U.S. Auto Parts Network Inc. has consolidated its position as America’s dominant online auto parts distributor by acquiring its smaller, more specialized rival.

The Carson company announced last week that it was buying Whitney Automotive Group, a Chicago-based online distributor of auto accessories, for $27.5 million plus the assumption of about $11 million in debt.

“This is a great acquisition for a strong company, providing them large growth opportunities for the future,” said Jared Schramm, a research analyst with Roth Capital Partners in Newport Beach, which follows the company.

The acquisition, announced Aug. 2, drove the company’s share price up 21 percent by the end of the week to $8.11 per share.

Chief Executive Shane Evangelist said the move is part of a strategy that began when the company first went online in 2000, primarily as a distributor of auto body parts to local retailers.

Six years later, Auto Parts Network acquired a company called Parts Bin to expand its catalog into engine parts, including brakes, water pumps and catalytic converters.

The most recent acquisition thrusts the company more deeply into accessories – products designed to make cars look better or last longer, including floor mats, lift kits and car covers – a market that previously accounted for only 10 percent of sales.

“Now accessories are our single biggest category,” said Evangelist. The acquisition should boost accessory sales to about 37 percent the company’s total.

Accessories have higher profit margins and should help insulate the company from market swings between sales associated with new-car purchases during good times and engine parts purchased to keep older cars on the road during downturns.

“What this does is give us a natural hedge in our product mix,” Evangelist said.

The company reported lackluster second quarter earnings the same day it announced the acquisition. Net income fell to $462,000 from $629,000 a year ago, even as revenue rose 22 percent to $53.2 million.