Communities are defined as the ensemble of populations that interact with
each other and with the environment in a specific time and location.
Community ecology studies how communities assemble, what are the
patterns of diversity, abundance, and composition of species, and the
processes driving these patterns. It includes four basic mechanisms for the
assembly of communities: dispersal, drift, selection, and speciation, with
each mechanism influencing how the communities change in a different
way. Dispersal, the movement of species from one geographical location to
another, plays a major role in the recolonization of barren environments and
the introduction of new species to established environments. Drift (i.e.,
random birth and death events within a community) could, theoretically, be
negligible in bacterial communities where the high population densities are
expected to buffer its effect. Conversely, horizontal gene transfer can be a
strong selective force, as horizontally transferred genetic material is a
source of functional traits that may provide selective advantages to the
recipient cells, especially in environments where strong selection pressure
occurs.
In my Ph.D. thesis, I aim to examine these three contrasting mechanisms
in controlled, simplified bacterial communities that are designed and studied
through a synthetic ecology approach. I found that even at low dispersal
rates, the species abundance of planktonic bacterial communities can be
homogenized by migration. This homogenization can occur even when
there are strong variable selection forces interacting in each environment.
I also found strong evidence on the importance of stochasticity in
communities. Drift can decrease the community similarity by up to 6.3%,
and increases the probabilities that species become extinct, especially in
the case of rare taxa.
In contrast, I found that naturally competent bacteria are favored to uptake
more DNA in communities that are highly productive and phylogenetically
diverse. This pattern is explained by a potential higher availability of naked
DNA for naturally competent bacteria, presumably because there are more
cells and the predation systems are more effective. Altogether, our findings
support the theory on the importance of stochastic forces and their
interaction with deterministic forces on the shaping of microbial community
assembly.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/659509 |
| Date | 10 1900 |
| Creators | Valenzuela-Cuevas, Adriana |
| Contributors | Daffonchio, Daniele, Biological and Environmental Science and Engineering (BESE) Division, Hong, Pei-Ying, Moran, Xose Anxelu G., Marzorati, Massimo |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2024-04-30, At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2024-04-30. |
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