|In the selection of reserve networks there are special sites whose ecologic, strategic or morphologic
values dictate their inclusion. The existence of regional rare or confined-distribution
species is one among other reasons that often determines the existence of such
mandatory sites. Moreover, quite often these mandatory sites are located far apart.
Although several methods have been proposed to accommodate structural connectivity
in reserve selection, they were not devised to deal specifically with such mandatory sites.
Those that encourage aggregation of sites by means of criteria incorporated in the objective
function do not seem suitable to acquire consistent connectivity levels in the presence of
mandatory sites. Methods that enforce ‘‘full connectivity’’ tend to produce long and narrow
solutions, which results in efficiency deficits and biological unsuitability, as they force the
selection of more sites of less quality to ensure connectivity. Hence specific methods to
select ecological reserves when mandatory sites exist are needed. Here we discuss and propose
a 0–1 linear programming model to deal with this issue. The model was applied in two
data sets of forest breeding birds and butterflies. Its solutions and computational performances