Evolution of slow and fast development in predatory ladybirds

Abstract

The frequency distribution of the durations of development of 516 larvae of Adalia bipunctata is unimodal, and the fast-and slow-developing larvae can be identified at the beginning of the fourth (=last) instar. To determine the advantages of fast and slow development, the survival, duration of development, growth and number of aphids consumed by fast-and slow-developing fourth instar larvae fed different numbers aphids were recorded. The percentages of fast-and slow-developing fourth instar larvae that survived when fed 0.5, 1 or an excess of aphids per day, surprisingly, did not differ. The slow-developing larvae of both sexes took longer to complete their development than the fast-developing larvae when fed 1 or an excess of aphids per day, and although the weights of the fast-and slow-developing fourth instar larvae differed at the beginning of the instar, they did not differ at the end of this instar when fed 1 aphid per day. However, when reared on an excess of aphids per day, the adult weights of the fast-developing individuals was greater than that of slowdeveloping individuals. The average durations for which the larvae in the two groups survived when fed 0.5 aphids/day differed with the larvae of the fast-developing individuals surviving for 9.8 AE 0.5 days and slowdeveloping individuals 17 AE 1.3 days. Assuming that it is the rate of predator biomass increase, which is maximized by evolution, a model of the relationship between the rate of development/growth of a predator and that of its prey indicates that the optimum growth rate of a predator is positively associated with that of its prey. The evolutionary implications of these results are discussed.

Slow and fast development in two aphidophagous ladybirds on scarce and abundant prey supply

“…This may also act as a counterbalancing force that preserves the slow developing individuals in the population. Dixon et al (2015) reported that the optimum growth rate of a predator is positively associated with that of its prey and that plays a crucial role in evolution. The variation in responses with change in prey is similar to that witnessed in these two ladybirds at varying temperatures under ad libitum prey supply (Singh et al, 2014(Singh et al, , 2016.…”

“…Such an inherent variation in developmental rate has also been reported in salmonid fish (Gross, 1985), butterflies, Maculinea rebeli (Hirchke) (Schönrogge et al , 2000; Witek et al , 2006) and Bicyclus anynana (Butler) (Lewis et al , 2010), predaceous syrphid, Microdon mutabilis (L.) (Schönrogge et al , 2000), nematode, Teladorsagia circumcincta (Stadelman) (Skorping, 2007) and other insects (Gouws et al ., 2011) including ladybirds (Mishra & Omkar, 2012; Singh et al , 2014, 2016; Dixon et al , 2015). Though, not commonly assessed, but in ladybirds this inherent variation in developmental rates within the same cohort and population has been observed (Rodriguez-Saona & Miller, 1995; Dixon, 2000; Mishra & Omkar, 2012; Singh et al , 2014, 2016; Dixon et al , 2015), albeit their distribution pattern has not been assessed until recently (Mishra & Omkar, 2012; Singh et al , 2014, 2016; Dixon et al , 2015). The lack of unanimity about bimodality of developmental durations of ladybirds could simply be a result of very few studies on their growth and development attempting to assess the distribution of development rates.…”

“…In cohorts of M. sexmaculatus and P. dissecta , fast developing individuals were large in size and females were more fecund with higher egg viability than slow developing individuals in both prey supply. Dixon et al (2015) reported that the adult weights of the fast-developing individuals were greater than that of slow-developing individuals when reared on an excess of aphids per day. The variation in fecundity was supported by the differences in body mass (Darwin, 1874).…”

Influence of intraspecific competition for food on the bodyweight of the adult aphidophagous ladybird, Coccinella transversalis

“…Siddiqui et al (2015) report that mutual interference of slow and fast developing ladybird, Propylea dissecta (Mulsant) were −0.394 and −0.808, respectively, indicating that fast developers search more efficiently and spend less time interacting with conspecifics. Fast developers tend to eat faster than slow developers and are heavier and lay more eggs than the latter (Singh et al 2014;Dixon et al 2016). Mutual interference values for unparasitized and parasitized larvae of Nephus includens (Kirsch) were −0.44 and −0.92 respectively, indicating that interference reduces the foraging capacity of parasitized more than that of unparasitized larvae (Bayoumy and Michaud 2012).…”

Generation time ratio, rather than voracity, determines population dynamics of insect – natural enemy systems, contrary to classical Lotka-Volterra models

“…Thus, for predators, the optimal strategy involves counteracting pressures to maximize their own reproduction and survival while conserving enough prey to sustain a sufficient food supply for their offspring. This is very nicely exemplified by long-lived insect predators, such as ladybirds, feeding on short-lived prey, such as aphids (Dixon and Kindlmann 1998;Kindlmann and Dixon 1999a, 1999b, 2001Dostálková et al 2002;Dixon et al 2015). As most of these predators suffer enormous egg and larval mortality due to cannibalism (Dixon and Kindlmann 2012) and intraguild predation (Mills 1982), selection acts mainly on optimizing their oviposition strategies in terms of maximizing the likelihood that their offspring will survive until reproductive age.…”