Samantha Stosur has beaten compatriot Ashleigh Barty in straight sets in the second round of the Miami Open.

Stosur prevailed 6-4 6-4 after in-form wildcard Barty came into the clash off a victory over former top-five player Eugenie Bouchard in Miami.

Earlier, Australia’s Ajla Tomljanovic scored an upset victory over world No.13 Elena Vesnina.

World No.594 Tomljanovic overcame Indian Wells champion Vesnina 3-6 6-4 7-5 to secure a spot in the third round.

The 23-year-old Tomljanovic, who is Nick Kyrgios’ girlfriend, led Russia’s Vesnina 5-3 in the third set on Thursday when a thunderstorm halted play, returned on Friday (Saturday AEDT) and cashed in on her third match point.

One-time world No.47 Tomljanovic made her return last month after just over a year on the sidelines with a shoulder injury.

French Open champion Garbine Muguruza, whose opening match on Thursday was also interrupted, fared better than Vesnina after her night’s sleep.

The sixth-seeded Spaniard, who trailed 46th-ranked American Christina McHale 6-0 3-2 when play was suspended Thursday, escaped a match point in the tiebreak and emerged with an 0-6 7-6(6) 6-4 victory.

Romanian third seed Simona Halep was pushed to three sets by Japanese teenager Naomi Osaka before advancing 6-4 2-6 6-3, while seeds Timea Babos and Roberta Vinci were also eliminated.

France’s Pauline Parmentier overcame Hungarian Babos, the 24th seed, 6-7(1) 6-2 6-0 three sets, and American qualifier Taylor Townsend beat 25th seed Vinci of Italy 6-3 6-2.