The entomologist R. C. L. Perkins pioneered observations of breeding
site ecology for the endemic Hawaiian Drosophilidae, a renowned group of flies
that has undergone explosive speciation and adaptive radiation into a wide variety
of breeding niches. Females of the various species groups and subgroups oviposit
their eggs in either fungi, flowers, fruits, leaves, stems, bark, sap fluxes, or other
novel substrates. Varied selective forces in these alternative breeding sites have
apparently molded female reproductive characters and strategies into diverse outcomes;
some species mature and oviposit only one egg at a time, whereas others
oviposit hundreds. Here, we have analyzed the pattern of shifts in breeding substrate,
and the associated evolution of selected ovarian, egg, and ovipositor traits, by
mapping the various ecological and female reproductive character states on an
independently derived phylogenetic hypothesis based on nuclear and mitochondrial
DNA sequences. This comparative phylogenetic approach demonstrates a number
of strong historical associations among female reproductive traits and between
particular traits and the breeding substrate, although the overall pattern is complex
and more data are needed. Identification of certain apomorphic traits associated
with shifts in breeding substrate suggests an adaptational origin for some of the
changes in egg load per fly, in the length of the respiratory filaments of the egg,
and in the length and shape of the ovipositor. Although these hypotheses need further
testing, it appears that the ecological diversification in breeding substrates has been
an integral component in the radiation of drosophilids in Hawai'i