Near-lattice-matched and highly compressive-strained InxAl1-xN epilayers were grown on GaN templates by metalorganic chemical vapor deposition. The V-defects associated with screw-component threading dislocations (TDs) were found in all the InxAl1-xN layers. Their origin and evolution were investigated through near-lattice-matched In0.173Al0.827N layers with different thicknesses. Furthermore, small V-defects not associated with TDs were also found in InxAl1-xN layers with high In composition (x=0.231). Stacking mismatch boundaries induced by lattice relaxation in InxAl1-xN epilayers under large strain is believed to be another mechanism forming V-defects.