Biogeography of soil nematodes

Biogeography is the study of distributions of organisms, plus an attempt to explain the distributions. Two approaches to explanation of biogeographic patterns may be termed ecological biogeography and historical biogeography. Most nematologists have taken the ecological approach, with a goal of determining why a particular species is restricted to certain areas, and not present in nearby areas. Historical biogeography is based on the premise that present-day patterns of taxa result largely from the history of the taxa and of the areas of the earth in which they have lived. Nematologists generally adhere to the classic view of dispersal in which a center of origin is postulated and long-range dispersal over barriers is invoked. The dispersal mechanism is often assumed to be man himself. Challenges to this approach exist in the form of methods which infer the biogeographic history from phylogeny. Vicariance biogeographers postulate fragmentation of widespread ancestral biotas, resulting from geological, climatic or other disjunctions, and further allopatric speciation among descendant biotas. Distributions amenable to general explanation can be distinguished from those which require unique dispersal events. Biogeography of soil nematodes is hampered by present limitations in systematics, including our inability to determine species limits with certainty.     

Direct fetal chromosome studies from chorionic villi

An easy and reproducible technique for direct fetal chromosome analysis after chorionic biopsy is described. Very high colchicine concentration and rehydratation of the fixed villi are the two original points of this method.     

The cerebro-hepato-renal (Zellweger) syndrome: Prenatal detection based on impaired biosynthesis of plasmalogens

Prenatal diagnosis of the cerebro-hepato-renal (Zellweger) syndrome has been performed in 10 pregnancies at risk by measuring both the activity of acyl CoA: dihydroxyacetonephosphate acyltransferase (DHAP-AT) and the de novo plasmalogen biosynthesis, either in cultured amniotic fluid cells or in fibroblasts cultured from a chorionic villus biopsy. In 7 of the pregnancies both tests indicated no abnormality. All 7 continued to term and normal infants were delivered. However, in amniotic fluid cells from 2 fetuses affected by Zellweger syndrome unequivocal differences from control values were found. The activity of DHAP-AT was clearly deficient and the de novo plasmalogen biosynthesis was impaired. In one pregnancy at risk prenatal diagnosis was performed during the first trimester by measuring both the DHAP-AT activity and the de novo plasmalogen biosynthesis in fibroblasts cultured from a chorionic villi biopsy. From the deficient DHAP-AT activity and the impaired de novo plasmalogen biosynthesis it was concluded that the fetus was affected. This was confirmed biochemically after induced abortion. It can be concluded that measurement of the DHAP-AT activity and the de novo plasmalogen biosynthesis provides convenient methods for the early prenatal detection of Zellweger syndrome.     

Expedient Metrics to Describe Plant Community Change Across Gradients of Anthropogenic Influence

Human influence associated with land use may cause considerable biodiversity losses, namely in oceanic islands such as the Azores. Our goal was to identify plant indicator species across two gradients of increasing anthropogenic influence and management (arborescent and herbaceous communities) and determine similarity between plant communities of uncategorized vegetation plots to those in reference gradients using metrics derived from R programming. We intend to test and provide an expedient way to determine the conservation value of a given uncategorized vegetation plot based on the number of native, endemic, introduced, and invasive indicator species present. Using the metric IndVal, plant taxa with a significant indicator value for each community type in the two anthropogenic gradients were determined. A new metric, ComVal, was developed to assess the similarity of an uncategorized vegetation plot toward a reference community type, based on (i) the percentage of pre-defined indicator species from reference communities present in the vegetation plots, and (ii) the percentage of indicator species, specific to a given reference community type, present in the vegetation plot. Using a data resampling approach, the communities were randomly used as training or validation sets to classify vegetation plots based on ComVal. The percentage match with reference community types ranged from 77 to 100 % and from 79 to 100 %, for herbaceous and arborescent vegetation plots, respectively. Both IndVal and ComVal are part of a suite of useful tools characterizing plant communities and plant community change along gradients of anthropogenic influence without a priori knowledge of their biology and ecology.