No abstract

The yellow gene family is intriguing for a number of reasons. To date, yellow-like genes have only been identified in insect species and a number of bacteria. The function of the yellows is largely unknown, although a few have been associated with melanization and behavior in Drosophila, and a unique clade of genes from Apis mellifera may be involved in caste specification. Here, we show that yellow-like sequences are present in bacteria, insects, and fungi but absent from other eukaryotes apart from isolated putative sequences in Amphioxus, the Salmon Louse, and Naegleria. The yellow-like family forms a discrete gene class characterized by the presence of a major royal jelly protein domain, but eukaryote yellow-like proteins are not monophyletic. The unusual phylogenetic distribution of yellow-like sequences suggests either multiple horizontal transfer from bacteria into eukaryotes or extensive gene loss in eukaryote lineages. Comparative analysis of yellow family synteny and gene order demonstrates that a highly conserved block of three to five genes has been maintained throughout insect diversification despite extensive genome rearrangements. We show strong purifying selection on seven yellow genes over approximately 100 My separating the silkmoth and Heliconius butterflies and an association between spatial regulation of gene expression and distribution of melanic pigment in the developing butterfly wing. A single ancestral yellow-like gene has therefore undergone multiple rounds of duplication within the insects accompanied by functional constraint on both genomic location and protein evolution.

Relationships between androgens and the size of sexually dimorphic male traits have been demonstrated in several non-human species. It is often assumed that a similar relationship exists for human male faces, but clear evidence of an association between circulating testosterone levels and the size of masculine facial traits in adulthood is absent. Here we demonstrate that, after experimentally determined success in a competitive task, men with more a masculine facial structure show higher levels of circulating testosterone than men with less masculine faces. In participants randomly allocated to a 'winning' condition, testosterone was elevated relative to pre-task levels at 5 and 20 min post-task. In a control group of participants allocated to a 'losing' condition there were no significant differences between pre-and posttask testosterone. An index of facial masculinity based on the measurement of sexually dimorphic facial traits was not associated with pre-task (baseline) testosterone levels, but was associated with testosterone levels 5 and 20 min after success in the competitive task. These findings indicate that a man's facial structure may afford important information about the functioning of his endocrine system.

Homoploid hybrid speciation is the formation of a new hybrid species without change in chromosome number. So far, there has been a lack of direct molecular evidence for hybridization generating novel traits directly involved in animal speciation. Heliconius butterflies exhibit bright aposematic color patterns that also act as cues in assortative mating. Heliconius heurippa has been proposed as a hybrid species, and its color pattern can be recreated by introgression of the H. m. melpomene red band into the genetic background of the yellow banded H. cydno cordula. This hybrid color pattern is also involved in mate choice and leads to reproductive isolation between H. heurippa and its close relatives. Here, we provide molecular evidence for adaptive introgression by sequencing genes across the Heliconius red band locus and comparing them to unlinked wing patterning genes in H. melpomene, H. cydno, and H. heurippa. 670 SNPs distributed among 29 unlinked coding genes (25,847bp) showed H. heurippa was related to H. c. cordula or the three species were intermixed. In contrast, among 344 SNPs distributed among 13 genes in the red band region (18,629bp), most showed H. heurippa related with H. c. cordula, but a block of around 6,5kb located in the 3′ of a putative kinesin gene grouped H. heurippa with H. m. melpomene, supporting the hybrid introgression hypothesis. Genealogical reconstruction showed that this introgression occurred after divergence of the parental species, perhaps around 0.43Mya. Expression of the kinesin gene is spatially restricted to the distal region of the forewing, suggesting a mechanism for pattern regulation. This gene therefore constitutes the first molecular evidence for adaptive introgression during hybrid speciation and is the first clear candidate for a Heliconius wing patterning locus.

In the 1950s the myxoma virus was released into European rabbit populations in Australia and Europe, decimating populations and resulting in the rapid evolution of resistance. We investigated the genetic basis of resistance by comparing the exomes of rabbits collected before and after the pandemic. We found a strong pattern of parallel evolution, with selection on standing genetic variation favouring the same alleles in Australia, France and the United Kingdom. Many of these changes occurred in immunity-related genes, supporting a polygenic basis of resistance. We experimentally validated the role of several genes in viral replication and showed that selection acting on an interferon protein has increased its antiviral effect.