Driving factors and the persistence of small populations
For many species, the future is abundantly clear. Due to anthropogenic disturbances, (i) their populations will have to exist in smaller, isolated habitats; (ii) their dispersal (and hence gene flow) will be more restricted, and (iii) they will live at depressed abundances.
What is less clear – a key aim of our lab’s research program – is which populations will adapt to these changes. Will the classic genetic effects of being small and isolated translate into extinction? Or does demographic and environmental stochasticity usually ‘knock off’ populations before genetic effects even play a major role? And if extinction does not occur, what are the main drivers that allow populations to adapt to environmental change? How much environmental change can populations withstand and still persist? Will sufficient adaptation occur to retain the services that populations of many species deliver to humankind? Outside of laboratory research on microbes and fruit flies, there is remarkably little empirical research that has investigated these questions in integration.
We are investigating how multiple factors influence adaptation to environmental change using a unique, vertebrate model: a series of isolated brook trout populations at Cape Race, Newfoundland, Canada.
Why are Cape Race trout populations an excellent system to study how vertebrate species adapt to environmental change?
Well, besides being a beautiful place to conduct field research……..
1) They can be easily demarcated with genetic tools, and population isolation can be confirmed (this is actually quite difficult in many taxa/instances)
2) They inhabit small streams and hence can be comprehensively sampled, both in the field directly (habitat, population size, movement, life stages etc.), for population genetics/genomics studies, and for study in a wetlab setting (common garden experimentation on their quantitative genetics and phenotypic plasticity)
3) They vary in abundance by four orders of magnitude (10s to 10000s), and three orders of magnitude in effective population size (10s to 1000s)
4) They originate from a common ancestor and became isolated abruptly after the last deglaciation, i.e. their evolutionary history can be feasibly teased apart.
5) They are essentially pristine; fish species – especially salmonid fishes – have a history of being transplanted/stocked everywhere, but not here, probably because the small size of Cape Race trout and the relative remoteness of the populations has not resulted in anthropogenic disturbance.
6) Brook trout are a member of one of the world’s most socio-economically important fish families, salmonids (salmon, trout, charr); research results on Cape Race trout have a direct bearing on conservation and management strategies/considerations for these species.
Associated research papers (*supervised or co-supervised students):
*Wells ZRR (MSc), L McDonnell, L Chapman, DJ Fraser (2016) Limited variability in upper thermal tolerance among pure and hybrid populations of a cold water fish. Conservation Physiology, in press.
*Bernos TA (MSc), DJ Fraser (2016) Spatiotemporal relationship between adult census size and genetic population size across a wide population size gradient. Molecular Ecology 25: 4472-4487. PDF
*Wood JLA (PhD), MC Yates (PhD)*, DJ Fraser (2016) Are selection and heritability related to population size in nature? Meta-analysis and conservation implications. Evolutionary Applications 9: 640-657. PDF
*Wood JLA (PhD), D Tezel (BSc)*, D Joyal (BSc)*, DJ Fraser (2015) Population size is weakly associated with quantitative genetic variation and trait differentiation in a stream fish. Evolution 69: 2303-2318. PDF
*Wood JLA (PhD), DJ Fraser (2015) Similar plastic responses to elevated temperature among different-sized brook trout populations. Ecology 96: 1010 – 1019. PDF
Fraser DJ, PV Debes (Postdoc)*, L Bernatchez, JA Hutchings (2014) Population size, habitat fragmentation, and the nature of adaptive variation in a stream fish. Proceedings of the Royal Society of London Biological Sciences 281:20140370. PDF
*Yates MC (PhD), DJ Fraser (2014) Does source population size affect performance in new environments? Evolutionary Applications 7: 871 – 882. PDF
*Wood JLA (PhD), S Belmar-Lucero (MSc)*, JA Hutchings, DJ Fraser (2014) Relationship of habitat variability to population size in a stream fish. Ecological Applications 24: 1085-1100. PDF
*Belmar-Lucero S (MSc), JLA Wood* (PhD), S Scott* (BSc), AB Harbicht* (MSc), JA Hutchings, DJ Fraser (2012) Concurrent habitat and life history influences on effective/census population ratios in stream-dwelling trout. Ecology and Evolution 2: 562-573. PDF