TABLE 1 - uploaded by Daniel Janzen
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The distribution of nymph and adult Dysdercus fasciatus along the lines of seeds depicted in Fig. 3, at approximately half-hour intervals during one morn- ing
Source publication
When a seed of the large tree Sterculia apetala falls to the ground beneath the parent tree in a Costa Rican tropical deciduous forest, it is typically found and fed upon within a few minutes by cotton-stainer bugs (Dysdercus fasciatus). The rate of seed discovery by the bugs is highest where the seed fall is most intense and tapers off to zero bet...
Contexts in source publication
Context 1
... at 6: 37 AM, "milk seeds" (full-sized but not yet black) were removed from the pods and placed on the ground with a clean spoon at approx- imately I-m intervals along four lines radiating from the large tree (Fig. 3). The number of bugs feeding on each seed was recorded at various intervals until 10: 15 AM (Table 1). Both the average number of bugs on a seed and the rate at which seeds are found should be directly correlated with bug density in the seed's immediate vicinity. ...
Context 2
... differences are readily explained by differences in the overall micro- habitat and the extent of the seed shadow. Line 1 extends upwind from the tree, and its peak bug den- sity is between 5 and 11 m out from the trunk ( Table 1 ). The vertical projection .of the crown margin is about 10 m from the trunk on this line (Fig. 3). ...
Context 3
... vertical projection .of the crown margin is about 10 m from the trunk on this line (Fig. 3). Line 3 (Table 1) extends downwind and the peak Minutes exposedb meters ------------ from trunk" bug density is 18-23 m from the trunk; the crown margin on this line is about 11 m from the trunk (- Fig. 3). This asymmetry of bug density along lines in the forest (Fig. IB sion of downwind distortion of the seed shadow by seeds being blown as much as 5-10 m off the vertical as they fall. ...
Context 4
... asymmetry of bug density along lines in the forest (Fig. IB sion of downwind distortion of the seed shadow by seeds being blown as much as 5-10 m off the vertical as they fall. The point where no more bugs are found on line 4 (11-14 m from the trunk, see Table 1) coincides almost exactly with the line of shadow cast on the open grass field (Fig. Ie) at 8:00 AM; the steeper drop-off in bug density at 7 m from the trunk is approximately 2 m past the edge of the forest. A seed landing anywhere in the open pasture probably has no chance of surviving, owing to desiccation of either seed or seedling during the next 4 months of the dry season. ...
Context 5
... seed landing anywhere in the open pasture probably has no chance of surviving, owing to desiccation of either seed or seedling during the next 4 months of the dry season. The river serves as a barrier to move- ment away from the tree, which probably accounts for the very high density of bugs along line 2 ( Table 1). ...
Context 6
... all three forest lines (1, 2, and 3), all seeds had been found by bugs within about 3.5 hr after placing the seeds on the ground (Table 1). However, 33 of 76 seeds in these lines had been located within 25 min after the first seed was positioned (dawn was approximately 6:37 AM). ...
Citations
... Dependiendo del clima y el tipo de suelo en el que se desarrolle, la fructificación se presenta cuando el árbol tiene entre 20 y 30 años o entre 15 y 25 m de altura. En la mayor parte de América tropical, la producción de semillas es anual y en época seca (febrero a marzo) (Janzen, 1972;Dvorak, 1998). De acuerdo con Crawley (2000), la fructificación de S. apetala es alterna, con altas producciones intercaladas con la obtención de pocos frutos y semillas (Fajardo, 2013). ...
Si bien los procesos de reforestación en Colombia se han realizado principalmente utilizando especies exóticas o introducidas, la alta diversidad de especies nativas podría convertirlas en una alternativa socioeconómica para los productores, además de contribuir a la adaptación y mitigación de la variabilidad y el cambio climático, así como a la recuperación del paisaje natural, la cultura y las tradiciones de los territorios. Sin embargo, la información es limitada o no hay suficientes datos disponibles sobre el comportamiento silvicultural de las especies, su adaptación y su crecimiento en plantaciones comerciales o en asocio bajo sistemas agroforestales y silvopastoriles para promover el desarrollo forestal en el país. Esta cartilla, dirigida a productores, academia, técnicos y profesionales del sector, incluye resultados obtenidos en los centros de investigación Nataima (Tolima), Motilonia (Cesar) y La Libertad (Meta) de agrosavia para las especies forestales caracolí (Anacardium excelsum), iguá (Albizia guachapele), ocobo o roble (Tabebuia rosea), camajón (Sterculia apetala), guayacán (Bulnesia arborea), carreto (Aspidosperma olyneuron), machaco (Simarouba amara) y cañafístola (Cassia moschata).
... In the case between deer and red cotton bugs, the deer are a confirmed seed disperser (Khadka & Lamichhane, 2020;B. Awasthi, unpublished data) and bugs are seed predators (Dinerstein, 2013;Janzen, 1972) and possibly secondary seed dispersers (B. Awasthi, unpublished data), indicating potentially important tri-trophic interactions under fruiting Trewia trees; determining the overall outcomes for seedling recruitment from these interactions will require detailed study. ...
Fruiting trees provide important fruit and seed resources for various animal species, but rarely are they considered to be rich sources of insects as well. During a study of seed dispersal of Trewia nudiflora (Euphorbiaceae) using camera traps in Nepal, we observed four tropical deer species (Axis axis, Muntiacus vaginalis, Rusa unicolor, Axis porcinus) foraging for insects, rather than fruits under the trees. These herbivorous deer are proven seed dispersers of Trewia, but 8%–38% of video captures (across each species) were of insectivory, rather than frugivory. The deer chased and consumed red cotton bugs (Dysdercus sp. family Pyrrhocoridae), which were seed predators that hoarded Trewia seeds. It is likely that other unidentified insect species were also consumed. Tropical deer species are considered to be fully herbivorous, so our observations extend their known diets and possibly indicate a seasonal requirement for protein. These findings also highlight tri‐trophic interactions among deer, insects, and fruits that could have important implications for seedling recruitment if seed predators are being consumed by seed dispersers (in addition to fruit consumption).
... In the case between deer and red cotton bugs, the deer are a confirmed seed disperser (Khadka & Lamichhane, 2020;B. Awasthi, unpublished data) and bugs are seed predators (Dinerstein, 2013;Janzen, 1972) and possibly secondary seed dispersers (B. Awasthi, unpublished data), indicating potentially important tri-trophic interactions under fruiting Trewia trees; determining the overall outcomes for seedling recruitment from these interactions will require detailed study. ...
... La ardilla Sciurus variegatoides Ogilby, 1839 es una de las nueve especies de la familia Sciuridae presentes en América Central (Thorington & Hoffmann, 2005), de la cual se dispone de relativa poca información, limitándose una descripción de sus subespecies (Harris, 1937;McPherson, 1971), su alimentación (Glanz, 1984;Monge & Hilje, 2006;Henn, McCoy, & Vaughan, 2014) y algunos datos de estudios no enfocados a la especie o bien de observaciones aisladas (Boucher, 1981;Fleming, 1970;Janzen, 1971Janzen, , 1972Janzen, , 1982aJanzen, , 1982bRose et al., 2003;Schemske, 1980). Otros aspectos de su historia natural han sido resumidos por Best (1995). ...
Introducción: la ardilla Sciurus variegatoides es una de las especies más abundantes de ardilla en América Central, sin embargo, poco se sabe sobre su reproducción. Objetivo: determinar el ciclo reproductivo de S. variegatoides en un área agrícola de Costa Rica. Métodos: mensualmente (diciembre de 1986 a enero de 1988) recolecté 10 animales en Hacienda Curú, Paquera, Costa Rica. Usé la presencia de escroto, el tamaño de los testículos y la longitud de los cuernos uterinos para evaluar la madurez. El ciclo reproductivo se basó en la preñez, la lactancia, el cortejo, la construcción de nidos y la proporción de subadultos. Resultados: recogí un total de 135 ardillas, la proporción de sexos fue de 1,7 machos por cada hembra y el 22% fueron subadultos (ambos sexos). Capturé las hembras embarazadas de diciembre a junio y representaron el 42% de las hembras adultas. Febrero y abril estuvieron marcados por cortejo y un aumento en la construcción de nidos. Recolecté las hembras lactantes de junio a setiembre, cuando capturé más subadultos. Conclusión: no hubo evidencia de actividad reproductiva en octubre y noviembre.
... Another bias that is obvious from the studies listed in Table 1 is the almost exclusive focus on chewing insects attacking either seeds or seedlings. The only exception is an influential paper by Janzen in which he reports on the effects of an external-feeding sap-sucking bug on seeds of Sterculia apetala (Janzen, 1972a). Seed bugs (Lygaeidae and related families) are renowned as potentially important seed predators in the tropics (Slater, 1972 and references therein). ...
... Janzen's study on seed mortality by seed-sucking bugs on Sterculia apetala also illustrates another potentially important point. Since the externally sap-sucking bug studied by Janzen may transmit a pathogenic fungus to the host tree (Janzen, 1972a), the ultimate cause of seed mortality might appear to be caused by a seed pathogen rather than by an insect. This illustrates the need to consider the synergy between insects and pathogens. ...
... Negative interactions with conspecific neighbors might be caused by shared pests and/or by competition for limiting resources (Lebrija-Trejos et al. 2014). A major mechanism, known as the Janzen-Connell hypothesis, proposed that the maintenance of diversity is facilitated by a conspecific negative density dependence (CNDD), whereby the proximity to adults of the same species reduces seedling survival rates through attacks by hostspecific adversaries (Janzen 1970(Janzen , 1972. Furthermore, distance dependence, a basic part of the Janzen-Connell hypothesis, has been extensively verified in tropical forests. ...
Key message
The effects of distance dependence, negative density dependence (NDD), phylogenetic density dependence, and habitat filtering were integrated to provide additional evidence in temperate forest tree seedling survival. The main focus of this study was to explore how population density and habitat filtering regulate NDD. An approach involving four classes of population density and three classes of soil moisture was tested, including the effect of habitat variables to more accurately evaluate the underlying ecological processes affecting the density dependence of seedlings.
Context
NDD is an important mechanism for the maintenance of species diversity across multiple life stages, particularly during seedling recruitment. By regulating specific population structures to maintain species diversity, the effects of density dependence and distance dependence are sometimes difficult to distinguish. Nevertheless, the contribution of NDD to community assembly, relative to other processes such as habitat filtering, remains a subject of debate. Recently, it has been reported that seedling survivals are also negatively correlated with phylogenetic relatedness between neighbors and focal individuals. This effect is known as phylogenetic negative density dependence (PNDD). However, another opposite effect known as phylogenetic positive density dependence (PPDD) has also been reported to exist.
Aims
The objectives of this study are to examine the following: (i) how population density affects negative density dependence (NDD); (ii) how habitat filtering regulates the NDD; (iii) whether more evidence can be found for PNDD or PPDD and why; and (iv) whether the intensity of negative density dependence is affected by the distance between parent trees and seedlings.
Methods
The study was conducted in a 20-ha primary mixed broad-leaved Korean pine forest in Changbai Mountain of China. We used generalized linear mixed models to analyze how the seedling survival of 23 woody plant species relates to neighborhoods and habitat variables. Four models were established with and without habitat variables, and two of the four models were used to test how different population densities of focal seedlings and different gradients of habitat variable regulated negative density dependence.
Results
The following results were obtained: (1) the strongest conspecific negative density dependence (CNDD) was found within a radius of 15 m; (2) seedling survival were most strongly impacted by the density of conspecific seedling and adult neighbors in habitats with relatively low soil moisture; (3) the effect of seedling-seedling CNDD was especially significant, when densities ranged from 20 to 40 seedlings/4 m², and (4) there were some evidences of phylogenetic positive density dependence (PPDD), and the effect of seedling-seedling PPDD was increasing with an increase in soil moisture.
Conclusion
Our results demonstrate that conspecific negative density dependence played an important role in seedling survival, which is closely related to habitat filtering and population density. However, we found some evidences of phylogenetic positive density dependence. We suggest that future studies of neighborhood density dependence should increase awareness of evolutionary relationships.
... Panamá fruits, S. apetala, are a dietary staple of capuchins at RBLB; they comprise 8% of the diet of most groups in the early dry season [37]. The fruits are empanada-shaped, and the fatty, protein rich seeds within are protected by a hardened outer husk and stinging hairs [38]. Instead of waiting for fruits to dehisce, capuchins will open closed fruits and work around their structural defences, thus reducing competition with other organisms. ...
... Panamá processing techniques are also observed to vary between groups at RBLB and other field sites in the area [29], suggesting they are socially learned traditions. Wild capuchins without prior exposure to panamá fruits cannot initially open them [38], suggesting that personal experience and/or social influence are important. ...
The type and variety of learning strategies used by individuals to acquire behaviours in the wild are poorly understood, despite the presence of behavioural traditions in diverse taxa. Social learning strategies such as conformity can be broadly adaptive, but may also retard the spread of adaptive innovations. Strategies like pay-off-biased learning, by contrast, are effective at diffusing new behaviour but may perform poorly when adaptive behaviour is common. We present a field experiment in a wild primate, Cebus capucinus, that introduced a novel food item and documented the innovation and diffusion of successful extraction techniques. We develop a multilevel, Bayesian statistical analysis that allows us to quantify individual-level evidence for different social and individual learning strategies. We find that pay-off-biased and age-biased social learning are primarily responsible for the diffusion of new techniques. We find no evidence of conformity; instead rare techniques receive slightly increased attention. We also find substantial and important variation in individual learning strategies that is patterned by age, with younger individuals being more influenced by both social information and their own individual experience. The aggregate cultural dynamics in turn depend upon the variation in learning strategies and the age structure of the wild population.
... The decrease under Olea in seed predation rates with distance from the parent crown coincided with a decrease in the capture rate of Praomys jacksoni. Such distance-responsive patterns of seed predation and fungal attacks have previously been reported [32,19,33,34,35]. ...
Careful scrutiny of data collected during the forest inventory in the 1960s on the undergrowth reveals absence of seedlings of Olea welwitschii. This study sought to determine why Olea welwitschii does not regenerate inside the forest and to examine the roles of predispersal and post-dispersal drupes and seed predation intensities as precipitators of lack of regeneration. Seed/drupe predation experiments were conducted at two levels. The first level examined pre-dispersal seed and drupe predation. Rectangular seed/drupe traps made out of meshed fabric with a collecting surface of 0.25 m2were randomly placed to cover all the four quadrants under the canopy of five randomly selected Olea fruiting trees. The second level examined post-dispersal predation by sampling seeds and drupes under the crown of each of the randomly selected fruiting trees by dividing it into four quadrants. Within each quadrant, five 1m2 quadrats were established on the ground in a random fashion to cover at least 10-30 per cent of the total canopy area. Frequency- and distance- dependent seed/drupe predation were examined using 30 (l m2) quadrats with equal numbers of seeds and drupes and inspected every 12 hours for one month to determine differences in seed and drupe predation rates. Effects of density and distance were tested by setting up 50 m long transects with the base of the fruiting trees as the starting point. Two transects per tree in two different directions, north/south and east/west at five fruiting trees were established. Along each transect, eleven sampling stations were established at a five metre interval. A trapping grid was established under the crown of five fruiting Olea adults and away from the crown to determine differences in small mammal predator density. Results of predispersal drupes predation was derived from the pooled sample of all drupes collected. A total of 1386 drupes were collected. Of these, three (3) per cent had insect holes. A closer examination of size and weight of the drupes that were attacked revealed that smaller drupes (70%) were attacked more than larger ones (30%). Overall, there were more small drupes falling on the forest floor (89 per cent) than large ones (11 per cent). Drupe and seed density was a decreasing function of distance from the parent trees ad distance from the parent trees had a significant effect on drupes and seed predation rates. Regardless of density, seeds were removed at higher rates under the parent crowns, while drupes were ignored by the predators. One species of rodents, Praomys jacksoni was trapped. The majority of the captures were under fruiting Olea adults (3.71 animals per trapping night) rather than farther away from the adult trees (0.61 animals per trapping night; Z=8.724, p<0.01). A total of 18,000 seeds were examined for pathogen attacks and only 10 per cent of the intact seeds showed sign of insect/rodent attack. Drupes density greatly influenced fungal infection rates (ᵡ2=55.867, p<0.001). Results clearly suggest that density is not an important factor in the predation of Olea drupes and drupes. The failure to find greater predation rates for drupes in large clumps suggest that either large clumps are no easier to find than small clumps for predators or these predators remove all the drupes they find regardless of clump size. Predation risk of drupes and seed appears to be influenced by patchiness in the activity patterns of drupes eaters.
... A recent meta-analysis of 108 plant species, suggests overall support for JC effects in both tropical and temperate regions (Comita et al. 2014). Thus, 'escape in space' from Janzen-Connell effects via dispersal is a well-explored theme in habitat generalists (Janzen 1972;Beattie and Lyons 1975;Hay and Fuller 1981). Another way to avoid these effects is by regulating the numbers of fruits overtime and the timing of fruit production. ...
Our understanding of processes underlying plant recruitment emerges from species and habitats that are widely distributed
at regional and global scales. However, the applicability of dispersal-recruitment models and the role of dispersal limitation
versus microsite limitation have not been examined for specialised habitats. In patchy, freshwater Myristica swamp forests (Western Ghats, India), we examine the roles of primary seed dispersal, secondary seed removal and microsite
suitability for the establishment of a swamp specialist tree, Myristica fatua. We estimated primary seed shadows, performed secondary removal experiments and enumerated recruits in swamp sites. Steady-state
fruiting was observed with the extended production (> 7 months) of small numbers of fruits. Frugivores dropped most of the
large and heavy seeds under parent crowns, while a few seeds were transported over short distances by hornbills. Seed placement
experiments indicated that removal, germination and establishment were similar within swamp microsites, while seeds failed
to survive in matrix habitats surrounding the swamp. Crabs, which were major secondary removers of M. fatua, did not alter the initial seed dispersal patterns substantially, which led to the retention of seeds within the swamp. Distribution
of saplings and adults from previous seasons also suggest that dispersal-recruitment dynamics in the swamp specialist M. fatua did not strictly follow predictions of Janzen-Connell model while abiotic effects were significant. Large seeds, steady-state
fruiting and small crop sizes may be significant selective forces facilitating escape from density and distance-dependent
effects in space and time in specialist plant species such as M. fatua.
... H. Karst. (Janzen, 1972). The latter species is African, but has arrived in the New World (Janzen, 1972). ...
... (Janzen, 1972). The latter species is African, but has arrived in the New World (Janzen, 1972). In Nigeria, Dysdercus superstitiosus (Fabricius, 1775), feeds on Sterculia sp. between January and March, but then moves to cotton (Gossypium sp., Malvales: Malvaceae) (Golding, 1928). ...
A recently described species of Dysdercus, named Dysdercus stehliki Schaefer, 2013 (Hemiptera: Heteroptera: Pyrrhocoridae), found in Viçosa, Minas Gerais State, Brazil, feeds upon the seeds of fallen fruits of Sterculia chicha A. St. Hil. (Malvales: Sterculiaceae). The biology and immature stages’ descriptions of D. stehliki were assessed in two environments: laboratory and field. Individuals of the five nymphal instars were collected in March, 2011, in Viçosa, Minas Gerais State, Brazil on fruits of S. chicha. The presence of eggs, nymphs, and adults inside of the fruits was observed daily. Developmental time for eggs, nymphs, and adults were 9, 45 and 30 days, respectively in the field. The five nymphal instars were described. First instar: overall color dark red, paler ventrally except for head. Second instar: overall color darker red (darker than first instar). Third instar: overall color slightly darker than 2nd instar. Fourth instar: slightly darker and browner than 3rd instar. Fifth instar: overall color brown red.
Key words: Brazil, Malvales, Morphology, Neotropical region, Nymph
