Environmental Variation, Niches of Indicator Species and Forest Structure in Amazonia

Amazonia is the largest remaining tropical rainforest. As such, it is globally important both in terms of carbon and water cycles as well as biodiversity. As in most areas of the tropics, deforestation is also alarmingly fast in the Amazon. Rainforests are subject to many types of land use pressures, such as food production, mining and timber extraction. Although the rainforest area looks quite uniform in aerial photographs, the soil in the area is remarkably variable. This variation, in turn, is reflected in the variation of species composition. There are also regional differences in the structure of the forest. Mapping the variation in soils and species composition is particularly important in conditions of rapidly advancing deforestation, as soil properties affect productivity - both the productivity of the original forest ecosystem and food production. The properties of the soil also affect the assemblage of species present in the area. Large variability of the soil often also means a great variety of forest types and thus a regionally high number of species. Mapping is therefore also important for conservation purposes. The extent of Amazonia and the inaccessibility of many areas, the large number of species and the lack of knowledge about species ecology have slowed down the mapping. The use of indicator species is an effective way to speed up mapping. In this dissertation, I use two large datasets on Amazonian indicator species collected over the last three decades. I draw from the long tradition of Europe's deciduous and coniferous forest zones, where indicator species are used to indicate soil fertility and forest type. I am looking into whether the same could be applied in Amazonia. I look for potential indicator species by modelling their ecological niches in relation to an important soil variable, the concentration of base cations. I also study general plant ecological questions, such as whether common and abundant species are always ecologically wide-ranging generalists. For these purposes, I use HOF models and weighted averaging. I test how accurately different soil properties can be predicted with indicator species. In prediction, I apply the k-nearest neighbour method (k-NN) and weighted averaging calibration. I also study the influence soil has on the structure of the lowland rainforest understorey. I carry out field measurements of stem density in different size classes of trees, and of canopy openness. In the cloud forests of the Andean slopes, I study the relationship between the forest structure and microclimate, and their effect on the abundance and diversity of epiphytic plants. I carry out forest structure measurements and estimate the abundance of epiphytes in the field and record the microclimate with automatic data loggers. In five research papers, I find out that: 1) Both the Melastomataceae family and the fern genera Adiantum and Lindsaea contain several promising indicator species. In addition, the optima of the species in both groups are spread along the base cation gradient in such a way that several narrowniche indicator species exist in all parts of the gradient, 3) Locally abundant species are not always ecological generalists, but can also be specialised to a certain soil type, 3) Soil base cation concentration can be accurately predicted using indicator, but it is also possible to predict the potassium content quite accurately. Regarding other soil variables, the method is not as good, 4) The differences in forest structure between different soil types prove to be difficult to verify with field measurements, but differences have later been found with remote sensing methods, 5) The conditions in the premontane cloud forest become less favourable for epiphytes with increasing canopy openness. This development is reinforced by both climate change and deforestation.Amazonia on laajin jäljellä oleva trooppinen sademetsäalue. Sellaisena se on globaalisti tärkeä niin hiilen ja veden kiertokulkujen kuin luonnon monimuotoisuudenkin kannalta. Kuten useimmilla tropiikin alueilla, metsäkato on myös Amazoniassa huolestuttavan nopeaa. Sademetsiin kohdistuu monenlaisia maankäyttöpaineita, kuten ravinnontuotantoa, kaivostoimintaa ja puutavaran hankintaa. Vaikka sademetsäalue näyttää ilmakuvissa varsin yhtenäiseltä, alueen maaperä on huomattavan vaihtelevaa. Tämä vaihtelu puolestaan heijastuu eliölajiston vaihteluun. Myös metsän rakenteessa on alueellisia eroja. Maaperä- ja lajistovaihtelun kartoittaminen on nopeasti etenevän metsäkadon oloissa erityisen tärkeää, sillä maaperän ominaisuudet vaikuttavat tuottavuuteen – niin alkuperäisen metsäekosysteemin tuottavuuteen kuin ravinnontuotantoonkin. Maaperän ominaisuudet vaikuttavat myös siihen, minkä tyyppistä lajistoa alueella esiintyy. Maaperän suuri vaihtelevuus merkitsee usein myös suurta metsätyyppien vaihtelua ja siten alueellisesti korkeaa lajimäärää. Kartoitus on siten tärkeää myös lajiston suojelun kannalta. Kartoituksen hidasteena on ollut Amazonian laajuus ja monien alueiden vaikeapääsyisyys, suuri lajimäärä ja puutteellinen tieto alueen lajiston ekologiasta. Indikaattorilajien eli ilmaisinlajien käyttö on tehokas tapa nopeuttaa kartoitusta. Tässä väitöskirjassa käytän kahta suurta, viimeisten kolmen vuosikymmenen aikana kerättyä aineistoa Amazonian indikaattorilajeista. Ammennan Euroopan lehti- ja havumetsävyöhykkeiden pitkästä perinteestä, jossa indikaattorilajeja käytetään maaperän viljavuuden ja metsätyypin osoittamiseen. Tutkin, voitaisiinko samaa soveltaa Amazoniassa. Etsin potentiaalisia indikaattorilajeja mallintamalla niiden ekologisia lokeroita tärkeän maaperämuuttujan, emäskationikonsentraation, suhteen. Tutkin myös yleisiä kasviekologisia kysymyksiä, kuten sitä, ovatko yleiset ja runsaat lajit aina ekologisesti laaja-alaisia generalisteja. Näihin tarkoituksiin käytän HOF-malleja ja painotetun keskiarvon menetelmää. Testaan, kuinka tarkasti indikaattorilajeilla voi ennustaa erilaisia maaperän ominaisuuksia. Ennustamisessa sovellan k-lähin naapuri -menetelmää (k-NN) ja painotettua keskiarvokalibrointia. Tutkin myös maaperän vaikutusta alankosademetsän rakenteeseen. Suoritan maastomittauksia, joissa selvitän puiden tiheyttä eri kokoluokissa sekä latvuksen aukkoisuutta. Andien rinteiden pilvimetsissä tutkin metsän rakenteen ja mikroilmaston välistä yhteyttä, ja näiden vaikutusta epifyyttisten kasvien runsauteen ja monimuotoisuuteen. Suoritan maastossa metsän rakenteen ja epifyyttien runsauden mittauksia, ja automaattisten tallentimien avulla mikroilmaston seurantaa. Yhteensä viidessä osatyössä saan selville, että: 1) Sekä Melastomataceae -heimo että Adiantum ja Lindsaea -saniaissuvut sisältävät useita lupaavia indikaattorilajeja. Lisäksi kummankin ryhmän lajien optimit asettuvat emäskationigradientille siten, että mihin tahansa gradientin osaan tulee useita kapea-alaisia indikaattorilajeja, 2) Paikallisesti runsaat lajit eivät ole aina generalisteja, vaan ne voivat olla myös erikoistuneita tiettyyn maaperätyyppiin, 3) Etenkin emäskationikonsentraation ennustaminen indikaattorilajien avulla on varsin tarkkaa, mutta myös kaliumpitoisuutta on mahdollista ennustaa melko tarkasti. Muiden maaperämuuttujien suhteen menetelmä ei ole yhtä hyvä, 4) Metsän rakenteen erot eri maaperätyyppien välillä osoittautuvat vaikeiksi todentaa maastomittauksin, mutta eroja on myöhemmin löydetty kaukokartoitusmenetelmin, 5) Vuoristosademetsän olosuhteet muuttuvat epifyyteille epäsuotuisammiksi, kun latvuksen aukkoisuus lisääntyy. Tätä kehityskulkua vahvistavat sekä ilmastonmuutos että metsien hakkuut

Search for top-down and bottom-up drivers of latitudinal trends in insect herbivory in oak trees in Europe

International audienceAim: The strength of species interactions is traditionally expected to increase toward the Equator. However, recent studies have reported opposite or inconsistent latitudinal trends in the bottom-up (plant quality) and top-down (natural enemies) forces driving herbivory. In addition, these forces have rarely been studied together thus limiting previous attempts to understand the effect of large-scale climatic gradients on herbivory. Location: Europe. Time period: 2018–2019. Major taxa studied: Quercus robur. Methods: We simultaneously tested for latitudinal variation in plant–herbivore–natural enemy interactions. We further investigated the underlying climatic factors associated with variation in herbivory, leaf chemistry and attack rates in Quercus robur across its complete latitudinal range in Europe. We quantified insect leaf damage and the incidence of specialist herbivores as well as leaf chemistry and bird attack rates on dummy caterpillars on 261 oak trees. Results: Climatic factors rather than latitude per se were the best predictors of the large-scale (geographical) variation in the incidence of gall-inducers and leaf-miners as well as in leaf nutritional content. However, leaf damage, plant chemical defences (leaf phenolics) and bird attack rates were not influenced by climatic factors or latitude. The incidence of leaf-miners increased with increasing concentrations of hydrolysable tannins, whereas the incidence of gall-inducers increased with increasing leaf soluble sugar concentration and decreased with increasing leaf C : N ratios and lignins. However, leaf traits and bird attack rates did not vary with leaf damage. Main conclusions: These findings help to refine our understanding of the bottom-up and top-down mechanisms driving geographical variation in plant–herbivore interactions, and indicate the need for further examination of the drivers of herbivory on trees

Search for top-down and bottom-up drivers of latitudinal trends in insect herbivory in oak trees in Europe

AimThe strength of species interactions is traditionally expected to increase toward the Equator. However, recent studies have reported opposite or inconsistent latitudinal trends in the bottom‐up (plant quality) and top‐down (natural enemies) forces driving herbivory. In addition, these forces have rarely been studied together thus limiting previous attempts to understand the effect of large‐scale climatic gradients on herbivory.LocationEurope.Time period2018–2019.Major taxa studiedQuercus robur.MethodsWe simultaneously tested for latitudinal variation in plant–herbivore–natural enemy interactions. We further investigated the underlying climatic factors associated with variation in herbivory, leaf chemistry and attack rates in Quercus robur across its complete latitudinal range in Europe. We quantified insect leaf damage and the incidence of specialist herbivores as well as leaf chemistry and bird attack rates on dummy caterpillars on 261 oak trees.ResultsClimatic factors rather than latitude per se were the best predictors of the large‐scale (geographical) variation in the incidence of gall‐inducers and leaf‐miners as well as in leaf nutritional content. However, leaf damage, plant chemical defences (leaf phenolics) and bird attack rates were not influenced by climatic factors or latitude. The incidence of leaf‐miners increased with increasing concentrations of hydrolysable tannins, whereas the incidence of gall‐inducers increased with increasing leaf soluble sugar concentration and decreased with increasing leaf C : N ratios and lignins. However, leaf traits and bird attack rates did not vary with leaf damage.Main conclusionsThese findings help to refine our understanding of the bottom‐up and top‐down mechanisms driving geographical variation in plant–herbivore interactions, and indicate the need for further examination of the drivers of herbivory on trees.</p

Similar understorey structure in spite of edaphic and floristic dissimilarity in Amazonian forests

Forest structure determines light availability for understorey plants. The structure of lowland Amazonian forests is known to vary over long edaphic gradients, but whether more subtle edaphic variation also affects forest structure has not beenresolved. In western Amazonia, the majority of non-flooded forests grow on soils derived either from relatively fertile sediments of the Pebas Formation or from poorer sediments of the Nauta Formation. The objective of this study was to compare structure and light availability in the understorey of forests growing on these two geological formations. We measured canopy openness and tree stem densities in three size classes in northeastern Peru in a total of 275 study points in old-growth terra firme forests representing the two geological formations. We also documented variation in floristic composition (ferns, lycophytes and the palm Iriartea deltoidea) and used Landsat TM satellite image information to model the forest structural and floristic features over a larger area. The floristic compositions of forests on the two formations were clearly different, and this could also be modelled with the satellite imagery. In contrast, the field observations of forest structure gave only a weak indication that forests on the Nauta Formation might be denser than those on the Pebas Formation. The modelling of forest structural features with satellite imagery did not support this result. Our results indicate that the structure of forest understorey varies much less than floristic composition does over the studied edaphic difference

Evidence of a causal effect of genetic tendency to gain muscle mass on uterine leiomyomata

Uterine leiomyomata (UL) are the most common tumours of the female genital tract and the primary cause of surgical removal of the uterus. Genetic factors contribute to UL susceptibility. To add understanding to the heritable genetic risk factors, we conduct a genome-wide association study (GWAS) of UL in up to 426,558 European women from FinnGen and a previous UL meta-GWAS. In addition to the 50 known UL loci, we identify 22 loci that have not been associated with UL in prior studies. UL-associated loci harbour genes enriched for development, growth, and cellular senescence. Of particular interest are the smooth muscle cell differentiation and proliferation-regulating genes functioning on the myocardin-cyclin dependent kinase inhibitor 1A pathway. Our results further suggest that genetic predisposition to increased fat-free mass may be causally related to higher UL risk, underscoring the involvement of altered muscle tissue biology in UL pathophysiology. Overall, our findings add to the understanding of the genetic pathways underlying UL, which may aid in developing novel therapeutics.Peer reviewe