Strangler Figs Research Articles

The restless plant

The restless plant

Effects of ingestion by neotropical bats on germination parameters of native free-standing and strangler figs (Ficus sp., Moraceae)

Fruit-eating animals can influence the germination success of seeds through transportation and handling. We experimentally tested the contribution of ingestion by the common fruit-eating bat, Artibeus jamaicensis (Phyllostomidae, Chiroptera), to the percentage and rate of seed germination of figs (Ficus, Moraceae), which are considered keystone species for many frugivores. We collected fruits from three species of native free-standing figs (subgenus Pharmacosycea: F. insipida, F. maxima and F. yoponensis) and three species of native strangler figs (subgenus Urostigma: F. nymphiifolia, F. obtusifolia and F. popenoei) on Barro Colorado Island, Panama. The germination success of seeds removed from fruit pulp either manually or by ingestion was very high (>92%), while seeds that were not removed from fruit pulp were destroyed by fast-growing fungi within a few days. The dynamics of seed germination were not influenced by ingestion, but differed between the two subgenera of figs. In free-standing figs, germination started significantly earlier (5.3 +/- 0.7 days) than in strangler figs (8.6 +/- 1.4 days). Furthermore, strangler seeds were covered with a sticky coating and their seedlings developed cotyledons faster than fine roots, in contrast to free-standing figs that showed the opposite pattern. Our results demonstrate that the germination of fig seeds is positively influenced by passage through the gut of A. jamaicensis. Furthermore, free-standing and strangler figs revealed differences in germination parameters that might be adaptive with respect to the suitability of microsites such as tree fall gaps or host trees for establishment.

Behavior of tamarins, tanagers and manakins foraging in a strangler fig (Ficus sp.) in Suriname, South America: implications for seed dispersal

The behavior of foragers can directly affect the dispersal of seeds. Strangler figs are keystone resources throughout the tropics and are important resources for both primates and birds. We examined the foraging behavior of golden-handed tamarins and four bird species in a strangler fig to see how these behaviors might affect the dispersal of fig seeds. Tamarins removed fruit at a faster rate than did any of the bird species examined. Additionally, tamarins tended to swallow figs whole whereas birds tended to drop figs once they were processed. Tamarins visiting fig trees ingest large quantities of fig seeds that may be deposited throughout the forest. Birds on the other hand tended to slowly process fruits near the fig tree and drop processed fruit containing large quantities of seeds. Future studies need to be conducted to ascertain differences in post dispersal seed fate.

Quality of rooting environments and patterns of root colonization by arbuscular mycorrhizal fungi in strangler figs in a Mexican palmetto woodland

Arbuscular mycorrhizal colonization in strangler figs, spore richness, and abundance of arbuscular mycorrhizal fungi were quantified in epiphytic and ground-rooted trees in a Sabal palmetto woodland that had marked heterogeneity in rooting environments for hemiepiphytic plants. An inoculation experiment was performed to assess whether low spore density could limit mycorrhizal colonization. There was no significant difference in mycorrhizal colonization among Ficus species, but epiphytic plants in nutrient-rich rooting environments had less mycorrhizal colonization than ground-rooted plants in low-nutrient soils. However, richness and abundance of spores was low, and to some extent, this limited the mycorrhizal colonization of strangler figs. Nevertheless, our results suggest intraindividual adjusting levels of root colonization in strangler figs in accordance with mineral availability. Such responses could maximize the cost-benefit balance of arbuscular mycorrhizal interactions throughout the development of strangler figs from epiphytic young plants to ground-rooted trees.

Hurricanes and the Urban Forest: II. Effects on Tropical and Subtropical Tree Species

In 1998 when Hurricane Georges (177 km/h) crossed over the entire island of Puerto Rico, and in 2004 when Hurricanes Jeanne (193 km/h) and Charley (233 km/h) struck south Florida, U.S., we measured the impacts of these hurricanes on the urban forest composed of tropical and subtropical species. In addition, we also used previous published data for Hurricane Andrew for some analyses. The percent urban forest loss ranged from 13% for Georges to 16% for Jeanne to 18% for Charley. In Hurricanes Jeanne and Charley, palms survived significantly better than all other trees. Some of the best surviving species in Florida’s hurricanes were gumbo limbo (Bursera simarouba), sea grape (Coccoloba uvifera), strangler fig (Ficus aurea), live oak (Quercus virginiana), laurel oak (Quercus laurifolia), and baldcypress (Taxodium distichum). Of the species measured in Puerto Rico, the species with the highest survival and least branch damage were Santa Maria (Calophyllum calaba), Caribbean pine (Pinus caribaea), schefflera (Schefflera actinophylla), and West Indian mahogany (Swietenia mahogani). Losing leaves during these hurricanes had no relationship with how well trees survived. In Hurricanes Jeanne, Charley, and Georges, 3%, 4%, and 11%, respectively, of the trees that fell damaged property. Native tree species survived better than exotic species in Hurricanes Jeanne and Charley but not in Hurricane Georges. Trees growing in groups had greater survival and less branch loss in Hurricane Jeanne than those growing individually. Wood density was not related to survival or branch loss for tree species in Hurricanes Jeanne, Charley, Georges, or Andrew. Two other measurements of wood strength, modulus of elasticity and modulus of rupture, were related to survival and branch loss in Jeanne but not Charley. Tree species with dense crowns had greater survival and less branch loss than moderate- or open-crowned species. Tree species with decurrent growth form survived better than excurrent trees in Hurricane Jeanne with no difference in Charley. Trees with the most rooting space (>7 m2) had the lowest branch loss and the greatest survival in Hurricane Georges. A reanalysis of seven dicot species and their survival in Hurricane Andrew showed that survival for pruned trees was 73% compared with 47% for unpruned trees. A survey of 85 arborists, scientists, and urban foresters ranked species for their wind resistance. Using our results from hurricanes and incorporating results from the survey and the scientific literature, we have developed lists of relative wind resistance for tropical and subtropical tree species. These lists are presented with the caveat that no tree is completely windproof and that other factors such as soil conditions, wind intensity, cultural practices, and tree health and age also contribute to wind firmness.

Adaptations of strangler figs to life in the rainforest canopy.

Figs are rainforest keystone species. Non-strangler figs establish on the forest floor; strangler figs establish epiphytically, followed by a dramatic transition from epiphyte to free-standing tree that kills its hosts. Free-standing figs display vigorous growth and resource demand suggesting that epiphytic strangler figs require special adaptations to deal with resource limitations imposed by the epiphytic environment. We studied epiphytic and free-standing strangler figs, and non-strangler figs in tropical rainforest and in cultivation, as well as strangler figs in controlled conditions. We investigated whether the transition from epiphyte to free-standing tree is characterised by morphological and physiological plasticity. Epiphyte substrate had higher levels of plant-available ammonium and phosphate, and similar levels of nitrate compared with rainforest soil, suggesting that N and P are initially not limiting resources. A relationship was found between taxonomic groups and plant N physiology; strangler figs, all members of subgenus Urostigma, had mostly low foliar nitrate assimilation rates whereas non-strangler figs, in subgenera Pharmacocycea, Sycidium, Sycomorus or Synoecia, had moderate to high rates. Nitrate is an energetically expensive N source, and low nitrate use may be an adaptation of strangler figs for conserving energy during epiphytic growth. Interestingly, significant amounts of nitrate were stored in fleshy taproot tubers of epiphytic stranglers. Supporting the concept of plasticity, leaves of epiphytic Ficus benjamina L. had lower N and C content per unit leaf area, lower stomatal density and 80% greater specific leaf area than leaves of conspecific free-standing trees. Similarly, glasshouse-grown stranglers strongly increased biomass allocation to roots under water limitation. Epiphytic and free-standing F. benjamina had similar average foliar δ13C, but epiphytes had more extreme values; this indicates that both groups of plants use the C3 pathway of CO2 fixation but that water availability is highly variable for epiphytes. We hypothesise that epiphytic figs use fleshy stem tubers to avoid water stress, and that nitrate acts as an osmotic compound in tubers. We conclude that strangler figs are a unique experimental system for studying the transition from rainforest epiphyte to tree, and the genetic and environmental triggers involved.

Host associations of the strangler fig Ficus watkinsiana in a subtropical Queensland rain forest

Abstract The distribution of epiphytic organisms is limited by the availability of, and dispersal to suitable hosts. We examined the distribution of a hemi‐epiphytic strangler fig, Ficus watkinsiana (Moraceae) in Cooloola National Park (Queensland, Australia), in order to determine whether this species exhibits a preference for certain host species and why. We assessed host bark roughness and flakiness, fruit type, and size to explain the observed distribution of F. watkinsiana. We surveyed over 1900 potential host trees of the 30 most common forest canopy species and found that host size measured by diameter at breast height accounted for most variation in fig prevalence (Binary Logistic Regression log‐likelihood = −588.178, G = 314.494, d.f. = 1, P < 0.005). After controlling for host size, F. watkinsiana prevalence still differed significantly between host species (χ2 = 54.612, d.f. = 24, P < 0.005), a difference that was only partly explained by variation in the bark roughness of host trunks. These results suggest that variation in the rate at which tree species host strangler figs are primarily related to individual tree size – figs may simply be more likely to colonize and thrive upon host species that grow larger.

Fruit-frugivore interactions in a moist evergreen forest of Khao Yai National Park in Thailand

Seed dispersal by animals plays a crucial role in the tropics. Fruit-bearing plants serve not only as nutritional sources for frugivores, but also as seed sources for forest regeneration and as important foci for the re-establishment of other plant species by attracting seed-dispersing frugivores to their vicinity. However, opportunities for investigating the interactions between a diverse fruit flora and disperser fauna are rapidly disappearing in Southeast Asia. We observed the behaviors of 28 species of frugivorous visitors to 15 fruit-bearing plant species in a moist evergreen forest in Khao Yai National Park, Thailand, to determine their potential quality as seed dispersers. Behavioral observations included the frequency and duration of visits by each forager and their fruit-handling techniques. The highest numbers of frugivores were recorded at strangler figs, confirming their role as an important resource for frugivores at Khao Yai. Mammals and non-passerine birds spent significantly more time at food plants than did passerine birds. Our study provides a preliminary inventory of plant-frugivore interactions that is comparable to other study sites in Southeast Asia. Since fruit-frugivore interactions may differ among the forests, these kinds of studies need to be replicated at faunally intact forests, as well as depleted forests, in Southeast Asia.

Temporal Variation in the Relative Abundance of Fruit Bats (Megachiroptera: Pteropodidae) in Relation to the Availability of Food in a Lowland Malaysian Rain Forest1

The aims of this study were to investigate the diet and relative abundance of fruit bats in a lowland Malaysian rain forest and to test the hypothesis that the local assemblage structure of fruit bats varies significantly over time in relation to the availability of food. In total, 352 fruit bats of eight species were captured during 72,306 m2 mist-net hours of sampling between February 1996 and September 1999. Three species of fruit bats (Balionycteris maculata, Chironax melanocephalus, and Cynopterus brachyotis) that fed on a wide range of “steady state” and “big bang” food resources were captured continuously throughout the study period, with no significant variation in capture rates over time. In contrast, five species that fed exclusively or almost exclusively on “big bang” food resources were sampled intermittently, with significant temporal variation in the capture rates of two species (Cynopterus horsfieldi and Megaerops ecaudatus). Significant variation in the capture rates of the remaining three species (Dyacopterus spadiceus, Eonycteris spelaea, and Rousettus amplexicaudatus) could not be detected due to small sample sizes. Since ephemeral “big bang” food resources were only sporadically available within the study area and were associated with large canopy trees and strangler figs, these results suggest that food abundance, or the availability of specific food items, may be important factors limiting local fruit bat species diversity in old-growth Paleotropical rain forest. Thus, only three fruit bat species were locally resident within the forest throughout the study period. Therefore, further studies on the ranging behavior and habitat requirements of Malaysian fruit bats are required to assess the adequacy of existing reserves and protected areas.

Development of forest structure on cleared rainforest land in eastern Australia under different styles of reforestation

Rainforests in eastern Australia have been extensively cleared over the past two centuries. In recent decades, there have been increasing efforts to reforest some of these cleared lands, using a variety of methods, to meet a range of economic and environmental objectives. However, the extent to which the various styles of reforestation restore structure, composition and ecological function to cleared land is not presently understood. In this study, we develop and apply a method for quantifying the structural attributes of reforestation sites in tropical and subtropical Australia. The types of reforestation studied were plantation monocultures, mixed-species cabinet timber plots, diverse restoration plantings and unmanaged regrowth. Two age classes of reforestation were examined: ‘young’ (5–22 years), incorporating sites from all categories, and ‘old’ (30–70 years), in which only monoculture plantations and regrowth were represented. A total of 104 sites were surveyed including reference sites in intact rainforest and pasture. Intact rainforest was characterised by a suite of complex structural features including abundant special life forms (vines, epiphytes, hemi-epiphytes and strangler figs), a dense stand of trees in a range of size classes, a closed canopy, a shrubby understorey and a well-developed ground layer of leaf litter and woody debris. These features were lost on conversion to pasture. While all types of reforestation returned some elements of structural complexity to cleared land, young plantation monocultures, cabinet timber plots and young regrowth had a relatively simple structure. These sites typically had a low density of woody stems, a relatively open canopy and grassy ground cover, and lacked large trees, coarse woody debris and most special life forms. Restoration plantings and old regrowth were more complex, with a high density of woody stems, a relatively closed canopy and shrubby understorey. Old monoculture plantations in the tropics had acquired many of the structural attributes of intact forest, however this was not the case in the subtropics, where plantations were subject to more intensive management. The marked differences in structural complexity between sites suggest that the different types of reforestation practiced in eastern Australia are likely to vary considerably in their value as habitat for rainforest biota.

Nutritional Values of 14 Fig Species and Bat Feeding Preferences in Panama1

ABSTRACTFigs are a critical resource for many tropical frugivores, yet they often are referred to as low quality fruits. To determine their nutritional value, both as a group and for individual species, we analyzed 14 fig species from Barro Colorado Island (BCI), Panama, for fiber, tannins, lipids, protein, carbohydrates, amino acids, and minerals. Seeds and pulp were analyzed separately. Fig fruit pulp consisted of about one‐third digestible components, mostly carbohydrates with some lipids and proteins. Tannin, lignin, and water‐soluble carbohydrates showed considerable variation among species, as did fruit size. Figs contained high amounts of amino acids, such as leucine, lysine, valine, and arginine, and minerals, such as potassium, calcium, magnesium, sodium, and phosphorus. One species, Ficus insipida, contained the highest concentrations of almost all amino acids, many minerals, and protein. Small figs had as much nutritional value per gram as large figs. Free‐standing figs had higher percentages of protein, complex carbohydrates, and ash than strangler figs, which had higher percentages of water‐soluble carbohydrates, tannins, and hemicellulose. The guild of fruit‐eating bats on BCI included ten common species with diets dominated by figs. Fecal analyses and captures at ripe fig trees showed a consistent pattern of resource partitioning. Small bats preferentially ate small‐fruited and strangler figs while large bats consumed mostly large‐fruited and free‐standing figs. Small bats most often ate F. bullenei, which has high levels of lipid and carbohydrates, and F. yoponensis, which has high levels of protein. Medium and large bats most often ate F. insipida, a nutritionally superior species; their second most eaten species was F. obtusifolia, in which the large size may make it efficient to eat. Each bat ate a variety of fig species, supporting the idea that although no single species of fig may be sufficient to sustain frugivores, a mix of fig species can provide a complete set of nutrients.

Strangler Figs in a Stand of Dry Rainforest in the Lower Hunter Valley, NSW

A complete census was conducted of all hemi-epiphytic Ficus individuals within a single stand of dry rainforest. Substrate analyses were conducted on the material from potential hemi-epiphyte germination sites in an attempt to understand the factors influencing the distribution of hemi-epiphytic Ficus individuals within the stand. In all, 191 individuals of Ficus macrophylla ssp. macrophylla (Moreton Bay fig) and 65 individuals of Ficus superba var. henneana (deciduous fig) were found within the stand, providing a mean hemi-epiphyte density of 13.5/ha. Clear host preferences were shown for both fig species with two species, Olea paniculata (native olive) and Drypetes deplanchei (yellow tulip), shown to host 60 per cent and 21 per cent, respectively, of all hemi-epiphytes within the stand. These host trees are characterised by humus pockets that accumulate in depressions on their branches and trunk, as well as in branch axils. Their host potential is thought to be enhanced by the increased visitation of birds that feed on the fruit from both the hemi-epiphytes and these potential host trees. Substrate analyses revealed that while the highly organic epiphytic and rock-surface substrates had a high field capacity, their moisture holding capacity was low. The ponding of water and the reduced desiccation afforded by the microtopography of the germination sites ensures that these sites are more likely to maintain a viable moisture content. It appears that desiccation of the germination substrate could be the major cause of the high rate of juvenile hemi-epiphytic Ficus mortality.

Fruit characteristics and factors affecting fruit removal in a Panamanian community of strangler figs.

We describe fruiting characteristics for 12 species in a community of strangler figs (Moraceae: Urostigma) studied in Panama. We quantify diurnal and nocturnal removal rates and proportions of fruits removed, and relate them to the activities of the main dispersers of the figs: bats and birds. These results combined with previous studies show that there are clear differences between fig species with fruit that ripen red and those with fruit that remain green(ish). In the red-fruited species, the fruit are small, ripen asynchronously over relatively long periods, produce little scent, and are mainly taken during the day by birds. In contrast, in the green(ish)-fruited species, the fruits are larger, span a range of sizes, ripen relatively synchronously, produce very distinctive aromas, and are mainly taken at night by bats. This dichotomy in fruiting characteristics suggests coadaptive links between groups of dispersers and different species within the genus Ficus. All fig species produce a range of fruit crop sizes (10-155 fuits/m2 canopy area) of which a high proportion were removed by seed dispersers (>80%). Removal rates (fruit removed per day) were positively correlated with crop size, suggesting that trees with large crop size attract more frugivores. Removal rates of green-fruited figs were significantly lower and persistence and abortion of ripe fruit were significant higher around full moon, apparently due to the reduced activity of bats. We further estimate the number of bats that are sustained by a tree fruit crop and account for the observed fruit removal. We then discuss the evidence for coadaptation between different groups of figs and their seed dispersers, Finally, we consider the conservation implications for figs as keystone resources in tropical forests.

Nutritional Values of 14 Fig Species and Bat Feeding Preferences in Panama1

Figs are a critical resource for many tropical frugivores, yet they often are referred to as low quality fruits. To determine their nutritional value, both as a group and for individual species, we analyzed 14 fig species from Barro Colorado Island (BCI), Panama, for fiber, tannins, lipids, protein, carbohydrates, amino acids, and minerals. Seeds and pulp were analyzed separately. Fig fruit pulp consisted of about one-third digestible components, mostly carbohydrates with some lipids and proteins. Tannin, lignin, and water-soluble carbohydrates showed considerable variation among species, as did fruit size. Figs contained high amounts of amino acids, such as leucine, lysine, valine, and arginine, and minerals, such as potassium, calcium, magnesium, sodium, and phosphorus. One species, Ficus insipida, contained the highest concentrations of almost all amino acids, many minerals, and protein. Small figs had as much nutritional value per gram as large figs. Free-standing figs had higher percentages of protein, complex carbohydrates, and ash than strangler figs, which had higher percentages of water-soluble carbohydrates, tannins, and hemicellulose. The guild of fruit-eating bats on BCI included ten common species with diets dominated by figs. Fecal analyses and captures at ripe fig trees showed a consistent pattern of resource partitioning. Small bats preferentially ate small-fruited and strangler figs while large bats consumed mostly large-fruited and free-standing figs. Small bats most often ate F. bullenei, which has high levels of lipid and carbohydrates, and F. yoponensis, which has high levels of protein. Medium and large bats most often ate F. insipida, a nutritionally superior species; their second most eaten species was F. obtusifolia, in which the large size may make it efficient to eat. Each bat ate a variety of fig species, supporting the idea that although no single species of fig may be sufficient to sustain frugivores, a mix of fig species can provide a complete set of nutrients.

Ophioglossum pendulum L. Naturalized in Miami, Dade County, Florida

Ophioglossum pendulum L. Naturalized in Miami, Dade County, Florida.Ophioglossum pendulum L. has been discovered separately by Adrian Tejedor and Craig Allen, growing on cultivated palm trees in Miami, Florida. Ophioglossum pendulum is an Old World epiphyte, which grows from Madagascar through tropical Asia and into Polynesia. It has been infrequently cultivated in tropical fern collections in Miami since the mid-1970s. This is the first report of established plants growing outside of strictly man-made, horticultural conditions in the New World. This is quite a surprising discovery due to the relative difficulty of maintaining this exotic species in cultivation. Two populations are known in two separate sites in Coral Gables, a community located in southeast Miami. One population (discovered by Adrian Tejedor, in April, 1998) is growing in the persistent leaf bases of Canary Island date palms (Phoenix canariensis) along a public street. In this location, three colonies are on adjacent palms and a fourth is some distance away, in the same row of planted palms. A second, small population, is growing on a sugar palm (Arenga pinnata), inside of Fairchild Tropical Gardens. It was discovered during the summer of 1995, by Craig Allen. In both locations, mature, sporulating plants are growing among the old persistent leaf bases on the palm trunks. Two of the date palm colonies were relatively large and vigorous in 1998, the other two were smaller. The largest colony covered 1.5 square meters of the palm trunk, about ten feet from the ground, with an estimated number of 60 fronds. Considering the slow growth typical of 0. pendulum, this largest colony is estimated to be in excess of 15 years old, and may be much older. In March 1999, only 12 fronds were observed. The majority of the fronds observed the previous year had died and remained in place, completely dried and shriveled. Only the largest fronds bore sporangia. One fertile appendage is borne on the undersurface of the large fronds, which are from 45 to 90 cm. long. Most of the fronds in all the colonies are small, infertile and average 45 cm. in length. Specimens have been taken from this population to document its occurrence and are on deposit at the Fairchild Tropical Garden Herbarium (A. Tejedor, Fairchild Herbarium #81775). In Phoenix and other palm genera, a compact and spongy mass of old leaf bases remains attached to the palm's upper trunk for many years after the leaves are shed. This is where O. pendulum and other epiphytes become established. In the case of Ophioglossum, the dangling fronds are the only visible part of the plant. The rhizome and root system are hidden under the substrate of old leaf bases of the palm. Adventitious shoot buds that develop on the root system eventually produce a colony of plants on the south-east side of the trunk, sheltered by the leaf crown. The dead leaf bases have an ability to remain remarkably wet for days after a rain. The palm leaf-base habitat seems favorable for these ferns, which otherwise may not survive to South Florida's long, late winter and spring, dry season. During the dry winter of 1999 the colonies seemed to have suffered and appeared decidedly smaller. Other epiphytes that coexist with O. pendulum in this habitat are the Boston fern (Nephrolepis cordifolia) and young individuals of Ficus aurea (strangler fig) and 46

Studies in Urban Ecology: Strangler Figs in the Urban Parklands of Brisbane, Queensland, Australia

This study investigated the establishment dynamics of strangler figs and the constraints on their development in the urban parklands of Brisbane, Queensland, Australia. Of 3580 trees and palms in the study parks, approximately 5% support at least one Ficus species. Six Ficus species occur epiphytically in older parkland. Four are Brisbane natives: F. macrophylla, F. obliqua, F. platypoda and F. virens; and two are from elsewhere in Australia: F. benjamina and F. rubiginosa. A lack of pollinator wasps in the Brisbane area prevents exotic and other native Ficus spp. from reproducing. Though they form predominantly open communities, the percentage of phorophytes (support trees) in the study parks is similar to that associated with natural, closed communities. Ficus spp. become established in structural features that accumulate humic soil, such as the forks of trunks and branches on trees, and behind marcescent leaf bases on palms. Plants with few humus pockets support few Ficus species. Environmental factors such as atmospheric quality, canopy shade, bark texture and whether or not a park is irrigated, seem not to be consequential to Ficus establishment. Significantly greater numbers of Ficus occur on deciduous trees, perhaps because avian seed dispersers favour them as perches over evergreen trees. Ficus also occur significantly more frequently on the western sides of palms with marcescent leaf bases. These western flanks offer shelter from the prevailing sea breezes: fewer Ficus are therefore likely to be torn from these sides in strong winds.

Light or presence of host trees: which is more important for the strangler fig?

Strangler fig density varied considerably in the evergreen forest of Karian Shola National Park, southern India, with 11 individuals ha−1 in an open trail area and 5.6 individuals ha−1 within the primary forest area. The index of light level was assessed by estimating the percentage of upper canopy cover along the longitudinal centre of ten, 500-m × 20-m plots in each of the two areas of the evergreen forest. However, the increase in strangler fig density was not correlated to light levels but was significantly correlated to the numbers of their main host species in the two areas. In Karian Shola National Park, strangler figs occurred predominantly on a few host species with 20 and 50% of strangler figs growing on Vitex altissima, Diospyros bourdilloni and Eugenia/Syzygium spp. in the primary forest and trail areas respectively. Both young and established strangler figs were recorded mainly on larger individuals of their host trees indicating that older host trees are likely to be more suitable for the germination and establishment of strangler figs. The reason for the above could be the higher incidence of humus-filled and decaying regions in the older host trees which would provide an assured supply of nutrients for the establishing strangler fig.

The breeding structure of a tropical keystone plant resource

Despite the recognized importance of maintaining viable populations of keystone plant resources in tropical wildlife parks and forested preserves, the critical question of what constitutes effective breeding units of these species has not been directly addressed. Here we use paternity analysis techniques to reconstruct the genotypes of pollen donor trees and to estimate pollen dispersal distances and breeding population size parameters for Panamanian populations of seven species of monoecious strangler figs (Ficus, Moraceae), a particularly widespread and influential group of keystone producers1,2,3. Despite the minute size (1–2 mm) and short lifespan (2–3 d) of the species-specific wasp pollinators (Agaonidae, Chalcidoidea), pollen dispersal was estimated to occur routinely over distances of 5.8–14.2 km between widely spaced host trees. As a result of such extensive pollen movement, breeding units of figs comprise hundreds of intermating individuals distributed over areas of 106–632 km2, an order of magnitude larger than has been documented for any other plant species. Moreover, these results should be generalizable to the 350 or so monoecious fig species that share this pollination system4. The large areal extent of breeding units of these keystone plant resources has important implications for our understanding of both the evolution of tropical biodiversity and its maintenance by applied conservation efforts.

Within‐Crown Flowering Synchrony in Strangler Figs, and Its Relationship to Allofusion1

ABSTRACTWe studied flowering phenology at the level of individual branches within strangler fig trees to determine (1) whether branches bloomed asynchronously within trees and (2) whether asynchrony, if observed, could be ascribed to genetically different branches of mosaic trees (i.e., trees formed by spontaneous grafting of genetically different individuals) undergoing individual flowering cycles that were out of phase with each other. Although asynchrony was fairly common, it most often reflected individual branches failing to bloom during one flowering episode, then coming back to bloom in synchrony at the next episode. We detected fewer mosaic trees than expected, and found only a very weak suggestion that mosaic trees may show less within‐tree synchrony than simple trees.

Reproductive and Genetic Consequences of Forest Fragmentation: Two Case Studies of Neotropical Canopy Trees

Large areas of continuous tropical forests are rapidly becoming fragmented as a result of human activities, prompting a growing need for information on the reproductive and genetic responses of tree species to disturbance. Here we review the literature on pollen dispersal in continuous forest stands in order to identify factors expected to enhance or to inhibit interfragment pollen flow. We then describe two empirical studies of the effects of fragmentation on pollen flow in Neotropical populations of Spondias mombin (Anacardiaceae) and five monoecious species of Ficus (Moraceae). In S. mombin, small fragment populations suffered significant reductions in germination rate and fruit production relative to large fragment and continuous forest populations. Nevertheless, 90-100% of the progeny produced in the small fragments were the product of pollen gene flow originating from forest stands located over 80-1000 m away. In contrast to S. mombin, which is relatively abundant and pollinated by a variety of small insects, the strangler fig species studied were relatively rare and pollinated by species-specific wasps that are both small and short-lived. Paternity analyses revealed these highly coevolved pollinators to be effective agents of pollen movement over very long distances, routinely dispersing 6-14 km to receptive host trees. Because of such extensive pollen flow, breeding populations of figs were estimated to consist of hundreds of intermating individuals distributed over 108-632 km2, an area substantially larger than has been documented for any other plant species. The observed patterns of dispersal in S. mombin and Ficus demonstrate the potential for ecologically and evolutionarily significant pollinator and pollen movement among populations occurring in both disturbed and continuous forest environments. Moreover, given the integral relationship of figs, as keystone plant resources, to other plant and animal species, the extensive spatial scale of fig breeding units demonstrates how the conservation of biodiversity in spatially isolated reserves may be dependent on the preservation of forest elements in a surrounding fragmented landscape.