Fig. 4

Sequence similarities and evolutionary relationships between SPF proteins. (A) Alignment of selected beta-SPF transcripts (numbers refer to transcripts used in the tree (B)). Protein sequences show a typical 10 + 8-cysteine pattern in the first and second motif, suggesting a high structural similarity (but note the slight deviation of cysteine position 2 in the second motif of the Plectrohyla sequences). (B) Maximum likelihood tree of 2-domain-TFPs (2D-TFP) from amphibians and teleost fish (outgroup). Anuran transcripts that originated from breeding glands are shown in green, salamander transcripts from breeding glands in blue (see Additional file 1). Nodes supported by all three assessment methods are indicated with a black circle, nodes only supported by one or two methods are indicated with blue, green and/or red (ultrafast Bootstrap > 95%, red; SH-aLRT > 80%, green; aBayes-support > 0.95, blue). Duplication events within the anuran SPF clade are marked with “D”, other nodes within this clade are considered speciation nodes (Notung analysis). Numbers 1–5 are referred to in the text