  A square lattice is introduced into the Penna model for biological aging in
order to study the evolution of diploid sexual populations under certain
conditions when one single locus in the individual's genome is considered as
identifier of species. The simulation results show, after several generations,
the flourishing and coexistence of two separate species in the same
environment, i.e., one original species splits up into two on the same
territory (sympatric speciation). As well, the mortalities obtained are in a
good agreement with the Gompertz law of exponential increase of mortality with
age.
