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The increasing urbanization process is hypothesized to drastically alter (semi‐)natural environments with a concomitant major decline in species abundance and diversity. Yet, studies on this effect of urbanization, and the spatial scale at which it acts, are at present inconclusive due to the large heterogeneity in taxonomic groups and spatial scales at which this relationship has been investigated among studies. Comprehensive studies analysing this relationship across multiple animal groups and at multiple spatial scales are rare, hampering the assessment of how biodiversity generally responds to urbanization. We studied aquatic (cladocerans), limno‐terrestrial (bdelloid rotifers) and terrestrial (butterflies, ground beetles, ground‐ and web spiders, macro‐moths, orthopterans and snails) invertebrate groups using a hierarchical spatial design, wherein three local‐scale (200 m × 200 m) urbanization levels were repeatedly sampled across three landscape‐scale (3 km × 3 km) urbanization levels. We tested for local and landscape urbanization effects on abundance and species richness of each group, whereby total richness was partitioned into the average richness of local communities and the richness due to variation among local communities. Abundances of the terrestrial active dispersers declined in response to local urbanization, with reductions up to 85% for butterflies, while passive dispersers did not show any clear trend. Species richness also declined with increasing levels of urbanization, but responses were highly heterogeneous among the different groups with respect to the richness component and the spatial scale at which urbanization impacts richness. Depending on the group, species richness declined due to biotic homogenization and/or local species loss. This resulted in an overall decrease in total richness across groups in urban areas. These results provide strong support to the general negative impact of urbanization on abundance and species richness within habitat patches and highlight the importance of considering multiple spatial scales and taxa to assess the impacts of urbanization on biodiversity.

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Genetic variability of the non-marine ostracod species Darwinula stevensoni was estimated by sequencing part of the nuclear and the mitochondrial genome. As Darwinulidae are believed to be ancient asexuals, accumulation of mutations should have occurred, both between alleles within lineages and between lineages, during the millions of years of parthenogenetic reproduction. However, our sequence data show the opposite: no variability in the nuclear ITS1 region was observed within or among individuals of D. stevensoni, despite sampling a geographical range from Finland to South Africa. Lack of allelic divergence might be explained by concerted evolution of rDNA repeats. Homogeneity among individuals may be caused either by slow molecular evolution in ITS1 or by a recent selective sweep. Variability of mitochondrial cytochrome oxidase (COI) was similar to intraspeci¢c levels in other invertebrates, thus weakening the latter hypothesis. Calibrating interspeci¢c, genetic divergences among D. stevensoni and other Darwinulidae using their fossil record enabled us to estimate rates of molecular evolution. Both COI and ITS1 evolve half as fast, at most, in darwinulids as in other invertebrates, and molecular evolution has signi¢-cantly slowed down in ITS1 of D. stevensoni relative to other darwinulids. A reduced ITS1 mutation rate might explain this inconsistency between nuclear and mitochondrial evolution in D. stevensoni.

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Ancient asexual animal groups, such as bdelloid rotifers and darwinuloid ostracods, are excellent model organisms to study the effects of long-term asexuality. However, the absolute length of time that these groups have been fully asexual is mostly ignored. In the case of the darwinuloid ostracods, the fossil record shows that sexual reproduction disappeared almost completely after the end of Permian mass extinction (ca. 245 Myr ago), although several putative records of males from the Mesozoic obscure the exact timeframe of obligate asexuality in darwinuloids. Here, we re-examine the Mesozoic darwinuloid records, with regard to the reproductive mode of the assemblages. Three criteria to distinguish males in fossil populations (lack of brood pouch, position of muscle scars and size dimorphism) are used here to test for the presence of males in darwinuloid assemblages. A large, well-preserved assemblage of Darwinula leguminella (Forbes 1885) from the latest Jurassic (ca. 145 Myr ago) of England is found to be markedly variable in size and shape, but nevertheless turns out to be an all female assemblage. The exceptional preservation of the material also allows the re-assignment of this species to the extant darwinuloid genus Alicenula. All other putative dimorphic darwinuloid records from the Mesozoic are re-examined using the same criteria. The hypothesis that these assemblages represent bisexual populations is rejected for all post-Triassic (ca. 208 Myr ago) records.