ST. PETERSBURG — The leader of the University of South Florida St. Petersburg has been ousted.

University officials did not provide an immediate reason on Friday for the departure of Sophia Wisniewska, USFSP's regional chancellor of four years.

Wisniewska said she is leaving her post with pride and gratitude.

"One of the great joys of my career has been my years as regional chancellor at USFSP," Wisniewska wrote in a text message to the Tampa Bay Times late Friday. "In the life of any institution, there are natural times for leadership change. This is one of them."

The school named newcomer Martin Tadlock as interim leader. Tadlock came to St. Petersburg a year ago as the regional vice chancellor of academic affairs.

When Wisniewska joined the university in July 2013, she took the helm of a school seeking to reinvent itself.

USFSP, numbering about 4,700 students, only began graduating its own students and housing them on campus in the last decade or so. The small waterfront campus, where two-thirds of students commute, has made strides to become the first choice for some local high school graduates. But it still sought a greater sense of identity.

Wisniewska brought experience in strategic planning. She led the development of a sprawling strategic plan, which proposed doubling the student body — a serious endeavor — and building brand-name academic programs that would set the school apart.

"Working together with the board of trustees, faculty, staff and students, we made extraordinary progress," she said Friday. She cited new majors and minors, a growing reputation and fundraising successes. During Wisniewska's tenure, the school received its largest-ever gift, $10 million toward naming the Kate Tiedemann College of Business.

Read more: After years of planning, USF St. Petersburg opens new home for its business college

The university has long been dwarfed in size and reputation by USF Tampa across the bay, a research heavyweight with nearly 43,000 students in all. Ambitious USF System leaders, while recognizing the different strengths of each institution, have asked leaders of each campus to improve graduation rates and other metrics, in hopes of enhancing the student experience and increasing prestige.

USFSP's retention and graduation rates have lagged USF Tampa's for years, but the difference has become more stark as the Tampa campus has shot to preeminence. In recent months, USF System leaders have questioned Wisniewska about St. Petersburg's efforts to help students stay on track and graduate in a timely fashion.

Just 38 percent of USFSP students graduate in six years. USF Tampa, in comparison, graduates 70 percent in six years.

Stephanie Goforth, chair of the university's board of trustees, declined to comment about Wisniewska's departure.

"We will be providing an update to our community in the near future," USF spokeswoman Lara Wade said in a statement Friday evening. "We will not be commenting further at this time."

USFSP will not be the only USF institution with an interim leader. Earlier this year, the regional chancellor of USF Sarasota-Manatee stepped down, citing family reasons, amid years of lackluster funding for the university.

From 2013: A chat with Sophia Wisniewska, the new chancellor of USF St. Petersburg

Contact Claire McNeill at cmcneill@tampabay.com or (727) 893-8321.