From the rules-as-written, it does not. Land speed had to be listed under the abilities granded by the spell. Otherwise you do not gain the ability.
From Beast Shape I:
When you cast this spell, you can assume the form of any Small or Medium creature of the animal type. If the form you assume has any of the following abilities, you gain the listed ability: climb 30 feet, fly 30 feet (average maneuverability), swim 30 feet, darkvision 60 feet, low-light vision, and scent.
From Transmutation (Polymorph):
In addition, each polymorph spell can grant you a number of other benefits, including movement types, resistances, and senses. If the form you choose grants these benefits, or a greater ability of the same type, you gain the listed benefit. If the form grants a lesser ability of the same type, you gain the lesser ability instead. Your base speed changes to match that of the form you assume. If the form grants a swim or burrow speed, you maintain the ability to breathe if you are swimming or burrowing.
However, these rules assume most characters using Beast Shape are either humanoids or land-based creatures. I even had some difficulty figuring out how a caster character could not have a land speed to begin with, as most flying creatures do have a land speed, and most aquatic creatures intelligent enough to be spellcasters have at least a 5 feet base land speed.
Though the Symbiosis abilities does not cast Beast Shape, the spell does have all the text from polymorph subschool as part of it's effect. Those rules are separated so designers can save space on the book and not have the same rule repeating all over the place. Specially if you consider that it says "each polymorph spell can [...]".
Taking that into consideration, all three forms of speed granted by Beast Shape (fly, swim and climb) are considered fairly stronger than a land speed as a special ability, but I won't enter into details why, it should be obvious.
For instance, if a triton druid turned into a bear, he couldnt he walk on land? There isn't much sense on that. If land-walkers turned into sharks can swim freely, and he could fly if he turned into an eagle (which is fairly stronger than walking due to the 3D movement gained), why cripple the bear?
Also, you could argue that the base speed mentioned on the polymorph effect is actually talking about base land speed, as we have the text on nearly all humanoid races, talking about base speed meaning your actual base land speed. So it is safe to say that base speed is land speed.
That said, it is fair to assume that Beast Shape does grant a base land speed if the original creature could also walk on land.