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Breaking up the wall: metal-enrichment in Ovipositors, but not in mandibles, co-varies with substrate hardness in gall-wasps and their associates.

Polidori C, García AJ, Nieves-Aldrey JL - PLoS ONE (2013)

Bottom Line: Among gall-inducers, metals in the ovipositors were more likely to be found in species inducing galls in woody plants.On the other hand, no relationships were found between substrate hardness or gall-association type and concentration of metals in mandibles.We suggest that ecological pressures related to oviposition were sufficiently strong to drive changes in ovipositor elemental structure in these gall-associated Hymenoptera.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biodiversidad y Biología Evolutiva, Museo Nacional de Ciencias Naturales-Consejo Superior de Investigaciones Científicas, Madrid, Spain. cpolidori@mncn.csic.es

ABSTRACT
The cuticle of certain insect body parts can be hardened by the addition of metals, and because niche separation may require morphological adaptations, inclusion of such metals may be linked to life history traits. Here, we analysed the distribution and enrichment of metals in the mandibles and ovipositors of a large family of gall-inducing wasps (Cynipidae, or Gall-Wasps) (plus one gall-inducing Chalcidoidea), and their associated wasps (gall-parasitoids and gall-inquilines) (Cynipidae, Chalcidoidea and Ichneumonoidea). Both plant types/organs where galls are induced, as well as galls themselves, vary considerably in hardness, thus making this group of wasps an ideal model to test if substrate hardness can predict metal enrichment. Non-galler, parasitic Cynipoidea attacking unconcealed hosts were used as ecological "outgroup". With varying occurrence and concentration, Zn, Mn and Cu were detected in mandibles and ovipositors of the studied species. Zn tends be exclusively concentrated at the distal parts of the organs, while Mn and Cu showed a linear increase from the proximal to the distal parts of the organs. In general, we found that most of species having metal-enriched ovipositors (independently of metal type and concentration) were gall-invaders. Among gall-inducers, metals in the ovipositors were more likely to be found in species inducing galls in woody plants. Overall, a clear positive effect of substrate hardness on metal concentration was detected for all the three metals. Phylogenetic relationships among species, as suggested by the most recent estimates, seemed to have a weak role in explaining metal variation. On the other hand, no relationships were found between substrate hardness or gall-association type and concentration of metals in mandibles. We suggest that ecological pressures related to oviposition were sufficiently strong to drive changes in ovipositor elemental structure in these gall-associated Hymenoptera.

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Occurrence of metals in the mandibles of the studied species, mapped on a phylogenetic tree derived from recent literature and unpublished data (see Methods).Species for which mandibles were not studied have their name in grey. * Zn and Cu are present in the sexual form, while only Zn is present in the asexual form.
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pone-0070529-g001: Occurrence of metals in the mandibles of the studied species, mapped on a phylogenetic tree derived from recent literature and unpublished data (see Methods).Species for which mandibles were not studied have their name in grey. * Zn and Cu are present in the sexual form, while only Zn is present in the asexual form.

Mentions: We found Zn, Mn and Cu in mandibles (Table 1). Zn was present in all species (Fig. 1) with generally high concentrations, with only 12 species out of 55 showing Zn falling in the lowest rank (<5 wt%) and more than half of the species (31) showing Zn >10.1 wt% (ranks 3–4) (Table 1). The abundant Zn is even visible from SEM images of mandibles, in which a clearly whiter area is recognizable at the outer margins of the teeth (Fig. 2). Such pattern is confirmed by the elemental analysis, which invariably showed values at the inner point and a sigmoid increase from the inner to the outer part of the teeth (increasing the rank) (Fig. S2A and Table S2). Mn was found in about half of the species (28) (Fig. 1), with concentration mainly (18 spp.) falling in lowest rank 1 (<0.3 wt%) (Table 1). Mn was found to increase in concentration from the inner to the outer part of the mandible teeth in about half of the cases; when this occurs, it increased following a linear trend (Fig. S2B and Table S2). Cu occurred in 26 species (Fig. 1) with concentration in most cases (21 spp.) below 0.6 wt% (ranks 1–2) (Table 1), and increased (linearly) in concentration towards the tip of the teeth in all these species (Fig. S2C and Table S2). For both Mn and Cu, the concentration at the inner point was or extremely low and not higher than the error (see methods), while their concentration measured both at the distal point and from the line-scan fall in the same rank.


Breaking up the wall: metal-enrichment in Ovipositors, but not in mandibles, co-varies with substrate hardness in gall-wasps and their associates.

Polidori C, García AJ, Nieves-Aldrey JL - PLoS ONE (2013)

Occurrence of metals in the mandibles of the studied species, mapped on a phylogenetic tree derived from recent literature and unpublished data (see Methods).Species for which mandibles were not studied have their name in grey. * Zn and Cu are present in the sexual form, while only Zn is present in the asexual form.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3722128&req=5

pone-0070529-g001: Occurrence of metals in the mandibles of the studied species, mapped on a phylogenetic tree derived from recent literature and unpublished data (see Methods).Species for which mandibles were not studied have their name in grey. * Zn and Cu are present in the sexual form, while only Zn is present in the asexual form.
Mentions: We found Zn, Mn and Cu in mandibles (Table 1). Zn was present in all species (Fig. 1) with generally high concentrations, with only 12 species out of 55 showing Zn falling in the lowest rank (<5 wt%) and more than half of the species (31) showing Zn >10.1 wt% (ranks 3–4) (Table 1). The abundant Zn is even visible from SEM images of mandibles, in which a clearly whiter area is recognizable at the outer margins of the teeth (Fig. 2). Such pattern is confirmed by the elemental analysis, which invariably showed values at the inner point and a sigmoid increase from the inner to the outer part of the teeth (increasing the rank) (Fig. S2A and Table S2). Mn was found in about half of the species (28) (Fig. 1), with concentration mainly (18 spp.) falling in lowest rank 1 (<0.3 wt%) (Table 1). Mn was found to increase in concentration from the inner to the outer part of the mandible teeth in about half of the cases; when this occurs, it increased following a linear trend (Fig. S2B and Table S2). Cu occurred in 26 species (Fig. 1) with concentration in most cases (21 spp.) below 0.6 wt% (ranks 1–2) (Table 1), and increased (linearly) in concentration towards the tip of the teeth in all these species (Fig. S2C and Table S2). For both Mn and Cu, the concentration at the inner point was or extremely low and not higher than the error (see methods), while their concentration measured both at the distal point and from the line-scan fall in the same rank.

Bottom Line: Among gall-inducers, metals in the ovipositors were more likely to be found in species inducing galls in woody plants.On the other hand, no relationships were found between substrate hardness or gall-association type and concentration of metals in mandibles.We suggest that ecological pressures related to oviposition were sufficiently strong to drive changes in ovipositor elemental structure in these gall-associated Hymenoptera.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biodiversidad y Biología Evolutiva, Museo Nacional de Ciencias Naturales-Consejo Superior de Investigaciones Científicas, Madrid, Spain. cpolidori@mncn.csic.es

ABSTRACT
The cuticle of certain insect body parts can be hardened by the addition of metals, and because niche separation may require morphological adaptations, inclusion of such metals may be linked to life history traits. Here, we analysed the distribution and enrichment of metals in the mandibles and ovipositors of a large family of gall-inducing wasps (Cynipidae, or Gall-Wasps) (plus one gall-inducing Chalcidoidea), and their associated wasps (gall-parasitoids and gall-inquilines) (Cynipidae, Chalcidoidea and Ichneumonoidea). Both plant types/organs where galls are induced, as well as galls themselves, vary considerably in hardness, thus making this group of wasps an ideal model to test if substrate hardness can predict metal enrichment. Non-galler, parasitic Cynipoidea attacking unconcealed hosts were used as ecological "outgroup". With varying occurrence and concentration, Zn, Mn and Cu were detected in mandibles and ovipositors of the studied species. Zn tends be exclusively concentrated at the distal parts of the organs, while Mn and Cu showed a linear increase from the proximal to the distal parts of the organs. In general, we found that most of species having metal-enriched ovipositors (independently of metal type and concentration) were gall-invaders. Among gall-inducers, metals in the ovipositors were more likely to be found in species inducing galls in woody plants. Overall, a clear positive effect of substrate hardness on metal concentration was detected for all the three metals. Phylogenetic relationships among species, as suggested by the most recent estimates, seemed to have a weak role in explaining metal variation. On the other hand, no relationships were found between substrate hardness or gall-association type and concentration of metals in mandibles. We suggest that ecological pressures related to oviposition were sufficiently strong to drive changes in ovipositor elemental structure in these gall-associated Hymenoptera.

Show MeSH
Related in: MedlinePlus