摘要: Environmental warming places physiological constraints on organisms, which may be mitigated by their feeding behavior. Theory predicts that consumers should increase their feeding selectivity for more energetically valuable resources in warmer environments to offset the disproportionate increase in metabolic demand relative to ingestion rate. This may also result in a change in feeding strategy or a shift towards a more specialist diet. This study used a natural warming experiment to investigate temperature effects on the feeding selectivity of three freshwater invertebrate grazers: the snail Radix balthica, the blackfly larva Simulium aureum, and the midgefly larva Eukiefferiella minor. Chesson's Selectivity Index was used to compare the proportional abundance of diatom species in the guts of each invertebrate species with corresponding rock biofilms sampled from streams of different temperature. The snails became more selective in warmer streams, choosing high profile epilithic diatoms over other guilds and feeding on a lower diversity of diatom species. The blackfly larvae appeared to switch from active collector gathering of sessile high profile diatoms to more passive filter feeding of motile diatoms in warmer streams. No changes in selectivity were observed for the midgefly larvae, whose diet was representative of resource availability in the environment. These results suggest that key primary consumers in freshwater streams, which constitute a major portion of invertebrate biomass, can change their feeding behavior in warmer waters in a range of different ways. These patterns could potentially lead to fundamental changes in the flow of energy through freshwater food webs.

摘要: Batesian mimicry is the process in which harmless species adopt the appearance of a dangerous, aposematic species. In some prey species, both Batesian mimetic and non-Batesian morphs coexist, presupposing that both morphs have to be evolutionarily advantageous. The viperine snake, Natrix maura, exhibits a zigzag dorsal pattern and antipredatory behavior that mimics European vipers. This snake also has a striped dorsal pattern that coexists with the zigzag pattern. We have examined whether individuals belonging to different geographically structured clades were more likely to exhibit a certain dorsal pattern, and whether the zigzag pattern has a protective function by exposing artificial snakes to predation in natural environments, in addition to comparing antipredatory behavior between zigzag and striped snakes also in natural environments. Our results indicate that the striped pattern was not geographically structured, but habitat-dependent. Aerial predators less frequently attacked zigzag plasticine models than striped or unpatterned models. We detected a shift in antipredator behavior between the 2 morphs, as Batesian mimicking N. maura responded to an approaching potential predator by remaining immobile or fleeing at shorter distances than did striped ones. We conclude that Batesian mimics maintain the cryptic and aposematic value by resembling vipers, whereas in open habitats the non-Batesian mimic has altered its antipredator behavior to maintain its fitness.

摘要: Climate change is ranked as one of the most severe threats to global biodiversity. This global phenomenon is particularly true for reptiles whose biology and ecology are closely linked to climate. In this study, we used over 1,300 independent occurrence points and different climate change emission scenarios to evaluate the potential risk of changing climatic conditions on the current and future potential distribution of a rock-dwelling lizard; the velvet gecko. Furthermore, we investigated if the current extent of protected area networks in Australia captures the full range distribution of this species currently and in the future. Our results show that climate change projections for the year 2075 have the potential to alter the distribution of the velvet gecko in southeastern Australia. Specifically, climate change may favor the range expansion of this species to encompass more suitable habitats. The trend of range expansion was qualitatively similar across the different climate change scenarios used. Additionally, we observed that the current network of protected areas in southeast Australia does not fully account for the full range distribution of this species currently and in the future. Ongoing climate change may profoundly affect the potential range distribution of the velvet gecko population. Therefore, the restricted habitat of the velvet geckos should be the focus of intensive pre-emptive management efforts. This management prioritization should be extended to encompass the increases in suitable habitats observed in this study in order to maximize the microhabitats available for the survival of this species.

摘要: In many sexually reproducing species, individuals can gather information about potential mates by observing their mating success. This behavioral pattern, that we call mate-copying, was reported in the fruit fly Drosophila melanogaster where females choosing between 2 males of contrasting phenotypes can build a preference for males of the phenotype they previously saw being chosen by a demonstrator female. As sex ratio is known to affect mate choice, our goal was to test whether mate-copying is also affected by encountered sex ratios. Thus, we created a gradient of sex ratio during demonstrations of mate-copying experiments by changing the number of females observing from a central arena 6 simultaneous demonstrations unfolding in 6 peripheral compartments of a hexagonal device. We also tested whether the sex ratio experienced by females during demonstrations affected their choosiness (male courtship duration and double courtship rate) in subsequent mate-choice tests. Experimental male: female sex ratio during demonstrations did not affect mate-copying indices, but positively affected the proportion of both males courting the female during mate-choice tests, as well as male courtship duration, the latter potentially explaining the former relationship. As expected, the sex ratio affected female choosiness positively, and Drosophila females seem to have evolved a mate-copying ability independently of sex ratio, and a capacity to adapt their choosiness to male availability. This suggests that, as in many animal species, individuals, especially females, can adapt their mate choice depending on the current sex ratio.

摘要: Primates have been found to differ widely in their taste perception and studies suggest that a coevolution between plant species bearing a certain taste substance and primate species feeding on these plants may contribute to such between-species differences. Considering that only platyrrhine primates, but not catarrhine or prosimian primates, share an evolutionary history with the neotropical plant Stevia rebaudiana, we assessed whether members of these three primate taxa differ in their ability to perceive and/or in their sensitivity to its two quantitatively predominant sweettasting substances. We found that not only neotropical black-handed spider monkeys, but also paleotropical black-and-white ruffed lemurs and Western chimpanzees are clearly able to perceive stevioside and rebaudioside A. Using a two-bottle preference test of short duration, we found that Ateles geoffroyi preferred concentrations as low as 0.05mM stevioside and 0.01mM rebaudioside A over tap water. Taste preference thresholds of Pan troglodytes were similar to those of the spider monkeys, with 0.05mM for stevioside and 0.03mM for rebaudioside A, whereas Varecia variegata was slightly less sensitive with a threshold value of 0.1mM for both substances. Thus, all three primate species are, similar to human subjects, clearly more sensitive to both steviol glycosides compared to sucrose. Only the spider monkeys displayed concentration-response curves with both stevioside and rebaudioside A which can best be described as an inverted U-shaped function suggesting that Ateles geoffroyi, similar to human subjects, may perceive a bitter side taste at higher concentrations of these substances. Taken together, the results of the present study do not support the notion that a co-evolution between plant and primate species may account for between-species differences in taste perception of steviol glycosides.