Do Bird Perching Structures Elevate Seed Rain and Seedling Establishment in Abandoned Tropical Pasture?

Lack of seed dispersal has been shown to be a major factor limiting tropical forest recovery in abandoned pasture land. The goal of this work was to determine whether bird perching structures serve to enhance seed dispersal and seedling establishment in an abandoned pasture in Costa Rica. Two types of perching structures (crossbar and branch) were tested. Bird visitation rates were significantly higher on branch than on crossbar perches. The number of animal-dispersed seeds was significantly higher below branch perches than below crossbar perches or in open pasture. Despite differences in seed rain, percent cover of animal-dispersed plants and the number of seedlings of animal-dispersed plant species were similar below both perch types and in open pasture. Baiting perches with bananas did not increase either bird visitation rates or seed rain. These results suggest that, although bird perching structures increase seed dispersal, they do not overcome other barriers to tropical forest recovery such as seed predation and low seed germination.     

Do Tropical Cyclones Shape Shorebird Habitat Patterns? Biogeoclimatology of Snowy Plovers in Florida

Background

The Gulf coastal ecosystems in Florida are foci of the highest species richness of imperiled shoreline dependent birds in the USA. However environmental processes that affect their macroecological patterns, like occupancy and abundance, are not well unraveled. In Florida the Snowy Plover (Charadrius alexandrinus nivosus) is resident along northern and western white sandy estuarine/ocean beaches and is considered a state-threatened species.

Methodology/Principal Findings

Here we show that favorable nesting areas along the Florida Gulf coastline are located in regions impacted relatively more frequently by tropical cyclones. The odds of Snowy Plover nesting in these areas during the spring following a tropical cyclone impact are seven times higher compared to the odds during the spring following a season without a cyclone. The only intensity of a tropical cyclone does not appear to be a significant factor affecting breeding populations.

Conclusions/Significance

Nevertheless a future climate scenario featuring fewer, but more extreme cyclones could result in a decrease in the breeding Snowy Plover population and its breeding range. This is because the spatio-temporal frequency of cyclone events was found to significantly affect nest abundance. Due to the similar geographic range and habitat suitability, and no decrease in nest abundance of other shorebirds in Florida after the cyclone season, our results suggest a common bioclimatic feedback between shorebird abundance and tropical cyclones in breeding areas which are affected by cyclones.     

Are Ridge Habitats Special Sites for Endemic Plants in Tropical Montane Rain Forests? A Case Study of Pteridophytes in Ecuador

We addressed whether ridges, which are ecologically distinct from slopes, harbor specialized plant assemblages with a high representation of endemic species. We surveyed pteridophytes in 28 plots each of 400 m² in ridge and slope forests at 2,430–2,660 m at three different localities in southeastern Ecuador. Data analysis was based on those 147 species with reliable determinations and excluded 14 undetermined species. Range sizes were expressed as the latitudinal distance between the northern- and southernmost collections, and species were then assigned to range-size quartiles, with the 1st quartile including the 25% most widespread species, etc. Differences in species richness per range-size quartile were determined using G-tests and differences in abundance using ANOVAs. The recorded 147 fern species were represented by 21,800 individuals, including 106 terrestrial (7,300 individuals) and 98 epiphytic species (14,500). Ridges had fewer species than slopes, and there was no higher representation of localized species on ridges. Overall, widespread species were weakly (R²?=?0.03) but significantly more abundant than localized species. Ridges had significantly higher abundances of terrestrial – but not of epiphytic – species compared to slopes, especially among the widespread species of the 1st range-size quartile. The contribution of ridge habitats to overall pteridophyte diversity and as habitats for endemics in our study region is low. Methodologically, the separation of species into range-size classes in an ecological study is novel and effective, as statistically significant patterns were found only for species belonging to the 1st or 4th quartiles.     

Rook Spring Seed Dispersal in the Agricultural Landscape – Frugivory, Granivory or Accidental Transport?

Seed dispersal seems to be extremely important in agrocoenoses where suitable habitats (patches) are surrounded by an unfavourable environment (matrix). The role of the rook Corvus frugilegus, an omnivorous bird, in seed dispersal was studied in the agricultural landscape of Eastern Poland. We analyzed 739 pellets produced by regurgitation, which were collected under breeding colonies in April, May and June. Our goal was to i) assess the structure of the seed pool in pellets; ii) evaluate the temporal variation in the pellet seed pool on two different time scales; iii) compare the species composition of seeds in pellets and vegetation under the rook nests. Seeds were present in 18 % of pellets; 571 seeds were found, half of them belonging to dry-fruited species, without any obvious adaptations to endozoochory. These seeds could be an additional source of food, or they could have been accidentally swallowed during foraging for other food items. Taking into consideration the abundance of the rook population, we assessed the mean number of seeds transferred by one bird to be from 4 seeds per month in April and up to 160 seeds in June. The most important factor responsible for qualitative and quantitative structure of seed pool in pellets is the time when pellets were regurgitated. The type and availability of food determines the number and species structure of dispersed seeds. The comparison of the species structure of the seed pool in pellets and of the herb layer under the breeding colonies showed that the rook could effectively disperse seeds of weeds, meadow and ruderal species, that could germinate under the dense canopy of trees at the studied sites.     

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

Spatial and temporal patterns of seed bank dynamics In relation to gaps in an old growth tropical montane rainforast of Hainan Island, South China, were studied over two consecutive years. From June 2001 to June 2003, soil seed bank sampling blocks were taken near each of the four sides of each seed trap and immediately put into a nursery for observation of seedling emergence dynamics in four seasons (each experiment in each season). The abundances of seedlings that emerged from seed banks showed the trend of vine functional group (VFG) > shrub functional group (SFG) > tree functional group (TFG) > herb functional group (HFG), but the trend in species richness of seedlings that emerged from the soil seed banks was TFG > VFG > SFG > HFG. The abundances of seedlings that emerged from seed banks in the three gap zones showed no significant differences, but significant differences did exist for the species richness. The time of sampling or seasons of experiments had significant influences on both the species richness and seedling abundances. The seedling emergence processes of each experiment all revealed the unimodal patterns. Few emergences occurred 1 year after each experiment. Compared with those under closed canopies, the recruitment rates from seed to seedlings and from seedlings to saplings in gaps were higher, but the mortality rates from saplings to big trees were also higher in the gaps.     

Do Hybrid Trees Inherit Invasive Characteristics? Fruits of Corymbia torelliana X C. citriodora Hybrids and Potential for Seed Dispersal by Bees

Tree invasions have substantial impacts on biodiversity and ecosystem functioning, and trees that are dispersed by animals are more likely to become invasive. In addition, hybridisation between plants is well documented as a source of new weeds, as hybrids gain new characteristics that allow them to become invasive. Corymbia torelliana is an invasive tree with an unusual animal dispersal mechanism: seed dispersal by stingless bees, that hybridizes readily with other species. We examined hybrids between C. torelliana and C. citriodora subsp. citriodora to determine whether hybrids have inherited the seed dispersal characteristics of C. torelliana that allow bee dispersal. Some hybrid fruits displayed the characteristic hollowness, resin production and resin chemistry associated with seed dispersal by bees. However, we did not observe bees foraging on any hybrid fruits until they had been damaged. We conclude that C. torelliana and C. citriodora subsp. citriodora hybrids can inherit some fruit characters that are associated with dispersal by bees, but we did not find a hybrid with the complete set of characters that would enable bee dispersal. However, around 20,000 hybrids have been planted in Australia, and ongoing monitoring is necessary to identify any hybrids that may become invasive.     

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

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

The Lethal Fungus Batrachochytrium dendrobatidis Is Present in Lowland Tropical Forests of Far Eastern Panamá

The fungal disease chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), is one of the main causes of amphibian population declines and extinctions all over the world. In the Neotropics, this fungal disease has caused catastrophic declines in the highlands as it has spread throughout Central America down to Panamá. In this study, we determined the prevalence and intensity of Bd infection in three species of frogs in one highland and four lowland tropical forests, including two lowland regions in eastern Panamá in which the pathogen had not been detected previously. Bd was present in all the sites sampled with a prevalence ranging from 15–34%, similar to other Neotropical lowland sites. The intensity of Bd infection on individual frogs was low, ranging from average values of 0.11–24 zoospore equivalents per site. Our work indicates that Bd is present in anuran communities in lowland Panamá, including the Darién province, and that the intensity of the infection may vary among species from different habitats and with different life histories. The population-level consequences of Bd infection in amphibian communities from the lowlands remain to be determined. Detailed studies of amphibian species from the lowlands will be essential to determine the reason why these species are persisting despite the presence of the pathogen.     

Differences in Morphometry and Activity among Tabanid Fly Assemblages in an Andean Tropical Montane Cloud Forest: Indication of Altitudinal Migration?

Evidence suggests that variations along ecological gradients shape organism traits such as behavior or morphometry. We studied the effect of altitude on the flight activity of tropical tabanid fly assemblages of one species of Stypommisa Enderlein along a 1 km altitudinal gradient on the northwestern slopes of the Ecuadorian Andes. Our objectives were as follows: (1) to test the hypothesis that highland individuals present larger flight body structures; and (2) to compare the flight activity patterns of flies’ assemblages among altitudes and correlate it with weather factors. We sampled specimens in Malaise traps at 1180, 1680 and 2180 m of altitude from 0600 to 1830 h for 20 d at each site. Seven weather variables were measured every hour and flight activity was inferred from relative tabanid fly abundances/hour in traps. We measured morphometrical parameters that included tabanid fly body size, thorax volume, wing area and wing loading. Flight activity patterns revealed a bimodal distribution at 1680 m, and two asynchronous unimodal distributions, one at 1180 and one at 2180 m. GLM analyses revealed that temperature, mist and rainfall were the best predictors of fly activity differences among altitudes. Morphometrical analyses showed that body size and thorax volume increased with increasing altitude. Synchronous groups of flies at different altitudes (those between 1180–1680_(pm) m, and 1680_(am)–2180 m) were morphologically similar, suggesting that flies could be capable of migrating from highlands to lowlands at defined hours of the day depending on forest weather conditions.     

Do Epigeal Termite Mounds Increase the Diversity of Plant Habitats in a Tropical Rain Forest in Peninsular Malaysia?

The extent to which environmental heterogeneity can account for tree species coexistence in diverse ecosystems, such as tropical rainforests, is hotly debated, although the importance of spatial variability in contributing to species co-existence is well recognized. Termites contribute to the micro-topographical and nutrient spatial heterogeneity of tropical forests. We therefore investigated whether epigeal termite mounds could contribute to the coexistence of plant species within a 50 ha plot at Pasoh Forest Reserve, Malaysia. Overall, stem density was significantly higher on mounds than in their immediate surroundings, but tree species diversity was significantly lower. Canonical correspondence analysis showed that location on or off mounds significantly influenced species distribution when stems were characterized by basal area. Like studies of termite mounds in other ecosystems, our results suggest that epigeal termite mounds provide a specific microhabitat for the enhanced growth and survival of certain species in these species-rich tropical forests. However, the extent to which epigeal termite mounds facilitate species coexistence warrants further investigation.     

What Cues Do Ungulates Use to Assess Predation Risk in Dense Temperate Forests?

Anti-predator responses by ungulates can be based on habitat features or on the near-imminent threat of predators. In dense forest, cues that ungulates use to assess predation risk likely differ from half-open landscapes, as scent relative to sight is predicted to be more important. We studied, in the Białowieża Primeval Forest (Poland), whether perceived predation risk in red deer (Cervus elaphus) and wild boar (Sus scrofa) is related to habitat visibility or olfactory cues of a predator. We used camera traps in two different set-ups to record undisturbed ungulate behavior and fresh wolf (Canis lupus) scats as olfactory cue. Habitat visibility at fixed locations in deciduous old growth forest affected neither vigilance levels nor visitation rate and cumulative visitation time of both ungulate species. However, red deer showed a more than two-fold increase of vigilance level from 22% of the time present on control plots to 46% on experimental plots containing one wolf scat. Higher vigilance came at the expense of time spent foraging, which decreased from 32% to 12% while exposed to the wolf scat. These behavioral changes were most pronounced during the first week of the experiment but continuous monitoring of the plots suggested that they might last for several weeks. Wild boar did not show behavioral responses indicating higher perceived predation risk. Visitation rate and cumulative visitation time were not affected by the presence of a wolf scat in both ungulate species. The current study showed that perceived predation risk in red deer and wild boar is not related to habitat visibility in a dense forest ecosystem. However, olfactory cues of wolves affected foraging behavior of their preferred prey species red deer. We showed that odor of wolves in an ecologically equivalent dose is sufficient to create fine-scale risk factors for red deer.     

Spiny Norman in the Garden of Eden? Dispersal and early biogeography of Placentalia

The persistent finding of clades endemic to the southern continents (Afrotheria and Xenarthra) near the base of the placental mammal tree has led molecular phylogeneticists to suggest an origin of Placentalia, the crown group of Eutheria, somewhere in the southern continents. Basal splits within the Placentalia have then been associated with vicariance due to the breakup of Gondwana. Southern-origin scenarios suffer from several problems. First, the place of origin of Placentalia cannot be reconstructed using phylogenetic reasoning without reference to outgroups. When available outgroups are considered, a Laurasian origin is most parsimonious. Second, a model of pure vicariance would require that basal placental splits occurred not with the breakup of Gondwana, but of Pangea in the Late Triassic—Early Jurassic. This event long preceded even the oldest molecular divergence estimates for the Placentalia and was coeval only with the earliest mammals in the fossil record. Third, a problem with the number of dispersal events that would be required emerges under different southern-origin scenarios. In considering the geographic distribution of the major placental clades at their first appearance (mostly Early Cenozoic), it becomes clear that a Laurasian center of origin would require fewer dispersal events. Southern-origin models would require at least twice the number of dispersal events in comparison with a model of Laurasian origins. This number of required dispersal events increases if extinct groups of placental mammals are also considered. Results are similar assuming a morphology-based phylogeny. These facts, along with earlier findings speaking against a major placental radiation deep in the Cretaceous without leaving fossil evidence, suggest an origin of Placentalia somewhere in Laurasia with few supraordinal splits occurring before the last 5–10 million years of the Cretaceous.     

Patterns of Migration and Risks Associated with Leprosy among Migrants in Maranh?o,Brazil

Leprosy remains a public health problem in Brazil with new case incidence exceeding World Health Organization (WHO) goals in endemic clusters throughout the country. Migration can facilitate movement of disease between endemic and non-endemic areas, and has been considered a possible factor in continued leprosy incidence in Brazil. A study was conducted to investigate migration as a risk factor for leprosy. The study had three aims: (1) examine past five year migration as a risk factor for leprosy, (2) describe and compare geographic and temporal patterns of migration among past 5-year migrants with leprosy and a control group, and (3) examine social determinants of health associated with leprosy among past 5-year migrants. The study implemented a matched case-control design and analysis comparing individuals newly diagnosed with leprosy (n = 340) and a clinically unapparent control group (n = 340) without clinical signs of leprosy, matched for age, sex and location in four endemic municipalities in the state of Maranhão, northeastern Brazil. Fishers exact test was used to conduct bivariate analyses. A multivariate logistic regression analysis was employed to control for possible confounding variables. Eighty cases (23.5%) migrated 5-years prior to diagnosis, and 55 controls (16.2%) migrated 5-years prior to the corresponding case diagnosis. Past 5 year migration was found to be associated with leprosy (OR: 1.59; 95% CI 1.07–2.38; p = 0.02), and remained significantly associated with leprosy after controlling for leprosy contact in the family, household, and family/household contact. Poverty, as well as leprosy contact in the family, household and other leprosy contact, was associated with leprosy among past 5-year migrants in the bivariate analysis. Alcohol consumption was also associated with leprosy, a relevant risk factor in susceptibility to infection that should be explored in future research. Our findings provide insight into patterns of migration to localize focused control efforts in endemic areas with high population mobility.     

Do parameters of seminal quality correlate with the results of on-farm inseminations in rabbits?

This study was conducted to determine if different sperm characteristics correlate with the in vivo fertility of rabbit sperm. A total of 2,765 heterospermic inseminations were performed in commercial rabbitries using 50-pooled samples of fresh semen. Sperm motility and morphological evaluations were performed on each of the heterospermic pooled samples to asses the seminal quality, and the percentage of kindling rate (76.2%) and number of kits born alive (9.3) were recorded. Sperm motility parameters, assessed using a computer-assisted sperm analysis (CASA) system (Sperm Class Analyzer, Microptic, Barcelona, Spain), were: average path velocity, curvilinear velocity, straight-line velocity, linearity, amplitude of lateral head displacement, beat cross-frequency, wobble and percentage of total motile spermatozoa. Morphological analyses included the percentage of sperm with a normal apical ridge, the percentage of sperm with cytoplasmatic droplets and the percentage of abnormal sperm. Significant correlations were observed between kindling rate and the percentage of total motile cells (r=0.31; P<0.05), linearity index (r=-0.32; P<0.05) and the percentage of abnormal sperm in the sample (r=-0.32; P<0.05). Regression models including motility and the morphological parameters explained 45% of the variation in kindling rate. These results indicate that motility parameters, determined by CASA systems, in combination with sperm morphology analyses can provide some information about the fertilizing potential of rabbit sperm.     

Does Restoration Enhance Regeneration of Seasonal Deciduous Forests in Pastures in Central Brazil?

The goal of restoration is to accelerate ecosystem recovery, but in ecosystems that naturally regenerate rapidly restoration techniques need to be selected carefully to facilitate rather than impede natural recovery. We compared the effects of five restoration techniques, such as plowing the soil, removing grasses, adding forest litter, seeding, and planting nursery‐growing seedlings, on the regeneration of seasonal deciduous forest trees in four abandoned pastures in central Brazil. We monitored all woody stems immediately prior to treatments and again 14 months after the treatments. We recorded an average of 16,663 tree stems per hectare and a total of 83 species before implementing treatments. Planting strongly increased species richness; adding litter and seeding had weaker positive effects on richness; and plowing and grass removal had no effect. Plowing substantially reduced the density of naturally established stems. Despite the high survival of planted seedlings, stem density in planting treatments did not change because the tractor and digging holes to plant seedlings caused mortality of naturally regenerating seedlings. Tree stems grew more in the grass release plots than in the control plots. Our results suggest that early succession of seasonal deciduous forest in pastures in the region studied does not need to be stimulated once the perturbation is stopped and that intensive restoration efforts may actually slow recovery. We recommend only enrichment planting of seedlings that are not able to resprout.     

Do Species Sorting and Mass Effects Drive Assembly in Tropical Agroecological Landscape Mosaics?

Recent assessments of biodiversity in tropical agroecosystems have revealed surprisingly high functional and taxonomic diversity in systems with low management intensity. This biodiversity is the product of community assembly. Because agroecosystems are novel ecosystems and occur in landscape mosaics, the assembly processes generating communities in agroecosystems are poorly resolved. Broadly, two models have been proposed to explain landscape assembly: trade‐offs in species performance across habitats (species sorting) and source‐sink dynamics between habitats of differential quality (mass effects). These models are largely untested in tropical agroecosystems. We utilize an extensive data set on a tropical twig‐nesting ant community from five microhabitat types in a shaded coffee agroecosystem to test for species sorting, mass effects, or a mixed model. To test among these models, we used community similarity and a variance decomposition on a focal microhabitat (a moderate‐shade coffee farm) to partition community variance into spatial and environmental components. To identify the source habitat for mass effects and assess their strength, we measured dispersing alates (winged reproductives), artificial nests, and colony and nest size in shade trees and coffee. We found significant environmental and spatial signal and evidence for both species sorting and mass effects. We find sorting occurs among common species, but that mass effects are prevalent among rare species and likely originate in the shade trees. Our results indicate that both metacommunity models occur in tropical landscape mosaics, but they may not apply equally to all species in communities, habitat gradients, or timescales.