We examined the breeding system, reproductive output and pollination ecology of Abronia ammophila Greene, a rare and highly restricted endemic of Yellowstone National Park, Wyoming, USA. Floral morphology permits the automatic deposition of self-pollen on the stigma of individual flowers, and male and female reproductive functions temporally overlap. In controlled hand-pollination treatments, we found no significant difference among pollination treatments (unmanipulated, self-pollinated or cross-pollination). The species maintains a long reproductive season with high reproductive output (natural seed set ranged from 59 to 84%). Our results, along with pollinator observations, suggest that A. ammophila exhibits a mixed-mating system: the species can produce seed without pollinators (via either autogamy or agamospermy), but is also visited by an array of pollinating insects that included moths, butterflies and bumblebees. However, noctuid moths were the most abundant pollinators. In contrast, other Abronia species are obligate outcrossers. The mixed-mating system of A. ammophila may have evolved as a consequence of ecological pressures such as scarcity of mates or pollinators.

Summary1 Niche pre-emption and competitive exclusion is unsatisfactory as a sole explanation for the apparent paradox of a large number of monophyletic taxa in the Macaronesian island flora. 2 Undetected hybridizations have been proposed as an additional plausible explanation. In addition, hybrid swarm theory predicts that hybridizations between invading species would promote adaptive radiation. 3 We suggest that branching processes and coalescence offer yet another plausible explanation allowing for multiple colonizations of closely related taxa, which, because of their later local extinction or hybridization, would lead to apparent monophyly in the molecular record. 4 The cause of such widespread radiation of a few taxa has not been explained, but may involve intermediate conditions of disturbance or productivity. This proposition has, to date, only been tested in a microbial model system, but it offers a reasonable explanation for the patterns observed in the Macaronesian flora, and perhaps in other island floras worldwide. In his Forum article (The ghost of competition past in the phylogeny of island endemic plants), Silvertown (2004a) proposes two hypotheses to explain why many/ most Macaronesian endemic groups are monophyletic: either new recruits cannot get to islands easily (clearly not the case for Macaronesia), or interspecific competition or niche pre-emption prevents later recruits of closely related species from establishing. We welcome this approach as it provides an ecological explanation for an observed evolutionary pattern. Nevertheless, at the heart of Silvertown's hypothesis is the idea that each monophyletic lineage currently present on the Macaronesian Islands arrived in a single colonizing event shortly after the islands' genesis. He proposes that, by primacy of establishment, the initial colonizers were able to shut out closely related species (intrageneric taxa) through the mechanisms of competitive exclusion and niche pre-emption. Without the assumption of a single colonizing event to account for each monophyletic lineage, the mechanisms of competitive exclusion and niche pre-emption are without merit. Herben et al . (2005) (HSM thereafter) offer past hybridization of closely related colonists as a plausible explanation, additional to the niche pre-emption hypothesis offered by Silvertown (2004a). Here we offer additional observations on HSM's argument, which we find convincing, and on other points related to breeding system, branching processes and coalescent theory, hybrid swarm theory and the ecological constraints on adaptive radiation. Together, these persuade us that niche pre-emption may be a likely explanation, but is certainly not the only one, for the patterns observed by Silvertown (2004a). Key-words

As the quality of water in dialysis fluid varies considerably, dialysate is often contaminated by large amounts of bacteria and endotoxins. Membrane properties and operating pressures are acknowledged to give high-flux dialysis with bicarbonate the bacteriological potential to favor passage of endotoxin fragments from the dialysate into the blood stream. Therefore, a sterile dialysate will have to become a standard. Ultrafiltration across hydrophobic synthetic membranes was shown to remove endotoxins (and their fragments) from dialysis water by the combined effect of filtration and adsorption. However, each module can be used for a limited time only. Ceramic membranes may represent an alternative to polymeric membranes for endotoxin removal. In this article, we tested the capacity of different commercial ceramic membranes with nominal molecular weight cut-off down to 1,000 to retain endotoxins from Ps. aeruginosa. The tested membranes did not generally produce dialysate meeting the Association for the Advancement of Medical Instrumentation standard. When using aluminum-containing membranes, we detected aluminum leaking into the dialysate that could possibly be transported into the blood stream.

Abstract. Personal computers of ever‐increasing speed have motivated programmers of multivariate software to adapt their programs to be run in Microsoft Windows and Macintosh platforms. Updated versions of these multivariate programs appear more and more frequently and are marketed intensively. In this review we provide a comparative analysis of the most recent versions of three analytical software packages –Canoco for Windows 4.5, PC‐ORD version 4 and SYN‐TAX 2000. The three packages share two characteristics. First, the most recent versions are now compatible with the most recent Windows platforms and should therefore be accessible for use by virtually all vegetation scientists. Second, they have capabilities for numerous multivariate techniques, although each package has some unique techniques. Thus, any one of the packages will have much to offer the user.

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