Figure 4: Silk genes in the velvet spider.

(a) Schematic overview of exon-intron and repeat structure of the identified silk genes. The repeats from a single locus share evolutionary history and are easy to align, except for S.m. Sp2c that consists of two sets of repeats (grey and blue) with different evolutionary histories. S.m. PiSp consists of sequences obtained from two scaffolds. PCR verified that they come from the same locus. (b) The evolutionary history of the major ampullate C-terminal domain, including the recent events of gene conversion, whole-gene duplication (~10 MYA) and pseudogenization* (Supplementary Note 3). Scale bar represents number of nucleotide differences per site. (c) Major ampullate repeat evolution over ~10 MY since a whole-gene duplication. The evolutionary relationship of repeats from two recently duplicated loci is depicted by a phylogenetic tree and repeat structures. Similar coloured repeats are evolutionarily most related. Scale bar represents the number of nucleotide differences per site. (d) Use of aciniform silk in the velvet spider compared with previously studied species that use aciniform silk to wrap their prey. Velvet spiders do not wrap their prey, but use aciniform silk for dragline silk in combination with major ampullate silk. Velvet spiders also use aciniform silk for egg case construction as do previously studied species.