A mast fruiting episode of the tropical tree Peltogyne purpurea (Caesalpinaceae) in the Osa Peninsula, Costa Rica

The existence of mast fruiting has not been well documented in the Neotropics. The occurrence of a mast fruiting episode in the population of the tree Peltogyne purpurea in the Osa Peninsula of Costa Rica is described. In February and March of 2000 most of the trees of this species produced a large fruit crop, compared with 1995-1999, when the number of fruit producing trees was very low or zero and those that did bear fruit, did so at a low intensity. In contrast, the fruit crop of 2000 was massive, all trees examined produced fruits and the intensity of fruiting was maximal. There is not enough information on the event for a hypothesis to be formed because the climatic or biological cues that triggered this sporadic flowering are unknown and there is no meteorological data available for this area. Populations with this mode of reproduction may experience local extinction bacause of logging operations.     

Phytogeography of the trees of the Osa Peninsula,Costa Rica

A phytogeographic analysis of the distributions of 454 species of trees native to the Osa Peninsula in 22 families revealed that 4.8% of the species are endemic to the Osa Peninsula and the adjacent mainland of Costa Rica. However, nearly one-fourth of the species might be regionally endemic to Central-South Mesoamerica (Costa Rica, Nicaragua, and Panama). Our sample suggests that 53.6% of the species occur in some part of Mesoamerica and sometimes range into northwestern South America, and that 44.5% of the species have wide distributions throughout tropical America. There is a strong affinity with the flora of northwestern South America, with 46.2% of the species on the Osa also found there. In addition, 50.6% of the tree species on the Osa occur on both the Atlantic and Pacific slopes of Central America or, if they reach South America, are sometimes found on both sides of the Andes. Major contributions to the tree flora of the Osa have been made by species arriving in the Osa by 1) dispersal from South and North America to islands in proto Central America before the formation of a dry-land connection between the two continents, and 2) migration from South America and North America after the closure of the Panamanian isthmus was made. This analysis demonstrates the importance of the Osa as a regional refuge for protecting species with distributions limited to the Osa and parts of Panama, Costa Rica, or Nicaragua. The Osa is also important because it harbors the last expanse of tropical wet forest on the Pacific slope of Central America large enough to ensure the survival of the Central American populations of widely distributed plants and animals.     

Topographic distributions of emergent trees in tropical forests of the Osa Peninsula,Costa Rica

Tropical rainforests are reservoirs of terrestrial carbon and biodiversity. Large and often emergent trees store disproportionately large amounts of aboveground carbon and greatly influence the structure and functioning of tropical rainforests. Despite their importance, controls on the abundance and distribution of emergent trees are largely unknown across tropical landscapes. Conventional field approaches are limited in their ability to characterize patterns in emergent trees across vast landscapes with varying environmental conditions and floristic composition. Here, we used a high‐resolution light detection and ranging (LiDAR) sensor aboard the Carnegie Airborne Observatory Airborne Taxonomic Mapping System (CAO‐AToMS) to examine the abundance and distribution of tall emergent tree crowns (ETC) relative to surrounding tree crowns (STC) across the Osa Peninsula, a geologically and topographically diverse region of Costa Rica. The abundance of ETC was clearly influenced by fine‐scale topographic variation, with distribution patterns that held across a variety of geologic substrates. Specifically, the density of ETC was much greater on lower slopes and in valleys, compared to upper slopes and ridges. Furthermore, using the CAO high‐fidelity imaging spectrometer, ETC had a different spectral signature than that of STC. Most notably, ETC had lower remotely sensed foliar nitrogen than STC, which was verified with an independent field survey of canopy leaf chemistry. The underlying mechanisms to explain the topographic‐dependence of ETCs and linkages to canopy N are unknown, and remain an important area of research.     

Landscape-Scale Controls on Aboveground Forest Carbon Stocks on the Osa Peninsula,Costa Rica

Tropical forests store large amounts of carbon in tree biomass, although the environmental controls on forest carbon stocks remain poorly resolved. Emerging airborne remote sensing techniques offer a powerful approach to understand how aboveground carbon density (ACD) varies across tropical landscapes. In this study, we evaluate the accuracy of the Carnegie Airborne Observatory (CAO) Light Detection and Ranging (LiDAR) system to detect top-of-canopy tree height (TCH) and ACD across the Osa Peninsula, Costa Rica. LiDAR and field-estimated TCH and ACD were highly correlated across a wide range of forest ages and types. Top-of-canopy height (TCH) reached 67 m, and ACD surpassed 225 Mg C ha^-1, indicating both that airborne CAO LiDAR-based estimates of ACD are accurate in tall, high-biomass forests and that the Osa Peninsula harbors some of the most carbon-rich forests in the Neotropics. We also examined the relative influence of lithologic, topoedaphic and climatic factors on regional patterns in ACD, which are known to influence ACD by regulating forest productivity and turnover. Analyses revealed a spatially nested set of factors controlling ACD patterns, with geologic variation explaining up to 16% of the mapped ACD variation at the regional scale, while local variation in topographic slope explained an additional 18%. Lithologic and topoedaphic factors also explained more ACD variation at 30-m than at 100-m spatial resolution, suggesting that environmental filtering depends on the spatial scale of terrain variation. Our result indicate that patterns in ACD are partially controlled by spatial variation in geologic history and geomorphic processes underpinning topographic diversity across landscapes. ACD also exhibited spatial autocorrelation, which may reflect biological processes that influence ACD, such as the assembly of species or phenotypes across the landscape, but additional research is needed to resolve how abiotic and biotic factors contribute to ACD variation across high biomass, high diversity tropical landscapes.     

Phenology of the tree Sideroxylon capiri (Sapotaceae) at the tropical dry forest in Costa Rica

From March 1996 until February 2000, an study about the phenology of the Tempisque tree [Sideroxylon capiri (A.DC.) Pittier] was made in the Tropical Dry Forest of the Barra Honda National Park (Costa Rica). Ten trees were chosen at random and their phenology was evaluated monthly during the first two years and every two months afterwards. Climatological data were also collected in situ. Trees change their foliage each year during the rainy season or at the beginning of the dry season. In contrast with other native species in forest, soil water deficit is not responsible for foliage change in S. capiri. Some elements that affect the process are photoperiod and herbivores. Unknown physiological mechanisms allow the tree to maintain foliage during the driest months (March and April). Flowering and fruiting may occur every year and in any season, but mostly in the dry season, with variability both among seasons and among individuals.     

Population structure and genetic diversity in four tropical tree species in Costa Rica

Despite intensified interest in conservation of tropical forests, knowledge of the population genetics of tropical forest trees remains limited. We used random amplified polymorphic DNA (RAPD) data to evaluate trends in genetic diversity and differentiation for four tropical tree species, Alchornea latifolia, Dendropanax arboreus, Inga thibaudiana and Protium glabrum . These species occur at contrasting population densities along an elevational gradient and we use RAPD and ecological data to examine natural levels of genetic diversity of each species, trends in genetic variability with population density and structure, genetic differentiation along the elevation gradient, and the relationship between genetic diversity and such factors as seed dispersal and pollination syndrome. At the distances we examined (plot distances ranging from 0.8 to 8.6 km) there was very little genetic structuring at any distance along the gradient. All four species exhibited levels of variation expected for spatial distribution, mating system and pollinator syndrome; greater than 96% of the genetic variation occurred within plots for Inga thibaudiana, Protium glabrum and Dendropanax arboreus. Alchornea latifolia only occurred in a single plot. The results of this study contribute to a growing database of genetic diversity data that can be utilized to make predictions about the effect of disturbance and subsequent reductions in population size on genetic variation and structure in tropical tree species.     

Monitoring of the mangrove forest at Gandoca, Costa Rica (CARICOMP site)

The mangrove forest at Gandoca, Refugio Nacional de Vida Silvestre Gandoca-Manzanillo, Caribbean coast of Costa Rica, has been monitored since 1999, following the CARICOMP protocol. The dominant species was the red mangrove, Rhizophora mangle. The peak of productivity and flowering was in July. The mangrove productivity decline from 2001 to 2004 while the temperature rised. Biomass (14 kg/m2) and density (9 trees/10 m2) in Gandoca were relatively low compared to other CARICOMP sites, while productivity in July in Costa Rica (4 g/m2/day) was intermediate, similar to most CARICOMP sites.     

Variation in the breeding behavior of the dry forest tree Enterolobium cyclocarpum (guanacaste) in Costa Rica

We studied the breeding systems of four populations of Enterolobium cyclocarpum (guanacaste, earpod tree) in Costa Rica. Multilocus estimates of the outcrossing rate indicate that E. cyclocarpum is a predominant outcrossing species (t(m) ranged between 0.881 and 0.901) and biparental inbreeding is low (range between 0.058 and 0.079). Overall, our analyses showed significant differences in the gene frequencies between pollen and ovules and significant differences in pollen gene frequencies between the four populations. We also found significant differences in the pollen gene frequencies calculated for single trees in the same population. Outcrossing rates and pollen gene frequencies varied in two consecutive years in two populations of E. cyclocarpum. The correlated mating model revealed that there are differences in the correlation of paternity between populations and years. These findings indicate that there is variation in the average number of trees that father the seed crop of each tree and/or that some fathers are overrepresented in the seed crop of each tree. The implication of these findings for the development of strategies for conservation and management of this species are discussed.     

Restoration of genetic diversity in the dry forest tree Swietenia macrophylla (Meliaceae) after pasture abandonment in Costa Rica

We studied the levels of genetic diversity of Swietenia macrophylla (big leaf mahogany) in five successional plots in the Santa Rosa National Park, Guanacaste, Costa Rica. We selected sites with different lengths of time since the last major disturbance (typically fire): 6, 9, 15 and 20 years. In addition, we also included a patch of mature forest that had experienced selective logging and other human activity in the past 100 years. Genetic diversity was assessed using five polymorphic DNA microsatellite loci. We found a total of 21 alleles in the five loci examined, in which the number of alleles present varied among the five sites studied. Allelic diversity varied between sites ranging from 20 to 14 alleles, and our data revealed that earlier successional sites have more alleles than older sites. There was significant heterogeneity in allele frequencies between sites; however, genetic differentiation between populations was low (FST = 0.063) indicating that most of the variation was found within sites and extensive gene flow between sites. In addition, our analysis also showed that genetic diversity of adult trees does not solely determine the diversity of seedlings and saplings found around them, also supporting the existence of extensive gene flow. The impact of these findings for the design of conservation strategies for tropical dry forests trees is discussed.     

Phenological behavior of the tree Elaeagia uxpanapensis (Rubiaceae), in a premontane rain forest of Costa Rica

Phenology of the tree Elaeagia uxpanapensis was studied from March 1994 to March 1998. This species is a canopy emergent in the A.M. Brenes Biological Reserve, Alajuela, Costa Rica. Fifteen mature trees were marked in order of appearance and observed every month using bionculars. A platform was built on one three better distinguished the transition from flowering to fruiting. Leaf abscission and budding were continuous throughout the year with several peaks, while flowering and fruit production occurred every 28 and 25 months, respectively. Leaf-fall was positively correlated with a ir temperature (n = 13, r = 0.44, p < 0.05), and fruiting with precipitation (n = 13, r = 0.37, p < 0.05) and relative humidity (n = 13, r = 0.44, p < 0.05). Bud formation was in inversely associated with precipitation (n = 13, r = 0.66 p < 0.05) and relative humidity ( n = 13, r = 0.61, p < 0.05).     

Feeding habits of the squirrel Sciurus variegatoides (Rodentia: Sciuridae) in the Nicoya Peninsula, Costa Rica

Food items consumed by the squirrel Sciurus variegatoides atrirufus were determined in an agricultural setting in the Nicoya Peninsula (9 degrees 47' N, 84 degrees 56' W), Costa Rica, where two life zones (Premontane Moist Forest Basal Belt Transition, and Tropical Dry Forest) predominate. By analyzing the gut contents of 120 squirrels, from February 1987 through January 1988, it was determined that coconut (Cocos nucifera), indian almond (Terminalia catappa) and flamboyant (Delonix regia) were the most common dietary items. There were differences in food consumption according to age: adults preferred coconut, whereas young individuals preferred almond. This finding can be explained in terms of fruit characteristics, as well as tree architecture and accessibility for squirrels; almendro trees provide higher protection and a more accessible food resource, so that it was better used by young individuals.     

Seagrass monitoring at Perezoso, Cahuita, Costa Rica (CARICOMP site)

The seagrass of Perezoso (Cahuita National Park, Caribbean coast of Costa Rica) was monitored using the CARICOMP protocol. Productivity (2.7 +/- 1.15 g/m2/d; n=74) was intermediate, compared to other Caribbean sites. Total biomass was intermediate to high (750-1500 g/m2) at most CARICOMP sites (Colombia, Cuba, Mexico, Puerto Rico and Venezuela) including Costa Rica (822.8 +/- 391.84 g/m2; n=32). Turnover rates were high (5.5 +/- 1.36%; n=74) compared to what was found in March and August at other sites. Shoot densities average 725 shoots/m2, in the Caribbean region, while in Costa Rica the value was higher (1184 +/- 335.5 shoots/m2). Average leaf length and width in the entire region were 14.4 cm and 10.6 mm, respectively, similar to what we found, but leaf area index average 3.4 m2 m(-2), higher than what was found in Costa Rica (0.92 m2 m(-2)). At Cahuita, seagrass productivity was significantly lower in March 2005 compared with the previous six years, and biomass has decreased with time. Seagrass productivity and biomass are being affected by the maximum temperatures, which increased by almost 10 degrees C from 1999 to 2005, and show a high negative correlation. Turnover rate and temperature were not correlated. Recreational boating, swimming and nutrient loading from deforested lands in the coast, the upstream rivers and local pollution are potential sources of impact to the seagrass beds at Cahuita.     

Inter-annual higher germination from smaller than medium-sized premontane wet forest fragments for an animal-dispersed tree species in Costa Rica

Forest fragmentation is pervasive in tropical landscapes, and animal-dispersed tree species are among the most threatened. Seed source is an important factor for active conservation and restoration efforts for such species but many studies show lower germination levels for seeds collected from small fragments compared to larger forests. However, the increasing rarity of large forests makes them difficult to be used as practical seed sources. We assessed the potential of small to medium-sized fragments (19–209 ha) to serve as seed sources for the conservation and restoration of an animal-dispersed tree Lacistema aggregatum (Lacistemataceae) in Costa Rican premontane wet forests. Germination, seedling survivorship, and growth for 2 years were quantified in a screen house environment. Two years later, more rigorous germination tests were conducted. Germination levels differed substantially among source trees. Seeds from some individuals had no germination inter-annually, suggesting that fecundity alone may be an incomplete indicator of individual fitness. Furthermore, in contrast to many previous studies, germination was better for seeds from smaller fragments for both study years. Subsequent seedling survivorship did not counteract the trends generated by germination, and the better performance of seeds from smaller fragments was retained for 2 years as ex situ seedlings. Higher seed quality in smaller fragments was associated with larger seed size in trees near forest edges, which might result from higher potential outcrossing rates. Our results suggest a previously unrecognized potential of small fragments as seed sources.     

The tree Cedrela odorata (Meliaceae): a morphologically subdivided species in Costa Rica

In Latin America. Cedrela odorata is a wide ranging species that occurs in several environments, where it shows significant morphological variation. A common garden experiment was established with seedlings from 63 families of ten populations from two habitat types (mesic and dry), distributed throughout Costa Rica, to examine the relationships between quantitative variation and site of population origin. Seedlings from dry areas tended to be distinct from those from mesic areas, with climatic grouping of provenance explaining a mean of 52% of the total variance and 80% of the genetic variance. Cluster analysis for seedling traits showed two natural groupings of families, which corresponded for the most part with the regional population groupings into mesic (Atlantic and South Pacific) and dry (North Pacific) groups. Cluster analysis based on seed weight and size also separated populations into mesic and dry climatic groups. Seeds from populations in dry areas were 43% heavier, and seedlings were 61% taller, 117% greater in diameter, and with leaflets 39% longer and 81% wider. These differences may be related to fast growth in the dry zone for taking advantage of early life cycle moisture availability. These findings may indicate incipient speciation in C. odorata in Costa Rica. Evaluation of reproductive isolating mechanisms between populations from the mesic and dry zones, and of clines at potential zones of hybridization would assist in testing a speciation hypothesis.     

Reproductive biology of the dry forest tree Enterolobium cyclocarpum (guanacaste) in Costa Rica: a comparison between trees left in pastures and trees in continuous forest

We compared the rate of pollen deposition, the likelihood of fruit production, the number of seeds per fruit, the outcrossing rate, and the progeny vigor of the tropical dry forest tree Enterolobium cyclocarpum for individuals in pastures vs. individuals in continuous forest. We found that flowers from trees growing in continuous forests were more likely to have pollen deposited on their stigmas than flowers from trees in pastures (52.1 vs. 32.3%, respectively). We also found that trees from continuous forests were almost six times more likely to set fruits and produce more seeds per fruit than trees in pastures. Morever, progeny from trees in continuous forests were, on average, more vigorous than the progeny from trees in pastures, as indicated by 12 of 16 indicators of plant vigor. However, there was no significant difference in the multilocus estimate of the outcrossing rate between the two groups of trees (tm = 1.00 and 0.99 for trees from continuous forest and trees from pastures, respectively). But there are differences in the correlation of paternity between the progeny of the two groups, where the progeny from trees in pastures showed a lower correlation of paternity than progeny of trees from continuous forests (r(p) = 0.104 and r(p) = 0.189, respectively). We argue that the mechanisms that regulate progeny vigor are disrupted in trees from pastures. We discuss the implications of these findings for the conservation of E. cyclocarpum.     

Fine-scale genetic population structure of an understory rainforest bird in Costa Rica

We studied five populations of a rainforest understory insectivorous bird (Myrmeciza exsul, chestnut-backed antbird) in a fragmented landscape in northeastern Costa Rica in order to test hypotheses about the influence of forest fragmentation on population genetic structure using 16 microsatellite loci. Bayesian assignment approaches—perhaps the most conservative analyses we performed—consistently grouped the sites into two distinct groups, with all individuals from the smallest and most isolated population clustering separately from the other four sites. Additional analyses revealed (1) overall significant genetic structure; (2) a pattern of population differentiation consistent with a hypothesis of isolation by resistance (landscape connectivity), but not distance; and (3) relatively short dispersal distances indicated by elevated mean pairwise relatedness in several of the sites. Our results are somewhat surprising given the small geographic distances between sites (11–34?km) and the short time (~60?years) since wide-spread deforestation in this landscape. We suspect fine-scale genetic structure may occur in many resident tropical bird species, and in the case of the chestnut-backed antbird it appears that anthropogenic habitat fragmentation has important population genetic implications. It appears that chestnut-backed antbirds may persist in fragmented landscapes in the absence of significant migration among patches, but mechanisms that allow this species to persist when many other similar species do not are not well understood.     

Notes on the ecology of rolled-leaf hispines (Chrysomelidae,Cassidinae) at La Gamba (Costa Rica)

A total of 301 adult hispine beetles of the genera Cephaloleia and Chelobasis were found in rolled leaves of plants of 17 species of Zingiberales (families Costaceae, Heliconiaceae, Maranthaceae, Musaceae, and Zingiberaceae) during a field study at La Gamba, Golfito region, Costa Rica. Of these beetles, Cephaloleia belti was recorded from 12 potential host plant species, C. distincta from 7, C. dilaticollis from 5, C., Chelobasis bicolor, C. championi, and C. histrionica from 3, Chelobasis perplexa and C. instabilis from 2, whereas C. trivittata from only one. Of the plant species, Heliconia latispatha had 7 beetle species in its leaf rolls, Calathea lutea had 5, H. imbricata and H. rostrata had 4, H. stricta and Musa paradisiaca had 3, H. wagneriana had 2, while on H. vaginalis, H. danielsiana, H. densiflora, H. longiflora, Calathea crotalifera, C. platystachya, Goeppertia lasiophylla, Alpinia purpurata, Costus pulverulentus and Costus barbatus, H. densiflora, H. vaginalis, and H. danielsana only hispines of one species were found.Cephaloleia belti occurred together with beetles of six other hispine species, whereas Cephaloleia trivittata never shared a leaf roll with another hispine species. The remaining beetle species aggregated with one to four other hispines. Adults of C. belti and C. championi were frequently seen, occasionally also with C. dilaticollis, C. histrionica, and Chelobasis perplexa, to co-occur with the carabid Calophaena ligata in the same leaf roll without any sign of interspecific aggression.A comparison of host choices and the phylogeny of the hispines and of their host plants revealed no signs that beetles used species level phylogenetic relationships within the Zingiberales to select food plants. Obviously, within this plant order, rolled-leaf hispines choose their plant hosts in a nearly opportunistic manner. Seemingly, they use differences among plants at higher taxonomic levels but within the Zingiberales, the availability of young – rolled – leaves might be the actual decisive factor.     

Floristic composition and structure of a premontane moist forest in Central Valley of Costa Rica]

The floristic composition and structure of a premontane moist forest remnant were studied in the El Rodeo Protected Zone, Central Valley of Costa Rica. Three one-hectare plots were established in the non-disturbed forest, and all trees with a diameter at breast height (dbh) of 10 cm or greater were marked, measured and identified. The plots were located within a radius of 500 m from each other. A total of 106 tree species were recorded in the three plots. Average values: species richness 69.6 species ha-1, abundance 509 individuals ha-1, basal area 36.35 m2 ha-1. Total diversity was 3.54 (Shannon Index, H'), and the species similarity among the plots ranged between S = 0.68 and 0.70 (S?rensen Similarity Index). Most tree species are represented by few individuals (five or less). There is a lack of emergent trees and arborescent palms in the forest canopy. According to the Familial Importance Value, Moraceae, followed by Fabaceae, Lauraceae, and Sapotaceae, largely dominates this forest. Pseudolmedia oxyphillaria (Moraceae) is the dominant species (Importance Value Index), accounting for 25% of all the marked trees in the plots, followed by Clarisia racemosa (Moraceae), Heisteria concinna (Olacaceae), and Brosimum alicastrum (Moraceae). The size class distributions were similar among plots, and in general followed the expected J-inverted shape. Differences in tree abundance, floristic composition, and spatial distribution of some species among the plots suggest heterogeneity of this ecosystem's arborescent vegetation. Moreover, it is an important natural reservoir for the conservation of rare and endangered tree species in a national level. Using these results as a baseline, this study should start a long term monitoring of the structure and composition of this very reduced and fragmented ecosystem.     

The genus Neotherina Dognin (Geometridae, Ennominae) in Costa Rica

So far, two species of Neotherina Dognin have been recorded in Costa Rica. Neotherina imperilla (Dognin) occurs primarily at altitudes between 1100 and 1700 meters and Neotherina callas (Druce) which is widely distributed above 1100 meters. A third, new species, Neotherina xanthosa Sullivan and Chacón is described from altitudes above 2400 meters. Heterogeneity of the genus is discussed.