PHILADELPHIA — The shortage of Roman Catholic clergy isn't just being felt in church.

Religious orders that have founded and run Catholic colleges and universities across the U.S. — in some cases for more than a century — are grappling with how to retain the institutions' distinct religious identities in the face of declining numbers of priests and nuns.

The Rev. Timothy Lannon, president of Saint Joseph's University, can envision a time when a lay person will lead the Jesuit school in Philadelphia because of the dwindling number of his brethren. So it's important now to instill the order's philosophy on campus through curriculum and staff initiatives, he said.

"Without Jesuits, how can you call yourself Jesuit?" Lannon said.

Saint Joseph's is not alone, said Richard Yanikoski, president of the Association of Catholic Colleges and Universities.

As religious orders shrink, the critical challenge is for Catholic identity "to be built into the goals and operations and practices of the institution," Yanikoski said.

Retaining that identity was somewhat easier in previous generations when priests and nuns who ran the schools wore religious garb as they carried out teaching and administrative duties, he said.

"Everyone could see the Catholic identity of the institution in those people," said Yanikoski.

Yet diminishing numbers, and members of orders opting for secular dress, have combined to change that sensibility at places like Saint Xavier University in Chicago, which was founded by the Sisters of Mercy and where Yanikoski served as the third lay president.

The school's student body has changed as well, said university spokesman Joseph Moore. While the percentage of Catholics is still very high, today's students grew up under Vatican II reforms and are less steeped in what might be considered traditional Catholic culture, he said. They are required to take two religion courses, but not necessarily on Catholicism.

Saint Xavier tries to maintain its roots by offering a "peer mentoring" program in which staff members periodically meet after work for informal, faculty-led discussions on what it means to work in a Catholic institution.

But it's still a challenge. Only two sisters remain among the faculty at the 5,700-student campus, Moore said. Five more work in other roles at the school.