Molecular phylogeny and timing of diversification in Alpine Rhithrogena (Ephemeroptera: Heptageniidae)

Laurent Vuataz; Sereina Rutschmann; Michael T Monaghan; Michel Sartori

doi:10.1186/s12862-016-0758-1

Molecular phylogeny and timing of diversification in Alpine Rhithrogena (Ephemeroptera: Heptageniidae)

BMC Evol Biol. 2016 Sep 21;16(1):194. doi: 10.1186/s12862-016-0758-1.

Authors

Laurent Vuataz^{1

2}, Sereina Rutschmann^{3

4

5}, Michael T Monaghan^{3

4}, Michel Sartori^{6

7}

Affiliations

¹ Musée cantonal de zoologie, Palais de Rumine, Place de la Riponne 6, 1014, Lausanne, Switzerland. laurentvuataz@yahoo.fr.
² Department of Ecology and Evolution, Biophore, University of Lausanne, 1015, Lausanne, Switzerland. laurentvuataz@yahoo.fr.
³ Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), 12587, Berlin, Germany.
⁴ Berlin Center for Genomics in Biodiversity Research, 14195, Berlin, Germany.
⁵ Department of Biochemistry, Genetics and Immunology, University of Vigo, 36310, Vigo, Spain.
⁶ Musée cantonal de zoologie, Palais de Rumine, Place de la Riponne 6, 1014, Lausanne, Switzerland.
⁷ Department of Ecology and Evolution, Biophore, University of Lausanne, 1015, Lausanne, Switzerland.

Abstract

Background: Larvae of the Holarctic mayfly genus Rhithrogena Eaton, 1881 (Ephemeroptera, Heptageniidae) are a diverse and abundant member of stream and river communities and are routinely used as bio-indicators of water quality. Rhithrogena is well diversified in the European Alps, with a number of locally endemic species, and several cryptic species have been recently detected. While several informal species groups are morphologically well defined, a lack of reliable characters for species identification considerably hampers their study. Their relationships, origin, timing of speciation and mechanisms promoting their diversification in the Alps are unknown.

Results: Here we present a species-level phylogeny of Rhithrogena in Europe using two mitochondrial and three nuclear gene regions. To improve sampling in a genus with many cryptic species, individuals were selected for analysis according to a recent DNA-based taxonomy rather than traditional nomenclature. A coalescent-based species tree and a reconstruction based on a supermatrix approach supported five of the species groups as monophyletic. A molecular clock, mapped on the most resolved phylogeny and calibrated using published mitochondrial evolution rates for insects, suggested an origin of Alpine Rhithrogena in the Oligocene/Miocene boundary. A diversification analysis that included simulation of missing species indicated a constant speciation rate over time, rather than any pronounced periods of rapid speciation. Ancestral state reconstructions provided evidence for downstream diversification in at least two species groups.

Conclusions: Our species-level analyses of five gene regions provide clearer definitions of species groups within European Rhithrogena. A constant speciation rate over time suggests that the paleoclimatic fluctuations, including the Pleistocene glaciations, did not significantly influence the tempo of diversification of Alpine species. A downstream diversification trend in the hybrida and alpestris species groups supports a previously proposed headwater origin hypothesis for aquatic insects.

Keywords: Dated phylogeny; Diversification; Ephemeroptera; Freshwater insects; Headwater; Lineage-through-time; Mayfly; Pleistocene glaciations; Speciation.