Do sperm really compete and do eggs ever have a choice? Adult distribution and gamete mixing influence sexual selection, sexual conflict, and the evolution of gamete recognition proteins in the sea

The evolution of gametic compatibility and the effectiveness of compatibility, within and across species, depend on whether sperm from different males directly compete for an egg and whether eggs ever have a choice. Direct sperm competition and egg choice depend on whether sperm from different males arrive at an egg in the brief interval between first sperm contact and fertilization. Although this process may be relevant for all sexually reproducing organisms, it is most easily examined in aquatic external fertilizers. When sperm are released into the sea, packets of seawater at the spatial scale relevant to single eggs might contain sperm from only one male, eliminating the potential for direct sperm competition and egg choice. Field experiments and a simple heuristic model examining the degree of sperm mixing for the sea urchin Strongylocentrotus franciscanus indicate that degree of competitive fertilization depends on density and distribution of competing males and that the nature of...配子相容性（gametic compatibility）的演化以及种内、种间相容性的有效性，取决于不同雄性的精子是否会直接竞争同一枚卵子，以及卵子是否具备选择的权利。直接精子竞争与卵子选择的发生，取决于不同雄性的精子是否会在首次接触卵子至完成受精之间的极短时段内抵达该卵子。尽管这一过程或对所有有性生殖生物均具有研究意义，但在水生体外受精生物中最易于开展相关研究。当精子被释放至海水中时，在与单枚卵子相关的空间尺度下，一团海水中可能仅存在单一雄性的精子，这将消除直接精子竞争与卵子选择的可能性。针对红海胆（Strongylocentrotus franciscanus）开展的野外实验与检验精子混合程度的简单启发式模型研究表明，竞争性受精的程度取决于竞争雄性的种群密度与分布模式，而其本质为……