| 1. |
- Pujol-Buxo, Eudald, et al.
(author)
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Growth strategies of tadpoles along the pond permanency gradient
- 2016
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In: Evolutionary Ecology. - : Springer Science and Business Media LLC. - 0269-7653 .- 1573-8477. ; 30:6, s. 1117-1132
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Journal article (peer-reviewed)abstract
- The preference for particular features of water bodies for reproduction is one of the most important aspects of anuran ecology, affecting key aspects of both tadpole and adult life. The use by species of different habitats along the pond permanency gradient has been already studied, noting conflicting selective pressures from predation and desiccation risk. Here, we aim to discover physiological patterns related with this gradient. As a study system, we used the full anuran community of the NE Iberian Peninsula. We quantified growth rate, consumption rate, food assimilation and the proportion of energy allocated to growth, as well as gut length, for all species. Food consumption rate and growth allocation were the variables that defined tadpole growth, while food assimilation abilities and gut length seem to have a secondary or cryptic role in growth. More interestingly however, our data suggests a labile continuum of consumption-based versus allocation/assimilation-based growth strategies differentiating species. Differences among species follow predictions of adaptation to the pond permanency gradient selective pressures. Species from ephemeral ponds are more prone to use consumption-related growth tactics while species inhabiting ponds with longer hydroperiods are more efficient retaining and allocating energy into growth, although results seem partly shaped by strong interspecific competition. Physiological differences in growth and the usage of the assimilated energy could be an additional factor to understand how tadpoles adapt to the features of ponds they inhabit, as well as how they compete and coexist.
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| 2. |
- San Sebastian, Olatz, et al.
(author)
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Differential trophic traits between invasive and native anuran tadpoles
- 2015
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In: Aquatic Invasions. - : Regional Euro-Asian Biological Invasions Centre Oy (REABIC). - 1798-6540 .- 1818-5487. ; 10:4, s. 475-484
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Journal article (peer-reviewed)abstract
- How trophic resources are managed is a key factor in our understanding of the success of invasive species. In amphibians that usually occupy ephemeral ponds, the capacity to acquire resources and food selection are especially important because as a pond dries, the larval density increases and food resources are limited. Abundant and high-quality food can increase the final size and reduce the duration of development of amphibians. The aim of this work was to assess the trophic traits of tadpoles of the invasive (originally North African) anuran Discoglossus pictus compared to those of native European Epidalea calamita tadpoles under laboratory conditions. Food of two different levels of quality was supplied, and the feeding activity and food preference of the two species were analysed alone and in co-occurrence. D. pictus was capable of modifying its behaviour and food preferences; while E. calamita displayed much milder differences between treatments. Both alone and in co-occurrence with the native species, the invasive tadpoles obtained higher feeding activity values and showed a stronger preference for high-quality food. Additionally, when high densities of the two species shared food resources, the feeding activity results indicated potential displacement of the native tadpoles to low-quality resources. D. pictus thus presents trophic traits that are favourable for invasion and could limit the fitness of E. calamita when resources are limited or there is a risk of pond desiccation.
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| 3. |
- San Sebastian, Olatz, et al.
(author)
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Trophic Strategies of a Non-Native and a Native Amphibian Species in Shared Ponds
- 2015
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:6
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Journal article (peer-reviewed)abstract
- One of the critical factors for understanding the establishment, success and potential impact on native species of an introduced species is a thorough knowledge of how these species manage trophic resources. Two main trophic strategies for resource acquisition have been described: competition and opportunism. In the present study our objective was to identify the main trophic strategies of the non-native amphibian Discoglossus pictus and its potential trophic impact on the native amphibian Bufo calamita. We determine whether D. pictus exploits similar trophic resources to those exploited by the native B. calamita (competition hypothesis) or alternative resources (opportunistic hypothesis). To this end, we analyzed the stable isotope values of nitrogen and carbon in larvae of both species, in natural ponds and in controlled laboratory conditions. The similarity of the delta N-15 and delta C-13 values in the two species coupled with isotopic signal variation according to pond conditions and niche partitioning when they co-occurred indicated dietary competition. Additionally, the non-native species was located at higher levels of trophic niches than the native species and B. calamita suffered an increase in its standard ellipse area when it shared ponds with D. pictus. These results suggest niche displacement of B. calamita to non-preferred resources and greater competitive capacity of D. pictus in field conditions. Moreover, D. pictus showed a broader niche than the native species in all conditions, indicating increased capacity to exploit the diversity of resources; this may indirectly favor its invasiveness. Despite the limitations of this study (derived from potential variability in pond isotopic signals), the results support previous experimental studies. All the studies indicate that D. pictus competes with B. calamita for trophic resources with potential negative effects on the fitness of the latter.
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