No abstract

o effectively conserve and manage species, it is important to (1) understand how they are spatially distributed across the globe at both broad and fine spatial resolutions and (2) elucidate the determinants of these distributions. However, information pertaining to the distributions of many species remains poor as occurrence data are often scarce or collected with varying motivations, making the resulting patterns susceptible to sampling bias. Exacerbating an already limited quantity of occurrence data with an assortment of biases hinders their effectiveness for research, thus making it important to identify and understand the biases present within species occurrence data sets. We quantitatively assessed occurrence records of 126 reptile species occurring in the Kruger National Park (KNP), South Africa, to quantify the severity of sampling bias within this data set. We collated a data set of 7118 occurrence records from museum, literature and citizen science sources and analysed these at a biologically relevant spatial resolution of 1 km × 1 km. As a result of logistical challenges associated with sampling in KNP, approximately 92% of KNP is data deficient for reptile occurrences at the 1 km × 1 km resolution. Additionally, the spatial coverage of available occurrences varied at species and family levels, and the majority of occurrence records were strongly associated with publicly accessible human infrastructure. Furthermore, we found that sampled areas within KNP were not necessarily ecologically representative of KNP as a whole, suggesting that areas of unique environmental space remain to be sampled. Our findings highlight the need for substantially greater sampling effort for reptiles across KNP and emphasise the need to carefully consider the sampling biases within existing data should these be used for conservation management decision-making. Modelling species distributions could potentially serve as a short-term solution, but a concomitant increase in surveys across the park is needed.Conservation implications: The sampling biases present within KNP reptile occurrence data inhibit the inference of fine-scale species distributions within and across the park, which limits the usage of these data towards meaningfully informing conservation management decisions as applicable to reptile species in KNP.

1. Invasions by non-native species can compromise the conservation value of otherwise pristine headwater streams. While both developed and developing countries recognize this threat, few of the latter have suitable budgets to implement control programmes. 2. This study assessed the effectiveness of a mechanical project to remove non-native rainbow trout Oncorhynchus mykiss from a 6 km section of the upper Krom River, a small headwater stream in the Cederberg Mountains in South Africa's Cape Floristic Region (CFR). 3. From October 2013 to February 2014, 354 O. mykiss were removed by angling (58%), fyke netting (28%) and gill netting (14%). This resulted in a marked reduction, but not eradication, of the O. mykiss population (fish relative abundance decreased from 0.53 ± 0.09 fish per net per night in October 2013 to 0.21 ± 0.09 fish per net per night in February 2014). Following the cessation of manual removals, the relative abundance of O. mykiss had increased to 0.56 ± 0.18 fish per net per night by March 2016, suggesting that without sustained removal effort, the population will rapidly return to its pre-removal abundance level. 4. Further work is needed to refine the methodology and test the effectiveness of mechanical removal of non-native freshwater fish in a variety of ecological settings in the CFR. This approach holds potential for meeting the dual goals of reducing the ecological impacts of non-native fishes and generating employment opportunities in line with the policy objectives of developing nations.

Acacia mearnsii is an introduced Australian acacia in South Africa and has invaded more than 2.5 million ha, primarily establishing in rangeland and riparian areas. Because acacias have the capability to fix N, A. mearnsii invasions may fundamentally change N dynamics in invaded systems. This study compares biological N 2 -fixation in the alien invasive A. mearnsii and the native A. caffra growing in a grassland riparian zone in the Komati Gorge Reserve, Mpumalanga, South Africa. A 15 N natural abundance field survey suggested that both mature alien and native acacias fix N under current conditions in the riparian zone. Significantly depleted d 15 N was observed in both acacias relative to reference species, although variation in d 15 N was not correlated with N concentrations. Calculated contributions of N 2 -fixation (%Ndfa) suggest that alien acacias fix significantly more of their N than native acacias (*75 ± 5% SE and 53 ± 9% SE, respectively). There was a larger variation in d 15 N and %Ndfa in the native acacia, suggesting relatively high plasticity in its N 2 -fixation contributions. This plasticity was interpreted as a facultative N 2 -fixation strategy for the native acacia, while the N 2 -fixation strategy of the alien acacia remained unclear. Our results emphasize the importance of potentially elevated N inputs through N 2 -fixation by invasive legumes in invaded landscapes. Furthermore, they suggest that N 2 -fixation by invasive acacias may not respond to fine-scale patchiness in soil N in the same manner as native acacias, making them potential contributors to N excess in Southern Africa.