Meal Worm Practical Flashcards
Estimating population size
Approx distribution and abundance of individuals over space and time. Important for conservation/ evolutionary biology and ecology research - it is not usually possible to count whole population
Capture mark recapture models (CMR)
Animals marked uniquely so that recaptured animals can be distinguished from those captured once
Assumption: all individuals are independent of each other and have same probability of getting caught
This is not always the case as certain individuals may be caught more easily due to pop. heterogeneity (diff in age, sex, size, colour, social status, territorial location etc)
May be pos or neg as catch response leads some animals to become trap happy and others trap shy
Open or closed population
Closed population easier to study but only for short term investigation
Open includes Emmi/immigration
Impact of birth and death over time
Lincoln Peterson method
Estimate N (total pop) by capture and recapture (2 captures)
First catch S1 should be equal in no. to second capture S2 (aka first recapture)
S1 red dot mark and S2 blue dot mark. Also count those already marked in S2 (this no. = R1,2)
Proportion of total pop caught first time = proportion of second sample caught previously (S1/N = R1,2/S2)
So estimated population N= S1xS2/R1,2
Bailey’s triple catch method
Continuation on Lincoln Peterson method ( S1 marked red, S2 marked blue R1,2 counted)
Then third sample of same no. collected at random S3 ( second recapture)
Divide recaptured individuals into
R1,3 those marked in 1st capture and recaptured in S3 red dot
R2,3 those marked 2nd capture and recaptured blue dots. Also R1,2,3 Individuals captured all 3 times (blue and red) included in this group
Calculate population of marked individuals (M)
M=( S2xR1,2/R1,2,3+R2,3) + R1,2
To estimate whole population (N) take into account pop of marked individuals (M) and relationship between M & S2
Proportion of total marked population caught 2nd time = proportion of total pop caught second time
I.e. R1,2/M = S2/N
So N = MxS2/R1/2
CMR assumptions
No recruitment/death between sampling occasions
Animals not effected by marking
Marks do not rub off or get lost
Marked animals mix completely
Pop sample random in regard to sex status and age
Sampling time is short relative to study time otherwise pop may be open.
Mealworm practical aims
To compare 2 diff capture and recapture methods for estimating size of mealworm pop.
Learning outcome With the aim to make estimates of pop size using pop. Ecology techniques
Life cycle of mealworm (Tenebrio Molitor)
Eggs
Mini worms
Molted worms
Large worms (studied stage)
Pupae
Young beetle
Adult beetle - mate and produce eggs
Formative data assignment
Determine how best to compare estimates of population size obtained using 2 methods
Present results clearly (from class data sets) graph of data, simple statistical analysis + brief conclusion
Check if data norm dist to decide whether to use para or non parametric test
Decide whether or not sig diff between the two pop estimates
Use 2 pages
Ask : is there sig diff between the 2 pop estimates?
How to display graphically?
How to test statistically?
Include table of summary stats to aid data display
determine significance of any apparent diff between 2 pop estimates
Statistical analysis
Dist/sample size:
plot histogram or F test for variances (excel)
Or Kolmogorov-Smirnov test (SPSS) to check for norm dist.
If sample size >40 or norm dist. Use a parametric test i.e. two sample t-test - compared 2 means and spread of data around mean - independent or paired T-test
If data not norm dist and n is small use a non- parametric test e.g. Mann-Whitney U test or Wilcoxon signed-ranks test (see if median of sample is specific value)
Use a parametric test with a sample >15<40 if distribution is just a little skewed
Write summary statistics for paired T tests comparing class estimates of mealworm pop. Using the 2 diff methods
E.g. methods compared: PL and BTC
T stat: 5.97
Degrees of freedom: 75
Associated probability p<0.0001
Accept or reject null hyp and explain why
