Endemic species: Contribution to community uniqueness, effect of habitat alteration, and conservation priorities

► 65% of the 46 Texas Unionidae were rare and very rare, including all endemics. ► Endemic species defined the uniqueness of unionid communities. ► Unionid diversity was twice higher in natural lotic than in man-made lentic waters. ► Almost all endemics were found exclusively in lotic waters. ► Water alteration homogenizes communities favoring common and reducing rare species.