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Phylogenetic relationships among corytophanine iguanid lizards inferred from morphological characters
Raul Diaz
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Phylogenetic relationships among corytophanine iguanid lizards inferred from morphological characters Introduction Corytophanine
lizards form a clade within the Iguanidae whose major diagnostic character
is a head crest supported by a bony projection of the parietal bone.
Their neotropical distribution extends from Mexico to Colombia, with
its main concentration in Central America. Three genera of corytophanines
have traditionally been recognized: Basiliscus (four species),
Corytophanes (three species), and Laemanctus (two species).
We inferred the phylogenetic relationships among the species of corytophanine
lizards using morphological characters and tested various hypotheses
about the taxonomy of the group.
Characters
were obtained from the literature [primarily from Etheridge and de Queiroz
(1988), Frost and Etheridge (1989), and Lang (1989)] and verified using
museum specimens. New characters were also identified based on published
studies on Basiliscus (Maturana, 1962) and Laemanctus
(McCoy, 1968) and from personal observation. All currently recognized
species were included as terminal taxa; Enyalioides laticeps,
Dipsosaurus dorsalis, and Polychrus marmoratus were included
as outgroups to root the tree. Phylogenetic analysis were conducted
using the parsimony criterion using MacClade 4.0® (Maddison and
Maddison, 2000) and PAUP* 4.0b10 (Swofford, 2002). Permutation tests
(1000 replicates, heuristic searches) were used to evaluate non-random
hierarchical structure in the data. Phylogenetic relationships were
estimated using a branch and bound search. Non-parametric bootstrap
analysis (1000 replicates, branch and bound searches) was used to assess
nodal support on the tree. Taxonomic hypothesis were tested using constraint
trees and standard statistical tests [Kishino-Hasegawa (1989), Templeton
Test (1983), and Winning-sites Test (Prager and Wilson, 1988)].
We compiled a list of 94 characters (56 characters were treated as unordered, 4 partially ordered, and 34 ordered), 55 of which are informative under the parsimony criterion. The data exhibits significant non-random hierarchical structure (permutation tail probability = 0.001). Using all 3 outgroup taxa, a single most parsimonious tree was found (length = 188, rescaled consistency index = 0.4651), but the tree could not be rooted to make the ingroup monophyletic. However, when a single outgroup was used, the ingroup trees were identical and always rooted along the same branch no matter which taxon was chosen as the outgroup. Therefore, all subsequent analysis were conducted using only Dipsosaurus as the outgroup (length of most parsimonious tree = 135, rescaled consistency index = 0.6780; see figure). The
bootstrap analysis revealed 2 strongly supported (bootstrap proportion
= 100%) and 4 moderately supported (bootstrap proportion = 69-88%) groups.
The two strongly supported groups, monophyly of Corytophanes
and monophyly of Corytophanes + Laemanctus, also explain
the data significantly better than the best trees in which those groups
are not monophyletic (see table). Non-monophyly of Basiliscus
and non-monophyly of Laemanctus were not rejected by our data.
Similarly, our data did not reject either Lang’s (1989) tree based
on morphology or an unpublished tree based on mitochondrial DNA sequences
(tree supplied by James A. Schulte, II).
Our study provided a fully resolved phylogenetic tree with moderate to high levels of support for the various groups. We were able to resolve the polytomy in Lang’s (1989) tree among Basiliscus vittatus, B. galeritus, and B. basiliscus + B. plumifrons, however support for our resolution of this polytomy is low (47%) and is contradicted by the DNA data. There is high congruence between the relationships found in this study based on morphological and those inferred from DNA sequence data, suggesting that the inferred relationships are an accurate representation of the phylogeny of the group.
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