Long-term isolation of European steppe outposts boosts the biome’s conservation value

The European steppes and their biota have been hypothesized to be either young remnants of the Pleistocene steppe belt or, alternatively, to represent relicts of long-term persisting populations; both scenarios directly bear on nature conservation priorities. Here, we evaluate the conservation value of threatened disjunct steppic grassland habitats in Europe in the context of the Eurasian steppe biome. We use genomic data and ecological niche modelling to assess pre-defined, biome-specific criteria for three plant and three arthropod species. We show that the evolutionary history of Eurasian steppe biota is strikingly congruent across species. The biota of European steppe outposts were long-term isolated from the Asian steppes, and European steppes emerged as disproportionally conservation relevant, harbouring regionally endemic genetic lineages, large genetic diversity, and a mosaic of stable refugia. We emphasize that conserving what is left of Europe’s steppes is crucial for conserving the biological diversity of the entire Eurasian steppe biome.


Statistics
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n/a Confirmed The exact sample size (n) for each experimental group/condition, given as a discrete number and unit of measurement A statement on whether measurements were taken from distinct samples or whether the same sample was measured repeatedly The statistical test(s) used AND whether they are one-or two-sided Only common tests should be described solely by name; describe more complex techniques in the Methods section.
A description of all covariates tested A description of any assumptions or corrections, such as tests of normality and adjustment for multiple comparisons A full description of the statistical parameters including central tendency (e.g. means) or other basic estimates (e.g. regression coefficient) AND variation (e.g. standard deviation) or associated estimates of uncertainty (e.g. confidence intervals) For null hypothesis testing, the test statistic (e.g. F, t, r) with confidence intervals, effect sizes, degrees of freedom and P value noted Give P values as exact values whenever suitable.

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For hierarchical and complex designs, identification of the appropriate level for tests and full reporting of outcomes Estimates of effect sizes (e.g. Cohen's d, Pearson's r), indicating how they were calculated Our web collection on statistics for biologists contains articles on many of the points above.

Software and code
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Data analysis
For manuscripts utilizing custom algorithms or software that are central to the research but not yet described in published literature, software must be made available to editors/reviewers. We strongly encourage code deposition in a community repository (e.g. GitHub). See the Nature Research guidelines for submitting code & software for further information.

Data
Policy information about availability of data All manuscripts must include a data availability statement. This statement should provide the following information, where applicable: -Accession codes, unique identifiers, or web links for publicly available datasets -A list of figures that have associated raw data -A description of any restrictions on data availability Philipp Kirschner, philipp.kirschner@gmail.com Feb 24, 2020 No software was used for data collection.
All tools and software packages that were used for data analysis are given in the method section and the supplementary information, respectively. A quick summary: Bamindexdecoder v. Grasshoppers were collected as adults, as larval and subadult stages do not allow unambiguous identification on species level. Usually both sexes were collected, except when permits did not allow collection of females. In case of the ant P. taurica, worker ants (females) were collected.
All species were sampled across their distribution ranges, while extrazonal occurrences were more densely sampled than zonal ones. Three randomly taken individuals were sampled per population. As sequencing ressources were a limiting factor, we chose a sample size that allowed us to still detect genetic variability within a population, and at the same time, allowed us to sequence as many populations as possible from the steppe biome. No data were excluded from the analyses From each species-specific genetic (RadSeq) datasets 10% of the samples were replicated. After sucessful evaluation of the reproducibility of the results the replicates were removed from the final datasets.
As our study is based on field-collected samples, no randomisation was necessary.
Blinding was not necessary for this study Field conditions were not considered to be relevant for the conducted sampling. Generally days without precipitation were favoured to collect insects though.
All sampled localities and their coordinates are given in Supplementary Table 1