For my story I am working on, a peaceful alien race that is studying Earth wants to terraform the Moon by building a giant sealed dome over its entire surface, then they will create forests, deserts and oceans. Then they're going to import animals from Earth to the Moon's newly terraformed surface. Would animals be able to reproduce and survive in this environment? The gravity of the Moon is unchanged. If they are surviving and reproducing after many generations would they evolve to look different from what they originally looked like?
Working from what we know of the effects of reduced gravity on human animals (actually, astronauts) and this mainly in micro-gravity conditions, we can extrapolate to less human animals and livestock living under the one-sixth g conditions on a roofed-over Moon.
Most of the primary effects aren't too good They include muscular dystrophy, loss of bone density leading to osteoporosis, cardio-vascular problems, and negative impact on their balance. For animals living out their entire lives under lunar gravity this will lead to animals with chronic ill health.
There will be probable with radiation. The Moon lacks Earth's protective atmosphere and magnetic field, so high-energy particles including solar and galactic cosmic rays and increased UV and x-rays will deliver increased radiation exposure. While the roofing materials and the air under it will provide some protection from radiation they won't be able to shield it all. Perhaps your friendly aliens could install a hypertechnological radiation deflector.
The Moon doesn't have the same day-night cycle as planet Earth. Days and nights last two weeks on the Moon. This will disrupt the circadian of introduced animals.
For animals which have evolved to move around under Earth's gravity, many species will have difficulty adjusting to gravity where every step sending them pogo-sticking but sans pogo-stick across the moonscape. Arboreal species will probably be at an advantage. Koala bears and possums, especially glider possums, might enjoy their lunar ease of mobility in any transplanted eucalyptus trees.
However, the sum total of physiological problems will stress the animals and this will make reproduction difficult and there will possibly be a lot of stillbirths and miscarriages. A high proportion of live births may have additional problems. Weaker bones, blood circulation issues, and cardio-vascular stress will be endemic.
The possibility of long-term adaptation is an open question. One thing is obviously if the animals do adapt to lunar conditions, it will nigh on impossible to repatriate them and especially their descendants to Earth. Evolution shows adaptation is possible, in the long run, but for short and medium term that adaptation will come at a high cost. A large fraction of the animals will suffer chronic health problems.
Perhaps if your friendly aliens have the knowledge and where-withall they might practice genetic engineering and ue biotechnological techniques on the introduced livestock to accelerate their adaptation to the Moon. In fact, if the peaceful aliens don't do that biotechnological remediation, this would constitute a colossal act of animal cruelty and there are laws against that. If they removed animals from my country without doing something to enable the animals to cope with lunar conditions, the aliens would be taken to court for animal cruelty. There's a story in that alone to make this more than just an interesting scenario.