WYOMING — Vegetation ecologists monitoring the latest mountain pine beetle epidemic fear for the survival of the Teton Range’s remaining ancient whitebark pine stands. A keystone species that gained Endangered Species Act protections early this year, whitebark pines were hit hard by a plague of mountain pine beetles that spanned from 2004 to 2012. A cold snap ended that wave, giving the region’s embattled whitebark pine a temporary reprieve. Four years ago, however, scientists monitoring the gnarled high-elevation conifers started to see a larger concentration of “brood trees” harboring increasing numbers of the bark-boring insects. “It’s just another beetle epidemic happening because they are not being slowed down by cold falls and springs — like they naturally were before,” said Nancy Bockino, a Northern Rockies Conservation Cooperative whitebark pine field ecologist. “And it’s getting worse.”