Drosophila grimshawi

Magnacca, Karl N., Foote, David & O’Grady, Patrick M., 2008, A review of the endemic Hawaiian Drosophilidae and their host plants, Zootaxa 1728, pp. 1-58: 27-28

publication ID

http://doi.org/ 10.5281/zenodo.274194

persistent identifier

http://treatment.plazi.org/id/01205760-B933-0B66-FF3B-FDFEFB68FBB2

treatment provided by

Plazi

scientific name

Drosophila grimshawi
status

 

grimshawi  clade

With 77 species, the grimshawi  clade accounts for the bulk of picture wing species. It is also the most diverse in host usage, comparable to the modified mouthparts clade. On a finer scale, however, more specificity emerges. Within each species subgroup, a relatively small number of host shifts appears to have taken place ( Table 5; to avoid confusion with the larger clade, their “ grimshawi  subgroup” is referred to here as the crucigera  subgroup). For example, 12 of the 17 orphnopeza  subgroup species are from either Agavaceae  or Araliaceae  , including one oligophagous species that uses both; species of the vesciseta  subgroup use only Amaranthaceae  , Nyctaginaceae  , or Urticaceae  ; the odontophallus  subgroup is exclusively on Agavaceae  ; and monophagous species of the crucigera  subgroup use only Pandanaceae  or Thymelaeaceae  . The low overlap in host families between subgroups implies that specialization on a host plant may have played a major  role in the early diversification of the picture wing clade. This is in contrast to the AMC clade, where little hostswitching has taken place across the whole group, and the modified mouthparts group, where the dissita  and quadrisetae  subgroups show no clear pattern of host usage. The lack of a detailed species-level phylogeny such as exists for the planitibia  group ( Bonacum, et al., 2005), and numerous confounding shifts to rarer hosts such as Nyctaginaceae  and Sapindaceae  , preclude further speculation on evolution of host usage among the grimshawi  subgroups.

species complex  a data species

ecological

with polyphagous y n Agavaceae  Amaranthaceae  Araliaceae  Fabaceae  Myoporaceae  Nyctaginaceae  Pandanaceae  Sapindaceae  Thymelaeaceae  Urticaceae  / oligophagous

crucigera  8 1 3 2 3 hawaiiensis  9 5 3 3 1 2 odontophallus  4 4 orphnopeza  17 2 2 9 1 1 1 3 punalua  5 3 1 2 1 1 vesciseta  11 5 5 2 3 1

a The discreta  and distinguenda  subgroups are not shown since rearing data is only available for one species from each.

Despite the wide diversity of host families used by the grimshawi  clade, the only substrate shift has been from stems and bark proper to sap flux in the hawaiiensis  subgroup. The latter is a similar habitat that is sometimes used by other picture wing species, particularly in the orphnopeza  subgroup. Only two species commonly use other substrate types: D. punalua  will sometimes use the fruit and leaves of Freycinetia  in addition to the stems, and D. crucigera  , a highly polyphagous species, will also use fruit.

The most striking aspect of the breeding records for the grimshawi  clade is not so much the variety of host families that are used, as one that is not: Campanulaceae  . This is considered one of the most important hosts for Hawaiian drosophilids in general, but especially for the other clades ( adiastola  and planitibia  ) in the picture wing group. Yet there are almost no records for the family in the grimshawi  clade; in addition to four polyphagous species ( D. crucigera  , D. disjuncta  , D. grimshawi  , and D. villosipedis  ), there are only 4 records from 2 species ( D. limitata  and D. murphyi  ), and even these may be incidental. The near-absence of such a significant host from this large, highly host-variable group is remarkable, and warrants further investigation.

Araliaceae  , particularly the genus Cheirodendron  , is another very common host plant for Hawaiian Drosophilidae  . While there are several records of grimshawi  clade species using Araliaceae  , nearly all are confined to the orphnopeza  subgroup, the same 4 polyphagous species mentioned above, and scattered incidental records. Of those species that do use Araliaceae  , 80 % have been reared from either Tetraplasandra  or Reynoldsia  (see Appendix 1), often in lowland and/or relatively dry habitats. In contrast, none of the 240 Araliaceae  records from the AMC and modified mouthparts clades are from Reynoldsia  and only 22 (9 %) are from Tetraplasandra  , and all but one are from montane wet locations.

In general, the species of the grimshawi  clade tend to favor more mesic to dry forest plants: Acacia  , Charpentiera  , Myoporum  , Pisonia  , Pleomele  , Reynoldsia  , Sapindus  , Tetraplasandra  , Urera  , and Wikstroemia  . Although many of these live in wet forest as well, it appears likely that the grimshawi  clade evolved as a mesic assemblage, perhaps as sister to the nudidrosophila and ateledrosophila groups. It is perhaps not so surprising then that the characteristic plants of the wet forest – Cheirodendron  , Clermontia  , and Cyanea  – are lacking from their diet, especially when these plants are already heavily utilized by other picture wings.

AMC

Department of Biologics Research