Corpus Christi, Texas, is not the first place you would think to look for a Jewish community - and not just because of its name.

"This was once a frontier," said local rabbi Ken Roseman. "There were Indians, there were cowboys, there were bandits, there was adventure."

Yet over the last century and a half, this port city on the Gulf of Mexico, known for its oil and farming industries, sustained a small but vibrant Jewish community.

Recently, however, the two shrinking congregations discovered the town was no longer big enough for both of them. But rather than a showdown, the shuls - one Reform, the other Conservative - merged.

This pattern is being repeated across America, as synagogues struggle to cope with declining Jewish populations. In some places, the community migrates to another part of town; in other cases, it leaves town altogether or assimilates. The solution for a few wealthy synagogues has been to lure young couples to join them, with financial incentives of up to $50,000.

But for more cash-strapped Conservative and Reform congregations - roughly equivalent to Reform and Liberal in the UK - there is the prospect of a merger.

Rabbi David Fine, a specialist in merging congregations for the Union of Reform Judaism, called the few recent examples of interdenominational merger "the tip of the iceberg.

"It works because we are fluent and comfortable with each other, even though there are some theological and philosophical differences," he said. "There is a much greater understanding and appreciation for the other."

Rabbi Fine said the merger process is complicated and slow. He has been working for some time with two congregations in Georgia, "but it's still not done yet".

Dr Stuart Rockoff, of the Institute of Southern Jewish Life, said he knows of at least two congregations, in Galveston, Texas, and in Pensacola, Florida, where Reform and Conservative shuls have had held informal discussions. But there are still many issues to iron out.

In Miami, Florida, the Conservative Congregation Samu-El Or Olom and the Reform Temple Bet Breira merged in 2008 to form Bet Breira Samu-El Or Olom. The two congregations mix for social activities, community projects, religious education and bar- and batmitzvah classes.

"But when it's time to worship we have different rituals and philosophies," said Reform Rabbi Jamie Aklepi.

On Friday nights, a Reform service is held in the sanctuary and a Conservative service is held in the synagogue's ballroom, which has been converted for prayer. On Saturday mornings, the Conservative congregation worships in the sanctuary and the Reform congregation meets for a bagels and Bible class in a hall. If there is a Reform bar- or batmitzvah that week, the congregations swap.

Bet Breira Samu-El Or Olom sits in a section of Miami-Dade County that is steadily becoming more Latin. Each congregation could have merged with another Reform or Conservative shul a few miles away. But Rabbi Aklepi said the congregations chose to merge "to create something more vibrant.

"We wanted to become one synagogue that offered different worship opportunities," she said. "If you look at surveys of how people define themselves as Jews, they define less as a denomination and more as whether they are traditional or non-traditional, Orthodox or not Orthodox. And how do we reach out to those people who are some kind of not Orthodox? By coming together we can offer a wide range of experiences."

Before the merger, the Reform congregation had 325 families, many with school-age children. The Conservative congregation had 250 families, most of whom were empty-nesters. Said Conservative Rabbi David Schonblum: "Now we have kids running up and down the bimah with the Torahs."

The merger has not been painless. The Conservative congregation had to sell their synagogue. The Reform shul had to move its Saturday religious school programme to Sunday and install a kosher kitchen. The merger of two boards, 44 people, has been complicated.

"It's a lot of bureaucracy," said Rabbi Schonblum.

There has also been friction. About 75 families have dropped out.

"We know that we can never please everyone," he added.

In Corpus Christi, the Conservative rabbi was made redundant and Rabbi Roseman leads a tailored service, with Conservative lay people and rabbis leading Friday and Saturday services occasionally.

Rabbi Roseman described the new Friday evening services as "middle-of- the-road Reform". On Saturday mornings, the congregation uses a Conservative siddur but omits certain sections, such as particular psalms. The haftarah is saved for an after-service study session.

"We agreed very clearly at the beginning we were going to be fair to everybody and we've worked really hard to do that in every way we can," said Rabbi Roseman.

The congregations, the Reform Temple Beth-El and the Conservative B'nai Israel Synagogue, even wound themselves down and created a new entity, Congregation Beth Israel, in 2006. The merger took about three years.

Nevertheless, the new shul lost a few families on the more traditional and liberal wings of each congregation.

Ruth Kane, 85, whose husband was cantor of the Conservative synagogue, was among them. Mrs Kane's group of about half-a-dozen families rents a house for its services. She said that a splinter group from the Reform had formed a tiny congregation too.

"They merged because we wanted one congregation," Mrs Kane said. "And now we have three."