A daphniid studying its diet of phytoplankton (water color by Brittany Benson). (A gift from N. Zehrbach.)

My group and I study the mechanisms (e.g. selection, migration) that influence the maintenance of genetic diversity in asexual-sexual species complexes, using the freshwater cladoceran genus, Daphnia, as our primary model organism. My research bridges the fields of population genetics, environmental genomics, and evolutionary ecology. In my lab, a variety of molecular techniques (e.g. microsatellites, DNA sequencing, and Next-Gen genomics) are used to examine the population genetic/genomic structure of aquatic organisms, with most of my work focusing on zooplankton.

We currently have several major projects. The first project with European colleagues has been examining long-term (i.e. decadal) changes in arctic rock-pool and tundra pond population genetic structure, as well as community structure among zooplankton related to climate change.

Sampling rock pools – Churchill, Manitoba, Summer 2007
Sampling tundra ponds; Churchill, Manitoba, Summer 2012. L-R: Dagmar Frisch, Puni Jeyasingh, L.J. Weider

A second major project funded by the U.S. National Science Foundation (NSF) with colleagues at Oklahoma State University, the St. Croix River (MN) Watershed Research Station (and Science Museum of Minnesota), and colleagues in Europe is focusing on the ecological and genetic information held in lake/pond sediment egg banks of freshwater invertebrates, primarily Daphnia.  We employ a variety of “resurrection ecology” techniques spanning the fields of paleolimnology, molecular genetics, ecology (i.e. direct hatching of eggs, selection experiments), and environmental genomics (i.e. Next-Gen sequencing) to examine long-term (i.e. decades, centuries) shifts in population genetic/genomic structure that may be associated with concomitant shifts in environmental factors (e.g. nutrient/eutrophication history).  We aim to look at how shifts in environmental factors may influence long-term temporal genetic heterogeneity in natural populations, and are incorporating “paleogenomic/paleogenetic” approaches.

Preparing the sediment corer; Elk Lake, MN, Summer 2010
Sediment coring – Elk Lake, MN, Summer 2010; L.J. Weider & Ryan O’Grady
Cell culture plates containing Daphnia resting eggs that are being induced to hatch.
Daphnia pulicaria hatchling

A third project, which involves a number of my students, in particular, Emily Kiehnau, has started to examine the influence of the invasive predatory spiny water flea (Bythotrephes longimanus), on the population genetic and community structure of native North American zooplankton communities (primarily focusing on Daphnia) in Canada and the upper Mid-west U.S.A.

Bythotrephes longimanus mural (courtesy of Shelley Arnott)