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Abstract Detail

Ecological Section

Coburn, Francis S. [1], Stromberg, Juliet [1], Landrum, Leslie R. [1], Makings, Elizabeth [1].

The Enhancement of Regional Floristic Species Richness by Geologic Complexity: Examples from the Upper Verde River, Arizona.

Edaphic factors exert significant influence on plant species distributions, coming second only to climate among abiotic factors. Within a given climate, the plant species diversity of an area can greatly increase due to the presence of differing substrates. This is especially evident when particularly harsh or infertile soils are present. Indeed, some of the world’s hotspots for diversity owe their richness to the presence of high numbers of endemics of infertile soils. The region of the Upper Verde River in the central highlands “Transition Zone” of Arizona is an excellent example of this phenomenon. There, an eventful geologic history caused a mosaic of distinct geologic formations, causing an extant patchy landscape of edaphic “islands”. In an approximate 70 square-mile area, there are twelve formations that form eight distinct geologic types. While some plant species are widespread and appear to be substrate generalists, many species have high fidelity to a particular edaphic substrate type. The marine and lacustrine limestones in particular host a high number of disjuncts from distant floristic affinities and multiple regional and narrow endemics. Three of these endemics are the sensitive species Salvia dorrii ssp. meansii (Lamiaceae), Eriogonum ripleyi (Polygonaceae) and the endangered Purshia subintegra (Rosaceae). The few small patches of gabbro and granite host altitudinal and spatial disjuncts. These include species such as Porphyllum gracile (Asteraceae) from the lower-elevation Sonoran Desert, Chaemaecyse dioica (Euphorbiaceae) and Schistophragma intermedia (Plantaginaceae), which are most common in the Madrean Floristic Province hundreds of miles to the south and the Arizona endemic Eremogone aberrans (Caryophyllaceae). Other suites of species are associated with the basaltic and sandstone formations.  The species richness of the Flora of the Upper Verde River is greatly enhanced with the presence of each geologic type. For instance, from a base number of approximately 260 generalists, the basalt soils bring the number up to 370. With the addition of limestone and dolostones, the number increases to ca. 525, and with addition of granite, gabbro and Tapeats sandstone, the richness increases to ca. 625 species. The Flora of the Upper Verde River in central Arizona provides an excellent model for the enhancement of regional plant species richness by the presence of geologic complexity.

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1 - Arizona State University, School of Life Sciences, 427 E Tyler Mall, Tempe, AZ, 85281, USA

Edaphic specialization
Edaphic Endemic
rare species
species distribution
Calcareous Soils

Presentation Type: Poster:Posters for Sections
Session: P
Location: Eyrie/Boise Centre
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PEC018
Abstract ID:853
Candidate for Awards:Ecological Section Best Graduate Student Poster


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