Date of Award

Summer 2017

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Dr. Rebecca Drenovsky

Abstract

Gypsum endemism in plants (gypsophily) is common on gypsum outcrops worldwide, but little is known about the functional ecology of Chihuahuan Desert gypsophiles. We investigated whether leaf chemistry of gypsophile lineages from the northern Chihuahuan Desert are similar to leaves of related non-endemic (gypsovag) species relative to their soil chemistry. We expected widely-distributed gypsophiles, hypothesized to be older lineages on gypsum, would have distinct leaf chemistry from narrowly-distributed, relatively younger lineages endemic to gypsum and gypsovags, reflecting adaptation to gypsum. We collected leaves from 23 gypsophiles and related non-endemic taxa growing on non-gypsum soils. Soils and leaves were analyzed for Ca, S, Mg, K, N, and P. Leaf gypsum was assessed using Fourier transform infrared spectroscopy. Most widespread gypsophilic lineages that are hypothesized to be relatively old accumulate foliar S, Ca and gypsum, but younger gypsophilic lineages and closely related gypsovags do not. Young, narrowly-distributed gypsophilic lineages have leaf chemical signatures similar to non-endemic congeners and confamilials. Our data suggest multiple adaptive mechanisms support life on gypsum in Chihuahuan Desert gypsophiles. Most widespread gypsophiles are specialized for life on gypsum, likely due to shared abilities to accumulate and assimilate S and Ca in leaves. In contrast, narrowly-distributed gypsophiles may have mechanisms to exclude excess S and Ca from their leaves, preventing toxicity. Future work will investigate the nutrient accumulation and exclusion patterns of other plant organs to determine at what level excess S and Ca uptake is restricted for young-lineage gypsophiles and gypsovags.

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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