The spatial pattern of soil-dwelling termites in primary and logged forest in Sabah, Malaysia

Abstract.  1. Primary and logged lowland dipterocarp forest sites were sampled for subterranean termites using soil pits located on a grid system in order to detect any patchiness in their distribution.
2. A spatial pattern in termite distributions was observed in the primary and logged sites, but the response differed between soil-feeding and non-soil-feeding termites.
3. Spatial analysis showed that soil-feeding termites were homogeneously distributed in the primary forest but significantly aggregated in the logged forest. This pattern was reversed for non-soil-feeding termites and may result from differences in resource provisioning between the two sites.
4. Gaps in termite distribution comprised a greater area than patches for both feeding groups and sites, but gaps dominated the logged site.
5. A significant association between soil-feeding and non-soil-feeding termite distributions occurred at both sites. This arose from an association between patches in the primary forest and between gaps in the logged forest.
6. Termite spatial pattern was optimally observed at a minimum extent of 64 m and lag of 2 m.
7. The spatially explicit SADIE (Spatial Analysis by Distances IndicEs) analyses were more successful than (non-spatially explicit) multivariate analysis (Canonical Correspondence Analysis) at detecting associations between termite spatial distributions and that of other biotic and abiotic variables.     

Fluctuations in Escherichia coli O-serotypes in Pigs Throughout Life in the Presence and Absence of Antibiotic Treatment

A detailed study, throughout life, of the coliform and Escherichia coli gut flora of two pigs, is presented. One pig was given oral tetracycline for 3 d on two separate occasions; the other pig was not treated and housed separately. The fluctuations in numbers of coliforms, O-serotypes of E. coli , the occurrence and persistence of antibiotic resistance, and their interrelations, are analysed for both animals. Oral tetracycline profoundly affected the proportion of antibiotic sensitive and resistant E. coli , and, by selecting for R-factor bearing O-serotypes, limited the number of O-serotypes isolated from individual faceal specimens. Specific O-serotypes exhibited marked differences in their ability to persist in the gut of the control pig. The R-factor bearing O-serotypes, selected by tetracycline treatment, also showed differences in ability to persist after treatment indicating that properties other than the possession of R-factors, decide colonizing ability. The size of the colony sample for serotype analysis is discussed.     

Attempts to Displace the Indigenous Antibiotic Resistant Gut Flora of Chicken by Feeding Sensitive Strains of Escherichia coli Prior to Slaughter

Attempts to limit the use of antibiotics have not, in general, resulted in the gut flora in farm animals becoming predominantly sensitive. Partial success has been demonstrated, however, by feeding chickens with antibiotic sensitive Escherichia coli known to be good colonizers of the chicken gut. Where feeding was done prior to slaughter a corresponding reduction in carcass contamination by resistant E. coli was observed.     

The Effect of Tetracycline on the Coliform Gut Flora of Broiler Chickens with Special Reference to Antibiotic Resistance and O-Serotypes of Escherichia coli

The effect of terramycin, administered prophylactically in drinking water, on the gut flora of broiler birds was investigated. Exposure to the antibiotic for only 24 h profoundly affected the counts of tetracycline-resistant strains and selected O-serotypes carrying resistance determinants. Large numbers of Escherichia coli resistant to sulphonamides were found in treated and control birds and this is discussed in relation to the use of sulphaquinoxaline as a coccidiostat. Evidence of carcass contamination by antibiotic resistant E. coli found in the gut is presented.     

The speciation and biotyping of enteroccccal isolates from chickens

A scheme for speciating and biotyping enterococcal isolates from chickens is described. All tests are performed using solid media inoculated with a multipoint inoculator and can be done in conjunction with an antibiotic sensitivity test in which the agents are also incorporated into agar.     

Inter‐specific gene flow dynamics during the Pleistocene‐dated speciation of forest‐dependent mosquitoes in Southeast Asia

Tropical forests have undergone repeated fragmentation and expansion during Pleistocene glacial and interglacial periods, respectively. The effects of this repeated forest fragmentation in driving vicariance in tropical taxa have been well studied. However, relatively little is known about how often this process results in allopatric speciation, since it may be inhibited by recurrent gene flow during repeated secondary contact, or to what extent Pleistocene‐dated speciation results from ecological specialization in the face of gene flow. Here, divergence times and gene flow between three closely‐related mosquito species of the Anopheles dirus species complex endemic to the forests of Southeast Asia, are inferred using coalescent based Bayesian analysis. An Isolation with Migration model is applied to sequences of two mitochondrial and three nuclear genes, and 11 microsatellites. The divergence of An. scanloni has occurred despite unidirectional nuclear gene flow from this species into An. dirus. The inferred asymmetric gene flow may result from the unique evolutionary adaptation of An. scanloni to limestone karst habitat, and therefore the fitness advantage of this species over An. dirus in regions of sympatry. Mitochondrial introgression has led to the complete replacement of An. dirus haplotypes with those of An. baimaii through a recent (～62 kya) selective sweep. Speciation of An. baimaii and An. dirus is inferred to have involved allopatric divergence throughout much of the Pleistocene. Secondary contact and bidirectional gene flow has occurred only within the last 100 000 years, by which time the process of allopatric speciation seems to have been largely completed.