Multiple endosymbionts in populations of the ant Formica cinerea

<p>Abstract</p> <p>Background</p> <p>Many insects, including ants, are infected by maternally inherited <it>Wolbachia </it>endosymbiotic bacteria though other secondary endosymbionts have not been reported in ants. It has been suggested that the ability of <it>Wolbachia </it>to invade and remain in an ant population depends on the number of coexisting queens in a colony. We study the genetic and social structure of populations in the ant <it>Formica cinerea </it>which is known to have populations with either monogynous or polygynous colonies. We screen populations for several endosymbiotic bacteria to evaluate the presence of different endosymbionts, possible association between their prevalence and the social structure, and the association between endosymbiont prevalence and genetic differentiation of ant populations.</p> <p>Results</p> <p>We found three endosymbiotic bacteria; 19% of the nests were infected by <it>Wolbachia</it>, 3.8% by <it>Cardinium </it>and 33% by <it>Serratia</it>. There was significant variation among the populations regarding the proportion of nests infected by <it>Serratia</it>, <it>Wolbachia </it>and the pooled set of all the endosymbionts. Some individuals and colonies carried two of the bacteria, the frequency of double infections agreeing with the random expectation. The proportion of infected ants (individuals or colonies) did not correlate significantly with the population level relatedness values. The difference in the prevalence of <it>Wolbachia </it>between population pairs correlated significantly with the genetic distance (microsatellites) of the populations.</p> <p>Conclusions</p> <p>The discovery of several endosymbionts and co-infections by <it>Wolbachia </it>and <it>Cardinium </it>demonstrate the importance of screening several endosymbionts when evaluating their possible effects on social life and queen-worker conflicts over sex allocation. The low prevalence of <it>Wolbachia </it>in <it>F. cinerea </it>departs from the pattern observed in many other <it>Formica </it>ants in which all workers have been infected. It is likely that the strain of <it>Wolbachia </it>in <it>F. cinerea </it>differs from those in other <it>Formica </it>species. The correlation between the difference in <it>Wolbachia </it>prevalence and the pair-wise genetic distance of populations suggests that spreading of the bacteria is restricted by the isolation of the host populations.</p

Wolbachia transmission dynamics in Formica wood ants

Background: The role of Wolbachia endosymbionts in shaping the mitochondrial diversity of their arthropod host depends on the effects they have on host reproduction and on the mode of transmission of the bacteria. We have compared the sequence diversity of wsp ( Wolbachia surface protein gene) and the host mtDNA in a group of Formica ant species that have diverged approximately 0.5 million years ago ( MYA). The aim was to study the relationship of Wolbachia and its ant hosts in terms of vertical and horizontal transmission of the bacteria.Results: All studied ant species were doubly infected with two Wolbachia strains ( wFexl and wFex4) all over their geographical distribution area in Eurasia. The most common haplotypes of these strains were identical with strains previously described from a more distantly related Formica ant, with an estimated divergence time of 3.5 - 4 MYA. Some strain haplotypes were associated to the same or closely related mtDNA haplotypes as expected under vertical transmission. However, in several cases the wsp haplotypes coexisted with distant mtDNA haplotypes, a pattern which is more compatible with horizontal transmission of the bacteria.Conclusion: Two lines of evidence suggest that the sharing of Wolbachia strains by all F. rufa species is rather due to horizontal than vertical transmission. First, the fact that endosymbiont strains identical to those of F. rufa ants have been found in another species that diverged 3.5 - 4 MYA strongly suggests that horizontal transfer can and does occur between Formica ants. Second, the frequent sharing of identical Wolbachia strains by distant mitochondrial lineages within the F. rufa group further shows that horizontal transmission has occurred repeatedly. Nevertheless, our dataset also provides some evidence for longer- term persistence of infection, indicating that Wolbachia infection within this host clade has been shaped by both horizontal and vertical transmission of symbionts. The fact that all the ants were infected irrespective of the family structure of their societies gives no support to the proposed hypotheses that the spreading of Wolbachia in ants might be associated to the types of their societies

Going nuclear: gene family evolution and vertebrate phylogeny reconciled

Gene duplications have been common throughout vertebrate evolution, introducing paralogy and so complicating phylogenctic inference from nuclear genes. Reconciled trees are one method capable of dealing with paralogy, using the relationship between a gene phylogeny and the phylogeny of the organisms containing those genes to identify gene duplication events. This allows us to infer phylogenies from gene families containing both orthologous and paralogous copies. Vertebrate phylogeny is well understood from morphological and palaeontological data, but studies using mitochondrial sequence data have failed to reproduce this classical view. Reconciled tree analysis of a database of 118 vertebrate gene families supports a largely classical vertebrate phylogeny

SlWUS1; An X-linked Gene Having No Homologous Y-Linked Copy in Silene latifolia

The dioecious plant Silene latifolia has heteromorphic sex chromosomes, and comparison of the positions of sex-linked genes indicates that at least three large inversions have occurred during the evolution of the Y chromosome. In this article, we describe the isolation of a new sex-linked gene from S. latifolia, which provides new information on the evolution of this plant’s young sex chromosomes. By using reverse-transcription polymerase chain reaction degenerate primers based on the Arabidopsis thaliana sequence of WUSCHEL, a flower-development gene, we found two copies in S. latifolia, which we named SlWUS1 and SlWUS2. Southern blot and genetic segregation analysis showed that SlWUS1 is located on the X chromosome and SlWUS2 is autosomal. No Y-linked copy of SlWUS1 was found by either Southern blot analysis under low-stringency conditions or polymerase chain reaction with degenerate primers, so we conclude that SlWUS1 probably has no Y-linked homolog. It is unknown whether the Y chromosome lost the SlWUS1 copy by degeneration of this individual gene or whether deletion of a larger genome region was involved. Several tests lead us to conclude that dosage compensation has not evolved for this sex-linked gene. We mapped the ortholog in the nondioecious relative S. vulgaris (SvWUS1), to compare the location in a species that has no history of having sex chromosomes. SvWUS1 maps to the same linkage group as other fully X-linked genes, indicating that it was not added to the X, but was lost from the Y. Its location differs in the maps from the two species, raising the possibility that the X chromosome, as well as the Y, may have been rearranged

Elokuvan katselun aktivoimien aivoverkostojen ajallispaikallinen erottelu

Niin levon kuin tehtävän suorituksen aikana aktiiviset, toisiinsa toiminnallisesti kytkeytyneet aivoalueet, eli nk. lepoverkostot, ovat yksi nykyaikaisen aivotutkimuksen erityisistä mielenkiinnon kohteista. Ensimmäiseksi havaittiin motorinen verkosto, minkä jälkeen on löydetty monia muita aivoverkostoja. Tässä diplomityössä tutkittiin sensorimotorista ja dorsaalista tarkkaavaisuus verkostoa sekä nk. default mode -verkostoa. Nämä kolme aivoverkostoa erotettiin 15 minuutin pituisen elokuvan ("At Land", Maya Deren) katselun aikana 15 koehenkilöltä kerätystä fMRI-datasta riippumattomien komponenttien analyysillä (ICA). Estimoitujen riippumattomien komponenttien (IC) lukumäärän vaikutusta ryhmä-ICAn tuloksiin tarkasteltiin kolmella eri komponenttimäärällä. ICAlla löydettyjen aivoverkostojen toiminnallinen yhteys todettiin myös lähdekorrelaatiomenetelmällä. Korrelaatioanalyysin (ISC) avulla paikannettiin ärsykkeeseen liittyvät aivoalueet ja ICt järjestettiin ISC-kartan avulla. Näin pystyttiin tunnistamaan ärsykkeeseen reagoivat komponentit, joiden aikasarjoja verrattiin elokuvan tapahtumiin. Pienellä komponenttimäärällä (25) sensorimotorista ja tarkkaavaisuusverkostoa vastaavat komponentit sisälsivät myös näihin verkostoihin kuulumattomia aivoalueita. Kun komponenttimäärää kasvatettiin (40), ylimääräiset alueet erottuivat omiksi verkostoikseen, josta voitiin olettaa, että tämä komponenttimäärä oli lähellä oikeaa. Suurella komponenttimäärällä (70) aivoverkostot jakaantuivat pienempiin osiin. Vaikka spatiaalinen jakaantuminen oli fysiologisesti mielekästä, komponenttien aikasarjat vääristyivät liian suurella komponenttimäärällä. Tämän työn tulokset auttavat ymmärtämään, miten riippumattomien komponenttien lukumäärä vaikuttaa ryhmä-ICAn tuloksiin. Tuloksia voidaan soveltaa oikean komponenttimäärän kokeellisessa etsimisessä ryhmä-fMRI datasta.So called resting state networks (RSNs), i.e. functionally connected brain areas that are active both during rest and task conditions, are receiving growing attention in modern brain research. The first observed RSN was the motor network. Since then, several different cortical networks have been identified. In this thesis the focus was on the sensorimotor, dorsal attention and default-mode networks. Independent component analysis (ICA) was used to segregate the three cortical networks from fMRI data collected from 15 subjects who were watching a 15 minutes long film ("At land" by Maya Deren). ICA was performed at three different dimensionalities and the effect of increasing the number of component estimates was examined. The functional connectivity between brain areas occupied by the three networks was examined also with seed-based correlation. The stimulus-related brain areas were indentified with intersubject correlation (ISC) analysis and the ICs were sorted according to the spatial overlap with the ISC map. The time courses of the most stimulus related ICs were compared with events in the movie. At a low dimensionality of ICA (25), the ICs representing the sensorimotor and dorsal attention networks included brain areas that do not belong to the networks. With an intermediate number of components (40) the additional areas were separated from the networks. This dimensionality was apparently closest to the correct one. When the dimensionality was further increased (70), the networks split into subcomponents. Although the spatial splitting was physiologically sensible, the time courses of the ICs got distorted at a too high dimensionality. The results of this work contribute to understanding how the number of components affects the group-ICA results and how the correct number of ICs could be empirically controlled in group-fMRI data

Activation of Auditory Cortex by Anticipating and Hearing Emotional Sounds: An MEG Study

To study how auditory cortical processing is affected by anticipating and hearing of long emotional sounds, we recorded auditory evoked magnetic fields with a whole-scalp MEG device from 15 healthy adults who were listening to emotional or neutral sounds. Pleasant, unpleasant, or neutral sounds, each lasting for 6 s, were played in a random order, preceded by 100-ms cue tones (0.5, 1, or 2 kHz) 2 s before the onset of the sound. The cue tones, indicating the valence of the upcoming emotional sounds, evoked typical transient N100m responses in the auditory cortex. During the rest of the anticipation period (until the beginning of the emotional sound), auditory cortices of both hemispheres generated slow shifts of the same polarity as N100m. During anticipation, the relative strengths of the auditory-cortex signals depended on the upcoming sound: towards the end of the anticipation period the activity became stronger when the subject was anticipating emotional rather than neutral sounds. During the actual emotional and neutral sounds, sustained fields were predominant in the left hemisphere for all sounds. The measured DC MEG signals during both anticipation and hearing of emotional sounds implied that following the cue that indicates the valence of the upcoming sound, the auditory-cortex activity is modulated by the upcoming sound category during the anticipation period.Peer reviewe

Counting Coalescent Histories

Given a species tree and a gene tree, a valid coalescent history is a list of the branches of the species tree on which coalescences in the gene tree take place. I develop a recursion for the number of valid coalescent histories that exist for an arbitrary gene tree/species tree pair, when one gene lineage is studied per species. The result is obtained by defining a concept of m-extended coalescent histories, enumerating and counting these histories, and taking the special case of m = 1. As a sum over valid coalescent histories appears in a formula for the probability that a random gene tree evolving along the branches of a fixed species tree has a specified labeled topology, the enumeration of valid coalescent histories can considerably reduce the effort required for evaluating this formula.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63175/1/cmb.2006.0109.pd

Nestmate recognition and the genetic relatedness of nests in the ant Formica pratensis

Genetic relatedness of the mound-building ant Formica pratensis was determined by means of microsatellite DNA polymorphism, and its impact on nestmate recognition was tested in a population in Southern Sweden (Oeland). Recognition between nests was measured by testing aggression levels between single pairs of workers. The genetic distances of nests (Nei's genetic distance) and the spatial distance of nests were correlated and both showed a strong relation to the aggression behavior. Multiple regression analysis revealed a stronger impact of genetic relatedness rather than spatial distances on aggression behavior. Neighbouring nests were more closely related than distant nests, which may reflect budding as a possible spreading mechanism. The genetic distance data showed that nestmate recognition was strongly genetically influenced in F. pratensis

Pheromonal and enzyme genetic characteristics of the Bombus lucorum species complex in northern Europe

Spatial and temporal distribution of the species in the Bombus lucorum species complex, B. lucorum (L.), B. cryptarum (Fabricius) and B. magnus Vogt, were studied in Finland. Morphological distinction between the species is not as clear as in Central Europe, but B. lucorum can be distinguished from the other two with the help of enzyme genetic markers. B. lucorum is the most common of the three species in most of Finland, and B. cryptarum is abundant in the southwestern coastal area and in northern Lapland. B. magnus was only rarely found among the spring queens in southwestern Finland, and its range possibly restricts to southern and central parts of Finland. A comparison of the chemical composition of the male labial glands and enzyme genotypes shows that males produce species-specific marking pheromones

Functional Subdivision of Group-ICA Results of fMRI Data Collected during Cinema Viewing

Independent component analysis (ICA) can unravel functional brain networks from functional magnetic resonance imaging (fMRI) data. The number of the estimated components affects both the spatial pattern of the identified networks and their time-course estimates. Here group-ICA was applied at four dimensionalities (10, 20, 40, and 58 components) to fMRI data collected from 15 subjects who viewed a 15-min silent film (“At land” by Maya Deren). We focused on the dorsal attention network, the default-mode network, and the sensorimotor network. The lowest dimensionalities demonstrated most prominent activity within the dorsal attention network, combined with the visual areas, and in the default-mode network; the sensorimotor network only appeared with ICA comprising at least 20 components. The results suggest that even very low-dimensional ICA can unravel the most prominent functionally-connected brain networks. However, increasing the number of components gives a more detailed picture and functionally feasible subdivision of the major networks. These results improve our understanding of the hierarchical subdivision of brain networks during viewing of a movie that provides continuous stimulation embedded in an attention-directing narrative.Peer reviewe