No abstract

1. The relationship between coarse particulate organic matter (CPOM) standing stock and benthic macroinvertebrate assemblages in Kenyan highland streams was determined by sampling seven sites on three rivers (2000–2700 m a.s.l.). Taxa recorded were allocated to functional feeding groups using published literature, mouthpart analysis and examination of gut contents. Patterns were compared with five structurally similar streams in three areas of Europe (south‐west France, south‐east England, north‐east England). 2. Number of individuals and proportion of detritivores in Kenyan streams were equivalent to, or greater than, those in European sites. Shredders were, however, almost completely absent from Kenyan sites, despite high standing stocks of CPOM. Shredders were abundant in all European sites. 3. The phenomenon of low shredder abundance has been observed in other tropical streams in south‐east Asia and Central and South America but, in contrast to these regions, the African rivers studied were devoid of shrimps or fish which may occupy the shredding niche elsewhere. 4. These preliminary data suggest that shredder‐mediated detritus processing, which is a key functional component of streams in the North Temperate Zone, does not operate in East African streams. There are three possible reasons for this. The first is that tropical African rivers are functionally different to those in temperate regions. This could be because of enhanced microbial activity replacing shredder activity at high temperatures. Alternatively, it could be a result of low palatability of detrital inputs from dominant riparian trees in the region. The second and third are methodological: that our allocation to functional feeding groups is incorrect, and that our sampling methods missed a potentially key shredding taxon – the freshwater crab Potamonautes sp.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. The retention characteristics of stretches of four low order streams in south-east England were manipulated over a period of 2 years by the addition of small traps which accumulated leaf litter. Unmanipulated control stretches were retained in each stream. Our aim was to test the prediction that the local density of 'shredders', invertebrates which comminute autumn-shed leaves, would increase in response to leaf litter availability. One stream naturally retained a high leaf litter biomass, two had few natural leaf packs and one was intermediate. After manipulation had begun, simultaneous samples of the benthos and leaf litter were taken from control stretches and the traps and intervening stream bed ('intertraps') in the manipulated stretches.3. The effects of manipulation were slight in the highly retentive site, in terms of both litter standing stock and shredder abundance. The other three sites showed rapid responses, with increased leaf litter and shredder abundance in traps compared with controls. 4. In the least retentive site, manipulation significantly increased the biomass of coarse particulate organic matter in the intertrap samples. In one other site, there was also an increase in shredder density in the intertraps. 5. The changes associated with manipulation were consistent despite the differences in pH among streams, which determined the species assemblage of shredders at each site, but not the pattern of response to increased retention. 6. The results indicate that resource limitation may occur among mobile detritivorous invertebrates in low-order streams. The nature of the limiting resource is discussed; it is speculated that leaf litter may be limiting as a habitat for shredders as well as a source of food.

The natural distribution of the 17 non‐flying mammal species occurring wild in both the Maghreb (north‐west Africa) and Iberia (south‐west Europe) is considered. It is concluded that only four species – Red Fox Vulpes vulpes, Wild Boar Sus scrofa, Wild Cat Felis silvestris and Otter Lutra lutra – are native to both regions, while another three – Red Deer Cervus elaphus, Brown Bear Ursus arctos and Aurochs Bos primigenius – were native to North Africa until the mid‐Holocene but have probably died out naturally. Algerian Hedgehog Atelerix algirus, Barbary Ape Macaca sylvanus, Genet Genetta genetta and Egyptian Mongoose Herpestes ichneumon are widely accepted as introductions to Europe from North Africa. The remaining six species, and Red Deer now found in Africa, were also probably introduced – Rabbit Oryctolagus cuniculus, Weasel Mustela nivalis, Wood Mouse Apodemus sylvaticus and Lesser White‐toothed Shrew Crocidura russula from Europe to Africa; Algerian Mouse Mus spretus from Africa to Europe; Savi’s Pygmy Shrew Suncus etruscus perhaps from the eastern Mediterranean to both Iberia and the Maghreb. There are two Maghrebi species which, although not found in Europe, are more closely related to Palaearctic than to Afrotropical species: Garden Dormouse Eliomys melanurus, probably native to north‐west Africa, although possible augmentation of the natural population cannot be ruled out, and Whitaker’s Shrew Crocidura whitakeri, a North African endemic. Removal of so many species of European provenance from the list of mammals native to north‐west Africa should not be considered to weaken its position as part of the Palaearctic zoogeographical region. Bats and other, non‐mammalian, taxa illustrate the clear faunal relationship between the Maghreb and south‐west Europe, whilst emphasizing its distinction from subsaharan Africa.

Background Radical surgery via total mesorectal excision might not be the optimal first-line treatment for early-stage rectal cancer. An organ-preserving strategy with selective total mesorectal excision could reduce the adverse effects of treatment without substantially compromising oncological outcomes. We investigated the feasibility of recruiting patients to a randomised trial comparing an organ-preserving strategy with total mesorectal excision.Methods TREC was a randomised, open-label feasibility study done at 21 tertiary referral centres in the UK. Eligible participants were aged 18 years or older with rectal adenocarcinoma, staged T2 or lower, with a maximum diameter of 30 mm or less; patients with lymph node involvement or metastases were excluded. Patients were randomly allocated (1:1) by use of a computer-based randomisation service to undergo organ preservation with short-course radiotherapy followed by transanal endoscopic microsurgery after 8-10 weeks, or total mesorectal excision. Where the transanal endoscopic microsurgery specimen showed histopathological features associated with an increased risk of local recurrence, patients were considered for planned early conversion to total mesorectal excision. A non-randomised prospective registry captured patients for whom randomisation was considered inappropriate, because of a strong clinical indication for one treatment group. The primary endpoint was cumulative randomisation at 12, 18, and 24 months. Secondary outcomes evaluated safety, efficacy, and health-related quality of life assessed with the European Organisation for Research and Treatment of Cancer (EORTC) QLQ C30 and CR29 in the intention-to-treat population. This trial is registered with the ISRCTN Registry, ISRCTN14422743.