title: Counterintuitive size patterns in bivoltine moths: late-season larvae grow larger despite lower food quality.
abstract: Within a season, successive generations of short-lived organisms experience different combinations of environmental parameters, such as temperature, food quality and mortality risk. Adult body size of e.g. insects is therefore expected to vary both as a consequence of proximate environmental effects as well as adaptive responses to seasonal cues. In this study, we examined intraspecific differences in body size between successive generations in 12 temperate bivoltine moths (Lepidoptera), with the ultimate goal to critically compare the role of proximate and adaptive mechanisms in determining seasonal size differences. In nearly all species, individuals developing late in the season (diapausing generation) attained a larger adult size than their conspecifics with the larval period early in the season (directly developing generation) despite the typically lower food quality in late summer. Rearing experiments conducted on one of the studied species, Selenia tetralunaria also largely exclude the possibility that the proximate effects of food quality and temperature are decisive in determining size differences between successive generations. Adaptive explanations appear likely instead: the larger body size in the diapausing generation may be adaptively associated with the lower bird predation pressure late in the season, and/or the likely advantage of large pupal size during overwintering.
authors.affiliation: Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia. tiit.teder@ut.ee
authors.forename: Tiit
authors.initials: T
authors.lastname: Teder
authors.forename: Toomas
authors.initials: T
authors.lastname: Esperk
authors.forename: Triinu
authors.initials: T
authors.lastname: Remmel
authors.forename: Anu
authors.initials: A
authors.lastname: Sang
authors.forename: Toomas
authors.initials: T
authors.lastname: Tammaru
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D049628:Body Size; D005247:Feeding Behavior; D007814:Larva / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology; D009036:Moths / Q000033:anatomy & histology / Q000254:growth & development* / Q000502:physiology; D012621:Seasons; D013312:Stress, Physiological; D013696:Temperature