Seed dispersal and predation by Yakushima macaques, Macaca fuscata yakui, in a warm temperate forest of Yakushima Island, southern Japan

The relationships between fruit morphology and the foraging behavior of the Yakushima macaque, Macaca fuscata yakui were studied during a 9-month field study and series of laboratory experiments on Yakushima Island, southern Japan. These relationships may affect seed germination traits through seed dispersal. The macaques foraging behavior was observed in order to obtain data concerning the treatment of pulp and seeds. Seeds in feces and spat seeds were collected and analyzed. A linear discriminant analysis of the data led to the following results: (i) an increase in the relative flesh volume of a fruit was one of the potential factors which increased the probability of seed dispersal by the macaques; and (ii) seed size was an important parameter in relation to the type of seed dispersal (by defecation or spitting out). The germination test was conducted in a laboratory, then the germination rates and delays of dispersed seeds were compared with those of seeds collected directly from trees. The germination of dispersed seeds of Ficus thunbergii, Eurya japonica, and Vaccinium bracteatum, was significantly enhanced by passage through the macaques gut. The enhanced germination behavior was not seen in larger seeds, such as those of Psychotria serpens, Myrsine seguinii, Diospyros morrisiana, and Neolitsea sericea. The germination enhancement in small-seeded plants could be due to a sorting effect from the passage through the gut, which selects seeds with a narrower range of germination traits.     

Morphological and molecular variation in Mitchella undulata,with special reference to the systematic treatment of the dwarf form from Yakushima

Morphological and molecular variation in Mitchella undulata Siebold et Zucc. was examined to evaluate the genetic basis for recognizing the dwarf variety, M. undulata var. minor Masamune. Considerable variation in leaf size in M. undulata, but no obvious morphological discontinuities, were found between the normal and dwarf varieties. Instead, a weak cline running from the Pacific Ocean to the Sea of Japan was found. Anatomical observations of leaf blades revealed that the large variation in leaf size can be attributed to variation in the number of leaf cells and not to differences in cell size. A molecular analysis based on sequences of rDNA internal transcribed spacer regions indicated that there were two major genotypes in M. undulata with minor variation in haplotypes resulting from additional substitutions or putative recombination. The dwarf form from Yakushima was neither genetically uniform nor apparently differentiated from other populations. From these results, we conclude that the dwarf form of M. undulata should be treated at the rank of forma.     

高榕雌花期传粉榕小蜂和欺骗性小蜂的繁殖特点

榕树及其专一性传粉榕小蜂组成了动植物界最为经典的协同进化关系,传粉榕小蜂演化出欺骗性是非常罕见的。在雌雄同株的高榕隐头果内,共存着一种传粉榕小蜂Eupristina altissima和一种欺骗性的小蜂Eupristina sp.,两种小蜂在雌花期进入隐头果内繁殖,但有不同的繁殖特点。对比研究了两种小蜂从成虫羽化到产卵和传粉这个阶段的雌蜂个体大小、孕卵量及繁殖差异,结果表明:羽化期两种雌蜂的平均个体小,经飞行小个体的雌蜂易死亡,大个体雌蜂到达接受树,但通过苞片通道,一些个体较大的传粉榕小蜂被夹死导致进入果腔的雌蜂相对小,而欺骗性小蜂易通过苞片以至进入果腔的雌蜂个体较大。两种未产卵雌蜂均表现为个体大者孕卵量较多,但两种雌蜂的平均孕卵量没有差异。即使有充足雌花资源产卵,两种雌蜂均未产完所有卵,产卵后两种雌蜂卵巢中的卵量均显著减少,遗留下的卵量两种小蜂间没有差异。传粉榕小蜂只有部分个体传完所携带花粉,并表现为传粉越成功的雌蜂,产卵越多。存在种内竞争时,两种小蜂的产卵量均减少,传粉榕小蜂的传粉效率也降低。在种间竞争背景下,欺骗性小蜂产卵更成功,传粉榕小蜂的产卵和传粉量均受到极大抑制。研究结果说明雌花期隐头果内传粉榕小蜂只适量利用雌花资源产卵繁殖后代,更有效地传粉繁殖榕树种子,这可能是维持榕-蜂互惠系统稳定共存的重要机制之一;欺骗者稳定存在需降低与传粉者的直接竞争,而欺骗者和传粉者分散在不同果内,甚至是不同的树上繁殖是理想的繁殖策略。     

Molecular variation of Spiranthes sinensis (Orchidaceae) in Japan, with special reference to systematic treatment of seasonally differentiated groups and a dwarf form, f. gracilis, from Yakushima Island

Molecular variations of Spiranthes sinensis Ames var. australis (R.Br.) H. Hara et Kitam. ex Kitam. in Japan were examined to evaluate the validity of the seasonally differentiated groups and a dwarf form of the species, which is endemic to Yakushima Island, Japan. Sequence differences in the plastid trnL-F locus clearly distinguished Japanese S. sinensis var. australis from S. sinensis var. sinensis collected from Ryukyu. In contrast, the trnL-F sequence of S. sinensis var. australis from Sabah, Malaysia, clearly differed from that of Japanese S. sinensis var. australis, suggesting genetic heterogeneity of Spiranthes sinensis var. australis in Asia. Moreover, a molecular analysis based on the sequences of nuclear ITS1 regions indicated that there are two major groups of S. sinensis var. australis in Japan, with a geographic distribution boundary on Kyushu Island. However, the trnL-F and ITS1 sequences did not support the genetic differentiation of the seasonally differentiated groups or the dwarf form from the other Japanese individuals. Based on these molecular data, the systematic treatment of physiological and morphological variations in the Japanese population of S. sinensis. var. australis is discussed.     

Independent evolution of the same set of characters in fig flies (Lissocephala,Drosophilidae)

Summary Comparison of species of African fig flies (Lissocephala, Drosophilidae) shows that an unusual phenotype has evolved independently when a particular environment prevails. Each time the adaptation is observed, associated morphological and behavioural characters also appear. Such convergence suggests that selection operates on sets of predetermined morphogenetic pathways.     

Measuring the trophic ecology of ants using stable isotopes

Ants are prominent components of most terrestrial arthropod food webs, yet due to their highly variable diet, the role ants play in arthropod communities can be difficult to resolve. Stable isotope analysis is a promising method for determining the dietary history of an organism, and has the potential to advance our understanding of the food web ecology of social insects. However, some unique characteristics of eusocial organisms can complicate the application of this technique to the study of their trophic ecology. Using stable isotopes of N and C, we investigated levels of intraspecific variation both within and among colonies. We also examined the effect of a common preservation technique on δ¹⁵N and δ¹³C values. We discuss the implications of our results on experimental design and sampling methods for studies using stable isotopes to investigate the trophic ecology of social insects. Received 4 February 2005; revised 23 June 2005; accepted 4 July 2005.     

Seed dispersal by Japanese marten <Emphasis Type="Italic">Martes melampus</Emphasis> in the subalpine shrubland of northern Japan

The functions of carnivorous mammals as seed dispersers were studied during a snow-free period of 2 years in the subalpine shrubland of northern Japan. Mammal appearances, which were recorded using three automatic cameras, were dominated by Japanese marten, Martes melampus (Wagner), followed by three carnivores (ermine, red fox, and raccoon dog) and two other mammals (field mouse and Japanese hare). Fecal analysis revealed that the martens dispersed seeds of 11 species (eight woody and three herbaceous plants), which included a vine species that is an inhabitant of lower elevation sites. Fruit weight and size, and flesh weight and volume of the fleshy-fruited species foraged by the martens were significantly greater than those that were not foraged. These facts indicate that the marten plays a key role as a relatively long-distance seed disperser for major component species with large and flesh-rich fruits in the subalpine shrubland.     

Chemosensory attraction of fig wasps to substances produced by receptive figs

In the mutualism between figs (Ficus spp., Moraceae) and their species-specific fig wasp pollinators (Hymenoptera: Agaonidae), location of a receptive host tree by the adult insect is a critical step. The adult female wasp lives only a few days, and must usually fly to a different tree than her natal tree to locate receptive figs. Trees in receptive phase often occur at very low densities. Reproductive success of both fig and wasp depends on trasmission of a very strong signal by the plant. Some evidence exists for the role of olfaction in location of receptive hosts by fig wasps, but very little work has been done on the chemical ecology of host location and host specificity. Here the first experimental evidence is presented for long-distance olfactory attraction of wasps by volatile substances produced by receptive figs, and for short-distance or contact chemostimulation by host volatiles that elicit entry of the wasp into the fig. In studies usingFicus carica L., pentane extracts of receptive-phase figs attract the pollinatorBlastophaga psenes L. from distances of at least 5 m in the field. Short-distance chemostimulation was demonstrated in laboratory bioassays. Pentane extracts of receptive figs, when painted onto the ostiole of non-receptive figs, elicit entry of pollinator wasps. Figs emit volatile compounds attractive to pollinating wasps only during the period of receptivity; pentane extracts of non-receptive figs are not attractive. A simple reliable procedure is described to compare the attractivity of different types of extracts (total, internal, and external extracts) and of different fractions, in the first step towards identifying attractant substances.     

Dispersed central-place foraging in the polydomous odorous house ant, Tapinoma sessile as revealed by a protein marker

The odorous house ant, Tapinoma sessile, is a native ant species common throughout North America. In urban areas, this ant is classified a pest species and exhibits several attributes characteristic of invasive “tramp” ants (sensu Passera, 1994). These include: extreme polygyny, colony reproduction by budding, reduced internest aggression, generalist diet, and polydomy. Here we explore the organization of foraging and the pathways of food distribution in polydomous colonies of T. sessile in the laboratory and field using a novel marking technique (rabbit IgG protein) and enzyme linked immunosorbent assay (ELISA). Laboratory assays revealed patterns of food allocation from foragers to other castes and developmental stages. Foragers distributed the IgG- labelled sucrose to the majority of workers within 24 h, and workers retained significantly more sucrose than either queens or larvae. Approximately 50% of queens tested positive for the IgG marker and some queens received significantly more sucrose than others, indicating a possible reproductive dominance hierarchy. Larvae received little sucrose demonstrating their minor reliance on carbohydrates. The results of field experiments showed that odorous house ants are dispersed central-place foragers whereby ants from individual nests exhibit high foraging site fidelity, travel along well-established trails, and forage on a local scale. Dispersed central-place foraging most likely allows the odorous house ant to more efficiently secure both clumped and dispersed food sources and possibly increases its competitive ability. As a result, colonies become numerically large and ecologically dominant. The results of our study contribute to our understanding of the social behavior and colony organization in T. sessile. In addition, they provide a framework for designing more effective ant control programs based on liquid baits. Received 13 December 2005; revised 28 February 2006; accepted 3 March 2006.     

Low genetic diversity and biased distribution of mitochondrial DNA haplotypes in the Japanese macaque (Macaca fuscata yakui) on Yakushima Island

The Japanese macaques (Macaca fuscata yakui) on Yakushima Island are an endemic subspecies and are closely related to the population of Kyushu, one of the main islands of Japan. Using feces collected throughout Yakushima Island, we examined mitochondrial DNA (mtDNA) to investigate the phylogeography of Japanese macaques. Six haplotypes were observed for a 203-bp fragment of the mtDNA control region. The nucleotide diversity () was low (0.0021). The genetic divergence within the Yakushima population was lower (0.009) than that among four haplotypes of the Kyushu population (0.015), calculated using Kimuras two-parameter method. The mismatch distribution analysis of the six haplotypes of the Yakushima population suggested that the Yakushima population had experienced a sudden expansion in population size, which could be related to the bottleneck effect. The geographic distribution of the mtDNA haplotypes was not uniform. One haplotype was distributed widely, whereas the other five haplotypes were distributed only in the lowlands. The low genetic diversity and biased distribution are discussed in relation to an environmental crash caused by ancient volcanic activity near this island, which is postulated to have happened about 7,300 years ago, and the delayed recovery of highland vegetation.     

中国部分地区实验猕猴巴尔通体感染状况及其遗传特征

【目的】五日热巴尔通体(Bartonella quintana)由体虱在人群中传播,可引起多种人类疾病包括战壕热。为进一步搜集猕猴是五日热巴尔通体自然宿主的证据,本研究调查了国内4个地区实验用猕猴五日热巴尔通体的感染状况,对菌株遗传特征进行了分析。【方法】采集猕猴全血和血清样品各550份,用于菌株分离、核酸和血清IgG抗体检测。应用6个管家基因扩增及测序方法进行菌株鉴定、系统发育及核苷酸多态性分析;应用随机扩增多态性DNA标记(Random amplified polymorphic DNA,RAPD)技术分析不同宿主来源菌株RAPD指纹图谱差异;应用间接免疫荧光法(Indirect immunofluorescence assay,IFA)检测血清中抗五日热巴尔通体IgG抗体水平。【结果】从550只猕猴中分离到8株五日热巴尔通体菌株,带菌率为1.5%;直接PCR检测550份全血核酸的总感染率为8.2%。普通猕猴血清阳性率为19.0%,感染水平明显高于食蟹猕猴(5.6%)。五日热巴尔通体与汉赛巴尔通体RAPD指纹图谱的带型完全不同,猴源和人源五日热巴尔通体菌株Fuller带型基本一致。不同宿主来源菌株核苷酸多态性分析显示,猴源菌株之间差异小,其与人源菌株差异较大。【结论】中国猕猴五日热巴尔通体感染水平较高,普通猕猴自然感染率及抗体水平明显高于食蟹猕猴,猴源与人源菌株的基因型有明显差异。     

Correlated evolution of fig size and color supports the dispersal syndromes hypothesis

The influence of seed dispersers on the evolution of fruit traits remains controversial, largely because most studies have failed to account for phylogeny and or have focused on conservative taxonomic levels. Under the hypothesis that fruit traits have evolved in response to different sets of selective pressures by disparate types of seed dispersers (the dispersal syndromes hypothesis), we test for two dispersal syndromes, defined as groups of fruit traits that appear together more often than expected by chance. (1) Bird syndrome fruits are brightly colored and small, because birds have acute color vision, and commonly swallow fruits whole. (2) Mammal syndrome fruits are dull-colored and larger on average than bird syndrome fruits, because mammals do not rely heavily on visual cues for finding fruits, and can eat fruits piecemeal. If, instead, phylogenetic inertia determines the co-occurrence of fruit size and color, we will observe that specific combinations of size and color evolved in a small number of ancestral species. We performed a comparative analysis of fruit traits for 64 species of Ficus (Moraceae), based on a phylogeny we constructed using nuclear ribosomal DNA. Using a concentrated changes test and assuming fruit color is an independent variable, we found that small-sized fruits evolve on branches with red and purple figs, as predicted by the dispersal syndromes hypothesis. When using diameter as the independent variable, results vary with the combination of algorithms used, which is discussed in detail. A likelihood ratio test confirms the pattern found with the concentrated changes test using color as the independent variable. These results support the dispersal syndromes hypothesis.     

Cheek-pouch dispersal of seeds by Japanese monkeys (Macaca fuscata yakui) on Yakushima Island, Japan

Seed dispersal by Japanese monkeys (Macaca fuscata yakui) via cheek-pouch was studied in a warm temperate evergreen forest on Yakushima Island. Plant list was compiled based on a study during 1986–1995, of which troops of monkeys have been habituated without artificial feeding. We followed the well-habituated monkeys in 1993 and 1994 to observe the feeding behavior and their treatments of fruits and seeds, and collected seeds dispersed by monkeys to record the distance carried from the mother trees. We checked the difference of germination ratio between seeds dispersed via cheek-pouch and seeds taken from mother trees by sowing experiments. Seeds and acorns of 22 species were observed to be dispersed via cheek-pouch of monkeys. Among them, three species with acorns were never dispersed via feces, and 15 species with drupes were seldom dispersed via feces. Plant species of which seeds are dispersed only via cheek-pouch had larger seeds than those of dispersed both via cheek-pouch and via feces, and typically had only one or two seeds in a fruit. As for one of cheek-pouch dispersal species,Persea thunbergii, the mean distance when seeds were carried from the mother trees via cheek-pouch was 19.7 m, and the maximum distance was as long as 105 m although more than 80% of seeds were dispersed within 30 m from mother trees. And 82% of seeds dispersed via cheek-pouch germinated. The easy separation of seeds from other parts of the fruit seems to facilitate cheek-pouch dispersal more than dispersal via feces. Cheek-pouch dispersal by monkeys has possibly enhanced the natural selection for larger seeds which bring forth larger seedlings with high shade-tolerance. In conclusion, cheek-pouch dispersal by monkeys is quite an important mode for trees in the mature stand in a warm temperate evergreen forest on Yakushima Island.     

Population density and group composition of Japanese sika deer (<Emphasis Type="Italic">Cervus nippon yakushimae</Emphasis>) in an evergreen broad-leaved forest in Yakushima,southern Japan

The population density of Japanese sika deer (Cervus nippon yakushimae Kuroda and Okada) in an evergreen broad-leaved forest in Yakushima, southern Japan, was surveyed over 4years from 1998 to 2001. Two approximately 50ha study sites, Hanyama and Kawahara, were established with a total of 4km of census trails at each site. The estimated densities of sika deer at the two sites were 43–70 deerkm^–2 at Hanyama and 63–78 deerkm^–2 at Kawahara, although these values might be underestimates. The adult sex ratio (number of adult males:number of adult females) ranged from 0.6 to 1.0 at Hanyama, and from 0.4 to 0.9 at Kawahara. Mean group size was 1.9 deer (male group, 1.5 deer; female group, 1.6 deer; mixed group, 3.6 deer). The population density of sika deer was relatively high compared to other sites in Japan, with the exception of very small (<10km²) islands. Possible explanations for this naturally high density of sika deer in an evergreen broad-leaved forest in Yakushima are discussed.     

Morphological variation in leaf shape in <Emphasis Type="Italic">Ainsliaea apiculata</Emphasis> with special reference to the endemic characters of populations on Yakushima Island,Japan

We analyzed leaf shape variations in Ainsliaea apiculata Sch. Bip. to evaluate the uniqueness of morphological characters in populations on Yakushima Island, Kagoshima Prefecture, Japan. Leaf size and shape from populations on Yakushima Island (n = 300) were compared with those from populations in other areas of Japan (n = 300). A considerable amount of variation occurred in leaf size in A. apiculata populations both on Yakushima Island and elsewhere, but clear discontinuities in leaf size were not detected. Some variants previously thought to be endemic to Yakushima Island, i.e., A. apiculata var. acerifolia and A. apiculata var. rotundifolia, were also found in other locations in Japan. Moreover, these leaf types were found to be continuous with the typical leaf shape of A. apiculata var. apiculata via various intermediate types, suggesting the need for future revision of these taxa. Based on these results, we reevaluated the uniqueness of the Yakushima populations of A. apiculata in terms of leaf variation. The uniqueness of the Yakushima populations was defined by a more diverse leaf shape than found in populations from other areas.     

Optimal central-place foraging by beavers: Tree-size selection in relation to defensive chemicals of quaking aspen

Summary At a newly occupied pond, beavers preferentially felled aspen smaller than 7.5 cm in diameter and selected against larger size classes. After one year of cutting, 10% of the aspen had been cut and 14% of the living aspen exhibited the juvenile growth form. A phenolic compound which may act as a deterrent to beavers was found in low concentrations in aspen bark, and there was no significant regression of relative concentration of this compound on tree diameter. At a pond which had been intermittently occupied by beavers for over 20 years, beavers selected against aspen smaller than 4.5 cm in diameter, and selected in favor of aspen larger than 19.5 cm in diameter. After more than 28 years of cutting at this site, 51% of the aspen had been cut and 49% of the living aspen were juvenileform. The phenolic compound was found in significantly higher concentrations in aspen bark than at the newly occupied site, and there was a significant negative regression of relative concentration on tree diameter. The results of this study show that responses to browsing by trees place constraints on the predictive value of standard energy-based optimal foraging models, and limitations on the use of such models. Future models should attempt to account for inducible responses of plants to damage and increases in concentrations of secondary metabolites through time.     

Fruits foraging patterns and seed dispersal effect of frugivorous birds on Hippophae rhamnoides sinensis

Behaviors of 18 species of birds eating fruits of Hippophae rhamnoides spp. sinensis were observed from September 2003 to March 2004. Their foraging patterns were found to be very different and can be divided into five classes: (1) direct swallowing the fruits on crown of the shrubs and sometimes regurgitating seeds soon after; (2) carrying the fruits to their perching sites and swallowing; (3) pecking the fruits from the shrubs to the ground, eating pulp and seeds but leaving pericarp; (4) pecking through the pericarp, eating pulp and leaving pericarp and seeds; (5) pecking through the pericarp on the top of fruits, and only eating seeds. These foraging patterns have different effects on seed dispersal of H. rhamnoides spp. sinensis. The germination experiment of three groups of seeds (seeds from feces, dry fruits and extracted seeds from dry fruits) was carried out. Although ingestion processes of birds had some adverse effects on the seed germination of H. rhamnoides spp. sinensis, the seeds from feces still have a relatively higher germination ratio. H. rhamnoides spp. sinensis provides food to a variety of frugivorous birds, and the birds disperse its seeds. Thus, a mutually beneficial relationship between the bird and the seed is formed. __________ Translated from Chinese Journal of Ecology, 2005, 24(6): 635–638 [译自: 生态学杂志, 2005, 24(6): 635–638]     

Critical population size for fig/wasp mutualism in a seasonal environment: effect and evolution of the duration of female receptivity

Fig trees and their pollinating wasps form ca. 750 pairs of obligate mutualists, mainly in the tropics. Survival of each partner depends on that of its associated species. Here, we examine the possible outcome of such an interaction at small population size. Using phenology data collected on Ficus natalensis in Gabon, we modelled wasp survival and the reproductive success of the trees according to the duration of receptivity of the tree, the amplitude of flowering seasonality, and the size of the fig tree population. Since the duration of receptivity is critical in these population level models, we also determined the influence of individual selection on this phenological trait. The models give three major results: (1) The minimum fig population size required to sustain a wasp population increases with the amplitude of seasonality, and decreases with increasing duration of receptivity; (2) tree population reproductive success is higher when the duration of receptivity is longer and when the population is large, but (3) individual selection toward a long duration of receptivity is weak or absent.     

视野受阻对东方田鼠觅食行为的影响

植食性小型哺乳动物的觅食行为是对特定生境的适应性产物。食物斑块周边植被对动物视野遮挡是否通过作用于其觅食活动中的警觉而影响摄入率。采用新鲜白三叶叶片构建东方田鼠密集均质食物斑块,以牛皮纸模拟食物斑块周边植被遮挡田鼠视野,测定其在食物斑块上的觅食行为序列过程及行为参数,检验食物斑块周边植被高度对东方田鼠摄入率的影响。结果发现,个体在不同程度视野受阻条件下食物摄入率无显著差异。分析觅食行为参数动态发现,在不同视野受阻条件下,个体能通过调整各采食回合内警觉行为动作的发生频次和持续时间,维持觅食回合内总的觅食中断时间的稳定,进而保证进食时间的稳定。东方田鼠在不同程度的视野遮挡条件下均能通过行为变异和优化使摄入率保持稳定。结果亦充分说明,东方田鼠在警觉强度上的变化不能反映觅食中断所带来的食物收益减损的代价,但觅食活动中各警觉动作的持续时间的变异却能够明确指示个体摄入率的动态变化,因此,以觅食活动中警觉引起的觅食中断时间代价为线索,检验其对摄入率的影响,是评价植食性小型哺乳动物在不同生境觅食适应性策略的有效的方法。