The travel industry’s 800-pound gorillas have been bulking up, and consumers are getting nervous.

A series of mergers in recent months — from Expedia’s acquisitions of rival online booking companies to Marriott International’s recent takeover of Starwood Hotels and Resorts — have only quickened the pace of consolidation in the industry.

“I believe it’ll reduce competition,” Steve Ledewitz, an independent meeting planner, said of the Starwood-Marriott merger. He said he used to be able to drive bargains for clients by making Marriott and Starwood hotels vie for his business.

“Once my client picks the city they want to go to, Starwood and Marriott would compete against each other, and many of their brands do match up against each other, so there was a lot of head-to-head,” he said.

Others are taking a wait-and-see approach.

“It’s definitely got some positives and negatives to it,” Alex Borodkin, an SPG, or Starwood Preferred Guest, member who spends most of his time on the road as an accounting consultant, said of the acquisition. “It’ll open up more options for me to earn points, but I am worried about the value of my points going down.”

Part of the reason for the mergers is the rise of home rental sites, industry observers say. They call the Marriott-Starwood deal a prudent, perhaps necessary move in the wake of consolidation among online travel agencies, which hotels rely on for nearly 20 percent of their bookings, according to the research firm Phocuswright.

“The calculation here is really pretty simple,” said Douglas Quinby, vice president for research at Phocuswright. “When you control more supply and you have a distributor that brings you demand but needs your supply, you have a little bit more negotiating leverage.”

Marriott’s announcement came less than two weeks after the online travel agency Expedia said it would buy HomeAway, the home-rental platform and a chief rival to Airbnb, for $3.9 billion. And that deal followed two other acquisitions by Expedia this year, of its rivals Orbitz and Travelocity.

“I think Marriott recognized that bigger is better in dealing with some of the emerging threats to the industry, things like greater consolidation among the online travel agencies,” said David Loeb, a senior research analyst at Robert W. Baird & Co. “This is one way to fight back.”

The hotel companies bitterly, though unsuccessfully, opposed Expedia’s $1.3 billion purchase of Orbitz, which gives the combined company control of roughly 75 percent of the domestic market for third-party online booking, according to Phocuswright.

Expedia, which also owns sites including Hotwire and Hotels.com, now primarily competes against the Priceline Group, which owns Booking.com and has made several acquisitions of its own during the past couple of years, including OpenTable, the restaurant reservations platform, and Kayak.

Buying HomeAway, the biggest company in the home-rental industry, helps Expedia catch up, said Chekitan Dev, a marketing and branding professor at Cornell University’s School of Hotel Administration.

“It sort of levels the playing field with them a little bit,” he said, predicting that home rental eventually would be integrated in a way that makes it as easy for travelers to book as a hotel room. “I think, over time, it’s going to be just another option on Expedia.”

Dara Khosrowshahi, Expedia’s president and chief executive, said that consolidation had helped consumers. For instance, Khosrowshahi, who is also on the board of The New York Times Co., said his company had lowered or eliminated airfare booking fees on many itineraries. “Consolidation on the Internet has to be a force for price reductions,” he said.

“Consolidation on the Internet has to be a force for price reductions,” he said.

Corporate travel professionals expressed concern, though, that the Marriott-Starwood deal could kick off a domino effect of additional acquisitions.

“The perception might be there’s another consolidation similar to what we’ve seen on the airline side,” said Greeley Koch, executive director of the Association of Corporate Travel Executives. “We’ve seen this happen in the past.”

Phocuswright’s Quinby agreed that additional mergers or acquisitions are more likely than not.

“I’m quite sure we’ve not seen the end of consolidation on the supply side,” he said. “I think you’re going to see other hotel chains look at consolidation as a way to compete with the combined Marriott-Starwood behemoth.”

Some of the objections from travelers stem from the way consolidation in the airline industry, which has left four carriers responsible for roughly 80 percent of United States air traffic, led to the erosion of mileage values and statuses.

Marriott is keenly aware that the new guests it is bringing into the fold are skeptical of its intentions. In a video provided by a spokesman, Marriott’s chief executive, Arne Sorenson, sought to reassure guests, especially SPG members, that they would not be lost in the shuffle.

“The SPG program was one of the most attractive aspects of our acquisition of Starwood,” Sorenson said in the two-minute message, saying the company wanted to preserve the best aspects of both SPG and Marriott Rewards. “Devaluing points or member benefits is not the way to preserve and strengthen these programs.”

Bjorn Hanson, divisional dean of the Preston Robert Tisch Center for Hospitality, Tourism and Sports Management at New York University, said hotel mergers are unlikely to create the loyalty program depreciation that elicited gripes from frequent fliers because of the way hotel loyalty programs are financed.

In frequent-flier programs, airlines foot the bill for traveler benefits, giving them a financial incentive to pare down perks after consolidation. Hotels are financed and managed differently, in that Marriott and Starwood do not actually own the majority of hotels that bear their brand names. Franchisees like real estate investment trusts own the buildings and pay into a pool of funds that finances the guest loyalty program.

“It’s much different in the hotel industry,” than when two airlines merge, said Dan Wasiolek, senior equity analyst for Morningstar.

Loyalty program members might even be happily surprised, Hanson suggested. “There’s a better than 50 percent chance that the programs will be merged with the most favorable of both available to travelers,” he said.

© 2015 The New York Times Company