Supervisor: dr hab. Łukasz Michalczyk, prof. UJ (l.michalczyk@uj.edu.pl)

Institute of Zoology and Biomedical Research

Background information:

In recent years, research on tardigrades, microinvertebrates ubiquitous across the globe, has significantly broadened our understanding of their diversity, biogeography, evolution, and their iconic cryptobiotic abilities. However, not much is known about the causes behind the differences in the evolutionary success and dispersal abilities within the phylum. Some tardigrade clades are widespread and rich in species whereas their relatives are rare and have restricted geographic ranges. Such a pattern can be observed in the eutardigrade family Macrobiotidae, making it a great model for studying factors determining variation in species richness and geographic ranges. However, little is known about the evolution of macrobiotoid morphological traits, types of reproduction, and variation in their anhydrobiotic abilities, which prevents addressing the question posed in this project.

The main question to be addressed in the project:

The project aims to identify determinants of evolutionary success of closely related clades, using macrobiotoid tardigrades as a model. The results of this project will not only allow for understanding the past, but may also allow for predicting what the future evolution of this animal group may look like, under ongoing climate change.

Information on the methods/description of work:

Tardigrades will be isolated from samples collected throughout the world and analysed under the integrative taxonomy framework to determine their morphological variability and establish their detailed phylogenetic relationships. Moreover, physiological traits that are hypothesised to play an important role in survival and dispersal will be experimentally analysed. Specifically, individuals obtained via isogenic cultures will be tested under controlled laboratory conditions for anhydrobiotic survival under varying temperature and humidity, as well as for resistance of active animals to variations in temperature, pH, and restricted food availability. Both survival and reproductive success after exposure to harsh environmental conditions will be evaluated. In parallel, reproductive mode will be identified via gonad and lifecycle observations. We will then map morphological and physiological variability onto the phylogeny. We predict that increased survivability and resistance to unfavourable environmental conditions, as well as parthenogenesis and certain morphotypes, should correlate with geographic range size and species richness of the analysed tardigrade clades.

Additional information (e.g Special requirements from the student):

The applicant should have at least basic knowledge of tardigrade taxonomy and a strong interest in evolutionary biology. Experience working with microinvertebrates is highly advantageous.

References:

[1] Kremer A. & Hipp A.L. (2020) Oaks: an evolutionary succes story. New Phytologist, 226: 987–101. [https://doi.org/10.1111/nph.16274]

[2] Neves R.C. et al. (2020) New insights into the limited thermotolerance of anhydrobiotic tardigrades. Communicative & Integrative Biology, 13(1): 140–146. [https://doi.org/10.1080/19420889.2020.1812865]

[3] Stec D. et al. (2021) New multilocus phylogeny reorganises the family Macrobiotidae (Eutardigrada) and unveils complex morphological evolution of the Macrobiotus hufelandi group. Molecular Phylogenetics and Evolution, 160: 106987. [https://doi.org/10.1016/j.ympev.2020.106987]