1. The emerging role of molecular markers in coccidian speciation:
Katarzyna B. Miska, Dagmara Motriuk-Smith, R. Scott Seville
June 29, 2008

2. Why is use of molecular tools important:
Eimeria are be morphologically very similar.
-Can lead to erroneous classification
-Usually needs “an expert eye” to be carried out correctly
Analysis of DNA sequences is fast, relatively inexpensive, can provide information discerning differences among closely related species or strains of the same species.
Selecting the correct gene to answer these questions is KEY.

3. Use of 18s ribosomal DNA sequences
Historically very common
Sequences are conserved
Primer design and amplification is relatively easy
although complete sequence is around 1.8 kb.
Probably represents the largest database of available Eimerian sequences.

4. 18s Phylogeny Updated to include data from other galliforme
birds: Chukars and pheasants
More questions arise:
is Eimeria of chickens and turkeys
paraphyletic
Do cecal Eimeria in galliforme
birds represent (ie E. tenella,
E. necatrix, E. adenoides)
a separate colonization of the
Gut?

5. Cytochrome c oxidase subunit I
Encoded on the mitochondrial genome
Well conserved (most highly conserved of the mitochondrial genes
Single copy

7. ITS-1 and ITS-2 Use has been very wide especially in higher eukaryotes
Quickly evolving- very divergent even among closely related taxa
In Apicomplexans structure and evolution or ribosomal DNA may be VERY different
For example: Plasmodium falciparum has two independently evolving rDNA gene, expressed differentially among stages of the life-cycle.
Similar rDNA structures also found in Cryptosporidium, Theileria, and possibly Eimeria maxima
This can confound phylogeny

8. Eimeria maxima appears
to contain at least two
highly dissimilar ITS-1
sequences (same is seen
with ITS-2)
ITS sequences are most
likely of limited use in
reconstructing species
phylogeny in Eimeria
BEWARE of ITS based
Species phylogenies

9. The future? Better sampling of species Multi-gene phylogenies
Identify more suitable target genes to base species phylogenies on. Such as conserved (at least in Eimeria), single copy, nuclear genes.