When El Diario, the nation’s oldest Spanish-language daily newspaper, merged with La Prensa in the early 1960s, there was no question who its readers were: Puerto Ricans. That’s no longer the case. El Diario/La Prensa has a diversified audience, mirroring the Hispanic population of the city, where there is an increasingly broad spectrum of Latino immigrants. Today it will name as its editor a Mexican-born journalist with a Guatemalan-Greek background, Alberto Vourvoulias-Bush.

A Brooklyn resident, Mr. Vourvoulias-Bush is a former editor at Time magazine who until Friday was managing editor of ARTNews.

“This is an important moment to reach for someone with his knowledge,” the publisher and CEO of El Diario, Rossana Rosado, said, noting intense competition from Hoy, the city’s other leading Spanish-language daily. “He’ll bring a whole new dynamic to the market.”

When Ms. Rosado, who was born in the Bronx to Puerto Rican parents, started at the paper as a reporter in the 1980s, she said, the transformation among the city’s Hispanics was already evident. Puerto Ricans began to rise on the social ladder and move on to the suburbs and Florida, and the influx of Dominicans was well under way. Meanwhile, new immigrants from South and Central America started to take footholds in the city.

“No one can deny there’s been an incredible, and I mean increible, growth in the Colombian, Ecuadorian, Mexican population,” Ms. Rosado said. El Diario’s content and readership have reflected the shift. While about 50% of the readership remains Dominican and Puerto Rican, people from Central and South America now make up more than a third.

“As a daily newspaper in New York City you couldn’t stay alive if you continued to be what people call ‘a Puerto Rican paper,'” Ms. Rosado said.

The new editor, Ms. Rosado said, was chosen for his qualifications, not his background, but his understanding of diverse Latino communities gives him a clear advantage. As deputy editor of Time magazine’s Latin America edition, Mr. Vourvoulias-Bush, 47, visited and reported from nearly every country in the Americas. Meanwhile, he has lived in New York for the past 15 years and been a loyal reader of El Diario and Hoy during that time.

One of the first editors of El Diario to come from a leadership position at a top English-language publication, Mr. Vourvoulias-Bush said that what attracted him to the paper is he thought El Diario and other specialized and upstart publications are doing some of the most interesting work in journalism.

Recipient of a master’s degree from Yale University’s Department of Politics, he comes from a more privileged background than the typical El Diario reader. Still, he said he thought his experience growing up in Central America gives him a perspective on what recent immigrant communities face.

His father, a Chicago-born businessman, met his mother, the artist known as Joyce de Guatemala, while working in Mexico City. Mr. Vourvoulias-Bush was born there, but the family moved to Guatemala when he was young. At 16 he came to America to finish his schooling, going on to study international relations at the University of Pennsylvania.

Four years ago, he married a novelist, Jhumpa Lahiri, who won the 2000 Pulitzer Prize for fiction for “Interpreter of Maladies.” The daughter of a couple from India, she was born in London and grew up in Rhode Island. Their wedding was a traditional Bengali ceremony, in which Mr. Vourvoulias-Bush chanted Sanskrit mantras. He and his wife, who live in Park Slope, are raising their two children to be trilingual, speaking Bengali, Spanish, and English.

The increasingly transnational nature of immigrant communities is one element that Mr. Vourvoulias-Bush is looking forward to exploring at El Diario.

The forces of globalization are frequently broken down into financial shifts, movement of labor, and increased cultural diversity, said Mr. Vourvoulias-Bush, who also worked as a research associate at the Council on Foreign Relations. The readers of El Diario “live the conjunction of those three historical movements,” he said. “They embody them in many respects. That’s what I hope we will be addressing.”

Indeed, many readers of El Diario have said they first flip to the paper’s Nuestos Paises or Our Countries section to find news from their native country, and then to local news. The paper’s sports section includes baseball, particularly popular with Caribbean immigrants, but it has more soccer coverage than any English-language daily. During the summer, almost every week the paper will feature a different national festival.

Finding the balance between reporting on New York and on more than a dozen Latin American countries is one of the great challenges of editing El Diario, a former editor, Gerson Borrero, said.

Mr. Borrero, who now writes a regular column for the newspaper, said it has “a responsibility” to show new immigrants “the way.”

“At the same time you try to entertain them,” he said, “and you need to be able to kick some ass when there are abusive people.”

Mr. Vourvoulias-Bush is the third editor at El Diario in a tumultuous two years. In 2003 Mr. Borrero left after his bosses at the paper, in which the primary owner was Knight Paton Media Corp., said he could not run a column written by Fidel Castro. After he left, the paper joined forces with the Los Angeles daily La Opinion to form ImpreMedia, and a former editor from La Opinion, Pedro Rojas, took over at El Diario. Mr. Rojas lasted less than a year and left last month, citing family reasons.

At the same time El Diario has weathered turmoil over editors, it has faced fierce competition from Hoy for dominance in the Spanish market. Two years ago, Hoy was reported to be crushing El Diario, claiming average weekday sales of more than 90,000 copies to El Diario’s 50,000. Then last year the Audit Bureau of Circulations said it had found that Hoy, which is owned by the Chicago-based Tribune Company, had inflated the numbers by nearly 50%. The scandal returned El Diario to its no. 1 spot in the Hispanic media market, but just barely. Last winter, El Diario, its circulation still about 50,000, led Hoy by only 1,500 copies.

Challenges aside, Mr. Vourvoulias-Bush said he was excited to take the helm of a paper with a more than 90-year history and looked forward to covering a wide range of topics, from the mayor’s race to soccer to art, at a pivotal moment for the community.

“It’s a very important time for the Spanish-speaking population,” he said. “They’re on the verge of more recognition, not only of their diversity but of their growth and potential.”