Genetic structure and distribution of Parisotoma notabilis (Collembola) in Europe: Cryptic diversity, split of lineages and colonization patterns

Sympatry of genetic lineages of Parisotomanotabilis s. l. (Collembola, Isotomidae) in the East European Plain

Parisotomanotabilis (Schaeffer, 1896) is one of the most abundant eurytopic species of springtails in temperate regions of the northern hemisphere, and is often used as a model species for studies on the genetics of soil microarthropod populations. Six genetic lineages (L0, L1, L2, L3, L4-Saltzwedel, L4-Hebert) are known which are distributed mainly parapatrically in Western and Central Europe. Individuals of P.notabilis from 21 locations on the East European Plain were analyzed. Three genetic lineages were found: L1, L2, L4-Hebert. In contrast to Western and Central Europe, the coexistence of two or three lineages was revealed in about half of the locations on the East European Plain. The most diverse genetic composition of P.notabilis populations was noted in natural forests and slightly disturbed habitats, while the least diverse was in places with a high anthropogenic influence.

Distinct phylogeographic patterns in populations of two oribatid mite species from the genus Pantelozetes (Acari, Oribatida, Thyrisomidae) in Central Europe

Oribatid mites are important decomposers of dead organic matter in soils across the world. Their origin dates back at least 380 Mya. Multiple severe climatic changes during Late Pliocene and Pleistocene shaped the migration patterns of these organisms and should be reflected in the genetic variability of their current populations. In this study, we examined the genetic diversity and phylogeographic structure as well as the evolutionary history of populations of two ecologically different oribatid mite species. Pantelozetes cavaticus is a troglophile oribatid mite known mainly from Central European caves, whereas Pantelozetes paolii is a common surface eurytopic species with Holarctic distribution. We used two molecular markers-mitochondrial cytochrome c oxidase subunit I (COI) and the nuclear D3 region of the 28S rDNA gene-to reveal phylogenetic relationships between contemporary populations. Whereas the D3 region showed minimal or no variability within populations, COI appeared to be a relevant marker for population studies. Phylogeographic analysis based on COI detected two lineages of P. cavaticus ('Czech' and 'Slovak'), which separated during the Late Pliocene (2.9 Mya) and revealed the existence of one new species. In contrast, three identified genetic lineages of P. paolii (radiation time 2.9 and 1.2 Mya, respectively) uncovered in this study were found to coexist in the distant sampling localities, suggesting a connection between populations even over long distances.

Unexpected diversity in the host-generalist oribatid mite Paraleius leontonychus (Oribatida, Scheloribatidae) phoretic on Palearctic bark beetles

Bark beetles are feared as pests in forestry but they also support a large number of other taxa that exploit the beetles and their galleries. Among arthropods, mites are the largest taxon associated with bark beetles. Many of these mites are phoretic and often involved in complex interactions with the beetles and other organisms. Within the oribatid mite family Scheloribatidae, only two of the three nominal species of Paraleius have been frequently found in galleries of bark beetles and on the beetles themselves. One of the species, P. leontonychus, has a wide distribution range spanning over three ecozones of the world and is believed to be a host generalist, reported from numerous bark beetle and tree species. In the present study, phylogenetic analyses of one mitochondrial and two nuclear genes identified six well supported, fairly divergent clades within P. leontonychus which we consider to represent distinct species based on molecular species delimitation methods and largely congruent clustering in mitochondrial and nuclear gene trees. These species do not tend to be strictly host specific and might occur syntopically. Moreover, mito-nuclear discordance indicates a case of past hybridization/introgression among distinct Paraleius species, the first case of interspecific hybridization reported in mites other than ticks.

Extreme genetic diversity among springtails (Collembola) in subterranean calcretes of arid Australia

The subterranean islands hypothesis for calcretes of the Yilgarn region in Western Australia applies to many stygobitic (subterranean-aquatic) species that are "trapped" evolutionarily within isolated aquifers due to their aquatic lifestyles. In contrast, little is known about the distribution of terrestrial-subterranean invertebrates associated with the calcretes. We used subterranean Collembola from the Yilgarn calcretes to test the hypothesis that troglobitic species, those inhabiting the subterranean unsaturated (non-aquatic) zone of calcretes, are also restricted in their distribution and represent reciprocally monophyletic and endemic lineages. We used the barcoding fragment of the mtDNA cytochrome c oxidase subunit 1 (COI) gene from 183 individuals to reconstruct the phylogenetic history of the genus Pseudosinella Schäffer (Collembola, Lepidocyrtidae) from 10 calcretes in the Yilgarn. These calcretes represent less than 5% of the total possible calcretes in this region, yet we show that their diversity for subterranean Collembola comprises a minimum of 25 new species. Regionally, multiple levels of diversity exist in Pseudosinella, indicative of a complex evolutionary history for this genus in the Yilgarn. These species have probably been impacted by climatic oscillations, facilitating their dispersal across the landscape. The results represent a small proportion of the undiscovered diversity in Australia's arid zone.

Mitochondrial Genome Diversity in Collembola: Phylogeny, Dating and Gene Order

Collembola (springtails) are an early diverging class of apterygotes, and mark the first substantial radiation of hexapods on land. Despite extensive work, the relationships between major collembolan lineages are still debated and, apart from the Early Devonian fossil Rhyniella praecursor, which demonstrates their antiquity, the time frame of springtail evolution is unknown. In this study, we sequence two new mitochondrial genomes and reanalyze all known Collembola mt-genomes, including selected metagenomic data, to produce an improved phylogenetic hypothesis for the group, develop a tentative time frame for their differentiation, and provide a comprehensive overview of gene order diversity. Our analyses support most taxonomically recognized entities. We find support for an Entomobryomorpha + Symphypleona clade, while the position of Neelipleona could not be assessed with confidence. A Silurian time frame for their basal diversification is recovered, with an indication that divergence times may be fairly old overall. The distribution of mitochondrial gene order indicates the pancrustacean arrangement as plesiomorphic and dominant in the group, with the exception of the family Onychiuridae. We distinguished multiple instances of different arrangements in individual genomes or small clusters. We further discuss the opportunities and drawbacks associated with the inclusion of metagenomic data in a classic study on mitochondrial genome diversity.

Ancient landscapes of the Namib Desert harbor high levels of genetic variability and deeply divergent lineages for Collembola

AIM

To assess spatial patterns of genetic and species-level diversity for Namib Desert Collembola using mitochondrial DNA cytochrome c oxidase subunit I (COI) gene sequences.

LOCATION

Namib Desert gravel plains.

TAXON

Collembola (springtails).

METHODS

A total of 77 soil samples were collected along NE-SW (60 km) and E-W (160 km) transects from within a 4,000 km2 area of the Namib Desert gravel plains. We extracted 434 springtails from the 37 samples which contained Collembola and sequenced them at the COI gene locus. In the absence of specific taxonomic keys and previous genetic data for these taxa, we used Generalized Mixed Yule Coalescent (GMYC) analyses to provide putative species-level designations.

RESULTS

We obtained 341 successful COI sequences, 175 of which were unique haplotypes. GMYC analyses identified 30 putative species, with up to 28% sequence divergence (uncorrected p-distance). The distribution of genetic variants was disjunct, with 97% of haplotypes and 70% of "GMYC species" found only at single sites.

MAIN CONCLUSIONS

Dispersal events, although rare, may be facilitated by environmental events such as prevailing onshore winds or occasional flow of rainwater to the coast. We conclude that the high genetic diversity we observed is the result of ancient springtail lineages, patchy distribution of suitable habitats, and limited dispersal (gene flow) among habitable locations.

DNA-based approaches uncover cryptic diversity in the European Lepidocyrtus lanuginosus species group (Collembola: Entomobryidae)

DNA sequence data and phylogenies are useful tools for species delimitation, especially in taxa comprising cryptic species. The Lepidocyrtus lanuginosus species group (Collembola: Entomobryidae) comprises three morphospecies and distinct cryptic species. We applied three DNA-based methods to delimit species boundaries in the L. lanuginosus species group across central and southern Europe. Using cytochrome c oxidase subunit I and II, we identified gaps of genetic distances that indicate species boundaries and found 10 and 9 distinct genetic lineages in L. cyaneus and L. lanuginosus, respectively. The nuclear gene elongation factor 1-α delimited 89% of the lineages but 28S rDNA (D1–2 domain) was too conserved for this purpose. The phylogenetic trees showed that L. cyaneus and L. lanuginosus are polyphyletic, suggesting that body colour is insufficient for delimiting species in the L. lanuginosus species group. Our study challenges the current morphology-based species delimitation in the L. lanuginosus species group and suggests that molecular approaches are needed for fast and accurate determination of Collembola species in both taxonomic and ecological studies. Overall, the results suggest that wide geographic sampling combined with molecular phylogenetic approaches is needed to delimit species and to understand the full range of cryptic diversity in Collembola.