Upsetting the balance of resource allocation (Anderson et al. 2018)

How do organisms allocate resources to different aspects of life and what are the consequences of differences in this allocation? To explore these questions at both genetic and phenotypic levels I generated a genetically heterogeneous population of the fungus Neurospora crassa which contains genes from 20 naturally isolated strains and performed selection experiments to bias resource allocation toward reproduction or growth. I used RADseq to genotype the parental lines, individuals from the heterogeneous population, and the evolved lines. I have also measured growth rate and spore production in these individuals in two conditions. Using this massive data set, I will determine whether biasing resource allocation toward growth or reproduction influences investment in the other and identify regions of the genome associated with the response to selection (population genomic comparisons between ancestral population and evolved lines). In addition to addressing important questions in life history evolution, this study represents a new approach for experimental study using Neurospora, which has previously been largely limited to studies of single strains and genetic mutants.

Sex determination, sex chromosomes and sexually selected traits in fishes (Anderson et al. 2012, Wilson et al. 2014, Chalopin et al. 2015, Feron et al. 2020, Schartl et al. 2020)

The master sex determination genes in fishes are highly variable between species and even between populations. Thus to date, the master sex determining genes are known in only ~ 12 species, strongly limiting our ability to study sex determination processes in early development in key vertebrate models and hindering our efforts to manipulate sex in key aquaculture species. Using genome wide polymorphism data (RADseq) we have identified the sex determining region in the zebrafish Danio rerio and determined that this sex determinant has been lost from the domesticated strains of zebrafish typically used for all zebrafish research. We are currently applying this same approach (RAD-sex) to identify sex determination loci in an additional 30 species of fish from across the fish phylogeny.

We are also using RADseq and information about genome content to study the architecture and evolution of sex chromosomes in fish. To date, we have identified a sex chromosome in the zebrafish, and characterized transposable elements in several species.

Thermal preference might not optimize fitness (Anderson et al. 2007, 2011)

Using a robust experimental system, in which I could measure reproductive fitness, rather than fitness proxies, and thermal preference I showed that preference-fitness relationships are strain and fitness metric specific in C. elegans—effectively upsetting a central premise of this field which predicts that organisms will choose temperatures that maximize fitness. This study is important in the context of climate change and our understanding of how much organismal behavior is likely to/can compensate for changes in temperature.

Early reproduction can be decoupled from lifespan (Anderson, Reynolds et al. 2011)

Based on theories of life history evolution and the evolution of aging, we would predict that early reproduction trades-off with lifespan. After evolving heterogeneous C. elegans populations under conditions favoring early reproduction, reproductive output on the first day of sexual maturity tripled (and did trade-off with late reproduction), but we found no consistent corresponding decrease in lifespan. We conclude that although trade-offs between reproduction and lifespan have been previously observed the genetic constraint is not absolute—that longevity and early fecundity can be decoupled.

High diversity without sex? (Anderson et al. 2006, Anderson and Shearer 2011)

Aquatic fungi are fundamentally important mediators of nutrient spiraling and energy flow in rivers. A large number of these fungi are only known in an asexual form, leaving open the questions of whether sexual forms exist and how predominant or exclusive asexual reproduction influences population structure. I sampled populations of one species of aquatic fungus over 2 years from 7 sites in 3 rivers, finding that nearly every individual sampled from each site and time was genetically unique and population structure was only observed at large spatial scales. These findings are remarkable given that no clear evidence of sexual reproduction was found and there is no know mechanism for dispersal between rivers.