Food webs in the era of molecular revolution – Like resolving the Gordian knot with a tricorder

Living nature consists of countless organisms, which are classified into millions of species. These species interact in many ways; for example predators when foraging on their prey, insect larvae consuming plants, and pathogenic bacteria drifting into humans. In addition, abiotic nature has a great initiative impact on life through many factors (including sunlight, ambient temperature, and water. In my thesis, I have studied interactions among different life forms in multifaceted ways. The webs of these interactions are commonly referred to as food webs, describing feeding relationships between species or energy transfer from one trophic level to another. These ecological interactions – whether they occur between species, between individuals, or between microorganisms within an individual – are among the greatest forces affecting natural communities. Relationships are tightly related to biological diversity, that is, species richness and abundances. A species is called a node in food web vocabulary, and its interactions to other species are called links. Generally, Artic food webs are considered to be loosely linked, simple structures. This conception roots into early modern food webs, where insects and other arthropods, for example, were clumped under one node. However, it has been shown that arthropods form the greatest part of diversity and biomass both in the tropics and in Arctic areas. Earlier challenges of revealing the role of insects and microorganisms in interactions webs have become possible with the help of recent advances in molecular techniques. In the first chapter, I studied the prey diversity of a common bat, Myotis daubentonii, in southwestern Finland. My results proved M. daubentonii being a versatile predator whose diet mainly consists of aquatic insects, such as chironomid midges. In the second chapter, I expanded the view to changes in seasonal and individual-based variation in the diet of M. daubentonii including the relationship between available and observed prey. I found out that chironomids remain the major prey group even though their abundance decreases in proportion to other insect groups. Diet varied a lot between individuals, although the differences were not statistically significant. The third chapter took the study to a large network in Greenland. I showed that Artic food webs are very complex when arthropods are taken into account. In the fourth chapter, I examined the bacterial flora of M. daubentonii and surveyed the zoonotic potential of these bacteria. I found Bartonella bacteria, of which one was described as a new species named after the locality of discovery. I have shown in my thesis that Myotis daubentonii as a predator links many insect species as well as terrestrial and aquatic environments. Moreover, I have exposed that Arctic food webs are complex structures comprising of many densely linked species. Finally, I demonstrated that the bacterial flora of bats includes several previously unknown species, some of which could possibly turn in to zoonosis. To summarize, molecular methods have untied several knots in biological research. I hope that this kind of increasing knowledge of the surrounding nature makes us further value all the life forms on earth.Ravintoverkot DNA:n aikakaudella – kuin ratkoisi Gordionin solmua tricorder-laitteella Elollinen luonto koostuu lukemattomista organismeista, jotka luokitellaan miljooniin eri lajeihin. Nämä organismit ovat vuorovaikutuksessa keskenään monin tavoin; esimerkiksi pedot saalistaessaan, hyönteisten toukat syödessään ravintokasviaan, sekä toisaalta myös taudinaiheuttajabakteerit kulkeutuessaan ihmiseen. Myös niin kutsutulla elottomalla luonnolla on suuri alkuunpaneva vaikutus elolliseen luontoon eri tekijöiden kautta (muun muassa auringonvalo, lämpötila ja vesi). Olen väitöskirjassani tutkinut monipuolisesti eliöiden välisiä vuorovaikutuksia. Näiden vuorovaikutusten verkkoa kutsutaan yleisesti ravintoverkoiksi, kuvaten lajien välisiä syömissuhteita tai energian liikettä ravintotasolta toiselle. Juuri nämä ekologiset vuorovaikutukset – tapahtuvat ne sitten lajien tai yksilöiden välillä tai mikro-organismien välillä yksilön sisällä – ovat suurimpia eliöyhteisöä muokkaavia voimia. Vuorovaikutukset ovat kiinteässä suhteessa biologiseen monimuotoisuuteen, eli lajien määrään ja lajimäärien suhteisiin. Laji kuvataan ravintoverkossa solmukohtana, jonka vuorovaikutussuhteita muihin lajeihin merkitään yhdistävillä viivoilla, linkeillä. Yleisesti on ajateltu, että arktiset ravintoverkot ovat yksinkertaisia, koostuen vain muutamista solmuista ja niitä yhdistävistä harvoista linkeistä. Tämä käsitys on juontanut juurensa ensimmäisiin ravintoverkkoihin, joissa esimerkiksi hyönteiset ja muut niveljalkaiset oli kerätty yhden otsikon alle. Kuitenkin, monissa tutkimuksissa on osoitettu, että hyönteiset muodostavat sekä lajimäärältään että biomassaltaan vallitsevan ryhmän sekä tropiikissa että arktisilla alueilla. Aiemmin haasteelliseksi osoittautunut hyönteisten ja mikro-organismien roolien selvittäminen ravintoverkoissa on molekyylimenetelmien kehittymisen myötä tuonut uusia mahdollisuuksia ekologiseen tutkimukseen. Ensimmäisessä osatyössäni tutkin Suomessa yleisen lepakon, vesisiipan, ravintoa Varsinais-Suomen alueella. Tulokset osoittivat, että vesisiippa on erittäin monipuolinen peto, jonka pääasiallisen ravinnon muodostavat vedestä kuoriutuvat hyönteiset, erityisesti surviaissääsket. Toisessa työssäni laajensin vesisiipan ravinnonkäytön tutkimusta ajallisen ja yksilöiden välisen vaihtelun selvittämiseen sekä saatavilla olevan ravinnon suhdetta saaliiseen. Tulosten perusteella näyttää siltä, että surviaissääsket säilyttävät asemansa tärkeimpänä ravintokohteena, vaikka niiden määrä suhteessa muuhun ravintoon laskee syksyn edetessä. Ruokavalio vaihteli paljon yksilöiden välillä, tosin vaihtelu ei saavuttanut tilastollista merkitsevyyttä. Kolmannessa osatyössä tutkin laajaa ravintoverkkokokonaisuutta Grönlannissa. Löysin todisteita siitä, että arktiset ravintoverkot ovat erittäin monimutkaisia, eli lajien välillä on paljon vuorovaikutusyhteyksiä. Neljännessä työssäni tutkin vesisiipan bakteerilajistoa, sekä kartoitin löytyneiden bakteerien zoonoosi-potentiaalia. Löysin Bartonella-bakteereja, joista kuvasin yhden tieteelle uuden lajin löytöpaikan mukaan. Olen väitöskirjassani osoittanut, että vesisiippa petona yhdistää monia hyönteislajeja sekä terrestrisen ja akvaattisen ympäristön. Olen myös näyttänyt, että arktiset ravintoverkot koostuvat monimutkaisesti linkittyneistä eliöistä. Lisäksi osoitin, että lepakoiden bakteerilajisto sisältää paljon ennestään tuntemattomia bakteereja, joista osa saattaa olla ihmisellekin vaaraksi. Tiivistäen, molekyylimenetelmät ovat avanneet monia solmuja biologisessa tutkimuksessa. Toivonkin, että tämänkaltainen tiedon lisääntyminen ympäröivästä maailmasta lisää arvostustamme kaikkea elämän monimuotoisuutta kohtaan.Siirretty Doriast

Microclimate structures communities, predation and herbivory in the High Arctic

1. In a warming world, changes in climate may result in species-level responses as well as changes in community structure through knock-on effects on ecological interactions such as predation and herbivory. Yet, the links between these responses at different levels are still inadequately understood. Assessing how microclimatic conditions affect each of them at local scales provides information essential for understanding the consequences of macroclimatic changes projected in the future.2. Focusing on the rapidly changing High Arctic, we examine how a community based on a common resource species (avens, Dryas spp.), a specialist insect herbivore (Sympistis zetterstedtii) and natural enemies of lepidopteran herbivores (parasitoids) varies along a multidimensional microclimatic gradient. We ask (a) how parasitoid community composition varies with local abiotic conditions, (b) how the community-level response of parasitoids is linked to species-specific traits (koino- or idiobiont life cycle strategy and phenology) and (c) whether the effects of varying abiotic conditions extend to interaction outcomes (parasitism rates on the focal herbivore and realized herbivory rates).3. We recorded the local communities of parasitoids, herbivory rates on Dryas flowers and parasitism rates in Sympistis larvae at 20 sites along a mountain slope. For linking community-level responses to microclimatic conditions with parasitoid traits, we used joint species distribution modelling. We then assessed whether the same abiotic variables also affect parasitism and herbivory rates, by applying generalized linear and additive mixed models.4. We find that parasitism strategy and phenology explain local variation in parasitoid community structure. Parasitoids with a koinobiont strategy preferred high-elevation sites with higher summer temperatures or sites with earlier snowmelt and lower humidity. Species of earlier phenology occurred with higher incidence at sites with cooler summer temperatures or later snowmelt. Microclimatic effects also extend to parasitism and herbivory, with an increase in the parasitism rates of the main herbivore S. zetterstedtii with higher temperature and lower humidity, and a matching increase in herbivory rates.5. Our results show that microclimatic variation is a strong driver of local community structure, species interactions and interaction outcomes in Arctic ecosystems. In view of ongoing climate change, these results predict that macroclimatic changes will profoundly affect arctic communities

Atmospheric humidity affects global variation of bat echolocation via indirect effects

The peak frequency of bat echolocation is a species-specific functional trait linked to foraging ecology. It is tailored via evolution to suit conditions within the distribution range of each species, but the evolutionary drivers are not yet well-understood. Global patterns of humidity correlate with many aspects of bat ecology. We hypothesized that atmospheric absolute humidity could explain global peak frequency variation directly and indirectly via increasing species body size and bat species richness. These hypotheses were tested using Bayesian phylogenetic path analysis on 226 tropical and subtropical bat species. In line with our predictions, we found a positive total effect of humidity on peak frequency, which was dominated by the positive indirect effects via body size and bat species richness. We did not observe the negative direct effect of humidity on peak frequency, which was hypothesized based on atmospheric attenuation of sound. In line with our expectations, excluding the predominantly clutter foraging bat families from our dataset downplayed the importance of the richness-mediated route. To conclude, our findings suggest that indirect effects, owing to ecology and biogeography of bat taxa, play a major role in the global relationship between peak frequency and atmospheric humidity.Peer reviewe

Arthropod Communities on Young Vegetated Roofs Are More Similar to Each Other Than to Communities at Ground Level

Vegetated roofs are human-manufactured ecosystems and potentially promising conservation tools for various taxa and habitats. Focussing on arthropods, we conducted a 3 year study on newly constructed vegetated roofs with shallow substrates (up to 10 cm) and vegetation established with pre-grown mats, plug plants and seeds to describe pioneer arthropod communities on roofs and to compare them with ground level communities. We vacuum sampled arthropods from the roofs and nearby ground level sites with low, open vegetation, i.e., potential source habitats. We showed that the roofs and ground sites resembled each other for ordinal species richness but differed in community composition: with time the roofs started to resemble each other rather than their closest ground level habitats. Species richness increased with time on roofs and at ground level, but the roofs had consistently less species than the ground sites and only a few species were unique to the roofs. Also, the proportion of predators increased on roofs, while not at ground level. We conclude that vegetated roofs established with similar substrates and vegetation, filter arthropods in a way that produces novel communities that are different from those at ground level but similar to one another. The role of these insular communities in species networks and ecosystem function remains to be investigated

First record of an indoor pest sawtoothed grain beetle Oryzaephilus surinamensis (Coleoptera: Silvanidae) from wild outdoor wood ant nest

Alive individual adult sawtoothed grain beetle Oryzaephilus surinamensis (Linnaeus, 1758) was discovered inside a nest mound of the red wood ant Formica rufa Linnaeus, 1758 during a survey of myrmecophilous invertebrates. The sawtoothed grain beetle is a widespread indoor pest that has not previously been found in an ant nest. It is one of the most common pests in stored grain and cereal products, but the natural life-style of the species is not known. As the site of discovery was exceptional, we verified the species identification using the DNA barcode. If the sawtoothed grain beetle can live in mounds of red wood ants, the mounds may become widespread source habitats for the future infestations of this serious stored product pest

A global class reunion with multiple groups feasting on the declining insect smorgasbord

We report a detection of a surprising similarity in the diet of predators across distant phyla. Though just a first glimpse into the subject, our discovery contradicts traditional aspects of biology, as the earliest notions in ecology have linked the most severe competition of resources with evolutionary relatedness. We argue that our finding deserves more research, and propose a plan to reveal more information on the current biodiversity loss around the world. While doing so, we expand the recently proposed conservation roadmaps into a parallel study of global interaction networks.Peer reviewe

Optimisation of variables for studying dilepton transverse momentum distributions at hadron colliders

In future measurements of the dilepton ($Z/\gamma^*$) transverse momentum, \Qt, at both the Tevatron and LHC, the achievable bin widths and the ultimate precision of the measurements will be limited by experimental resolution rather than by the available event statistics. In a recent paper the variable \at, which corresponds to the component of \Qt\ that is transverse to the dilepton thrust axis, has been studied in this regard. In the region, \Qt\ $<$ 30 GeV, \at\ has been shown to be less susceptible to experimental resolution and efficiency effects than the \Qt. Extending over all \Qt, we now demonstrate that dividing \at\ (or \Qt) by the measured dilepton invariant mass further improves the resolution. In addition, we propose a new variable, \phistarEta, that is determined exclusively from the measured lepton directions; this is even more precisely determined experimentally than the above variables and is similarly sensitive to the \Qt. The greater precision achievable using such variables will enable more stringent tests of QCD and tighter constraints on Monte Carlo event generator tunes.Comment: 8 pages, 5 figures, 2 table

Technical note: Analytical formulae for the critical supersaturations and droplet diameters of CCN containing insoluble material

International audienceIn this paper, we consider the cloud drop activation of aerosol particles consisting of water soluble material and an insoluble core. Based on the Köhler theory, we derive analytical equations for the critical diameters and supersaturations of such particles. We demonstrate the use of the equations by comparing the critical supersaturations of particles composed of ammonium sulfate and insoluble substances with those of model organic particles with varying molecular sizes