MOVING: Howard Yezerski is taking his venerable Newbury Street Gallery to the South End.

A week after Allston Skirt Gallery got two of its artists named among the four finalists for the Institute of Contemporary Art’s 2008 Foster Prize, word began to spread that the nine-year-old gallery would be closing at the end of its next show.

The news turned out to be the first sign of a major gallery shake-up involving a number of Boston’s most prestigious venues. Three galleries are closing, several are moving, and others are restructuring. Are these changes just the start of a contraction as the tanking economy begins to affect the local art market?

The three-year-old Space Other gallery at 63 Wareham Street will close after its April 4-26 show, but it’s planning a series of “Space Other at other spaces” exhibits in Amsterdam, Berlin, New York, San Juan, and Mexico City in 2008 and ’09. Judy Ann Goldman at 14 Newbury Street plans to close, at least temporarily, at the end of June and “use the summer to reassess my next move.” There are widespread rumors that Rhys Gallery at 401 Harrison Avenue may leave town; owner Colin Rhys declined to comment. At least three additional galleries seem to be on the bubble and may close in the coming months.

On the plus side, GASP gallery in Brookline (run by artist María Magdalena Campos-Pons) plans to open an expansion at 368 Boylston Street, next door to its existing space, during Brookline Artists’ Open Studios on April 12. It will offer a performance and meeting space, a shop selling artist-designed functional multiples, and occasional art exhibits. Ami Bennitt, who organized art shows at the Paradise Lounge, opened the gallery Space242 on East Berkeley Street in January. And Stephanie Walker, former director at Newbury Street’s Chase Gallery, hopes to open her own gallery on Newbury, perhaps as early as this fall.

Bernard Toale is hashing out a new lease that would have his gallery director, Joseph Carroll, take over much of the space as his own independent gallery (and maintain the Boston Drawing Project) by September while Toale opens an art-consulting business in a corner of the space. Axiom Gallery co-director Phaedra Shanbaum is scheduled to move to England in August to pursue graduate studies in art history. The gallery plans to continue operations under the other director, Heidi Kayser, with Shanbaum offering long-distance advice.

A number of galleries are moving, continuing the shift in numbers — and power — from Newbury Street to the South End, where rents can run half of what they do on Newbury Street. Howard Yezerski is working out a lease to move from 14 Newbury Street to 460 Harrison Avenue over the summer. There are widespread rumors that Miller Block Gallery, whose lease expires this summer, may also move from 14 Newbury Street to Harrison Avenue; the gallery declined to comment. Beth Urdang is looking for a new Newbury Street spot for her gallery when the lease on her space at 129 Newbury expires June 1. John Colan moved his HallSpace gallery from 31 Norfolk Avenue in Roxbury to 950 Dorchester Avenue in Dorchester in February, after his old building changed hands.

One cause of the upheaval is the schedule of developer Mario Nicosia’s GTI Properties, which owns numerous South End buildings. The leases of several galleries around town expire in coming months, but the leases of all tenants at GTI’s 450 Harrison Avenue at Thayer Street — the major art building in the South End — expire in November, according to commercial leasing director John Kiger. And rents are rising.

But GTI is also redeveloping an old factory building next door at 460 Harrison Avenue, and tenants could begin moving in as soon as this summer. “I think this year we’d bring on something like 10 to 15 more galleries [to 460],” says Kiger. Some dealers are skeptical of that number — if true, it would double the number of galleries on Thayer Street. A furniture store and restaurant are also rumored to be among the incoming tenants.

Allston Skirt, which is owned by Beth Kantrowitz and regular Phoenix contributor Randi Hopkins, and Space Other, which is run by Gamaliel Herrera and Mark Schwindenhammer, say economics isn’t the driving factor in their decisions to close. (For Kantrowitz and Hopkins, whose rent was rising, it seemed a good time to pursue separate visions; for Herrera and Schwindenhammer, it was the international curatorial opportunities.) Long-time Newbury Street galleries like Pucker Gallery and Barbara Krakow Gallery talk of the past year as a banner one. So Krakow doesn’t see a downturn in sales as a key factor — yet. “I’ve been through this before. It’s hard for me to believe this [a downturn] isn’t going to happen.”

But with leases ending and rents rising, dealers are taking hard looks at their futures. Bernard Pucker, who has seen hundreds of Boston galleries come and go since he opened his gallery in 1967, sees the changes as part of the usual “winnowing out.” The strong art market of the past several years — boosted by Internet and art-fair sales — has helped keep more galleries afloat, but if it cools it could leave them in a lurch.