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1.
Abstract In a ‘restinga’ habitat of southeastern Brazil, we studied the food habits and the microhabitat use of two lizards with distinct foraging modes: the tropidurid Tropidurus torquatus, a sit-and-wait predator, and the teiid Cnemidophorus ocellifer, a wide forager. The diet of the two species differed strongly, indicating a low level of similarity in their trophic niche. The sit-and-wait predator fed mainly on mobile prey, whereas the wide forager fed mainly on sedentary prey (larvae). The spatial niche breadth of T. torquatus was larger than that of C. ocellifer. Despite interspecific differences, the two species overlapped greatly in micro-habitat use. The data indicate that at Linhares the two lizard species differed more in food resources than in microhabitat, and that most of the food differences reflect the foraging patterns of the species.  相似文献   

2.
Variation in learning abilities within populations suggests that complex learning may not necessarily be more adaptive than simple learning. Yet, the high cost of complex learning cannot fully explain this variation without some understanding of why complex learning is too costly for some individuals but not for others. Here we propose that different social foraging strategies can favor different learning strategies (that learn the environment with high or low resolution), thereby maintaining variable learning abilities within populations. Using a genetic algorithm in an agent-based evolutionary simulation of a social foraging game (the producer-scrounger game) we demonstrate how an association evolves between a strategy based on independent search for food (playing a producer) and a complex (high resolution) learning rule, while a strategy that combines independent search and following others (playing a scrounger) evolves an association with a simple (low resolution) learning rule. The reason for these associations is that for complex learning to have an advantage, a large number of learning steps, normally not achieved by scroungers, are necessary. These results offer a general explanation for persistent variation in cognitive abilities that is based on co-evolution of learning rules and social foraging strategies.  相似文献   

3.
This paper gives proof of convergence for a learning algorithm that describes how anoles (lizards found in the Caribbean) learn foraging threshold distance. An anole will pursue a prey if and only if it is within this threshold of the anole's perch. The learning algorithm was proposed by Roughgarden and his colleagues. They experimentally determined that this algorithm quickly converges to the foraging threshold that is predicted by optimal foraging theory. We provide analytic confirmation that the optimal foraging behavior as predicted by Roughgarden's model can be attained by a lizard that follows this simple and zoologically plausible rule of thumb. Copyright 1999 Academic Press.  相似文献   

4.
Life histories can reveal important information on the performance of individuals within their environment and how that affects evolutionary change. Major trait changes, such as trait decay or loss, may lead to pronounced differences in life history strategies when tight correlations between traits exist. Here, we show that three congeneric hyperparasitoids (Gelis agilis, Gelis acarorum and Gelis areator) that have diverged in wing development and reproductive mode employ markedly different life history strategies. Potential fecundity of Gelis sp. varied, with the wingless G. acarorum maturing a much higher number of eggs throughout life compared with the other two species. Realized lifetime fecundity, in terms of total offspring number was, however, highest for the winged G. areator. The parthenogenic G. agilis invests its resources solely in females, whilst the sexually reproducing species both invested heavily in males to reduce competitive pressures for their female offspring. Longevity also differed between species, as did the direction of the reproduction-longevity trade-off, where reproduction is heavily traded off against longevity only in the asexual G. agilis. Resting metabolic rates also differed between the winged and wingless species, with the highest metabolic rate observed in the winged G. areator. Overall, these geline hyperparasitoids showed considerable divergence in life history strategies, both in terms of timing and investment patterns. Major trait changes observed between closely related species, such as the loss of wings and sexual reproduction, may contribute to the divergence in key life history traits.  相似文献   

5.
Eggs from congeneric gonochoristic and parthenogenetic whiptail lizards were incubated at various temperatures. There was no significant deviation from a sex ratio of one-half in the sexual species at any temperature, whereas no males were produced in the parthenogenetic species. Temperature-dependent sex determination appears to be completely absent in these lizards.  相似文献   

6.
7.
Bo Wang  Gang Wang  Jin Chen 《Plant Ecology》2012,213(8):1329-1336
Seed predation and dispersal by scatter-hoarding rodents are key processes that determine seed survival, and thus, plant regeneration within forests. For decades, there has been much debate on the important effects of seed size (one of the most important seed traits) on rodent foraging preference. Furthermore, the possible selective forces in the evolution of seed size may be influenced by primary selectivity and how rodents treat seeds after harvesting. In this study, different-sized seeds from four species (Pinus armandii, Pinus densata, Abies sp., and Viburnum sp.) harvested by scatter-hoarding rodents were studied in an alpine forest in Southwestern China for two consecutive years. Our results showed that seed size influenced rodent foraging preferences, with bigger seeds being preferred over smaller seeds, within and across species. Rodents only removed and cached the larger seeds of P. armandii, and ate the seeds of the other three species in situ. Rodents are purely seed predators for these three species. For the cached seeds of P. armandii, significantly positive correlations were observed between seed size and dispersal distance among both primary and secondary cached seeds in 2006, but not in 2005. Our results indicate that among many coexisting species with widely different-sized seeds, scatter-hoarding rodents played important roles in the seed dispersal of the big-seeded species alone. This caching behavior could offset the limited seed dispersal of large-seeded and wingless species (P. armandii), in comparison with that of small winged seed species (P. densata and Abies sp.) and frugivore-dispersed species (Viburnum sp.).  相似文献   

8.
Foraging behaviors exist along a continuum from highly sedentary, ambush foraging, to more continuous searching, or active foraging. Foraging strategies, or modes, are defined based upon locomotor behaviors (e.g. percent time moving, moves per minute). In lizards, traits correlated with ambush and active foraging have been of interest for some time; however, general patterns of correlated evolution between locomotor morphology and locomotor behavior have only recently begun to be quantified. In this study, variation in hindlimb morphology is investigated in a model group of lizard species that vary between active foraging and more sedentary (or mixed) foraging mode. Canonical variates analysis reveals that the two active foraging species occupy similar regions of the morphospace, while the two more sedentary species occupy different regions. The active foraging species have a narrow pelvis with shorter tibia and femora. The more sedentary species have a wide pelvis, long tibia and femora, and slightly longer metatarsals. Phylogenetic patterns of trait variation were examined through ancestral character state reconstruction and show morphological shifts in concert with foraging mode in these species. The observed shifts in locomotor morphology are discussed in light of published data on sprint speed and endurance in these species. Together, the data show that linking morphological variation to variation in stride length and stride frequency is critical to understanding the evolution of locomotor performance. Much more stride length and frequency data are needed among ambush, mixed, and active foraging species because these parameters, and their morphological components, are likely correlated with variation in food acquisition mode.  相似文献   

9.
Spatial and non-spatial serial discrimination reversal performance was investigated in guinea pigs over eleven reversals. Difference in learning ability between albino and pigmented strains was not evident on spatial or non-spatial SDR tasks. The guinea pigs' ability to learn rapidly successive spatial and non-spatial reversals with increasing proficiency corresponds well with previous published findings using other mammalian species. These studies also demonstrated behavioural research with the guinea pig to require extended periods of intensive experimental management.  相似文献   

10.
Paula S  Pausas JG 《Oecologia》2011,165(2):321-331
Drought and fire are prevalent disturbances in Mediterranean ecosystems. Plant species able to regrow after severe disturbances (i.e. resprouter life history) have higher allocation to roots and higher water potential during the dry season than coexisting non-resprouting species. However, seedlings of non-resprouters have a higher survival rate after summer drought. We predict that, to counteract their shallow-rooting systems and to maximize seedling survival, non-resprouters have root traits that confer higher efficiency in soil resource acquisition than resprouters. We tested this prediction in seedlings of less than 1.5 months old. We select 13 coexisting woody species (including both resprouters and non-resprouters), grew them in a common garden and measured the following root traits: length, surface, average diameter, root tissue density (RTD), specific root length (SRL), surface:volume ratio (SVR), specific tip density (STD), tip distribution in depth, internal links ratio (ILR), and degree of branching. These root traits were compared between the two resprouting life histories using both standard cross-species and phylogenetic-informed analysis. Non-resprouters showed higher SRL and longer, thinner and more branched laterals, especially in the upper soil layers. The external links (i.e. the most absorptive root region) were also more abundant, longer, thinner and with higher SVR for non-resprouters. The results were supported by the phylogenetic-informed analysis for the root traits most strongly related to soil resource acquisition (SRL, SVR and branching pattern). The seedling root structure of non-resprouters species allows them to more efficiently explore the upper soil layer, whereas seedling roots of resprouters will permit both carbon storage and deep soil penetration.  相似文献   

11.
Closely related lacertid lizards (Eremias, Nucras) in the Kalahari desert differ in patterns of foraging behaviour. Some species are relatively sedentary (‘sit-and-wait’) whereas others are more active (‘widely-foraging’) predators. We determined whether whole-animal locomotor capacities (cruising endurance on a treadmill, initial speed and maximum burst speed in a racetrack, and sprint endurance in a torus-shaped track) correlated with interspecific differences in foraging behaviour. Two of three widely-foraging species had greater cruising endurance, graater sprint endurance, but lower burst speed than did a sit-and-wait species. However, the two species that sprinted quickly also had limited endurance, and vice versa. Pre-feeding negatively influenced endurance but not sprint capacity. Theoretical models of foraging behaviour should recognize that ectotherms have limited endurance, that there can be a trade-off between speed and endurance, and that pre-feeding can reduce some aspects of locomotor capacity.  相似文献   

12.
Polmunate land snails are subject to stress conditions in their terrestrial habitat, and depend on a range of behavioural, physiological and biochemical adaptations for coping with problems of maintaining water, ionic and thermal balance. The involvement of the heat shock protein (HSP) machinery in land snails was demonstrated following short-term experimental aestivation and heat stress, suggesting that land snails use HSPs as part of their survival strategy. As climatic variation was found to be associated with HSP expression, we tested whether adaptation of land snails to different habitats affects HSP expression in two closely related Sphincterochila snail species, a desert species Sphincterochila zonata and a Mediterranean-type species Sphincterochila cariosa. Our study suggests that Sphincterochila species use HSPs as part of their survival strategy following desiccation and heat stress, and as part of the natural annual cycle of activity and aestivation. Our studies also indicate that adaptation to different habitats results in the development of distinct strategies of HSP expression in response to stress, namely the reduced expression of HSPs in the desert-inhabiting species. We suggest that these different strategies reflect the difference in heat and aridity encountered in the natural habitats, and that the desert species S. zonata relies on mechanisms and adaptations other than HSP induction thus avoiding the fitness consequences of continuous HSP upregulation.  相似文献   

13.
14.
Summary Daily energy metabolism and water flux were measured with doubly labeled water in the free-living insectivorous lizards Cnemidophorus tigris (mean body mass 15.7 g) and Callisaurus draconoides (8.6 g) in June 1979 in the Colorado Desert of California. C. tigris was an active forager; it spent 91% of its 5-h daily activity period in movement. C. draconoides was a sit-and-wait predator; it spent less than 2% of its 10-h activity period in movement. C. tigris had significantly higher rates of field energy metabolism and water influx (210 Jg-1 day-1, 36.8 ul H2O g-1 day-1, N=19) than C. draconoides (136, 17.1, N=18). There were no significant differences between the sexes within either species.The extra costs of free existence were calculated from differences between field metabolic rates and maintenance costs estimated from laboratory respirometry. Rates of energy metabolism during the field activity period were about 1.5x resting levels at 40° C (field active body temperature) for C. draconoides and 3.3 x resting levels at 40° C (field active body temperature) for the more active C. tigris. Feeding rates calculated from water influx data were 13.3 mg g-1 day-1 for C. tigris and 5.8 mg g-1 day-1 for C. draconoides. Though C. tigris had a high rate of energy expenditure, its foraging efficiency was higher than C. draconoides'.  相似文献   

15.
1. We investigated the association between field body temperatures (Tb), field air temperatures (Ta), and their differences (Δ) with measurements of foraging activity (percentage of time moving (PTM), number of movements per minute (MPM) and proportion of prey attacked while moving (PAM)) for 25 species of lacertid lizards.

2. Lizards active at relatively high field body temperatures tended to have higher PTM and PAM values. We found no association between temperatures and MPM. The difference Δ did not co-vary with PTM and MPM, but showed a positive trend with PAM.

3. Our results seem robust with regard to the assumptions of different models of evolution and to the phylogenetic trees used.

Keywords: Foraging; Thermal ecology; Lizard; Lacertidae; Evolution  相似文献   


16.
The acquisition of information is a fundamental part of individual foraging behaviour in heterogeneous and changing environments. We examine how foragers may benefit from utilizing a simple learning rule to update estimates of temporal changes in resource levels. In the model, initial expectation of resource conditions and rate of replacing past information by new experiences are genetically inherited traits. Patch-time allocation differs between learners and foragers that use a fixed patch-leaving threshold throughout the foraging season. It also deviates from foragers that obtain information about the environment at no cost. At the start of a foraging season, learners sample the environment by frequent movements between patches, sacrificing current resource intake for information acquisition. This is done to obtain more precise and accurate estimates of resource levels, resulting in increased intake rates later in season. Risk of mortality may alter the trade-off between exploration and exploitation and thus change patch sampling effort. As lifetime expectancy decreases, learners invest less in information acquisition and show lower foraging performance when resource level changes through time.  相似文献   

17.
Lennart Persson 《Oecologia》1985,67(3):338-341
Summary The foraging efficiency of a visually feeding fish, perch (Perca fluviatilis) was studied on two prey species (Daphnia magna and Chaoborus obscuripus) presented either separately or combined. It is shown that when both prey species are present, the foraging efficiency of the predator is reduced. This is due to the predator's inability to simultaneously cope with prey species with different anti-predatory behaviour. In the mixed-meal experiment the predator captured both prey species in equal proportions in disagreement with optimal foraging models assuming that handling time and encounter rate for a prey species are independent of other prey species. The results are, however, in agreement with optimal foraging models assuming that handling time and encounter rate are influenced by short time learning.  相似文献   

18.

Though biological invasions constitute one of the biggest threats for global biodiversity, our understanding of the mechanisms that enable invasive species to outperform native species is still limited, especially, in terms of behavior. Most available studies have examined behavioral traits which favor invasive species on the later stages of invasion, however, our knowledge on earlier stages, namely, when alien species face novel environments and must exploit new resources, remains obscure. Here, we focus on one crucial behavioral trait, finding food. The Italian wall lizard (Podarcis siculus) has been widely introduced and established viable populations in S. Europe and N. America. We examined whether P. siculus has enhanced exploratory behavior and abilities to find food compared to two native congeneric species with which it may come in contact in the near future, an insular endemic (P. milensis) and a widely distributed lizard (P. erhardii). We performed a Y-maze experiment, in which we varied arm markings in a standard way to prevent learning. Podarcis siculus was more efficient than its congenerics in finding and consuming food. This exploitative superiority was persistent, more frequent and repetitive. Interesting behavioral differences were also detected within the native species. Some P. milensis individuals showed no interest in exploring the maze, while few P. erhardii individuals remained rather indifferent to food even after detecting it. Our results suggest that the invasive P. siculus displays behavioral traits that could provide better opportunities for survival in the new environment and thus facilitate establishment even in the presence of congenerics. This provides further support to the idea that behavior plays a crucial role in animal invasions.

  相似文献   

19.
In this work, a new plant-inspired optimization algorithm namely the hybrid artificial root foraging optimizion (HARFO) is proposed, which mimics the iterative root foraging behaviors for complex optimization. In HARFO model, two innovative strategies were developed: one is the root-to-root communication strategy, which enables the individual exchange information with each other in different efficient topologies that can essentially improve the exploration ability; the other is co-evolution strategy, which can structure the hierarchical spatial population driven by evolutionary pressure of multiple sub-populations that ensure the diversity of root population to be well maintained. The proposed algorithm is benchmarked against four classical evolutionary algorithms on well-designed test function suites including both classical and composition test functions. Through the rigorous performance analysis that of all these tests highlight the significant performance improvement, and the comparative results show the superiority of the proposed algorithm.  相似文献   

20.
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