Genetic and morphological diversity of Sphagnum angustifolium, S. flexuosum and S. fallax in Europe

Abstract

Molecular and morphological evolution of species may be decoupled which can lead to contrasting delimitation of taxonomic units based on morphological and genetic characters. The moss genus Sphagnum (peat mosses) provides a good example in which morphological and genetic characters often contradict each other. We investigated morphological and genetic variability within a highly polymorphic and taxonomically controversial species complex of the genus Sphagnum in order to reveal the ultimate causes of discordance between morphology and molecular evolution. Specifically, we aimed at addressing the following questions: (1) Are the three closely related European taxa (S. angustifolium, S. fallax, S. flexuosum) of the S. recurvum group morphologically and genetically distinct entities? (2) Are morphological and genetic groups concordant? (3) Is there any sign of hybridization among taxa that might complicate their morphological delimitation? We show that European specimens of the S. recurvum group form three distinct gene pools based on 11 polymorphic microsatellite markers. Individuals defined as morphotype “fallax” appear to be genetically clearly distinct from both morphotype “angustifolium” and “flexuosum”. However, for the latter two morphotypes, traditionally used morphological and genetic markers provide partly incongruent taxonomic delimitations. We show that in about 13% of the accessions 12 traditionally used morphological characters cannot fully distinguish the genetic groups revealed. Our genetic analysis also reveals that only a low proportion of the specimens (3%) is admixed suggesting that hybridization is unlikely to explain the taxonomical controversies observed. Therefore, we hypothesize that taxonomic controversies are likely due to the extreme phenotypic plasticity of morphological characters rather than to porous species boundaries.

Local adaptations in bryophytes revisited: the genetic structure of the calcium‐tolerant peatmoss Sphagnum warnstorfii along geographic and pH gradients

“…Interspecific hybridization has been already documented in the subgenus Acutifolia by Cronberg (1998), Flatberg et al (2006, and Natcheva and Cronberg (2007). Microsatellite data further revealed hybridization within the subgenus Cuspidata (Szurdoki et al 2014), and hybridization among species from different subgenera has even been shown (Karlin et al 2009(Karlin et al , 2014. The ability to hybridize may not be uniform across the subgenus Acutifolia, and the genetic data suggest that S. rubellum and S. warnstorfii tend to hybridize easily (Shaw and Cox 2005).…”

“…Microsatellite data further revealed hybridization within the subgenus Cuspidata (Szurdoki et al. ), and hybridization among species from different subgenera has even been shown (Karlin et al. , ).…”

“…, ; Stenøien and Såstad ; Szurdoki et al. ), and the subgenus Sphagnum (Thingsgaard ). Most studies were focused on calcifuge species, while calcium‐tolerant species have been studied only marginally.…”

“…The local population structure has been described in a few species of the Sphagnum subgenus Acutifolia (e.g., Shaw and Srodon 1995;Cronberg 1998;Natcheva and Cronberg 2003;Gunnarsson et al 2007), the subgenus Subsecunda (e.g., Shaw et al 2008;Ricca et al 2011), the subgenus Cuspidata Stenøien and S astad 1999;Szurdoki et al 2014), and the subgenus Sphagnum (Thingsgaard 2001). Most studies were focused on calcifuge species, while calcium-tolerant species have Northern Minnesota (Vitt and Slack 1984) n/a 7.4 n/a Schwarzwald (Dierssen and Dierssen 1984) 4.2 4.9 5.5 Canada (Andrus 1986) 4.0 6.2 7.5 Maine, Northern America (Anderson et al 1995) n/a 8.3 n/a Western Italian Alps (Miserere et al 2003) n/a 5.4 n/a Central Europe (H ajek et al 2006) 5 been studied only marginally.…”

Testing inter‐regional variation in pH niches of fen mosses

“…S. flexuosum is morphologically similar to S. fallax , but genetically distinct (Szurdoki et al. ). Already, Rybníček () reported S. flexuosum from fens with pH 5 or even pH 6.…”