Phylogeographic structure across one of the largest intact tropical savannahs: Molecular and morphological analysis of Australia's iconic frilled lizard Chlamydosaurus kingii.
The spectacular threat display of the savannah specialist Australo-Papuan frilled lizards has made them one of the world's most iconic reptiles. They are increasingly used as a model system for research in evolutionary biology and ecology but little is known of their population structure. Their distribution across northern Australia and southern New Guinea also provides an opportunity to examine biogeographic patterns as they relate to the large-scale movement of savannah habitat during the Plio/Pleistocene and the associated increase in aridity. We generated sequence data for one mitochondrial and four nuclear DNA loci (5052 base pairs) for 83 frilled lizards sampled throughout their range. We also quantified body proportion variation for 279 individuals. Phylogenetic analyses based on maximum likelihood and Bayesian species-tree methods revealed three shallow clades that replace each other across the monsoon tropics. We found the expected pattern of male biased sexual size dimorphism in both maximum body size and head size but there was no sexual dimorphism in overall body shape or in frill size, relative to head size, supporting the hypothesis that the frill is used primarily as a threat display rather than a sexual display. The genetic clades are broadly consistent with known clinal variation in frill color that gradually shifts from west to east (red, orange, yellow/white) but otherwise show little morphological differentiation in body proportion measures. The biogeographic breaks between clades occur at the Carpentaria Gap and the lowlands surrounding the Ord River, and our ecological niche modeling predicts lower habitat suitability for C. kingii in these regions. While this biogeographic pattern is consistent with numerous other taxonomic groups in northern Australia, the overall low genetic diversity in frilled lizards across the entire monsoon tropics and southern New Guinea contrasts starkly to patterns seen in other terrestrial vertebrates. Extremely low intra-clade genetic diversity over vast geographic areas is indicative of recent gene flow that would likely have been facilitated by widespread savannah during interglacials, or alternatively may reflect population bottlenecks induced by extreme aridity during Pleistocene glacials. The shallow divergence between Australian and New Guinean samples is consistent with recent connectivity between Australia and New Guinea that would have been possible via a savannah corridor across the Torres Strait. Based on our molecular and morphological data, we do not support taxonomic recognition of any of the frilled lizard clades and instead consider C. kingii a single species with shallow phylogeographic structure and clinal variation in frill color.
Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australia. Electronic address: mitzy.Pepper@anu.edu.au.
Mitzy
M
Pepper
Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australia.
David G
DG
Hamilton
Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australia.
Thomas
T
Merkling
Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australia.
Nina
N
Svedin
Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australia.
Bori
B
Cser
School of Science and Health, Western Sydney University, Penrith, NSW, Australia; CSIRO Land and Water, Black Mountain, Canberra, Australia.
Renee A
RA
Catullo
Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australia.
Sarah R
SR
Pryke
Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australia.
J Scott
JS
Keogh
D000818:Animals; D001315:Australia; D001499:Bayes Theorem; D005075:Biological Evolution; D004247:DNA / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000145:classification / Q000235:genetics / Q000378:metabolism; D005260:Female; D051456:Gene Flow; D014644:Genetic Variation; D008116:Lizards / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics; D008297:Male; D009512:New Guinea; D010802:Phylogeny; D058974:Phylogeography; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial; D004247:DNA
Carpentarian Gap; Monsoon tropics; Ord River; Phylogeography; Torres Strait; Trans-Fly