American Journal of Botany
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30-1-2020
American Journal of Botany / Volume 106, Issue 6
Research Article
The monocotyledonous underground: global climatic and phylogenetic
patterns of geophyte diversity
Cody Coyotee Howard  , Ryan A. Folk , Jeremy M. Beaulieu , Nico Cellinese
First published: 20 May 2019
https://doi.org/10.1002/ajb2.1289
Citations: 2
Abstract
Premise
Geophytes—plants that typically possess a bulb, corm, tuber, and/or rhizome—have long
captured the attention of hobbyists and researchers. However, despite the economic and
evolutionary importance of these traits, the potential drivers of their morphological
diversity remain unknown. Using a comprehensive phylogeny of monocots, we test for
correlations between climate and geophyte growth form to better understand why we
observe such a diversity of underground traits in geophytes. Understanding the
evolutionary factors promoting independent origins of these potentially adaptive organs
will lend insights into how plants adapt to environmental hardships.
Methods
Using a comprehensive phylogeny incorporated with global occurrence and climate data
for the monocots, we investigated whether climatic patterns could explain di erences
between geophytes and non‐geophytes, as well as di erences among bulbous, cormous,
tuberous, rhizomatous, and non‐geophytic taxa. We used phylogenetically‐informed
ANOVAs, MANOVAs, and PCAs to test di erences in climatic variables between the
di erent growth forms.
Results
Geophytes inhabit cooler, drier, and more thermally variable climates compared to non‐
geophytes. Although some underground traits (i.e., bulb, corm, and tuber) appear to
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American Journal of Botany
inhabit particular niches, a result supported by strong phylogenetic signal, our data has
limited evidence for an overall role of climate in the evolution of these traits. However,
temperature may be a driving force in rhizome evolution, as well as the evolution of taxa
which we considered here as non‐geophytic (e.g., trees, epiphytes, etc.).
Conclusions
While precipitation patterns have played a role in the evolution of geophytism, our
results suggest that temperature should be more strongly considered as a contributing
factor promoting the evolution of belowground bud placement, speci cally in
rhizomatous and non‐geophytic taxa. Bulbous, cormous, and tuberous taxa need closer
examination of other mechanisms, such as anatomical constraints or genetic controls, in
order to begin to understand the causes behind the evolution of their underground
morphology.
Citing Literature
Supporting Information
Filename


Description
ajb21289-
APPENDIX S1. Taxonomic classi cation (order, family and species columns) for all 12,779
sup-0001-
taxa in addition to growth form coding (geophyte column) with references (reference
Appendix
column) used to infer character state. Numbers used for coding are 0 (bulb), 1 (corm), 2
S1.csv
(rhizome), 3 (tuber), and 4 (non‐geophyte). For list of references used for character coding,
CSV
see Appendix S2 .
document,
590.1 KB
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Filename
ajb21289-
Description
APPENDIX S2. Sources used for the character coding of geophytes found in Appendix S1 .
sup-0002-
Citation numbers correspond to the reference used to code each taxon (see reference
Appendix
column in Appendix S1 ).
S2.docx
Word
document,
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