Icons of Indiana’s Prairies 

The transition into wetter habitats by 
the ancestors of prairie-dock and cup- 
plant involved adaptation of their water 
conducting tissues. The greater reliability 
of soil moisture allowed selection of more 
vulnerable hydraulic traits, like greater vein 
size and decreases in structural material, 
and thus greater susceptibility to drought 
if it were to occur. Drought is dangerous to 
plants because it increases the chance of 
embolism, air bubbles that block veins, and 
the subsequent loss of function of adjacent 
leaf and stem tissue. 
Mason & Donovan (2015) observed that 
species in the family Asteraceae follow the 
so-called leaf economic spectrum. This is 
the idea that plants cannot invest resources 
infinitely, but must make specific tradeoffs that 
define the life strategies for individual species. 
In the genus Si/phium, tradeoffs centered 
on changes in leaf mass / inch’, lignin and 
cellulose content, and growth form within this 
genus. Regardless of the specific life strategy 
of our Si/phium species, each is beautifully 
adapted and collectively these iconic prairie 
wildflowers demonstrate a cross-habitat 
evolution that may become more important in 
the uncertain years to come. 
References 
Clevinger, J.A. & J.L. Panero. 2000. Phylogenetic 
analysis of Sijphium and subtribe Engelmanniinae 
(Asteraceae: Heliantheae) based on ITS and 
ETS sequence data. American Journal of Botany 
87:565—-572. 
Crisp, M.D., M.T.L. Arroyo, L.G. Cook, M.A. Gandolfo, 
G.J. Jordan, M.S. Mcglone & H.P. Linder. 2009. 
Phylogenetic biome conservatism on a global 
scale. Nature 458:754—756. 
Mason, C.M. & L.A. Donovan. 2015. Evolution of 
the leaf economics spectrum in herbs: evidence 
from environmental divergences in leaf physiology 
across Helianthus (Asteraceae). Evolution 
69:2705—2720. 
Josh Randall is a first year Ph.D. student in 
Ecology and Evolutionary Biology at Yale 
University, studying the evolution of leaf 
physiology in the shrub Viburnum. He completed 
his undergraduate in Botany at Purdue where 
he pursued research on Silphium and became 
excited by plant morphological diversity. 


Left: Compass- 
plant, like prairie- 
dock, sends up 
long flowering 
peduncles. 
Below: Prairie- 
dock has a basal 
rosette of leaves 
whose blades 
reach 18” long. 

Summer 2021 « Indiana Native Plant Society + 17 
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