Genome of the Komodo dragon reveals adaptations in the cardiovascular and chemosensory systems of monitor lizards

Abstract

Monitor lizards are unique among ectothermic reptiles in that they have high aerobic capacity and distinctive cardiovascular physiology resembling that of endothermic mammals. Here, we sequence the genome of the Komodo dragon Varanus komodoensis, the largest extant monitor lizard, and generate a high-resolution de novo chromosome-assigned genome assembly for V. komodoensis using a hybrid approach of long-range sequencing and single-molecule optical mapping. Comparing the genome of V. komodoensis with those of related species, we find evidence of positive selection in pathways related to energy metabolism, cardiovascular homoeostasis, and haemostasis. We also show species-specific expansions of a chemoreceptor gene family related to pheromone and kairomone sensing in V. komodoensis and other lizard lineages. Together, these evolutionary signatures of adaptation reveal the genetic underpinnings of the unique Komodo dragon sensory and cardiovascular systems, and suggest that selective pressure altered haemostasis genes to help Komodo dragons evade the anticoagulant effects of their own saliva. The Komodo dragon genome is an important resource for understanding the biology of monitor lizards and reptiles worldwide.

Genomic bases underlying the adaptive radiation of core landbirds

“…Consistent with the enhanced capability of lipid utilization in birds of prey found in this study, previous genomic studies have well documented an enhanced lipid utilization in many carnivorous mammals (e.g., dog, cats, polar bear, cetaceans) [31][32][33][34][35][36][37][38][39][40] , carnivorous reptiles (e.g., pythons, Komodo dragons) 41,42 and even modern humans, such as the Maasai, who consume a fat-rich diet 43 . In addition to these findings at the molecular level, anatomically, carnivores are usually found to retain a gallbladder, and their gallbladders are relatively large, while for those animals that feed primarily on plant food, the gallbladder is absent or relatively small 26,44 .…”

Two decades of suspect evidence for adaptive DNA-sequence evolution – Less negative selection misconstrued as positive selection

“…In many species, there is no data on polymorphism. Nevertheless, the complete sequences of a diploid individual consist of two haploid genomes, which could provide information on polymorphism 30,[37][38][39][40][41] . If genomes of single individuals can be used in lieu of a polymorphism survey, then the database would expand greatly.…”

A chromosome-level genome assembly for the Eastern Fence Lizard (Sceloporus undulatus), a reptile model for physiological and evolutionary ecology

“…Despite having evolved greater phylogenetic diversity than mammals and birds, two major vertebrate groups with extensive genome sampling, genomic resources for squamates remain scarce and assemblies at the chromosome-level are even more rare [7, 9-13]. While squamates are known to have a level of karyotypic variability similar to that of mammals [14], the absence of high-quality genome assemblies has led to their exclusion from many chromosome-level comparative genome analyses.…”