.g. Dufresnes, Strachinis, Suriadna, et al., 2019, Dufresnes, Berroneau, 2020, Dufresnes, Probonas, 2020; Pabijan et al., 2017; Wielstra & Arntzen, 2014) and reptiles such as lizards (e.g. Gvoždík et al., 2010; Kornilios et al., 2020; Marzahn et al., 2016; Psonis et al., 2018; Sagonas et al., 2014) and snakes (e.g.…”

Reconstruction of past distribution for the Mongolian toad, Strauchbufo raddei (Anura: Bufonidae) using environmental modeling

“…For instance, the impact of the Quaternary glaciations on biota is a topic of considerable interest and modeling can help answer questions. Thus, environmental modeling allows reconstructing the dynamics of species distribution in the Holocene and Pleistocene (e.g., Garcia-Porta et al, 2012;Wielstra et al, 2013;Skorinov & Litvinchuk, 2016;Dufresnes et al, 2018;Dufresnes et al, 2019;Dufresnes et al, 2020a;Dufresnes et al, 2020b).…”