Sperm competition and small size advantage for males of the golden orb-web spider Nephila edulis
نویسندگان
چکیده
Patterns of sexual dimorphism in dioecious organisms depend on the relative strengths of a variety of selection pressures (Andersson, 1994; Mùller, 1994). For example, selection may favour large female size if this ensures greater fecundity, parental care or dominance in contests over resources. Typically, sexual selection is thought to in ̄uence sexual size dimorphism in the context of female choice and/or male±male competition, and most studies have focussed on the bene®ts of large body size (Blankenhorn, 2000). Thus, large male body size may be favoured if females prefer larger males, or larger males dominate in physical contests over females (Andersson, 1994). Under conditions of scramble competition, sexual selection may favour small body size if smaller, early emerging males are more likely to ®nd females than later males (Andersson, 1994). However, multiple mating by females allows sexual selection to persist after mating has taken place (Mùller, 1998). If females store sperm from several mating partners, then these sperm may directly compete for fertilization inside the female. Numerous studies have identi®ed an extraordinary diversity of mechanisms by which males attempt to ensure that the eggs of their mating partners are not fertilized by rival males (see Birkhead & Mùller, 1998). However, the relationship between sperm competition and male body size is still poorly understood (Simmons & Siva-Jothy, 1998).
منابع مشابه
Discovery of the Largest Orbweaving Spider Species: The Evolution of Gigantism in Nephila
BACKGROUND More than 41,000 spider species are known with about 400-500 added each year, but for some well-known groups, such as the giant golden orbweavers, Nephila, the last valid described species dates from the 19(th) century. Nephila are renowned for being the largest web-spinning spiders, making the largest orb webs, and are model organisms for the study of extreme sexual size dimorphism ...
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