Thermal plasticity of growth and development varies adaptively among alternative developmental pathways

Abstract

Polyphenism, the expression of discrete alternative phenotypes, is often a consequence of a developmental switch. Physiological changes induced by a developmental switch potentially affect reaction norms, but the evolution and existence of alternative reaction norms remains poorly understood. Here, we demonstrate that, in the butterfly Pieris napi (Lepidoptera: Pieridae), thermal reaction norms of several life history traits vary adaptively among switch-induced alternative developmental pathways of diapause and direct development. The switch was affected both by photoperiod and temperature, ambient temperature during late development having the potential to override earlier photoperiodic cues. Directly developing larvae had higher development and growth rates than diapausing ones across the studied thermal gradient. Reaction norm shapes also differed between the alternative developmental pathways, indicating pathway-specific selection on thermal sensitivity. Relative mass increments decreased linearly with increasing temperature and were higher under direct development than diapause. Contrary to predictions, population phenology did not explain trait variation or thermal sensitivity, but our experimental design probably lacks power for finding subtle phenology effects. We demonstrate adaptive differentiation in thermal reaction norms among alternative phenotypes, and suggest that the consequences of an environmentally dependent developmental switch primarily drive the evolution of alternative thermal reaction norms in P. napi.

Local adaptation of photoperiodic plasticity maintains life cycle variation within latitudes in a butterfly

“…4c, d). Temperature effects on diapause induction occur in many (but not all) photoperiodic insects, with high temperature either averting diapause irrespective of day length (Kivel€ a et al 2015) or, as here, modulating the CD (Beck 1980, Numata et al 1993, Vaz Nunes et al 1996. Although the overall effect on the simulation results is small (Table 1), it lends tentative support to the idea, put forth, e.g., by Hayes (1982), that such temperature effects can help maintain voltinism variation within latitudes.…”

Idiosyncratic development of sensory structures in brains of diapausing butterfly pupae: implications for information processing

“…Diapause is initiated in larvae in response to shortening day length [13,14]. Whereas pupal development without diapause generally lasts about two weeks, pupal diapause may last two to six months [15].…”

Developmental plasticity in metabolism but not in energy reserve accumulation in a seasonally polyphenic butterfly

“…This is because the penultimate instar is the typical time window during which the developmental pathway is induced in P. napi (Friberg et al, 2011), resulting in a limited post-induction period for phenotypic divergence to become apparent in the penultimate instar. Putting these results together with the observation that the inter-pathway difference in development time became more pronounced in the final larval instar and the fact that the induction of a developmental pathway is largely independent of rates of growth and development in P. napi (Friberg et al, 2012; Kivelä et al, 2015), a high metabolic rate seems associated with fast growth and rapid development in individuals set for direct maturation after the induction of the developmental pathway. A high metabolic rate may be the cause for a high growth rate, or vice versa (Glazier, 2015).…”

“…Here, we address potential pre-diapause physiological divergence between the diapause and direct development pathways by using the green-veined white butterfly Pieris napi (Linnaeus) as study system. Pieris napi produces at least two generations per year in a large part of its Palearctic distribution (Wiklund et al, 1991; Tolman and Lewington, 2002; Kivelä et al, 2015). It overwinters exclusively as a pupa, but the induction of the developmental pathway takes place during the penultimate larval instar in response to photoperiod and temperature (Friberg et al, 2011).…”

“…It overwinters exclusively as a pupa, but the induction of the developmental pathway takes place during the penultimate larval instar in response to photoperiod and temperature (Friberg et al, 2011). Individuals following the diapause and direct development pathways have different life histories, including a shorter larval development time under direct development than diapause (Wiklund et al, 1991; Friberg et al, 2011; Kivelä et al, 2015). However, we do not know whether the relatively high rates of development and growth under direct development are associated with a high metabolic rate, and whether metabolic rate diverges between the diapause and direct development pathways at the same time as the divergence in development and growth rate appears.…”