The biotech ecosystem looks healthy moving into 2013. With the space above $1 billion more than replenished in 2012, mid-cap names have money to create their own tier-jumping stories this year, while investors see natural selection plucking winners from the small and micro-cap spaces.

Fund managers suggest the run-up in large caps could lead to a rotation of investment into lower market cap tiers, fueling the cycle of replenishment necessitated by take-outs like Amylin Pharmaceuticals Inc. and Human Genome Sciences Inc.