Abstract
This research presents evidence showing that: (1) lower arthropod herbivory correlates with seedling survival, and (2) spider presence correlates with lower arthropod herbivory, seedling growth, and seedling survival of the tropical rainforest tree species Dipteryx oleifera in eastern Nicaragua. The study was conducted from January 2005 to January 2006 in a 6.37 ha permanent plot established in 2002. Seedling height, spider behavior and presence on seedlings, and percentage of leaf area lost due to arthropod herbivory were measured. Arthropod herbivory was assessed from digital photographs of each seedling within the permanent plot. Seedling fate was followed in order to determine its correlation with spider presence, initial seedling size, and arthropod herbivory. A GLM showed that seedling survival correlated negatively with lower levels of arthropod herbivory (<20%), while seedlings with higher levels of herbivore damage experienced mortalities close to 100%. Results from another GLM suggests that seedling mean height (aprox. 8 cm) would be increased by approximately 1.5 cm for each year that spiders were present on seedlings and would be decreased 0.75 cm in height for each percent unit of arthropod herbivory. We also report a trend toward lower arthropod herbivory in seedlings colonized by spiders with aggressive traits, presumably because more aggressive spiders better defended seedlings against herbivorous arthropods than less aggressive spiders.
Highlights
Foliar herbivory damage can negatively affect seedling (Coley 1983, Dirzo 1987, Coley 1990), and can be severe enough to determine seedling fate (Sullivan 2003)
There is a tend towards lower arthropod herbivory damage in seedlings with “selfdefensive” spiders and more so in seedlings that harbored spiders with “aggressive” traits (F2,701 = 2.65, p
For seedlings with spiders present and herbivory damage, growth was positively correlated with spider presence and negatively correlated with arthropod herbivory damage
Summary
Foliar herbivory damage can negatively affect seedling (Coley 1983, Dirzo 1987, Coley 1990), and can be severe enough to determine seedling fate (Sullivan 2003). Since low levels of insect herbivory are omnipresent at the forest floor, more research is needed in order to determine which factor is responsible for seedling transition to larger size stages (Clark & Clark 1985, Ruiz et al 2009). In this communication we evaluate the ecological role that predatory spiders could play in seedling recruitment dynamics if their presence leads to lower arthropod herbivory and higher seedling survival. We tested the null hypotheses that seedling performance (survival and growth) is independent of arthropod herbivory and the presence of spiders
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