Seasonal Declines in Offspring Fitness and Selection for Early Reproduction in Nymph-Overwintering Grasshoppers

Abstract

In this study, I examine the effects of natural and experimentally induced variation in life cycle timing on offspring fitness in Arphia sulphurea and Chortophaga viridifasciata, to understand the selective pressures shaping phenology in these two species of nymph-overwintering grasshoppers. Because these species lack embryonic diapause, hatching varies over a two month range under natural conditions. I used a cold treatment to delay hatching of some egg pods and extend the natural range of hatching dates. Due to the shorter time for growth and poorer growing conditions late in the fall, late-hatching nymphs of both species grew to a smaller size before winter and suffered higher overwinter mortality, compared to early nymphs. In addition, late nymphs that did survive the winter became reproductive later in the following year's breeding season. Size- dependent mortality of offspring during the winter is a strong selective pressure favoring early reproduction in these species. Female adult life history traits appear responsive to the seasonal declines in offspring fitness, in that late-maturing females began reproducing sooner after adult maturation and reproduced at a more rapid rate, even at the expense of having shorter adult longevity and producing fewer total egg pods. Experimental manipulations were crucial in understanding the fitness consequences of intrapopulation variation in the timing of specific life-cycle events for these species.

Effects of night-time warming on temperate ectotherm reproduction: potential fitness benefits of climate change for side-blotched lizards

“…Developing embryos do not appear to have the capacity to compensate physiologically for cold temperatures during incubation (Booth, 1998) (but see Du et al, 2011) or to hatch prematurely in response to decreasing temperatures, such as those experienced in autumn (Shine, 2002). Advancing reproductive phenology is one of the most likely means of maximizing fitness in seasonal environments, and is a common pattern in many lizards (Sinervo and Doughty, 1996;Warner and Shine, 2007) as well as other species, such as fishes (Schultz, 1993), insects (Landa, 1992) and birds (Verhulst, 1998). To this end, by delaying hatching in our experimental cohorts beyond that of natural variation we were able to show that overwinter survival is related to hatching phenology.…”

Male Genotype Affects Female Longevity in Drosophila Melanogaster

“…This undoubtedly reflects the widespread observation that timing of reproduction is a strong determinant of offspring viability and reproductive success both in animals (Lack 1950;Berger 1992;Landa 1992;Brinkhof et al 1993;Sih and Moore 1993;Trites and Antonelis 1994;Olsson and Shine 1997;Bowyer et al 1998;Post and Klein 1999) and plants (Janzen 1976;Harper 1977;Dieringer 1991;Young and Augspurger 1991;Domínguez and Dirzo 1995). However, the conditions under which the evolutionarily stable strategy (ESS) of the timing of reproduction involves synchrony or asynchrony within populations is a matter of debate.…”

Selection Against Late Emergence and Small Offspring in Atlantic Salmon (Salmo Salar)

“…Breeding time may affect offspring fitness through several selective agents. For instance, early-born individuals will often have an ontogenetic advantage over those born later that can be important in size-dependent competition (e.g., Johnsson et al 1999;Cutts et al 1999; see also Maynard Smith and Parker 1976), mortality (e.g., Landa 1992;Garvey et al 1998;Hurst and Conover 1998;Schultz et al 1998), and reproduction (Landa 1992;Schultz 1993). Moreover, in territorial species, early birth can be competitively advantageous as a result of prior residence effects (Nilsson 1990;Sandell and Smith 1991;Cutts et al 1999).…”