A new picture-winged Hawaiian Drosophila species from the
islands of Kaua'i and O'ahu that is morphologically indistinguishable from
Drosophila grimshawi Oldenberg from the Maui Nui islands is described, based
on differentiation in ecological, behavioral, cytological, and molecular characters
as well as ultrastructural features of the chorion. The new species, D. craddockae,
and D. grimshawi represent the first clear case of an allopatric sibling
species pair among Hawaiian Drosophilidae (i.e., there is strong evidence for a
profound set of intrinsic, genetically determined differences that are not easily
diagnosable by the usual morphological methods). Ecologically, D. craddockae
is a strict specialist, with oviposition restricted to the decaying bark of Wikstroemia.
Drosophila grimshawi, on the other hand, is a generalist that breeds
in the decaying parts of 10 families of plants. Data from cytological, behavioral,
and molecular analyses are consistent with the geological evidence that
species on the older islands are usually more ancestral than those that evolved
on the younger islands. Thus, although long-standing ecological theory states
that specialization is a derived condition, the biological and genetic evidence
all indicate that specialism in D. craddockae is the ancestral condition and that
generalism evolved in D. grimshawi on Maui Nui as a derived trait
