Interaction between ants and seeds of a nonmyrmecochorous neotropical tree, Cabralea canjerana (Meliaceae), in the Atlantic forest of southeast Brazil

On the forest floor of two Atlantic forest sites in southeast Brazil, we recorded 26 ant species (12 genera) interacting with the seeds of Cabralea canjerana (Meliaceae), a typical ornithochorous tree whose seeds are covered by a lipid-rich aril. The ants treat the arillate seeds in three different ways: (1) the large ponerine ants Pachycondyla striata and Odontomachus chelifer individually remove the seeds to their nests, (2) many species (Pheidole spp.) recruit workers to remove the aril on the spot, or (3) Solenopsis spp. recruit nestmates and cover the seeds with soil before removing the aril on the spot. The ants remove the aril exceptionally rapidly, and removal greatly facilitates seed germination. Seed predation by insects below fruiting trees is severe, and field experiments using vertebrate exclosures showed that rodents also prey heavily upon seeds found near parent trees. Ponerine ants actively remove seeds from this predation-prone zone. By removing bird-manipulated and naturally fallen seeds, ants can play a key role in the fate of medium-sized seeds like those of C. canjerana.     

Germination of Geonoma brevispatha (Arecaceae) in laboratory and its relation to the palm spatial distribution in a swamp forest

Geonoma brevispatha is a clonal palm species commonly found as tussocks in swamp and riparian forests in SE Brazil, occurring in the very transition between flooded pits/channels and dry mounds. Aiming to verify whether the germination responses could explain the spatial pattern of the palm tussocks in swamp forests, we investigated the germination in relation to the main environmental factors to which the seeds are subjected in their natural habitat. The seeds are recalcitrant since germination percentage is reduced with loss of moisture content. Germination did not differ on moist filter paper, semi-immersion (water up to half of the seed diameter) or complete immersion (water up to double of the seed diameter). Seeds did not germinate when stored in a closed bottle with water (that is, under low oxygen concentration), but remained viable for up to 8 weeks under this condition. The capacity to germinate in water with minimum oxygen availability may be considered ecologically advantageous in a swamp habitat. On the other hand, the capacity to germinate in moist filter paper indicates that, in natural conditions, the seed can germinate, provided there is a critical minimum of water availability. We concluded that the germination responses per se are not enough to explain the palm tussocks spatial pattern, but they are very well tuned with the conditions of the transitional zone between channels/pits (ever flooded micro-sites) and mounds (well-drained micro-sites), in which the species occurs in the swamp forest.     

科尔沁沙地家榆林的种子散布及幼苗更新

家榆是典型的风播植物,在科尔沁沙地可以形成单一优势种林地.通过对林缘和孤立树不同方向从树基部向外的有序取样与林下和林窗的随机取样调查,分析了家榆林下和林窗不同生境的种子沉降和幼苗分布特征、林缘和孤立树种子散布方向的差异性与规律性.结果表明,家榆种子密度在林下生境阴坡和阳坡明显大于丘顶和丘底,在林窗生境丘顶明显大于丘底.家榆向周围不同方向种子散布的距离和累积数量均有较大差异,其中林缘和孤立树均以当地多逆风频率的西南方向最近,累积数量也最少;孤立树以多顺风频率的东北方向最远,累积数量也最多.林缘和孤立树共6个方向断面从树基部向外单位面积种子数量频度均适合于韦伯分布和对数-正态分布(X2(a)＜0.500)密度函数,具有相同的种子散布格局.家榆幼苗密度在林下阴坡明显大于阳坡,林下和林窗均为丘顶明显大于丘底.林缘19 m内家榆幼苗呈连续分布.在科尔沁沙地,如果不加限制或人为扰动,家榆林不仅可以很好地进行自然更新,而且可以在适宜的沙地生境逐渐扩大其分布空间.     

Seed dispersal by red howling monkeys (Alouatta seniculus) in the tropical rain forest of French Guiana

A 2-year field study of the frugivorous diet of a howling monkey troop, in a tropical rain forest in French Guiana, shows that they disperse by endozoochory ≥95% of plant species from which they eat ripe fruit. Passage through the digestive tract of howlers does not significantly modify the germination success of most plant species samples. Their low digestion rate (X = 20 hr 40 min) is the ultimate cause of a bimodal defecation rhythm that results in the concentration of 60% of defecations being deposited under sleeping sites. The distance of seed dispersal can reach more than 550 m from parent trees,with a mean of 260 m. Although howling monkeys consume fruits differing in morphological characteristics, they are particularly able to disseminate seeds of species whose fruits have a hard and indehiscent external coat or large seeds or both. In French Guiana, they may be especially important dispersers of the Sapotaceae with fruits that simultaneously present both characteristics.     

Seed dispersal and seedling recruitment of trees at different successional stages in a temperate forest in northeastern China

Aims Spatial distribution of adult trees in a forest community is determined by patterns of both seed dispersal and seedling recruitment. The objectives of our study were to understand the processes of seed dispersal and seedling recruitment of dominant tree species in a temperate forest of northeastern China and to identify the factors constraining seed dispersal and seedling establishment at different stages of forest succession.Methods During three summer and autumn sessions between 2006 and 2008, altogether 113080 seeds from 22 different tree species were collected in three large field plots representing different forest types in the Changbai Mountain region of northeastern China. The spatial distribution of seed abundance was analyzed using a Syrjala test. Regeneration success of nine major tree species was assessed using variables defining 'limitations' in 'seeds' and 'seedling establishment'.Important findings We found that seed production fluctuated between years and varied greatly with forest types. Four tree species, Acer spp., Fraxinus mandshurica, Tilia amurensis and Betula spp., had the greatest seed production and the widest range of seed dispersal, whereas Quercus mongolica showed the most sustained seed production pattern. The spatial patterns of seed abundance differed significantly among forest types and years. The tree species investigated in this study differed in the degree of seed limitation, as well as in limitation of seedling establishment. There were both negative and positive correlations between seed density and seedling density, depending on site and parental tree density. Seeds of 16 tree species were found in the Populus davidiana–Betula platyphylla forest (PBF) plot, 11 in the conifer and broad-leaved mixed forest (CBF) plot but only 8 in the broad-leaved-Korean pine mixed forest (BKF) plot. The number of seed-contributing species was not only greater in the secondary forests (CBF and PBF plots) than in the primary forest (BKF plot) but was also more variable during the 3 years of assessment. Results from the correlations between seed density and seedling occurrence and that between parental tree density or seed weight and dispersal limitation confirm our intuitive expectations, i.e. heavy seeds had greater dispersal limitation but higher establishment success than light seeds.     

秦岭森林鼠类对华山松种子捕食及其扩散的影响

森林鼠类的种子贮藏行为对植物的扩散和自然更新有着非常重要的影响。通过塑料片标记法,2008和2009年的9月—11月分别在秦岭南坡的佛坪国家级自然保护区内调查了森林鼠类对华山松(Pinus armandii)种子的捕食和扩散,结果显示:森林鼠类对华山松种子有着非常大的捕食压力。在2008年,几乎所有的种子(96.4%)在第3天后就被全部取食,而在2009年,也有将近一半的种子(49.6%)在第3天后被取食。但与此同时,鼠类对华山松种子的扩散也起着非常重要的作用。尤其在2009年,第3天时鼠类最高分散贮藏了17.75%的种子,而且直到第19天后仍然有12.25%被贮藏的种子存活下来。华山松种子在两个年份间的扩散历程有很大差异。在2008年,几乎所有的种子都被鼠类取食,贮藏量非常小;而在2009年,种子被贮藏的比例显著的增加。这个结果可能与种子大小年现象有着十分紧密的联系。2008年是华山松种子的小年,产量非常低。鼠类为了满足其日常的能量需求,只能大量的取食有限的种子,而减少其贮藏量。而2009年是华山松种子的大年,产量非常高。鼠类在满足其日常能量需求的同时,还有大量剩余的种子供其贮藏。     

荒漠孑遗植物裸果木种子时空扩散特性

裸果木(Gymnocarpos przewalskii)是亚洲中部荒漠区少有的第三纪孑遗物种,由于气候变化及人为干扰,其自然种群分布范围不断缩小。种子扩散作为植物生活史过程中的重要阶段,不仅对物种生存及其多样性至关重要,还影响物种分布范围和局部丰度。2015年和2016年分别在新疆哈密地区,采用布设种子收集器的方法,对其自然种群种子扩散的时空动态进行了定点连续观测。结果表明:该物种于当年6月上旬开始扩散,2015年略早于2016年。每年种子扩散持续时间约两个月,扩散趋势为单峰曲线,且呈集中大量扩散的模式,扩散高峰期与当年初次月降水高峰期吻合;在顺风的正南和东南方向上,种子扩散密度大且距离远;种子扩散主要集中在母株冠幅下,随着距母株距离的增加,种子扩散密度减少,二者间存在极显著的负相关性(P0.01),由于裸果木枝条繁多,对风力强度起到了一定的阻碍作用,可能是造成种子集中扩散在母株下的原因。裸果木种子扩散受外界环境(降水、风向)和自身因素等方面的影响,当种子在大量降水前完成扩散,将有利于种子在适宜的微生境萌发,是对多风、干旱的恶劣生境的一种长期适应。     

Distyly and sequential pollinators of Psychotria nuda (Rubiaceae) in the Atlantic rain forest, Brazil

Reciprocal herkogamy is known to promote intermorph-pollination in distylous species, which are generally self- and intramorph-incompatible. Legitimate crossing rates are also influenced by pollinator foraging strategy, which determines most of the pollen flow in natural populations. This study reports on the floral morphology, compatibility relations and pollination biology of Psychotria nuda (Cham. and Schltdl.) Wawra in the Atlantic rain forest, southeastern Brazil, based on floral measurements, hand-pollination experiments and focal observation of floral visitors. It was found that P. nuda does not present an exactly reciprocal herkogamy, however, this morphological trait in P. nuda is as good as in most of Rubiaceae. Reproductive experiments showed compatibility relations similar to those frequently observed in distylous species. The hummingbirds Ramphodon naevius and females of Thalurania glaucopis were the main pollinators of P. nuda, presenting the traplining foraging strategy, which seems to maximize intermorph crosses in P. nuda flowers. These hummingbirds pollinated P. nuda flowers sequentially throughout the flowering period.     

Seed banks on Attalea phalerata (Arecaceae) stems in the Pantanal wetland, Brazil

Background and Aims

Seeds can accumulate in the soil or elsewhere, such as on the stems of palms when these are covered by persistent sheaths. These sheaths could act as a safe site for some species. Here, we studied whether persistent sheaths of the palm Attalea phalerata (Arecaceae) are available sites for seed accumulation in the Pantanal wetland of Brazil. We also investigated whether the composition, richness and diversity of species of seeds in the persistent sheaths are determined by habitat (riparian forest and forest patches) and/or season (wet and dry).

Methods

All accumulated material was collected from ten persistent sheaths along the stems of 64 A. phalerata individuals (16 per habitat and 16 per season). The material was then individually inspected under a stereomicroscope to record seed species and number.

Key Results

Of the 640 sheaths sampled, 65 % contained seeds (n = 3468). This seed bank included 75 species belonging to 12 families, and was primarily composed of small, endozoochoric seeds, with a few abundant species (Cecropia pachystachya and Ficus pertusa). Moraceae was the richest family (four species) and Urticaceae the most abundant (1594 seeds). Stems of A. phalerata in the riparian forest had 1·8 times more seeds and 1·3 times more species than those in forest patches. In the wet season we sampled 4·1 times more seeds and 2·2 more species on palm stems than in the dry season. Richness did not differ between habitats, but was higher in the wet season. Abundance was higher in forest patches and in the wet season.

Conclusions

Attalea phalerata stems contain a rich seed bank, comparable to soil seed banks of tropical forests. As most of these seeds are not adapted to grow in flooding conditions, palm stems might be regarded as safe sites for seeds (and seedlings) to escape from the seasonal flooding of the Pantanal.     

Bird diversity and abundance in forest fragments and Eucalyptus plantations around an Atlantic forest reserve, Brazil

Little of Brazil's remaining Atlantic forest is protected, so it is important to assess how well the region's wildlife can persist in areas/habitats outside reserves. We studied bird diversity and abundance during 546 point counts in the Sooretama/Linhares reserve, 200 point counts in 31 forest fragments (10–150 h), and 50 point counts in <30-year-old Eucalyptus plantations, within 7 km of the reserve. Only eight bird species were recorded in Eucalyptus, and this impoverishment, as compared to some Eucalyptus plantations elsewhere in Brazil may be a result of intensive clearance of understory vegetation. Species diversity in forest fragments was significantly lower than in the reserve. Twelve, mostly non-forest or edge species, were significantly commoner in the fragments, but nineteen species were frequent in the reserve but rare or absent in forest fragments. These included two Pyrrhura parakeets, a Brotogeris parakeet, a trogon Trogon, a jacamar Galbula, woodpeckers Piculus and Campephilus, Myrmotherula antwrens, and Hemithraupus and Tachyphonus tanagers. Bird species richness at points in forest fragments did not decline with fragment size, distance from the reserve, or forest quality. However, forest in fragments was more heavily degraded than forest within the reserve and poor forest quality may be the cause of declines in some species. Whilst protection of forest within reserves is a priority, management of forest fragments may aid conservation of some threatened species.     

Germination and water dispersal of seeds from a threatened plant species Penthorum chinense

To conserve a threatened plant species (Penthorum chinense Pursh) in Japan, seed germination responses to pretreatment (imbibition and/or chilled), temperature and light, and seed dispersal by water were examined. The seeds collected from abandoned paddy fields in a warm temperate region, central Japan, germinated in light (14 h photoperiod; light 22°C, dark 21°C) after a moist-chilled treatment. After this pretreatment, the seeds germinated well at 10–25°C (optimum temperature 15°C), but did not germinate in darkness even at the optimum temperature. Most of the seeds floated on distilled water, but 20–60% of the seeds that were collected from several populations sank in distilled water, indicating dimorphism in seed dispersal by water. The floating and sunken seeds did not show significant differences in weight and germination rate within a population. The addition of a surface-active agent in distilled water submerged the seeds, indicating that the buoyancy of the seeds is attributable to an oil coating on the seed surface that enhances the interfacial tension on the seeds. Three times the number of seeds sank in river water collected from a rural area than in distilled water. A greater number of seeds also sank in water that had increasing concentrations of linear alkylbenzenesulfonate, which is a major component of synthetic detergents. This suggests that the water dispersal of this species is suppressed by surface-active agents, including detergents, in river water.     

Feeding behavior of Geoffroy's marmoset (Callithrix geoffroyi) in an Atlantic forest fragment of South-eastern Brazil

We report on the diet and feeding behaviour of a group of Geoffroy's marmosets (Callithrix geoffroyi) in an Atlantic forest fragment in south-eastern Brazil, studied during the period February 1993 to Januaray 1994. Major food categories were gums (68.6%) fruits (15%), and small animal prey (invertebrates 14.6% and vertebrates 0.8%). Dietary changes were observed between the wet and dry seasons, although they were not statistically significant. Insects and gums were consumed throughout the year but fruits were more prevalent in the diet in the wet season. Plant species exploited for their gums includedInga stipularis, followed byAcacia paniculata, Paulinia carpopodia, andBauhinia angulosa. Chemical analysis of the gum of the four species most used all presented high values for carbohydrates and crude proteins. Fruits of an unidentified species of Myrtaceae (sp. 2) were consumed the most. Animal prey consisted mainly of insects, arachnids, snails, and in three cases, lizards and frogs, with orthopterans being the most prevalent insect prey. This study demonstrates thatC. geoffroyi efficiently exploits resources typically available in secondary and disturbed forest habitat. The main threat to the species is forest destruction, degradation, and fragmentation, but the management of small forest fragments may be an effective corservation strategy.     

Seed predation and dispersal of glabrous filbert (Corylus Heterophylla) and pilose filbert (Corylus Mandshurica) by small mammals in a temperate forest, northeast China

We investigated the seed dispersal of glabrous filbert (Corylus heterophylla) and pilose filbert (Corylus mandshurica), two large-seeded shrub species in a temperate forest, northeast China, September 2006. Small mammals such as Apodemus speciosus, Clethrlonomys rufocanus, and Eutamias sibiricus, were regarded as the main dispersal agents. More seeds were harvested by small mammals in pilose filbert (98%) than in glabrous filbert (87.5%) till our last survey. Seed removal rates differed between the two species. Fewer seeds of glabrous filbert (17.5%) were eaten in situ than pilose filbert (57.5%). More seeds of glabrous filbert were removed (70%), stay intact after removal (25.5%), eaten after removal (16%) than pilose filbert. However, more seeds were cached after removal in pilose filbert than in glabrous filbert (10.5 and 4%, respectively). Fewer tagged seeds of pilose filberts (14%) were missed than glabrous filberts (24.5%). About 8 and 12 primary caches were found in glabrous filbert and pilose filbert seeds respectively, indicating scatter hoarding. All of the removed seeds were distributed within 10 m of seed stations for both filberts. The average dispersal distances for glabrous filbert did not differ from pilose filbert. Only a small proportion of the caches remained till our last survey (2 and 1%, respectively). Based on the results, we found a difference in dispersal patterns of glabrous filbert and pilose filbert seeds. Evidences showed that glabrous filberts might be a less preferred seed species for small seed-eating mammals compared with pilose filbert, probably due to its harder and thicker husk and low seed profitability.     

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.     

Phenology and floral visitors of two sympatric Heliconia species in the Brazilian Atlantic forest

The main goal of the present study was to test if two sympatric species of Heliconia, Heliconia spathocircinata and Heliconia laneana var. flava, differ in their reproductive seasons and guilds of flower visitors. Twenty-four sampling sessions were conducted monthly between February 2001 and January 2003. Individuals of H. spathocircinata and of H. laneana var. flava were tagged within a transect of 4000×4 m. Reproductive phenophases (flowering, unripe, and ripe fruits) were recorded, and circular statistics were used to test for the regularity and frequency of phenophases. Flower visitors were observed during two flowering periods for each species. Both species had well-defined and synchronous reproductive periods, with a small overlap, suggesting a sequential flowering model. Biotic and abiotic factors seem to affect phenophases of both species. However, herbarium data suggest that the flowering period in H. spathocircinata varies less than in H. laneana, despite its wider geographic distribution. The hummingbird Phaethornis idaliae was the main floral visitor of both Heliconia species studied. H. laneana was also legitimately visited by another hummingbird species, Glaucis hirsuta, and by Lepidoptera. Some Lepidoptera, particularly the bee Trigona spinipes, were illegitimate visitors (‘nectar robbers’). We suggest that the flower of H. spathocircinata allowed a wider array of visitors, because it is bigger.     

Slow death of Atlantic forest trees in cocoa agroforestry in southeastern Brazil

Cocoa (Theobroma cacao) is cultivated in the states of Bahia and Espírito Santo in eastern Brazil under the so-called cabruca system, where the understorey of native Atlantic forest is cleared and the canopy is thinned out to provide adequate shading for the cocoa trees. Apart from its economic and social role, the cabruca system is said to be important for the conservation of Atlantic forest biodiversity. In this paper we studied tree species richness and forest structure of cabrucas to examine the demographic health of these forests and discuss their long-term survival. Data were collected in 20 farms located alongside a 30km track of the northern margin of the Rio Doce, in northern Espírito Santo. All trees 5cm DBH were identified and their diameter was measured in 80 plots (600m²), totalling 4.8ha of sampled area. Recorded trees were also allocated to four different regeneration phases (pioneers, early secondary, late secondary and climax). The inventory resulted in 507 trees belonging to 105 species in 39 families. This species richness is much lower than in less disturbed forests located in the region. Pioneers and early secondary species dominate the cabruca forest in terms of number of species (56.2%), density (71.0%) and basal area (72.3%). The distribution of diameter frequency showed an imbalance in tree regeneration. Most trees in the range of 5–30cm DBH were pioneers (40.7%), or early secondary species (32.6%), while late secondary and climax trees were less frequent (10.2 and 16.5% of the sampled trees, respectively). The dominance of species of early regeneration phases was also observed for trees >30cm DBH (69.0% of pioneers or early secondary and 31.0% of late secondary or climax species). The results indicated that the cabruca forests are not only less diverse and less dense than secondary or primary forests of the region, but also, and more importantly, their natural succession and gap dynamics are being severely impaired. As a consequence, cabrucas present a structure where tree species of late successional phases are becoming increasingly rare while pioneers and early secondary species are becoming dominant. If current management practices of thinning and clearing of native trees are not improved, the long-term survival of these forests is questionable and their role in maintaining biodiversity in the long run is limited.     

Description of the karyotype of Rhagomys rufescens Thomas, 1886 (Rodentia, Sigmodontinae) from Southern Brazil Atlantic forest

Rhagomys rufescens (Rodentia: Sigmodontinae) is an endemic species of the Atlantic forest from Southern and Southeastern Brazil. Some authors consider Rhagomys as part of the tribe Thomasomyini; but its phylogenetic relationships remain unclear. Chromosomal studies on eight specimens of Rhagomys rufescens revealed a diploid number of 2n = 36 and a number of autosome arms FN = 50. GTG, CBG and Ag-NOR banding and CMA(3) /DAPI staining were performed on metaphase chromosomes. Eight biarmed and nine acrocentric pairs were found in the karyotype of this species. The X and Y chromosomes were both acrocentric. Most of the autosomes and the sex chromosomes showed positive C-bands in the pericentromeric region. The X chromosome showed an additional heterochromatic block in the proximal region of the long arm. Nucleolus organizer regions (NORs) were located in the pericentromeric region of three biarmed autosomes (pairs 4, 6 and 8) and in the telomeric region of the short arm of three acrocentrics (pairs 10, 12 and 17). CMA (3) /DAPI staining produced fluorescent signals in many autosomes, especially in pairs 4, 6, and 8. This study presents cytogenetic data of Rhagomys rufescens for the first time.     

Estimation of the retention times and distances of seed dispersed by two monkey species, Alouatta seniculus and Lagothrix lagotricha, in a Colombian forest

Isolated-bout method to estimate the retention times and dispersal distances was applied to the seed dispersal by red howler monkeys (Alouatta seniculus) and Humboldts woolly monkeys (Lagothrix lagotricha) in a lowland tropical forest at La Macarena, on the border of the Macarena and Tinigua National Parks, the Department of Meta, Colombia. Continuous observations were made on the feeding and ranging behavior of well-habituated troops of howler monkeys and woolly monkeys as well as continuous collection of monkeys feces. We selected out the isolated-bout as a feeding bout on the specific species that was only once recorded within 48 h before the seeds of that species appeared in the feces of monkeys. In that case, the seeds were strongly suggested to come from that isolated bout. Then retention times, route seed dispersal distances and direct seed dispersal distances were estimated. Howler monkeys, which are regarded as generalist herbivores, showed longer retention times and dispersal distances along monkeys route than did woolly monkeys, which are specialist frugivores. However, the direct distances that seeds were carried from the mother tree were not significantly greater for howler monkeys than for woolly monkeys. This shows that both retention time and movement patterns by the monkeys, especially the total ranging area, influence the direct distance that seeds are carried from the mother tree.