Phenology of Forest Caterpillars and Their Host Trees: The Importance of Synchrony

Abstract

For many leaf-feeding herbivores, synchrony in phenology with their host plant is crucial as development outside a narrow phenological time window has severe fitness consequences. In this review, we link mechanisms, adaptation, and population dynamics within a single conceptual framework, needed for a full understanding of the causes and consequences of this synchrony. The physiological mechanisms underlying herbivore and plant phenology are affected by environmental cues, such as photoperiod and temperature, although not necessarily in the same way. That these different mechanisms lead to synchrony, even if there is spatial and temporal variation in plant phenology, is a result of the strong natural selection acting on the mechanism underlying herbivore phenology. Synchrony has a major impact on the population densities of leaf-feeding Lepidoptera, and years with a high synchrony may lead to outbreaks. Global climate change leads to a disruption of the synchrony between herbivores and their host plants, which may have major impacts for population viability if natural selection is insufficient to restore synchrony.

Distinguishing between anticipatory and responsive plasticity in a seasonally polyphenic butterfly

“…However, it is rather straightforward to ascribe the small size of the individuals developing at the end of the season to an immediate effect of the suboptimal conditions they are faced with (e.g. Scriber and Slansky 1981;Van Asch and Visser 2007). This 438 study implies that this is not necessarily the case and therefore indicates that the adaptive nature of the seasonal polyphenism in body size in insects may have a rather universal character.…”

“…Indeed, the predictability of seasonally varying selective pressures, many of which are relatively straightforward to understand (Tauber et al 1986) 105 and even quantify (e.g. Rodrigues and Moreira 2004, Van Asch and Visser 2007, Remmel et al 2009) provides an opportunity to analyse the limits to adaptive plastic changes, and the degree to which organisms can evolve to cope with detrimental changes 108 in their environments.…”

“…the immediate effects of environmental factors. Indeed, host plant quality (Scriber and Slansky 1981;Schroeder 1986;Van Asch andVisser 2007, Nealis 2012) and sometimes also quantity (Ohgushi 1996;Rodrigues and Moreira 2004) have been shown to decline 129 towards the end of the season. Individuals with their larval period in spring are therefore expected to achieve larger adult sizes for this reason alone (Hahn and Denlinger 2007;Teder et al 2010).…”

Contrasting relations between diversity of candidate genes and variation of bud burst in natural and segregating populations of European oaks

“…An increase in the length of the growing season has already been observed for trees in Europe and North America (Menzel and Fabian, 1999;Penuelas and Filella, 2001). Changes in the date of bud burst will modify exposures to late frost (Scheifinger et al, 2003), or to outbreaks of phytophagous insects (Van Asch and Visser, 2007). The adaptive response of trees to these rapid climatic changes will depend on the levels of genetic variation within natural populations.…”

Phase-dependent outbreak dynamics of geometrid moth linked to host plant phenology

“…Jepsen et al 4125 season (Karlsson et al 2003;Shutova et al 2006;Pudas et al 2008), while the same temperature increase translates to a 7-10 days earlier onset of the growing season in oceanic northwest Norway . Assuming that larval hatching depends more directly on temperature than does budburst (Topp & Kirsten 1991;Van Asch & Visser 2007), there is a large potential for local and regional differences in the degree of match between larval hatching and birch budburst in individual years. Thus for the observed massive large-scale outbreak to develop, meteorological conditions providing a good phenological match must have occurred simultaneously at a large scale.…”