Revealing paraphyly and placement of extinct species within Epischura (Copepoda: Calanoida) using molecular data and quantitative morphometrics.

Epischura (Calanoida: Temoridae) is a Holarctic group of copepods serving important ecological roles, but it is difficult to study because of small range sizes of individual species and widespread distribution of the genus. This genus includes Tertiary relicts, some endemic to single, isolated lakes and can play major roles in unique ecosystems like Lakes Baikal and Tahoe. We present the first molecular and morphological analysis of Epischura that reveals their spatio-temporal evolutionary history. Morphological measurements of mandibles and genetics estimated phylogenetic relationships among all species represented in Epischura, including E. massachusettsensis, whose extinction status is of concern. Analyses used three gene regions for six previously unsequenced species to infer highly-resolved and well-supported phylogenies confirming a split between Siberian and North American species. Previously published age estimates and sequence data from broad taxonomic sampling of calanoid copepods estimated divergence times between the two Epischura groups. Divergence time estimates for Epischura were consistent with earlier molecular clock estimates and late-Miocene cooling events. Additionally, we provide the first taxonomically broad estimates of divergence times within Calanoida. The paraphyletic nature of the genus Epischura (and the family Temoridae) is apparent and requires the resurrection of the genus Epischurella (Smirnov, 1936) to describe the Siberian species.

Temperature gradient affects differentiation of gene expression and SNP allele frequencies in the dominant Lake Baikal zooplankton species.

Local adaptation and phenotypic plasticity are main mechanisms of organisms' resilience in changing environments. Both are affected by gene flow and are expected to be weak in zooplankton populations inhabiting large continuous water bodies and strongly affected by currents. Lake Baikal, the deepest and one of the coldest lakes on Earth, experienced epilimnion temperature increase during the last 100 years, exposing Baikal's zooplankton to novel selective pressures. We obtained a partial transcriptome of Epischura baikalensis (Copepoda: Calanoida), the dominant component of Baikal's zooplankton, and estimated SNP allele frequencies and transcript abundances in samples from regions of Baikal that differ in multiyear average surface temperatures. The strongest signal in both SNP and transcript abundance differentiation is the SW-NE gradient along the 600+ km long axis of the lake, suggesting isolation by distance. SNP differentiation is stronger for nonsynonymous than synonymous SNPs and is paralleled by differential survival during a laboratory exposure to increased temperature, indicating directional selection operating on the temperature gradient. Transcript abundance, generally collinear with the SNP differentiation, shows samples from the warmest, less deep location clustering together with the southernmost samples. Differential expression is more frequent among transcripts orthologous to candidate thermal response genes previously identified in model arthropods, including genes encoding cytoskeleton proteins, heat-shock proteins, proteases, enzymes of central energy metabolism, lipid and antioxidant pathways. We conclude that the pivotal endemic zooplankton species in Lake Baikal exists under temperature-mediated selection and possesses both genetic variation and plasticity to respond to novel temperature-related environmental pressures.

Ecology under lake ice.

Winter conditions are rapidly changing in temperate ecosystems, particularly for those that experience periods of snow and ice cover. Relatively little is known of winter ecology in these systems, due to a historical research focus on summer 'growing seasons'. We executed the first global quantitative synthesis on under-ice lake ecology, including 36 abiotic and biotic variables from 42 research groups and 101 lakes, examining seasonal differences and connections as well as how seasonal differences vary with geophysical factors. Plankton were more abundant under ice than expected; mean winter values were 43.2% of summer values for chlorophyll a, 15.8% of summer phytoplankton biovolume and 25.3% of summer zooplankton density. Dissolved nitrogen concentrations were typically higher during winter, and these differences were exaggerated in smaller lakes. Lake size also influenced winter-summer patterns for dissolved organic carbon (DOC), with higher winter DOC in smaller lakes. At coarse levels of taxonomic aggregation, phytoplankton and zooplankton community composition showed few systematic differences between seasons, although literature suggests that seasonal differences are frequently lake-specific, species-specific, or occur at the level of functional group. Within the subset of lakes that had longer time series, winter influenced the subsequent summer for some nutrient variables and zooplankton biomass.

Course-based prefaculty training program introduces instructional methods, increases instructor self-efficacy, and promotes professional development.

Graduate student and postdoctoral teaching assistants receive highly variable preparation for instructional methods because providing such training is often expensive. Therefore, we conducted an intensive, pedagogical boot camp followed by classroom observations, structured professional development discussions about leveraging the experience on the job market, individual exit interviews, and a letter of recommendation. Our data show the participants implemented new pedagogical techniques in their classrooms, showed increased self-efficacy, and reported appreciation for the training experience. Using a clustering analysis of instructional methods, most participants' classrooms were characterized as peer-led collaborative work as opposed to more traditional instructor-led pedagogies. We believe that this low-cost, prefaculty training leads to demonstrable short-term outcomes and is a viable option for institutions with limited resources or personnel.