Brigitte Braschler

Species richness changes lag behind climate change

Species-energy theory indicates that recent climate warming should have driven increases in species richness in cool and species-poor parts of the Northern Hemisphere. We confirm that the average species richness of British butterflies has increased since 1970–82, but much more slowly than predicted from changes of climate: on average, only one-third of the predicted increase has taken place. The resultant species assemblages are increasingly dominated by generalist species that were able to respond quickly. The time lag is confirmed by the successful introduction of many species to climatically suitable areas beyond their ranges. Our results imply that it may be decades or centuries before the species richness and composition of biological communities adjusts to the current climate.

Effects of small-scale grassland fragmentation and frequent mowing on population density and species diversity of orthopterans: a long-term study

Abstract 1. Habitat fragmentation is considered one of the major threats to invertebrate diversity in semi‐natural grassland. However, the effects of habitat fragmentation through mowing on the rich insect fauna of these grasslands have not been sufficiently investigated and experiments are especially rare.

Effects of experimental small-scale grassland fragmentation on spatial distribution, density, and persistence of ant nests

Abstract.  1. Grassland fragmentation is expected to influence the abundance of different invertebrate species to a different extent. Fragmentation‐related effects are of particular importance in species that interact with many other species.

Realizing a synergy between research and education: how participation in ant monitoring helps raise biodiversity awareness in a resource-poor country

Biodiversity-rich, resource-poor countries need to allocate scarce resources to the competing goals of identifying and monitoring their biodiversity and educating their populace about it. Often only relatively wealthy individuals participate in biodiversity-related volunteering, while the poor are left on the margins. We present a case study that shows how monitoring and education can be combined. South African high school scholars from mostly disadvantaged communities participated in ant monitoring in transformed sites and received lessons using their own data. The project provides baseline data on an important insect group in a region where invertebrate monitoring is rare. Participation in a real study enhances the scholars’ interest in science and direct interaction with scientists allows them to enquire about careers they might not otherwise consider. Here we outline how the project works, what participants learnt, and demonstrate that the data provide insights into ant diversity and the effects of landscape transformation.

The Fynbos and Succulent Karoo biomes do not have exceptional local ant richness

Background The Fynbos (FB) and Succulent Karoo biomes (SKB) have high regional plant diversity despite relatively low productivity. Local diversity in the region varies but is moderate. For insects, previous work suggests that strict phytophages, but not other taxa, may have high regional richness. However, what has yet to be investigated is whether the local insect species richness of FB and SKB is unusual for a region of this productivity level at this latitude, and whether regional richness is also high. Here we determine whether this is the case for ants. Methodology/Principal Findings We use species richness data from pitfall traps in the FB and SKB in the Western Cape Province, South Africa and a global dataset of local ant richness extracted from the literature. We then relate the globally derived values of local richness to two energy-related predictors—productive energy (NDVI) and temperature, and to precipitation, and compare the data from the FB and SKB with these relationships. We further compare our local richness estimates with that of similar habitats worldwide, and regional ant richness with estimates derived from other regions. The local ant species richness of the FB and SKB falls within the general global pattern relating ant richness to energy, and is similar to that in comparable habitats elsewhere. At a regional scale, the richness of ants across all of our sites is not exceptional by comparison with other regional estimates from across the globe. Conclusions/Significance Local richness of ants in the FB and SKB is not exceptional by global standards. Initial analyses suggest that regional diversity is also not exceptional for the group. It seems unlikely that the mechanisms which have contributed to the development of extraordinarily high regional plant diversity in these biomes have had a strong influence on the ants.

Grain-dependent relationships between plant productivity and invertebrate species richness and biomass in calcareous grasslands

Abstract The relationships among productivity, species richness and consumer biomass are of fundamental importance for understanding determinants of biodiversity. These relationships may depend on grain size. We examined the relationships between productivity (above-ground phytomass) and plant species richness and between productivity and species richness and biomass of gastropods and grasshoppers using sampling units of different sizes (0.5, 2.75 and 23 m 2 ) in nutrient-poor, calcareous grasslands in north-western Switzerland in two successive years. Species richness of forbs had a unimodal relationship with productivity in sampling units of 0.5 m 2 and was negatively correlated with productivity at the other two plot sizes in one year. In the other year, forb species richness tended to decrease with productivity in sampling units of 23 m 2 . No similar relationship was found for grasses. Gastropod biomass had a unimodal relationship with productivity at 0.5 m 2 in the first year. Grasshopper species richness was correlated with forb species richness at plot sizes of 2.75 and 23 m 2 . This study demonstrates that patterns detected between productivity and diversity and between productivity and biomass of consumers depend on the grain size used in the investigation and vary among years. Die Zusammenhange zwischen Produktivitat, Artenreichtum und Biomasse von Konsumenten sind wichtig, um zu verstehen, was Biodiversitat beeinflust. Diese Zusammenhange konnen von der Grose der Untersuchungsflache abhangig sein. Wir untersuchten wahrend zwei aufeinanderfolgenden Jahren die Zusammenhange zwischen Produktivitat (oberirdische Pflanzenbiomasse) und Artenreichtum von Gefaspflanzen, sowie zwischen Produktivitat und Artenreichtum und Biomasse von Schnecken und Heuschrecken bezuglich dreier raumlicher Skalen (0,5, 2,75 und 23 m 2 ) in Kalkmagerrasen in der Nordwestschweiz. Der Zusammenhang zwischen dem Artenreichtum von Krautern und der Produktivitat war unimodal in Flacheneinheiten von 0,5 m 2 und negativ in Flacheneinheiten von 2,75 und 23 m 2 im ersten Jahr und war tendenziell negativ in Flacheneinheiten von 23 m 2 im zweiten Jahr, wahrend kein solcher Zusammenhang bei Grasern gefunden wurde. Der Zusammenhang zwischen Produktivitat und Biomasse von Schnecken war unimodal in Flacheneinheiten von 0,5 m 2 im ersten Jahr. Auserdem bestand ein Zusammenhang zwischen dem Artenreichtum von Krautern und Heuschrecken in Flacheneinheiten von 2,75 und 23 m 2 . Diese Arbeit zeigt, das Zusammenhange zwischen Produktivitat und Diversitat sowie zwischen Produktivitat und Biomasse von Konsumenten von der Grose der Untersuchungsflache abhangen und zwischen Jahren variieren.

Diverse Effects of a Seven-Year Experimental Grassland Fragmentation on Major Invertebrate Groups

Habitat fragmentation is a major driver of biodiversity loss, but observed effects vary and may depend on the group examined. Time since fragmentation may explain some differences between taxonomical groups, as some species and thus species composition respond with a delay to changes in their environment. Impacts of drivers of global change may thus be underestimated in short-term studies. In our study we experimentally fragmented nutrient-poor dry calcareous grasslands and studied the response of species richness, individual density and species composition of various groups of invertebrates (gastropods, ants, ground beetles, rove beetles, orthoptera, spiders, woodlice) in 12 small (1.5 m * 1.5 m) and 12 large (4.5 m * 4.5 m) fragments and their corresponding control plots after 7 years. We further examined responses to fragmentation in relation to body size and habitat preferences. Responses to fragmentation varied between taxonomical groups. While spider species richness and individual density were lower in fragments, the opposite was true for an orthopteran species and woodlice. Species composition and β-diversity differed between fragments and control plots for some groups. However, the interaction treatment*plot size was rarely significant. Species with high occupancy rates in undisturbed control plots responded more negatively to the fragmentation, while species with large body size were relatively more abundant in fragments in some groups. No effect of the fragmentation was found for ants, which may have the longest lag times because of long-lived colonies. However, relationships between abundance and the species’ preferences for environmental factors affected by edge effects indicate that ant diversity too may be affected in the longer-term. Our results show the importance of considering different groups in conservation management in times of widespread fragmentation of landscapes. While species richness may respond slowly, changes in abundance related to habitat preferences or morphology may allow insights into likely long-term changes.

Diverse effects of degree of urbanisation and forest size on species richness and functional diversity of plants, and ground surface-active ants and spiders

Urbanisation is increasing worldwide and is regarded a major driver of environmental change altering local species assemblages in urban green areas. Forests are one of the most frequent habitat types in urban landscapes harbouring many native species and providing important ecosystem services. By using a multi-taxa approach covering a range of trophic ranks, we examined the influence of degree of urbanisation and forest size on the species richness and functional diversity of plants, and ground surface-active ants and spiders. We conducted field surveys in twenty-six forests in the urban region of Basel, Switzerland. We found that a species’ response to urbanisation varied depending on trophic rank, habitat specificity and the diversity indices used. In plants, species richness decreased with degree of urbanisation, whereas that of both arthropod groups was not affected. However, ants and spiders at higher trophic rank showed greater shifts in species composition with increasing degree of urbanisation, and the percentage of forest specialists in both arthropod groups increased with forest size. Local abiotic site characteristics were also crucial for plant species diversity and species composition, while the structural diversity of both leaf litter and vegetation was important for the diversity of ants and spiders. Our results highlight that even small urban forests can harbour a considerable biodiversity including habitat specialists. Nonetheless, urbanisation directly and indirectly caused major shifts in species composition. Therefore, special consideration needs to be given to vulnerable species, including those with special habitat requirements. Locally adapted management practices could be a step forward to enhance habitat quality in a way to maximize diversity of forest species and thus ensure forest ecosystem functioning; albeit large-scale factors also remain important.