Predatory behaviour of alpine (<i>Ichthyosaura alpestris</i>) and smooth (<i>Lissotriton vulgaris</i>) newts towards conspecific and heterospecific eggs and larvae

<p>Consumption of conspecific and heterospecific eggs and larvae is common in many animal taxa, including many amphibians. Adult newts (Amphibia Urodela) often co-occur temporally and spatially with conspecific and heterospecific newt eggs and larvae, and adult individuals may benefit from their consumption, but little is known on the degree of discrimination in the newts’ predatory behaviour towards them. We performed two laboratory experiments to examine whether adult male and female alpine, <i>Ichthyosaura alpestris</i> (Laurenti 1768), and smooth, <i>Lissotriton vulgaris</i> (Linnaeus 1758), newts discriminate between conspecific and heterospecific eggs and larvae in their predatory behaviour. In our study, eight out of 64 newts succeeded in consuming eggs, although 3 times as many attacked them. We found no differences in predatory behaviour towards conspecific and heterospecific eggs, or between males and females in either species. Similarly, we found no evidence for the occurrence of discriminative predatory behaviour towards conspecific and heterospecific larvae. In our experiments the criterion for whether a newt would consume a prey item (egg or larva) was not the prey’s identity (species), but the newts’ ability to detect, capture and/or ingest it. Our results suggest that newts of both species follow an opportunistic foraging strategy, consuming whatever prey of appropriate size they manage to capture.</p

Appendix_PLOS ONE (herzien)- Voucher numbers - RMNH

This file contains all information relating to the Drilus specimens (adults, larvae, and exuviae) obtained from snail shells in the course of this study. Voucher numbers refer to the official collections in which the specimens were deposited

Greek <i>Albinaria</i> snails and their <i>Drilus</i> predators.

<p>A, <i>Albinaria hippolyti</i> from Crete (photo: V. Wiese). B and C, the clausilium, shown in the shell aperture after removal of the left lateral shell wall (B shows a less-obstructing, N-type clausilium, C shows a more obstructing, G-type clausilium). D and E, a male and a female, respectively, of a yet undescribed <i>Drilus</i> species from Crete (scale: 2 mm). F, a full-grown larva of <i>Drilus</i> “L” from the Peloponnese (same scale as D and E). G, an estivating <i>A. discolor</i> from the Peloponnese, with a <i>Drilus</i> exit bore hole. H, a <i>Drilus</i> “L” exiting from its prey, an <i>A. menelaus</i> from the Peloponnese.</p

Data Collection Codes

Collection details pertaining to the Albinaria samples, some containing Drilus laevae or adult, that were used in this stud

Greek <i>Albinaria</i> snails and their <i>Drilus</i> predators.

<p>A, <i>Albinaria hippolyti</i> from Crete (photo: V. Wiese). B and C, the clausilium, shown in the shell aperture after removal of the left lateral shell wall (B shows a less-obstructing, N-type clausilium, C shows a more obstructing, G-type clausilium). D and E, a male and a female, respectively, of a yet undescribed <i>Drilus</i> species from Crete (scale: 2 mm). F, a full-grown larva of <i>Drilus</i> “L” from the Peloponnese (same scale as D and E). G, an estivating <i>A. discolor</i> from the Peloponnese, with a <i>Drilus</i> exit bore hole. H, a <i>Drilus</i> “L” exiting from its prey, an <i>A. menelaus</i> from the Peloponnese.</p

Still from Video S1, showing a <i>Drilus</i> “L” larva (in the lab) creating an exit bore-hole from within a prey <i>Albinaria meleaus</i>, followed by the lengthy procedure by which the larva emerges from the shell.

<p>Still from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0100366#pone.0100366.s008" target="_blank">Video S1</a>, showing a <i>Drilus</i> “L” larva (in the lab) creating an exit bore-hole from within a prey <i>Albinaria meleaus</i>, followed by the lengthy procedure by which the larva emerges from the shell.</p

A, five <i>Drilus</i> species from the Peloponnese have different specificities for <i>Albinaria</i> as prey, and concomitant propensities to bore holes in the shell (calculated as the number of bore holes divided by the total number of prey).

<p>B, difference (<i>P</i><0.05, Fisher's exact test) in prey specificity between <i>Drilus</i> “D” (more <i>Albinaria</i>-specific) and “E” (less <i>Albinaria</i> specific) in two localities where both species occur syntopically (these data are not included in fig. 3A). C, differences in <i>Drilus</i> predation rate (dark portion of the bar) between solitarily (“sol”) and group-wise (“agg”) estivating snails of <i>A. caerulea</i> in four 5 m² plots in the islands of Paros, Naxos, and Thira (voucher numbers RMNH.MOL.84354-84363, RMNH.MOL.85192, and RMNH.MOL.85193). An aggregate was defined as a cluster of >20 snails, with distances of <2 cm separating them. A snail was considered solitary if it was >20 cm distance from a conspecific (significance tested with Chi-square test). D, positions of entrance holes in shells of species with an N-type clausilium compared with those in shells of species with a G-type clausilium, shown for the entire eastern Peloponnese as well as for the site Monemvasia, where both clausilium types occur microsympatrically. (<i>P</i>-values are derived from Fisher's exact test.)</p

Map of Crete and surrounding islands, showing contours of regionally varying <i>Drilus</i> predation rates (given as percentages attacked shells per sample) in <i>Albinaria</i>, derived from bore-hole frequencies in 1,160 museum samples from Naturalis Biodiversity Center, Leiden, The Netherlands, Haus der Natur, Cismar, Germany, and Natural History Museum, Budapest, Hungary.

<p>Maps were drawn using inverse kriging distance calculation in R v.2.15.2 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0100366#pone.0100366-R1" target="_blank">[23]</a>, with packages gstat <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0100366#pone.0100366-Pebesma1" target="_blank">[24]</a>, maptools (R v.0.8-27), rgdal (R v.0.8-12) and rgeos (R v.0.3-2).</p