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Evolution of leaf structure and drought tolerance in species of Californian Ceanothus
Author(s) -
Fletcher Leila R.,
Cui Hongxia,
Callahan Hilary,
Scoffoni Christine,
John Grace P.,
Bartlett Megan K.,
Burge Dylan O.,
Sack Lawren
Publication year - 2018
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/ajb2.1164
Subject(s) - biology , allometry , turgor pressure , drought tolerance , arid , subgenus , botany , specific leaf area , xylem , range (aeronautics) , deserts and xeric shrublands , phylogenetic comparative methods , phylogenetic tree , ecology , genus , biochemistry , photosynthesis , materials science , gene , composite material , habitat
Premise of the Study Studies across diverse species have established theory for the contribution of leaf traits to plant drought tolerance. For example, species in more arid climates tend to have smaller leaves of higher vein density, higher leaf mass per area, and more negative osmotic potential at turgor loss point (π TLP ). However, few studies have tested these associations for species within a given lineage that have diversified across an aridity gradient. Methods We analyzed the anatomy and physiology of 10 Ceanothus (Rhamnaceae) species grown in a common garden for variation between and within “wet” and “dry” subgenera ( Ceanothus and Cerastes , respectively) and analyzed a database for 35 species for leaf size and leaf mass per area ( LMA ). We used a phylogenetic generalized least squares approach to test hypothesized relationships among traits, and of traits with climatic aridity in the native range. We also tested for allometric relationships among anatomical traits. Key Results Leaf form, anatomy, and drought tolerance varied strongly among species within and between subgenera. Cerastes species had specialized anatomy including hypodermis and encrypted stomata that may confer superior water storage and retention. The osmotic potentials at turgor loss point (π TLP ) and full turgor (π o ) showed evolutionary correlations with the aridity index ( AI ) and precipitation of the 10 species’ native distributions, and LMA with potential evapotranspiration for the 35 species in the larger database. We found an allometric correlation between upper and lower epidermal cell wall thicknesses, but other anatomical traits diversified independently. Conclusions Leaf traits and drought tolerance evolved within and across lineages of Ceanothus consistently with climatic distributions. The π TLP has signal to indicate the evolution of drought tolerance within small clades.