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Mother and offspring fitness in an insect with maternal care: phenotypic trade-offs between egg number, egg mass and egg care.

Koch LK, Meunier J - BMC Evol. Biol. (2014)

Bottom Line: We found negative associations between egg number and mass as well as between egg number and maternal expenditure on egg care.In contrast, offspring weight was positively associated with egg mass only.Finally, maternal expenditure on egg care reduced their future reproduction, but this effect was only detected when mothers were experimentally isolated from their offspring at egg hatching.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Evolutionary Biology, Institute of Zoology, Johannes Gutenberg University of Mainz, Mainz, Germany. meunier.joel@gmail.com.

ABSTRACT

Background: Oviparous females have three main options to increase their reproductive success: investing into egg number, egg mass and/or egg care. Although allocating resources to either of these three components is known to shape offspring number and size, potential trade-offs among them may have key impacts on maternal and offspring fitness. Here, we tested the occurrence of phenotypic trade-offs between egg number, egg mass and maternal expenditure on egg care in the European earwig, Forficula auricularia, an insect with pre- and post-hatching forms of maternal care. In particular, we used a series of laboratory observations and experiments to investigate whether these three components non-additively influenced offspring weight and number at hatching, and whether they were associated with potential costs to females in terms of future reproduction.

Results: We found negative associations between egg number and mass as well as between egg number and maternal expenditure on egg care. However, these trade-offs could only be detected after statistically correcting for female weight at egg laying. Hatchling number was not determined by single or additive effects among the three life-history traits, but instead by pairwise interactions among them. In particular, offspring number was positively associated with the number of eggs only in clutches receiving high maternal care or consisting of heavy eggs, and negatively associated with mean egg mass in clutches receiving low care. In contrast, offspring weight was positively associated with egg mass only. Finally, maternal expenditure on egg care reduced their future reproduction, but this effect was only detected when mothers were experimentally isolated from their offspring at egg hatching.

Conclusions: Overall, our study reveals simultaneous trade-offs between the number, mass and care of eggs. It also demonstrates that these factors interact in their impact on offspring production, and that maternal expenditure on egg care possibly shapes female future reproduction. These findings emphasize that studying reproductive success requires consideration of phenotypic trade-offs between egg-number, egg mass and egg care in oviparous species.

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Influence of maternal expenditure on egg care on their 2nd clutch. Maternal expenditure on egg care was estimated through their relative weight loss between egg laying and egg hatching. After hatching of their 1st clutch eggs, females experienced (grey) or did not experience (black) post-hatching family life.
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Figure 4: Influence of maternal expenditure on egg care on their 2nd clutch. Maternal expenditure on egg care was estimated through their relative weight loss between egg laying and egg hatching. After hatching of their 1st clutch eggs, females experienced (grey) or did not experience (black) post-hatching family life.

Mentions: The relative weight loss of mothers during egg care affected their investment into future reproduction, but this effect depended on the occurrence of post-hatching family life (GLM; Interaction between relative mother weight loss and occurrence of post-hatching family life: Likelihood ratio (LR) χ2 = 11.33, d.f. = 1, P = 0.0008). In particular, mother weight loss was negatively correlated with the number of 2nd clutch eggs when mothers were isolated from their 1st clutch nymphs at egg hatching (Figure 4; GLM estimate ± SE = −138.8 ± 73.4, t = −3.58, P = 0.001) but not when they were kept with their nymphs after hatching (GLM estimate ± SE = − 93.6 ± 80.8, t = 1.34, P = 0.188). In contrast, the mean egg mass of the 2nd clutch was independent of the three components of reproductive success measured on the 1st clutch and the occurrence of family life (GLM; Relative mother weight loss during 1st clutch: LR χ21 = 0.30, d.f. = 1, P = 0.583; Mean egg mass measured in the 1st clutch: LR χ21 = 0.36, d.f. = 1, P = 0.546; Post-hatching family life: LR χ21 < 0.01, d.f. = 1, P = 0.924; Interactions, all P > 0.384).


Mother and offspring fitness in an insect with maternal care: phenotypic trade-offs between egg number, egg mass and egg care.

Koch LK, Meunier J - BMC Evol. Biol. (2014)

Influence of maternal expenditure on egg care on their 2nd clutch. Maternal expenditure on egg care was estimated through their relative weight loss between egg laying and egg hatching. After hatching of their 1st clutch eggs, females experienced (grey) or did not experience (black) post-hatching family life.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4061511&req=5

Figure 4: Influence of maternal expenditure on egg care on their 2nd clutch. Maternal expenditure on egg care was estimated through their relative weight loss between egg laying and egg hatching. After hatching of their 1st clutch eggs, females experienced (grey) or did not experience (black) post-hatching family life.
Mentions: The relative weight loss of mothers during egg care affected their investment into future reproduction, but this effect depended on the occurrence of post-hatching family life (GLM; Interaction between relative mother weight loss and occurrence of post-hatching family life: Likelihood ratio (LR) χ2 = 11.33, d.f. = 1, P = 0.0008). In particular, mother weight loss was negatively correlated with the number of 2nd clutch eggs when mothers were isolated from their 1st clutch nymphs at egg hatching (Figure 4; GLM estimate ± SE = −138.8 ± 73.4, t = −3.58, P = 0.001) but not when they were kept with their nymphs after hatching (GLM estimate ± SE = − 93.6 ± 80.8, t = 1.34, P = 0.188). In contrast, the mean egg mass of the 2nd clutch was independent of the three components of reproductive success measured on the 1st clutch and the occurrence of family life (GLM; Relative mother weight loss during 1st clutch: LR χ21 = 0.30, d.f. = 1, P = 0.583; Mean egg mass measured in the 1st clutch: LR χ21 = 0.36, d.f. = 1, P = 0.546; Post-hatching family life: LR χ21 < 0.01, d.f. = 1, P = 0.924; Interactions, all P > 0.384).

Bottom Line: We found negative associations between egg number and mass as well as between egg number and maternal expenditure on egg care.In contrast, offspring weight was positively associated with egg mass only.Finally, maternal expenditure on egg care reduced their future reproduction, but this effect was only detected when mothers were experimentally isolated from their offspring at egg hatching.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Evolutionary Biology, Institute of Zoology, Johannes Gutenberg University of Mainz, Mainz, Germany. meunier.joel@gmail.com.

ABSTRACT

Background: Oviparous females have three main options to increase their reproductive success: investing into egg number, egg mass and/or egg care. Although allocating resources to either of these three components is known to shape offspring number and size, potential trade-offs among them may have key impacts on maternal and offspring fitness. Here, we tested the occurrence of phenotypic trade-offs between egg number, egg mass and maternal expenditure on egg care in the European earwig, Forficula auricularia, an insect with pre- and post-hatching forms of maternal care. In particular, we used a series of laboratory observations and experiments to investigate whether these three components non-additively influenced offspring weight and number at hatching, and whether they were associated with potential costs to females in terms of future reproduction.

Results: We found negative associations between egg number and mass as well as between egg number and maternal expenditure on egg care. However, these trade-offs could only be detected after statistically correcting for female weight at egg laying. Hatchling number was not determined by single or additive effects among the three life-history traits, but instead by pairwise interactions among them. In particular, offspring number was positively associated with the number of eggs only in clutches receiving high maternal care or consisting of heavy eggs, and negatively associated with mean egg mass in clutches receiving low care. In contrast, offspring weight was positively associated with egg mass only. Finally, maternal expenditure on egg care reduced their future reproduction, but this effect was only detected when mothers were experimentally isolated from their offspring at egg hatching.

Conclusions: Overall, our study reveals simultaneous trade-offs between the number, mass and care of eggs. It also demonstrates that these factors interact in their impact on offspring production, and that maternal expenditure on egg care possibly shapes female future reproduction. These findings emphasize that studying reproductive success requires consideration of phenotypic trade-offs between egg-number, egg mass and egg care in oviparous species.

Show MeSH