Browsing by master's degree program "Magisterprogrammet i ekologi och evolutionsbiologi"

Metsätalouden seurauksena lahopuu on vähentynyt Suomen metsissä ja siten useat lahopuusta riippuvaiset lajit ovat päätyneet uhanalaisiksi. Lahopuun määrän lisäämiseksi metsähakkuiden yhteydessä on alettu jättämään säästöpuita ja tekopökkelöitä. Tekopökkelöt hyödyttävät lahotessaan lahopuusta riippuvaisia lajeja, kuten kolopesiviä myrkkypistiäisiä. Kolopesivät myrkkypistiäiset rakentavat pesänsä yleensä kovakuoriaisten puiden runkoihin kaivamiin koloihin. Tässä tutkimuksessa selvitettiin, millaista myrkkypistiäislajistoa tekopökkelöt tukevat, millaiset ja miten sijoitetut tekopökkelöt ovat hyödyllisimpiä myrkkypistiäisille, onko tekopökkelön vai ympäristön laatu merkittävämpää myrkkypistiäisille ja eroavatko eri ekologisten ryhmien (mesipistiäiset, petoina elävät myrkkypistiäiset ja pesäloiset) myrkkypistiäiset pesäpaikkavaatimuksiltaan. Tutkimuksen aineisto kerättiin kesällä 2021 Keski-Suomessa Viitasaarella, kuusivaltaisilta eri tavoin käsitellyiltä metsäkuviolta. Kuvioista kahdeksan oli harvennuksia, tuoreita päätehakkuita kahdeksan ja vanhoja päätehakkuita kymmenen. Tekopökkelöiden myrkkypistiäislajistoa tutkittiin keinopesien avulla. Keinopesät koostuivat muoviputkilosta, jonka sisällä oli eri kokoisia järviruo’on (Phragmites australis) korsia, monenlaisten myrkkypistiäislajien houkuttelemiseksi. Keinopesiä kiinnitettiin yhteensä 120 kappaletta teko- ja luonnonpökkelöihin, sekä kantoihin. Puulajeina oli kuusi ja koivu, sekä yksi haapa. Pökkelöistä ja metsäkuvioilta mitattiin niiden laatua kuvaavia muuttujia. Keinopesät olivat maastossa keväästä syksyyn, jolloin ne haettiin säilytykseen ulkovarastoon. Keinopesät siirrettiin huoneenlämpöön alkuvuonna 2022 pistiäisten aikuiseksi kehittymisen vauhdittamiseksi. Korret avattiin ja aikuiset myrkkypistiäiset tunnistettiin pesittäin lajilleen mikroskooppia apuna käyttäen. Tilastolliset analyysit suoritettiin R-Studiolla. Yksilö- ja lajimäärän muutoksia suhteessa selittäviin muuttujiin arvioitiin yleistetyillä lineaarisilla sekamalleilla (GLMM). Selittävinä muuttujina toimivat lämpötila, pökkelön korkeus, kaarnan peittävyys, alustan tyyppi, puulaji, lahopuun määrä, ravintokasvien määrä, hakkuutyyppi, pökkelön sijainti ja pesäkolojen määrä. Myrkkypistiäislajiyhteisöjen erilaisuutta arvioitiin NMDS-analyysillä. Sen avulla havainnollistettiin lajiyhteisöjen erilaisuutta eri hakkuutyyppien välillä. Keinopesistä löydettiin kolopesiviä myrkkypistiäisiä ja niiden myrkkypistiäispesäloisia yhteensä yli 3000 yksilöä. Petoina eläviä myrkkypistiäisiä löytyi eniten harvennusmetsistä, joissa oli alhaisempi lämpötila kuin tuoreilla ja vanhoilla päätehakkuilla. Mesipistiäisiä, jotka ruokailevat sekä toukka että aikuisvaiheessa medellä ja siitepölyllä, löytyi eniten tuoreilta ja vanhoilta päätehakkuilta. Näillä kuvioilla oli korkeamman lämpötilan lisäksi aurinkoisempaa ja enemmän ravintokasveja kuin harvennusmetsissä. Kaikkia myrkkypistiäisiä löytyi eniten korkeilta pökkelöiltä, joiden rungoilla oli vain vähän kaarnaa. Myrkkypistiäiset suosivat enemmän teko- ja luonnonpökkelöitä kuin kantoja. Pökkelön ympäristön ominaisuudet olivat kuitenkin tärkeämpiä kuin pökkelön ominaisuudet niin lajimäärälle kuin yksilörunsaudelle. Koska eri ekologisten ryhmien lajit suosivat erilaisia elinympäristöjä, tekopökkelöitä kannattaa jatkossakin tehdä sekä pääte- että harvennushakkuiden yhteydessä. Tekopökkelöitä tehdessä kannattaa myös huomioida niiden monipuolinen sijoittuminen reunoille ja keskelle hakkuuta, jotta niitä jää hakkuualueelle monenlaisiin ympäristöoloihin. Tekopökkelö tulisi katkaista mahdollisimman korkealta, sillä korkeisiin pökkelöihin mahtuu enemmän pesiä kuin mataliin ja matalat pökkelöt ovat alttiimpia kosteudelle, sekä pesien homehtumiselle kuin korkeat pökkelöt.

Lake ecosystems are shaped by water chemistry processes that affect the lake environment and the species communities within. Changes in the water chemistry thus have far-reaching consequences. Water colour is one variable that affects water chemistry and stems from humic substances in the water. Dark water reduces light availability and also affects nutrient and oxygen availability. A trend of brownification of freshwater systems has been observed in recent years and it is expected to influence species community’s diversity and composition. The aim of this thesis was to study whether brownification is an ongoing issue in the study lakes and whether it has had a negative effect on phytoplankton diversity and resulted in shifts in the phytoplankton composition. A data set including about a 100 lakes in Finland with measurements from 1965 up until now served as the study system which was analysed with statistical methods. The results indicated a brownification trend in the past decades. The brownification so far had a positive impact on species richness but a negative impact on beta diversity. Brownification also affected species composition. Flagellates and autotrophic species increased in darker waters but mixotrophic species that are known to dominate in dark water colour, did not show a clear increase with water colour. Other hydrological variables than water colour could have had a bigger impact on the phytoplankton community than water colour but future monitoring of the phytoplankton community is recommended to see if water colour will have a negative impact on species diversity in the future.

Fear has far-reaching physiological and behavioural effects for animals, altering their foraging efficiency, parental care and breeding success. Extensive research shows that an animal’s perceived risk of predation, for example, can have fitness effects equivalent to direct killing. However, less work has explored the effects of fear induced by other natural enemies. Here I investigated by field experiment how the perceived risk of brood parasitism by common cuckoos (Cuculus canorus) affects behaviour of reed warblers (Acrocephalus scirpaceus), one of the favourite host species. Previous work shows that reed warblers upregulate behavioural defences based on social information about parasitism risk, but it is not known whether this alters their behaviour outside of an encounter with a cuckoo. Therefore, I manipulated social information about parasitism risk using models and alarm-call playbacks, and measured differences in vigilance behaviour depending on the amount of social information provided (high, medium, low, no risk). I found that vigilance increased when the perception of parasitism risk increased, both during social information presentations and 6 days later during incubation (when the nest is no longer at risk of parasitism). The findings suggest that when perceived risks are high, incubation behaviour is adapted to reduce parasitism risk. Additionally, the cues indicating increased parasitism risk reduced the fledging success, possibly due to the increased stress and the time allocated into vigilance rather than parental care. Therefore, these changes in incubation behaviour impact individual fitness. Further study is required into the behavioural changes in parenting during chick rearing from the increased perception of parasitism risk.

Anthropogenic activity has enhanced global warming at alarming rates, causing temperatures to increase and heat waves to occur more frequently. The effects of global warming are prominent in aquatic ecosystems, particularly in the Baltic Sea. Temperature increases and fluctuations in the Baltic Sea create a changing environment and this can affect inhabiting species’ behaviors, specifically behaviors during reproduction. Reproductive behavior influences both the number and quality of offspring born into a population therefore making behavior changes during reproduction important to study. The three-spined stickleback (Gasterosteus aculeatus), an ectothermic animal, inhabits the Baltic Sea and is an ideal species to study reproductive behavioral changes. Although previous studies have researched three-spined sticklebacks in changing environments, none had specifically looked into the effects of rising temperatures and temperature fluctuations on male three-spined stickleback reproductive behavior. The three-spined stickleback is of particular interest because it reproduces in shallow waters which tend to be more affected by temperature changes. In this study, I aimed to investigate behavioral responses of stickleback males to higher temperatures and to temperature fluctuations during reproduction, as well as the consequences the responses have for reproductive success and the viability of offspring. In order to see how this species would cope with rising temperatures and heat waves during reproduction, a comparative climate chamber experiment was executed in Southern Finland at Tvärminne Zoological Station. Males were housed in either 19°C or 14°C for two breeding cycles, and for the second breeding cycle eight males switched temperatures to experience a temperature fluctuation. Results show that during reproduction, three-spined sticklebacks respond to higher temperatures with increased courtship activity, increased parental activity, quicker breeding cycles, and more weight lost. Parental care activity in constant high temperature decreases from the first to the second breeding cycle, while parental activity in constant low temperature increases. During temperature fluctuations, males experiencing a rise in temperature increase their parental care activity, while males experiencing a drop in temperature demonstrate the opposite. However, no significant consequences of temperature and temperature changes for reproductive success and the viability of offspring were detected during the two breeding cycles. Overall, the results of this study would indicate that the three-spined stickleback will prove to be a resilient species, and maintain population growth in the face of increased temperatures and temperature fluctuations in the Baltic Sea.

Non-native species can have complex effects on the abundance of native species potentially altering the functioning of ecosystems negatively. Invasive species can outcompete local species competing for resources, ultimately causing the extinction of local species. Inter- and intraspecific competition can be especially vigorous for limited resources. Invasive species have been thought to be a leading cause in native species extinction, and their effects on native species can be especially pronounced during reproductive crucial life-history stages, such as nest-building. Based on previous information about invasive species and their effects on ecosystems, and previous studies conducted related to invasive species, I conducted an experiment at the Tvärminne zoological station in Hanko, southern Finland during May and June of 2021. I conducted a laboratory experiment in which the test species used were the invasive fish species round goby, that has increased its range across the Baltic Sea rapidly, and the native fish species sand goby. The purpose was to see, if there was any effect the invasive species has on the nesting success and motivation of the native species. Methods included five different treatments in aquariums. The results did not differ statistically between different treatments, length was close to statistical significance. However, these results do not demonstrate, that the round goby has no effect on the nest building motivation of sand gobies. Some factors of the experimental setup might have been faulty, and future studies with a larger sample are needed to examine the effects of competition on native species’ abundance.

Trace element analysis is a useful tool for the study of migration and migratory connectivity in birds. Trace elements are present in the environment and, through the food chain, can be incorporated into tissues such as growing feathers. Since the concentrations of elements remain stable after the feather has stopped growing, and trace element abundances can vary at very small geographical scales, the concentration of trace elements in feathers can provide information on the location where a feather was moulted. Trace element analysis is still rarely used and there are important gaps in our understanding of how trace elements can vary at different organizational levels such as within a feather, between individuals or even between species. It is also not clear if large-scale geographical patterns can be detected by the method, as trace element concentrations can vary a lot even at small scales, which could make it impossible to see larger-scale patterns. To address that, my objectives were (1) analysing the variability of trace element concentrations within feathers, between individuals and between species and (2) determining whether trace element levels differed in feathers grown in Africa compared to feathers grown in Europe. This would shed insight on the suitability of trace element analysis for the study of migration and migratory connectivity. I analysed the concentration of 18 trace elements in the rachis of feathers from willow warblers (Phylloscopus trochilus) and barn swallows (Hirundo rustica) collected in Finland. I plucked three belly feathers from willow warblers collected in spring, whose feathers had grown in Africa. These feathers were used to analyse variability of trace element concentrations within feathers and between individuals. They were also compared to feathers plucked from barn swallows collected in spring (two feathers per bird) to analyse variability between the feathers of two species that winter in the same region. Finally, African-grown feathers of willow warblers were compared to European-grown feathers of willow warblers collected in autumn (two feathers per bird) to look for differences in trace element concentrations in feathers grown on two different continents. Trace element concentrations were analysed using Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry (LA-ICP-MS), which allowed to measure concentration at hundreds to thousands of points along the feather rachis. The concentration of each of the 18 elements was used as the response variable in linear mixed models (LMM). To model variation in concentration within the feather I used location along the feather rachis as the explanatory variable and explored how well it predicted concentration of each element. To compare variation between feathers and individuals I fit models including and excluding the feather and individual that each measurement belonged to as random effects and compared them using AIC. To compare between willow warbler and barn swallow feathers grown in Africa I included species identity as the explanatory variable and looked at how the concentration of the 18 elements differed between them. Finally, I followed the same approach to compare willow warbler feathers moulted in Africa and in Europe. For most elements there was little variation along the feather rachis, with concentration remaining stable from feather base to tip. Zn and S showed an increase in concentration starting at the feather base until the central part of the feather and then remained constant toward the tip. Feathers belonging to the same individual showed mostly similar trace element concentrations, although there were exceptions and differences between feathers of different willow warbler individuals were also little. 10 out of 18 elements showed significant differences in feathers of willow warblers and barn swallows grown in Africa. Eight of those elements were more abundant in willow warbler feathers, while only two were more abundant in barn swallow feathers.12 out of 18 elements showed significant differences between their level in African-grown feathers and European-grown feathers. Of those, 10 elements showed higher levels in African-grown feathers, while only two were higher in European-grown feathers. My results suggest that trace elements can show variation at different organizational levels. Variability within feathers was important in at least two elements, which could be caused by physiological processes. This means that when designing sample collection for trace element analysis, unless we know that an element does not vary along a feather, it is important to consider which part of feathers we are sampling. Variability between feathers and individuals was lower than within feather variability, but still significant. Future studies should account for possible within and between individual differences in their design. Differences between barn swallows and willow warblers were large, which was expected based on the literature. It is still unknown what drives these differences between species: some explanations suggested have been physiological and dietary differences or differences in their habitats. I also found clear differences between feathers of willow warblers grown in Europe and Africa. While the exact cause is still not known, this means that at least in willow warbler feathers it is possible to study large scale geographical patterns by trace element analysis. LA-ICP-MS has potential to be a powerful tool to study migration and migratory connectivity in birds. It allows to detect variation in trace elements at continental scales while also allowing to control for different levels of variability in the study design. I encourage researchers to adopt its use in their research.

Lignin is a key macromolecule in many land plants and plays a role in structural support, water conduction, and defence (Vanholme et al., 2010). In most vascular plants, lignin makes up a significant portion of the total plant biomass, about 20-30% (Robinson, 1990). This is important to consider for a variety of reasons, including the large energetic and monetary cost that the forestry industry incurs when removing lignin from tree biomass during processing. Despite its cost to paper and pulp mills, lignin has large potential in the pharmaceutical, construction, and packaging fields, among others (Albuquerque et al., 2021). With proper bioengineering, lignin could even replace fossil fuels as a feedstock in bioplastics production. However, current research and knowledge of lignification, the process wherein lignin deposition occurs in the plant, is lacking when it comes to our ability to produce commercially viable plants with manipulated lignin properties on a large scale. These gaps in knowledge are why it is important to study species with unusual lignin formation, such as the small North American shrub Dirca palustris, commonly known as eastern leatherwood. Such efforts will enable comparative analyses that will improve our understanding of lignification. Previous work on leatherwood has found that the space between adjacent cell walls, known as the middle lamella, is deficient in lignin even after cell wall lignification has concluded, despite the middle lamellae in most other vascular plant species being highly enriched in lignin (Mottiar et al., 2020). This thesis expands upon that finding by determining through histochemical staining, autofluorescence in confocal microscopy, and transmission electron microscopy, that leatherwood is almost completely devoid of lignin in the middle lamella. Histochemical staining and laser excitation were also used to investigate lignin deficiencies in other leatherwood tissues: root, leaf petiole, and peduncle, the small stem that supports flowers and developing fruit. To provide some context for the lignin patterns in leatherwood, both leatherwood and a distant relative, Daphne mezereum, commonly known as daphne, were studied in this work. The results indicate that lignin deficiencies in the middle lamella of fibres may be unique to the Dirca genus as they do not occur in daphne and, therefore, are not necessarily present throughout the entire Thymelaeaceae family. Research was also done with another important macromolecule, pectin, to assess if leatherwood might also have a unique distribution of pectin. Immunostaining revealed that pectin in leatherwood is found in the middle lamella, the same area where lignin is deficient. This new information highlights the need for more research, especially molecular studies, regarding the spatiotemporal relationship between pectin and lignin biosynthesis. Further work is needed to elucidate the underlying genetic factors for leatherwood’s unique lignin patterning, and potentially unveil pectin’s role in the initiation of lignification.

Beta diversity (total dissimilarity) can be partitioned into two components: dissimilarity attributed to turnover and nestedness-resultant dissimilarity. Turnover refers to the variation in species identities among sites and implies the replacement of some species by others. In contrast, nestedness occurs when species-poor sites have a subset of the biota present in species-richer sites. Although disentangling the relative contribution of these two antithetic components from beta diversity can characterize species assemblages, the dissimilarity indices do not provide information on the processes generating the patterns. Conversely, Hierarchical Modelling of Species Communities (HMSC), which unifies many of the recent advantages of Joint Species Distribution Models, has proved to be the one of the best performing frameworks for unravelling the underlying mechanisms structuring ecological communities. The aim of this research is to explore the relationship between the outputs of the HMSC model and the dissimilarity indices in different communities with a wide range of parameterizations. As the observed patterns measured by the beta-diversity indices result from the underlying processes which HMSC attempts to capture, I hypothesized that both frameworks are at least partially linked to each other. To achieve this aim, I simulated the community data by following the structure of the HMSC model. For simplicity, only one environmental covariate was considered, which was scaled to 0 mean. The intercept of the HMSC model accounted for the baseline occurrence probability of the species, while the slope modeled the species responses to the environmental covariate. The HMSC-intercept and the HMSC-slope, which represent the species multivariate niches, were summarized in terms of center and spread. Simultaneously, the beta diversity indices (total, turnover and nestedness dissimilarity) were calculated from the community data. Finally, the outputs of both frameworks were related in terms of linear modelling and variation partitioning. As hypothesized, the results of this study suggest that outputs of the HMSC model are able to explain most of the variation in the beta-diversity indices, indicating that both frameworks are strongly related. By plotting the species niches (intercept and slope coefficients of the HMSC model) it is possible to determine the main axes of niche variation producing the nestedness and turnover patterns. While nestedness is generated by a shared response of the species to the environmental covariate(s), turnover is produced by variation in the species responses. Finally, the total dissimilarity index is driven by species rarity. In conclusion, the most comprehensive evaluation of the structure of ecological communities and the processes determining the diversity patterns can be achieved by combining the outputs of beta-diversity indices and the HMSC model.

Tutkielmassani kartoitan Ahvenanmaan hoikkatytönkorentopopulaation (Ischnura elegans) Wolbachia infektioita. Lisäksi pyrin selvittämään, löytyykö samaa infektiota korentoja loisivilta vesipunkeilta (Hydrachnidia). Wolbachia on niveljalkaisilla yleisesti esiintyvä endosymbioottinen bakteeri. Bakteerin yleinen esiintyminen johtuu sen kyvystä manipuloida isäntänsä kelpoisuutta, jolloin infektoidut naaraat lisääntyvät tehokkaammin. Bakteeri leviää tyypillisesti maternaalisesti iturataa pitkin, mutta voi levitä myös lajilta toiselle horisontaalisesti. Aikaisempien tutkimusten perusteella Manner-Suomen ja Ruotsin hoikkatytönkorentopopulaatioilla esiintyy yleisesti Wolbachia infektioita, toisin kuin Ahvenanmaalla, josta bakteeria ei löydetty lainkaan. Otanta Ahvenanmaalta oli kuitenkin pieni, eikä se siten välttämättä edusta populaation varsinaista infektiostatusta. Lisäksi korentoja loisivien vesipunkkien mahdollisia Wolbachia infektioita tai niiden potentiaalista roolia bakteerin levittämisessä on tutkittu aikaisemmin hyvin vähän. Tutkielmassani analysoin hoikkatytönkorentoja ja niiden punkkeja, jotka on kerätty eri puolilta Ahvenanmaata kesäkuukausien aikana vuosina 2021, 2022 ja 2023. Näytteiden Wolbachia infektiostatuksen selvittämiseksi käytin PCR-tekniikkaa, monistaen yhden mitokondriaalisen lokuksen (COI) ja kolme Wolbachia lokusta (fbpA, wsp ja ftsz). Sekvenssien analysointiin käytin MEGA v.11 ohjelmaa. Laajemman otannan perusteella alle puolella Ahvenanmaan hoikkatytönkorennoista on Wolbachia infektio (41.51 %). Populaatiossa esiintyy ainakin kolmea eri Wolbachia kantaa, joista yksi vastaa Ruotsissa ja toinen Manner-Suomessa esiintyvää bakteerikantaa. Lisää tutkimusta tarvitaan selvittämään, miksi bakteeri ei ole yhtä yleinen Ahvenanmaalla kuin naapuripopulaatioissa, ja millaisia vaikutuksia bakteerilla on hoikkatytönkorennon ekologiaan ja evoluutioon. Noin puolen millimetrin pituisten vesipunkkien infektiostatus jäi epäselväksi lähinnä DNA:n eristämiseen ja monistamiseen liittyvien haasteiden vuoksi.