Biology subjects

Brady, N. K.

Publications and source records attributed to Brady, N. K..

3 recordsLinked to original sources

bioRxiv2024

Synchronous seasonal plasticity in colouration, behaviour, and visual gene expression in a wild butterfly population

Phenotypic plasticity allows many animals to quickly respond to seasonal changes in their environment. Seasonal changes to physiological systems, such as sensory systems, may explain other more obvious changes in behaviour, often working synergistically with changes in morphology. Here we investigate if there are covarying seasonal changes to morphology, behaviour, and the visual system in the seasonally plastic butterfly Junonia coenia. To describe when seasonal wing patterns occur at our field sites in the central United States and for analysis of gene expression in eye tissue, we collected animals throughout the summer and fall in 2018, 2019, 2020, and 2021. For the first three years we also visited field sites to observe behaviour during focal watches and point counts throughout the flight period. We found that more J. coenia exhibit seasonal dark wing patterns in September and October compared to butterflies collected in previous months. This change in wing pattern correlates to an increase in basking behaviour. Eye tissues of dark fall animals and lighter summer animals exhibit different patterns of gene expression, including clock genes and genes involved in eye pigment synthesis. Subsequent analysis of monthly variation in opsin gene expression in eye tissues confirmed that opsin genes are not differentially expressed throughout the year, though period gene expression is higher in the fall, and females have higher blue opsin gene expression than males. This concurrent seasonal shift in colouration, behaviour, and underlying visual physiology indicates that J. coenia undergoes a complex shift in phenotype that encompasses more than simple changes to thermoregulation.

animal behavior and cognition↗

bioRxiv2024

mirror determines the far posterior domain in butterfly wings

Insect wings, a key innovation that contributed to the explosive diversification of insects, are recognized for their remarkable variation and many splendid adaptations. Classical morphological work subdivides insect wings into several distinct domains along the antero-posterior (AP) axis, each of which can evolve relatively independently to produce the myriad forms we see in nature. Important insights into AP subdivision of insect wings comes from work in Drosophila melanogaster, however they do not fully explain the diversity of AP domains observed across broad winged insects. Here we show that the transcription factor mirror acts as a selector gene to differentiate a far posterior domain in the butterfly wing, classically defined as the vannus, and has effects on wing shape, scale morphology, and color pattern. Our results support models of how selector genes may facilitate evolutionarily individuation of distinct AP domains in insect wings outside of Drosophila, and suggest that the D. melanogaster wing blade has been reduced to represent only a portion of the archetypal insect wing.

evolutionary biology↗

bioRxiv2024

The ivory lncRNA regulates seasonal color patterns in buckeye butterflies

Long non-coding RNAs (lncRNAs) are transcribed elements increasingly recognized for their roles in regulating gene expression. Thus far, however, we have little understanding of how lncRNAs contribute to evolution and adaptation. Here we show that a conserved lncRNA, ivory, is an important color patterning gene in the buckeye butterfly Junonia coenia. ivory overlaps with cortex, a locus linked to multiple cases of crypsis and mimicry in Lepidoptera. Along with a companion paper by Livraghi et. al., we argue that ivory, not cortex, is the color pattern gene of interest at this locus. In J. coenia a cluster of cis-regulatory elements (CREs) in the first intron of ivory are genetically associated with natural variation in seasonal color pattern plasticity, and targeted deletions of these CREs phenocopy seasonal phenotypes. Deletions of different ivory CREs produce other distinct phenotypes as well, including loss of melanic eyespot rings, and positive and negative changes in overall wing pigmentation. We show that the color pattern transcription factors Spineless, Bric-a-brac, and Ftz-f1 bind to the ivory promoter during wing pattern development, suggesting that they directly regulate ivory. This case study demonstrates how cis-regulation of a single non-coding RNA can exert diverse and nuanced effects on the evolution and development of color patterns, including modulating seasonally plastic color patterns. SignificanceThe genomic locus hosting the cortex gene has been linked to numerous cases of color pattern adaptation in moths and butterflies, including crypsis, mimicry, and seasonal polyphenism. Here we show in buckeye butterflies that the actual color pattern gene at the cortex locus is an evolutionarily conserved long non-coding RNA (lncRNA), dubbed ivory, that overlaps with cortex. Compared with other wing pattern genes, ivory stands out because of the highly nuanced, quantitative changes in pigmentation that can be achieved by manipulating adjacent cis-regulatory sequences. This study highlights how lncRNAs can be important factors underlying morphological evolution, and emphasizes the importance of considering non-coding transcripts in comparative genomics.

genetics↗