Aleksandra Cvetkoska

Dr. Aleksandra Cvetkoska

Postdoc

Bezoekadres

Droevendaalsesteeg 10
6708 PB Wageningen

+31 (0) 317 47 34 00

The Netherlands

Netwerk

Over

I am an expert in paleoecology and paleolimnology, specifically interested in understanding how species and communities respond to environmental drivers.

Biografie

I am an integrative biologist, with a background in paleoecology, and paleolimnology and use diatoms (single-celled siliceous algae) as model taxon for my research. Specifically, I am interested in how species and communities responded to the climatic oscillations during the Quaternary. By applying a combination of diatom and geochemistry data from sediment records I reconstruct the ecology of lakes over geological time. 

Earth's biodiversity faces major losses caused by global change, including climate warming and eutrophication. I am interested in understanding the species ability to adapt to changing environments in order to survive and persist. To disentangle the processes facilitating species adaptation, I am developing an integrative approach between two disciplines, experimental evolution and evolutionary paleoecology. A 1.36 Ma old fossil record from Europe's oldest and most biodiverse lake, Lake Ohrid (North Macedonia) provided a unique opportunity to study species phenotypic diversity and evolutionary patterns over multiple glacial-interglacial cycles. In addition, I use experimental studies with diatoms, to understand their short-term response to different temperatures and phosphorus loads. The combination of these disciplines will provide a comprehensive understanding of the evolutionary potential of the aquatic primary producers towards global change on the genetic, physiological, and morphological level of organization. 

CV

Employment

  • 2019–Present
    Postdoc
  • 2017–2018
    Postdoctoral researcher, Justus Liebig University, Giessen, Germany
  • 2014–2017
    Postdoctoral researcher, Palaeoecology, Department of Physical Geography, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands

Education

  • 2011–2014
    PhD in Biological sciences, University SS. Cyril and Methodius, North Macedonia
  • 2009–2011
    MSc in Biology/Ecology, University SS. Cyril and Methodius, North Macedonia

Grants

  • 2017
    Postdoctoral Stipend, Justus Liebig University Giessen, Giessen, Germany
    Budget: €12,000
  • 2010
    UNESCO/Japan Young Researchers' Fellowships Programme (UNESCO/Keizo Obuchi Research Fellowships Programme)
    Budget: €10,000

Invited talks and keynote addresses on symposia and conferences

  • 2018
    Society of Wetland Scientists European Chapter Meeting
  • 2016
    10th Central European Diatom Meeting
  • 2015
    Nederlands-Vlaamse Kring van Diatomisten. NVKD study days
  • 2015
    IODP-NL Symposium: Illuminating the Earth by scientific drilling

Publicaties

Belangrijkste publicaties

  • Global Ecology and Biogeography
    2022

    Environmental filtering drives assembly of diatom communities over evolutionary time-scales

    Jovanovska, E., Hauffe, T., Stelbrink, B., Cvetkoska, A., Levkov, Z., et al.
    Abstract Aim Ecological communities are structured through the interplay of deterministic assembly processes such as competition and environmental filtering. Whereas the drivers of spatial community structure are frequently studied in extant communities, little is known about the relative importance of assembly processes in response to environmental factors over evolutionary time-scales. Here, we use an integrative framework to unravel community assembly processes since the inception of a long-lived lake ecosystem. Location Lake Ohrid. Time period From lake formation 1.36 million years ago to the present. Major taxa studied Planktonic diatoms. Methods We constructed a dated phylogeny of extant and extinct diatoms and collected trait data for 380 fossil communities to quantify phylogenetic community structure and functional richness and to determine the relative importance of deterministic assembly processes over time. We then used regression analysis to correlate the phylogenetic community structure with palaeoenvironmental and intrinsic biological predictors and to identify primary drivers of assembly processes. Results Our results suggest a dense packing of niche space with higher species richness and co-occurrence of closely related species. There are only two short episodes in the very recent past dominated by distantly related taxa. We found distinct changes in phylogenetic community structure upon speciation or extinction events and an increase in mean community relatedness over time. Main conclusions Our finding of closely related co-occurring species implies environmental filtering as the primary assembly mechanism, with a minor but increasingly important role of competition towards the present, driven by evolutionary dynamics. Such an increase in the relative contribution of competition to the assembly of communities in relation to the aging of an insular ecosystem, together with a denser packing of morphospace in the early phase of system ontogeny is compatible with ecological predictions according to the theory of island biogeography.
  • Quaternary Science Reviews
    2021

    Drivers of phytoplankton community structure change with ecosystem ontogeny during the Quaternary

    Cvetkoska, A., Jovanovska, E., Hauffe, T., Donders, T. H., Levkov, Z., Van de Waal, D. B., Reed, J. M., et al.
    Freshwater species are particularly sensitive to climate fluctuations, but little is known of their response to the large-scale environmental change that took place during the Quaternary. This is partly due to the scarcity of continuously preserved freshwater sedimentary records with orbital chronology. We use a 1.363 Ma high-resolution fossil record of planktonic diatoms from ancient Lake Ohrid to evaluate the role of global and regional versus local-scale environmental change in driving temporal community dynamics. By using a Bayesian joint species distribution model, we found that communities were mostly driven by the local-scale environment. Its effects decreased over time, becoming less important than global and regional environment at the onset of the penultimate glacial, 0.183 Ma. Global and regional control over the environment became important with successive deepening of the lake at around 1.0 Ma, and its influence remained persistent until the present. Our high-resolution data demonstrate the critical role of lake depth and its thermal dynamics in determining phytoplankton response to environmental change by influencing lake mixing, nutrient and light availability. With this study we demonstrate the relative impact of various environmental factors and their scale-dependant effect on the phytoplankton communities during the Quaternary, emphasizing the importance of not only considering climate fluctuations in driving their structure and temporal dynamics but also the local environment.
  • Science Advances
    2020

    Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem

    Wilke, T., Hauffe, T., Jovanovska, E., Cvetkoska, A., Donders, T. H., Ekschmitt, K., Francke, A., Lacey, J., Levkov, Z., et al.
    The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems.
  • Nature
    2019

    Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years

    Wagner, B., Vogel, H., Francke, A., Friedrich, T., Donders, T., Lacey, J.H., Leng, M. J., ...Cvetkoska, A., et al.
    Mediterranean climates are characterized by strong seasonal contrasts between dry summers and wet winters. Changes in winter rainfall are critical for regional socioeconomic development, but are difficult to simulate accurately1 and reconstruct on Quaternary timescales. This is partly because regional hydroclimate records that cover multiple glacial–interglacial cycles2,3 with different orbital geometries, global ice volume and atmospheric greenhouse gas concentrations are scarce. Moreover, the underlying mechanisms of change and their persistence remain unexplored. Here we show that, over the past 1.36 million years, wet winters in the northcentral Mediterranean tend to occur with high contrasts in local, seasonal insolation and a vigorous African summer monsoon. Our proxy time series from Lake Ohrid on the Balkan Peninsula, together with a 784,000-year transient climate model hindcast, suggest that increased sea surface temperatures amplify local cyclone development and refuel North Atlantic low-pressure systems that enter the Mediterranean during phases of low continental ice volume and high concentrations of atmospheric greenhouse gases. A comparison with modern reanalysis data shows that current drivers of the amount of rainfall in the Mediterranean share some similarities to those that drive the reconstructed increases in precipitation. Our data cover multiple insolation maxima and are therefore an important benchmark for testing climate model performance.
  • Biogeosciences
    2016

    Ecosystem regimes and responses in a coupled ancient lake system from MIS 5b to present: the diatom record of lakes Ohrid and Pr

    Cvetkoska, A., Jovanovska, E., Francke, A., Tofilovska, S., Vogel, H., Levkov, Z., Donders, T. H., Wagner, B., Wagner-Cremer, F.
    We reconstruct the aquatic ecosystem interactions since the last interglacial period in the oldest, most diverse, hydrologically connected European lake system, by using palaeolimnological diatom and selected geochemistry data from Lake Ohrid “DEEP site” core and equivalent data from Lake Prespa core, Co1215. Driven by climate forcing, the lakes experienced two adaptive cycles during the last 92 ka: "interglacial and interstadial" and "glacial" cycle. The short-term ecosystems reorganizations, e.g. regime shifts within these cycles substantially differ between the lakes, as evident from the inferred amplitudes of variation. The deeper Lake Ohrid shifted between ultra oligo- and oligotrophic regimes in contrast to the much shallower Lake Prespa, which shifted from a deeper, (oligo-) mesotrophic to a shallower, eutrophic lake and vice versa. Due to the high level of ecosystem stability (e.g. trophic state, lake level), Lake Ohrid appears relatively resistant to external forcing, such as climate and environmental change. Recovering in a relatively short time from major climate change, Lake Prespa is a resilient ecosystem. At the DEEP site, the decoupling between the lakes' response to climate change is marked in the prolonged and gradual changes during the MIS 5/4 and 2/1 transitions. These response differences and the lakes' different physical and chemical properties may limit the influence of Lake Prespa on Lake Ohrid. Regime shifts of Lake Ohrid due to potential hydrological change in Lake Prespa are not evident in the data presented here. Moreover, a complete collapse of the ecosystems functionality and loss of their diatom communities did not happen in either lake for the period presented in the study.

Peer-reviewed publicaties

  • Quaternary International
    2022

    Diatom community responses to environmental change in Lake Ohrid (Balkan Peninsula) during the mid-Pleistocene Transition

    Dušica Zaova, Aleksandra Cvetkoska, Bernd Wagner, Alexander Francke, Hendrik Vogel, Zlatko Levkov, Elena Jovanovska

    The Quaternary is characterized by a series of glacial-interglacial cycles and a shift in the Earth's climate state known as the mid-Pleistocene Transition (MPT, ca. 1200 ka to 720 ka). The progressive increase in glacial cycle length from approximately 41 ka to on average 100 ka affected marine and terrestrial life, but how it affected freshwater communities is far less known. Here, diatom and paleoenvironmental data between 1050 ka and 815 ka from a sediment succession of ancient Lake Ohrid are used to understand how the freshwater communities responded to environmental changes during key-periods of glacial intensification associated with the MPT. Based on stratigraphically constrained incremental sum of squares cluster (CONISS), a distinct diatom community turnover in Lake Ohrid was identified during the study period. The first community existed between 1050 and 955 ka MIS (Marine Isotope Stages) 30–25 and was mostly influenced by environmental parameters related to nutrient supply, mixing processes and primary productivity in the lake. The second community existed between 955 and 815 ka (MIS 25–21) and was largely driven by ontogenetic processes related to the ongoing deepening of the lake, changes in bottom water redox conditions and changes in mixing processes in the lake. The increased severity and duration of cold, glacial stages during the MPT shows only a weak impact on the diatom community in Lake Ohrid. Shifts in species phenotypes, abundance and composition are found in both communities, likely as adaptation in response to the changing environmental conditions. This study shows that the diatom communities were only weakly affected by the progressive intensification of the glacial intensity during the MPT, emphasizing the role of local environmental changes in regulating freshwater communities.

    https://doi.org/10.1016/j.quaint.2022.03.002
  • Global Ecology and Biogeography
    2022

    Environmental filtering drives assembly of diatom communities over evolutionary time-scales

    Elena Jovanovska, Torsten Hauffe, Björn Stelbrink, Aleksandra Cvetkoska, Zlatko Levkov, Bernd Wagner, Jack H. Lacey, Nadja Ognjanova-Rumenova, Paul B. Hamilton, Karen M. Brandenburg, Christian Albrecht, Thomas Wilke

    Aim: Ecological communities are structured through the interplay of deterministic assembly processes such as competition and environmental filtering. Whereas the drivers of spatial community structure are frequently studied in extant communities, little is known about the relative importance of assembly processes in response to environmental factors over evolutionary time-scales. Here, we use an integrative framework to unravel community assembly processes since the inception of a long-lived lake ecosystem.

    Location: Lake Ohrid.

    Time period: From lake formation 1.36 million years ago to the present.

    Major taxa studied: Planktonic diatoms.

    Methods: We constructed a dated phylogeny of extant and extinct diatoms and collected trait data for 380 fossil communities to quantify phylogenetic community structure and functional richness and to determine the relative importance of deterministic assembly processes over time. We then used regression analysis to correlate the phylogenetic community structure with palaeoenvironmental and intrinsic biological predictors and to identify primary drivers of assembly processes.

    Results: Our results suggest a dense packing of niche space with higher species richness and co-occurrence of closely related species. There are only two short episodes in the very recent past dominated by distantly related taxa. We found distinct changes in phylogenetic community structure upon speciation or extinction events and an increase in mean community relatedness over time.

    Main conclusions: Our finding of closely related co-occurring species implies environmental filtering as the primary assembly mechanism, with a minor but increasingly important role of competition towards the present, driven by evolutionary dynamics. Such an increase in the relative contribution of competition to the assembly of communities in relation to the aging of an insular ecosystem, together with a denser packing of morphospace in the early phase of system ontogeny is compatible with ecological predictions according to the theory of island biogeography.

    https://doi.org/10.1111/geb.13471
  • Quaternary Science Reviews
    2021

    Drivers of phytoplankton community structure change with ecosystem ontogeny during the Quaternary

    Aleksandra Cvetkoska, Elena Jovanovska, Torsten Hauffe, Timme H. Donders, Zlatko Levkov, Dedmer Van de Waal, Jane M. Reed, Alexander Francke, Hendrik Vogel, Thomas Wilke, Bernd Wagner, Friederike Wagner-Cremer
    Freshwater species are particularly sensitive to climate fluctuations, but little is known of their response to the large-scale environmental change that took place during the Quaternary. This is partly due to the scarcity of continuously preserved freshwater sedimentary records with orbital chronology. We use a 1.363 Ma high-resolution fossil record of planktonic diatoms from ancient Lake Ohrid to evaluate the role of global and regional versus local-scale environmental change in driving temporal community dynamics. By using a Bayesian joint species distribution model, we found that communities were mostly driven by the local-scale environment. Its effects decreased over time, becoming less important than global and regional environment at the onset of the penultimate glacial, 0.183 Ma. Global and regional control over the environment became important with successive deepening of the lake at around 1.0 Ma, and its influence remained persistent until the present. Our high-resolution data demonstrate the critical role of lake depth and its thermal dynamics in determining phytoplankton response to environmental change by influencing lake mixing, nutrient and light availability. With this study we demonstrate the relative impact of various environmental factors and their scale-dependant effect on the phytoplankton communities during the Quaternary, emphasizing the importance of not only considering climate fluctuations in driving their structure and temporal dynamics but also the local environment.
    https://doi.org/10.1016/j.quascirev.2021.107046
  • Science advances
    30-09-2020

    Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem

    Thomas Wilke, Torsten Hauffe, Elena Jovanovska, Aleksandra Cvetkoska, Timme Donders, Klemens Ekschmitt, Alexander Francke, Jack H. Lacey, Zlatko Levkov, Charles R. Marshall, Thomas A. Neubauer, Daniele Silvestro, Björn Stelbrink, Hendrik Vogel, Christian Albrecht, Jens Holtvoeth, Sebastian Krastel, Niklas Leicher, Melanie J. Leng, Katja Lindhorst, Alessia Masi, Nadja Ognjanova-Rumenova, Konstantinos Panagiotopoulos, Jane M. Reed, Laura Sadori, Slavica Tofilovska, Bert Van Bocxlaer, Friederike Wagner-Cremer, Frank P. Wesselingh, Volkmar Wolters, Giovanni Zanchetta, Xiaosen Zhang, Bernd Wagner
    The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems.
    https://doi.org/10.1126/sciadv.abb2943
  • European Journal of Taxonomy
    2020

    Tertiarius minutulus sp. nov. (Stephanodiscaceae, Bacillariophyta) – a new fossil diatom species from Lake Ohrid

    Dušica Zaova, Aleksandra Cvetkoska, Danijela Mitic-Kopanja, Elena Jovanovska, Nadja Ognjanova-Rumenova, Zlatko Levkov
    A new fossil diatom species, Tertiarius minutulus sp. nov., is described from a sediment sequence DEEP-5045-1 of Lake Ohrid. The species is characterized by small valves (3.0–8.0 µm) with a round shape, a marginal area with radially arranged costae and a central uneven area with scattered areolae. Externally, the alveoli are occluded by cribra perforated by irregularly arranged pores. Internally, the alveoli are simple and areolae are occluded with domed cribra. The marginal fultoportulae are situated on costae close to the valve margin, located on every 5th or 7th thick internal costa. One to three fultoportulae are present on the valve face, each surrounded by two to three satellite pores. One rimoportula is present, positioned on a costa at the valve face / mantle junction. The species is compared with morphologically similar taxa and a detailed differential diagnosis is provided. Tertiarius minutulus sp. nov. is known only as a fossil taxon from Lake Ohrid, with a first occurrence during the early stages of lake basin development.
    https://doi.org/10.5852/ejt.2020.670
  • Quaternary Science Reviews
    2020

    Insights into the evolution of the young Lake Ohrid ecosystem and vegetation succession from a southern European refugium during the Early Pleistocene

    Konstantinos Panagiotopoulos, Jens Holtvoeth, Katerina Kouli, Elena Marinova, Alexander Francke, Aleksandra Cvetkoska, Elena Jovanovska, Jack H. Lacey, Emma T. Lyons, Connie Buckel, Adele Bertini, Timme Donders, Janna Just, Niklas Leicher, Melanie J. Leng, Martin Melles, Richard D. Pancost, Laura Sadori, Paul Tauber, Hendrik Vogel, Bernd Wagner, Thomas Wilke
    Mediterranean mid-altitude sites are critical for the survival of plant species allowing for elevationalvegetation shifts in response to high-amplitude climate variability. Pollen records from the southernBalkans have underlined the importance of the region in preserving plant diversity over at least the lasthalf a million years. So far, there are no records of vegetation and climate dynamics from Balkan refugiawith an Early Pleistocene age. Here we present a unique palynological archive from such a refugium, theLake Ohrid basin, recording continuouslyfloristic diversity and vegetation succession under obliquity-paced climate oscillations. Palynological data are complemented by biomarker, diatom, carbonateisotope and sedimentological data to identify the mechanisms controlling shifts in the aquatic andterrestrial ecosystems within the lake and its catchment. The study interval encompasses four completeglacial-interglacial cycles (1365e1165 ka; MIS 43e35). Within thefirst 100 kyr of lake ontogeny, lake sizeand depth increase before the lake system enters a new equilibrium state as observed in a distinct shift inbiotic communities and sediment composition. Several relict tree genera such asCedrus,Tsuga,Carya,andPterocaryaplayed an important role in ecological succession cycles, while total relict abundanceaccounts for up to half of the total arboreal vegetation. The most prominent biome during interglacials iscool mixed evergreen needleleaf and deciduous broadleaf forests, while cool evergreen needleleaf forestsdominate within glacials. A rather forested landscape with a remarkable plant diversity provide uniqueinsights into Early Pleistocene ecosystem resilience and vegetation dynamics.
    https://doi.org/10.1016/j.quascirev.2019.106044

Projecten & samenwerkingen

Projecten

Outreach

Categories