Demographic consequences of habitat loss and crowding in large carnivores: A natural experiment

Habitat loss is one of largest threats to the persistence of large carnivore populations. However, because most large carnivores are long‐lived, cryptic and wide‐ranging, few studies examine the demographic consequences of habitat loss, and the resultant crowding that ensues, on these species. We used long‐term data to examine the demographic responses of an African lion (Panthera leo) population to flooding‐induced habitat loss in a seasonal wetland, the Okavango Delta, during a transition from low to high annual flooding patterns. We found that intraspecific competition reduced cub survival and that this effect was exacerbated by habitat loss and consequent crowding. The proportion of cubs recorded in the population also declined as crowding increased, and both the survival of cubs and proportion of cubs recorded declined as prey abundance decreased. Apparent sub‐adult survival declined with increasing pride size, but this likely reflects emigration rather than mortality. Adult survival remained relatively constant throughout the study period, a population response which is important in buffering populations against short‐term fluctuations in ecological conditions. As many large carnivore populations face future habitat loss, it is important that we understand the demographic consequences of habitat loss in order to better mitigate its effects in the future.     

Forty years of carabid beetle research in Europe - from taxonomy, biology, ecology and population studies to bioindication, habitat assessment and conservation

‘Carabidologists do it all’ (Niemelä 1996a) is a phrase with which most European carabidologists are familiar. Indeed, during the last half a century, professional and amateur entomologists have contributed enormously to our understanding of the basic biology of carabid beetles. The success of the field is in no small part due to regular European Carabidologists’ Meetings, which started in 1969 in Wijster, the Netherlands, with the 14th meeting again held in the Netherlands in 2009, celebrating the 40th anniversary of the first meeting and 50 years of long-term research in the Dwingelderveld. This paper offers a subjective summary of some of the major developments in carabidology since the 1960s. Taxonomy of the family Carabidae is now reasonably established, and the application of modern taxonomic tools has brought up several surprises like elsewhere in the animal kingdom. Progress has been made on the ultimate and proximate factors of seasonality and timing of reproduction, which only exceptionally show non-seasonality. Triggers can be linked to evolutionary events and plausibly explained by the “taxon cycle” theory. Fairly little is still known about certain feeding preferences, including granivory and ants, as well as unique life history strategies, such as ectoparasitism and predation on higher taxa. The study of carabids has been instrumental in developing metapopulation theory (even if it was termed differently). Dispersal is one of the areas intensively studied, and results show an intricate interaction between walking and flying as the major mechanisms. The ecological study of carabids is still hampered by some unresolved questions about sampling and data evaluation. It is recognised that knowledge is uneven, especially concerning larvae and species in tropical areas. By their abundance and wide distribution, carabid beetles can be useful in population studies, bioindication, conservation biology and landscape ecology. Indeed, 40 years of carabidological research have provided so much data and insights, that among insects - and arguably most other terrestrial organisms - carabid beetles are one of the most worthwhile model groups for biological studies.     

Management of hybridization in an endemic species: decision making in the face of imperfect information in the case of the black wildebeest—<Emphasis Type="Italic">Connochaetes gnou</Emphasis>

Hybridization between introduced and endemic ungulates, resulting from anthropogenic actions, has been reported for several species. Several studies of such events contain the common themes of extralimital movements, problematic phenotypic and genetic detection, and imperfect management. In southern Africa, the endemic black wildebeest (Connochaetes gnou) currently faces a serious threat of hybridization and introgression. This species survived near extinction and consequent genetic bottlenecks in the late 1800s and in the 1930s. Initiatives by private farmers followed by conservation authorities led to a dramatic recovery in numbers of this species. However, in an ironic twist, the very same advances in conservation and commercial utilisation which led to the recovery of numbers are now themselves threatening the species. Injudicious translocation has brought the species into contact with its congener, the blue wildebeest (Connochaetes taurinus), and in recent times, hybridization between the species has occurred at numerous localities in South Africa. Consequently, a significant proportion of the national black wildebeest population potentially carries a proportion of introgressed blue wildebeest genetic material. We discuss completed and ongoing attempts to find molecular markers to detect hybrids and highlight the difficulty of detecting advanced backcrosses. Additional avenues of research, such as work on morphology (cranial and postcranial elements), estimating of the probability of introgression and modelling of diffusion rates are also introduced. In addition to the difficulty in detecting hybrid animals or herds, the lack of consensus on the fate of hybrid herds is discussed. Finally, in an environment of imperfect information, we caution against implementation of management responses that will potentially induce a new genetic bottleneck in C. gnou.     

The effect of egg embryonation on field-use of a hookworm benzimidazole-sensitivity egg hatch assay in Yunnan Province, People's Republic of China

Background

Current efforts to control human soil-transmitted helminths (STHs) involve the periodic mass administration of benzimidazole drugs to school aged children and other at- risk groups. Given that high levels of resistance to these drugs have developed in roundworms of livestock, there is a need to monitor drug efficacy in human STHs. The current study aimed to evaluate an in vitro egg hatch assay for measuring the sensitivity of human hookworms to benzimidazole drugs in an isolated field setting in southern Yunnan province, People''s Republic of China.

Methodology/Principal Findings

Egg hatch assays were performed with hookworm (Necator americanus) eggs extracted from 37 stool samples received from local school-aged children. The mean IC₅₀ was 0.10 ug/ml thiabendazole (95% CIs: 0.09–0.12 ug/ml). Observation of the eggs immediately prior to assay set-up revealed that a small percentage had embryonated in some samples. Scoring of % embryonation of eggs prior to the assay allowed for corrections to be made to IC₅₀, IC₉₅ and IC₉₉ values. Examination of the data with and without this correction revealed that the embryonation of a small number of eggs did not affect IC₅₀ values, but did increase IC₉₅ and IC₉₉ values for some samples.

Conclusions/Significance

This study has highlighted the impact of egg embryonation on the use of benzimidazole drug sensitivity assays for human hookworms in field settings. Given the greater flexibility required in human stool collection procedures compared to livestock studies, we suggest that embryonation of some eggs may be an unavoidable issue in some human studies. Hence, it needs to be measured and accounted for when analysing dose response data, particularly for generation of IC₉₅ and IC₉₉ values. The protocols used in this study and our suggested measures for accounting for egg embryonation should have widespread application in monitoring benzimidazole sensitivity at field sites worldwide.     

Survival and Population Dynamics of the Marabou Stork in an Isolated Population,Swaziland

Investigating the ecology of long lived birds is particularly challenging owing to the time scales involved. Here an analysis is presented of a long term study of the survival and population dynamics of the marabou stork (Leptoptilos crumeniferus), a wide ranging scavenging bird from Sub-Saharan Africa. Using resightings data of tagged nestlings and free flying birds we show that the stork population can be divided into three general life stages with unique survival probabilities and fecundities. Fecundity of the storks is inversely related to rainfall during their breeding season. Corroborative evidence for a metapopulation structure is discussed highlighting the impact of the Swaziland birds on the ecology of the species in the broader region. The importance of tag loss or illegibility over time is highlighted. Clearly, any attempt at conserving a species will require a detailed understanding of its population structure, of the sort examined here.     

Forest edge contrasts have a predictable effect on the spatial distribution of carabid beetles in urban forests

Fragmented urban forest remnants are characterised by sharp edges and are bordered by various land-use types, which may have a considerable effect on the fauna and flora at forest edges, and into forest interiors. To investigate the effects of differentially contrasting edges (low vs. intermediate vs. high) on carabid beetle assemblages in urban boreal forests, we placed pitfall traps along a gradient from 6?m into three matrix types (secondary forest vs. grassland vs. asphalt) up to 60?m into urban forest patches in the cities of Vantaa and Helsinki, southern Finland. Individual species and carabid beetle assemblages were strongly affected by edge contrasts and distance from the forest edge. The strongest effect on individual species was caused by high contrasting edges: generalist and open-habitat species were favoured or not affected while forest specialists were affected negatively. Effects of the abundances of potential prey and competitors on the carabid beetles were also evaluated. Forest and moisture-associated carabid species were negatively to neutrally associated with springtail abundances while generalist and open habitat, and dryness associated species were more positively related to springtail abundances (a potential food source). In terms of potential competitors, forest and moisture-associated carabid species were negatively and/or neutrally affected by ant and wood ant numbers, while generalist and open-habitat species were neutrally to positively associated with these taxa. It appears that carabid beetle habitat associations are more important in the responses of these beetles across edges of different contrast than are the prey and competitor numbers collected there. We recommend the creation of “soft” or low-contrast urban edges if the aim of urban management is to protect forest carabids in cities.     

Wetland Plant Species Used for Craft Production in Kwazulu–Natal,South Africa: Ethnobotanical Knowledge and Environmental Sustainability

Wetland Plant Species Used for Craft Production in Kwazulu–Natal, South Africa: Ethnobotanical Knowledge and Environmental Sustainability. In KwaZulu–Natal Province, there is a rich tradition of wetland plant utilization for craft production. A survey of the province, based on interviews and participatory field walks, revealed which wetland plant species are harvested and how the different species are used. The principal plant species utilized varied greatly among regions: In the coastal region it was Cyperus latifolius Poir. (iKhwane) and Juncus kraussii Hochst. (iNcema), whereas in the uplands it was Cyperus marginatus Thunb. (iNcema). The initial hypothesis that the diversity of plant morphologies added to the diversity of different weave types and products was confirmed by the data. Plant morphological characteristics influenced the weaving techniques suitable for craft production. For example, the fine culms of J. kraussii and C. marginatus have particular value for twilling, twining, and straight sewing and the robust C. latifolius leaves are well suited for the plait. Pressures on the supply of the natural resource were greatest from competing land uses, such as wetland cultivation and, to a lesser extent, from competition among plant harvesters. There was a high demand for J. kraussii, which is traded beyond the limits of its geographical distribution to a much greater extent than the other species. The paper concludes by recommending the wider application of the approach and methods used in the study in order to inform initiatives promoting small business development based upon sustainably harvested natural resources.     

Effects of cyromazine on reproduction and offspring development in Lucilia cuprina (Diptera: Calliphoridae).

The effects of cyromazine on reproduction and subsequent hatch and larval developmental in Lucilia cuprina (Wiedemann) were examined by feeding the compound in water to adult flies at concentrations up to 100 ppm. Cyromazine did not interfere with oviposition or hatch; however, subsequent larval development was strongly inhibited in a concentration-dependent manner.     

The occurrence and distribution of carabid beetles (Carabidae) on islands in the Baltic Sea: a review

The distribution and occurrence of carabid beetles have been studied extensively in a number of archipelagoes in the Baltic Sea, a ca. 377,000 km², fairly shallow and young sea in northern Europe. This work has revealed some surprising results related to colonisation success and maintenance of populations. Dispersal from the mainland and between islands appears to be relatively easy because inter-island distances are small (tens or hundreds of metres) and the salinity of the Baltic is low, which allows survival during drift. This is reflected in the higher than expected proportion of brachypterous species on small islands. A lack of energetically expensive wings, flight muscles and flight fuel may give brachypterous species an advantage - in terms of resource allocation for survival and fecundity - over macropterous species in the colonisation of an island. Once an island is reached, successful colonisation mainly depends on the presence of suitable habitat. The most abundantly collected carabids on these islands are habitat generalists, but some degree of habitat association exists. Yet, the composition of carabid assemblages differs substantially among islands, possibly a result of chance effects. There is evidence that species on smaller islands occur in a wider variety of vegetation types than species on larger islands. Both habitat diversity and area per se are implicated in the positive species-area relationships found, but the small island effect has been identified as being significant in most of the archipelagoes investigated. Pterostichus melanarius, a eurytopic, wing-polymorphic species abundantly collected on the mainland is, unexpectedly, absent from small islands. Possible reasons for this include; (1) interspecific predation and competition for food by the closely related but slightly larger P. niger, which is dominant on small islands, (2) the apparent inability of P. melanarius to reproduce on small islands, (3) its reduced dispersal power as compared to P. niger and (4) the possible absence of some essential resources from small islands. In conclusion, the conservation value of highly threatened cultural landscapes on Baltic Sea islands, such as species rich wooded meadows, is discussed as well as the possible negative effects of climate change on carabid beetles.