 |
in Brennan, Chapple, Keogh ... et Donnellan, 2024. |
Highlights:
• A new and reliable species tree of Tiliquini skinks (bluetongues and relatives)
• Patterns of morphological trait evolution are heterogeneous
• Nested “bursts” in evolution lead to new phenotypes
Summary
Animal phenotypes evolve and diverge as a result of differing selective pressures and drift. These processes leave unique signatures in patterns of trait evolution, impacting the tempo and mode of morphological macroevolution. While there is a broad understanding of the history of some organismal traits (e.g., body size), there is little consensus about the evolutionary mode of most others. This includes the relative contribution of prolonged (Darwinian gradualist) and episodic (Simpsonian jump) changes toward the evolution of novel morphologies. Here, we use new exon-capture and linear morphological datasets to investigate the tempo and mode of morphological evolution in Australo-Melanesian Tiliquini skinks. We generate a well-supported time-calibrated phylogenomic tree from ∼400 nuclear markers for more than 100 specimens, including undescribed diversity, and provide unprecedented resolution of the rapid Miocene diversification of these lizards. By collecting a morphological dataset that encompasses the lizard body plan (19 traits across the head, body, limb, and tail), we are able to identify that most traits evolve conservatively, but infrequent evolutionary bursts result in morphological novelty. These phenotypic discontinuities occur via rapid rate increases along individual branches, inconsistent with both gradualistic and punctuated equilibrial evolutionary modes. Instead, this “punctuated gradualism” has resulted in the rapid evolution of blue-tongued giants and armored dwarves in the ∼20 million years since colonizing Australia. These results outline the evolutionary pathway toward new morphologies and highlight the heterogeneity of evolutionary tempo and mode, even within individual traits.
Keywords: morphological evolution, Simpsonian, skink phylogenomics, Tiliquini
Ian G. Brennan, David G. Chapple, J. Scott Keogh ... et Stephen Donnellan. 2024. Evolutionary Bursts drive Morphological novelty in the World’s Largest Skinks. Current Biology. In Press. DOI: doi.org/10.1016/j.cub.2024.07.039
(a) Monkey-tailed skink (Corucia zebrata) (b) Western bluetongue (Tiliqua occipitalis)
(c) Shingleback lizard (Tiliqua rugosa) (d) Yakka skink (Egernia rugosa)
(e) Tree skink (Egernia striolata) (f) Pygmy spiny-tailed skink (Egernia depressa)
(g) Mainland She-oak skink (Cyclodomorphus michaeli) (h) Crocodile skink (Tribolonotus gracilis)
... These lizards represent some of the extremes of the diversity we see in the 'Social Skinks' a group mostly found in Australia.
