Daniel Hooper

Sex chromosome inversions enforce reproductive isolation across an avian hybrid zone

Publisher: Wiley

Date: 24-10-2019

DOI: 10.1111/MEC.14874

Abstract: Across hybrid zones, the sex chromosomes are often more strongly differentiated than the autosomes. This is regularly attributed to the greater frequency of reproductive incompatibilities accumulating on sex chromosomes and their exposure in the heterogametic sex. Working within an avian hybrid zone, we explore the possibility that chromosome inversions differentially accumulate on the Z chromosome compared to the autosomes and thereby contribute to Z chromosome differentiation. We analyse the northern Australian hybrid zone between two subspecies of the long-tailed finch (Poephila acuticauda), first described based on differences in bill colour, using reduced-representation genomic sequencing for 293 in iduals over a 1,530-km transect. Autosomal differentiation between subspecies is minimal. In contrast, 75% of the Z chromosome is highly differentiated and shows a steep genomic cline, which is displaced 350 km to the west of the cline in bill colour. Differentiation is associated with two or more putative chromosomal inversions, each predominating in one subspecies. If inversions reduce recombination between hybrid incompatibilities, they are selectively favoured and should therefore accumulate in hybrid zones. We argue that this predisposes inversions to differentially accumulate on the Z chromosome. One genomic region affecting bill colour is on the Z, but the main candidates are on chromosome 8. This and the displacement of the bill colour and Z chromosome cline centres suggest that bill colour has not strongly contributed to inversion accumulation. Based on cline width, however, the Z chromosome and bill colour both contribute to reproductive isolation established between this pair of subspecies.

Experimentally testing mate preference in an avian system with unidirectional bill color introgression

Publisher: Wiley

Date: 02-2023

DOI: 10.1002/ECE3.9812

Abstract: Mating behavior can play a key role in speciation by inhibiting or facilitating gene flow between closely related taxa. Hybrid zones facilitate a direct examination of mating behavior and the traits involved in establishing species barriers. The long‐tailed finch ( Poephila acuticauda ) has two hybridizing subspecies that differ in bill color (red and yellow), and the yellow bill phenotype appears to have introgressed ~350 km eastward following secondary contact. To examine the role of mate choice on bill color introgression, we performed behavioral assays using natural and manipulated bill colors. We found an assortative female mating preference for males of their own subspecies when bill color was not manipulated. However, we did not find this assortative preference in trials based on artificially manipulated bill color. This could suggest that assortative preference is not fixed entirely on bill color and instead may be based on a different trait (e.g., song) or a combination of traits, or alternatively may be due to lower statistical power alongside the bill manipulations being unconvincing to the female choosers. Intriguingly, we find a bias in the inheritance of bill color in captive bred F1 hybrid females. Previous modeling suggests that assortative mate preference and this kind of partial dominance in the underlying genes may together contribute to introgression, making the genetic architecture of bill color in this system a priority for future research.

Evaluating evidence of mitonuclear incompatibilities with the sex chromosomes in an avian hybrid zone

Publisher: Wiley

Date: 07-05-2021

DOI: 10.1111/EVO.14243

University Of Chicago

Location: United States of America

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American Museum Of Natural History

Location: United States of America

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University Of California Davis

Location: United States of America

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Cornell University

Location: United States of America

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Discovery Projects - Grant ID: DP230101261

Start Date: 06-2023

End Date: 05-2026

Amount: $237,980.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP180101783

Start Date: 06-2018

End Date: 11-2022

Amount: $299,944.00

Funder: Australian Research Council