Biology subjects

Schroder, B.

Publications and source records attributed to Schroder, B..

5 recordsLinked to original sources

bioRxiv2024

Competition and cooperation: The plasticity of bacteria interactions across environments

Bacteria live in diverse communities, forming complex networks of interacting species. A central question in bacterial ecology is why some species engage in cooperative interactions, whereas others compete. But this question often neglects the role of the environment. Here, we use genome-scale metabolic networks from two different open-access collections (AGORA and CarveMe) to assess pairwise interactions of different microbes in varying environmental conditions (provision of different environmental compounds). By scanning thousands of environments for 10,000 pairs of bacteria from each collection, we found that most pairs were able to both compete and cooperate depending on the availability of environmental resources. This approach allowed us to determine commonalities between environments that could facilitate the potential for cooperation or competition between a pair of species. Namely, cooperative interactions, especially obligate, were most common in less diverse environments. Further, as compounds were removed from the environment, we found interactions tended to degrade towards obligacy. However, we also found that on average at least one compound could be removed from an environment to switch the interaction from competition to facultative cooperation or vice versa. Together our approach indicates a high degree of plasticity in microbial interactions to the availability of environmental resources.

microbiology↗

bioRxiv2024

Protected area establishment in Southern and Eastern Africa: Consequences for management today

To understand the complexities of managing protected areas, it is important to understand the causes for their established. We summarized the motives for establishing protected areas in Southern and Eastern Africa, and the possible consequences for management of these areas today. We scrutinised documents for 48 randomly selected protected areas and investigated, (1) when and why each of the protected areas was established? (2) what the management implications were of the reasons for incorporation for these areas? and (3) how/if the original management still impacts conservation in these areas today? First, we learnt that the establishment of protected areas occurred in three periods, namely, Period 1 when area protection was started to protect wild animals from decimation; Period 2 during which areas considered marginal for agriculture, prone to disease or sickness and considered uninhabitable for humans were set aside; and Period 3 when areas were proclaimed protected because of ecological or cultural importance. Second, we showed that the establishment of protected areas has ramifications for management of these areas today, which for Period 1 were remote logistics and tourism, anti-poaching difficulties, large size logistics and human wildlife conflict. Period 2 has consequences for community-land issues and intensive management, with Period 3 having intensive management to meet the objectives of these parks. Our insights have consequences for management of protected areas today, with Period 1 protected areas generally being managed on a laissez-faire approach and Period 2 and 3 protected areas being managed on a more intensive management basis.

ecology↗

bioRxiv2024

Provisioning polyethylene glycol (PEG) to large herbivores in nutrient poor savannas can break food limitation

Reproduction and survival of herbivores in nutrient poor savannas is low due to low nutrient and energy availability, partly caused by high levels of tannins. Polyethylene glycol (PEG) increases the availability of proteins for herbivores by binding tannins. The effect of PEG on the diet of free-roaming herbivores has not been tested. Our hypothesis was deploying lick blocks with the addition of PEG in a nutrient poor savanna, will result in a broadening of the diet of free-roaming herbivores with higher percentages of browse species and higher utilisation per browse species, with higher tannin levels. We further hypothesised that the mineral content in the faeces, once exposed to PEG would increase. We collected faecal samples of five herbivore species with various feeding methods (grazers, browsers or mixed feeders). The study used a Before-After-Control-Impact (BACI) design. The results show that the addition of PEG promotes a change in the browse dietary choices of four of the five herbivore species, and are expressed as a broader choice of diet, coupled with higher numbers of browse species with low edibility and higher tannin levels. The addition of PEG had no noteworthy effect on the concentration of minerals found in the faeces.

ecology↗

bioRxiv2024

Nutrient addition on grazing lawns and selection by free-roaming mammalian herbivores in a nutrient poor savanna

Grazing lawns are important food sources in nutrient poor savannas for free-roaming mammalian herbivores. It has been hypothesized that increased grazing pressure by mammalian herbivores can create and maintain patches of lawn grass. We tested whether the application of specific nutrients, nitrogen (N), phosphorus (P) or in combination with calcitic and dolomitic lime (Ca), in a nutrient poor African savanna, would make the grass sward more nutrient rich, which would attract mammalian herbivores to graze more frequently. We investigated the grazing patterns of six species of mammalian herbivores, namely, blue wildebeest (Connochaetes taurinus), Burchells zebra (Equus quagga burchellii), common eland (Taurotragus oryx), impala (Aepyceros melampus), square-lipped rhinoceros (Ceratotherium simum) and warthog (Phacochoerus africanus). We show that the addition of N attracts and increases the grazing pressure for three of the herbivore species, namely, blue wildebeest, Burchells zebra and impala. Our findings suggest that these often abundantly present mammalian herbivores with intermediate body mass, attracted to grazing lawns by the addition of N, can maintain grazing lawns. Conservation implicationsArtificial fertilization with nitrogen attracts large free-roaming herbivore species to localized grazing lawns, stimulating the creation and expansion of high nutrient quality lawn grasses in nutrient poor savannas. This results in a nutrient high food source which would normally not be available in nutrient poor savannas.

ecology↗

bioRxiv2024

Effects of mineral addition on the establishment of grazing lawns in a nutrient poor savanna

Nutrient poor savannas are often characterized by inedible or rarely palatable grasses, which generally provide poor nutrition for mammalian grazers. So-called grazing lawns, with short, stoloniferous edible grasses, could provide high-quality food for grazers, but these lawn grasses are rare in nutrient poor savannas. We tested whether we could use mineral addition to establish grazing lawns in a nutrient poor African savanna, in order to achieve a switch from tall, nutritionally poor to short, highly nutritional grass species. The key finding is that phosphorus and lime, nitrogen and nitrogen and lime supplementation resulted in shift from tall to short grasses within three years, with a higher overall nutrient concentration in the grass leaf, than without supplementation. When grazed, the cover of lawn grasses was higher compared to the other grasses when not grazed, demonstrating the role of grazers in maintaining and expanding lawn grass patches. We conclude that local fertilisation in nutrient poor savannas is a viable method of increasing mineral levels in the soil and grass leaf. We also concluded that grazing results in an increase in lawn grass cover and a combination of fertilisation and grazing can improve forage quality to ensure higher nutrient availability to herbivores.

ecology↗