Short distances between extreme microhabitats do not result in ecotypes in Syntrichia caninervis

Abstract

Phenotypic variation occurs in many populations of plants. When this variation occurs along an environmental gradient, the immediate question is whether the variation is attributed to phenotypic plasticity, ecotypes, or some combination of the two. The moss Syntrichia caninervis appears morphologically variable along an environmental gradient changing rapidly from low light, low temperature, and high moisture levels in the understory microhabitat to high light, high temperature, and low moisture levels in the intershrub microhabitat. We tested for the presence of physiological variation using recovery from a heat-shock event in a mimicked microhabitat light environment, and for morphological variation using a common garden with the ultimate goal of attributing observed variation to plasticity, genetic variation, or a combination. The results suggest that plasticity plays a large role in trait variation. Photosynthetic recovery depended on the current light levels of an environment and not the original microhabitat. The supposed morphological variation in the field was not reflected in the test traits (awn length, leaf area, and shoot volume) and further growth in a common garden continued to show no variation between microhabitats.

Keywords:

• Common garden
• Desert
• Ecotypes
• F_v/F_m
• Phenotypic plasticity

We thank C. Walter for laboratory assistance, J. Brinda for comments, and L. Stark for his hospitality in hosting our field work and many valuable comments when editing this manuscript. LAR was supported by REU supplement to National Science Foundation grant no. IOB 0416281 (DNM).

Taxonomic Additions and Changes: Nil.