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    Heliconius

    I am often asked for general reviews and reference material on Heliconius. Here are some useful starters:

     

    Non-specialist articles

    • Crane J. (1957): Keeping house for tropical butterflies. National Geographic Magazine 112(2):193-217.
    • D'Abrera, B (1984): Butterflies of the Neotropical region. Vol. Part II. Danaidae, Ithomiidae,...
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    Keightley, P. D., Pinharanda, A., Ness, R. W., Simpson, F., Dasmahapatra, K. K., Mallet, J., Davey, J. W., et al. (2015). Estimation of the spontaneous mutation rate in Heliconius melpomene. Molecular Biology and Evolution , 32, 239-43. Publisher's VersionAbstract
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    We estimated the spontaneous mutation rate in Heliconius melpomene by genome sequencing of a pair of parents and 30 of their offspring, based on the ratio of number of de novo heterozygotes to the number of callable site-individuals. We detected nine new mutations, each one affecting a single site in a single offspring. This yields an estimated mutation rate of 2.9 x 10(-9) (95% confidence interval, 1.3 x 10(-9)-5.5 x 10(-9)), which is similar to recent estimates in Drosophila melanogaster, the only other insect species in which the mutation rate has been directly estimated. We infer that recent effective population size of H. melpomene is about 2 million, a substantially lower value than its census size, suggesting a role for natural selection reducing diversity. We estimate that H. melpomene diverged from its Mullerian comimic H. erato about 6 Ma, a somewhat later date than estimates based on a local molecular clock.

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    Kozak, K. M., Wahlberg, N., Neild, A. F., Dasmahapatra, K. K., Mallet, J., & Jiggins, C. D. (2015). Multilocus species trees show the recent adaptive radiation of the mimetic Heliconius butterflies. Systematic Biology , 64, 505-24. Publisher's VersionAbstract
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    Mullerian mimicry among Neotropical Heliconiini butterflies is an excellent example of natural selection, associated with the diversification of a large continental-scale radiation. Some of the processes driving the evolution of mimicry rings are likely to generate incongruent phylogenetic signals across the assemblage, and thus pose a challenge for systematics. We use a data set of 22 mitochondrial and nuclear markers from 92% of species in the tribe, obtained by Sanger sequencing and de novo assembly of short read data, to re-examine the phylogeny of Heliconiini with both supermatrix and multispecies coalescent approaches, characterize the patterns of conflicting signal, and compare the performance of various methodological approaches to reflect the heterogeneity across the data. Despite the large extent of reticulate signal and strong conflict between markers, nearly identical topologies are consistently recovered by most of the analyses, although the supermatrix approach failed to reflect the underlying variation in the history of individual loci. However, the supermatrix represents a useful approximation where multiple rare species represented by short sequences can be incorporated easily. The first comprehensive, time-calibrated phylogeny of this group is used to test the hypotheses of a diversification rate increase driven by the dramatic environmental changes in the Neotropics over the past 23 myr, or changes caused by diversity-dependent effects on the rate of diversification. We find that the rate of diversification has increased on the branch leading to the presently most species-rich genus Heliconius, but the change occurred gradually and cannot be unequivocally attributed to a specific environmental driver. Our study provides comprehensive comparison of philosophically distinct species tree reconstruction methods and provides insights into the diversification of an important insect radiation in the most biodiverse region of the planet.

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    Mallet, J. (2015). New genomes clarify mimicry evolution. Nature Genetics , 47, 306-7.Abstract
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    For over 100 years, it has been known that polymorphic mimicry is often switched by simple mendelian factors, yet the physical nature of these loci had escaped characterization. Now, the genome sequences of two swallowtail butterfly (Papilio) species have enabled the precise identification of a locus underlying mimicry, adding to unprecedented recent discoveries in mimicry genetics.

    doi: 10.1038/ng.3260.

    Mallet, J. (2008). Hybridization, ecological races and the nature of species: empirical evidence for the ease of speciation. Philosophical Transactions of the Royal Society B-Biological Sciences , 363, 2971-2986.Abstract
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    Species are generally viewed by evolutionists as 'real' distinct entities in nature, making speciation appear difficult. Charles Darwin had originally promoted a very different uniformitarian view that biological species were continuous with 'varieties' below the level of species and became distinguishable from them only when divergent natural selection led to gaps in the distribution of morphology. This Darwinian view on species came under immediate attack, and the consensus among evolutionary biologists today appears to side more with the ideas of Ernst Mayr and Theodosius Dobzhansky, who argued 70 years ago that Darwin was wrong about species. Here, I show how recent genetic studies of supposedly well-behaved animals, such as insects and vertebrates, including our own species, have supported the existence of the Darwinian continuum between varieties and species. Below the level of species, there are well-defined ecological races, while above the level of species, hybridization still occurs, and may often lead to introgression and, sometimes, hybrid speciation. This continuum is evident, not only across vast geographical regions, but also locally in sympatry. The existence of this continuum provides good evidence for gradual evolution of species from ecological races and biotypes, to hybridizing species and, ultimately, to species that no longer cross. Continuity between varieties and species not only provides an excellent argument against creationism, but also gives insight into the process of speciation. The lack of a hiatus between species and ecological races suggests that speciation may occur, perhaps frequently, in sympatry, and the abundant intermediate stages suggest that it is happening all around us. Speciation is easy!

    doi: 10.1098/rstb.2008.0081

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