Journal
GENOME BIOLOGY AND EVOLUTION
Volume 7, Issue 7, Pages 1856-1870Publisher
OXFORD UNIV PRESS
DOI: 10.1093/gbe/evv110
Keywords
Theridiidae; Latrodectus; Steatoda; expression; patterns of selection; neofunctionalization
Categories
Funding
- National Science Foundation [IOS-0951886, IOS-0951061]
- National Institutes of Health [F32 GM78875-1A, 1F32GM083661-01, 1R15GM097714-01]
- Army Research Office [W911NF-06-1-0455, W911NF-11-1-0299]
- Washington and Lee University
- Direct For Biological Sciences
- Division Of Integrative Organismal Systems [0951061] Funding Source: National Science Foundation
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [0951086] Funding Source: National Science Foundation
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The evolution of specialized tissues with novel functions, such as the silk synthesizing glands in spiders, is likely an influential driver of adaptive success. Large-scale gene duplication events and subsequent paralog divergence are thought to be required for generating evolutionary novelty. Such an event has been proposed for spiders, but not tested. We de novo assembled transcriptomes from three cobweb weaving spider species. Based on phylogenetic analyses of gene families with representatives from each of the three species, we found numerous duplication events indicative of a whole genome or segmental duplication. We estimated the age of the gene duplications relative to several speciation events within spiders and arachnids and found that the duplications likely occurred after the divergence of scorpions (order Scorpionida) and spiders (order Araneae), but before the divergence of the spider suborders Mygalomorphae and Araneomorphae, near the evolutionary origin of spider silk glands. Transcripts that are expressed exclusively or primarily within black widow silk glands are more likely to have a paralog descended from the ancient duplication event and have elevated amino acid replacement rates compared with other transcripts. Thus, an ancient large-scale gene duplication event within the spider lineage was likely an important source of molecular novelty during the evolution of silk gland-specific expression. This duplication event may have provided genetic material for subsequent silk gland diversification in the true spiders (Araneomorphae).
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