The food web in a subterranean ecosystem is driven by intraguild predation

Abstract

Trophic interactions of cave arthropods have been understudied. We used molecular methods (NGS) to decipher the food web in the subterranean ecosystem of the Ardovská Cave (Western Carpathians, Slovakia). We collected five arthropod predators of the species Parasitus loricatus (gamasid mites), Eukoenenia spelaea (palpigrades), Quedius mesomelinus (beetles), and Porrhomma profundum and Centromerus cavernarum (both spiders) and prey belonging to several orders. Various arthropod orders were exploited as prey, and trophic interactions differed among the predators. Linear models were used to compare absolute and relative prey body sizes among the predators. Quedius exploited relatively small prey, while Eukoenenia and Parasitus fed on relatively large prey. Exploitation of eggs or cadavers is discussed. In contrast to previous studies, Eukoenenia was found to be carnivorous. A high proportion of intraguild predation was found in all predators. Intraspecific consumption (most likely cannibalism) was detected only in mites and beetles. Using Pianka’s index, the highest trophic niche overlaps were found between Porrhomma and Parasitus and between Centromerus and Eukoenenia, while the lowest niche overlap was found between Parasitus and Quedius. Contrary to what we expected, the high availability of Diptera and Isopoda as a potential prey in the studied system was not corroborated. Our work demonstrates that intraguild diet plays an important role in predators occupying subterranean ecosystems.

A Primer on Spider Assemblages in Levantine Caves: The Neglected Subterranean Habitats of the Levant—A Biodiversity Mine

“…It is very common to find troglophile arachnids in the entrance of Levantine caves, as in caves of other regions of the world. Arachnids (and among them spiders) are often numerically dominant in caves and are considered dominant predators in many cave foodwebs [31][32][33][34]. Of the 11 extant terrestrial arachnid orders, five orders (i.e., Araneae, Opiliones, Palpigradi, Pseudoscorpiones, and Scorpiones) and the polyphyletic sub-class Acari were reported to have troglobite species around the world [35][36][37][38], while troglobite species of three orders (i.e., Amblypygi [39], Ricinulei, and Schizomida) were reported only from subtropical and tropical regions [35].…”

Observations on the habitat and feeding behaviour of the hypogean genus Eukoenenia (Palpigradi, Eukoeneniidae) in the Western Italian Alps

“…A direct attack on collembola in caves was documented (Lukić 2012) and a specimen of E. strinatii that carried a dead springtail, keeping it with chelicerae, was photographed in this work. Moreover, a recent study on gut content of E. spelaea has shown the presence of spiders, beetles, mites, springtails, and flies DNA (Parimuchová et al 2021), supporting carnivory in palpigrades. Wheeler (1900) suggested that palpigrades probably feed on eggs or juvenile stages of bigger arthropods invertebrates, however, our observations on scavenging activity could explain the presence of genetic material of large arthropods in the intestinal tube of palpigrades.…”

“…An observation of Eukoenenia hunting springtail provides evidence of a predatory habit (Lukić 2012), however, the presence of Cyanobacteria in their gut indicates an alternative food source (Smrž et al 2013) and scavenging is also another possibility. A recent study based on molecular analysis (NGS) on the gut-content of Eukoenenia spelaea (Peyerimhoff, 1902) in Ardovská Cave, Slovakia, supports carnivory behaviour (Parimuchová et al 2021).…”

“…The first scientific investigation of the species in this order began in 1885 in Sicily (Italy), where the zoologist Giovanni Battista Grassi (Grassi and Calandruccio 1885) discovered a "mysterious species" of arachnid that he described as Koenenia mirabilis Grassi & Calandruccio, 1885, now Eukoenenia mirabilis (Grassi & Calandruccio, 1885). Silvestri (1905) described for the first time the anatomy of the species and he was followed by other authors but many aspects of the biology of the order, including food selection and reproduction, are still unknown (Condé 1996;Smrž et al 2013;Christian et al 2014;Parimuchová et al 2021). Molecular phylogeny of the taxon was performed only by Giribet et al (2014) that demonstrated the monophily of the order and of the family of Eukoeneniidae.…”

Arthropoda fauna of Zindan Cave (Isparta, Turkey) with notes on new records and some ecological characteristics

“…Predators such as Chilopoda, Araneae, Pseudoscorpiones, carnivorous Acarina and some Coleoptera are hunting invertebrates which feed on dead organic material and microbes. Subterranean food webs mostly consist of more generalist species, as in soil food webs (Parimuchová et al, 2021).…”