Faculty Profiles

Sean Mullen

Sean P. Mullen

Assistant Professor of Biology

PhD, Cornell University, 2006
Areas of Interest: Adaptation and speciation; hybrid zones; the evolution of mimicry and wing pattern variation in butterflies; evolutionary genetics; comparative and population genomics; bioinformatics

Current Research

My research focuses on understanding how adaptive phenotypic variation arises and is maintained in natural populations. In particular, I am interested in the link between divergent natural and sexual selection and the origins of barriers to gene exchange between closely-related populations. Hybrid zones are ideal settings to address such questions because they present opportunities to study the effects of gene flow, selection, and recombination in nature and, thus, provide insights into the genetic, behavioral, and phenotypic changes that occur early in speciation.

Although I have studied the origins of adaptive phenotypes in a number of evolutionary systems (predominantly insects), much of my previous work has been aimed at understanding the origins of mimicry and wing pattern variation among hybridizing populations of mimetic and non-mimetic admiral butterflies in the Limenitis arthemis-astyanax species complex. Results of this research suggest that strong natural selection related to mimicry both maintains the current position of the hybrid zone and limits gene flow between these two wing pattern races.

Current research efforts in the lab are directed at characterizing the proximal genetic mechanisms underlying examples of mimetic wing pattern variation in butterflies within a comparative evolutionary framework. Specifically, in collaboration with Marcus Kronfost’s lab at the University of Chicago, we are working to identify the genes responsible for color pattern mimicry across Heliconius, Limenitis, and Papilio butterflies using a novel strategy that utilizes bulk segregant analyses paired with Illumina sequenced RAD tags, fine mapping, BAC contig sequencing, SNP discovery via genome resequencing, and array-based SNP genotyping in natural populations.

Selected Publications

  • Kronforst MK, Kapan DD, Hansen M, Crawford N, Kulathinal R, Mullen SP (2013) Hybridization reveals the genomic architecture of speciation. Cell Reports, In press.
  • The Heliconius Genome Consortium (2012) Butterfly Genome reveals promiscuous exchange of mimicry adaptations among species. Nature 487(7):94-98.
  • Mullen SP, Savage WK, Wahlberg N, Willmott KR (2011) Rapid diversification and not clade age explains high diversity in neotropical Adelpha butterflies. Proc. Roy. Soc. B.  278:1777-1785.
  • Pfennig DW, Mullen SP (2010) Mimics without models: causes and consequences of allopatry in Batesian mimicry. Proceedings of the Royal Society, Series B 277: 2577-85.
  • Savage WK, Mullen SP (2009) Asingle origin of Batesian mimicry among hybridizing populations of admiral butterflies (Limenitis arthemis) rejects an evolutionary reversion to the ancestral phenotype. Proceedings of the Royal Society, Series B 276: 2557-2565.
  • Mullen SP, Dopman EB, Harrison RG (2008) Hybrid zone origins, species boundaries, and the evolution of wing pattern diversity in a polytypic species complex of North American admiral butterflies (Nymphalidae: Limenitis). Evolution 62:1400-141.
  • Mullen SP, Mendelson TC, Schal C, Shaw KL (2007) Rapid evolution of cuticular hydrocarbons in a species radiation of acoustically diverse Hawaiian crickets (Gryllidae: Trigonidiinae: Laupala). Evolution 61(1):223-231.