TY - JOUR
T1 - Adaptive radiation of photosynthetic physiology in the Hawaiian lobeliads
T2 - Light regimes, static light responses, and whole-plant compensation points
AU - Givnish, Thomas J.
AU - Montgomery, Rebecca A.
AU - Goldstein, Guillermo
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2004/2
Y1 - 2004/2
N2 - Six endemic genera/sections of lobeliads (Campanulaceae) occupy nearly the full range of light regimes on moist sites in the Hawaiian Islands, from open alpine bogs and seacliffs to densely shaded rainforest interiors. To determine whether this clade has undergone a corresponding adaptive radiation in photosynthetic adaptations, we studied the natural light habitats and physiological characteristics of 11 species representing each sublineage. Across species in the field, average photon flux density (PFD) varies from 2.3 to 30.0 mol · m-2 · d-1, and maximum assimilation rate (Amax) ranges from 0.17 to 0.35 μmol CO 2 · g-1 · s-1. Across species, Amax, dark respiration rate (R), Michaelis-Menten constant (k), light compensation point, specific leaf area (SLA), maximum carboxylation rate (Vcmax), maximum rate of electron transport (Jmax), photosynthesis at saturating CO2 (AsatCO2), and carboxylation efficiency (α) all increase significantly and in tightly coupled fashion with PFD, in accord with classical economic theory. Area-based rates have a higher degree of physiological integration with each other and tighter coupling to PFD than the corresponding mass-based rates, despite the energetic importance of the latter. Area-based rates frequently show adaptive cross-over: high-light species outperform low-light species at high PFD and vice versa at low PFD. Amax-mass has little relationship to leaf mass per unit area (LMA), leaf N content, or leaf lifespan individually, but a multiple regression explains 96% of the variance in Amax-mass across species in terms of SLA, leaf N content, and average PFD. Instantaneous leaf compensation points range from 0.1 to 1.2% full sunlight, far lower than the ecological (whole-plant) compensation points (ECPs) of 1.1 to 29.0% sunlight calculated based on photosynthetic parameters, leaf longevity, and allocation to leaf vs. nonleaf tissue. The ECPs are much closer to the lower limits of PFD actually experienced by lobeliads, suggesting they may play an important role in restricting species distributions. Taken together, these data provide evidence for an adaptive radiation in photosynthetic traits that is strongly correlated with - and indeed may help determine - the light regime that each species inhabits.
AB - Six endemic genera/sections of lobeliads (Campanulaceae) occupy nearly the full range of light regimes on moist sites in the Hawaiian Islands, from open alpine bogs and seacliffs to densely shaded rainforest interiors. To determine whether this clade has undergone a corresponding adaptive radiation in photosynthetic adaptations, we studied the natural light habitats and physiological characteristics of 11 species representing each sublineage. Across species in the field, average photon flux density (PFD) varies from 2.3 to 30.0 mol · m-2 · d-1, and maximum assimilation rate (Amax) ranges from 0.17 to 0.35 μmol CO 2 · g-1 · s-1. Across species, Amax, dark respiration rate (R), Michaelis-Menten constant (k), light compensation point, specific leaf area (SLA), maximum carboxylation rate (Vcmax), maximum rate of electron transport (Jmax), photosynthesis at saturating CO2 (AsatCO2), and carboxylation efficiency (α) all increase significantly and in tightly coupled fashion with PFD, in accord with classical economic theory. Area-based rates have a higher degree of physiological integration with each other and tighter coupling to PFD than the corresponding mass-based rates, despite the energetic importance of the latter. Area-based rates frequently show adaptive cross-over: high-light species outperform low-light species at high PFD and vice versa at low PFD. Amax-mass has little relationship to leaf mass per unit area (LMA), leaf N content, or leaf lifespan individually, but a multiple regression explains 96% of the variance in Amax-mass across species in terms of SLA, leaf N content, and average PFD. Instantaneous leaf compensation points range from 0.1 to 1.2% full sunlight, far lower than the ecological (whole-plant) compensation points (ECPs) of 1.1 to 29.0% sunlight calculated based on photosynthetic parameters, leaf longevity, and allocation to leaf vs. nonleaf tissue. The ECPs are much closer to the lower limits of PFD actually experienced by lobeliads, suggesting they may play an important role in restricting species distributions. Taken together, these data provide evidence for an adaptive radiation in photosynthetic traits that is strongly correlated with - and indeed may help determine - the light regime that each species inhabits.
KW - Adaptive cross-over
KW - Adaptive radiation
KW - Brighamia
KW - Clermontia
KW - Cyanea
KW - Delissea
KW - Lobelia
KW - Photosynthetic light response
KW - Trematolobelia
UR - http://www.scopus.com/inward/record.url?scp=1342287533&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=1342287533&partnerID=8YFLogxK
U2 - 10.3732/ajb.91.2.228
DO - 10.3732/ajb.91.2.228
M3 - Article
C2 - 21653379
AN - SCOPUS:1342287533
SN - 0002-9122
VL - 91
SP - 228
EP - 246
JO - American journal of botany
JF - American journal of botany
IS - 2
ER -