Trade-offs in foraging success and predation risk with spatial position in colonial spiders

摘要: Colonial web-building spiders respond to trade-offs between selective forces relative spatial position within colonies and thus provide support for the selfish herd theory. The size distribution of Metepeira incrassata, a colonial orb-weaver (Araneae: Araneidae) from tropical Mexico is nonrandom; larger (mature) females guarding eggsacs are more prevalent in center, whereas small (immature) found on periphery. Experimental field studies with selected classes show that actively aggressively seek protected positions center colony webbing, even though prey availability capture rates significantly higher Attacks by predatory wasps, other spiders, hummingbirds frequent periphery than core colony. Reproductive at greater risk because they captured often smaller if their egg sacs consequently remain unguarded, chances cocoon parasitism increased. As result, have reproductive success, producing hatching frequency. appear be making trade-off foraging protection predation organization predicted influence such individual fitness structure discussed.