Research Article |
Corresponding author: Stanislav Korenko ( korenko@af.czu.cz ) Academic editor: Gavin Broad
© 2022 Stanislav Korenko, Jakub Sýkora, Ľudmila Černecká, Peter Gajdoš, Pavol Purgat, Ján Černecký, Kamil Holý, Petr Heneberg, Ingi Agnarsson.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Korenko S, Sýkora J, Černecká Ľ, Gajdoš P, Purgat P, Černecký J, Holý K, Heneberg P, Agnarsson I (2022) Elevation gradient affects the distribution and host utilisation of Zatypota anomala (Hymenoptera, Ichneumonidae) associated with mesh web weaving spiders (Araneae, Dictynidae). Journal of Hymenoptera Research 93: 89-100. https://doi.org/10.3897/jhr.93.91513
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The spatial distribution of parasitoids is closely linked to the distribution and ecological requirements of their hosts. Several studies have documented changes in the fauna composition of parasitoids in response to elevation, but data on parasitoids associated with spiders are missing. The koinobiont ichneumonid wasp Zatypota anomala is strictly specialised on spiders of the genus Dictyna (Dictynidae) in Europe. We examined the distribution of spiders of the family Dictynidae in forest ecotones in central Europe across a broad elevation gradient (110–1466 m a.s.l.). We checked the spiders for parasitism by Z. anomala. It was most abundant at the mid-elevations (median 712 m a.s.l., range 179–870 m a.s.l.). We identified four dictynid spider species as Z. anomala hosts. These were Dictyna arundinacea, Dictyna uncinata, Nigma flavescens, and Nigma walckenaeri. All four species and the genus Nigma were recorded as hosts for the first time. The parasitoids strongly preferred juvenile instars of their hosts. The body length differed between parasitised Dictyna and Nigma spiders (medians: 1.95 mm and 2.55 mm, respectively). The distribution of Dictyna and Nigma spiders overlapped along the elevation gradient, but parasitism incidence significantly differed between spider genera along the elevation gradient. Nigma was parasitized at lower elevations between 179–254 m a.s.l. and Dictyna at higher elevations between 361–870 m a.s.l. The phenology of Z. anomala is closely tied to the univoltine life strategy of its host spiders. The parasitoid female oviposits in autumn, and its offspring overwinter as larvae on the host, reach adulthood during spring, and pass the summer as an adult.
altitude, Darwin wasp, Ephialtini, host-parasitoid interaction, host range, host shift, host specificity, Polysphincta group of genera
The effect of elevational gradient on species assemblages remains a central theme of biogeography and ecology (
As some parasitoids may be specialised on hosts living at higher elevations, species-specific data are needed, particularly for associations where specific hosts are present at various elevations. Parasitism rates can differ with elevation and latitude (
Spiders of the family Dictynidae are aerial web builders producing 3D tangle webs on tree canopies, shrubs, or higher vegetation (
In the present study, we aimed to explore elevation gradient effects on the parasitism of Dictynidae by the ichneumonid wasp parasitoid Z. anomala. We hypothesised that the composition of the dictynid spider community differs with elevation and that this may reflect elevation preferences in its parasitoid.
Communities of spiders from the family Dictynidae (potential hosts of Z. anomala) were studied in 227 localities in 39 orographic units in Czechia and Slovakia at elevations ranging from 110 to 1466 m a.s.l. in the years 2016–2021 (Fig.
The two-tailed Kruskal-Wallis test and Dunn’s multiple comparison test as Multiple Choice Test (MCT) were used to reveal differences in the distribution of dictynid species/genera along the elevation gradient. The two-tailed Mann-Whitney U test was used to reveal differences in the body size of parasitised dictynid spiders and differences in parasitoid distribution along the elevation gradient between those reared from Dictyna and Nigma. The calculations were performed in GraphPad InStat v. 3.06. Data are shown as medians and 1Q and 3Q of the Interquartile Range (IQR) unless stated otherwise.
We used the Arc GIS 10.3 environment for the spatial presentation of the association of the distribution of Dictyna and Nigma and their parasitoid Z. anomala with elevation. Part of the spatial analysis was dedicated to the distribution of host species and their parasitised specimens within the orographic units. Orographic units represent functional ecological units, each defined by elevation and by ecological, climatic, and geological conditions.
The examination of tree and shrub branches led to the collection of 2,332 individuals of dictynid spiders. They represented eight species that belonged to five genera, namely Argenna, Brigittea, Dictyna, Lathys, and Nigma (Table
Total number of collected dictynid spiders (potential hosts), their distribution along the elevation gradient, and parasitism by Zatypota anomala. Median and (1Q–3Q) of IQR are shown; data are presented in mm. N – number of collected spiders; p – number of parasitized spiders.
Spider species | N | Distribution | p |
---|---|---|---|
Argenna subnigra (O. P.-C.) | 5 | 138(138–263) | 0 |
Brigittea latens (Fabricius) | 3 | 124(121–288) | 0 |
Dictyna arundinacea (Linnaeus) | 240 | 747(712–760) | 5 |
Dictyna pusilla Thorell | 61 | 870(870–870) | 0 |
Dictyna uncinata Thorell | 319 | 318(273–570) | 14 |
Dictyna sp. | 808 | 708 (439–760) | 44 |
Lathys humilis (Blackwall) | 742 | 572 (205–672) | 0 |
Nigma flavescens (Walckenaer) | 111 | 439(305–760) | 1 |
Nigma walckenaeri (Roewer) | 38 | 231(183–405) | 8 |
Nigma sp. | 5 | 431(431–441) | 0 |
Total | 2332 | 663(273–755) | 72 |
Differences in elevation distribution between dictynid species and genera. Dunn’s Multiply Comparisons Test. “z” means Mean Rand Differences. The rare species A. subnigra and B. latens were not included in the analysis. Spider individuals identified only to genus level were not included in the species analysis. The rare genera Argenna and Brigittea were not included in the genera analysis.
Comparison | z | p-value |
---|---|---|
Species | ||
D. arundinacea vs. D. pusilla | -287.87 | < 0.001 |
D. arundinacea vs. D. uncinata | 388.28 | < 0.001 |
D. arundinacea vs. L. humilis | 381.49 | < 0.001 |
D. arundinacea vs. N. flavescens | 250.46 | < 0.001 |
D. arundinacea vs. N. walckenaeri | 662.22 | < 0.001 |
D. pusilla vs. D. uncinata | 676.15 | < 0.001 |
D. pusilla vs. L. humilis | 669.36 | < 0.001 |
D. pusilla vs. N. flavescens | 538.34 | < 0.001 |
D. pusilla vs. N. walckenaeri | 950.09 | < 0.001 |
D. uncinata vs. L. humilis | -6.788 | ns |
D. uncinata vs. N. flavescens | -137.82 | ns |
D. uncinata vs. N. walckenaeri | 273.94 | < 0.01 |
L. humilis vs. N. flavescens | -131.03 | < 0.05 |
L. humilis vs. N. walckenaeri | 280.72 | < 0.01 |
N. flavescens vs. N. walckenaeri | 411.75 | < 0.001 |
Genera | ||
Dictyna vs. Lathys | 192.87 | < 0.001 |
Dictyna vs. Nigma | 164.37 | < 0.01 |
Lathys vs. Nigma | -28,50 | ns |
Of the eight collected dictynid species, four species of spiders from the genera Dictyna and Nigma were documented as hosts (Table
Body size of potential hosts and body size of parasitised spiders. Median and (1Q–3Q) of IQR are shown in mm. Different letters beside juvenile body sizes denote significant differences in body size analysed by Dunn’s multiple comparison test.
Dictyna | Nigma | Lathys | |
---|---|---|---|
Female | 2.55 (2.3–2.6) | 3.0 (2.6–3.2) | 2.45 (2.4–2.5) |
Male | 2.41 (2.3–2.5) | 2.6 (2.51–2.73) | No data |
Juvenile | 1.92 (1.78–2.14)b | 2.5 (2.3–2.7)a | 2.0 (1.8–2.0)b |
Parasitised | 1.95 (1.84–2.09) | 2.55 (2.45–2.6) | No record |
The parasitoid Z. anomala was present in 16 (33 localities) out of the 39 orographic units (227 localities) where accepted hosts (the genera Nigma and/or Dictyna) occurred in the examined spider community (Fig.
However, elevation differed significantly between localities where Nigma spp. were parasitised (183 (183–183) m a.s.l) and where Dictyna spp. were parasitized (712 (675–772) m a.s.l.) (Mann-Whitney test, U = 0, U´ = 567, p < .001, Fig.
Dictynid spiders were parasitised by Z. anomala in high numbers in early spring and autumn. The parasitoid overwintered as larvae of the second instar and reached adulthood the following spring. Summer is expected to be the period of adult flight. Adult Z. anomala attacks the next generation of juvenile hosts in autumn, when the spiders have grown to a body size suitable for oviposition (Fig.
Zatypota anomala presumably possess phenotypic plasticity, which enables it to attack spiders from different genera at different elevations. Although these accepted taxa differ in some morphological and behavioural traits, their ecological position in the local community is very similar across continents (e.g., Europe vs. North America) and along the elevation gradient. We found that Z. anomala attacked at least four species from the genera Dictyna and Nigma. Former host records of Z. anomala from Europe were mostly identified only to genus level as Dictyna spp.; only Dictyna pusilla Thorell was identified as a specific host species by
We found that Z. anomala accepted both Dictyna and Nigma spiders in Europe, but we never found both genera parasitised in the same locality. Zatypota anomala constantly attacked spider species which were highly abundant locally. Our results suggest that locally dominant dictynid species were easily available and consequently became preferred hosts. Local preference for the dominant host might also be imprinted onto the local population by hatching from the dominant host over several generations. In other parasitoids, it is known that offspring prefer to develop in/on the host in/on which their mother developed (
Polysphinctine wasps strictly associated with spiders possess high host specificity, even monophagy (e.g.,
We found that Z. anomala preferred mid-elevations, around 700 m a.s.l., but we also found it in smaller numbers at lower elevations and not at all at higher elevations over 800 m a.s.l. Zatypota anomala is strictly associated with spiders from the family Dictynidae, which were rarely collected at elevations over 800 m a.s.l. The absence and low abundance of dictynid spiders in localities at higher elevations seem to indicate the upper limit of the parasitoid distribution on the elevation gradient. On the basis of the collected data, we assume the occurrence of host substitution in Z. anomala, where spiders of the genus Dictyna were parasitised in localities at middle elevations, and spiders of the genus Nigma were attacked in localities at lower elevations.
Parasitoid phenology is synchronised with host phenology. This synchronisation influences many traits of the parasitoid life history, including the number of generations per year (e.g.,
The most important limitation on the acceptance of spider hosts by polysphinctines is the suitability of their size – specifically, the body size ratio between parasitoid and host (e.g.,
The study was financially supported by project No. LTAUSA19084 of the Ministry of Education Youth and Sports of the Czech Republic. ĽČ was supported by the Slovak Scientific Grant Agency VEGA, project No. 2/0149/20. JS was also supported by CULS, Internal FAPPZ, project No. 21150/1312/3152.