Unlike Ancistrocarphus filagineus, A. keilii has no obvious dispersal mechanism. Its cypselae appear to germinate more or less in place from previous years’ plants, often producing dense, turflike growths of dozens to hundreds of individuals (these sometimes resemble leafy glomerules of heads; each head is on a separate plant with its own root). Lack of dispersal may explain its very limited geographic range in the Santa Ynez River drainage of Santa Barbara County. Its range does not appear to overlap with that of A. filagineus, which is found farther inland to the east and north. No other Filagininae have been found mixed with A. keilii, suggesting that its habitat is fairly distinctive.