#  Mallet Group Lab | Home 

 



##  Mallet Group 

James Mallet and [co-workers](/group "Jim Mallet group") study evolution, hybridization, and speciation - mainly in butterflies. Methods range from collecting trips in dugouts, field experiments in the Amazon rainforest, population genetic inferences about selection and gene flow, to genomics.



 

 

  ![Heliconius erato butterflies (above) and H. melpomene butterflies (below)](/sites/g/files/omnuum6606/files/2026-06/butterflies.png)

 



 

 Heliconius erato (above), and H. melpomene (below), a pair of Müllerian co-mimics from different sites in Ecuador and Northern Peru. Each species gains protection from the other's unpalatability. Withinany site, the two species are excellent co-mimics, but major geographic differences in colour pattern have evolved within each species. This geographic diversity is extraordinary by temperate zone standards: the region (about 600km x 300km) of the Andean foothills from which all these forms within each species can be found is less extensive than NewEngland or Great Britain.



   

 

##  Research 

 



  [### Genomics and Speciation

 ](/gemonics)The diversity of life on our planet is generated by the process of speciation, the splitting of a population into two divergent groups that can coexist in a state of nature.



 

   ![heliconius melpomene cythera mashpi](/sites/g/files/omnuum6606/files/styles/hwp_16_9__480x270/public/2026-06/heliconius%20melpomene%20cythera%20mashpi.jpg?itok=UBrH_Lli) 

 

 

 

  [### Natural selection, mimicry and speciation

 ](/natural-selection)Heliconius are famous for the extraordinary diversity of colour patterns within and between species.



 

   ![Heliconius erato cyrbia Mashpi](/sites/g/files/omnuum6606/files/styles/hwp_16_9__480x270/public/2026-06/Heliconius%20erato%20cyrbia%20Mashpi.jpg?itok=MWK-QGYN) 

 

 

 

  [### Hybridization and introgression

 ](/hybrids)Many species hybridize with other species, and this can lead to wholesale transfer of variation important in adaptive evolution.



 

   ![melpomene numata hybridization](/sites/g/files/omnuum6606/files/styles/hwp_16_9__480x270/public/2026-06/DSC02155%20melpomene%20numata%20hybridization.JPG?itok=ErWNHWBz) 

 

 

 

  [### Species concepts and the Taxome Project

 ](/species)The newer understanding we have reached about the genomic nature of species and hybridization is leading to a re-examination of what we mean by the term "species."



 

   ![heliconius telesiphe neild ](/sites/g/files/omnuum6606/files/styles/hwp_16_9__480x270/public/2026-06/heliconius%20telesiphe%20neild%202011%20Ecuador%20IMG_3078_resize.JPG?itok=m3elMcGq) 

 

 

 

  [### History of science

 ](/history-science)Interest in hybridization and revised species concepts led to a fascination with why others in the past had got it so wrong (in my opinion).



 

   ![Prof. Muller](/sites/g/files/omnuum6606/files/styles/hwp_16_9__480x270/public/2026-06/Muller91%20orig.jpg?h=54f5a20f&itok=GpCslnLF) 

 

 

 

  

 

 

 

 

New Paper

### Hybrid speciation in the Amazon 

 

Rosser, N., Seixas, F., et al. 2024. Hybrid speciation driven by multilocus introgression of ecological traits. *Nature* 628:811-817.



 [ Read the article in Nature arrow\_circle\_right ](https://www.nature.com/articles/s41586-024-07263-w) 

 



      ![Heliconius butterflies in the Amazon](/sites/g/files/omnuum6606/files/styles/hwp_1_1__480x480/public/2026-06/AdobeStock_516539643.jpeg?itok=zSNnoxpq)