An Intensive Edaphological Characterization of The Soils of Malambito Experimental Station And Its Implications in Future Agricultural Research

Malambito Experiment Station, in the Atlántico III project area, Department of Atlántico, Colombia, had almost no quantitative edaphological data on which to base agricultural research. Unexplainably low general yields as well as problem areas of deficient plant growth only confounded the results of field plot experiments. Intensive soil sampling and subsequent measurements of pH, ECe of the saturation extract, and the four major cations disproved the previous suggestions that the crop growth problems were related to saline, sodic, or degraded soil conditions. The Ca/Mg+K+Na ratio, although significant when correlated with plant height, was sufficient explanation for only a small portion of Malambito problem. The heavy soil texture (50 percent clay) was also shown to be of minor importance in the overall problem. Although no difinitive answer was given to explain the variations in plant growth, a basis for further research was provided, including estimates of soluble plus exchangeable cations and their field variability, pH, organic carbon, ECe and CEC. Future studies in the areas of micronutrient deficiencies and toxicities and possible resistant crops were advocated. Recent research based on the results of this thesis has now implicated heavy metal toxicity as a probably cause for the growth deficiencies and low yields at Malambito

Long term preservation of DNA from honey bees (Apis mellifera) collected in aerial pitfall traps

This study examines the preservation of nuclear and mitochondrial DNA from honey bee (Apis mellifera L.) specimens which were first kept in propylene glycol-based antifreeze under various conditions, and then stored long-term, refrigerated in 95% ethanol. Two sets of bees were subjected to the propylene glycol treatment, then ethanol storage. One set consisted of bees captured in the field in propylene glycol-containing "aerial pitfall traps", where they remained for up to 21 days. A second set consisted of bees taken from a hive and kept in propylene glycol under various temperature and lighting conditions for up to 90 days. Both the field bees and laboratory bees were then stored long-term in ethanol before evaluation of the persistence of nuclear and mitochondrial DNA using the polymerase chain reaction. DNA integrity was preserved for both field and laboratory specimens. The results demonstrate that propylene glycol-captured, ethanol-preserved honey bees retain both nuclear and mitochondrial DNA after capture and long tern preservation. It is suggested that with little or no modification, the techniques described here might he applied to other studies involving trap-collected arthropod specimens

Use of insect repellents for dispersing defending honey bees (Hymenoptera: Apidae)

Some ecotypes of the honey bee, Apis mellifera L., show excessive levels of colony defense that have occasionally resulted in human and animal deaths. In cases where death has occurred, the victim, animal or human, has often been confined or panicked into an area from which it cannot escape. Our study was done to evaluate the use of repellents to reduce the severity of the stinging during accidental disturbances of excessively defensive colonies. Three mosquito repellents (diethyl-meta-toluamide, 2-ethyl-1,3-hexandiol, and dimethyl phthlate) and 2 odiferous compounds known to be repellent to honey bees (benzaldehyde and menthol) were tested in European (Texas) and Africanized (Mexico) apiaries by victims in protective clothing. When sprayed as an aerosol at the defending worker bees, all the compounds significantly reduced the number of bees around the victim and the number of stings in a patch of suede exposed during the test. DEET was consistently the most effective repellent. A number of materials could be developed as repellents for emergency use by individuals that are at high risk of encountering wild honey bee colonies in the course of their daily activity

Spatial and temporal distribution and nest site characteristics of feral honey bee (Hymenoptera: apidae) colonies in a coastal prairie landscape

We evaluated the distribution and abundance of feral honey bee, Apis mellifera L., colonies in a coastal prairie landscape by examining nest site characteristics, population trends, and spatial and temporal patterns in cavity use. The colony densities of up to 12.5 colonies per km2 were the highest reported in the literature for an area including both suitable and unsuitable patches of nesting habitat. The measured cavity attributes were similar to those reported from other areas. The time occupied and turnover indices provided useful information about cavity quality, although none of the measured cavity attributes were correlated with these indices. Unmeasurable cavity characteristics, such as cavity volume, may provide a better estimate of cavity quality. Spatial patterns existed in cavity use by the feral colonies, with the colonies showing an aggregated pattern of distribution throughout the study. Colony aggregations probably resulted from the distribution of resources, especially cavities. Two years after the arrival of Africanized honey bees, cavities used by Africanized and European colonies were aggregated in distribution. During what seemed to be a transition period, both Africanized and European colonies were randomly distributed. After that time, European colonies remained randomly distributed, whereas Africanized colonies were aggregated. Therefore, the invasion of Africanized honey bees seemed to fragment the existing European population, corresponding to a decrease in the overall number of European colonies in the study area

Feral honey bees in pine forest landscapes of east Texas

In 1990 the Africanized honey bee, a descendent of Apis mellifera scutellata, was identified in south Texas [Hunter, L.A., Jackman, J.A., Sugden,E.A., 1992.Detection records of Africanized honey bees inTexas during 1990, 1991 and 1992. Southwestern Entomol. 18, 79–89]. The potential impact of this immigrant on feral and managed colonies was the subject of considerable speculation. The goal of this study was to investigate the diversity of feral honey bee races in pine forest landscapes of east Texas, subsequent to immigration of A. m. scutellata. The specific objectives were (i) to assess the immigration of A. m. scutellata into east Texas pine forest landscapes and (ii) to evaluate the suitability of the pine forest landscape to feral honey bees. This mesoscale landscape study was conducted on the SamHouston National Forest in east Texas. Swarm traps and aerial pitfall traps were used to monitor feral honey bees. Spatial databases were used to evaluate suitability of the pine forest landscape for honey bees. Scoring mitochondrial DNA type (mitotypes), we found representatives of A. mellifera scutellata, eastern European, western European, and A. mellifera lamarckii races in pine forest landscapes of east Texas. The conclusions that follow from this aspect of the investigation are (i) honey bees are a ubiquitous component of the pine forest landscape in east Texas, (ii) mitotype diversity persists subsequent to the immigration of A. m. scutellata, and (iii) A. m. scutellata is an added element of the mitotype diversity in the landscape. To evaluate quantitatively the suitability of the pine forest to feral honey bees, we used a spatial database for the study area and FRAGSTATS. The landscape structure in 1256 ha units surrounding six swarms of honey bees captured in the swarm traps was examined. The metrics used to characterize the kind, number, size, shape, and configuration of elements forming the landscape, defined a heterogeneous environment for honey bees that included sufficient food and habitat resources needed for survival, growth, and reproduction. The conclusions that follow from this aspect of the investigation are (1) although classified as a pine forest, management practices and other human activities have altered the landscape and thereby created food and habitat resources suitable for honey bees, (2) the forestry practices associated specifically with road corridor maintenance, stream side corridor protection, RCW management, and Wilderness Area management introduce structural heterogeneity to the forest landscape which enriches the diversity and abundance of early successional flowering plants and provides cavity sites needed by honey bees, (3) ranching, farming, and urbanization within the study area also create these conditions, and (4) based on inferences from melissopalynology, honey bees provide pollination services for a broad representation of native and introduced flowering plant species of the pineywoods ecoregion

Temporal pattern of africanization in a feral honeybee population from Texas inferred from mitochondrial DNA

The invasion of Africanized honeybees (Apis mellifera L.) in the Americas provides a window of opportunity to study the dynamics of secondary contact of subspecies of bees that evolved in allopatry in ecologically distinctive habitats of the Old World. We report here the results of an 11-year mitochondrial DNA survey of a feral honeybee population from southern United States (Texas). The mitochondrial haplotype (mitotype) frequencies changed radically during the 11-year study period. Prior to immigration of Africanized honeybees, the resident population was essentially of eastern and western European maternal ancestry. Three years after detection of the first Africanized swarm there was a mitotype turnover in the population from predominantly eastern European to predominantly A. m. scutellata (ancestor of Africanized honeybees). This remarkable change in the mitotype composition coincided with arrival of the parasitic mite Varroa destructor, which was likely responsible for severe losses experienced by colonies of European ancestry. From 1997 onward the population stabilized with most colonies of A. m. scutellata maternal origin.PRODEP II - Medida 5/Acção 5.

Identification of africanized honey bee (Hymenoptera: apidae) mitochondrial DNA: validation of a rapid polymerase chain reaction-based assay

Polymerase chain reaction (PCR)-ampliÞed mitochondrialDNA(mtDNA)assays have been used in studies of the Africanization process in neotropical feral and managed honey bee populations. The approach has been adopted, in conjunction with morphometric analysis, to identify Africanized bees for regulatory purposes in the United States such as in California. In this study, 211 Old World colonies, representing all known introduced subspecies in the United States, and 451 colonies from non-Africanized areas of the southern United States were screened to validate a rapid PCR-based assay for identiÞcation of Africanized honey bee mtDNA. This PCR-based assay requires a single enzyme digestion (BglII) of a single PCR-ampliÞed segment of the cytochrome b gene. The BglII polymorphism discriminates the mitochondrial haplotype (mitotype) of Apis mellifera scutellata L. (ancestor of Africanized bees) from that of A. m. mellifera, A. m. caucasia, A. m. ligustica, A. m. carnica, A. m. lamarcki, A. m. cypria, A. m. syriaca, and some A. m. iberiensis, but not from that of A. m. intermissa and some A. m. iberiensis. Nonetheless, given the very low frequency ( 1%) of African non-A. m. scutellata mitotype present before arrival of Africanized bees in the United States, cytochrome b/BglII assay can be used to identify maternally Africanized bees with a high degree of reliability

Utilizing field collected insects for next generation sequencing: effects of sampling, storage and DNA extraction methods

DNA sequencing technologies continue to advance the biological sciences, expanding opportunities for genomic studies of non‐model organisms for basic and applied questions. Despite these opportunities, many next generation sequencing protocols have been developed assuming a substantial quantity of high molecular weight DNA (>100 ng), which can be difficult to obtain for many study systems. In particular, the ability to sequence field‐collected specimens that exhibit varying levels of DNA degradation remains largely unexplored. In this study we investigate the influence of five traditional insect capture and curation methods on Double‐Digest Restriction Enzyme Associated DNA (ddRAD) sequencing success for three wild bee species. We sequenced a total of 105 specimens (between 7–13 specimens per species and treatment). We additionally investigated how different DNA quality metrics (including pre‐sequence concentration and contamination) predicted downstream sequencing success, and also compared two DNA extraction methods. We report successful library preparation for all specimens, with all treatments and extraction methods producing enough highly reliable loci for population genetic analyses. Although results varied between species, we found that specimens collected by net sampling directly into 100% EtOH, or by passive trapping followed by 100% EtOH storage before pinning tended to produce higher quality ddRAD assemblies, likely as a result of rapid specimen desiccation. Surprisingly, we found that specimens preserved in propylene glycol during field sampling exhibited lower‐quality assemblies. We provide recommendations for each treatment, extraction method, and DNA quality assessment, and further encourage researchers to consider utilizing a wider variety of specimens for genomic analysesinfo:eu-repo/semantics/publishedVersio

Africanization of a feral honey bee (Apis mellifera) population in South Texas: Does a decade make a difference?

The arrival to the United States of the Africanized honey bee, a hybrid between European subspecies and the African subspecies Apis mellifera scutellata, is a remarkable model for the study of biological invasions. This immigration has created an opportunity to study the dynamics of secondary contact of honey bee subspecies from African and European lineages in a feral population in South Texas. An 11-year survey of this population (1991-2001) showed that mitochondrial haplotype frequencies changed drastically over time from a resident population of eastern and western European maternal ancestry, to a population dominated by the African haplotype. A subsequent study of the nuclear genome showed that the Africanization process included bidirectional gene flow between European and Africanized honey bees, giving rise to a new panmictic mixture of A.m.scutellata- and European-derived genes. In this study, we examined gene flow patterns in the same population 23 years after the first hybridization event occurred. We found 28 active colonies inhabiting 92 tree cavities surveyed in a 5.14 km2 area, resulting in a colony density of 5.4 colonies/km2. Of these 28 colonies, 25 were of A.m. scutellata maternal ancestry, and three were of western European maternal ancestry. No colonies of eastern European maternal ancestry were detected, although they were present in the earlier samples. Nuclear DNA revealed little change in the introgression of A.m.scutellata-derived genes into the population compared to previous surveys. Our results suggest this feral population remains an admixed swarm with continued low levels of European ancestry and a greater presence of African-derived mitochondrial genetic composition.Peer reviewedZoolog

Processing-Structure-Property Relationships of Spark Plasma Sintered Boron Carbide and Titanium Diboride Ceramic Composites

The aim of this study was to understand the processing – structure – property relationships in spark plasma sintered (SPS) boron carbide (B4C) and B4C-titanium diboride (TiB2) ceramic composites. SPS allowed for consolidation of both B4C and B4C-TiB2 composites without sintering additives, residual phases, e.g., graphite, and excessive grain growth due to long sintering times. A selection of composite compositions in 20% TiB2 feedstock powder increments from 0% to 100%, was sintered at 1900°C for 25 minutes hold time. A homogeneous B4C-TiB2 composite microstructure was determined with excellent distribution of TiB2 phase, while achieving ~99.5% theoretical density. An optimum B4C-23 vol.% TiB2 composite composition with low density of ~3.0 g/cm3 was determined that exhibited ~30-35% increase in hardness, fracture toughness, and flexural bend strength compared to commercial armor-grade B4C. This is a result of a) no residual graphitic carbon in the composites, b) interfacial microcrack toughening due to thermal expansion coefficient differences placing the B4C matrix in compression and TiB2 phase in tension, and c) TiB2 phase aids in crack deflection thereby increasing the amount of intergranular fracture. Collectively, the addition of TiB2 serves as a strengthening and toughening agent, and SPS shows promise for the manufacture of hybrid ceramic composites