Biology subjects

Nylin, S.

Publications and source records attributed to Nylin, S..

9 recordsLinked to original sources

bioRxiv2023

Genome-wide gene birth-death dynamics are associated with diet breadth variation in Lepidoptera

Comparative analyses of gene birth-death dynamics (GBDD) have the potential to reveal gene families that played an important role in the evolution of morphological, behavioral, or physiological variation. Here, we used whole genomes of 30 species of butterflies and moths to identify GBDD among the Lepidoptera that are associated with specialist or generalist feeding strategies. Our work advances this field by using a uniform set of annotated proteins for all genomes, investigating associations while correcting for phylogeny, and assessing all gene familes rather than a priori subsets. We discovered that the sizes of several important gene families (e.g., those associated with pesticide resistance, xenobiotic detoxification, and/or protein digestion) are significantly correlated with diet breadth. We also found 12 gene families showing significant shifts in GBDD at the butterfly (Papilionoidea) crown node, the most notable of which was a family of pheromone receptors that underwent a contraction potentially linked with a shift to visual-based mate recognition. Our findings highlight the importance of uniform annotations, phylogenetic corrections and unbiased gene family analyses in generating a list of candidate genes that warrant further exploration. Significance StatementGene duplications and gene deaths are important for the development of novel traits, but their study is often complicated by methodological issues, such as input data coming from different sources with different biases. Here, we address many of these issues in an analysis of gene duplication and death across 30 species of moths by using standardized, genome-wide input data. Importantly, our analysis uses a model that can correlate gene family sizes with any quantitative trait, while also accounting for relatedness between species. Using this model, we provide novel evolutionary insights by showing that the sizes of several important gene families are correlated with increases or decreases in the number of host plant orders that Lepidoptera eat.

evolutionary biology↗

bioRxiv2022

Evolution of seasonal plasticity in response to climate change differs between life-stages of a butterfly

Climate change alters seasonal environments without altering photoperiod, creating a cue-environment mismatch for organisms that rely on photoperiod as a cue for seasonal plasticity and phenology. Evolution can potentially correct for this mismatch by altering the photoperiodic reaction norm, but often phenology depends on multiple plastic decisions made at different life stages and times of year. We tested whether seasonal plasticity in different life stages evolves independently or in concert under climate change using Pararge aegeria (Speckled wood butterfly). This butterfly uses day length as a cue for life history plasticity in two different life stages: larval development time and pupal diapause. Photoperiodic reaction norms for plasticity in these traits were first measured over 30 years ago for two different Swedish populations. In this study, we replicated historic experiments that measured these reaction norms using the contemporary populations. We found evidence for evolution of the reaction norm for larval development time, but in opposite directions in the two populations. In contrast, we found no evidence for evolution of the reaction norm for pupal diapause. These results show that different life stages can evolve differently in response to climate change and only studying one part of the life cycle will not always be enough to fully understand how climate change impacts phenotypic plasticity and phenology.

evolutionary biology↗

bioRxiv2021

Evolution of butterfly-plant networks over time, as revealed by Bayesian inference of host repertoire

The study of herbivorous insects underpins much of the theory that concerns the evolution of species interactions. In particular, Pieridae butterflies and their host plants have served as a model system for studying evolutionary arms-races. To learn more about the coevolution of these two clades, we reconstructed ancestral ecological networks using stochastic mappings that were generated by a phylogenetic model of host-repertoire evolution. We then measured if, when, and how two ecologically important structural features of the ancestral networks (modularity and nestedness) evolved over time. Our study shows that as pierids gained new hosts and formed new modules, a subset of them retained or recolonized the ancestral host(s), preserving connectivity to the original modules. Together, host-range expansions and recolonizations promoted a phase transition in network structure. Our results demonstrate the power of combining network analysis with Bayesian inference of host-repertoire evolution to understand changes in complex species interactions over time.

ecology↗

bioRxiv2020

Analyzing the neutral and adaptive background of butterfly voltinism reveals structural variation in a core circadian gene

Many insects exhibit geographic variation in voltinism, the number of generations produced per year. This includes high-latitude species in previously glaciated areas, implying divergent selection on life cycle traits during or shortly after recent colonization. Here, we use a whole-genome approach to genetically characterize a set of populations of the butterfly Pararge aegeria that differ in voltinism. We construct a high-quality de novo genome for P. aegeria, and assess genome-wide genetic diversity and differentiation between populations. We then use the inferred phylogeographic relationships as the basis for a scan for loci showing signs of divergent selection associated with voltinism differences. The genic outliers detected include population-specific mutations of circadian loci, most notably a locally fixed 97-amino acid deletion in the circadian gene timeless. Variation in timeless has previously been implicated as underlying variation in life cycle regulation in wild populations in our study species, as well as in other insects. These results add to a growing body of research framing circadian gene variation as a mechanism for generating local adaptation of life cycles.

evolutionary biology↗

bioRxiv2020

The latitudinal diversity gradient in brush-footed butterflies (Nymphalidae): conserved ancestral tropical niche but different continental histories.

The latitudinal diversity gradient (LDG) is arguably one of the most striking patterns in nature. The global increase in species richness toward the tropics across continents and taxonomic groups stimulated the formulation of many hypotheses to explain the underlying mechanisms of this pattern. We evaluated several of these hypotheses to explain spatial diversity patterns in the butterfly family, Nymphalidae, by assessing the contributions of speciation, extinction, and dispersal to the LDG, and also the extent to which these processes differ among regions at the same latitude. We generated a new, time-calibrated phylogeny of Nymphalidae based on 10 gene fragments and containing ca. 2,800 species ([~]45% of extant diversity). Neither speciation nor extinction rate variations consistently explain the LDG among regions because temporal diversification dynamics differ greatly across longitude. For example, we found that Neotropical nymphalid diversity results from low extinction rates, not high speciation rates, and that biotic interchanges with other regions were rare. Southeast Asia was also characterized by a low speciation rate but, unlike the Neotropics, was the main source of dispersal events through time. Our results suggest that global climate change throughout the Cenozoic, particularly during the Eocene-Oligocene transition, combined with the conserved ancestral tropical niches, played a major role in generating the modern LDG of butterflies.

ecology↗

bioRxiv2019

The consequences of surviving infection across the metamorphic boundary: tradeoff insights from RNAseq and life history measures

The broad diversity of insect life has been shaped, in part, by pathogen pressure, yet the influence of injury and infection during critical periods of development is understudied. During development, insects undergo metamorphosis, wherein the organism experiences a dramatic shift in their overall morphology, and physiology. In temperate zones, metamorphosis is often directly followed by a developmental arrest called diapause, for which the insect needs to acquire enough energy reserves before the onset of winter. We investigated the long-term effects of injury and infection using two bacteria in the butterfly Pieris napi, revealing that the negative consequences of bacterial infection carry across the metamorphic boundary. Initial direct effects of infection were weight loss and slower development, as well as an increased mortality at higher infection levels. The detrimental effects were stronger in the gram-positive Micrococcus luteus compared to gram-negative Escherichia coli. Transcriptome-wide differences between the two bacteria were already observed in the gene expression profile of the first 24 hours after infection. Larvae infected with M. luteus showed a strong suppression of all non-immunity related processes, with several types of immune responses being activated. The impact of these transcriptomic changes, a tradeoff between homeostasis and immune response, were visible in the life history data, wherein individuals infected with M. luteus had the highest mortality rate, along with the lowest pupal weight, developmental rate and adult weight of all the treatments. Overall, we find that the cost of infection and wounding in the final larval instar carries over the metamorphic boundary, and is expected to negatively affect their lifetime fitness.

evolutionary biology↗

bioRxiv2019

Geographic variation in hemocyte diversity and phagocytic propensity shows a diffuse genomic signature in the green veined white butterfly

Insects rely on their innate immune system to successfully mediate complex interactions with their internal microbiota, as well as the microbes present in the environment. Given the variation in microbes across habitats, the challenges to respond to them is likely to result in local adaptation in the immune system. Here we focus upon phagocytosis, a mechanism by which pathogens and foreign particles are engulfed in order to be contained, killed and processed for antigen presentation. We investigated the phenotypic and genetic variation related to phagocytosis, in two allopatric populations of the butterfly Pieris napi. We found that the populations differ in their hemocyte composition, and overall phagocytic capability, driven by the increased phagocytic propensity of each cell type. However, no evidence for divergence in phagocytosis-related genes was observed, though an enrichment of genes involved in glutamine metabolism was found, which have recently been linked to immune cell differentiation in mammals.

evolutionary biology↗

bioRxiv2019

Bayesian inference of ancestral host-parasite interactions under a phylogenetic model of host repertoire evolution

Intimate ecological interactions, such as those between parasites and their hosts, may persist over long time spans, coupling the evolutionary histories of the lineages involved. Most methods that reconstruct the coevolutionary history of such associations make the simplifying assumption that parasites have a single host. Many methods also focus on congruence between host and parasite phylogenies, using cospeciation as the null model. However, there is an increasing body of evidence suggesting that the host ranges of parasites are more complex: that host ranges often include more than one host and evolve via gains and losses of hosts rather than through cospeciation alone. Here, we develop a Bayesian approach for inferring coevolutionary history based on a model accommodating these complexities. Specifically, a parasite is assumed to have a host repertoire, which includes both potential hosts and one or more actual hosts. Over time, potential hosts can be added or lost, and potential hosts can develop into actual hosts or vice versa. Thus, host colonization is modeled as a two-step process, which may potentially be influenced by host relatedness or host traits. We first explore the statistical behavior of our model by simulating evolution of host-parasite interactions under a range of parameters. We then use our approach, implemented in the program RevBayes, to infer the coevolutionary history between 34 Nymphalini butterfly species and 25 angiosperm families.

evolutionary biology↗

bioRxiv2017

A butterfly chromonome reveals selection dynamics during extensive and cryptic chromosomal reshuffling

Chromosome evolution, an important component of mico- and macroevolutionary dynamics 1-5, presents an enigma in the mega-diverse Lepidoptera6. While most species exhibit constrained chromosome evolution, with nearly identical haploid chromosome counts and chromosome-level shared gene content and collinearity among species despite more than 140 Million years of divergence7, a small fraction of species independently exhibit dramatic changes in chromosomal count due to extensive fission and fusion events that are facilitated by their holocentric chromosomes7-9. Here we address this enigma of simultaneous conservation and dynamism in chromosome evolution in our analysis of the chromonome (chromosome level assembly10) of the green-veined white butterfly, Pieris napi (Pieridae, Linnaeus, 1758). We report an unprecedented reorganization of the standard Lepidopteran chromosome structure via more than 90 fission and fusion events that are cryptic at other scales, as the haploid chromosome number is identical to related genera and gene collinearity within the large rearranged segments matches other Lepidoptera. Furthermore, these rearranged segments are significantly enriched for clusters of functionally related genes and the maintenance of ancient telomeric ends. These results suggest an unexpected role for selection in shaping chromosomal evolution when the structural constraints of monocentricq chromosomes are relaxed.

evolutionary biology↗