Stepwise evolution of Paleozoic tracheophytes from South China: contrasting leaf disparity and taxic diversity

Xue, Jinzhuang, Huang, Pu, Ruta, Marcello , Benton, Michael J., Hao, Shougang, Xiong, Conghui, Cascales-Minana, Borjas, Wang, Qi and Liu, Le (2015) Stepwise evolution of Paleozoic tracheophytes from South China: contrasting leaf disparity and taxic diversity. Earth-Science Reviews, 148 . pp. 77-93. ISSN 0012-8252

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During the late Paleozoic, vascular land plants (tracheophytes) diversified into a remarkable variety of morpho-
logical types, ranging from tiny, aphyllous, herbaceous forms to giant leafy trees. Leaf shape is a key determinant
of both function and structural diversity of plants, but relatively little is known about the tempo and mode of leaf
morphological diversification and its correlation with tracheophyte diversity and abiotic changes during this re-
markable macroevolutionary event, the greening of the continents. We use the extensive record of Paleozoic tra-
cheophytes from South China to explore models of morphological evolution in early land plants. Our findings
suggest that tracheophyte leaf disparity and diversity were decoupled, and that they were under different selec-
tive regimes. Two key phases in the evolution of South Chinese tracheophyte leaves can be recognized. In the first
phase, from Devonian to Mississippian, taxic diversity increased substantially, as did leaf disparity, at the same
time as they acquired novel features in their vascular systems, reproductive organs, and overall architecture.
The second phase, through the Carboniferous–Permian transition, saw recovery of wetland communities in
South China, associated with a further expansion of morphologies of simple leaves and an offset shift in
morphospace occupation by compound leaves. Comparison with Euramerica suggests that the floras from
South China were unique in several ways. The Late Devonian radiation of sphenophyllaleans contributed signif-
icantly to the expansion of leaf morphospace, such that the evolution of large laminate leaves in this group oc-
curred much earlier than those in Euramerica. The Pennsylvanian decrease in taxic richness had little effect on
the disparity of compound leaves. Finally, the distribution in morphospace of the Permian pecopterids,
gigantopterids, and equisetaleans occurred at the periphery of Carboniferous leaf morphospace.

Keywords:Leaf morphology, Disparity, Diversity, Tracheophytes, Floral provinciality, Paleozoic, bmjgoldcheck, NotOAChecked
Subjects:C Biological Sciences > C182 Evolution
C Biological Sciences > C191 Biometry
F Physical Sciences > F641 Palaeontology
C Biological Sciences > C200 Botany
C Biological Sciences > C181 Biodiversity
Divisions:College of Science > School of Life Sciences
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ID Code:17590
Deposited On:09 Jun 2015 12:55

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