Christopher WheatAssociate Professor
My work focused upon using ecological and evolutionary genomics to investigate adaptation in the wild.
I teach several course, from conservation genetics to evoltion. Please refer to the schedule in BIG.
In my group, research is focused on finding and studying the genetic variation causing performance and fitness variation in natural populations, as well as putting this into an evolutionary context. We use whatever tools we can to address a given quesition, from butterfly nets to genomes.
A selection from Stockholm University publication database
A high-coverage draft genome of the mycalesine butterfly Bicyclus anynana
2017. Reuben W. Nowell (et al.). GigaScience 6 (7)Article
The mycalesine butterfly Bicyclus anynana, the Squinting bush brown, is a model organism in the study of lepidopteran ecology, development, and evolution. Here, we present a draft genome sequence for B. anynana to serve as a genomics resource for current and future studies of this important model species. Seven libraries with insert sizes ranging from 350 bp to 20 kb were constructed using DNA from an inbred female and sequenced using both Illumina and PacBio technology; 128 Gb of raw Illumina data was filtered to 124 Gb and assembled to a final size of 475 Mb (similar to x260 assembly coverage). Contigs were scaffolded using mate-pair, transcriptome, and PacBio data into 10 800 sequences with an N50 of 638 kb (longest scaffold 5 Mb). The genome is comprised of 26% repetitive elements and encodes a total of 22 642 predicted protein-coding genes. Recovery of a BUSCO set of core metazoan genes was almost complete (98%). Overall, these metrics compare well with other recently published lepidopteran genomes. We report a high-quality draft genome sequence for Bicyclus anynana. The genome assembly and annotated gene models are available at LepBase (http://ensembl.lepbase.org/index.html).
Advances in finding Alba
2017. Alyssa Woronik, Christopher W. Wheat. Journal of Evolutionary Biology 30 (1), 26-39Article
Although alternative life-history strategies exist within many populations, very little is known about their genetic basis and mechanistic insight into these traits could greatly advance the understanding of eco-evolutionary dynamics. Many species of butterfly within the genus Colias exhibit a sex-limited wing colour polymorphism, called Alba, which is correlated with an alternative life-history strategy. Here, we have taken the first steps in localizing the region carrying Alba in Colias croceus, a species with no genomic resources, by generating whole genome sequence of a single Alba mother and two sequencing pools, one for her Alba and another for her orange, offspring. These data were used in a bulk-segregant analysis wherein SNPs fulfilling the Mendelian inheritance expectations of Alba were identified. Then, using the conserved synteny in Lepidoptera, the Alba locus was assigned to chromosome 15 in Bombyx mori. We then identified candidate regions within the chromosome by investigating the distribution of Alba SNPs along the chromosome and the difference in nucleotide diversity in exons between the two pools. A region spanning similar to 5.7 Mbp at the 50 end of the chromosome was identified as likely to contain the Alba locus. These insights set the stage for more detailed genomic scans and mapping of the Alba phenotype, and demonstrate an efficient use of genomic resources in a novel species.
Female fecundity variation affects reproducibility of experiments on host plant preference and acceptance in a phytophagous insect
2017. Alexander Schäpers (et al.). Proceedings of the Royal Society of London. Biological Sciences 284 (1849)Article
Reproducibility is a scientific cornerstone. Many recent studies, however, describe a reproducibility crisis and call for assessments of reproducibility across scientific domains. Here, we explore the reproducibility of a classic ecological experiment—that of assessing female host plant preference and acceptance in phytophagous insects, a group in which host specialization is a key driver of diversification. We exposed multiple cohorts of Pieris napi butterflies from the same population to traditional host acceptance and preference tests on three Brassicaceae host species. Whereas the host plant rank order was highly reproducible, the propensity to oviposit on low-ranked hosts varied significantly even among cohorts exposed to similar conditions. Much variation could be attributed to among-cohort variation in female fecundity, a trait strongly correlated both to female size and to the size of the nuptial gift a female receives during mating. Small males provide small spermatophores, and in our experiment small females that mated with small males had a disproportionally low propensity to oviposit on low-ranked hosts. Hence, our results provide empirical support to the theoretical prediction that female host utilization is strongly affected by non-genetic, environmental variation, and that such variation can affect the reproducibility of ecological experiments even under seemingly identical conditions.