Biology subjects

Rosser, N.

Publications and source records attributed to Rosser, N..

3 recordsLinked to original sources

bioRxiv2022

Cycad phylogeny predicts host plant use of Eumaeus butterflies

Eumaeus butterflies are obligate herbivores of Zamia, the most diverse neotropical genus of cycads. Eumaeus-Zamia interactions have been mainly characterized for species distributed in North and Central America. However, host plant use by the southern Eumaeus clade remains largely unknown, precluding a comprehensive study of co-evolution between the genera. Here, we combine fieldwork with museum and literature surveys to expand herbivory records for Eumaeus from 21 to 38 Zamia species. We inferred a time-calibrated phylogeny of Eumaeus to test for distinct macroevolutionary scenarios of host plant conservatism and co-evolution. We found remarkable coincidence between Eumaeus and Zamia diversification, with the butterfly stem group diverging at the same time as the most recent radiation of Zamia in the Miocene. Cophylogenetic reconciliation analyses show a strong cophylogenetic signal between cycads and their butterfly herbivores. Bipartite model-based approaches indicate that this is because closely related Zamia species are used by the same Eumaeus species, suggesting host plant resource tracking by the butterfly herbivores. Our results highlight a case of tight evolution between Eumaeus butterflies and cycads, pointing to the generality of correlated evolution and phylogenetic tracking in plant-herbivore interactions across seed plants.

evolutionary biology↗

bioRxiv2022

Diverse genetic architectures on the Z chromosome underlie the two rules of speciation in Papilio butterfly hybrids

The fitness of animal hybrids follows two empirical rules: hybrids of the heterogametic sex aremore unfit (Haldanes Rule), and the sex chromosome is disproportionately involved in incompatibility (the large-X/Z effect). Whether these rules result from genetic mechanisms shared across taxa remains unknown, and existing explanations rarely consider female heterogametic taxa such as butterflies. Here, we investigate hybrid incompatibilities in Papilio and Heliconius butterflies, and show that defects coincide with unbalanced introgression between the Z chromosome and its genetic background. This polygenic mechanism predicts both rules because introgressed ancestry on the Z chromosome is more skewed in females, and is more variable than on all autosomes. Therefore, the explanation for both rules in butterflies shares little similarity with prevailing theories relying on dominance.

evolutionary biology↗

bioRxiv2021

Complex basis of hybrid female sterility and Haldane's rule in Heliconius butterflies: Z-linkage and epistasis

Hybrids between diverging populations are often sterile or inviable. Hybrid unfitness usually evolves first in the heterogametic sex - a pattern known as Haldanes rule. The genetics of Haldanes Rule have been extensively studied in species where the male is the heterogametic (XX/XY) sex, but its basis in taxa where the female is heterogametic (ZW/ZZ), such as Lepidoptera and birds, is largely unknown. Here, we analyse a new case of female hybrid sterility between geographic subspecies of Heliconius pardalinus. The two subspecies mate freely in captivity, but female F1 hybrids in both directions of cross are sterile. Sterility is due to arrested development of oocytes after they become differentiated from nurse cells, but before yolk deposition. We backcrossed fertile male F1 hybrids to parental females, and mapped quantitative trait loci (QTLs) for female sterility. We also identified genes differentially expressed in the ovary, and as a function of oocyte development. The Z chromosome has a major effect, similar to the "large X effect" in Drosophila, with strong epistatic interactions between loci at either end of the Z chromosome, and between the Z chromosome and autosomal loci on chromosomes 8 and 20. Among loci differentially expressed between females with arrested vs. non-arrested ovary development, we identified six candidate genes known also from Drosophila melanogaster and Parage aegeria oogenesis. This study is the first to characterize hybrid sterility using genome mapping in the Lepidoptera. We demonstrate that sterility is produced by multiple complex epistastic interactions often involving the sex chromosome, as predicted by the dominance theory of Haldanes Rule.

evolutionary biology↗