Eric H. Harley

Reversible inhibition of intercellular junctional communication by glycyrrhetinic acid

Intercellular gap-junctional communication was measured using metabolic co-operation in co-cultures of argininosuccinate synthetase-deficient and argininosuccinate lyase-deficient human fibroblasts. 18-alpha-glycyrrhetinic acid (AGA) was found to inhibit communication by more than 95% at concentrations as low as 2 microM. Concentrations up to 100 microM were not cytotoxic over a period of 2 hours. Communication inhibition was of rapid onset and was readily reversible. Communication remained continuously yet reversibly blocked in cells cultured in the presence of AGA for 20 days. The related compounds 18-beta-glycyrrhetinic acid and carbenoxolone also caused communication inhibition. The effect is probably not mediated via mineralocorticoid or glucocorticoid receptors since aldosterone and glucocorticoids had no effect on communication. AGA thus has properties of a useful inhibitor in the study of intercellular junctional communication.

Strong population substructure is correlated with morphology and ecology in a migratory bat.

Examining patterns of inter-population genetic diversity can provide valuable information about both historical and current evolutionary processes affecting a species. Population genetic studies of flying and migratory species such as bats and birds have traditionally shown minimal population substructure, characterized by high levels of gene flow between populations. In general, strongly substructured mammalian populations either are separated by non-traversable barriers or belong to terrestrial species with low dispersal abilities. Species with female philopatry (the tendency to remain in or consistently return to the natal territory) might show strong substructure when examined with maternally inherited mitochondrial DNA, but this substructure generally disappears when biparentally inherited markers are used, owing to male-mediated gene flow. Male-biased dispersal is considered typical for mammals, and philopatry in both sexes is rare. Here we show strong population substructure in a migratory bat species, and philopatry in both sexes, as indicated by concordance of nuclear and mtDNA findings. Furthermore, the genetic structure correlates with local biomes and differentiation in wing morphology. There is therefore a close correlation of genetic and morphological differentiation in sympatric subspecific populations of this mammalian species.

Post‐bottleneck genetic diversity of elephant populations in South Africa, revealed using microsatellite analysis

Widespread hunting had fragmented and severely reduced elephant populations in South Africa by 1900. Elephant numbers increased during the 1900s, although rates of recovery of individual populations varied. The Kruger National Park elephant population increased rapidly, to more than 6000 by 1967, with recruitment boosted by immigration from Mozambique. The Addo Elephant National Park population was reduced to 11 elephants in 1931 and remains relatively small (n = 325). Loss of genetic variation is expected to occur whenever a population goes through a bottleneck, especially when post‐bottleneck recovery is slow. Variation at nine polymorphic microsatellite loci was analysed for Kruger and Addo elephants, as well as museum specimens of Addo elephants shot prior to the population bottleneck. Significantly reduced genetic variation and heterozygosity were observed in Addo in comparison to Kruger (mean alleles/locus and HE: Addo 1.89, 0.18; Kruger 3.89, 0.44). Two alleles not present in the current Addo population were observed in the museum specimens. Addo elephants represent a genetic subset of the Kruger population, with high levels of genetic differentiation resulting from rapid genetic drift. The Kruger population is low in genetic diversity in comparison to East African elephants, confirming this population also suffered an appreciable bottleneck.

Polyphyly of Arundinoideae (Poaceae): Evidence from rbcL Sequence Data

Sequence data from the plastid encoded gene rbcL are used to determine phylogenetic relationships between various lineages in the grasses, with particular emphasis on the subfamily Arundinoideae. Thirty four sequences, producing 155 phylogenetically informative sites, were analysed using both parsimony and distance methods. Cladistic analyses indicate that there are two main lineages: Pooideae (including the Stipeae) and a large clade comprising Panicoideae, Arun- dinoideae, Chloridoideae, and Centothecoideae. The Bambusoideae are unresolved and basal to these two lineages. Relationships within the panicoid, arundinoid, chloridoid, and centothecoid clade indicate that Arundinoideae as presently circumscribed are paraphyletic, as lineages within this subfamily show affinities with all three of the other subfamilies. Despite poor support for some relationships, rbcL appears to be well suited for systematic studies in the Poaceae.

GENETIC AND PHENOTYPIC DIFFERENCES BETWEEN SOUTH AFRICAN LONG-FINGERED BATS, WITH A GLOBAL MINIOPTERINE PHYLOGENY

Abstract The Natal long-fingered bat (Miniopterus natalensis) and lesser long-fingered bat (M. fraterculus) are morphologically almost indistinguishable and occur sympatrically over much of their southern African range. This raises the possibility that they are sister taxa. We employed a multidisciplinary approach to examine their taxonomic relationship to one another and to other Miniopterus species, whose global phylogeny requires review. We examined echolocation, morphological, and dietary differences between M. natalensis and M. fraterculus, as well as both nuclear and mitochondrial DNA variation between them in the context of a phylogeny incorporating 13 Miniopterus species and subspecies. Despite similarities in their morphology and distribution, M. natalensis and M. fraterculus echolocate at peak frequencies separated by 12 kHz, and both nuclear and mitochondrial DNA markers confirm they are distinct species. Analysis of cytochrome-b (Cytb) sequences further indicates that M. fraterculus and M. natalensis are not sister taxa; M. fraterculus appears to be more closely related to the greater long-fingered bat (M. inflatus). Examination of the global taxonomy of Miniopterus confirms that Schreiberss long-fingered bat (M. schreibersii) forms a paraphyletic species complex. Furthermore, the miniopterine bats are divided into 2 geographically isolated monophyletic groups, one containing African and European species, and the other taxa from Australasia and Asia. Cytb sequence divergence also suggests that M. natalensis is distinct from the European M. schreibersii. These results support the elevation of M. natalensis to full species rank.

The electrophoretic mobility of double-stranded RNA in polyacrylamide gels as a function of molecular weight

A re-evaluation of the mobility of double-stranded RNA on polyacrylamide gels over a molecular weight range of 0.46-6.3 . 10(6) was carried out using double-stranded RNAs of: bacteriophage ø6; virus like particles or mycoviruses of Penicillium chyrsogenum, Penicillium stoloniferum and Helminthosporium maydis, and reovirus type III. When the relative mobility on polyacrylamide gels was plotted as a function of log molecular weight, a smooth curve could be drawn which passed through all points. The implications of these findings to the determination of molecular weight of double-stranded RNA by polyacrylamide gel electrophoresis are discussed.

Genetic variation and population structure in remnant populations of black rhinoceros, Diceros bicornis, in Africa.

Black rhinoceros (Diceros bicornis) are one of the most endangered mammal species in Africa, with a population decline of more than 96% by the end of the last century. Habitat destruction and encroachment has resulted in fragmentation of the remaining populations. To assist in conservation management, baseline information is provided here on relative genetic diversity and population differentiation among the four remaining recognized subspecies. Using microsatellite data from nine loci and 121 black rhinoceros individuals, and comparing the results with those of other African species affected in similar ways, Diceros bicornis michaeli retained the most genetic diversity (heterozygosity 0.675) compared with Diceros bicornis minor (0.459) and Diceros bicornis bicornis (0.505), suggesting that the duration of the known bottlenecks in these populations has only had a limited impact on diversity. Comparable and moderate degrees of population differentiation were found between D. b. minor, D. b. bicornis and D. b. michaeli. Results from the single sample available of the most endangered subspecies, Diceros bicornis longipes, showed the least diversity of all individuals examined. This information should assist conservation management decisions, especially those affecting population viability assessments and selection of individuals for translocations, and will also facilitate subspecies identification for ex situ individuals of uncertain origin.

Phylogenetic relationships in Disa based on non-coding trnL-trnF chloroplast sequences: evidence of numerous repeat regions

Sequence data from the intron and spacer of the trnL-F chloroplast region elucidate the phylogenetic relationships of the tribe Diseae (Orchidoideae: Orchidaceae). Within Diseae, 41 species of Disa, two of Brownleea, three of Satyrium, and two of Corycium were included, with five species of Habenaria sensu lato (Orchideae) and one epidendroid as outgroups. The sequences revealed substitutions and considerable length variation, due mainly to the presence of repeat motifs. Phylogenetic analysis using parsimony revealed five distinct clades. The branching order of the five weakly supported the paraphyly of Diseae, with the successive divergence of Brownleea, Corycium, Habenaria, Satyrium, and Disa. Within the monophyletic Disa, three main groupings appeared, two strongly supported clades representing sect. Racemosae and sect. Coryphaea and the third grouping containing several clades currently grouped into sections based on morphological phylogenies. Some discrepancies between the molecular phylogeny and the phylogeny based on morphological characters may require reevaluation of some of the morphological characters. The presence of different numbers of repeat motifs, both among different taxa and within taxa, indicates that these characters may be phylogenetically informative at the population level.

Isolation and characterization of microsatellite loci in black rhinoceros (Diceros bicornis)

The black rhinoceros (Diceros bicornis) is currently one of the most endangered African mammals as a direct result o habitat destruction and intensive poaching. A microsatellite library was constructed to address a number of population genetic questions. This paper describes the isolation of five black rhinoceros microsatellite loci. Three of these loci were found to be polymorphic. In addition, the paper demonstrates the utility for cross‐hybridization of these primers in other species of rhinoceros.

Investigation of genetic diversity in fragmented geometric tortoise (Psammobates geometricus) populations

Microsatellite DNA was used to investigatelevels of genetic variability in severelyfragmented populations of the geometrictortoise, Psammobates geometricus, themost endangered tortoise on mainland Africa.Eight microsatellite markers were used toassess genetic variability within and betweenthree naturally occurring populations of P. geometricus. These populations areseparated by the Cape Fold mountain ranges inthe western Cape region of South Africa. Levels of variability were quantified usingallelic diversity, genotypic frequencies andheterozygosity. Evidence for populationsub-structuring was examined using Fstatistics, Rst and δμ2.High levels of variability were found in allthree populations. Low levels of populationdifferentiation were found suggestingsignificant gene flow between the populations.