Diapause and cold tolerance inAsian species of the parasitoidLeptopilina(Hymenoptera:Figitidae)

Abstract

Diapause and cold tolerance are essential for temperate insects to pass the winter, with the mechanisms controlling these two traits varying considerably among insects. In the present study, diapause and cold tolerance are compared among three Leptopilina species: Leptopilina japonica Novković & Kimura, Leptopilina victoriae Nordlander and Leptopilina ryukyuensis Novković & Kimura, all larval parasitoids of frugivorous drosophilid flies, with the aim of understanding their climatic adaptations. The first species is divided into the temperate (Leptopilina japonica japonica) and subtropical subspecies (Leptopilina japonica formosana), and the latter two species are distributed in the tropical and subtropical regions. The temperate subspecies of L. japonica enters prepupal diapause at low temperatures (15 or 18 °C), irrespective of photoperiod, and some individuals enter diapause when exposed to 0 °C for 1 or 2 day(s) or when placed at low humidity. Leptopilina victoriae also shows signs of diapause initiation at 15 °C, although L. ryukyuensis and L. j. formosana from the subtropical regions do not. Preimaginal viability at low temperature (13, 14 or 15 °C) is usually lower in L. victoriae from the tropical regions compared with L. japonica or L. ryukyuensis from the temperate or subtropical regions. Diapausing prepupae of the temperate subspecies appear to be cold tolerant. However, the cold tolerance of nondiapausing prepupae, pupae and adult females varies little among the tropical, subtropical and temperate species or subspecies, and adult males of the temperate subspecies of L. japonica are less cold tolerant than those of the tropical or subtropical species or subspecies. Cold tolerance may be unnecessary, except for diapausing individuals of the temperate species, because nondiapausing individuals appear in warmer seasons.

First Report of Leptopilina japonica in Europe

“…Leptopilina japonica is a solitary koinobiont endoparasitoid, consisting of two subspecies, L. japonica japonica Novković and Kimura present in Northern and Central Japan and L. japonica formosana Novković and Kimura occurring in Taiwan [ 67 ]. These subspecies seem to have distinct characteristics in terms of behavioral ecology [ 62 , 67 , 72 ]. Based on morphological and molecular identification, our specimens could be associated with L. j. japonica subspecies.…”

Overwintering of reproductively mature females of a pro‐ovigenic parasitic wasp, Leptopilina heterotoma (Hymenoptera: Figitidae)

“…In contrast, L. boulardi, L. japonica and L. longipes enter diapause at the prepupal stage for overwintering (Claret & Carton ; Carton & Claret ; Murata et al . ; M. T. Kimura, unpubl. data, 2015).…”

“…Another Leptopilina species, L. japonica Novković & Kimura and L. longipes (Hartig), also enter prepupal diapause (Murata et al . ; M. T. Kimura, unpubl. data, 2015), although it has not been studied whether they are pro‐ovigenic or nor.…”

“…In fact, another proovigenic species Leptopilina boulardi Barbotin, Carton & Kelner-Pillaut has been reported to enter prepupal diapause (Claret & Carton 1980;Carton & Claret 1982;Kopelman & Chabora 1986. Another Leptopilina species, L. japonica Novkovi c & Kimura and L. longipes (Hartig), also enter prepupal diapause (Murata et al 2013;M. T. Kimura, unpubl.…”

Taxonomy and evolution of putative thelytokous species of Leptopilina (Hymenoptera: Figitidae) from Japan, with description of two new species

“…The first three species form a monophyletic lineage in the phylogenetic trees based on the COI gene and ITS2. Among them, L. japonica is adapted to temperate climates, while L. ryukyuensis and L. victoriae are adapted to tropical and subtropical climates (Murata et al 2013). Leptopilina pacifica is an oriental species occurring in the subtropical and tropical regions of Asia as well as L. ryukyuensis (Novković et al 2011).…”