#Read in Tree use Bio::TreeIO; 
my $treeio = Bio::TreeIO->new(-format => 'newick',-file => $filename);
my $tree = $treeio->next_tree;

#You can find the species of interest ‘x'
foreach my $id(@lines){
    my $node = $tree->find_node(-id => $id);
    #Find internal node that is its immediate ancestor
    my $ancestral_node = $node->ancestor();
    #Find all descendants from ancestor (which will include ‘x’)
    for my $child ( $ancestral_node->get_all_Descendents ) {
        print $child->id, "\n";
    }
}