American Tropics Research Articles

Synchronous precipitation reduction in the American Tropics associated with Heinrich 2

During the last ice age temperature in the North Atlantic oscillated in cycles known as Dansgaard-Oeschger (D-O) events. The magnitude of Caribbean hydroclimate change associated with D-O variability and particularly with stadial intervals, remains poorly constrained by paleoclimate records. We present a 3.3 thousand-year long stalagmite δ18O record from the Yucatan Peninsula (YP) that spans the interval between 26.5 and 23.2 thousand years before present. We estimate quantitative precipitation variability and the high resolution and dating accuracy of this record allow us to investigate how rainfall in the region responds to D-O events. Quantitative precipitation estimates are based on observed regional amount effect variability, last glacial paleotemperature records, and estimates of the last glacial oxygen isotopic composition of precipitation based on global circulation models (GCMs). The new precipitation record suggests significant low latitude hydrological responses to internal modes of climate variability and supports a role of Caribbean hydroclimate in helping Atlantic Meridional Overturning Circulation recovery during D-O events. Significant in-phase precipitation reduction across the equator in the tropical Americas associated with Heinrich event 2 is suggested by available speleothem oxygen isotope records.

Los sorprendentes murciélagos: ¿Amigos, enemigos o aliados?

Los murciélagos son un grupo de vertebrados extraordinariamente especializados y son los únicos mamíferos capaces de volar; sus hábitos nocturnos los han estigmatizado hasta tal punto que en las producciones cinematográficas de Hollywood se consideró al Conde Drácula de los Montes Cárpatos como el primer hombre vampiro; incluso antes que el propio Batman. En los ecosistemas, los murciélagos son actores con roles protagónicos, el 70% de ellos son insectívoros, polinizadores, frugívoros, contribuyen a la regeneración de los bosques mediante la diseminación de semillas y algunos son cazadores de peces. Aunque su gran población se distribuye principalmente en los trópicos, son cosmopolitas y también se encuentran en el hemisferio norte. La población de estos murciélagos ha sido desplazada en los trópicos sudamericanos, debido, entre muchos factores, a la minería ilegal, la fumigación de pesticidas, la deforestación indiscriminada para proporcionar pastizales al ganado, así como la invasión de sus hábitats por los humanos (1).

Finding needles in the haystack: where to look for rare species in the American tropics

Tropical America (the Neotropics) harbours more plant species than any other region on Earth. The contribution of rare species to this diversity has been recently recognised, but their spatial distribution remains poorly understood. Here, we use all collection records of angiosperms from the Global Biodiversity Information Facility to delineate Neotropical bioregions, and to identify putatively rare species within the Neotropics and the Amazonian rainforest. We analyse the spatial distribution of these species and validate the results on a largely independent dataset based on vegetation plots from the Amazon Tree Diversity Network. We find that rare species are homogeneously distributed through most parts of the lowland Neotropics and Amazonia, but more concentrated in highlands. The second collection of any rare species is most often found in the close vicinity of the first, but in 20% of cases they are more than 580 km apart. We also find cross‐taxonomic patterns of disjunct distributions within the Andes, the Atlantic forest in eastern Brazil, and between Amazonia and the Atlantic forest, but no clear disjunction patterns within lowland areas. These results suggest that a considerable proportion of rare plant species have surprisingly large distribution ranges, and that collections of rare species across most of the lowland Neotropics, and in particular in Amazonia, show no clear directionality. The second record of many rare species may be found virtually anywhere, urging the need for intensifying and broadening biological sampling.

Aedeomyia squamipennis (Diptera: Culicidae) in Florida, USA, a New State and Country Record.

Aedeomyia squamipennis (Lynch Arribalzaga) is a tropical mosquito (Diptera: Culicidae) found throughout most of the American Tropics, from eastern Mexico through Argentina, including several Caribbean islands. Larvae are typically associated with bodies of water with dense growths of aquatic vegetation, particularly Pistia stratiotes L., water lettuce. Adult females feed predominantly on the blood of birds and seek hosts in forest canopies. Aedeomyia squamipennis is considered an important vector of Gamboa virus and avian malaria, and is also suspected of transmitting Venezuelan equine encephalitis virus. Collections from Florida City, FL, near the southern tip of the Florida peninsula, yielded larvae, adult males, and females of Ad. squamipennis, constituting a new genus and species record for Florida and the United States. The widespread availability of larval habitat and suitable hosts in Florida will likely lead to expansion of Ad. squamipennis in Florida, and perhaps into neighboring states. In South America, Ad. squamipennis is found as far south as Buenos Aires, Argentina, at ∼35° S latitude, which is equivalent in N latitude to coastal North Carolina. The northern limit of expansion of Ad. squamipennis in North America will likely be limited by winter temperatures and availability of larval habitat.

Guava: phytochemical composition of a potential source of antioxidants for cosmetic and/or dermatological applications

Guava (Psidium guajava L.) is a native fruit of the American tropics with commercial applications for its taste, flavor and aroma. Numerous pharmacological uses have been described for it, such as the antiseptic effect of its leaves, the use of the fresh fruit and tea from its leaves for the treatment of diarrhea, dysentery, diabetes mellitus, and others. However, considering its rich composition, the guava also is a potential source of antioxidants to be used in the development of new formulations for cosmetic and/or dermatological applications, the main focus of this research. Herein, we describe the study of the phytochemical composition and the antioxidant activity of a guava extract prepared with non-toxic solvents aiming its use at biological applications. High performance liquid chromatography and mass spectrometry were employed to identify the major components, while thermoanalytical measurements and hot stage microscopy were used to assess the chemical stability of guava fruit extract. The antioxidant activity was also evaluated assessing the SOD-like activity and ABTS free radical scavenger. The results show that the extract is a rich source of phenolic compounds, such as quercetin, kaempferol, schottenol, among many others. All of the components found in guava extract exhibit biological effects according to the literature data, mainly antioxidant properties.

Observations on the biology of the hermit crab, Coenobita compressus H. Milne Edwards (Decapoda; Anomura) on the west coast of the Americas

The semi-terrestrial hermit crab, Coenobita compressus , is one of the most conspicuous supra-littoral invertebrates on the west coast of the American tropics.

A climatic risk analysis of the threat posed by the South American leaf blight (SALB) pathogen Microcyclus ulei to major rubber producing countries

South American leaf blight (SALB) of the Para rubber tree, Hevea brasiliensis Muell. Arg., caused by the plant pathogenic fungus Microcyclus ulei (Henn.) Arx, is recognized as the most serious threat to the natural-rubber industry worldwide. While the pathogen is currently restricted to South America, the warm humid climatic conditions in Asia and Africa, which contribute to over 97 % of world’s natural rubber production are similar to the South American tropics, indicating a significant threat to global rubber production, should the pathogen be introduced to these regions. The present study aims to assess climate suitability for the occurrence of M. ulei in different parts of the world, based on the available literature for M. ulei pathogen establishment, including temperature, relative humidity and precipitation. The risk analysis study provides a preliminary indication of the likely threat of M. ulei in different rubber growing areas of the world and highlights the need for more information on pathogen biology, diversity and environmental tolerance.

Diversity in neotropical dry forests

Forest Ecology Dry forests in the American tropics are not as extensive as rain forests and are more severely threatened by human activity. The DRYFLOR network compiled a floristic inventory of the entire neotropical dry forest biome and used this database of nearly 5000 woody species to analyze the geographical distribution of plant diversity that it hosts. Large variation in floristic composition between different sites and regions implies that effective conservation of dry forest plant diversity will require the protection of numerous priority areas across neotropical nations. Science , this issue p. [1383][1] [1]: /lookup/doi/10.1126/science.aaf5080

The nest architecture of stingless bees with special reference to those of Costa Rica (Hymenoptera, Apidae)

The purpose of this work is to provide comparative information on the nest sites and architecture of the whole apid tribe Meliponini as well as data on the hitherto undescribed nests of certain species from Costa Rica. The field work involved opening limited numbers of nests of as many species as possible and recording the nest structure and organization by means of notes, diagrams, and photographs. We have not attempted the detailed kind of examination of architecture such as Nogueira-Neto's (40) study of cells, for such investigations are best done with colonies in hives. Qur interest has been in the field conditions and architectural adaptations to various kinds of cavities.The stingless bees are the most common bees and possibly the most important pollinators in the American tropics. They are less numerous in the African, Asiatic and Australian tropics but nonetheless are a significant element of the fauna, especially in the Malayan area. They are also sources of minor quantities of honey and wax. In addition to their major positive value as pollinators, sorne of them are significant pests. Various species cut leaves, buds, and bark of young trees, causing significant lesses to agriculture and horticulture, and transmit certain plant diseases.

Die Neuordnung pflanzengeografischen Wissens als „Transitzone“ Wallacea. Ein amerikanisches Expansionsprojekt auf den Philippinen, 1902–1928

The Reshaping of Phytogeographical Knowledge as the "Transition zone" Wallacea: An American Expansion Project in the Philippines, 1902-1928. This paper examines the development of a concept that to this day plays an important role in biogeography: the region Wallacea. Focussing on the work of the American tropical botanist Elmer D. Merrill in the Philippines, I argue that his research on the geographical movement and settlement of Philippine plants reflects a shift in the United States' scientific and cultural understanding of the Pacific area towards a notion of "American tropics". While inventorying plants for the American administration from 1901 to 1923, the composition of Philippine flora prompted Merrill to question biogeographical regionalization in Wallace's Malay Archipelago. Not being able to situate the Philippine flora within "Asian" or "Australasian" biota, Merrill described the islands as an area of trans-regional plant migration. Together with the paleontologist Roy E. Dickerson, he later conceptualized the region Wallacea as biogeographical "transition zone" between the Philippines and Australia. In addition to the scientific conceptualization, Wallacea constitutes a space between two biogeographical subregions, whose flora was considered as being part of both, but could not be unambiguously attributed to either of these regions. In this respect, the plants resembled the inhabitants of the United States' insular overseas territories, who were legally defined neither as aliens nor as citizens. In this sense, Wallacea embodies epistemic as well as geopolitical boundaries, while its case also illustrates some of the ways in which colonial interests in the usability of plants found expression in botanical research during the early period of American overseas expansion.

Fossil Cetaceans (Mammalia, Cetacea) from the Neogene of Colombia and Venezuela

There are significant geographic gaps in our knowledge of marine mammal evolution because most fossils have been found and described from Northern Hemisphere localities and a few other high-latitude areas in the Southern Hemisphere. Here, we describe fossil cetacean remains from five geological units in the South American tropics (Urumaco, Codore, Castilletes, Cantaure, and Querales formations) generally representing marginal marine depositional environments (estuaries, deltas, and tidal flats). While fossil cetaceans from Venezuelan Neogene localities have been previously studied, this paper includes the first descriptions of fossil cetaceans from Colombia, including a diverse assemblage of mysticetes and odontocetes. We identified and provisionally referred fragmentary remains to the iniid Ischyrorhynchus vanbenedeni and to the platanistid Zarhachis flagellator. The latter suggests the presence of Platanistidae in the eastern coast of South America during the early-middle Miocene, representing the second record of Platanistidae in South America and the first record of Platanistidae in eastern South America. Other less-diagnostic specimens are characterized by features commonly seen in longirostrine odontocetes such as Iniidae, Platanistidae, Pontoporiidae, Lipotidae, Eoplatanistidae, and Squalodelphinidae.

¿Cambio climático o variabilidad climática? Historia, ciencia y política en el clima mesoamericano

Las variaciones en el clima de Mesoamérica han influenciado el desarrollo y decaimiento de las poblaciones desde los primeros asentamientos humanos. La época actual no es la excepción; sin embargo, no se tienen evidencias de que el calentamiento global impactará las precipitaciones en la región, sino que más bien hay estudios importantes que muestran que los cambios en las lluvias responden más bien a la variabilidad climática que actualmente sufre el trópico americano.Debido a que nuestra región tropical es vulnerable a la variabilidad del clima, las políticas públicas deben ser congruentes para evitar los errores de generaciones previas y lograr, de la mano de la ciencia, un verdadero avance en la lucha contra el calentamiento global.

An assessment of Schinopsis brasiliensis Engler (Anacardiacea) for dendroclimatological applications in the tropical Cerrado and Chaco forests, Bolivia

Given the scarcity of instrumental climatic data in the South American tropics, it is valuable to explore the dendrochronological potential of the numerous tree species growing in the region. In this paper, we assessed for the first time the dendrochronological characteristics of Schinopsis brasiliensis, an arboreal species from the dry-tropical Cerrado and Chaco forests in Bolivia and adjacent countries. Similar to most woody species in the Cerrado and Chaco regions, growth rings of S. brasiliensis are delimited by the presence of thin but continuous lines of marginal parenchyma. Based on 22 samples from 15 trees, we present the first ring-width chronology for this species covering the period 1812–2011 (200 years). Additionally, a 106-year floating chronology from S. brasiliensis was developed using cores from four columns from the church of San Miguel, Santa Cruz, built in the period 1720–1740. Standard dendrochronological statistics indicate an important common signal in the radial growth of S. brasiliensis. The comparison of variations in regional climate and ring widths shows that tree growth is directly related to spring-summer rainfall and inversely related to temperature. Following the winter dry season, rainfall in late spring and early summer increases soil water supply, which activates tree growth. In contrast, above-average temperatures during the same period increase evapotranspiration, intensify the water deficit and reduce radial growth. The dependence of S. brasiliensis growth on water supply is evidence of its dendrochronological potential for reconstructing past precipitation variations in the extensive tropical Cerrado and Chaco forest formations in South America. Using wood from historical buildings opens the possibility of extending the chronologies of S. brasiliensis over the past 400–500 years.

Murciélagos (Chiroptera) del departamento del Chocó, occidente colombiano

Due to its location on the northwestern corner of the subcontinent, considered epicenter of the great inter- change of biota between North and South America, the department of Choco represents one of the most important terrestrial and aquatic environments in terms of biodiversity in the American tropics. In addition, the entire area of the department is part of in the Biogeographic Choco, which corresponds to a large proportion of conservation corridor Choco-Manabi, hotspot of biodiversity, as well as the Terrestrial Ecore- gion Priority (ETP) Tumbes-Choco-Magdalena. It has been documented, that chiropterans constitute one of the most important components of such diversity. Although there are many e orts that compile the chiropterological information of the department, important advances on the documentation of this group of mammals for the region make urgent a constant evaluation of the bat diversity for the department. On this line of ideas, we present an updated list of bats for the department of Choco, which include species that have been reported in national lists and are represented in scienti c collections of national and international institutions. We report a total of 132 Chocoan bat species, corresponding to 64,4% of the chiropteranfau-na of Colombia. Among this diversity there are six species considered at risk threat (IUCN). This diversity is grouped into 59 genera, seven families and 12 subfamilies. This study increases the Chocoan richness of bats in 49%, going from 83 to 132 species. This results position the Choco as the department with the highest number of species of bats in the country, and one of the areas with the greatest bat diversity in the hemisphere. The subregion with the highest species richness in the department was Atrato with 82 species and the municipality with the highest number recorded species was Quibdo with 72 species. However, our analyses suggest a high biotic potential for the region, and at the same time, point out on the scarcity of studies and knowledge and the poor geographic coverage of diversity inventories; a serious situation if we consider the multiple and constant human pressures on nature in this portion of the country. Habitat fragmentation caused by di erent human activities (agriculture, cattle, and mining) as well as hunting are some of the most relevant anthropogenic pressures. In this scenario, it is evident the need for further research in the department, involving taxonomic and eco- logical aspects, which contribute to a better understanding of this group and provide useful tools for the conservation of bats in northwestern Colombia.

Investigación en jícama (Pachyrhizus erosus) y su potencial para el desarrollo agrícola de la Región.

The yam bean (Pachyrhizus erosus) is an excellent alternative crop for the agricultural diversification in the American tropics, because the tuberous roots can be used as food and natural insecticides are produced with the rotenone extracted from the seeds. The main object of this trial was to submit the latest research findings obtained from the testing of new yam bean genotypes, under different environments in Costa Rica. Three experiments were established during April and July of 1993: 10 genotypes were evaluated at two localities, Alajuela and Turrialba, in the first two trials. The third trial conducted in Turrialba consisted of planting distances (0.10,0.15 and 0.20 m between plants. As a whole, there is a marked tendency with respect to the locality, as it was proven in consecutive trials that Alajuela is the most appropiated zone for growing yam bean. With reference to planting distances, the preliminary results suggest that at shorter distances, the larger the root production and the lower their weight. The yam bean offers an alternative to be considered for the agricultural development of the region because of itsadaptation within the farmers', systems, improving the food sustainability.

Carbon sequestration potential of second-growth forest regeneration in the Latin American tropics.

Regrowth of tropical secondary forests following complete or nearly complete removal of forest vegetation actively stores carbon in aboveground biomass, partially counterbalancing carbon emissions from deforestation, forest degradation, burning of fossil fuels, and other anthropogenic sources. We estimate the age and spatial extent of lowland second-growth forests in the Latin American tropics and model their potential aboveground carbon accumulation over four decades. Our model shows that, in 2008, second-growth forests (1 to 60 years old) covered 2.4 million km(2) of land (28.1% of the total study area). Over 40 years, these lands can potentially accumulate a total aboveground carbon stock of 8.48 Pg C (petagrams of carbon) in aboveground biomass via low-cost natural regeneration or assisted regeneration, corresponding to a total CO2 sequestration of 31.09 Pg CO2. This total is equivalent to carbon emissions from fossil fuel use and industrial processes in all of Latin America and the Caribbean from 1993 to 2014. Ten countries account for 95% of this carbon storage potential, led by Brazil, Colombia, Mexico, and Venezuela. We model future land-use scenarios to guide national carbon mitigation policies. Permitting natural regeneration on 40% of lowland pastures potentially stores an additional 2.0 Pg C over 40 years. Our study provides information and maps to guide national-level forest-based carbon mitigation plans on the basis of estimated rates of natural regeneration and pasture abandonment. Coupled with avoided deforestation and sustainable forest management, natural regeneration of second-growth forests provides a low-cost mechanism that yields a high carbon sequestration potential with multiple benefits for biodiversity and ecosystem services.

Olympic Games Rio 2016 and the uninvited viruses: Potential consequences for Europe and North America

In the Latin American tropics, we have witnessed the emergence of several pathogenic arboviruses in the last decade. These include Yellow Fever, West Nile virus, St. Louis encephalitis, Venezuelan equine encephalitis, Mayaro, Oropouche, Ilheus, and most recently, Chikungunya and Zika. Guillain-Barre syndrome (GBS), microcephaly and all the encephalitides, have been of concern to public health officials in Latin America since the arrival of emerging arboviruses. ¡Don‘t forget about dengue! Between 2014 and 2015 we received two unexpected and uninvited viruses: Chikungunya and Zika. Chikungunya, an alphavirus, appeared abruptly in developing countries of the Americas, revealing that we were not prepared to face it. While we were still recovering from Chikungunya, Zika virus arrived, only compounding the insult. One cannot imagine the potential impact of the introduction of a hemorrhagic virus of the likes of Marburg or Ebola in Latin America. This scenario would be catastrophic.

Vittaria appalachiana continues to provide insight into the biology of ferns: A commentary on two studies recently published in American Journal of Botany.

Vittaria appalachiana continues to provide insight into the biology of ferns: A commentary on two studies recently published in American Journal of Botany.

The metareticulate pollen morphology of Alternanthera Forssk. (Gomphrenoideae, Amaranthaceae) and its taxonomic implications

Alternanthera (Amaranthaceae) is a diverse genus largely restricted to the American Tropics that belongs to the alternantheroid clade containing C4 and C3–C4 intermediate species. This research focuses on the study of pollen characters by studying 13 species, representatives of the two major clades and subclades of Alternanthera. General palynological comparisons were conducted with light microscopy (LM), scanning electron microscopy (SEM) and with confocal laser scanning microscopy (CLSM) for exine ultrastructure. Twenty-five characters were measured and described for Alternanthera and among these, 14 pollen characters were used to discriminate pollen groups using cluster analysis and canonical analysis of principal coordinates (CAP). Pollen form and ornamentation, pores number, spines length, number of ektexinous bodies and nanospines on the ektexinous bodies on pore membranes, arrangement of nanopores and spines on structural elements, and metareticula form were taxonomically important and therefore used to construct the first palynological key to the alternantheroid clade species. Our study indicates that the seemingly subtle morphological variation of pollen is useful for recognising three main pollen types within Alternanthera. The much needed palynological terminology for describing the mesoporium in the metareticulate pollen of Amaranthaceae is provided.

Ariel’s Ecology: Plantations, Personhood, and Colonialism in the American Tropics by Monique Allewaert (review)

Ariel’s Ecology: Plantations, Personhood, and Colonialism in the American Tropics by Monique Allewaert (review)