Key‐factor/key‐stage analysis of long‐term life table data for a fruit gall midge, Asphondylia sphaera (Diptera: Cecidomyiidae)

Abstract

1. Population dynamics of Asphondylia sphaera Monzen (Diptera: Cecidomyiidae), a species that induces fruit galls on Ligustrum japonicum (Oleaceae), was studied from 1970 to 1996 in broad-leaved evergreen forests in Kagoshima, southern Japan. The numbers of fruit galls and emerging adults fluctuated greatly from year to year along with alternate year flowering of the host plant.2. To detect density-dependent and independent forces operating on the A. sphaera population and to assess the relative strength of top-down and bottom-up effects, we used the method of Key-factor/key-stage analysis, which allowed us to avoid various problems of the conventional key-factor analysis.3. Five factors and seven stages were distinguished in the life tables. Key-factor/key-stage analysis indicated that the number of flower buds made the largest contribution to the annual changes in total survival rate by operating through the proportion of eggs and first instars that survived abortion of host flower buds and flowers, which contributed most to density-dependency.4. The population dynamics of A. sphaera has been strongly influenced by the bottom-up effects of both the abundance of flower buds and the abortion of flowers of L. japonicum. 5. A top-down effect of Bracon asphondyliae Maeto (Hymenoptera: Braconidae) was weakly density-dependent and contributed less to the total survival rate. Abiotic factors, such as summer and winter temperatures and the effect of typhoons were negligible.

Ecological divergence among morphologically and genetically related Asphondylia species (Diptera: Cecidomyiidae), with new life history data for three congeners including the Alpinia fruit gall midge

“…Yukawa et al . ), we speculate that an oviposition mistake caused by asynchrony between gall midge emergence and host plant phenology or an extreme shortage of host plants could be the triggers, but we need actual field data to test these hypotheses.…”

“…Yukawa & Masuda ; Yukawa et al . ), and is distributed widely in Japan except Hokkaido and northern Honshu (e.g. Uechi et al .…”

“…Asphondylia sphaera is an oligophagous species, inducing fruit galls on Ligustrum japonicum Thunberg (Oleaceae) and its congeners (e.g. Yukawa & Masuda 1996;Yukawa et al 2016b), and is distributed widely in Japan except Hokkaido and northern Honshu (e.g. Uechi et al 2002).…”

“…Relative convenience in studying galls and miners has been emphasized on many occasions because of their outstanding features and immobility (e.g. Yukawa 2000;Stone & Schonrogge 2003;Sinclair & Hughes 2010;Yukawa et al 2016b).…”

Pseudasphondylia tominagai, a new gall midge species (Diptera: Cecidomyiidae) inducing flower bud galls on Eleutherococcus spinosus (Araliaceae) in Japan

“…In Diptera, the host-alternating habit has been known for only a few species of Asphondylia , such as A. gennadii (Marchal), A. yushimai Yukawa and Uechi, A. baca Monzen and A. sphaera Monzen (Harris 1975, Gagné and Orphanides 1992, Uechi et al 2005, Uechi et al 2004, Yukawa et al 2003, Yukawa et al 2016). Since Asphondylia and Pseudasphondylia belong to the same subtribe (Asphondyliina), they provide a great opportunity to study the evolutionary process of host-alternating habit by gall midges through molecular genetic analyses.…”