期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：34
DOI：10.1073/pnas.2205986119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
The diversification of canids in South America represents one of the most striking radiations of carnivorous mammals, comprising both small and large species, as well as hypercarnivorous and frugivorous forms. However, the timing, relationships, and geographic and climatic constraints on this radiation are not well understood. We show that canids colonized that continent from a single ancestral species between 3.9 and 3.5 million years ago. Canids first diversified in eastern South America, followed by a colonization and diversification west of the Andes with demographic histories influenced by habitat shifts during Pleistocene climatic cycles. We show that the phenotypic divergence of the bush dog and maned wolf reflect changes in the regulation and composition of genes underlying dental and skeletal traits.
The remarkable radiation of South American (SA) canids produced 10 extant species distributed across diverse habitats, including disparate forms such as the short-legged, hypercarnivorous bush dog and the long-legged, largely frugivorous maned wolf. Despite considerable research spanning nearly two centuries, many aspects of their evolutionary history remain unknown. Here, we analyzed 31 whole genomes encompassing all extant SA canid species to assess phylogenetic relationships, interspecific hybridization, historical demography, current genetic diversity, and the molecular bases of adaptations in the bush dog and maned wolf. We found that SA canids originated from a single ancestor that colonized South America 3.9 to 3.5 Mya, followed by diversification east of the Andes and then a single colonization event and radiation of
Lycalopex species west of the Andes. We detected extensive historical gene flow between recently diverged lineages and observed distinct patterns of genomic diversity and demographic history in SA canids, likely induced by past climatic cycles compounded by human-induced population declines. Genome-wide scans of selection showed that disparate limb proportions in the bush dog and maned wolf may derive from mutations in genes regulating chondrocyte proliferation and enlargement. Further, frugivory in the maned wolf may have been enabled by variants in genes associated with energy intake from short-chain fatty acids. In contrast, unique genetic variants detected in the bush dog may underlie interdigital webbing and dental adaptations for hypercarnivory. Our analyses shed light on the evolution of a unique carnivoran radiation and how it was shaped by South American topography and climate change.
