A character-based approach in the Mexican cycads supports diverse multigene combinations for DNA barcoding

Area of Science:

• Botany
• Molecular Biology
• Genetics

Background:

• DNA barcoding is vital for species identification.
• Cycads (Ceratozamia, Dioon, Zamia) in Mexico require effective molecular identification methods.
• Previous studies informed the selection of potential DNA barcoding loci.

Purpose of the Study:

• To identify the optimal DNA marker combinations for species-level molecular identification in three Mexican cycad genera.
• To evaluate the performance of seven chloroplast and one nuclear DNA regions using a character-based approach.

Main Methods:

• DNA barcoding was performed on Mexican cycad species.
• Seven chloroplast regions (matK, rpoB, rpoC1, rbcL, atpF/H, psbK/I, trnH-psbA) and the nuclear ITS2 region were tested.
• Data analysis employed the "character attributes organization system" (CAOS) for DNA diagnostics.

Main Results:

• Optimal identification varied by genus: Ceratozamia required four chloroplast and one nuclear region (>70% identification).
• Dioon identification (79%) was achieved with a two-gene chloroplast combination (atpF/H + psbK/I).
• Zamia identification (75%) required a four-gene combination (atpF/H + psbK/I + rpoC1 + ITS2).

Conclusions:

• The optimal DNA marker combinations for Mexican cycads differ from the universal plant core barcode (matK + rbcL).
• Specific multi-locus strategies are necessary for accurate species identification in these cycad genera.
• The findings highlight the need for genus- or region-specific DNA barcoding marker selection.