Table 2. Statistics of gene introns in the chloroplast genome of five Ulmus species.

Gene	Strand	Ulmus pumila	Ulmus davidiana Planch. var.	Ulmus macrocarpa	Ulmus davidiana	Ulmus laciniata
trnL-TAA	-	√	√	√	√	√
trnL-TAA	+	√	√	√	√	√
trnF-AAA	-	×	×	×	√	×
rpoC1	-	√	√	√	√	√
ycf3	-	×	√	√	√	√
rpl2	-	√	√	√	√	√
ndhA	-	√	√	√	√	√
trnY-ATA	+	×	√	×	×	×
ycf1	-	√	√	√	√	√
ndhB	+	×	√	√	×	×
rpl2	-	×	×	×	√	×
rps12	-	√	√	√	√	√
rps12	+	√	√	√	√	√
trnA-TGC	+	√	√	√	√	√
trnA-TGC	-	√	√	√	√	√
trnV-TAC	-	√	√	√	√	√
trnI-GAT	+	√	√	√	√	√
trnI-GAT	-	√	√	√	√	√
Total		13	16	16	17	14