Divergent trophic levels in two cryptic sibling bat species

Abstract

Changes in dietary preferences in animal species play a pivotal role in niche specialization. Here, we investigate how divergence of foraging behaviour affects the trophic position of animals and thereby their role for ecosystem processes. As a model, we used two closely related bat species, Myotis myotis and M. blythii oxygnathus, that are morphologically very similar and share the same roosts, but show clear behavioural divergence in habitat selection and foraging. Based on previous dietary studies on synanthropic populations in Central Europe, we hypothesised that M. myotis would mainly prey on predatory arthropods (i.e., secondary consumers) while M. blythii oxygnathus would eat herbivorous insects (i.e., primary consumers). We thus expected that the sibling bats would be at different trophic levels. We first conducted a validation experiment with captive bats in the laboratory and measured isotopic discrimination, i.e., the stepwise enrichment of heavy in relation to light isotopes between consumer and diet, in insectivorous bats for the first time. We then tested our trophic level hypothesis in the field at an ancient site of natural coexistence for the two species (Bulgaria, south-eastern Europe) using stable isotope analyses. As predicted, secondary consumer arthropods (carabid beetles; Coleoptera) were more enriched in (15)N than primary consumer arthropods (tettigoniids; Orthoptera), and accordingly wing tissue of M. myotis was more enriched in (15)N than tissue of M. blythii oxygnathus. According to a Bayesian mixing model, M. blythii oxygnathus indeed fed almost exclusively on primary consumers (98%), while M. myotis ate a mix of secondary (50%), but also, and to a considerable extent, primary consumers (50%). Our study highlights that morphologically almost identical, sympatric sibling species may forage at divergent trophic levels, and, thus may have different effects on ecosystem processes.

Carbon Isotope Ratios Document That the Elytra of Western Corn Rootworm (Coleoptera: Chrysomelidae) Reflects Adult Versus Larval Feeding and Later Instar Larvae Prefer Bt Corn to Alternate Hosts

“…Analyses of stable carbon isotopes have been widely used to describe and characterize a broad range of trophic interactions in various ecosystems (e.g., Tallamy and Pesek 1996, Traugott et al 2008, Grant and Kopple 2009, Hawke and Clark 2010, Okuzaki et al 2010, Schallhart et al 2011, Siemers et al 2011. Even though the literature suggests that the carbon isotopic ratio of the beetleÕs elytra gives relevant indirect information on the larval diet quality (e.g., Tallamy andPesek 1996, Gould et al 2002), our data do not support this hypothesis when western corn rootworm adults have the opportunity to feed after emergence.…”

Social learning within and across species: information transfer in mouse-eared bats

“…Although the preferred diet of M. oxygnathus differs significantly from M. myotis, there is also considerable overlap in diet and habitat use by the two species (e.g., Arlettaz 1996;Arlettaz et al 1997;Siemers et al 2011). Ecology, morphology, and foraging behaviour of these two species are therefore relatively similar (Arlettaz 1999).…”

Gastrointestinal digeneans (Platyhelminthes: Trematoda) of horseshoe and vesper bats (Chiroptera: Rhinolophidae and Vespertilionidae) in Serbia

“…The absence of L. linstowi in these Myotis species is likely explained by their diet. Metacercaria of digeneans from the family Lecithodendriidae often develop in the body of larvae and nymphs of aquatic insects of the order Plecoptera, Ephemeroptera, Odonata or Trichoptera (Hall, 1960), whereas the main prey items of M. oxygnathus and M. myotis are coleopterans (Carabidae, Scarabaeidae, Silphidae), orthopterans (Tettigoniidae, Gryllotalpidae), dermapterans and hymenopterans (Arlettaz, 1996;Pereira et al, 2002;Siemers et al, 2011;Graclik & Wasielewski, 2012). Studies on the composition of the helminth fauna of wild animals can reveal the presence of parasites that are potential pathogens of domestic animals or man.…”