Studies on the frequency and associations of equine leucocyte antigens in sarcoid and summer dermatitis

The equine leucocyte antigen (ELA) types and the clinical diagnosis for equine sarcoid and summer dermatitis were evaluated in 2026 horses representing five breeds. Data were analysed in unrelated animals and in family material. In the case of equine sarcoid, a strong association was observed between the ELA class II DW13 antigen and its effect on Swiss (cP < 0·001), French (cP < 0·0001) and Irish (cP < 0·01) Warmblood horses. The class I antigen A3 occurred more frequently in sarcoid-affected French horses (cP < 0·001). These results confirm our earlier findings (Gerber et al. 1988). Among Freiberger horses, which lack the ELA DW13 and A3 specificities, a breed-specific class I antigen, ABe108, displayed an increased frequency (cP < 0·05) in the affected group. Among Arabian horses, a tendency for increased frequency of the A1 antigen was observed in the affected animals, but the number of affected horses is too small for statistical significance. The Mendelian segregation in diseased half-siblings by ELA DW13 heterozygous stallions showed a strong association (P < 0·0001) between the inherited DW13 antigen and susceptibility to the sarcoid effect. In the case of summer dermatitis, previously published data (Marti et al. 1992) have been extended. The ELA types in four multiple-case families, founded by the same stallion, were analysed for an association with the effect of sarcoid. Eight out of nine ELA-typed affected offspring inherited the paternal haplotype A15, DW23 in contrast to nonaffected offspring where three out of 12 displayed these antigens (P < 0·005). Moreover, the ELA haplotypes of 11 out of 12 informative affected half-siblings sired by another stallion inherited the paternal haplotype A3, W12, DW23 (P < 0·05). Our findings demonstrate statistically significant associations between certain ELA antigens and two equine diseases. It is still unknown if the major histocompatibility complex (MHC) molecules themselves or another linked gene(s) play a role in the pathogenesis of these conditions.     

Interspecific aggression in mixed ungulate species exhibits

Mixed ungulate species exhibits are often plagued with difficulties stemming from interspecific aggression. Several aspects of interspecific aggression were investigated in mixed ungulate species exhibits at the Audubon Zoolnogical Garden in New Orleans, Louisiana. Success of a mixed species exhibit was found to be correlated with the rate of male-initiated aggression, but not with the total rate of aggression. Neither taxonomic relatedness nor size difference between the species could be used to predict the success of a species pairing. The total rate of aggression in an exhibit was related to taxonomic relatedness, aggression being highest between distantly related species. Increases in aggression were triggered by births, mating activity, and introduction of an animal to an exhibit.     

Population relationships of Simulium yahense and Simulium sanctipauli in the Firestone Rubber Plantation at Harbel, Liberia

Comparative genetic differences for the phosphoglucomutase and trehalase loci were surveyed in larval and adult blackfly populations of the onchocerciasis vectors Simulium yahense Vajime and Dunbar, and S.sanctipauli Vajime and Dunbar. Genotype frequencies for each stage and all populations were at Hardy-Weinberg equilibrium, indicating that S.yahense and S.sanctipauli remain genetically distinct. S.yahense populations from three different locations were found to be genotypically comparable. The larval population of S.yahense found in closest proximity to a S.sanctipauli population was found to express the phosphoglucomutase allele 1.33, characteristic of S.sanctipauli, with significantly greater frequency than other larval populations of S.yahense. This may constitute evidence of limited genetic introgression of S.sanctipauli with the S.yahense population.     

Geographical distributions,relative abundance and coexistence of Drosophila aldrichi and Drosophila buzzatii in Australia

Abstract Climatic data and collection records for the cactophilic Drosophila aldrichi and Drosophila buzzatii for 97 localities were used to examine the effects of geographical location, season, host plant species and climatic factors on their range and relative abundance. Temporal variation in relative abundance was assessed from monthly collections over 4 years at one locality. Effects of weather variables over the 28 days before each collection were examined. A generalized linear model of the spatial data showed significant geographical variation in relative abundance, and significant climatic effects, with the proportion of D. aldrichi higher in the warm season, and increasing as temperature variation decreased and moisture indices increased. The temporal data gave generally concordant results, as D. aldrichi proportion was higher in summer and autumn, and increased as maximum and minimum temperatures increased, and as variation in maximum temperature decreased. In a laboratory competition experiment, D. aldrichi eliminated D. buzzatii at 31°C, but was itself eliminated at 18°C and 25°C. The range of D. buzzatii is constrained only by availability of its host plant, Opuntia species, although its relative abundance is reduced in the northern part of its distribution. The range of D. aldrichi, from central Queensland to northern NSW, Australia, is entirely within that of D. buzzatii, and its relative abundance decreases from north to south. Both climate and weather, particularly temperature variability, have direct effects on the relative abundances of the two species, and both likely act indirectly by influencing the outcome of interspecific competition.     

The interspecific competition presents greater nutrient facilitation compared with intraspecific competition through AM fungi interacting with litter for two host plants in karst soil

AM 真菌和枯落物互作下两种喀斯特植物种间竞争较种内竞争更能促进植物养分利用 枯落物是植物养分获取和土壤养分转化的关键载体。丛枝菌根(Arbuscular mycorrhizae, AM)对植物养分摄取的影响已被广泛认知。然而，在养分亏缺的喀斯特生境中，不同竞争方式的植物如何通过AM真菌和枯落物利用养分尚不清楚。本研究对两种喀斯特适生植物构树(Broussonetia papyrifera)和云贵鹅耳枥(Carpinus pubescens)进行种内竞争和种  间竞争种植处理，并通过幼套球 囊霉(Glomus etunicatum)接种或不接种处理，以及土壤中添加或不添加两物种叶片混合枯落物处理，测定了植物生物量以及氮、磷、钾浓度等指标，研究植物的生长和养分利用。研究结果表明，AM真菌对两种植物养分摄取影响不同，AM真菌显著提高了种内和种间竞争下构树的养分摄取量，但降低了云贵鹅耳枥的养分摄取量。种间竞争下接种AM真菌，枯落物添加促进了云贵鹅耳枥对氮的摄取，抑制了构树对氮的摄取。接种AM真菌和添加枯落物条件下，种间竞争的构树对氮、磷和钾的摄取量及云贵鹅耳枥对氮的摄取量均高于种内竞争；种间竞争下两物种养分竞争力呈现明显差异，即构树对磷和钾养分竞争力显著提高，对氮则不显著；云贵鹅耳枥仅对钾的养分竞争力显著降低，对氮和磷则无显著影响。这些结果说明，在AM真菌与枯落物相互作用下，两种喀斯特植物种间竞争较种内竞争更能促进植物养分利用。     

Effects of land preparation and maize cultivar on efficiency of N-fertilizer applied at different times and by different methods in maize—mungbean association using15N

Summary A field experiment was conducted using¹⁵N-labelled urea on a Reddish Brown Lateritic (Peleustult) soil. Growing two crops on flat land and on soil ridges of 15 cm height produced similar comparative effects from fertilizer on maize. However, fertilizer applied by broadcasting on maize with a 50 cm effective band followed by incorporating was more useful to mungbean than that applied by banding below the cereal seed rows when crops were grown on flat land. The reverse was observed when crops were grown on ridges. It was deduced that the maize cultivar was not likely to affect comparative efficiencies of fertilizer. For fertilizer application at sowing, broadcasting in 50 cm maize effective band followed by incorporating was slightly superior to banding below maize seed rows. Side-dressing of fertilizer to maize at 4 weeks after sowing was superior to application at sowing. Evenly-split application, at sowing and at 4 weeks after sowing, was either only slightly superior or comparable to non-split application by banding below maize seed rows at sowing, depending on placement method of the first application. Soil moisture status as a possible factor rendering discrepancy in the comparative efficiencies obtained by different authors is discussed.     

Character displacement in the fighting colours of Hetaerina damselflies

Aggression between species is a seldom-considered but potentially widespread mechanism of character displacement in secondary sexual characters. Based on previous research showing that similarity in wing coloration directly influences interspecific territorial aggression in Hetaerina damselflies, we predicted that wing coloration would show a pattern of character displacement (divergence in sympatry). A geographical survey of four Hetaerina damselfly species in Mexico and Texas showed evidence for character displacement in both species pairs that regularly occurs sympatrically. Hetaerina titia, a species that typically has large black wing spots and small red wing spots, shifted to having even larger black spots and smaller red wing spots at sites where a congener with large red wing spots is numerically dominant (Hetaerina americana or Hetaerina occisa). Hetaerina americana showed the reverse pattern, shifting towards larger red wing spots where H. titia is numerically dominant. This pattern is consistent with the process of agonistic character displacement, but the ontogenetic basis of the shift remains to be demonstrated.