Abstract
Natural aquatic sites are disappearing worldwide, especially in the Mediterranean region where amphibians are frequently forced to move for reproduction to artificial sites designed for irrigation and cattle watering (i.e., wells, tanks and drinking troughs). In artificial aquatic sites, where resources (space and food) are usually limited, trophic niche information can be particularly useful to infer the suitability of habitats for amphibian conservation especially when more than one species co-occurs. In this paper, we focused on three newt species: The Italian newt (Lissotriton italicus), the Italian smooth newt (Lissotriton vulgaris meridionalis) and the Italian crested newt (Triturus carnifex) inhabiting man-made wells widespread in an area in Central Italy characterized by few available natural aquatic sites. Specifically, we analyzed the trophic spectrum of the species, their interactions and overlap, and discussed the potential role of wells in amphibian conservation. Overall, 550 newt individuals occurring in 16 distinct wells were sampled. The study species consumed similar resources, mainly of aquatic origin, with Diptera larvae and Cladocera representing the most important preys. The high degree of diet overlap observed may be due to site oligotrophy and high availability of small-sized prey, and it does not necessarily lead to competition. Newts had similar narrow niche width values and a generalist feeding pattern with high diversity among individuals. Lissotriton italicus and T. carnifex showed wider niche width in isolation than in syntopy condition, probably as a result of interspecific competition and/or intraguild predation. We showed that artificial aquatic sites are important for newt ecology and conservation since they allow up to three species to cohabit, thus representing a good surrogate of natural habitats. The study wells apparently provided suitable trophic conditions for newts in terms of prey availability and catchability. To date, just a few studies have contributed to a greater understanding of newts’ diet in artificial aquatic sites and this gap of knowledge has to be filled to clarify their role in amphibian ecology and conservation.
Highlights
IntroductionWidespread amphibian declines have become a critical issue in Conservation Biology during the past two decades, especially in the Mediterranean region where reproductive sites are increasingly disappearing because of habitat loss, alteration and fragmentation caused by agricultural intensification and urban development [1]
Several studies have contributed to a greater understanding of newts’ diet in artificial sites, but they were mostly focused on natural-like waterbodies, whereas trophic interactions in non-natural shape waterbodies remained less investigated [19]
The diet of the study species was mainly composed of Cladocera and Diptera larvae, the former dominating the food composition of L. vulgaris (LV) (IRI = 6930.532, FO = 71%) and the latter representing the most important prey in Lissotriton italicus (LI) (IRI = 2175.647, FO = 59%) and T. carnifex (TC) (IRI = 1867.151, FO = 60%)
Summary
Widespread amphibian declines have become a critical issue in Conservation Biology during the past two decades, especially in the Mediterranean region where reproductive sites are increasingly disappearing because of habitat loss, alteration and fragmentation caused by agricultural intensification and urban development [1]. In the Mediterranean region, newts have adapted to breed in temporary ponds and streams [4], especially in Italy where assemblages of up to three sympatric species may occur [5,6,7,8]. In temporary ponds and streams, newt community structure may be shaped by complex interactions including intraguild predation, environmental stochasticity and competition for habitat use and food resources [9]. Sympatric newts feed mostly on arthropods and differ in their interspecific feeding strategy and degree of specialization [10]
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