HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Wu, C. A. Articles by Campbell, D. R. Search for Related Content PubMed Articles by Wu, C. A. Articles by Campbell, D. R. Agricola Articles by Wu, C. A. Articles by Campbell, D. R.

Leaf physiology reflects environmental differences and cytoplasmic background in Ipomopsis (Polemoniaceae) hybrids¹

Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92697 USA; Rocky Mountain Biological Laboratory, Crested Butte, Colorado 81224 USA

ABSTRACT

Natural hybridization can produce individuals that vary widely in fitness, depending upon the performance of particular genotypes in a given environment. In a hybrid zone with habitat heterogeneity, differences in physiological responses to abiotic conditions could influence the fitness and spatial distribution of hybrids and parental species. This study compared gas exchange physiology of Ipomopsis aggregata, I. tenuituba, and their natural hybrids in situ and assessed whether physiological differences were consistent with their native environmental conditions. We also produced reciprocal F2s in a greenhouse study to test for cytonuclear effects on water-use efficiency (WUE). The relative performance of natural hybrids and parentals was consistent with their native habitats: I. aggregata at the coolest, wettest locations had the lowest WUE, while hybrids from the most xeric sites had the highest WUE. In hybrids, the mechanism by which both natural and experimental hybrids achieved this high WUE depended on cytotype: those with I. tenuituba cytoplasm had reduced transpiration, while those with I. aggregata cytoplasm had an increased photosynthetic rate, consistent with patterns in the cytoplasmic parent. The high WUE in hybrids may contribute to their high survival in the dry center of the natural hybrid zone, consistent with environment-dependent models of hybrid zone dynamics.

Key Words: cytoplasmic effects • hybridization • Ipomopsis • physiological performance • Rocky Mountains • water-use efficiency