Mari Roberts BSC3052 Sec 3 October 5 2012 Orchid PVA Computer Lab Briefly describe how you might collect the data you need to build your model decide how many stages to include seeds seedlings vegetative dormant flowering understand the species calculate transitions 14 total fraction surviving but not growing dormant fraction surviving and growing number of seeds fruit year make a population projection matrix F5 1 2 21618 0 53 13 749 048 S1 0 40 G35 0 141 Year 1990 1991 Plants 74 0 1991 1992 1992 1993 1993 1994 54 154 361 10 53 12 0 0 185 0 344 0 033 Flowering Probability Average 160 75 18 75 0 141 G35 0 40 0 0015 0 0 0 0 0 0 0 0 0 0 0 0301 0 0 0 0099 0 0 0 0 0 0 0 0 0 5783 0 2806 0 141 0 1015 0 0299 13749 10 0 0 10 0 0815 0 2106 10 0 5968 10 0 2025 10 Mari Roberts BSC3052 Sec 3 October 5 2012 Determine Current Status Is the population growing or shrinking in the first generation shrinking To support your conclusion provide the lambda for the first year current lambda 0 79 Is the population at its stable stage distribution in the first generation How can you tell Choose and provide an appropriate graph to support your answer Yes The stage structure proportion of t in stage x of population changes over time stabilizes at the first generation figure below Figure Nx ENx vs t for stage 1 Can you always infer the long term behavior of a population based on a few years of calculating lambda as Nt 1 Nt Why or why not No this will only be constant if the population is at a stable stage distribution Lambda is constant as long as P stays the same The count based model treats all individuals the same The stage based model in cludes life stages which are useful to infer long term behavior of a population Nt PNt 1 Determine Future Status What will this population do in the long term future To support your conclusion provide the long term average lambda lambda 0 963 The population will decline in the long term future by 3 7 Choose a quasi extinction threshold minimum population size you will tolerate If the population will go quasi extinct roughly how long will that take Provide a graph of total number in the population over time long enough to show extinction if it is expected to support your conclusion Hint you can overlay a grid on your graphs using the options menu at the top of the graph page About 250 generations for the population to reach zero Mari Roberts BSC3052 Sec 3 October 5 2012 Determine which life stages should be targeted for management Calculate and report the survival elasticity for each life stage For each stage in turn change all ele ments except fecundity by 5 each and calculate the elasticity Seeds 0 134 Seedlings 0 0834 Vegetative 0 0415 Dormant 0 00374 Flowering 0 0623 Also calculate and report the elasticity for fecundity 0 187 Which stage s should be the focus of management Seed viability should be the focus of management Increasing the amount of vi able seeds by 5 increased the value of lambda to 0 97 This also had the high est elasticity value 0 134 Fecundity elasticity 0 187 Management options There is pressure from local citizens to make use of the areas where the WPFO grows For example 1 Use the field as a hay field which means mowing each year This results in cutting leaves off of plants which de creases flowering and vegetative plant survival 2 Allow spraying of nearby crops with insecticides to reduce agricultural pests knowing that these sprays will re duce the number of pollinating moths moths are killed by the insecticide 3 Drain the field which will dry out the soil and reduce seed viability and the chances of seed germination Option 2 would be the least harmful to the WPFO Option 3 would be the most harmful Seed viability or seed germination is the most important stage of or chid population viability because it has the greatest effect on lambda and the largest elasticity value When I decreased the seed viability by 50 the lambda changed to 0 849 I repeated these calculations for the vegetative stage and flowering stage The negative effect on seed viability had the most drastic effect on lambda and would decrease the population of orchids significantly How might you deal with conflicts that could arise with citizens whose activities might have to be curtailed e g if you chose to allow spraying but not haying Prolong mowing of the fields until after the seeds have become embryos and reached adulthood This would increase seed and embryo viability reduce the amount of draining as the loss of water has the biggest impact on WPFO populations Citizens could use the field for cattle if grazing was at a managed time Cattle have been known to disperse seeds over a given area and could help plant seeds into the soil This could increase seed viability Mari Roberts BSC3052 Sec 3 October 5 2012 What are some possible weaknesses of the model you used for this PVA and how might they affect your conclusions The PVA could be more accurate if it was run for more than 5 years Running a PVA model for a longer time period would yield a better long term average lambda This model also did not take into account the presence of demographic stochasticity genetic variation or environmental effects such as Options 1 2 3 Taking these aspects into account would have made our long term average lambda more accurate as well What additional data or analyses might allow you to make a better recommendation for management of this species take into account the presence of demographic stochasticity genetic varia tion and environmental effects such as Options 1 2 3 The PVA performed excluded the details of habitat change or the involvement of any manage ment or conservation of the habitat