The influence of terrain age and altitude on the arthropod communities found on recently deglaciated terrain

Climate warming has been more pronounced in the Arctic than elsewhere, resulting in a recent rapid glacial retreat. Over 85% of the Almajallojekna glacier has disappeared over the last 115 years and it is one of the fastest retreating glaciers in Sweden. In 2011 and 2012, at 18 sites in the vicinity of the remaining glacier network, we sampled arthropods and related the species richness, abundance and proportion of herbivores to altitude （ranging from 824 to 1,524 m.a.s.1.） and the age of the site （ranging from 0 to 〉 115 years）. Temperature was measured at six sites and the average annual air temperature ranged from -3.7℃ to 1.1℃. In total, we recorded 3,705 arthropods from 117 species in nine different taxonomic groups. The most abundant and species-rich group was Coleoptera （1,381 individuals, 41 species） followed by Araneae （1,050 individuals, 15 species） and Macrolepidoptera （732 individuals, 17 species）. Only at lower altitudes did the abundance and species richness of arthropods increase with increasing age of the site. The results were consistent among the studied taxonomic groups and when controlling for sam- piing intensity using two different approaches. The proportion of herbivores decreased with increasing age of the site and with increasing altitude. Clearly, altitude appears more important than the age of the site and, at higher altitudes, abundance, species richness and herbivory are low [Current Zoology 60 （2）： 203-220, 2014].     

Mobility affects copulation and oviposition dynamics in Pieris brassicae in seminatural cages

When, how often and for how long organisms mate can have strong consequences for individual fitness and are crucial aspects of evolutionary ecology. Such determinants are likely to be of even greater importance in monandrous species and species with short adult life stages. Previous work suggests that mobility, a key dispersal? related trait, may affect the dynamics of copulations, but few studies have investigated the impact of individual mobility on mating latency, copulation duration and oviposition latency simultaneously. In this paper, we monitored the copulation dynamics of 40 males and 40 females, as well as the oviposition dynamics of the females of the Large White butterfly Pieris brassicae, a facultative long-distance disperser butterfly. Individuals from a breeding were selected to create a uniform distribution of mobility and we recorded the timing, number and duration of all copulations in a semiexperimental system. We showed that mobility, measured as the time spent in flight under stressful conditions (a proxy of dispersal tendency), correlates with all aspects of copulation dynamics: mobile males and females mated earlier and for shorter periods than less mobile individuals. In turn, late mating females increased the time between copulation and oviposition. These results feed the previously described mobility syndrome of R brassicae, involving morphological and physiological characters, with life-history traits. We suggest that the reduction of mating latency and copulation duration has an adaptive value in dispersing individuals, as their life expectancy might be shorter than that of sedentary individuals.     

Seasonal changes on two different spatial scales： response of aquatic invertebrates to water body and microhabitat

Knowledge about the spatial and temporal scales of both habitat use and the functional significance of different adaptations is essential for an understanding of the population dynamics of invertebrate assemblages. This fundamental knowledge is not only interesting from an academic point of view, but is sorely lacking and needed in the field of restoration ecology. Many species are threatened due to degradation. Knowing what environmental conditions are needed dtLring the life cycle of these species is important in the design of restoration measures which aim to lift existing bottlenecks for threatened species. To assess the relative importance of water type and microhabitat in structuring the invertebrate assemblage during different seasons, invertebrates were sampled in three water bodies differing in trophic level and acidity. Different parts within a water body （microhabitats） were sampled separately and each water body was sampled in all four seasons. Results show that water body is an important factor structuring the invertebrate assemblage early in the season, whereas microhabitat became more important later in the season. Structural complexity of microhabitats was related to the type of locomotion employed by invertebrates. Seasonal differences could be related to population dynamics （reproduction, mortality）. Moreover, fluctuations in resource availability were expected to differ between the water bodies, with highest fluctuations in the eutrophic water body and with fluctuations becoming less predictable later in the season. This was confirmed by the data： species synchronization to pulses in food availability was strongest in the eutrophic water body. Moreover, synchronization was strongest in summer, while in autumn waters were invaded by dispersive species. Based on these results a synthesis is presented on the functioning of the different waters during the different seasons.     

Nutritional stress reduces flight performance and exploratory behavior in a butterfly

Anthropogenic global change, including agricultural intensification and climate change, poses a substantial challenge to many herbivores due to a reduced availability of feeding resources. The concomitant food stress is expected to detrimentally affect performance, amongst others in dispersal-related traits. Thus, while dispersal is of utmost importance to escape from deteriorating habitat conditions, such conditions may negatively feedback on the ability to do so. Therefore, we here investigate the impact of larval and adult food stress on traits related to dispersal ability, including morphology, physiology, flight performance, and exploratory behavior, in a butterfly. We show that inadequate nutrition during development and in the adult stage dim inishes flight performance, despite som e reallocation of somatic resources. Detrimental effects of food stress on flight performance were mainly caused by reductions in body mass and storage reserves. Similar results were found for exploratory behavior. Furthermore, exploratory behavior was found to be (moderately) repeatable at the individual level, which might indicate the existence of a personality trait. This notion is further supported by the fact that flight performance and exploratory behavior were positively correlated, potentially suggesting the existence of a dispersal syndrome. In summary, our findings may have important implications for dispersal in natural environments, as the conditions requiring dispersal the m ost impair flight ability and thereby likely dispersal rates.     

Seed Dynamics in Relation to Gaps in a Tropical Montane Rainforest of Hainan Island, South China： （I） Seed Rain

Seed dynamics is an important part of stand dynamics in forest ecosystems. In this paper, 26 gaps were randomly selected to study the influence of gaps on the spatial and temporal patterns of seed rains in a tropical montane rainforest of Hainan Island, South China. Three zones for each gap, including outside gap zone （Non-gap）, transitional gap zone （EG-CG）, and central gap zone （CG）, were designed, and fourseed traps （each lm x lm in size） were placed in each zone. Seed rains were collected by these traps every 10 days from June 2001 to May 2002. Seed rain varied greatly with season and generally exhibited a pattern of unimodal change during the study period： seed abundance and species richness were both greater in the wet season than in the dry season. Gaps significantly influenced the temporal patterns of both species richness and density of seed rains. Gaps had no significant influences on the spatial distribution patterns of seed rain species richness, but significantly affected the spatial distribution pattern of seed rain densities. Among the three different zones of gaps, the outside gap zone generally received more seeds inputs than the two other gap zones.     

Different Patterns of Changes in the Dry Season Diameter at Breast Height of Dominant and Evergreen Tree Species in a Mature Subtropical Forest in South China

Information on changes in diameter at breast height （DBH） is important for net primary production （NPP） estimates, timing of forest inventory, and forest management. In the present study, patterns of DBH change were measured under field conditions during the dry season for three dominant and native tree species in a monsoon evergreen broad-leaved forest in the Dinghushan Biosphere Reserve. For each tree species, different patterns of DBH change were observed. In the case of the fast-growing tree species Castanopsis chinensis Hance, large diurnal fluctuations occur, with a peak DBH in the early morning （around 05：00 h） that decreases to a minimum by about 14：00 h. Both Schima superba Gardn. et Chemp and Cryptocarya chinensis （Hance） Hemsh exhibited less diurnal swelling and shrinkage. Diurnal fluctuations for these species were observed on a few occasions over the period of observation. Graphical comparisons and statistical analysis of changes in DBH with meteorological variables indicate that for different trees, the different changes in DBH observed responded to different meteorological variables. Large stem changes were found to occur for Ca. chinensis trees that were associated with variations in solar radiation. However, both S. superba and Cr. chinensis were found to be less sensitive to solar radiation. Changes in the DBH of these two species were found to be controlled mainly by soil temperature and soil moisture. During the later dry season, with a lower soil temperature and soil moisture, all three tree species stopped growing and only negligible shrinkage, expansion, or fluctuation occurred, suggesting that the optimum time to measure tree growth in the Dinghushan Biosphere Reserve is the later dry season.     

Cascade effects of crop species richness on the diversity of pest insects and their natural enemies

Understanding how plant species richness influences the diversity of herbivorous and predatory/parasitic arthropods is central to community ecology.We explore the effects of crop species richness on the diversity of pest insects and their natural enemies.Using data from a four-year experiment with five levels of crop species richness,we found that crop species richness significantly affected the pest species richness,but there were no significant effects on richness of the pests’natural enemies.In contrast,the species richness of pest insects significantly affected their natural enemies.These findings suggest a cascade effect where trophic interactions are strong between adjacent trophic levels,while the interactions between connected but nonadjacent trophic levels are weakened by the intermediate trophic level.High crop species richness resulted in a more stable arthropod community compared with communities in monoculture crops.Our results highlight the complicated cross-trophic interactions and the crucial role of crop diversity in the food webs of agro-ecosystems.     

Comparative studies on histological and ultra-structure of the pituitary of different ploidy level fishes

The histological and ultra-structure of the pituitary in diploid red crucian carp(Carassius auratus red var.),triploid crucian carp and allotetraploid hybrids within and after the breeding season were comparatively studied.The result showed that there were six endocrine cell types in the pituitary of these three kinds of fishes,and there was an obvious difference in cell size among different ploidy level fishes.As for the same type of pituitary cells,the cell size was increased gradually with the in- creasing ploidy level.In the breeding season,the allotetraploid hybrids had higher proportion of go- nadotropin cells(GTH)than triploids,and the triploids had higher proportion of GTH than diploids.The results were related to the earlier sexual maturity of allotetraploid hybrids and sterility of triploid cru- cian carp.On the other hand,among the three kinds of fishes,the proportion of somatotropin(STH) cells in triploids crucian carp was the highest,whereas that in allotetraploid hybrids was the lowest. The results might be connected with the faster growth rate of triploids and slower growth rate of al- lotetraploid hybrids.In addition,in GTH cells of meso-adenohypophysis after the breeding season, there were many endocrine particles in triploids,while those endocrine particles were released from the cells in allotetraploids and diploids.This result showed that the sterility of triploid crucian carp might be related to the hormone which was not released from the GTH cells.In a word,the present study indicated that the differences in the structure of pituitary among different ploidy level fishes contributed to their difference in the growth rate and gonadal development.     

Predicting wild boar damages to croplands in a mosaic of agricultural and natural areas

Crop damages by wildlife is a frequent form of human-wildlife conflict. Identifying areas where the risk of crop damages is highest is pivotal to set up preventive measures and reduce conflict. Species distribution models are routinely used to predict species distribution in response of environmental changes. The aim of this paper was assessing whether species distribution models can allow to identify the areas most at risk of crop damages, helping to set up management strategies aimed at the mitigation of human-wildlife conflicts. We obtained data on wild boar Sus scrofa damages to crops in the Alta Murgia National Park, Southern Italy, and related them to landscape features, to identify areas where the risk of wild boar damages is highest. We used MaxEnt to build species distribution models. We identified the spatial scale at which landscape mostly affects the distribution damages, and optimized the regularization parameter of models, through an information-theoretic approach based on AIC. Wild boar damages quickly increased in the period 2007-2011; cereals and legtmaes were the crops more affected. Large areas of the park have a high risk of wild boar damages. The risk of damages was related to low cover of urban areas or olive grows, intermediate values of forest cover, and high values of shrubland cover within a 2-km radius. Temporally independent validation data demonstrated that models can successfully predict damages in the future. Species distribution models can accurately identify the areas most at risk of wildlife damages, as models calibrated on data collected during only a subset of years correctly predicted damages in the subsequent year [Current Zoology 60 （2）： 170-179, 2014].     

Vocal individuality and rhythm in male and female duet contributions of a nonhuman primate

Duetting,or the stereotypical,repeated and often coordinated vocalizations between 2 individuals arose independently multiple times in the Order Primates.Across primate species,there exists substantial variation in terms of timing,degree of overlap,and sex-specificity of duet contributions.There is increasing evidence that primates can modify the timing of their duet contributions relative to their partner,and this vocal flexibility may have been an important precursor to the evolution of human language.Here,we present the results of a fine-scale analysis of Gursky’s spectral tarsier Tarsius spectrumgurskyae duet phrases recorded in North Sulawesi,Indonesia.Specifically,we aimed to investigate individual-level variation in the female and male contributions to the duet,quantify individual-and pair-level differences in duet timing,and measure temporal precision of duetting individuals relative to their partner.We were able to classify female duet phrases to the correct individual with an 80%accuracy using support vector machines,whereas our classification accuracy for males was lower at 64%.Females were more variable than males in terms of timing between notes.All tarsier phrases exhibited some degree of overlap between callers,and tarsiers exhibited high temporal precision in their note output relative to their partners.We provide evidence that duetting tarsier individuals can modify their note output relative to their duetting partner,and these results support the idea that flexibility in vocal exchanges—a precursor to human language—evolved early in the primate lineage and long before the emergence of modern humans.     

Patterns of tree phenological diversity in dry tropics

Recent phenological studies in tropical deciduous forests revealed a mosaic of vegetation composed of several pheno-phases that are evolved as an adaptation by the species to overcome seasonal drought in different ways. These pheno-phases represent extent of annual deciduousness (～leaflessness) and triggering factors for buds break (e.g. vegetative and flower). Thus, studying patterns of various pheno-phases (phonological diversity) in tropical forest have been thought to provide a potential tool to address critical questions related to climate change modeling and monitoring. In tropics, tree species represent a gradient of deciduousness (from leaf-exchanging species to >6 months deciduous species) and flowering initiation (breaking of flower buds in various part of annual cycle). Both processes are mostly triggered by variation in day length and/or temperature during late dry season/autumn, and/or first significant rain during rainy season. In addition, few factors like drought induced leaf fall and sporadic winter rains are supposed to affect these processes temporarily. Besides, the abundances of pheno-phases (i.e. leafing and flowering) also vary among tropical deciduous forest trees. Presence of such variations in tropical tree pheno-phases and their abundances are reported to vary due to micro-climatic variables and has specific implications in tropical forests. Present paper discusses the existing information on various pheno-phases and their abundances in tropical forests and role of climatic factors on tree phonological diversity. Further, we emphasized the need to develop predicting understanding of impending climatic change (i.e. precipitation and temperature) on diversity of pheno-phases by collecting long-term data on tree pheno-phases through a network of phonological stations in dry tropics.     

Patterns of tree phenological diversity in dry tropics

Recent phenological studies in tropical deciduous forests revealed a mosaic of vegetation composed of several pheno-phases that are evolved as an adaptation by the species to overcome seasonal drought in different ways. These pheno-phases represent extent of annual deciduousness (～leaflessness) and triggering factors for buds break (e.g. vegetative and flower). Thus, studying patterns of various pheno-phases (phonological diversity) in tropical forest have been thought to provide a potential tool to address critical questions related to climate change modeling and monitoring. In tropics, tree species represent a gradient of deciduousness (from leaf-exchanging species to >6 months deciduous species) and flowering initiation (breaking of flower buds in various part of annual cycle). Both processes are mostly triggered by variation in day length and/or temperature during late dry season/autumn, and/or first significant rain during rainy season. In addition, few factors like drought induced leaf fall and sporadic winter rains are supposed to affect these processes temporarily. Besides, the abundances of pheno-phases (i.e. leafing and flowering) also vary among tropical deciduous forest trees. Presence of such variations in tropical tree pheno-phases and their abundances are reported to vary due to micro-climatic variables and has specific implications in tropical forests. Present paper discusses the existing information on various pheno-phases and their abundances in tropical forests and role of climatic factors on tree phonological diversity. Further, we emphasized the need to develop predicting understanding of impending climatic change (i.e. precipitation and temperature) on diversity of pheno-phases by collecting long-term data on tree pheno-phases through a network of phonological stations in dry tropics.     

Seasonal and reproductive variation in chemical constituents of scent signals in wild giant pandas

Seasonally reproducing animals show many behavioral and physiological changes during the mating period, including increased signaling for intrasexual competition and mate attraction. We collected 102 anogenital gland secretions(AGS) from marking trees in Foping Nature Reserve, and used gas chromatography mass spectrometry to analyze these chemical composition. Of these marks, all but one were from males, confirmed with DNA analysis. We found that several chemical constituents, especially volatile compounds, were present only during the mating season and that the relative abundance of many compounds changed as a function of breeding season, whereas nonvolatile compounds were lower in the mating season. This seasonal variation in chemical composition of AGS most likely plays an important role in governing giant panda reproduction, including mate location, attraction, and male-male competition. The chemical properties of many of these putative chemosignals—such as volatility and longevity—are suggestive of these roles, and undoubtedly contribute to successful reproduction for this species with a characteristically sophisticated chemical communication system. We also found a number of important differences between the chemical constituents of AGS from wild pandas and those found in previous studies with captive pandas, suggesting that inappropriate chemosignal composition may contribute to poor reproductive success in captive breeding programs.     

Day length constrains the time budget of aphid predators

Phenology shifts and range expansions cause organisms to experience novel day length-temperature correlations.Depending on the temporal niche,organisms may benefit or suffer from changes in day length,thus potentially affecting phenological adaptation. We assessed the impact of day length changes on larvae of Chrysoperla carnea (Stephens) and Episyrphus balteatus (De Geer),both of which prey on aphids.Larvae ofE.balteatus are night-active,whereas those of C.carnea appear to be crepuscular.We subjected both species in climate chambers to day lengths of 16 :8 L :D and,to circumvent diapause responses,20 :4 L :D.We recorded development times and predation rates of both species. E.balteatus grew 13%faster in the 16 :8 L :D treatment and preyed on significantly more aphids.In contrast,C.carnea grew 13% faster in the 20 :4 L :D treatment and higher predation rates in 20 :4 L :D were marginally significant.Our results show that day length affects development and predation,but that the direction depends on species. Such differences in the use of day length may alter the efficiency ofbiocontrol agents in a changing climate.     

Differences in Thermal Preference and Tolerance among Three Phrynocephalus Lizards （Agamidae） with Different Body Sizes and Habitat Use

We acclimated adults of two viviparous(Phrynocephalus guinanensis and P.vlangalii) and one oviparous(P.versicolor) species of toad-headed lizards(Agamidae) to 28 °C,33 °C and 38 °C to examine whether thermal preference(preferred body temperature,Tp) and thermal tolerance(critical thermal minimum,CTMin;critical thermal maximum,CTMax) were affected by acclimation temperature,and correlate with body size and habitat use.Both Tp and CTMax were highest in P.versicolor and lowest in P.vlangalii,with P.guinanensis in between.The two viviparous species did not differ in CTMin and thermal tolerance range,and they both were more resistant to low temperatures and had a wider range of thermal tolerance than the oviparous species.Both CTMin and CTMax shifted upward as acclimation temperature increased in all the three species.Tp was higher in the lizards acclimated to 33 °C than in those to 28 °C or 38 °C.The range of thermal tolerance was wider in the lizards acclimated to 28 °C than in those to 33 °C or 38 °C.The data showed that:1) thermal preference and tolerance were affected by acclimation temperature,and differed among the three species of Phrynocephalus lizards with different body sizes and habitat uses;2) both Tp and CTMax were higher in the species exchanging heat more rapidly with the environment,and CTMin was higher in the species using warmer habitats during the active season;and 3) thermal preference and tolerance might correlat with body size and habitat use in Phrynocephalus lizards.     

Effect of Seasonality on Distribution of Macroalgae in a Stream System （Xin＇an Spring）in Shanxi Province, North China

A survey of the seasonal distribution of macroalgae in a stream system in Shanxi Province, north China, was undertaken from July 2004 to April 2005. The relative abundance and percentage cover of macroalgae, and several environmental factors were monitored along a 20-m stretch at each of four sites, at intervals of approximately three months （one sampling per season）. Several stream conditions were relatively constant over the sampling period （pH, maximum width and maximum depth）, whereas others exhibited a distinct seasonal pattern （water temperature and specific conductance）, and some fluctuated with no discernable seasonal pattern （current velocity and dissolved oxygen）. Forty-two species of macroalgae were found, with a predominance of Chlorophyta （26 species, 61.9%）. Rhodophyts and Charophyta represented the smallest proportion （1 species each, 2.38%）. Six macroalgae species were the most widespread, occurring in all four sampling sites. Twelve species were found at only one site each. In terms of seasonality, eight species occurred throughout the year, whereas 16 species were found in only one season each. The macroalgal community at Xin＇an Spring was species rich relative to other streams. Species richness per sampling site was negatively correlated with pH. Principal component analysis revealed that no single variable had much influence on the macroalgal seasonal dynamics. We calculated Sorensen similarity indices to compare our study with other continent-wide surveys of stream macroalgae, but the similarity indices were all very low. This study also shows that macroalgae in different locations have significant reproductive isolation.     

Validation of degree-day models for predict!ng the emergence of two fruit flies (Diptera: lephritidae) in northeast Egypt

We estimated thermal developmental thresholds(7o)and degree-day(DD)constants for the immature stages of two tephritid pests,Bcictrocera zonata(Saunders)and Ceratitis capitata(Weidenmann).Males of both species were trapped in an Egyptian guava orchard during the fruiting seasons of 2016 and 2017 and trap catches were compared with peak flights predicted by the DD model based on local weather data.Ceratitis capitata had faster development than B.zonata at 20 and 25°C,but their overall developmental rate was similar at 30 and 35°C.The thermal threshold of development(7o)of B.zonata was higher than that of C.capitata,indicating greater sensitivity to cold.Although 35°C yielded the fastest development of both species,survival was higher at 30°C,with B.zonata experiencing a slight advantage,suggesting better tropical adaptation.Immature development of B.zonata and C.capitata was estimated to require 338 and 373 d,respectively,and 616 and 424 DD for a complete generation.Trap catches over both seasons showed good correspondence to peaks of fly activity predicted by the DD models;deviations from expectation ranged from 0 to 7 d for both fly species.Both species had four overlapping generations per season,with B.zonata abundance peaking in the first generation in both years,but only in 2016 for C.capitata.The models predict about eight and 12 generations per year in northeast Egypt for B.zonata and C.capitata,respectively.These models should be useful for timing pest control measures to coincide with periods of peak fly activity in fruit orchards.     

Composition and distribution of ground-dwelling beetles among oak fragments and surrounding pine plantations in a temperate forest of North China

In this study, we compared ground-dwelling beetle assemblages （Coleoptera） from a range of different oak fragments and surrounding conifer plantations to evaluate effects of forest size and surrounding matrix habitat in a temperate forest of north China. During 2000, beetles were sampled via pitfall traps within two large oak fragments （ca. 2.0-4.0 ha）, two small oak fragments （ca. 0.2-0.4 ha） and two surrounding matrices dom- inated by pine plantations （〉4 ha） in two sites of different aspects. Overall, no significantly negative effects from forest patch size and the surrounding matrix habitat were detected in total species number and abundance of ground-dwelling beetles. However, compared with small oak patches or pine plantations, more species were associated with an affinity for at least one large oak patch of the two aspects. Multivariate regression trees showed that the habitat type better determined the beetle assemblage structure than patch size and aspect, indicating a strong impact of the surrounding matrix. Linear mixed models indicated that species richness and abundance of all ground-dwelling beetles or beetle families showed different responses to the selected environmental variables. Our results suggest that more disturbed sites are significantly poorer in oak forest specialists, which are usually more abundant in large oak fragments and decrease in abundance or disappear in small fragments and surrounding matrix habitats. Thus, it is necessary to preserve a minimum size of forest patch to create conditions characteristic for forest interior, rather than the more difficult task of increasing habitat connectivity.     

Pink bollworm moth （Lepidoptera： Gelechiidae） catches in the Imperial Valley, California from 1989 to 2003

We examined the patterns of male pink bollworm （PBW）, Pectinophora gossypiella （Saunders）, moth catches in gossyplure-baited traps over a 15-year period from 1989 to 2003 in the Imperial Valley, California, USA. Monitoring was conducted during periods when different pink bollworm areawide control strategies were being used. Numbers of male pink bollworm moths caught in gossyplure-baited traps progressively decreased each year from 1990 to 1994 during short-season cotton production. High numbers of male moths caught in traps from 1995 to 1997 may have been related to moth migrations from the large cotton acreages grown in the Mexicali Valley bordering the Imperial Valley. Transgenic Bollgard （Bt） cotton was planted in 3% of the cotton area in 1996 and thereafter in 80%- 94% of the cotton area from 1997 to 2003. Pink bollworm moth trap catches were significantly lower from 1998 to 2003 than catches in 1995 to 1997, except for 1999. The trapping results suggested that Bt cotton had significant input on reduction of pink bollworm populations, confirming results of other investigators and providing additional documentation on the benefits of the Bt cotton culture.     

Mixed‐species aggregations in arthropods

This review offers the first synthesis of the research on mixed-species groupings of arthropods and highlights the behavioral and evolutionary questions raised by such behavior.Mixed-species groups are commonly found in mammals and birds.Such groups are also observed in a large range of arthropod taxa independent of their level of sociality. Several examples are presented to highlight the mechanisms underlying such groupings, particularly the evidence for phylogenetie proximity between members that promotes cross-species recognition.The advantages offered by such aggregates are described and discussed.These advantages can be attributed to the increase in group size and could be identical to those of nonmixed groupings,but competition-cooperation dynamics might also be involved,and such effects may differ between homo-and heterospecific groups.We discuss three extreme cases of interspecific recognition that are likely involved in mixed-species groups as vectors for cross-species aggregation:tolerance behavior between two social species,one-way mechanism in which one species is attractive to others and two-way mechanism of mutual attraction.As shown in this review,the study of mixed-species groups offers biologists an interesting way to explore the frontiers of cooperation-competition, including the process of sympatric speciation.