Habitat modifies the relationship between grass and herbivore species richness in a South African savanna

The savanna ecosystem is dominated by grasses, which are a key food source for many species of grazing animals. This relationship creates a diverse mosaic of habitats and contributes to the high grass species richness of savannas. However, how grazing interacts with environmental conditions in determining grass species richness and abundance in savannas is still insufficiently understood. In the Kruger National Park, South Africa, we recorded grass species and estimated their covers in 60 plots 50 × 50 m in size, accounting for varying proximity to water and different bedrocks. To achieve this, we located plots (i) near perennial rivers, near seasonal rivers, and on crests that are distant from all water sources and (ii) on nutrient-rich basaltic and nutrient-poor granitic bedrock. The presence and abundance of large herbivores were recorded by 60 camera traps located in the same plots. Grass cover was higher at crests and seasonal rivers than at perennial rivers and on basalts than on granites. The relationship between grass species richness and herbivore abundance or species richness was positive at crests, while that between grass species richness and herbivore species richness was negative at seasonal rivers. We found no support for controlling the dominance of grasses by herbivores in crests, but herbivore-induced microsite heterogeneity may account for high grass species richness there. In contrast, the decrease in grass species richness with herbivore species richness at seasonal rivers indicates that the strong grazing pressure over-rides the resistance of some species to grazing and trampling. We suggest that the relationships between grasses and herbivores may work in both directions, but the relationship is habitat-dependent, so that in less productive environments, the effect of herbivores on vegetation prevails, while in more productive environments along rivers the effect of vegetation and water supply on herbivores is more important.

Thirteen moth species (Lepidoptera, Erebidae, Noctuidae) newly recorded in South Africa, with comments on their distribution

Background

Thanks to the high diversity of ecosystems and habitats, South Africa harbours tremendous diversity of insects. The Kruger National Park, due to its position close to the border between two biogeographic regions and high heterogeneity of environmental conditions, represents an insufficiently studied hotspot of lepidopteran diversity. During our ecological research in the Kruger National Park, we collected abundant moth material, including several interesting faunistic records reported in this study.

New information

We reported 13 species of moths which had not yet been recorded in South Africa. In many cases, our records represented an important extension of the species' known distribution, including two species (Ozarbagaedei and O.persinua) whose distribution ranges extended into the Zambezian biogeographic region. Such findings confirmed the poor regional knowledge of lepidopteran diversity.

Water availability, bedrock, disturbance by herbivores, and climate determine plant diversity in South-African savanna

To identify factors that drive plant species richness in South-African savanna and explore their relative importance, we sampled plant communities across habitats differing in water availability, disturbance, and bedrock, using the Kruger National Park as a model system. We made plant inventories in 60 plots of 50 × 50 m, located in three distinct habitats: (i) at perennial rivers, (ii) at seasonal rivers with water available only during the rainy season, and (iii) on crests, at least ~ 5 km away from any water source. We predicted that large herbivores would utilise seasonal rivers' habitats less intensely than those along perennial rivers where water is available throughout the year, including dry periods. Plots on granite harboured more herbaceous and shrub species than plots on basalt. The dry crests were poorer in herb species than both seasonal and perennial rivers. Seasonal rivers harboured the highest numbers of shrub species, in accordance with the prediction of the highest species richness at relatively low levels of disturbance and low stress from the lack of water. The crests, exposed to relatively low pressure from grazing but stressed by the lack of water, are important from the conservation perspective because they harbour typical, sometimes rare savanna species, and so are seasonal rivers whose shrub richness is stimulated and maintained by the combination of moderate disturbance imposed by herbivores and position in the middle of the water availability gradient. To capture the complexity of determinants of species richness in KNP, we complemented the analysis of the above local factors by exploring large-scale factors related to climate, vegetation productivity, the character of dominant vegetation, and landscape features. The strongest factor was temperature; areas with the highest temperatures reveal lower species richness. Our results also suggest that Colophospermum mopane, a dominant woody species in the north of KNP is not the ultimate cause of the lower plant diversity in this part of the park.

Into the great wide open: do alien plants spread from rivers to dry savanna in the Kruger National Park?

Protected areas play an important role as refuges from invasive species impacts on biodiversity. Within the MOSAIK (Monitoring Savanna Biodiversity in the Kruger National Park) project, plant species were recorded in a representative set of 60 plots, 50 × 50 m in size, across the entire KNP, distributed so as to cover a range of savanna habitats, i.e. perennial rivers, seasonal rivers and dry crests, and two main bedrock types (granite and basalt). The data were used to assess the role of rivers in the dispersal of alien plants and study whether the alien plant species spread from rivers to open dry savanna. The resulting dataset provided the first thorough information on the spatial distribution of naturalised alien plants in KNP. In total, we recorded 20 plant species that are alien to the park, four of them considered invasive: Parthenium hysterophorus, Opuntia stricta, Xanthium strumarium and Zinnia peruviana. The most widespread species in KNP was Tridax procumbens, recorded in 11 plots (i.e. 18% of all sampled), four other species were found in > 10% of the plots. One species, Bidens bipinnata, was not previously reported from the park and represents a new record. The majority of aliens were concentrated along perennial rivers (60% of all occurrences), but some were repeatedly recorded at seasonal rivers as well and two of the most invasive species in KNP, Opuntia stricta and Parthenium hysterophorus, occurred also on dry crests away from water. The average number of alien species per plot was low (1.6), as was their mean percentage contribution to all species in a plot (2.2%), but some plots harboured as many as seven species and contributed up to 11.9%. Moreover, only 21 plots (35%) were alien-species free. In terms of the total species number per habitat, perennial rivers had significantly more aliens than crests and were marginally significantly richer than seasonal rivers. By recording all naturalised alien species occurring in the plots – many of them are not invasive but may become so in the future – and by using the GloNAF database of global distribution of naturalised species, we assessed the invasion potential of the recorded species.

Invasive alien species add to the uncertain future of protected areas

Establishing and managing protected areas (national parks, nature reserves and other sites of conservation value) represent the most common approach to conserving species and ecosystems, but these areas are vulnerable to global environmental change. Recently, Golden Kroner et al. (2019) suggested protected area downgrading, downsizing, and degazettement (PADDD) as one of the main threats to biodiversity conservation. However, there are several other elements, of similar concern, that threaten conservation efforts in protected areas, such as climate change and pollution. Here, in a commentary to the Golden Kroner et al. (2019) paper, we address an additional important element affecting protected area dynamics and robustness that was overlooked by these authors – invasions by alien species. We argue that invasive alien species (IAS) contribute directly to the pressures of biodiversity loss by competing with native species and modifying the characteristics of the invaded ecosystems, and virtually no protected areas are free from these effects. Therefore, excluding IAS from legal instruments and policy frameworks underpinning current conservation approaches in protected areas presents a great risk for nature conservation. Consequently, this aligns poorly with the idea of protected areas being a cornerstone for conservation at local, regional and national levels. For that reason and to paint a more complete picture of the effectiveness of protected areas, we argue that when other factors threatening the existence and functioning of protected areas are discussed, we also need to account for biological invasions. This will ensure that adaptive conservation management strategies protect a wide range of species, ecosystems, and landscapes. Hence, this commentary aims to be of general interest for policymakers, managers and researchers.

Small genome separates native and invasive populations in an ecologically important cosmopolitan grass

The literature suggests that small genomes promote invasion in plants, but little is known about the interaction of genome size with other traits or about the role of genome size during different phases of the invasion process. By intercontinental comparison of native and invasive populations of the common reed Phragmites australis, we revealed a distinct relationship between genome size and invasiveness at the intraspecific level. Monoploid genome size was the only significant variable that clearly separated the North American native plants from those of European origin. The mean Cx value (the amount of DNA in one chromosome set) for source European native populations was 0.490 ± 0.007 (mean ± SD), for North American invasive 0.506 ± 0.020, and for North American native 0.543 ± 0.021. Relative to native populations, the European populations that successfully invaded North America had a smaller genome that was associated with plant traits favoring invasiveness (long rhizomes, early emerging abundant shoots, resistance to aphid attack, and low C:N ratio). The knowledge that invasive populations within species can be identified based on genome size can be applied to screen potentially invasive populations of Phragmites in other parts of the world where they could grow in mixed stands with native plants, as well as to other plant species with intraspecific variation in invasion potential. Moreover, as small genomes are better equipped to respond to extreme environmental conditions such as drought, the mechanism reported here may represent an emerging driver for future invasions and range expansions.

Carnivore distribution across habitats in a central-European landscape: a camera trap study

Quantitative data on local variation in patterns of occurrence of common carnivore species, such as the red fox, European badger, or martens in central Europe are largely missing. We conducted a study focusing on carnivore ecology and distribution in a cultural landscape with the use of modern technology. We placed 73 automated infra-red camera traps into four different habitats differing in water availability and canopy cover (mixed forest, wetland, shrubby grassland and floodplain forest) in the Polabí region near Prague, Czech Republic. Each habitat was represented by three or four spatially isolated sites within which the camera traps were distributed. During the year of the study, we recorded nine carnivore species, including the non-native golden jackal. Habitats with the highest numbers of records pooled across all species were wetland (1279) and shrubby grassland (1014); fewer records were made in mixed (876) and floodplain forest (734). Habitat had a significant effect on the number of records of badger and marten, and a marginally significant effect on fox. In terms of seasonal dynamics, there were significant differences in the distribution of records among seasons in fox, marginally significant in least weasel, and the occurrence among seasons did not differ for badger and marten. In the summer, fox and marten were more active than expected by chance during the day, while the pattern was opposite in winter when they were more active during the night. Our findings on habitat preferences and circadian and seasonal activity provided the first quantitative data on patterns whose existence was assumed on the basis of conventional wisdom. Our study demonstrates the potential of a long-term monitoring approach based on infra-red camera traps. Generally, the rather frequent occurrence of recorded species indicates that most carnivore species are thriving in current central-European landscapes characterized by human-driven disturbances and urbanization.

Golden jackal (Canis aureus) in the Czech Republic: the first record of a live animal and its long-term persistence in the colonized habitat

A golden jackal (Canis aureus) individual was recorded ~40 km east of Prague in the Czech Republic. It is the first record of a living golden jackal in the country; up to now several individuals have been recorded but all of them were either shot dead or killed by a vehicle. The observed animal was documented by camera traps set up for research of carnivore diversity in different habitats in the study area. It was first photographed on 19 June 2015, and in total there were 57 records made by 12 traps until 24 March 2016 when the animal was still present in the area. Forty-nine of the 57 records were made in a shrubby grassland over an area of ~100 ha, 39% of sightings were during the day and 61% in the night. There were two distinct peaks in the circadian activity of the animal, from 4 to 10 a.m., and from 6 p.m. to midnight. We also review the verified records of the golden jackal in the Czech Republic, some of which were only published in local hunting magazines. However, the observation reported in this paper represents the first evidence of a long-term occurrence in Europe of the same golden jackal individual, that persisted for at least nine months and over winter, northwest of Hungarian-Austrian border where the population has been known to reproduce.