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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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Interacting effects of egg number, egg mass and egg care on nymph number. The number of nymphs produced at hatching resulted from interactions between (A) egg number and mean egg mass, (B) egg number and mother weight loss and (C) mother weight loss and mean egg mass. As an illustration, the regressions lines are given for when (A) the mean egg mass was 0.55 mg (black), 0.65 mg (red) and 0.75 mg (green), as well as when (B & C) the relative female weight loss was 15% (black), 0% (red) or −15% (green).
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Figure 2: Interacting effects of egg number, egg mass and egg care on nymph number. The number of nymphs produced at hatching resulted from interactions between (A) egg number and mean egg mass, (B) egg number and mother weight loss and (C) mother weight loss and mean egg mass. As an illustration, the regressions lines are given for when (A) the mean egg mass was 0.55 mg (black), 0.65 mg (red) and 0.75 mg (green), as well as when (B & C) the relative female weight loss was 15% (black), 0% (red) or −15% (green).

Mentions: A series of pairwise interactions among egg number, mean egg mass and female weight loss determined the number of hatched nymphs (Table 2A), a result supporting the entangled effects of maternal expenditure on egg care and egg production on nymph production. In particular, decreases in mean egg mass or in relative weight loss by mothers during egg care cancelled the otherwise positive association between egg and nymph numbers (Table 2A, Figures 2A and 2B). Conversely, decreases in the weight loss by mothers entailed a negative association between mean egg mass and nymph number (Table 2A, Figure 2C). Independently from the interactive effects on nymph number presented above, the mean weight of nymphs at hatching was positively associated with the mean egg mass (Table 2B, Figure 3), but independent of egg number, mother weight loss or any interaction among the three tested factors (Table 2B). Overall, nymph number was independent of the mean weight of nymphs at hatching (Spearman rank correlation test; rs = −0.15, S = 81049, P = 0.190).


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)

Interacting effects of egg number, egg mass and egg care on nymph number. The number of nymphs produced at hatching resulted from interactions between (A) egg number and mean egg mass, (B) egg number and mother weight loss and (C) mother weight loss and mean egg mass. As an illustration, the regressions lines are given for when (A) the mean egg mass was 0.55 mg (black), 0.65 mg (red) and 0.75 mg (green), as well as when (B & C) the relative female weight loss was 15% (black), 0% (red) or −15% (green).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Interacting effects of egg number, egg mass and egg care on nymph number. The number of nymphs produced at hatching resulted from interactions between (A) egg number and mean egg mass, (B) egg number and mother weight loss and (C) mother weight loss and mean egg mass. As an illustration, the regressions lines are given for when (A) the mean egg mass was 0.55 mg (black), 0.65 mg (red) and 0.75 mg (green), as well as when (B & C) the relative female weight loss was 15% (black), 0% (red) or −15% (green).
Mentions: A series of pairwise interactions among egg number, mean egg mass and female weight loss determined the number of hatched nymphs (Table 2A), a result supporting the entangled effects of maternal expenditure on egg care and egg production on nymph production. In particular, decreases in mean egg mass or in relative weight loss by mothers during egg care cancelled the otherwise positive association between egg and nymph numbers (Table 2A, Figures 2A and 2B). Conversely, decreases in the weight loss by mothers entailed a negative association between mean egg mass and nymph number (Table 2A, Figure 2C). Independently from the interactive effects on nymph number presented above, the mean weight of nymphs at hatching was positively associated with the mean egg mass (Table 2B, Figure 3), but independent of egg number, mother weight loss or any interaction among the three tested factors (Table 2B). Overall, nymph number was independent of the mean weight of nymphs at hatching (Spearman rank correlation test; rs = −0.15, S = 81049, P = 0.190).

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
Related in: MedlinePlus