Differences In Evolutionary History Research Articles

In-planta sporulation phenotype: a major life history trait to understand the evolution of Alnus-infective Frankia strains.

Two major types of Frankia strains are usually recognized, based on the ability to sporulate in-planta: spore-positive (Sp+) and spore-negative (Sp-). We carried out a study of Sp+ and Sp- Frankia strains based on nodules collected on Alnus glutinosa, Alnus incana and Alnus viridis. The nodules were phenotyped using improved histology methods, and endophytic Frankia strain genotype was determined using a multilocus sequence analysis approach. An additional sampling was done to assess the relation between Sp+ phenotype frequency and genetic diversity of Frankia strains at the alder stand scale. Our results revealed that (i) Sp+ and Sp- Alnus-infective Frankia strains are genetically different even when sampled from the same alder stand and the same host-plant species; (ii) there are at least two distinct phylogenetic lineages of Sp+ Frankia that cluster according to the host-plant species and without regard of geographic distance and (iii) genetic diversity of Sp+ strains is very low at the alder stand scale compared with Sp- strains. Difference in evolutionary history and genetic diversity between Sp+ and Sp- Frankia allows us to discuss the possible ecological role of in-planta sporulation.

Intercontinental divergence in the climate envelope of major plant biomes

AbstractAimConvergent evolution and environmental filtering are assumed to often result in deterministic patterns of vegetation structure and function in relation to prevailing environmental conditions regardless of differences in evolutionary history among regions. We systematically evaluate the degree to which biomes located in different biogeographic realms converge in environmental space; identifying globally uniform entities and those diverging systematically among realms.LocationGlobal.MethodsTwo global biome distribution maps constructed using contrasting approaches are used to evaluate convergence in the environmental space occupied by biomes across biogeographic realms. Environmental conditions are summarized using nine climatic and two edaphic variables known to directly influence plant distributions. Biome maps are analysed accounting for differences in the availability of environments among realms.ResultsThe same biome located in two different realms often overlaps no more in environmental space than two altogether different biomes, with the average overlap on the two biome maps calculated using Schoener's D metric only 0.42 and 0.36. This suggests that the coarse structural and phenological characteristics used to define biomes conceal important differences in plant functioning and responses to environmental drivers. Nonetheless, some biomes, in particular savannas and boreal forests, show high overlap among realms. Others, like mediterranean‐type ecosystems and treeless biomes, often occur in vastly different regions of environmental space. Within most biomes though overlap varies greatly depending on the specific realms being compared, with historical biogeography and evolutionary history helping to explain this variation.Main conclusionsBiomes often occur under different environmental conditions when comparing regions with distinct evolutionary and environmental histories. The biome concept and efforts to model current and future vegetation patterns needs to be adapted to account for the role of history in determining how vegetation responds to environmental drivers and disturbance.

Influence of HIV and HCV on T cell antigen presentation and challenges in the development of vaccines.

Some of the central challenges for developing effective vaccines against HIV and hepatitis C virus (HCV) are similar. Both infections are caused by small, highly mutable, rapidly replicating RNA viruses with the ability to establish long-term chronic pathogenic infection in human hosts. HIV has caused 60 million infections globally and HCV 180 million and both viruses may co-exist among certain populations by virtue of common blood-borne, sexual, or vertical transmission. Persistence of both pathogens is achieved by evasion of intrinsic, innate, and adaptive immune defenses but with some distinct mechanisms reflecting their differences in evolutionary history, replication characteristics, cell tropism, and visibility to mucosal versus systemic and hepatic immune responses. A potent and durable antibody and T cell response is a likely requirement of future HIV and HCV vaccines. Perhaps the single biggest difference between the two vaccine design challenges is that in HCV, a natural model of protective immunity can be found in those who resolve acute infection spontaneously. Such spontaneous resolvers exhibit durable and functional CD4+ and CD8+ T cell responses (Diepolder et al., 1995; Cooper et al., 1999; Thimme et al., 2001; Grakoui et al., 2003; Lauer et al., 2004; Schulze Zur Wiesch et al., 2012). However, frequent re-infection suggests partial or lack of protective immunity against heterologous HCV strains, possibly indicative of the degree of genetic diversity of circulating HCV genotypes and subtypes. There is no natural model of protective immunity in HIV, however, studies of “elite controllers,” or individuals who have durably suppressed levels of plasma HIV RNA without antiretroviral therapy, has provided the strongest evidence for CD8+ T cell responses in controlling viremia and limiting reservoir burden in established infection. Here we compare and contrast the specific mechanisms of immune evasion used by HIV and HCV, which subvert adaptive human leukocyte antigen (HLA)-restricted T cell immunity in natural infection, and the challenges these pose for designing effective preventative or therapeutic vaccines.

Differences in mandibular disparity between extant and extinct species of metatherian and placental carnivore clades

There are a number of studies relating to skull morphology differences within the carnivoran clades of both placentals and metatherians. It is difficult to compare these studies because of differences in taxonomic sampling, for example some include fossil taxa while others include non-carnivoran placentals. As a consequence, we studied mandible morphology in a broad range of both extant and extinct carnivorous species, including Carnivora, Marsupialia and Sparassodonta to test for differences between these clades. We used geometric morphometrics and two disparity indexes, the variance and Procrustes distances mean. When including fossil species, we found no significant differences for both disparities in some analyses, except after the exclusion of the sabretooth morphotype. This can be explained by the extreme morphology of this morphotype, which increases the variance and reduces the disparity effect of the other species in the analyses. Using Procrustes distances, we found significant differences in disparity distances between Carnivora and Metatheria for most of the analyses. We also found significant differences using the variance index in some analyses. The mandibular disparity in Carnivora is greater than in carnivorous metatherian mammals for most of the cases and this can be related with differences in evolutionary history and constraints of both groups. The pattern found in the mandible is similar to that found in the face of the skull but was not observed in the braincase, due to differences in skull function and mandible function.

Differences in evolutionary history translate into differences in invasion success of alien mammals in South Africa.

Attempts to investigate the drivers of invasion success are generally limited to the biological and evolutionary traits distinguishing native from introduced species. Although alien species introduced to the same recipient environment differ in their invasion intensity – for example, some are “strong invaders”; others are “weak invaders” – the factors underlying the variation in invasion success within alien communities are little explored. In this study, we ask what drives the variation in invasion success of alien mammals in South Africa. First, we tested for taxonomic and phylogenetic signal in invasion intensity. Second, we reconstructed predictive models of the variation in invasion intensity among alien mammals using the generalized linear mixed-effects models. We found that the family Bovidae and the order Artiodactyla contained more “strong invaders” than expected by chance, and that such taxonomic signal did not translate into phylogenetic selectivity. In addition, our study indicates that latitude, gestation length, social group size, and human population density are only marginal determinant of the variation in invasion success. However, we found that evolutionary distinctiveness – a parameter characterising the uniqueness of each alien species – is the most important predictive variable. Our results indicate that the invasive behavior of alien mammals may have been “fingerprinted” in their evolutionary past, and that evolutionary history might capture beyond ecological, biological and life-history traits usually prioritized in predictive modeling of invasion success. These findings have applicability to the management of alien mammals in South Africa.

New approaches for unravelling reassortment pathways.

BackgroundEvery year the human population encounters epidemic outbreaks of influenza, and history reveals recurring pandemics that have had devastating consequences. The current work focuses on the development of a robust algorithm for detecting influenza strains that have a composite genomic architecture. These influenza subtypes can be generated through a reassortment process, whereby a virus can inherit gene segments from two different types of influenza particles during replication. Reassortant strains are often not immediately recognised by the adaptive immune system of the hosts and hence may be the source of pandemic outbreaks. Owing to their importance in public health and their infectious ability, it is essential to identify reassortant influenza strains in order to understand the evolution of this virus and describe reassortment pathways that may be biased towards particular viral segments. Phylogenetic methods have been used traditionally to identify reassortant viruses. In many studies up to now, the assumption has been that if two phylogenetic trees differ, it is because reassortment has caused them to be different. While phylogenetic incongruence may be caused by real differences in evolutionary history, it can also be the result of phylogenetic error. Therefore, we wish to develop a method for distinguishing between topological inconsistency that is due to confounding effects and topological inconsistency that is due to reassortment.ResultsThe current work describes the implementation of two approaches for robustly identifying reassortment events. The algorithms rest on the idea of significance of difference between phylogenetic trees or phylogenetic tree sets, and subtree pruning and regrafting operations, which mimic the effect of reassortment on tree topologies. The first method is based on a maximum likelihood (ML) framework (MLreassort) and the second implements a Bayesian approach (Breassort) for reassortment detection. We focus on reassortment events that are found by both methods. We test both methods on a simulated dataset and on a small collection of real viral data isolated in Hong Kong in 1999.ConclusionsThe nature of segmented viral genomes present many challenges with respect to disease. The algorithms developed here can effectively identify reassortment events in small viral datasets and can be applied not only to influenza but also to other segmented viruses. Owing to computational demands of comparing tree topologies, further development in this area is necessary to allow their application to larger datasets.

Quantifying Phylogenetic Beta Diversity: Distinguishing between ‘True’ Turnover of Lineages and Phylogenetic Diversity Gradients

The evolutionary dissimilarity between communities (phylogenetic beta diversity PBD) has been increasingly explored by ecologists and biogeographers to assess the relative roles of ecological and evolutionary processes in structuring natural communities. Among PBD measures, the PhyloSor and UniFrac indices have been widely used to assess the level of turnover of lineages over geographical and environmental gradients. However, these indices can be considered as ‘broad-sense’ measures of phylogenetic turnover as they incorporate different aspects of differences in evolutionary history between communities that may be attributable to phylogenetic diversity gradients. In the present study, we extend an additive partitioning framework proposed for compositional beta diversity to PBD. Specifically, we decomposed the PhyloSor and UniFrac indices into two separate components accounting for ‘true’ phylogenetic turnover and phylogenetic diversity gradients, respectively. We illustrated the relevance of this framework using simple theoretical and archetypal examples, as well as an empirical study based on coral reef fish communities. Overall, our results suggest that using PhyloSor and UniFrac may greatly over-estimate the level of spatial turnover of lineages if the two compared communities show contrasting levels of phylogenetic diversity. We therefore recommend that future studies use the ‘true’ phylogenetic turnover component of these indices when the studied communities encompass a large phylogenetic diversity gradient.

Exploratory behaviour in shrews: fast-lived Sorex versus slow-lived Crocidura

Exploration of the environment is a key behaviour in animals. The exploratory behaviour of species or populations depends on different aspects of their ecology. New evidence suggests that differences in exploratory behaviour might also be related to life history strategies, with fast-lived animals (high metabolic rate, short life span) being faster explorers than slow-lived ones. We tested this assumption in shrews. Shrews are divided into two phylogenetic groups, which differ tremendously in life history. We compared the exploratory behaviour of three species, covering both phylogenetic groups. Shrews of the fast-lived genus Sorex were quicker to start exploration and to locate the first food patch. They also moved faster than the slow-lived genus Crocidura . Unlike many studies on exploratory behaviour that analyse only a short period of time (i.e. a single exploration bout with a fixed duration), we analysed the species-specific allocation of prolonged total exploration time into exploration bouts. Using this method, we could show that Sorex performed more, but shorter exploration bouts than Crocidura . Our results support the hypothesis of exploratory behaviour being related to life history. While the species we tested occur sympatrically, the two genera differ strongly in the climatic zones they inhabit. It is likely that also during evolution they faced different types of habitat and thus different selection pressures. These differences in evolutionary histories possibly favoured the evolution of their diversified life histories and exploration strategies. ► We analysed the temporal and spatial strategies of shrews to explore a large open arena. ► We used shrew species with strong differences in life history. ► Shrews with a fast live history showed a fast and time-efficient exploration strategy. ► Shrews with a slow live history showed a slow and thorough exploration strategy. ► Our results support the hypothesis that exploratory behaviour relates to life history.

Ecological commonalities among pelagic fishes: comparison of freshwater ciscoes and marine herring and sprat

Systematic comparisons of the ecology between functionally similar fish species from freshwater and marine aquatic systems are surprisingly rare. Here, we discuss commonalities and differences in evolutionary history, population genetics, reproduction and life history, ecological interactions, behavioural ecology and physiological ecology of temperate and Arctic freshwater coregonids (vendace and ciscoes, Coregonus spp.) and marine clupeids (herring, Clupea harengus, and sprat, Sprattus sprattus). We further elucidate potential effects of climate warming on these groups of fish based on the ecological features of coregonids and clupeids documented in the previous parts of the review. These freshwater and marine fishes share a surprisingly high number of similarities. Both groups are relatively short-lived, pelagic planktivorous fishes. The genetic differentiation of local populations is weak and seems to be in part correlated to an astonishing variability of spawning times. The discrete thermal window of each species influences habitat use, diel vertical migrations and supposedly also life history variations. Complex life cycles and preference for cool or cold water make all species vulnerable to the effects of global warming. It is suggested that future research on the functional interdependence between spawning time, life history characteristics, thermal windows and genetic differentiation may profit from a systematic comparison of the patterns found in either coregonids or clupeids.

The Logic of Evolution: Review of the Logic of Chance by Eugene V. Koonin

The Logic of Evolution: Review of the Logic of Chance by Eugene V. Koonin

Exposure to predation across different time scales alters cortisol levels in guppies

Event Abstract Back to Event Exposure to predation across different time scales alters cortisol levels in guppies Eva Kristin Fischer1*, Rayna M. Harris2, Hans A. Hofmann2 and Kim L. Hoke1 1 Colorado State University, Biology Department, United States 2 University of Texas at Austin, Section of Integrative Biology, United States Hormonal responses are inherently plastic, responding to both an organism’s internal and external environment on a time scale from minutes to months. In addition, genetic factors influence hormone levels, making them targets of long-term selective processes. The interactions between genetic and environmental factors in shaping hormonal responses have important implications for individual fitness and adaptive evolution, however, they can rarely be parsed out in natural populations. Due to their well-established role in mediating stress responses, glucocorticoid steroid hormones are often implicated in mediating adaptive shifts in response to environmental stressors, in particular predation pressure. Because differences in predation pressure have repeatedly and independently driven adaptive divergence in the Trinidadian guppy (Poecilia reticulata), we hypothesized that differences in cortisol levels in guppies would reflect differences in evolutionary history with predators and/or life-time exposure to predators. We reared fish from high and low predation source populations with and without exposure to chemical cues of predators and examined baseline cortisol levels and acute cortisol responses using water-borne hormone assays. We first demonstrated that guppies rapidly habituate to sample collection procedures and validated water-borne cortisol results using whole body/water cortisol correlations. We found that both evolutionary history with predators and lifetime exposure to chemical cues of predators decreased baseline cortisol levels. This may be an adaptive shift to reduce the detrimental effects of chronically elevated cortisol that could result from persistent exposure to predators. Similarly, acute exposure to chemical cues of predators reduced excreted cortisol. We are currently exploring whether decreased cortisol excretion reflects decreased internal cortisol levels, or whether guppies actively decrease cortisol excretion in response to predator cues. The fact that evolutionary history with predators and lifetime exposure to predators both decrease cortisol release raises the possibility that adaptive evolutionary changes may co-opt pre-existing responses to environmental changes. This work demonstrates genetic and environmental influences on a hormonal system in a rapidly adapting natural population. Ultimately, we hope to link these hormonal differences to morphological and behavioral differences. Keywords: adaptive evolution, cortisol, Poecilia reticulata, predation Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for participant symposium and student poster award) Topic: Hormones and Sex Differences Citation: Fischer E, Harris RM, Hofmann HA and Hoke KL (2012). Exposure to predation across different time scales alters cortisol levels in guppies. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00385 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 01 May 2012; Published Online: 07 Jul 2012. * Correspondence: Ms. Eva Kristin Fischer, Colorado State University, Biology Department, Fort Collins, CO, 80521, United States, evakfisch@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Eva Kristin Fischer Rayna M Harris Hans A Hofmann Kim L Hoke Google Eva Kristin Fischer Rayna M Harris Hans A Hofmann Kim L Hoke Google Scholar Eva Kristin Fischer Rayna M Harris Hans A Hofmann Kim L Hoke PubMed Eva Kristin Fischer Rayna M Harris Hans A Hofmann Kim L Hoke Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Genomic characterization of novel dolphin papillomaviruses provides indications for recombination within the Papillomaviridae

Phylogenetic analysis of novel dolphin ( Tursiops truncatus) papillomavirus sequences, TtPV1, -2, and -3, indicates that the early and late protein coding regions of their genomes differ in evolutionary history. Sliding window bootscan analysis showed a significant a change in phylogenetic clustering, in which the grouped sequences of TtPV1 and -3 move from a cluster with the Phocoena spinipinnis PsPV1 in the early region to a cluster with TtPV2 in the late region. This provides indications for a possible recombination event near the end of E2/beginning of L2. A second possible recombination site could be located near the end of L1, in the upstream regulatory region. Selection analysis by using maximum likelihood models of codon substitutions ruled out the possibility of intense selective pressure, acting asymmetrically on the viral genomes, as an alternative explanation for the observed difference in evolutionary history between the early and late genomic regions of these cetacean papillomaviruses.

Convergence and contingency in production–precipitation relationships in North American and South African C4 grasslands

Mesic grasslands in North America and South Africa share many structural attributes, but less is known of their functional similarities. We assessed the control of a key ecosystem process, aboveground net primary production (ANPP), by interannual variation in precipitation amount and pattern via analysis of data sets (15- and 24-year periods) from long-term research programs on each continent. Both sites were dominated by C(4) grasses and had similar growing season climates; thus, we expected convergence in precipitation-ANPP relationships. Lack of convergence, however, would support an alternative hypothesis-that differences in evolutionary history and purportedly greater climatic variability in South Africa fundamentally alter the functioning of southern versus northern hemisphere grasslands. Neither mean annual precipitation nor mean ANPP differed between the South African and North American sites (838 vs. 857 mm/year, 423.5 vs. 461.4 g/m(2) respectively) and growing season precipitation-ANPP relationships were similar. Despite overall convergence, there were differences between sites in how the seasonal timing of precipitation affected ANPP. In particular, interannual variability in precipitation that fell during the first half of the growing season strongly affected annual ANPP in South Africa (P < 0.01), but was not related to ANPP in North America (P = 0.098). Both sites were affected similarly by late season precipitation. Divergence in the seasonal course of available soil moisture (chronically low in the winter and early spring in the South African site vs. high in the North American site) is proposed as a key contingent factor explaining differential sensitivity in ANPP to early season precipitation in these two grasslands. These long-term data sets provided no support for greater rainfall, temperature or ANPP variability in the South African versus the North American site. However, greater sensitivity of ANPP to early season precipitation in the South African grassland suggests that future patterns of productivity may be more responsive to seasonal changes in climate compared with the North American site.

Can common species provide valuable information for conservation?

To demonstrate the importance of genetic data for multispecies conservation approaches, we examined the distribution of genetic variation across the range of the mountain whitefish (Prosopium williamsoni) at microsatellite and allozyme loci. The mountain whitefish is a common species that is particularly well suited for accurately revealing historical patterns of genetic structure and differs markedly from previously studied species in habitat requirements and life history characteristics. As such, comparing the population genetic structure of other native fishes to similar data from mountain whitefish could inform management and conservation strategies. Genetic variation for mountain whitefish was hierarchically distributed for both allozymes and microsatellites. We found evidence for a total of five major genetically differentiated assemblages and we observed subdivision among populations within assemblages that generally corresponded to major river basins. We observed little genetic differentiation within major river basins. Geographic patterns of genetic differentiation for mountain whitefish were concordant with other native species in several circumstances, providing information for the designation of conservation units that reflect concordant genetic differentiation of multiple species. Differences in genetic patterns between mountain whitefish and other native fishes reflect either differences in evolutionary histories of the species considered or differences in aspects of their ecology and life history. In addition, mountain whitefish populations appear to exchange genes over a much larger geographic scale than co-occurring salmonids and are likely to be affected differently by disturbances such as habitat fragmentation.

MILD: a tool for constructing and analyzing matrices of pairwise phylogenetic character incongruence tests

Pairwise comparisons of disagreement in phylogenetic datasets offer a powerful tool for isolating historical incongruence for closer analysis. Statistically significant phylogenetic character incongruence may reflect important differences in evolutionary history, such as horizontal gene transfer. Such testing can also be used to specify possible combinations of datasets for further phylogenetic analysis. The process of comparing multiple datasets can be very time consuming, and it is sometimes unclear how to combine data partitions given the observed patterns of incongruence. Here we present an application that automates the process of making pairwise comparisons between large numbers of phylogenetic datasets using the Incongruence Length Difference (ILD) test. The application also implements strategies for data combination based on the patterns of incongruence observed in pairwise comparisons.

Genotypic variation among lineages of Trypanosoma cruzi and its geographic aspects

Isozyme analysis with 18 enzyme loci was conducted on 146 isolates of Trypanosoma cruzi from Mexico, Guatemala, Colombia, Ecuador, Peru, Brazil, Bolivia, Paraguay and Chile. Forty-four different MLGs (groups of isolates with identical multilocus genotypes) were identified and a phylogeny was constructed. The phylogenetic tree consisted of two main groups ( T. cruzi I, T. cruzi II), and the latter was further divided into two subgroups ( T. cruzi IIa, T. cruzi IIb–e). Evidence of hybridization between different MLGs of T. cruzi II was found, which means that genetic exchanges seem to have occurred in South American T. cruzi. On the other hand, the persistence of characteristic T. cruzi I and T. cruzi II isozyme patterns in single small villages in Bolivia and Guatemala suggested that genetic exchange is very rare between major lineages. A significant difference in genetic diversity was shown between T. cruzi I and T. cruzi II from several indices of population genetics. Two possibilities could explain this genetic variation in the population: differences in evolutionary history and/or different tendencies to exchange genetic material. Broad-scale geographic distributions of T. cruzi I and T. cruzi IIb–e were different; T. cruzi I occurred in Central America and south to Bolivia and Brazil, while T. cruzi IIb–e occurred in the central and southern areas of South America, overlapping with T. cruzi I in Brazil and Bolivia.

RED-T: utilizing the Ratios of Evolutionary Distances for determination of alternative phylogenetic events.

RED-T is a Java application for phylogenetic analysis based on a unique method, RED, that utilizes the ratios of evolutionary distances E(d) to distinguish between alternative evolutionary histories. RED-T allows the user to examine if any given experimental gene shares the same evolutionary history as the designated control gene(s). Moreover, the tool detects any differences in evolutionary history and allows the user to examine comparisons of E(d) for a likely explanation. Lateral gene transfer, which may have a significant influence in organismal evolution is one mechanism that could explain the findings of these RED-T analyses. The application is available online at http://www.arches.uga.edu/~whitman/RED.

Acoustic Communication in Insects and Anurans: Common Problems and Diverse Solutions

Walk near woods or water on any spring or summer night and you will hear a bewildering (and sometimes deafening) chorus of frog, toad, and insect calls. How are these calls produced? What messages are encoded within the sounds, and how do their intended recipients receive and decode these signals? How does acoustic communication affect and reflect behavioral and evolutionary factors such as sexual selection and predator avoidance? H. Carl Gerhardt and Franz Huber address these questions among many others, drawing on research from bioacoustics, behavior, neurobiology, and evolutionary biology to present the first integrated approach to the study of acoustic communication in insects and anurans. They highlight both the common solutions that these very different groups have evolved to shared challenges, such as small size, ectothermy (cold-bloodedness), and noisy environments, as well as the divergences that reflect the many differences in evolutionary history between the groups. Throughout the book Gerhardt and Huber also provide helpful suggestions for future research.

Geographic differences in host acceptance and suitability of two Cotesia sesamiae populations in Zimbabwe

Abstract Three lepidopteran stemborers, Busseola fusca Fuller (Noctuidae), Sesamia calamistis Hampson (Noctuidae), and Chilo partellus (Swinhoe) (Crambidae), were evaluated for their acceptability for oviposition and suitability for development by two populations of the larval endoparasitoid Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) occurring in the highveld (>1200 m) and lowveld ( C. sesamiae populations preferred the noctuids to C. partellus for oviposition, possibly reflecting differences in evolutionary history. Although B. fusca was partially suitable for development of lowveld C. sesamiae , all three hosts were suitable for development of the highveld population. Crosses between highveld and lowveld C. sesamiae were compatible, and were generally not different from the intra-population crosses in developmental time, % adult emergence and sex ratio. However, broods were much larger when highveld males were used in the mating combinations. We conclude that although there is host overlap and probably a considerable degree of outbreeding between the two C. sesamiae populations, there are still significant genetic differences between them. Within Zimbabwe, it is unlikely that the deliberate introduction of either population outside its region of occurrence will give meaningful stemborer control.

Population structure analysis of Burkholderia cepacia genomovar III: varying degrees of genetic recombination characterize major clonal complexes.

Infection with bacterial species belonging to the Burkholderia cepacia complex contribute significantly to morbidity and mortality in persons with cystic fibrosis (CF). The majority of isolates recovered from CF patients belong to B. cepacia genomovar III and several distinct 'epidemic' strains have been described. This study examined the population structure of B. cepacia genomovar III by using multilocus restriction typing, indexing allelic variation at five chromosomal genes by restriction analysis of PCR-amplified genes. A collection of 375 isolates, recovered from CF and non-CF patients and natural environments in North America, Europe and Australia, was examined. Among these isolates 144 different restriction types were found. Overall, the population is at linkage disequilibrium, indicating that it has a clonal structure. The majority (86.7 %) of restriction types grouped into three major clonal complexes, comprising the epidemic ET12, PHDC and Midwest clonal lineages. The analysis indicates that these complexes are geographically widespread and demonstrate varying degrees of genetic recombination. These differences in population structure among major clonal complexes within the same species are likely related to differences in evolutionary history and ecology. The observation that genetic recombination is frequent within some B. cepacia genomovar III populations has important implications for the biotechnological use of B. cepacia complex species.