A Unique Nest-Protection Strategy in a New Species of Spider Wasp

<div><p>Hymenoptera show a great variation in reproductive potential and nesting behavior, from thousands of eggs in sawflies to just a dozen in nest-provisioning wasps. Reduction in reproductive potential in evolutionary derived Hymenoptera is often facilitated by advanced behavioral mechanisms and nesting strategies. Here we describe a surprising nesting behavior that was previously unknown in the entire animal kingdom: the use of a vestibular cell filled with dead ants in a new spider wasp (Hymenoptera: Pompilidae) species collected with trap nests in South-East China. We scientifically describe the ‘Bone-house Wasp’ as <i>Deuteragenia ossarium</i> sp. nov., named after graveyard bone-houses or ossuaries. We show that <i>D. ossarium</i> nests are less vulnerable to natural enemies than nests of other sympatric trap-nesting wasps, suggesting an effective nest protection strategy, most likely by utilizing chemical cues emanating from the dead ants.</p></div

List of all sympatric cavity-nesting wasp species collected together with <i>Deuteragenia ossarium</i>.

<p>Pompilidae were identified by Raymond Wahis (Liege, Belgium), Sphecidae by Michael Ohl (Berlin, Germany) and Vespidae by Tingjing Li (Chongqing, P.R. China).</p

Summary statistics of the binomial glmm testing for the effect of group identity (other wasps/<i>D. ossarium</i>) and brood cell numbers on parasitism rates.

<p>Summary statistics of the binomial glmm testing for the effect of group identity (other wasps/<i>D. ossarium</i>) and brood cell numbers on parasitism rates.</p

Parasitism rates of <i>D. ossarium</i> were significantly lower compared to other cavity-nesting was species.

<p>The sympatric cavity-nesting wasp community is exemplified by <i>Orancistrocerus drewseni</i> (de Saussure, 1857) (Vespidae, lower left). As examples of parasitoid species <i>Chrysis principalis</i> Smith, 1874 (Chrysididae, top) and <i>Leucospis sp.</i> (Leucospidae, middle) are shown. Photographs: Michael Staab.</p

<i>Deuteragenia ossarium</i> Ohl sp. nov., (A, B) female, holotype; (C–F) male, paratype (T1482).

<p>(A, C) dorsal habitus, (B, D) right forewing, (E) head in frontal view, (F) genitalia in ventral view, slightly spread to show major elements. Scale bars: (A, C) 5.0 mm, (B, D) 2.0 mm, (E, F) 0.6 mm. Photographs: Bernhard Schurian (A–E), Birger Neuhaus (F).</p

Raw data for ant-wound interactions

This data set contains all raw data necessary to reproduce the results of the paper. Details on the data are provided in the associated ReadMe file

Tree Species Richness Promotes Invertebrate Herbivory on Congeneric Native and Exotic Tree Saplings in a Young Diversity Experiment

<div><p>Tree diversity in forests is an important driver of ecological processes including herbivory. Empirical evidence suggests both negative and positive effects of tree diversity on herbivory, which can be, respectively, attributed to associational resistance or associational susceptibility. Tree diversity experiments allow testing for associational effects, but evidence regarding which pattern predominates is mixed. Furthermore, it is unknown if herbivory on tree species of native vs. exotic origin is influenced by changing tree diversity in a similar way, or if exotic tree species escape natural enemies, resulting in lower damage that is unrelated to tree diversity. To address these questions, we established a young tree diversity experiment in temperate southwestern Germany that uses high planting density (49 trees per plot; plot size 13 m²). The species pool consists of six congeneric species pairs of European and North American origin (12 species in total) planted in monocultures and mixtures (1, 2, 4, 6 species). We assessed leaf damage by leaf-chewing insects on more than 5,000 saplings of six broadleaved tree species. Plot-level tree species richness increased leaf damage, which more than doubled from monocultures to six-species mixtures, strongly supporting associational susceptibility. However, leaf damage among congeneric native and exotic species pairs was similar. There were marked differences in patterns of leaf damage across tree genera, and only the genera likely having a predominately generalist herbivore community showed associational susceptibility, irrespective of the geographical origin of a tree species. In conclusion, an increase in tree species richness in young temperate forests may result in associational susceptibility to feeding by generalist herbivores.</p></div

Results of the best-performing linear mixed-effect for leaf damage by chewers.

<p>Results of the best-performing linear mixed-effect for leaf damage by chewers.</p

Mean leaf damage by chewing insects per tree species richness level for the six studied tree species.

<p>Mean leaf damage by chewing insects per tree species richness level for the six studied tree species.</p

Leaf damage by chewing insects.

<p>(A) Relationship between leaf damage and tree species richness. The solid line illustrates the prediction of a linear model (significant at <i>P</i> < 0.05). (B) Comparison of leaf damage on native European (EU) and exotic North American (NA) trees. The data are log(x+1)-transformed mean damage values per tree individual and presented as violin plots that combine a boxplot with a kernel density plot; medians and means are, respectively, indicated by white dots and horizontal black lines.</p