FromtheCover.PDF

March 20, 2012 u vol. 109 u no. 12 u 4337–4708 Cover image: Pictured is the fertilization duct of a female diving beetle, revealing the sperm inside. Dawn M. Higginson et al. found that the female reproductive tracts of diving beetles have undergone extensive diversification, with changes in size and shape associated with variations in sperm morphology and conjugation. The findings suggest that female reproduc- tive tract design drives the evolution of a variety of complex sperm forms, and highlights the importance of postcopulatory sexual selection as an agent of diversification. See the article by Higginson et al. on pages 4538–4543. Image courtesy of Dawn M. Higginson. From the Cover 4538 Evolution of complex sperm morphology 4383 Self-healing synthetic materials 4515 Origins of hematopoietic stem cells 4556 Toxin resistance in snakes 4674 Circadian control of plant defenses Contents COMMENTARIES 4341 Complex sperm evolution