10.5061/DRYAD.93P7F
Sundue, Michael A.
Department of Plant Biology
Rothfels, Carl J.
Duke University
Data from: Stasis and convergence characterize morphological evolution in
eupolypod II ferns
Dryad
dataset
2014
Athyriaceae
symplesiomorphy
character state reconstruction
Woodsiaceae
Convergent evolution
Eupolypods II
Polypodiales
Rhachidosoraceae
rate of evolution
Diplaziopsidaceae
2014-10-07T00:00:00Z
2014-10-07T00:00:00Z
en
https://doi.org/10.1093/aob/mct247
18633 bytes
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CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Background and Aims: Patterns of morphological evolution at levels above
family rank remain underexplored in the ferns. The present study seeks to
address this gap through analysis of 79 morphological characters for 81
taxa, including representatives of all ten families of eupolypod II ferns.
Recent molecular phylogenetic studies demonstrate that the evolution of
the large eupolypod II clade (which includes nearly one-third of extant
fern species) features unexpected patterns. The traditional ‘athyrioid’
ferns are scattered across the phylogeny despite their apparent
morphological cohesiveness, and mixed among these seemingly conservative
taxa are morphologically dissimilar groups that lack any obvious features
uniting them with their relatives. Maximum-likelihood and
maximum-parsimony character optimizations are used to determine characters
that unite the seemingly disparate groups, and to test whether the
polyphyly of the traditional athyrioid ferns is due to evolutionary stasis
(symplesiomorphy) or convergent evolution. The major events in eupolypod
II character evolution are reviewed, and character and character state
concepts are reappraised, as a basis for further inquiries into fern
morphology. Methods: Characters were scored from the literature, live
plants and herbarium specimens, and optimized using maximum-parsimony and
maximum-likelihood, onto a highly supported topology derived from
maximum-likelihood and Bayesian analysis of molecular data. Phylogenetic
signal of characters were tested for using randomization methods and
fitdiscrete. Key Results: The majority of character state changes within
the eupolypod II phylogeny occur at the family level or above. Relative
branch lengths for the morphological data resemble those from molecular
data and fit an ancient rapid radiation model (long branches subtended by
very short backbone internodes), with few characters uniting the
morphologically disparate clades. The traditional athyrioid ferns were
circumscribed based upon a combination of symplesiomorphic and homoplastic
characters. Petiole vasculature consisting of two bundles is ancestral for
eupolypods II and a synapomorphy for eupolypods II under deltran
optimization. Sori restricted to one side of the vein defines the recently
recognized clade comprising Rhachidosoraceae through Aspleniaceae, and
sori present on both sides of the vein is a synapomorphy for the
Athyriaceae sensu stricto. The results indicate that a chromosome base
number of x =41 is synapomorphic for all eupolypods, a clade that includes
over two-thirds of extant fern species. Conclusions: The integrated
approach synthesizes morphological studies with current phylogenetic
hypotheses and provides explicit statements of character evolution in the
eupolypod II fern families. Strong character support is found for
previously recognized clades, whereas few characters support previously
unrecognized clades. Sorus position appears to be less complicated than
previously hypothesized, and linear sori restricted to one side of the
vein support the clade comprising Aspleniaceae, Diplaziopsidaceae,
Hemidictyaceae and Rachidosoraceae – a lineage only recently identified.
Despite x =41 being a frequent number among extant species, to our
knowledge it has not previously been demonstrated as the ancestral state.
This is the first synapomorphy proposed for the eupolypod clade, a lineage
comprising 67 % of extant fern species. This study provides some of the
first hypotheses of character evolution at the family level and above in
light of recent phylogenetic results, and promotes further study in an
area that remains open for original observation.
eupolypodsII_character_matrixIncludes 79 discrete morphological characters
scored for 81 taxa and one tree file depicting relationships of eupolypod
II fernsfinal_matrix_Eu2_Aug_2013_Dryad.nex