Ori Segev

Long-Distance Movements by Fire Salamanders (Salamandra Infraimmaculata) and Implications for Habitat Fragmentation

Dispersal may be particularly important for the regional persistence of metapopulations that experience local extinctions. Some amphibian species are structured as metapopulations. Long-term persistence of these species should depend on natural connections between local subpopulations through dispersal. We explored movement distances of fire salamander adults (Salamandra infraimmaculata), a locally endangered species, on Mt. Carmel, northern Israel, and investigated the implications of movement for persistence of populations. During the breeding seasons (November-March) of 1999-2000 and 2002-2006, capture-recapture surveys were conducted around four breeding sites and along unpaved roads connecting them. Out of 300 adult salamander captures, 72 cases were recaptures. Most of the recaptures were in the same site as the initial capture. In eight cases (11%), however, salamanders were recaptured at least 400 m away from the first site. The maximum direct distances between capture-recapture sites (1100-1300 m...

THE MALE MATING SYSTEM IN A DESERT WIDOW SPIDER

Abstract Competition among males is a major force shaping sexual selection. We investigated the male mating strategy of the widow spider Latrodectus revivensis, a desert species with an annual life cycle. Based on morphology of the sperm storage organs reported for female Latrodectus, we predicted that males should guard sub-adult or virgin adult females. In a natural population, we found that males were generally monogamous, cohabiting longer with sub-adult females approaching the final molt than with adult females. Nevertheless, both the duration and timing of male cohabitation were highly variable. Males were found with females from a few days before or after female maturation to over two months after maturation. Maturation of males and females peaked in spring, with a second, smaller peak in summer. Adult males that matured in spring were larger than those maturing later in the summer, while for adult females the pattern was reversed. We suggest that large males of L. revivensis that mature in spring maximize reproductive success by mating with virgins. Late males will gain greater reproductive success from mating with large, late-maturing females, but the scarcity of these females in the population at this season may make opportunistic mating with non-virgin females a viable strategy.

Priority effects of the early breeding fire salamander on the late breeding banded newt

Early breeding intraguild predators may have advantages over late breeding predators via priority effects; early breeding predators may reduce shared prey resources before late breeders appear and may also prey upon the late breeders. Here we show that predatory larvae of the late-breeding predatory banded newt, Triturus vittatus vittatus, occupy the same temporary pond toward the end of the developmental period of the early-breeding predatory fire salamander, Salamandra salamandra, resulting in a large size disparity between larvae of these two species while they co-occur. We conducted outdoor artificial pool experiments to assess priority effects of large larval Salamandra at the end of their larval development period, on recently hatched larval Triturus. We also assessed how artificial vegetation may influence larval Triturus performance in the presence or absence of Salamandra Salamandra, introduced into the experimental pools two weeks prior to the newt larvae, strongly reduced invertebrate prey abundance shared by these two predatory urodeles and with only a one week period of overlap, strongly reduced abundance of Triturus larvae. The artificial vegetation had only a small ameliorating effect on Triturus survival when Salamandra was present. Triturus size at metamorphosis (snout-tail length) was significantly larger in the Salamandra pools, presumably due to a combination of a strong “thinning effect” and greater vulnerability of smaller Triturus individuals to predation by Salamandra. Time to metamorphosis was not significantly affected by Salamandra. These results have conservation implications as T. v. vittatus is listed as highly endangered and may also explain the largely negative spatial association of the two species.

Influence of water velocity and predation risk on fire salamander (Salamandra infraimmaculata) larval drift among temporary pools in ephemeral streams

Abstract In ephemeral streams, floods can temporarily connect isolated pools and provide otherwise spatially restricted organisms with the option to stay in or leave a pool. A field survey of the middle-eastern fire salamander (Salamandra infraimmaculata) larvae demonstrated that 18% disappeared from pools during high-discharge events, and ∼2% were found subsequently in downstream pools.We conducted indoor experiments to test whether larvae alter drift rate in response to different velocities and perceived risk of predation. We manipulated flow velocities within the range of natural ephemeral streams during floods. Anesthetized larvae (passive drifters) drifted out of a central pool faster than conscious larvae at low velocities but not at high velocities, suggesting that conscious larvae actively resisted hydraulic pressures. Drift of small larvae out of a pool in the presence of a caged, larger cannibalistic conspecific was faster than in the absence of a predator, indicating that the larvae perceived and attempted to avoid the predator. Our findings confirm that larval drift that occurs from normally isolated temporary pools in ephemeral streams, is in part behaviorally controlled, and can be mediated by predation risk. We suggest that larval drift can serve as a dispersal pathway for amphibians and may be of particular importance at local spatial scales when the terrestrial habitat surrounding breeding sites is fragmented and movement of terrestrial stages is restricted.

Flatworms ( Schmidtea nova) prey upon embryos of the common frog ( Rana temporaria) and induce minor developmental acceleration

Amphibians vary in the degree of pre-metamorphic developmental plasticity in response to risk of predation. Changes in hatching time and development rate can increase egg or tadpole survival respectively by shortening the duration of the more vulnerable stages. The intensity of predator induced developmental response and its direction, i.e. delayed, accelerated, or none, varies considerably between amphibian and predator species. We surveyed freshly deposited clutches of the European common frog Rana temporariain a population in Braunschweig, Germany and found that 62% (N = 20) of the clutches contained planarians ( Schmidtea nova), with an average of 3.94 ± 0.79 and a maximum of 13 planarians per clutch. A laboratory predation experiment confirmed that this planaria preys on R. temporariaeggs and early embryos. We further exposed freshly laid egg masses to either free, caged, or no planarians treatments using floating containers within a breeding pond where the two species co-occur. After 10 days exposure, embryos showed developmental stages 14-25 along the Gosner scale with statistically significant positive effects of both predator treatments. The observed effect was rather slight as predator-exposed individuals showed an increase by a single Gosner stage relative to those raised without planarians. The detected trend suggests that direct and indirect cues from flatworms, rarely considered as anuran predators, might induce a developmental response in R. temporariaearly developmental stages.

EffEcts of background color and prEdation risk on color changE in firE salamandEr larvaE

The threat-sensitivity hypothesis assumes individuals should demonstrate flexibility in response to perceived predation risk and vary the intensity of anti-predator responses in concert with perceived risk of predation. Substrate color matching is adaptive as it enables organisms to become less conspicuous to both their prey and predators. I hypothesized that newborn fire salamander (Salamandra infraimmaculata) larvae will respond fast through physiological color change to contrasting backgrounds, becoming lighter against a white background and darker against a black background. Additionally, in accordance with the threat-sensitivity hypothesis, I expected a background color x predator interaction—i.e., that predator presence will further enhance the focal larvae color-matching response. To explicitly test these hypotheses I conducted a replicated outdoor mesocosm experiment. I used a two-by-two factorial design: pools of black or white background color crossed with the presence or absence of a larger can...

Year-round activity patterns in a hyperdiverse community of rainforest amphibians in Madagascar

Madagascar hosts a high diversity of amphibians estimated at over 500 species, nearly all of them endemic. Surprisingly few data are available on the activity cycles of this fauna, despite its importance for ecological, evolutionary and conservation research. Here we report the results of a year-round survey of amphibians along a transect bordering the Analamazaotra forest near Andasibe in central eastern Madagascar. During 120 transect walks evenly spaced through the year, a total of 2530 individuals of 40 species of anurans was observed. Abundance was higher during the warm/rainy season (December to April) and peaked in February. Of the five climatic predictors measured, only mean temperature and relative humidity showed high importance values, and multi-model averages indicate that these two variables have a strong effect on amphibian abundance along the transect. Species richness showed no evident peak during the study period and was best explained by a model including average temperature and rainfall. Canonical correspondence analysis indicates that Boophis sibilans, B. tephraeomystax, B. boehmei and Plethodontohyla notosticta were more frequently encountered along the transect on cold and humid days while Plethodontohyla mihanika, Gephyromantis boulengeri and Spinomantis aglavei were distinctly more abundant on cold and dry days, and Paradoxophyla palmata on warm and dry days. The results of our study flag a number of species as suitable candidates for future monitoring initiatives and suggest that a simple combination of visual and acoustic surveys can estimate amphibian activity with high sample sizes in Madagascar’s rainforests.

Temporal migration patterns and mating tactics influence size-assortative mating in Rana temporaria

Birds of a feather flock together. This is also true for the European common frog where mating of similar sized individuals is more likely. But, how they assort is a rather complex mechanism. Aside from mate choice behavior and male–male competition, size dependent temporal migration patterns cause assortative mating. Larger males and females reach breeding ponds earlier in the season and are thus more likely to meet.

Testing the link between perceived and actual risk of predation: mosquito oviposition site selection and egg predation by native and introduced fish

Summary According to the threat-sensitivity hypothesis, prey avoidance behaviour should reflect the magnitude of predation risk. Since predation can strongly affect reproduction success, ovipositing females are expected to adaptively adjust their predator avoidance response, or local breeding patch selectivity, in accordance with the perceived level of threat posed for their progeny by specific predators. However, association between avoidance and predation can be disrupted when the prey and the predator lack spatiotemporal opportunities to co-evolve, such as in cases of non-native predator introductions. We examined the interactions between mosquitoes (from the genus Culex) and three species of sympatric predaceous freshwater fish, a native cyprinid Barbus paludinosus, a cichlid Pseudocrenilabrus philander and an introduced poeciliid, the western mosquitofish Gambusia affinis. In an outdoor mesocosm experiment, we quantified patterns of Culex oviposition site selection across fish species using free-roaming, caged and fish-free treatments. In a complementary laboratory experiment, we tested the effectiveness of each fish species as predators of mosquito eggs and larvae. Synthesis and applications. We found evidence for: (i) mosquito egg raft predation by free-roaming fish; (ii) fish-specific avoidance by ovipositing Culex; and (iii) a positive association between fish-specific oviposition avoidance and fish-specific efficiency as an egg predator. These results contribute towards a better understanding of predator–prey co-evolution, predator-borne cue recognition, and suggest local native fish, the southern mouthbrooder Pseudocrenilabrus philander, as an alternative to Gambusia for the biocontrol of Culex mosquitoes.

Compassionate approaches for the conservation and protection of fire salamanders

The Near Eastern fire salamander, Salamandra infraimmaculata , is considered an endangered species in Israel and is near-threatened regionally. For 25 years, our laboratory has sought ethical sampling methods to protect individuals and populations of Salamandra . To “mark” individuals for estimating dispersal and population size, we use non-invasive individual-specific markings from photographs of larvae and adults. We demonstrated through mesocosm experiments (which are less mortality-driven than in nature) that exotic Gambusia affinis have extreme negative mortality effects on Salamandra larvae. From a compassionate conservation aspect, G. affinis should not be killed and placed in habitats where amphibians are not in danger and mosquitoes can be controlled. We identified breeding-site characteristics demonstrating that permanent breeding sites support larger adult populations than temporary breeding sites. For population genetics studies, we take minimal sized tail tips from adults (which have no adverse effects) for microsatellite data. For gene expression studies, rather than sacrifice entire bodies, we demonstrated that by taking only small larval tail tips, we could follow gene expression. We additionally demonstrated that tail tip removal does not affect survival, time to or size at metamorphosis. We documented high road kill rates at a specific breeding site. To prevent potential disease spread, we sterilize boots and sampling gear. We use results for implementing or recommending conservation of individuals and populations – e.g., identifying: movement corridors for breeding site dispersal; roadkill hotspots for under-road tunnels; suitable habitat for pool construction for more effective conservation; utilizing population genetics for recommending management units; information on demography and genetic diversity to identify hotspots for conservation; removal of Gambusia for amphibian protection.