Maternal effects on phenotypic plasticity in larvae of the salamander Hynobius retardatus

Abstract

Maternal effects are widespread and influence a variety of traits, for example, life history strategies, mate choice and capacity to avoid predation. Therefore, maternal effects may also influence phenotypic plasticity of offspring, but few studies have addressed the relationship between maternal effects and phenotypic plasticity of offspring. We examined the relationship between a maternally influenced trait (egg size) and the phenotypic plasticity of the induction rate of the broad-headed morph in the salamander Hynobius retardatus. The relationship between egg size and the induction of the broad-headed morph was tested across experimental crowding conditions (densities of low conspecifics, high conspecifics, and high heterospecific anuran), using eggs and larvae from eight natural populations with different larval densities of conspecifics and heterospecifics. The broad-headed morph has a large mouth that enables it to consume either conspecifics or heterospecifics, and this ability gives survival advantages over the normal morph. We have determined that there is phenotypic plasticity in development, as shown by an increase in the frequency of broad-headed morph in response to an increase in the density of conspecifics and heterospecifics. This reaction norm differed between populations. We also determined that the frequency of the broad-headed morph is affected by egg size in which larger egg size resulted in expression of the broad-headed morph. Furthermore, we determined that selection acting on the propensity to develop the broad-headed morph has produced a change in egg size. Lastly, we found that an increase in egg size alters the reaction norm to favor development of the broad-headed morph. For example, an equal change in experimental density produces a greater change in the frequency of the broad-headed morph in larvae developing from large eggs than it does in larvae developing from small eggs. Population differences in plasticity might be the results of differences in egg 3 size between populations, which is caused by the adaptive integration of the plasticity and egg size. Phenotypic plasticity can not evolve independently of maternal effects.

Evolution of maternal egg size effects in sister salamander species

“…Offspring from larger cockroach, echinoid, salamander and frog eggs have higher phenotypic plasticity (Doughty 2002, Holbrook andSchal 2004;McAlister 2007;Michimae et al, 2009;Martin and Pfennig, 2010). This study suggests that with evolutionary egg size increases, more traits are added to the suite of traits responding to egg size variation and the response of each trait to yolk quantity variation increases.…”

“…Smith and Fretwell 1974) (Grime 1979) and a previous study of the responses of A. barbouri and A. texanum to oxygen (Landberg 2010) suggest that low-resource environments select for phenotypes that are stress tolerant and have low magnitudes of plasticity whereas high-resource environments select for phenotypes that have the ability to take advantage of resources and have high plasticity. Empirical support for an increase in phenotypic plasticity with egg size comes from both within and between species (McAlister 2007; Michimae et al, 2009). If high maternal investment in yolk has acted as a high-resource selective environment, phenotypic plasticity is expected to increase in A. barbouri.…”

Maternal body condition influences magnitude of anti-predator response in offspring

“…Clutches were then returned to the aviary and reared in 10 l of aged tap water. Subsamples were weighed, counted (range: 13 -40 eggs sample 21 ), photographed underwater against a scale bar, then freeze-dried at 2518C with a vacuum of 0.120 mbar for 24 h (eggs dried in 2013 only). Mean dry egg mass was then calculated from the three subsamples.…”

“…Larger larval size can also confer an advantage in coping with both abiotic [19,20] and biotic [9,16] stressors. Maternal influence on egg size can also alter the probability of offspring developing a competitive morphology under crowded conditions [21]. Thus, maternal provisioning influences the expression of plasticity through variation in offspring body size.…”

Inducible offences affect predator–prey interactions and life‐history plasticity in both predators and prey

“…In general, our work suggests that for organisms with complex life cycles, the impacts of offensive phenotypes on predator and prey populations will be mediated not just by changes in survival, but by changes in their life-history traits which will also depend on environmental conditions in both the larval and adult environments (Altwegg & Reyer 2003). We suggest that spatial and temporal variation in the population densities of R. pirica and H. retardatus may be driven by variation in factors affecting the expression of offensive phenotypes of H. retardatus larvae (Michimae & Wakahara 2002;Michimae 2006;Kishida, Trussell & Nishimura 2009;Michimae et al 2009). For example, H. retardatus salamander larvae exhibit offensive phenotypes more frequently when in the presence of small tadpoles than with large tadpoles (Michimae & Wakahara 2002), and less frequently when in the presence of predatory dragonfly larvae (Kishida, Trussell & Nishimura 2009;Kishida et al 2011).…”