9700834 Power Population and community dynamics in one habitat (compartment) are often strongly linked to dynamics in separate but adjacent habitats. In this way, one habitat may in effect, subsidize certain organisms in a second habitat. Several recent empirical studies suggest that spatial subsidies lead to inflated population densities or altered interaction strengths of organisms in recipient habitats. In river ecosystems, the export of winged adults of aquatic insects may be a cross-compartmental link, subsidizing watershed consumers and altering their community dynamics. In rivers of northern Califomia, lizards (Sceloporus, Iguanidae) are at least seven times more dense than congeners in non-river, upland habitats. On the same rivers, the abundance of aerial invertebrates declines nearly exponentially with increasing distance from the river-land interface. Sceloporus eat primarily terrestrial invertebrates, but 5-25% of the insects in their diet are of aquatic origin. The ability of Sceloporus to track aquatic resources may be limited by cover availability near rivers. The PIs propose to investigate 1) the effect of riverine subsidies of aquatic insects on Sceloporus population and community dynamics and 2) how near-river cover availability may modulate the ability of Sceloporus to track these resources.
