Coevolution with hosts underpins speciation in brood-parasitic cuckoos.

Coevolution between interacting species is thought to increase biodiversity, but evidence linking microevolutionary processes to macroevolutionary patterns is scarce. We leveraged two decades of behavioral research coupled with historical DNA analysis to reveal that coevolution with hosts underpins speciation in brood-parasitic bronze-cuckoos. At a macroevolutionary scale, we show that highly virulent brood-parasitic taxa have higher speciation rates and are more likely to speciate in sympatry than less-virulent and nonparasitic relatives. We reveal the microevolutionary process underlying speciation: Hosts reject cuckoo nestlings, which selects for mimetic cuckoo nestling morphology. Where cuckoos exploit multiple hosts, selection for mimicry drives genetic and phenotypic divergence corresponding to host preference, even in sympatry. Our work elucidates perhaps the most common, but poorly characterized, evolutionary process driving biological diversification.

Genetic variants in the human glucocorticoid-induced leucine zipper (GILZ) gene in fertile and infertile men.

Sertoli cell only (SCO) syndrome is the predominant histology for men with non-obstructive azoospermia (NOA) and is usually of unexplained aetiology. Studies in mouse models indicated that the X-linked gene glucocorticoid-induced leucine zipper (GILZ) is essential for survival and differentiation of spermatogonia, and meiosis. GILZ deficiency results in a rapid and progressive loss of germ cells with SCO tubules and sterility in adults. The role of GILZ in human fertility has not been examined. Here we show that GILZ is localized to spermatogonia and spermatocytes in the human testis in a pattern analogous to that seen in mice. To assess the potential for an association between GILZ variants and human infertility, we sequenced the entire protein-coding regions of the GILZ gene in 65 SCO and 87 fertile Australian men. We identified six genetic variants, three of which had not been reported previously. Three variants, 107018665 G>A, 107018485 C>G and 106959283 C>T, were found at a low frequency only in SCO men. Although none of the identified variants changed the protein code, sequence analysis indicated that two variants, 107018665 G>A and 107018485 C>G, would completely abolish the exonic splicing enhancer (ESE)-binding motifs for the splicing factors SF2/ASF and SC35 respectively. This result prompted an assessment of whether these two variants were associated with male infertility in a separate population of men. We used a PCR-based SNP detection approach to screen an additional 52 NOA and 153 fertile Australian men, and 86 SCO and 54 fertile American men. None of these men carried either of these two variants. The cumulative allelic frequency of these variants is less than 1% in SCO men and no association with fertility status was observed. Our study suggests that GILZ variants are not common causes of SCO and NOA in Australian or American men.