The couple of a year and a half part ways to focus on their careers, his rep says

Young love can be so fickle: Mischa Barton, 21, and Cisco Adler, 28, have ended their relationship – for now.

“They have parted ways to concentrate on their careers,” Dvora Vener, publicist for Adler’s band, Whitestarr, tells PEOPLE.

The split comes amid speculation that Barton was upset by a nude photo of Adler that turned up on a Web site displaying items from a storage unit rented by Paris Hilton.

Adler himself told the New York Observer on Wednesday, “Mischa wasn’t too excited, to say the least. I think it was actually worse for her than for me in some ways. So yeah, I’m gonna try to keep my pants on from now on.”

Barton and Hilton, 25, sparred publicly last year: After Barton joked to a British tabloid that Hilton “seems to hate everyone around her age who is more successful. … She does steal people’s boyfriends!” Hilton countered to PEOPLE, “I don’t even know the girl. I could care less.”

Barton recently wrapped the film Virgin Territory with Hayden Christensen and Adler is currently taping a VH1 reality show with his band entitled The Whitestarr Project. A source close to the band tells PEOPLE, “I think this is a ‘I don’t see you enough and I’m filming a rock and roll reality show’ thing.”

But this might not be the end of things, the source says: “I just spoke to him earlier this week. Give it a week. If past tells the future they will be back together.”