Mniophila, Stephens, 1831

Damaška, Albert František, Fikáček, Martin, Daňková, Klára, Čičovský, Daniel, Smyčková, Marie, Koštíř, Vojtěch & Munclinger, Pavel, 2024, From Europe to Caucasus: cryptic diversity and unexpected biogeographic history of a Western Palaearctic moss-inhabiting flea beetle (Chrysomelidae: Mniophila), Zoological Journal of the Linnean Society 201 (4), pp. 1-25 : 22-23

Biogeography of Mniophila

Our ancestral range reconstruction analyses place the major diversification centre for Mniophila in the Balkan Peninsula, with some overlap with Central Europe ( Fig. 4 ); these areas were connected during the Miocene–Pliocene boundary, allowing species to disperse and diversify around the Pannonian marine bay ( Popov et al. 2004). We found that M. bosnica is a Dinaric endemic, which is not surprising as there are numerous cases of endemics in this area and the Balkan Peninsula in general, especially in flightless beetle groups ( Guéorguiev 2007, Savić 2008, Král and Hillert 2013, Král et al. 2018, Tóth et al. 2019). From the Balkan Peninsula, Mniophila colonized Western Europe and the Ponto-Caucasus. Colonization of Europe from the Balkan Peninsula is not a surprising scenario: The Balkans are well-known as a Tertiary diversification centre of European species (Griffiths et al. 2004) and have also served as a glacial refugium for species that re-colonized Europe asser the glacial period ( Daporto 2010, Schmiư and Seitz 2022).

In contrast, the colonization of the Caucasus from Europe is an extremely rare scenario. Former studies on phylogeography in context to Caucasus have usually revealed the following patterns: (i) western and eastern phylogroups: the species form two clades, one distributed in Europe and one in the Ponto-Caucasus; a similar paưern appears, for example, in the case of medicinal leeches ( Trontelj and Utevsky 2012), and (ii) colonization of Europe from Caucasus (e.g. in the Primula vulgaris complex; Volkova et al. 2020). Colonization from Europe towards Asian mountain ranges is rare, documented, for example, for Hygromiidae land snails (Europe to Tien Shan Mts. in Central Asia; Neiber et al. 2017). Colonization of the Caucasus from the Balkans has been reported rarely; among animals, a possible case is known from one lineage of Poecilimon bush-crickets (Borissov et al. 2023), and barbel fishes ( Levin et al. 2019). Our study shows a first example of this rare colonization paưern in edaphic arthropods with limited dispersal abilities, demonstrating that Europe may be an important source of Caucasian biota.

Our study corroborates previous findings of very wide distributional ranges of Mniophila species ( Nadein 2009, GBIF. Org 2023). The range of M. muscorum reaches from the Balkan Peninsula and Sicily to the Pyrenees, Scotland, and southern Scandinavia and overlaps with nearly the entire range of the European beech ( Houston Durrant et al. 2016, Kembrytė et al. 2021). Such a wide distribution is unusual for moss-inhabiting flea beetles that are mostly known for very small distributional ranges and show local endemism. The most widespread moss-inhabiting flea beetles, apart from Mniophila , are European species of the genus Minota , especially M. obesa , also widespread in Europe (GBIF.Org 2023), but their ranges are also smaller than in Mniophila muscorum . In other parts of the world, there are Cangshanaltica castanea (Gruev, 1985) known from multiple localities across the Zhejiang Province in China ( Damaška et al. 2022b), as well as the Taiwanese Ivalia uenoi (Kimoto, 1970) distributed across the whole island of Taiwan ( Damaška et al. 2021). However, both these cases seem to be species complexes comprising multiple closely related species. On the contrary, Mniophila muscorum is widespread and genetically uniform. The distributional range of Mniophila muscorum is also large when compared to other flightless edaphic beetles in Europe, e.g. Acalles weevils, where only a few species have such large distribution ranges ( Buse 2012, Schüưe and Stüben 2015).

Species’ diversity and taxonomy of Mniophila

Our samples of Mniophila covered almost the entire range of its distribution ( Nadein 2009, Baviera and Biondi 2015, GBIF.Org 2023) and all known Mniophila species, except M. taurica , an endemic to the Crimea. We show that a large proportion of the species’ diversity of Mniophila has been overlooked, with subtle but reliable morphological differences among species considered as part of intraspecific variability. Nadein (2009) recognized two widespread species in Europe: M. muscorum and M. bosnica . Wańkowicz (1880) recognized a third species, M wroblewskii , based on differences in elytral puncturation: this is confirmed here based on the DNA data, with elytral puncturation being confirmed as a crucial diagnostic character. However, the species was immediately synonymized ( Weise 1883), not based on type material studies, but on an assumption that elytral puncturation could not be considered diagnostic for Mniophila species. This view was adopted in all subsequent studies ( Heikertinger 1948, Čížek and Doguet 2008, Nadein 2009, Döberl 2010). Additionally, two synonymous names exist for M. muscorum : Teinodactyla bryozoa Gistel, 1857 synonymized by Monrós and Bechyné (1956) and Altica monticola Grimmer, 1841 synonymized by Weise (1876). Both type specimens for the names were collected in Styria, Austria, where both M. muscorum and M. wroblewskii are distributed; however, we were not able to study the types, because they are lost ( Bousquet 2016, Fanti 2018). Therefore, it is not possible to find out whether either of these names in fact refer to M. wroblewskii, and they remain junior synonyms of M. muscorum following previous authors (Nadein

2009, Döberl 2010). Another European species, M. haveli sp. nov., remained undetected until now, despite the fact that it occurs in the Carpathians, including Slovakia, i.e. one of the best-studied areas in Europe ( Rozner 1996, Čížek and Doguet 2008, Bezdek 2021). Our findings, therefore, show that new species of beetles can be found even in well-studied areas, underpinning the limitations of our current knowledge of European beetle fauna. Mniophila bosnica is a distinct morphologically distinguishable species restricted to the south-west Balkans. Previous studies ( Nadein 2009, Borowiec et al. 2011) reported M. bosnica from Central Europe, the Alps, and Great Britain, but these records seem to refer to misidentified M. muscorum and M. wroblewskii , possibly due to relatively large intraspecific variability in M. muscorum , as well as the true interspecific variability among European Mniophila . The material identified previously as M. bosnica needs to be revised in future studies.

Our analyses recognized three species of Mniophila in the Ponto-Caucasian region in congruence with previous studies by Nadein (2009); however, the taxonomic identity of the M. caucasica – transcaucasica complex has not been sufficiently resolved. Despite the fact that we found two genetically wellseparated lineages in the Caucasus (supported by the ABGD species-delimitation analysis), the holotypes of M. caucasica and M. transcaucasica are morphologically very similar. Differences between the genetic lineages are present, but are relatively shallow in comparison to other Mniophila species. The diagnostic characters proposed by Nadein (2009), e.g. the shape of the antennomeres, vary more among specimens revealed as conspecific by DNA than between the holotypes of M. caucasica and M. transcaucasica , and seem inapplicable for species’ recognition. Consequently, it needs to be confirmed in the future whether or not the holotypes of these two species are conspecific. A future study based on extensive samples from the Caucasus, including specimens from the type localities of the two species described by Nadein, as well as a population genetics analysis of gene flow, is crucial for resolving the taxonomic identity of the species. Another Ponto-Caucasian species, Mniophila turcica , is morphologically similar to M. bosnica , the sister group of the Ponto-Caucasian lineage; we extend its distributional range to the Georgian Lesser Caucasus. The lack of DNA-grade material prevented us from revealing the phylogenetic position of the Crimean M. taurica . We consider M. taurica a valid species morphologically similar to the Ponto-Caucasian species, but fresh material or the application of museomic methods would be needed to obtain DNA data, to test its phylogenetic position.

Figures

Figure 4. Results from the BioGeoBEARS ancestral range reconstruction mapping based on the phylogenetic tree inferred from the BEAST time-calibrated Bayesian phylogenetic analysis.Above:historic biogeography scenario based on the DEC+j model; below:a map showing the delimitations of the distributional areas used in the analysis: W, Western Europe; E, Central Europe; I, Italy; B, Balkan; P, Pontus; C, Caucasus.