Phylogenetic Maximum Likelihood tree of the somatostatin receptor gene family

Published in: Ocampo Daza D, Sundström G, Bergqvist CA, Larhammar D. The evolution of vertebrate somatostatin receptors and their gene regions involves extensive chromosomal rearrangements. BMC Evolutionary Biology 2012, 12:231 doi:10.1186/1471-2148-12-231. Please refer to this article if using this figure.

Figure 1 Phylogenetic Maximum Likelihood tree of the somatostatin receptor gene
family. The topology is supported by a non-parametric bootstrap test with 100 replicates as
well as an SH-like approximate likelihood ratio test (aLRT). The tree is rooted with the
human kisspeptin receptor 1 sequence (not shown). Branch support (bootstrap replicates) for
deep divergences is shown at the nodes. All branch support values are shown in Figure S1
(bootstrap replicates) and Figure S2 (aLRT) (see Additional file 2). The phylogenetic tree
shows six well-supported subtype clusters, with the somatostatin receptor subtypes SSTR2, -3
and -5 forming one ancestral branch and the SSTR1, -4 and -6 receptor subtypes forming one
ancestral branch. This phylogenetic analysis supports the emergence of all six subtypes early
in vertebrate evolution, with the subsequent loss of SSTR4 in ray-finned fishes, before the
divergence of the spotted gar and teleost lineages, and of SSTR6 in the tetrapod lineage. All
six subtypes could be identified in the coelacanth genome. A seventh SSTR2-like sequence,
called SSTRX in the tree, could also be identified on the same genomic scaffold in the
coelacanth genome (see Additional file 1, Supplemental note 1). There are well-supported
teleost-specific duplicate branches of SSTR2, -3 and -5, although all could not be identified in
all teleost genomes. These duplicates have been named a and b based on the phylogenetic
analysis. There is a third SSTR3 sequence in the green puffer, called SSTR3c in the tree.