The MCR (Mutual Climatic Range) method is a technique for deriving quantitative
temperature reconstruction from fossil beetle remains developed during
the 1980's (Atkinson et al. 1986). It
is a Modern Analogue Technique (MAT) in that it uses the modern thermal
distribution of taxa as the basis for 'retrodicting' palaeotemperatures.
BugsCEP includes the facility for running these calculations and outputting
the results in table and graph form to MS Excel, along with the sample
thermal envelopes (climate space maps). The MCR component is called BugsMCR,
and uses the Birmingham RECON dataset.
MCR uses the area of mutual overlap of the thermal envelopes of the species
in a sample as the most probable thermal range, rather than looking for
similar species assemblages from the presnt day.
More information about the use of MCR in Bugs can be found at http://www.bugs2000.org/bugsmcr/index.html
or in Buckland & Buckland (2002).
Although it has its weaknesses, the (uncalibrated) MCR method is robust,
honest in its range estimates, and mathematically transparent. It was
also the first method to highlight the rapidity of warming at the end
of the last Ice Age.
|MCR can be calculated for any site that includes
species that have temperature data. At the time of writing there are
436 of these - you can see the list by clicking the 'Show All MCR
Species' link on the BugsMCR interface.
- To open the BugsMCR interface click the [BugsMCR] button
on the main toolbar.
- If you have created
a site, and entered
abundance data for it then it will be available from the 'Site'
dropdown box towards the top of the screen. (Use the [Refresh
sites list] button if it is not there).
Sites without abundance data are not shown.
(You can limit the species available for species list creation
to only those with MCR data in the 'Species
List Editor' if necessary)
- If the site has more than one countsheet, then selecct the required
one from the 'Select Countsheet' dropdown box.
- Click [Activate this countsheet], and the species list
will be loaded into the right hand half of the screen.
You can now use the 'Show Current Countsheet' link to examine
the abundances if you wish. Note that until you click the [Activate
this countsheet] button this link will show the previously used
- Select the options for output and calculation as follows:
- Closest to 100% - calculates MCR even for samples
with no 100% overlap between species.
- TMax & TMin Graphs - create graphical output.
- Sample envelopes - output grids of combined thermal
envelopes for each sample.
- Sample species lists - output the species list for
each sample underneath their respective envelopes.
- Click the [Run MCR on All Samples] button, and choose
a location and filename to save your output files. If 'Sample
envelopes' have been selected for output these will be saved in
a second file with the suffix '-matrices'.
- Stand back and let BugsMCR do its calculations. Wait until
the Penguin has finished moving before doing anything, as the
program needs full control of your computer.
- When calculations are complete you will be informed of where
the output files have been saved, and can click on buttons to
open them from within BugsMCR.
See below for an explanation of the
Calculate MCR for all species
at a site (full species list - ignore samples)
|This is most useful for teaching excercises,
but allows you to see the combined climatic implications of all species
through series of samples.
Remember that MCR results CANNOT BE AVERAGED
OVER SAMPLES*. Be creative with countsheets
in order to combine samples and calculate results over several samples.
|Follow the instructions above, but at number
6 click [Run MCR on Species List only].
Graphs will not be created, since only one set of results will be
Predict species presence from temperature
An exploratory tool that lets you (A) pick the
thermal range maximums of any species, and ask the database which
species can theoretically survive within those limits. You can also
(B) input single summer & winter temperature values and get
a list of all species that can survive at that temperature.
NOTE: The prediction tools are
still under development, and the implications of the reults must
be considered carefully when used. More range based search functions
will be added in the near future.
(A) Use ranges
- Access the Predictions interface from the BugsMCR screen by
clicking the [Predictions] button.
- Use the 'Tools' section to select a taxon from the MCR database.
- Click the [Copy to ranges search boxes] and the temperature
values will appear in the 'Ranges' section.
- Click the [Find Species that are equal or narrower within
range] to do what the button says.
- You can adjust any value and click the latter button again to
see the changes. It is wise to use the TMax/TMin values and
TRange values mutually exclusively, as they are interrelated.
Blanking a values leaves it out of the criteria.
- The results will be displayed in tabular form (as a query result).
You may have to move windows and resize columns to see everything
Raise the upper limits of the mean summer and winter temperatures
(TMaxHi and TMinHi) by 2 degrees and the species list expands as
the ranges of new species are encompassed:
(B) Use single summer and winter values
- Enter a TMax and TMin value in the 'Specifics' boxes and click
the [Find Species where range includes these values].
- These lists will be considerably larger where values close to
European means are used.
BugsMCR output files explained
|BugsMCR creates two output files on demand:
- the main file (your filename.xls) - containing results tabulation
- the matrices files (your filename_matricies.xls) - containing climate
space maps and sample species lists
The Main File
Two worksheets: Graphs and Results
Temperature values in degrees Celcius
show range of temperature values reconstructed. Note:
this is a range and not a mean and s.d. - it has no valid
Samples are currently only sorted in order of input (sorry),
so may need to be rearranged on the Results worksheet.
See below for explanation of variables.
Number of taxa in reconstruction
Percentage of species in sample in area of maximum overlap.
Numbers below 100% are not true MCR values and should be investigated
as to their ecological/taphonomic cause...
The Matrices File
|Results worksheet duplicated (as above) and then one worksheet per
|Example sample worksheet
Value in each cell shows the percentage of species in sample
that can survive in that climate cell.
Cell indices represent the upper limits of 1 Celcius thermal
Rows = TMax:
Row 1 = 36C
Row 36= 1C
Columns = TRange:
Column A = 6C
Column BH= 65C
Note: this matrx has been colour shaded with Poptools
Sample species lists are inserted immediately below the envelopes
TMax - mean value of warmest month (usually July)
TMaxHi - highest temperature of TMax in species envelope
TMaxLo - lowest temperature of TMax in species envelope
TMin - mean value of coldest month (usually January)
TMinHi - highest temperature of TMin in species envelope
TMinLo - lowest temperature of TMin in species envelope
TRange - difference between TMax and TMin, and a useful index
of continentality (higher values represent more continental climates)
TRangeHi - highest value of TRange in species envelope
TRangeLo - lowest value of TRange in species envelope
Since the thermal envelopes are grids of TMax vs TRange, it
follows that TMin is calculated from the values resulting from the
overlap of these grids. TMin is derived by subtracting the TRange
value from TMax of each cell in the area of maximum overlap, and
the extremes providing the TMinHi and TMinLo values. (Note
that it is incorrect to only use the ordinally outermost cells due
to the none rectangular form of the thermal envelopes).
The area of mutual overlap for the species in two different samples will
most probably not be the same as the average of the MCR results from each
sample. Or, more accurately, the area of mutual overlap for the combined
species lists will not be the same of the average values of the areas
of mutual overlap for the separate species lists.
ATKINSON, T. C., T. C., BRIFFA, K. R., COOPE, G. R., JOACHIM, J. M.
& PERRY, D. W. (1986) Climatic calibration of coleopteran data. In
B. E. Berglund (ed.) Handbook of Holocene Palaeoecology and Palaeohydrology,
851-858. J. Wiley & Son, Chichester.
BUCKLAND, P.I. & BUCKLAND, P.C. (2002). "How can a database
full of Bugs help reconstruct the climate?". In Burenhult, G &
Arvidsson, J (eds) Archaeological Informatics - Pushing the Envelope -
CAA 2001 - Computer Applications and Quantitative Methods in Archaeology,
Proceedings of the 29th Conference, Gotland, April 2001. BAR International
Series 1016. pp.453-461.