The interplay between movement, dispersal and morphology in Tetrahymena ciliates
- Published
- Accepted
- Subject Areas
- Biodiversity, Ecology, Microbiology, Freshwater Biology, Population Biology
- Keywords
- experimental, microcosm, movement ecology, Tetrahymena thermophila, condition-dependence
- Copyright
- © 2018 Pennekamp et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2018. The interplay between movement, dispersal and morphology in Tetrahymena ciliates. PeerJ Preprints 6:e26540v1 https://doi.org/10.7287/peerj.preprints.26540v1
Abstract
Understanding how and why individual movement translates into dispersal between populations is a long-term goal in ecology. Movement is broadly defined as “any change in the spatial location of an individual”, whereas dispersal is more narrowly defined as a movement that may lead to gene flow. Because the former may create the condition for the latter, behavioural decisions that lead to dispersal may be detectable in underlying movement behaviour. In addition, dispersing individuals also have specific sets of morphological and behavioural traits that help them coping with the costs of movement and dispersal, and traits that mitigate costs should be under selection and evolve if they have a genetic basis. Here we experimentally study the relationships between movement behaviour, morphology and dispersal across 44 genotypes of the actively dispersing unicellular, aquatic model organism Tetrahymena thermophila. We used two-patch populations to quantify individual movement trajectories, as well as activity, morphology and dispersal rate. First, we studied variation in movement behaviour among and within genotypes (i.e. between dispersers and residents) and tested whether this variation can be explained by morphology. Then, we address how much the dispersal rate is driven by differences in the underlying movement behaviour. Genotypes expressed different movements in terms of speed and path tortuosity. We also detected marked movement differences between resident and dispersing individuals, mediated by the genotype. Movement variation was partly explained by morphological properties such as cell size and shape, with larger cells consistently showing higher movement speed and lower tortuosity. Genetic differences in activity and diffusion rates were positively related to the observed dispersal and jointly explained 45% of the variation in dispersal rate. Our study shows that a detailed understanding of the interplay between morphology, movement and dispersal may have potential to improve dispersal predictions over broader spatio-temporal scales.
Author Comment
This is a submission to PeerJ for review.
Supplemental Information
A two patch dispersal system made of two 1.5 mL microtubes connected by a silicon pipe, filled with nutritive medium, used to quantify dispersal rate from cells inoculated in the start patch and allowed to move freely during 6 h
An illustration of the raw trajectory data extracted from videos
Different colours show different individual trajectories. The linearity differed among trajectories with some being very linear and others more tortuous (see arrows). Some very short (in time or space) trajectories correspond to non-moving cells.
Relationships between movement metrics (speed and tortuosity) and cell morphology averaged at the genotype level (N=88)
Lines show the fit of the most parsimonious ANCOVA model relating cell morphology to movement metrics, considering variation due to the dispersal status. Larger cells moved faster and less tortuous and the effect was additive.
Relationships between relative changes in movement metrics (speed and tortuosity) and cell morphology (N=132)
Each point is the difference between the disperser and residents across genotypes and replicates. Lines show the fit of the most parsimonious ANCOVA model relating cell morphology to movement metrics. If disperser cells were relatively larger than residents, they moved faster. In contrast, if dispersers were more elongated than residents, they moved slower. Relative changes in size and shape did not influence the relative tortuosity.
Overview of the genotypes used in the experiment
Supplemental information
Details about genotypes used, the experimental system and the trajectory reconstruction.