  We report the first measurement of genus curves for the two-dimensional mass
map in the neighborhood of rich, X-ray luminous galaxy cluster MS1054-03 at
z=0.83, reconstructed from weak lensing data obtained by Suprime-Cam on the
prime focus of 8.2m Subaru telescope. We find that the genus curve measured in
the whole survey field deviates from that expected from a random Gaussian
field. We show that this non-Gaussianity is induced by the rich cluster in this
region, and that the genus curve for the region without the cluster is
consistent with the prediction for a random Gaussian field. The results
demonstrate the feasibility of the genus statistics to examine the
non-Gaussianity due to the large scale structures and to probe the statistical
properties of the large scale clustering.
