Such a fact would be considered quite silly. Dugtrio has no connections with the sun or light energy at all, yet it can learn Sunny Day. Dugtrio has connections with the sand as it lives in burrows underground and could easily twist the earth for a sandstorm. I must state that Dugtrio receives no great bonus even with access to Sandstorm. It won't last long enough to abuse the hax that Sandstorm provides (one hit brings it down), and thus more commonly used as a full out offensive sweeper. In competetive battling, manually handling Sandstorm as a moveslot is rare, as most Sandstorm teams use Tyranitar to whip up a Sandstorm.