Host plants are used by herbivorous insects as feeding or nesting resources. In
wood-boring insects, host plants features may impose selective forces leading to
phenotypic differentiation on traits related to nest construction. Carpenter bees
build their nests in dead stems or dry twigs of shrubs and trees; thus, mandibles
are essential for the nesting process, and the nest is required for egg laying and
offspring survival. We explored the shape and intensity of natural selection on
phenotypic variation on three size measures of the bees (intertegular width,
wing length, and mandible area) and two nest architecture measures (tunnel
length and diameter) on bees using the native species Chusquea quila (Poaceae),
and the alloctonous species Rubus ulmifolius (Rosaceae), in central Chile. Our
results showed significant and positive linear selection gradients for tunnel
length on both hosts, indicating that bees building long nests have more offspring.
Bees with broader mandibles show greater fitness on C. quila but not
on R. ulmifolius. Considering that C. quila represents a selective force on mandible
area, we hypothesized a high adaptive value of this trait, resulting in