Freshwater biodiversity is declining faster than marine or terrestrial diversity, yet its drivers are much less known. Although dams were shown to negatively affect river habitats, fragmentation by bridges has received less attention and is not as well understood. We tested whether and how bridges present barriers to aquatic insects by studying mass swarmings of Palingenia longicauda mayflies on river Tisza (NE-Hungary). Behavioural observations showed that upon approaching the bridge, upstream-flying mayflies typically turned back and 86% of them never crossed the bridge. Lack of physical contact showed that the bridge was an optical, rather than a mechanical barrier for the polarotactic mayflies. Imaging polarimetry showed that the bridge disrupted the horizontally polarizing channel guiding the flight of mayflies above the river. Energy loss, demonstrated by calorimetry, and time constraints forced females to lay eggs only downstream from the bridge. Counts of larval skins shed by swarming individuals showed nearly 2 to 1 female per male downstream from the bridge, while sex ratio above the bridge was slightly male-biased. We suggest that the surplus of parthenogenetic females, that produce only female larvae, downstream from the bridge may have led to the observed sex-ratio bias since the construction of the bridge (1942). Our results demonstrate that bridges can be optical barriers for aquatic insects and can cause population-level impacts, such as biased sex ratios, in natural populations. Sex ratio biases due to bridges may decrease effective population size and genetic variability, which may have contributed to the recent extinction of this species from most of Europe.

Freshwater biodiversity has declined dramatically in Europe in recent decades. Because of massive habitat pollution and morphological degradation of water bodies, many once widespread species persist in small fractions of their original range. These range contractions are generally believed to be accompanied by loss of intraspecific genetic diversity, due to the reduction of effective population sizes and the extinction of regional genetic lineages. We aimed to assess the loss of genetic diversity and its significance for future potential reintroduction of the long-tailed mayfly Palingenia longicauda (Olivier), which experienced approximately 98% range loss during the past century. Analysis of 936 bp of mitochondrial DNA of 245 extant specimens across the current range revealed a surprisingly large number of haplotypes (87), and a high level of haplotype diversity (). In contrast, historic specimens (6) from the lost range (Rhine catchment) were not differentiated from the extant Rába population (, ), despite considerable geographic distance separating the two rivers. These observations can be explained by an overlap of the current with the historic (Pleistocene) refugia of the species. Most likely, the massive recent range loss mainly affected the range which was occupied by rapid post-glacial dispersal. We conclude that massive range losses do not necessarily coincide with genetic impoverishment and that a species' history must be considered when estimating loss of genetic diversity. The assessment of spatial genetic structures and prior phylogeographic information seems essential to conserve once widespread species.

Ecosystem/habitat restoration has become a major goal of international biodiversity policy. However, restorations are often limited in space or time, and we know little on whether and how restoration and management affect vertebrates. Here we assessed the local and landscape‐scale effects of habitat restoration and management on small‐mammal communities in the Egyek–Pusztakócs marsh system (Hortobágy National Park, Hungary), site of the largest active restoration of grasslands on former croplands in Europe. We live‐trapped mice, voles and shrews in spring and autumn in 2 years (four sampling periods) at two sites in six habitat types: croplands, grasslands restored 3–6 years earlier and natural grasslands. Data on 421 individuals of 12 species showed that restored grasslands were similar to croplands and natural grasslands in species richness, abundance and composition. At the local scale, management influenced abundance because there were more small mammals in unmanaged and early‐mown grasslands with taller vegetation than in late‐mown or grazed grasslands with lower vegetation, or in ploughed croplands. Elevation was also important because sites at higher elevation provided refuges during spring floods or summer droughts. At the landscape scale, the proportion of restored and natural grasslands positively affected the abundance of small mammals, whereas the proportion of linear habitats (roads, canals) had a negative effect on abundance. Our results show that management is more important than restoration per se at the local scale, which is expected for habitat generalists such as small mammals in contrast to specialists such as plant‐feeding invertebrates. However, restoration provides landscape‐scale benefits by increasing the area of grasslands that can serve as refuges for small mammals in unfavourable periods. We thus conclude that a mosaic of restored and appropriately managed grasslands with tall vegetation will provide the best chances for the persistence of small‐mammal communities in dynamic landscapes.

Ecosystem restoration implies focusing on multiple trophic levels and ecosystem functioning, yet higher trophic levels, that is, animals, are less frequently targeted by restoration than plants. Habitat diversity, the spatial heterogeneity between and within habitat patches in a landscape, is a well-known driver of species diversity, and offers possible ways to increase species diversity at multiple trophic levels. We argue that habitat diversity is central in whole-ecosystem restoration as we review its importance, provide a practical definition for its components, and propose ways to target it in restoration. Restoration targeting habitat diversity is used commonly in aquatic ecosystems, mostly to increase the physical diversity of habitats, meant to provide more niches available to a higher number of animal species. To facilitate the uptake of habitat diversity in terrestrial ecosystem restoration, we distinguish between compositional and structural habitat diversity, because different animal groups will respond to different aspects of habitat diversity. We also propose four methods to increase habitat diversity: varying the starting conditions to obtain divergent successional pathways, emulating natural disturbances, establishing keystone structures, and applying ecosystem engineer species. We provide two case studies to illustrate how these components and methods can be incorporated in restoration. We conclude that targeting habitat diversity is a promising way to restore habitats for a multitude of species of animals and plants, and that it should become mainstream in restoration ecology and practice. We encourage the restoration community to consider compositional and structural habitat diversity and to specifically target habitat diversity in ecosystem restoration.

Összefoglaló:A kétéltűek (Amphibia) globálisan az egyik legveszélyeztetettebb élőlénycsoport, ezért elterjedésük ismerete alapvetően fontos, különösen olyan védett területeken, ahonnan kevés a korábbi információ és aktív beavatkozások zajlanak. Jelen munkánkban összesítjük az Egyekpusztakócsi mocsarak területén több korábbi vizsgálatban végzett felméréseink faunisztikai eredményeit, melyeket ötféle mintavételi módszerrel gyűjtöttünk 15 darab 2,5x2,5 kilométeres UTM cellában. Összesen 11 kétéltűfaj (pettyes gőte, dunai tarajosgőte, vöröshasú unka, barna ásóbéka, barna varangy, zöld varangy, zöld levelibéka, mocsári béka, kis tavibéka, nagy tavibéka, kecskebéka) 14 362 egyedét figyeltük meg. A hat legjobban felmért UTM négyzet között nem volt jelentős eltérés a diverzitás tekintetében. Két 10x10 kilométeres UTM négyzet (DT86 és 96) esetében öt és hét faj jelenlétével bővültek ismereteink. Nagy állományokkal volt jelen két Natura 2000-es jelölőfaj, a vöröshasú unka és a dunai tarajosgőte. Eredményeink szerint a mocsárrendszer a tájrehabilitációs beavatkozásoknak köszönhetően értékes és diverz kétéltűfaunának szolgál otthonául, ezért megfelelő kezelése és védelme kiemelt fontossággal bír. ábra. A vizsgálati terület (Egyek-pusztakócsi mocsárrendszer) kiterjedése, a nagyobb mocsarak elhelyezkedése és a terület 2,5x2,5 kilométeres UTM négyzetekkel való lefedettsége.