Hulsey C D, Mims M C, Streelman J T
School of Biology and Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Proc Biol Sci. 2007 Aug 7;274(1620):1867-75. doi: 10.1098/rspb.2007.0444.
Constraints on form should determine how organisms diversify. Owing to competition for the limited space within the body, investment in adjacent structures may frequently represent an evolutionary compromise. For example, evolutionary trade-offs between eye size and jaw muscles in cichlid fish of the African great lakes are thought to represent a constructional constraint that influenced the diversification of these assemblages. To test the evolutionary independence of these structures in Lake Malawi cichlid fish, we measured the mass of the three major adductor mandibulae (AM) muscles and determined the eye volume in 41 species. Using both traditional and novel methodologies to control for resolved and unresolved phylogenetic relationships, we tested the evolutionary independence of these four structures. We found that evolutionary change in the AM muscles was positively correlated, suggesting that competition for space in the head has not influenced diversification among these jaw muscles. Furthermore, there was no negative relationship between change in total AM muscle mass and eye volume, indicating that there has been little effect of the evolution of eye size on AM evolution in Lake Malawi cichlids. The comparative approach used here should provide a robust method to test whether constructional constraints frequently limit phenotypic change in adaptive radiations.
形态上的限制应该决定生物体如何多样化。由于身体内有限空间的竞争，对相邻结构的投入可能常常代表一种进化上的妥协。例如，非洲大湖丽鱼科鱼类眼睛大小和颌肌之间的进化权衡被认为代表了一种结构限制，这种限制影响了这些鱼类群体的多样化。为了测试马拉维湖丽鱼科鱼类中这些结构的进化独立性，我们测量了41个物种的三块主要下颌收肌（AM）的质量，并确定了眼睛体积。我们使用传统和新颖的方法来控制已解决和未解决的系统发育关系，测试了这四个结构的进化独立性。我们发现AM肌肉的进化变化呈正相关，这表明头部空间的竞争并未影响这些颌肌之间的多样化。此外，AM肌肉总质量的变化与眼睛体积之间没有负相关关系，这表明在马拉维湖丽鱼中，眼睛大小的进化对AM进化几乎没有影响。这里使用的比较方法应该提供一种可靠的方法来测试结构限制是否经常限制适应性辐射中的表型变化。
