Date of Award

2019-01-01

Degree Name

Master of Science

Department

Geological Sciences

Advisor(s)

Elizabeth J. Walsh

Abstract

Species living in temporary wetlands can be threatened due to the instability and fluctuation of rising temperatures and evaporation caused by global climate change. In addition, regions characterized by dry climates, where most temporary wetlands exist, are expected to have a stronger response to climate change than other ecosystems. While most organisms are not able to respond to rapid changes in their environments, others like freshwater invertebrates have shown great resiliency to short- and long-term ecological disturbances. Rotifers for example, inhabit temporary waters that remain desiccated for indefinite periods of time making assessment of rotifer biodiversity challenging. Fortunately, many microinvertebrates have the ability to produce resting stages that persist in surface sediments when conditions become unfavorable. Their ability to persist through resting stages is important since the structure of these communities contribute to healthy and sustainable ecosystems. Here, active rotifer communities were compared with egg banks found in surface sediments from 12 temporary desert wetlands. Dormant communities were analyzed through rehydration experiments and amplicon sequencing. It was hypothesized that more permanent ponds would have higher microinvertebrate species richness than those that are more ephemeral due to habitat stability. Rehydration of sediments from 12 sites resulted in 41 rotifer species emerging from diapause, with richness ranging from 1-16. Unique taxa not present in active species lists were found in 8 out of the 12 sites. Species richness was highest in larger, Australian sites with lowest richness occurring in small rock pools from the United States. For a subset of the sites, hatching success was compared from sediments stored up to 21 years of age in order to assess the viability of rotifer resting eggs to hatch after being stored for long periods. As expected, recovery of rotifer species from older sediments was less when compared to the recovery rates of newer sediments. One-yr old sediment collected from a Texas playa yielded the highest species richness (n=10). Amplicon sequencing of sediments showed that taxonomic diversity varied among pond types and that larger more permanent temporary ponds had higher diversity than those that were more ephemeral. 18S sequencing resulted in 702,328 reads and 34,995 Operational Taxonomic Units (OTUs), of these, 3,610 (0.51%) reads corresponded to 55 OTUs (0.15%) that were identified as rotifers. COI sequencing resulted in 495,643 reads and 10,241 OTUs, of these, 15,687 reads (3.16%) corresponded to 149 OTUs (1.45%) that were identified as rotifers. Principal Coordinates Analysis (PCoA) plots constructed with 18S sequences showed little to no similarities among sites. Interestingly, PCoA plots based on COI sequences clustered sites by pool type. Implementing these approaches into ecological assessments of resting stages can expand our knowledge on their efficiency to fully capture species richness and how a combination of them allows detection of taxa missed by using only one method.

Language

en

Provenance

Received from ProQuest

File Size

116 pages

File Format

application/pdf

Rights Holder

Sergio David Samaniego

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Biology Commons

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