Exotic Marker
Definition
A known quantity of an introduced pollen type (often Lycopodium clavatum spores from a calibrated tablet) added to a sample before processing. Allows calculation of pollen concentration per unit of original sample.
- Typical material
- Lycopodium clavatum spore tablets, calibrated count
- Purpose
- Calculates pollen concentration per gram of sample
- Added at
- Before chemical processing of the sample
- Field
- Forensic and Quaternary palynology sample preparation
Common questions
Why must the exotic marker be added before processing rather than after?+
Processing steps such as acetolysis, sieving, and centrifugation cause proportional loss of both marker and sample pollen. Adding the marker first means losses affect both equally, so the ratio between counted marker grains and sample grains still yields an accurate concentration.
Why use Lycopodium instead of a pollen type native to the region?+
Lycopodium spores are morphologically distinctive and essentially absent from casework samples, so an analyst can count them without confusing them with pollen under investigation, and calibrated tablets give a known, reproducible starting count.
What does a very low marker count on a slide indicate?+
It signals a processing or mounting problem, such as spore loss during transfer or an under-dissolved tablet, and the concentration calculation for that sample becomes unreliable until repeated.
Related terms
- Acetolysis
- Erdtman's 1934 extraction method. The sample is treated with a 9:1 mixture of acetic anhydride and concentrated sulphuric acid, which dissolves cellulose...
- Assemblage
- The full community of diatom taxa present in a sample. The relative frequencies and absolute counts of species in an assemblage reflect...
- Pollen Sum
- The total number of pollen and spore grains counted on a slide, used as the denominator for calculating the percentage of each...
- Provenance Opinion
- The analyst's conclusion about the geographic or habitat origin of a pollen assemblage, expressed with explicit statement of confidence level, comparison data,...
- Reference Collection
- A curated library of verified specimens from known species, subspecies, and geographic populations used as comparators in forensic identification. The depth and...