God creates from nothing and God allows evolution within what He creates.
Here are some references:

[i:21ttmndt]In the Catholic perspective, neo-Darwinians who adduce random genetic variation and natural selection as evidence that the process of evolution is absolutely unguided are straying beyond what can be demonstrated by science Divine causality can be active in a process that is both contingent and guided. Any evolutionary mechanism that is contingent can only be contingent because God made it so. An unguided evolutionary process ‚Äì one that falls outside the bounds of divine providence ‚Äì simply cannot exist because”the causality of God, Who is the first agent, extends to all being, not only as to constituent principles of species, but also as to the individualizing principles….It necessarily follows that all things, inasmuch as they participate in existence, must likewise be subject to divine providence” (Summa theologiae I, 22, 2). [/i:21ttmndt]
Source[/url:21ttmndt]

[i:21ttmndt]”…..Likewise related is the “design” of the plan. God not only is the Maker of all; He is also the maintainer of His creation, directing it to its goal. ………God is not only a creator who at the beginning set the work in motion, like a watchmaker who has fashioned a time-piece that will tick on forever. Rather, he preserves and guides it towards its goal. The Christian faith further teaches that the creation is not yet complete, that it is in statu viae, in transit. God as Creator of the world is also its guide. We call this “providence” (Vorsehung). We are convinced that all of this – that there is a Creator and a guide – can also be perceived and recognized by us. Christian belief decidedly and tenaciously clings to the human capacity to discern both these divine aspects, though certainly neither in toto nor in every detail. [/i:21ttmndt]
http://www.kath.net/detail.php?id=12028

[i:21ttmndt]Within the teaching about evolution itself, the problem emerges at the point of transition from micro to macro-evolution, on which point Szathmary and Maynard Smith, both convinced supporters of an all-embracing theory of evolution, nonetheless declare that: “There is no theoretical basis for believing that evolutionary lines become more complex with time; and there is also no empirical evidence that this happens.”
The question that has now to be put certainly delves deeper: it is whether the theory of evolution can be presented as a universal theory concerning all reality, …….I do not think so. . In the end this concerns a choice that can no longer be made on purely scientific grounds or basically on philosophical grounds. [/i:21ttmndt]Pope Benedict XVI
http://www.zenit.org/english/visualizza.phtml?sid=75841