Map of the world

Theory at the service of conservation


About

Tanjona

I am a Malagasy ecologist with a mission to protect our unique biodiversity. Since I am more skilled in Mathematics than identifying plants or animals, I primarily develop mathematical and statistical models to better understand patterns and processes of biodiversity loss.

I obtained a MSc in applied mathematics with Arthur Randrianarivony at the University of Antananarivo. I completed a PhD with Ilkka Hanksi and Otso Ovaskainen at the University of Helsinki. I did a first postdoc with Emma Goldberg at the University of Minnesota working on energy budget models, and second postdoc with Anthony Ives and Monica G. Turner at the University of Wisconsin-Madison on abrupt changes in ecological systems (ACES).


Research

I work at the interface of theoretical ecology and conservation biology. I use mathematical and statistical approaches to assess the role of spatial processes, environmental variability, and species interactions to understand population persistence, community stability, and maintenance of biodiversity. I am not tied to a specific system and my work spans various continents: Asia, Europe, Northern America, and 'Madagascar', and includes topics such as phylogeography, paleoecology, contemporary ecology. Nevertheless, my research are generally motivated by conservation related questions in Madagascar.
extinction threshold as a function of niche breadth

Extinction thresholds, abrupt changes, alternative stable states

I try to understand how and what cause a system to shift to qualitatively a different state, e.g. species extirpation, extinction, or species composition. I strive to build models of intermediate complexity to bridge theoretical and empirical work and provide a mix of theoretical insights and practical applications. Key mechanisms I am interested in are: spatial processes such habitat destruction, change in disturbance regime due to climate change, stochastic processes, niche width, and species interaction.

habitat destruction in Madagascar

Habitat destructions, landscape connectivity, habitat corridors

This topic focuses on understanding population and community dynamics in fragmented landscapes and complements the theme above by adopting a more quantitative approach. The main goals include:

  • Quantifying loss of habitat quality, quantity, and fragmentation especially caused by human
  • Using spatially realistic landscape to assess population and community dynamics with sufficient biological details for parameterization
  • Merging spatial ecology and landscape ecology
  • thermal performance curve

    Thermal performance curve, regeneration niche, traits optimization

    A third interrelated topic is to understand factors that shape species' niche width.

  • Using energy budget and metabolic theory to understand species performance as a function of body size, temperature, and resource availability
  • Understanding the efficiency of various plant regeneration strategies with respect to distrubance regime with a particular focus on stand-replacing fire
  • Modeling the evolution of life-history traits in variable environments and spatially heterogeneous landscapes
  • phylogenetic pattern

    Miscellaneous

    I am broadly interested in method developments or analyses. I am developing phylogenetic comparative methods and a statistical approach to optimize fungal spores counting. I have been analyzing large spatiotemporal data: crop yield in the USA, evolution of malaria in Madagascar, and infuence of political instability on the economy of Madagascar.


    Publications and in prep.

    Ramiadantsoa, T. , M.A. Stegner, J.W. Williams, and A.R. Ives. 2019. The potential role of intrinsic processes in generating abrupt and quasi-synchronous tree declines during the Holocene. Ecology. 100(2): e02579

    Ramiadantsoa, T. , I. Hanski, and O. Ovaskainen. 2018. Responses of Generalist and Specialist Species to Fragmented Landscapes. Theoretical Population Biology. 124:31-40.

    Ratajczak, Z., S.R. Carpenter, A.R. Ives, C.J. Kucharik, T. Ramiadantsoa, M. A. Stegner, J. W. Williams, J. Zhang, and M.G. Turner. 2018. Abrupt Change in Ecological Systems: Inference and Diagnosis. Trends in Ecology & Evolution, Volume 33, Issue 7.

    Ihantamalala, F. A., F.M.J. Rakotoarimanana, T. Ramiadantsoa, J.M. Rakotondramanga, G. Pennober, F. Rakotomanana, S. Cauchemez, C.J.E. Metcalf, V. Herbreteau, and A. Wesolowski. 2018. Spatial and temporal dynamics of malaria in Madagascar. Malaria journal 17, no. 1: 58.

    Ramiadantsoa, T., J. Sirén, and I. Hanski. 2017. Phylogenetic comparative method for geographical radiation. Annales Zoologica Fennica Vol. 54. No. 1–4 (special issue in honor of Ilkka Hanski).

    Ramiadantsoa, T., O. Ovaskainen, J. Rybicki, and I. Hanski. 2015. Large-scale habitat corridors for biodiversity conservation: A forest corridor in Madagascar. PloS ONE 10: e0132126.

    Submitted and in prep.

    Kucharick, C.J., T. Ramiadantsoa, J. Zhang, A.R. Ives. Spatiotemporal trends in crop yields, yield variability, and yield gaps across the USA. In review in Crop science.

    Ramiadantsoa, T., Z. Ratajczak, M.G. Turner. A Goldilocks model for the response of fire-prone forests to changing fire regime: a case study of Yellowstone Nation Park. In prep. for Journal of Ecology.

    Ramiadantsoa, T. and A.R. Ives. Consequences of the structure of environmental variability on population and community stability. In prep. for Ecology Letters.

    Ramiadantsoa, T. and E.E. Goldberg. Exploring the role of body size in shaping thermal performance of insects.

    McCary, M.A., J. Phillips, T. Ramiadantsoa, L.A. Nell, A.R. McCormick, J.C. Botsch. Transient top-down and bottom-up effects on resources pulsed to multiple trophic levels. In prep. for Oikos.

    Perrotti, A.G., M. Traschel, T. Ramiadantsoa, ..., J.W. Williams. Optimal counting methods for coprophilous fungal spore analysis.

    Ramiadantsoa, T. , C.J.E. Metcalf, Selection of extreme life-history traits under hypervariable environments: a theoretical perspective.

    Ramiadantsoa, T., C. Fritsch. Extinction threshold and transient dynamics of orphaned plants.

    Ramiadantsoa, T., E.M. Temba, H. Rakouth, H.J. Rakotoniriana. Evidence of biodiversity loss in Madagascar? A multi-taxa review.

    Rakotoarivelo, O., Ramiadantsoa, T., Economic impacts of political instability in Madagascar.


    Teaching and outreach

    I spent a bit of my time introducing esoteric world of scientific research and the application of mathematics in ecology and conservation to high school students in Madagascar. I also co-organize and teach theory based workshops in Madagascar. The workshop on ecological and epidemiological modeling in Madagascar (E2M2) which is on its fourth year. A new workshop on data manipulation and visualization is now cooking. I am also developing a theoretical ecology class at a level suitable for both ecologists and mathematicians at the University of Antananarivo, Madagascar.

    My other activites include fostering cultural exchanges between Madagascar and other countries. I am a member of two societies: the Finnish-based (Suomi-Madagascar Seura) and the Malagasy-based (Madagascar-Finland). On top of cultural exchanges, we organize fund raising to help underprivileged students in Madagascar. Additionally, I have been organizing Malagasy language course for linguists students at the University of Helsinki.


    Contact & CV

    My CV
    Email: ramiadantsoa-AT-wisc.edu
    Twitter: @TRamiadantsoa