Robert Schabetsberger

Delineation of terrestrial reserves for amphibians: post-breeding migrations of Italian crested newts (Triturus c. carnifex) at high altitude

Little is known about the terrestrial phase of high-altitude populations of European amphibians, in spite of potentially important implications for conservation and management. We followed 51 adult Italian crested newts (Triturus carnifex) that emigrated from an ephemeral lake (Lake Ameisensee, 1282 m a.s.l., Northern Calcareous Alps, Austria) with radio-tracking. Transmitters were inserted into each newt’s stomach and we collected data until it did not relocate for more than 1 week or until the transmitter was regurgitated. Most newts migrated in a north-westerly direction towards an old growth spruce forest. Subterranean shelters, mostly 5–80 cm deep burrows of small mammals located 13–293 m from the lake, were reached in between 4 h and 7.8 days. Twenty percent of T. carnifex shared their refuges with other congeneric species. Females migrated significantly further (median distance 168 m) than males (median 53 m). We propose a terrestrial core reserve extending 100 m from the furthermost terrestrial refuges of newts found with radio-tracking linked with patches of old-growth forest. This terrestrial reserve is substantially larger than has been suggested as sufficient in the recent literature.

Losing the Bounty?: Investigating Species Richness in Isolated Freshwater Ecosystems of Oceania

Abstract: The South Pacific freshwater ecosystems have never been investigated systematically. Although their ecological value has long been recognized and recommended for protection, little action has been taken so far. Here, we present results of 39 lentic water bodies on 18 islands belonging to seven countries. Temperature, conductivity, and pH were measured and samples of aquatic organisms were collected. Freshwater algae, nematodes, rotifers, ostracods, copepods, cladocerans, and aquatic oribatid mites were identified to genus or species level. Sixty-six percent of all taxa recorded have a cosmopolitan distribution, 14% are circumtropical/tropicopolitan species, and for 20% a restricted distribution predominantly in Australasia has previously been reported. Eleven new copepod and three new ostracod taxa were discovered. Out of 39 water bodies we found at least 17 stocked with nonindigenous fish species. Salinization and uncontrolled introduction of alien fish species may lead to reduced species richness in these remote freshwater ecosystems. The highest species richness was recorded in old, shallow, fish-free softwater lakes at high altitude.

Trophic specialisations in alternative heterochronic morphs

Polymorphisms are suspected of reducing competition among conspecifics in heterogeneous environments by allowing differential resource use. However the adaptive significance of alternative morphs has been poorly documented. The aim of this study is to determine food partitioning of two heterochronic morphs of the Alpine newt, Triturus alpestris, in mountain lakes. The morphs differ in the functional morphology of their feeding apparatus. Only paedomorphs are able to expel water during prey suction behind the mouth through gill slits. We observed a substantial trophic differentiation between morphs in all lakes. Paedomorphs preyed mainly on plankton, whereas metamorphs foraged on terrestrial invertebrates that fell upon the water surface. This resource partitioning may facilitate the coexistence of the alternative morphs in lakes devoid of vertebrate competitors. Food diversity may thus favour the evolutionary maintenance of facultative polymorphism in natural populations.

Resource partitioning in two heterochronic populations of Greek Alpine newts, Triturus alpestris veluchiensis

Current ecological models suggest that the maintenance of trophic polymorphisms is favoured by a different resource use in alternative morphs. Facultative paedomorphosis in newts is an example of phenotypic variation as paedomorphs retain morphological larval traits, such as gills and gill slits. The aim of this study was to find out whether heterochronic morphs occupy particular micro-habitats and focus on specific prey items. Resource partitioning was found between morphs. It concerns mainly food selection with paedomorphs preying more on plankton and less on terrestrial invertebrates than metamorphs. Some habitat specializations were also found with metamorphs being more abundant at the water surface than paedomorphs. Diel variation in habitat use of the two different morphs was minimal. Polymorphism allows Alpine newts to exploit the different resources in the lakes in order to minimize intraspecific competition, but the extent of resource partitioning depends on habitat characteristics.

Distribution and ecology of copepods in mountainous regions of the Eastern Alps

Copepod species richness, patterns of distribution and composition of assemblages were evaluated in high-altitude sites in the Eastern Alps. Diverse habitats were sampled in 160 lentic water bodies from different geologic areas, ranging from acid bog ponds to alkaline karst waters and from small temporary puddles to deep lakes. The altitudinal range comprised all mountainous regions from the montane (1290 m a.s.l.) to the alpine (2886 m a.s.l.) zone. Forty-four species were recorded, with the harpacticoids being the richest group. Although most species occupied a wide altitudinal range, some stenotopic mountain forms were restricted to alpine habitats. The most widespread taxa were Acanthocyclops vernalis, Eucyclops serrulatus, Bryocamptus rhaeticus, Arctodiaptomus alpinus and Cyclops abyssorum tatricus. All species found were listed along with notes on their distribution, ecology and patterns of coexistence. There was both a marked change in species composition and a decline in species richness from hardwater habitats in the Limestone Alps to softwater sites in the Central Alps. Copepod taxocoenoses were most diverse in montane limestone lakes and impoverished with increasing altitude. Copepods and sampling sites were ordinated using canonical correspondence analysis (CCA), and copepod assemblages were defined in relation to physical and chemical parameters, habitat type and presence/absence of planktivorous fish. Planktonic species were largely absent from lakes with introduced fish. Although calanoid associations were common, coexisting diaptomids were rare, suggesting a strong interspecific competition between these predominantly filter feeders. Most copepods found are common eurytopic or cold stenothermal, but some exhibit peculiar disjunct patterns of geographical distribution, and others are apparently restricted to the Alps. Some species are discussed in more detail from a zoogeographical point of view. A complete checklist of copepods recorded to date from high-altitude sites in the Eastern Alps is provided.

Hang on or run? Copepod mating versus predation risk in contrasting environments

Mating durations of copepods were found to differ significantly between fishless high-altitude waters and lowland lakes containing fish. In lowland species the whole mating process was completed within a few minutes, but it averaged over an hour in high-altitude species. Alpine copepods showed a prolonged post-copulatory association between mates, during which the male clasped the female for an extended period after spermatophore transfer, while in lowland species males abandoned their partner immediately after copulation. Prolonged associations also occurred after transfer of spermatophores to heterospecific females with shorter conspecific mating duration, suggesting that male interests largely dictate the time spent in tandem. The differences observed may be adaptations to environments with different predation pressure, as pairs in tandem are more conspicuous and less reactive than single animals. We argue that differences in mating behavior and mating duration evolved under sexual versus natural selection, reflecting trade-offs between enhancement of fertilization success and reduction of vulnerability to visual predation. In fishless mountain lakes with high intrasexual competition, guarding males can reduce the risk of spermatophore displacement or the risk that the female will accept sperm from rival males without increased risk of being eaten, thereby maximizing paternity. Populations from fishless alpine lakes further differed from lowland species by exhibiting higher female/male size dimorphism and more intense pigmentation. While these traits vary between populations according to predation pressure, mating duration appears to be more species-specific.

Limnological Aspects of Two Tropical Crater Lakes (Lago Biao and Lago Loreto) on the Island of Bioko (Equatorial Guinea)

The limnology of Lago Biao and Lago Loreto, two tropical crater lakes on the island of Bioko, was investigated for the first time in January of 2002. Lago Biao fills a caldera at 1750 m altitude and is 18.5 m deep. This lake was characterized by low conductivity (11.6-13.3 μS cm−1), low pH (5.9-6.2), an oxycline between 6 and 10 m depth (90-27% saturation), and a Secchi depth of 5.5 m. Dinoflagellates, desmids, and green algae dominated the phytoplankton community. The rotifers Anuraeopsis fissa, Polyarthra indica, Trichocerca simoneae, and T. similis were most abundant above or in the thermocline. During the day Tropocyclops prasinus tjeefi and Chaoborus cf. ceratopogones concentrated in the oxycline, whereas Daphnia laevis was most abundant between 0 and 4 m depth. In contrast, L. Loreto is 82 m deep and probably fills an explosion crater (‘maar’) at 1050 m altitude. The lake had a turbid, yellowish appearance and a Secchi depth of only 0.6 m. Oxygen content dropped from 121% at the surface to 6% in 10 m depth. The pH declined from 9.15 at the surface to 7.4 in only 2.5 m depth and became acidic at approximately 15 m depth. One species of cyanobacterium, one dinoflagellate and one green alga dominated the phytoplankton and together reached densities of 12 100 cells ml−1. Only one rotifer (Brachionus angularis) and one copepod (Tropocyclops prasinus tjeefi) species colonized the open water. Intact algal cells and zooplankton specimens were encountered near the bottom.

The Presence of Common Frogs (Rana temporaria) Increases the Body Condition of Syntopic Alpine Newts (Ichthyosaura alpestris) in Oligotrophic High-Altitude Ponds: Benefits of High-Energy Prey in a Low-Productivity Habitat

In low-productivity, high-altitude habitats food can become a limiting factor for the occurring amphibians. Common frog eggs deposited in ponds and the developing tadpoles represent energy-rich prey for syntopic Alpine newts that should be advantageous for storing sufficient amounts of energy to survive hibernation and breed the following spring. In our study population in the Zillertal Alps, Austria at 2100 m a.s.l., in two consecutive years we found the body mass of Alpine newts to be significantly higher in ponds containing tadpoles of the common frog than in ponds without tadpoles. As the frogs forage mostly on land, we regard their eggs as an allochtonous nutrient subsidy for ultra-oligotrophic high-altitude ponds that may have a profound effect on the fitness and distribution of Alpine newts and common frogs.

'Global worming': first record of an epidemic of Triaenophorus crassus in a population of Arctic charr Salvelinus umbla

In May 2005, an epidemic of the cestode Triaenophorus crassus occurred in the Salvelinus umbla population of Lake Grundlsee, an oligotrophic Austrian Alpine Lake. Based on catches with a standardized multi-mesh gillnet survey 53% of S. umbla were infected with up to 17 cysts of T. crassus per fish. This is the first documented record of an epidemic of this tapeworm in S. umbla.

Limnological Characterization of Volcanic Crater Lakes on Uvea Island (Wallis and Futuna, South Pacific)

Abstract: Species composition and vertical distribution of planktonic organisms in Lakes Lalolalo, Lanutavake, and Lano on the Pacific island of Uvea were investigated in relation to physicochemical water column profiles of temperature, conductivity, dissolved oxygen, and pH. The meromictic lakes Lalolalo (maximum depth 88.5 m) and Lanutavake (23.6 m) exhibited a strong chemocline with anoxic conditions below 10 m depth. Mixis was inhibited by sheltered topography, thermal stratification, and in Lalolalo a strong halocline. Crustaceans and rotifers were limited to the oxygenated epilimnion, but diversity and density of ciliates were highest within and below the chemocline. In Lalolalo, euryhaline rotifers dominated the community, reflecting the brackish condition of the lake. Species richness and densities were highest within the shallow lake Lano (3.5 m). On a calm day, hypoxic conditions occurred near the sediment-water interface, but higher oxygen concentrations were observed after heavy winds, indicating occasional mixis. In total, 32 phytoplankton species, 23 ciliate taxa, 18 rotiferan, 1 cladoceran, 1 copepod, and 1 gastrotrich species were identified in the pelagic zones of all three lakes.