  We analyze the distribution of extrasolar planets (both confirmed and Kepler
candidates) according to their orbital periods P and planetary radii R. Among
confirmed planets, we find compelling evidence for a paucity of bodies with 3 <
R < 10 R_\oplus, where R_\oplus in the Earth's radius, and P < 2-3 days. We
have christened this region a "sub-Jovian Pampas". The same trend is detected
in multiplanet Kepler candidates. Although approximately 16 Kepler
single-planet candidates inhabit this Pampas, at least 7 are probable false
positives (FP). This last number could be significantly higher if the ratio of
FP is higher than 10%, as suggested by recent studies.
  In a second part of the paper we analyze the distribution of planets in the
(P,R) plane according to stellar metallicities. We find two interesting trends:
(i) a lack of small planets (R < 4 R_\oplus) with orbital periods P < 5 days in
metal-poor stars, and (ii) a paucity of sub-Jovian planets (4 R_\oplus < R < 8
R_\oplus) with P < 100 days, also around metal-poor stars. Although all these
trends are preliminary, they appear statistically significant and deserve
further scrutiny. If confirmed, they could represent important constraints on
theories of planetary formation and dynamical evolution.
