Question

You are studying black spruce (Picea mariana), which is the most dominant tree species in North American boreal forests, a. Consider climate change predictions for North America. For long-lived species such as black spruce, is phenotypic plasticity or adaptation through natural selection more likely to help this species survive in the future. Briefly explain your answer. 2 pts. You have 3 black spruce field sites that span a range of latitudes in Canada: northern (65°N), mid (60°N), and southern (55°N). There is a latitudinal gradient in growth; trees in the northern most population grow less each year than tress in the south. You can collect seedlings from these field sites and grow them in your greenhouse. Design an experiment to determine if the observed differences in growth are because of adaptation or phenotypic plasticity - be sure to indicate your independent and dependent variables and briefly explain your methods. 2 pts. b.

Answer 1

ANSWER a.---------- The survival of black spruce will depend on the adaptation capacity of populations, which can partially be evaluated by the ecophysiological response of different genetic sources along a climatic gradient. This adaptation capacity results from the compromise between (i) the degree of genetic adaptation of seed sources to their environment of origin and (ii) the phenotypic plasticity of functional trait which can make it possible for transferred seed sources to positively respond to new growing conditions.

However the phenotypic plasticity will help the species to spread across a varied environment and it will settle wherever it shows the best growth.

When such plants change their enviroment they adapt to the resources available in the new environment and change their mode of photosynthesis. The black spruce plant is already widely spread over the regions of north america and all 10 provinces of Canada. Thus it already shows phenotypic plasticity which will help it to survive in future when climatic changes will occur. A few adaptations may also add to the survival of the species

ANSWER b.------------Photosynthetic-related traits are key adaptive and fitness-related functional traits controlling carbon uptake, resources use efficiencies, and relative growth rates. Many studies conducted on different species have recorded among populations phenotypic differentiation for these traits. For instance, leaf nitrogen concentration and respiration rate have been found to increase with latitude and elevation while specific leaf area (SLA) decreases.

The photosynthetic rate can be an independent variable because it is found to be varying at varying latitudes and climates.

The relative contribution of both phenotypic plasticity and genetic variation to this phenotypic divergence has fundamental implications to improve our understanding and prediction of the physiological and growth responses of white spruce populations to climate change.

The assessment of phenotypic variation and adaptive value of functional traits involved in carbon assimilation and resource use efficiencies among seed sources in response to variation in climatic conditions should contribute toward more informed ecophysiological-based methods of matching populations to site conditions under climate change. The assessment of such traits should enable to improve their survival in the greenhouse beyond summary parameters such as growth and yield estimates and thereby, help minimize the risk of establishment failure, and maximize the adaptation potential of transferred seed sources.