More Like this

1. Transcriptomic analyses during development reveal mechanisms of integument structuring and color production

   https://doi.org/10.1007/s10682-023-10256-2  

   Stuckert, Adam M.; Freeborn, Layla; Howell, Kimberly A.; Yang, Yusan; Nielsen, Rasmus; Richards-Zawacki, Corinne; MacManes, Matthew D. (September 2023, Evolutionary Ecology)

   Abstract Skin coloration and patterning play a key role in animal survival and reproduction. As a result, color phenotypes have generated intense research interest. In aposematic species, color phenotypes can be important in avoiding predation and in mate choice. However, we still know little about the underlying genetic mechanisms of color production, particularly outside of a few model organisms. Here we seek to understand the genetic mechanisms underlying the production of different colors and how these undergo shifting expression patterns throughout development. To answer this, we examine gene expression of two different color patches(yellow and green) in a developmental time series from young tadpoles through adults in the poison frogOophaga pumilio.We identified six genes that were differentially expressed between color patches in every developmental stage (casq1, hand2, myh8, prva, tbx3,andzic1).Of these,hand2, myh8, tbx3,andzic1have either been identified or implicated as important in coloration in other taxa.Casq1andprvabuffer Ca²⁺and are a Ca²⁺transporter, respectively, and may play a role in preventing autotoxicity to pumiliotoxins, which inhibit Ca²⁺-ATPase activity. We identify further candidate genes (e.g.,adh, aldh1a2, asip, lef1, mc1r, tyr, tyrp1, xdh), and identify a suite of hub genes that likely play a key role in integumental reorganization during development (e.g., collagen type I–IV genes, lysyl oxidases) which may also affect coloration via structural organization of chromatophores that contribute to color and pattern. Overall, we identify the putative role of a suite of candidate genes in the production of different color types in a polytypic, aposematic species. 

   more » « less
2. Conspicuous coloration of toxin‐resistant predators implicates additional trophic interactions in a predator–prey arms race

   https://doi.org/10.1111/mec.16772  

   Hague, Michael T. J.; Miller, Lauren E.; Stokes, Amber N.; Feldman, Chris R.; Brodie, Jr, Edmund D.; Brodie, III, Edmund D. (November 2022, Molecular Ecology)

   Abstract Antagonistic coevolution between natural enemies can produce highly exaggerated traits, such as prey toxins and predator resistance. This reciprocal process of adaptation and counter‐adaptation may also open doors to other evolutionary novelties not directly involved in the phenotypic interface of coevolution. We tested the hypothesis that predator–prey coevolution coincided with the evolution of conspicuous coloration on resistant predators that retain prey toxins. In western North America, common garter snakes (Thamnophis sirtalis) have evolved extreme resistance to tetrodotoxin (TTX) in the coevolutionary arms race with their deadly prey, Pacific newts (Tarichaspp.). TTX‐resistant snakes can retain large amounts of ingested TTX, which could serve as a deterrent against the snakes' own predators if TTX toxicity and resistance are coupled with a conspicuous warning signal. We evaluated whether arms race escalation covaries with bright red coloration in snake populations across the geographic mosaic of coevolution. Snake colour variation departs from the neutral expectations of population genetic structure and covaries with escalating clines of newt TTX and snake resistance at two coevolutionary hotspots. In the Pacific Northwest, bright red coloration fits an expected pattern of an aposematic warning to avian predators: TTX‐resistant snakes that consume highly toxic newts also have relatively large, reddish‐orange dorsal blotches. Snake coloration also seems to have evolved with the arms race in California, but overall patterns are less intuitively consistent with aposematism. These results suggest that interactions with additional trophic levels can generate novel traits as a cascading consequence of arms race coevolution across the geographic mosaic. 

   more » « less
3. Identifying the proximal cue(s) for pupal color variation in the bordered patch butterfly, Chlosyne lacinia (Lepidoptera: Nymphalidae)

   https://doi.org/10.1093/aesa/saae026  

   Phelps, Jamie_M; Santiago-Rosario, Luis_Y; Kelly, Morgan_W; Solis, ed., Alma (October 2024, Annals of the Entomological Society of America)

   Abstract Coloration is a multifaceted trait that serves various functions, including predator defense, thermoregulation, and immune response, among others. We investigated pupal color variation in Chlosyne lacinia pupae, focusing on identifying the cue that influences variation in melanization. Through laboratory experiments, we demonstrated that pupae reared on black backgrounds exhibited significantly higher melanization compared to those on white backgrounds. Additionally, black pupae experienced longer developmental periods, suggesting a trade-off between defense and developmental time. Our findings support crypsis as a likely evolutionary driver for increased melanization in response to substrate color. We discuss potential implications for predator avoidance, immune response, and developmental costs associated with melanization. This study provides insights into the adaptive significance of pupal melanization in response to environmental cues, shedding light on the complex interplay between life history traits in butterflies. 

   more » « less
4. Intrasexual competition underlies sexual selection on male breeding coloration in the orangethroat darter, Etheostoma spectabile

   https://doi.org/10.1002/ece3.2136  

   Zhou, Muchu; Fuller, Rebecca C. (April 2016, Ecology and Evolution)

   Abstract Elaborate, sexually dimorphic traits are widely thought to evolve under sexual selection through female preference, male–male competition, or both. The orangethroat darter (Etheostoma spectabile) is a sexually dichromatic fish in which females exhibit no preferences for male size or coloration. We tested whether these traits affect individual reproductive success inE. spectabilewhen multiple males are allowed to freely compete for a female. The quality and quantity of male coloration were associated with greater success in maintaining access to the female and in spawning as the primary male (first male to participate). On the other hand, sneaking behavior showed little correlation with coloration. Male breeding coloration inE. spectabilemay therefore demonstrate how intrasexual competition can be a predominant factor underlying the evolution of male ornaments. 

   more » « less
5. Beclin -mediated Autophagy Drives Dorsal Longitudinal Flight Muscle Histolysis in the Variable Field Cricket, Gryllus lineaticeps

   https://doi.org/10.1093/icb/icae042  

   Diaz, Tomás; Treidel, Lisa_A; Menze, Michael_A; Williams, Caroline_M; Lebenzon, Jacqueline_E (May 2024, Integrative And Comparative Biology)

   Synopsis Flight muscle histolysis is a widespread strategy used by insects to break down functional flight muscle and modulate the energetic costs associated with flight muscle use and maintenance. The variable field cricket, Gryllus lineaticeps, undergoes histolysis during their transition between dispersal flight and reproduction. Despite the importance of histolysis on insect reproduction and fitness, the molecular mechanisms driving this flight muscle breakdown are not well understood. Here, we show that beclin-mediated autophagy, a conserved lysosomal-dependent degradation process, drives breakdown of dorsal longitudinal flight muscle in female flight-capable G. lineaticeps. We found that female G. lineaticeps activate autophagy in their dorsal longitudinal flight muscle (DLM), but to a greater extent than the neighboring dorsoventral flight muscle (DVM) during histolysis. RNA interference knockdown of beclin, a gene that encodes a critical autophagy initiation protein, delayed DLM histolysis, but did not affect DVM histolysis. This suggests that crickets selectively activate autophagy to break down the DLMs, while maintaining DVM function for other fitness-relevant activities such as walking. Overall, we confirmed that autophagy is a critical pathway used to remodel flight muscle cells during flight muscle histolysis, providing novel insights into the mechanisms underlying a major life history transition between dispersal and reproduction. 

   more » « less