EEB Seminar – Dec. 1st

This week EEB welcomes Dr. Amanda Tracey from the Department of Biology, Queens University:

Plant body size: when does it matter?



Identifying functional traits important for fitness is central to the interpretation of the structure and assembly of natural vegetation, and to management goals associated with biodiversity conservation and habitat restoration. Traditional plant competition theory is based on a ’size-advantage’ (SA) hypothesis — i.e. natural selection resulting from strongly contested resources within crowded vegetation generally favours capacity for a relatively large plant body size. In other words, gene transmission into future generations should increase as body size increases. However, smaller species (and smaller resident plants) typically dominate numerically at virtually all scales within vegetation. These patterns have been recently interpreted in terms of a ‘reproductive economy advantage’ (REA); i.e. when resident plants are severely suppressed in size because of intense resource competition, species with a smaller maximum potential body size (MAX) are generally more likely to produce at least some offspring because they tend also to have a smaller minimum reproductive threshold size (MIN). My PhD research has involved empirical investigations of the SA and REA hypotheses within old-field meadows at QUBS. Do bigger species have a greater abundance of seeds in the seed bank? Are they more abundant as resident plants? Are introduced species, under severely crowded conditions, more likely to establish and reproduce if they have a larger body size? Do bigger species contribute more to neighbourhood standing biomass? To explore these and other questions, I have used a combination of multi-season field experiments, greenhouse trials and natural vegetation surveys.

The EEB Seminars run weekly, on Thursdays, in the EEB Lounge of the BioSciences Complex, Room 4338, from 12:30-1:30pm. Light refreshments are served starting at 12:15.

EEB Seminar – Nov. 24th

This week EEB welcomes Dr. Melania Cristescu from McGill University:

From barcoding single individuals to metabarcoding biological communities: Towards understanding and managing invasive species


Estimating biodiversity has been a central undertaking and a major challenge for biologists over the centuries. The DNA-based species identification known as barcoding, firmly transformed the traditional approach to biodiversity science. The field is quickly transitioning from barcoding single individuals to metabarcoding complex communities of organisms. This rapid evolution involves new sequencing technologies, bioinformatics pipelines, computational infrastructure, and experimental designs. All these changes require new, integrative and coordinated approaches to delineate species and interpret biodiversity estimates. In this dynamic genomics landscape, many metabarcoding studies remain insular; biodiversity estimates depend on the particular marker of choice, the quality of the DNA libraries, bioinformatics pipelines, and divergence thresholds implemented. The molecular operational taxonomic units (MOTUs) inferred are not easily recognizable across sites or studies making inferences regarding species distributions or ecology less practical. The research community needs a robust recognition system open to input, validation, and annotation from users. A coordinated advancement of DNA-based species identification that integrates taxonomic information, phylogenetic inferences with barcoding information would facilitate access to almost three centuries of taxonomic knowledge and one decade of building repository barcodes. Many conservation projects are time sensitive, research funding is becoming restricted and informed decisions depend critically on our ability to embrace an integrative approach to biodiversity science. Using metabarcoding approaches calibrated on mock communities, we were able to detect distinct biodiversity signatures in natural zooplankton communities, and to identify non-indigenous species that had not previously been reported.


  • Born in Transilvania, Romania
  • Conducted undergraduate studies at the University of Constanta Romania, at the Black Sea coast. First undergraduate project focused on the invasive ctenophore Mnemiopsis Leidyi.
  • 1999 started PhD at the University of Guelph under the supervision of Paul Hebert. Central research on Speciation Patterns and Processes in Ancient Lakes
  • 2003 started the PostDoc stage at Indiana University with Michael Lynch. Main projects centered on developing Daphnia pulex as a model for ecological genomics.
  • 2006 took my First Faculty position at the Great Lakes Institute for Environmental Research, University of Windsor. Launched the NSERC CREATE training program in Aquatic Ecosystem Health.
  • 2012 Moved to McGill University. Received the CRC chair in Ecological Genomics
  • 2013 Became Co-Editor in Chief for the journal Genome (Canadian Science Publishing).

I have made significant contributions to research in three main areas: 1) the nature and scale of recombination and mutation rate variation across genomes; 2) the genetics of aquatic invasions; and 3) speciation in ancient lakes.

Recent Representative publications:

Chain FJJ, Brown EA, MacIsaac HJ, Cristescu ME (2016) Metabarcoding reveals strong spatial structure and temporal turnover of zooplankton communities among marine and freshwater ports. Diversity and Distributions, 22, 493-504.

Brown EA, Chain FJJ, Zhan A, MacIsaac HJ, Cristescu ME (2016). Early detection of aquatic invaders using metabarcoding reveals a high number of non-indigenous species in Canadian ports, Diversity and Distributions, 22, 1045-1059.

Cristescu ME (2015) Genetic reconstructions of invasion history. Molecular Ecology, 24, 2212-2225.

Flynn JM, Brown EA, Chain FJJ, MacIsaac HJ, Cristescu ME (2015) Towards accurate molecular identification of species in complex environmental samples: testing the performance of sequence filtering and clustering methods. Ecology and Evolution, 5, 2252-2266.

Cristescu ME (2014) From barcoding single individuals to metabarcoding biological communities: towards an integrative approach to the study of global biodiversity. Trends in Ecology and Evolution 29, 566-571.

Xu S, Innes DJ, Lynch M, Cristescu ME (2013) The role of hybridization in the origin and spread of asexuality in Daphnia. Molecular Ecology, 22, 4549-4561.

Zhan A, Hulak M, Syvester F, Huang X, Abisola AA, Abbott CL, Adamowicz SJ, Heath DD, Cristescu ME, MacIsaac HJ (2013) High sensitivity of 454 pyrosequencing for detection of rare species in aquatic communities. Methods in Ecology and Evolution, 4, 558-565.

The EEB Seminars run weekly, on Thursdays, in the EEB Lounge of the BioSciences Complex, Room 4338, from 12:30-1:30pm. Light refreshments are served starting at 12:15.

EEB Seminar – Nov. 17th

This week EEB welcomes Queen’s own Dr. Virginia Walker from the Department of Biology:

Impermafrost; a mini-sabbatical in Alaska


Climate change is leading to warming and the thawing of that strong underpinning of the Arctic landscape, the permafrost. My sabbatical travels around Alaska suggest that ‘impermafrost’ is perhaps more fitting.

The EEB Seminars run weekly, on Thursdays, in the EEB Lounge of the BioSciences Complex, Room 4338, from 12:30-1:30pm. Light refreshments are served starting at 12:15.

EEB Seminar – Nov. 10th

This week EEB welcomes Dr. Tim Johnson, Great Lakes Research Scientist, Ontario Ministry of Natural Resources and Forestry:

Dynamics and Dilemmas within the Lake Ontario Salmonid Community


The fish community of Lake Ontario reflects a mix of native and introduced species that together support a multi-million dollar recreational fishery. Native top predators including lake trout and Atlantic salmon underwent dramatic population declines early in the past century and efforts are underway to rehabilitate these species. However, in the absence of abundant top predators, largely invasive prey fish populations rapidly expanded to nuisance levels. Binational management response included increasing stocking of several species of Pacific salmon which created economically important recreational fisheries. Is native species rehabilitation compatible with viable non-native salmonid fisheries? I combine analyses of fish production with ecological tracers and mass balance models to identify the mechanisms governing the intensity of interaction among the salmonid fishes of Lake Ontario. The talk will combine concepts of population dynamics, foraging theory, bioenergetics, and resource management to convey the complexity inherent in this productive ecosystem.


Tim Johnson is a Great Lakes Research Scientist with the Ontario Ministry of Natural Resources and Forestry, based at the Glenora Fisheries Station in eastern Lake Ontario. Tim holds a Ph.D. in Zoology with a minor in Limnology and Oceanography from the University of Wisconsin – Madison. Tim’s research focus is the structure and efficiency of aquatic food webs, including the effects of aquatic invasive species, climate change, and habitat alteration on growth and production of fishes and other aquatic organisms. Tim has co-authored over 70 peer-reviewed publications largely addressing ecological issues within the Great Lakes basin. Tim is a former president of the International Association for Great Lakes Research, an Associate Editor for the Journal of Great Lakes Research, and represents the Province’s interests on numerous bi-national boards and committees. Tim is adjunct professor in the Department of Biology, and is currently co-advising two MSc students with Shelley Arnott.

The EEB Seminars run weekly, on Thursdays, in the EEB Lounge of the BioSciences Complex, Room 4338, from 12:30-1:30pm. Light refreshments are served starting at 12:15.

EEB Extra! – Tues. Nov. 8th

Special Session: This week EEB welcomes Dr. Dustin Marshall from Monash University.

Variation in selection as a limit to adaptation


Towards explaining why there is so much genetic variation in wild populations, Professor Dustin Marshall uses examples from his work on sessile marine invertebrates, exploring sources variation in selection that promote and maintain variation, also limiting adaptation.

Special Time: Tuesday Nov 8th, in the EEB Lounge of the BioSciences Complex, Room 4338, from 1:30-2:30pm. Light refreshments are served starting at 1:15.

EEB Seminar – 3 November

This week EEB welcomes Adam Jeziorski from the Department of Biology, Queens University:

From “Aquatic Osteoporosis” to the “Jellification of Lakes”: Ecological impacts of lakewater calcium decline on softwater boreal ecosystems


Over the past forty years, marked declines in Ca concentration have been observed in many softwater boreal lakes, and these trends are understood to be a long-term effect of acid deposition. To date, study of the direct ecological impacts of lower lakewater Ca has focused on Ca-rich members of the Cladocera, and a growing body of work suggests that reduced Ca availability can act as a potent stressor with profound consequences for aquatic ecosystems. Recent laboratory analyses and field surveys using varied approaches have provided insight into these consequences, while paleolimnological approaches have provided long-term perspective on the phenomenon. However, many questions remain regarding: (1) ‘baseline’ or ‘pre-impact’ conditions, due to the accelerated leaching of Ca from watershed soils during the acidification period, and (2) the eventual endpoints of the declines due to catchment-specific differences in both leaching rates and the initial size of the Ca pool in watershed soils. Despite these uncertainties, persistent low Ca concentrations are anticipated to impede biological recovery from lake acidification, and ongoing declines will have cascading impacts throughout aquatic ecosystems due to the loss of vulnerable taxa. To better understand how reduced Ca availability will continue to change affected surface waters and how these changes will interact with other environmental stressors will require continued multi-disciplinary investigation.

The EEB Seminars run weekly, on Thursdays, in the EEB Lounge of the BioSciences Complex, Room 4338, from 12:30-1:30pm. Light refreshments are served starting at 12:15.

EEB Seminar – 27 October

This week EEB welcomes Dr. Karen Samis from the Department of Biology, the University of Prince Edward island:

Expansion and introduction beyond geographic range limits


All species have limits to their geographic range, but there are numerous examples of species that have successfully moved beyond historical range limits. In recent decades a growing number of studies have experimentally demonstrated that ecological aspects of climate gradients (latitude, continentality, elevation) are associated with variation in growth and fitness across geographic ranges, but fewer of these studies occur at or beyond range limits. In light of current global ecological threats including climate change and biological invasions, there is a pressing need to refine our ability to predict organismal phenotypic responses at the edge of species’ geographical ranges. In this talk, I will present data from experiments with native and non-native species transplanted at and beyond their geographical range limits in an effort to understand the genetic and ecological factors that limit ranges and enable range expansion.

The EEB Seminars run weekly, on Thursdays, in the EEB Lounge of the BioSciences Complex, Room 4338, from 12:30-1:30pm. Light refreshments are served starting at 12:15.