Climate as a driver of tropical insular diversity: comparative phylogeography of two ecologically distinctive frogs in Puerto Rico

The effects of late Quaternary climate on distributions and evolutionary dynamics of insular species are poorly understood in most tropical archipelagoes. We used ecological niche models under past and current climate to derive hypotheses regarding how stable climatic conditions shaped genetic diversity in two ecologically distinctive frogs in Puerto Rico. Whereas the mountain coquí Eleutherodactylus portoricensis is restricted to montane forest in the Cayey and Luquillo Mountains, the red‐eyed coquí E. antillensis is a habitat generalist distributed across the entire Puerto Rican Bank (Puerto Rico and the Virgin Islands, excluding St Croix). To test our hypotheses, we conducted phylogeographic and population genetic analyses based on mitochondrial and nuclear loci of each species across their range in Puerto Rico. Patterns of population differentiation in E. portoricensis, but not in E. antillensis, supported our hypotheses. For E. portoricensis, these patterns include: individuals isolated by long‐term unsuitable climate in the Río Grande de Loíza Basin in eastern Puerto Rico belong to different genetic clusters; past and current climate strongly predicted genetic differentiation; and Cayey and Luquillo Mountains populations split prior to the last interglacial. For E. antillensis, these patterns include: genetic clusters did not fully correspond to predicted long‐term unsuitable climate; and past and current climate weakly predicted patterns of genetic differentiation. Genetic signatures in E. antillensis are consistent with a recent range expansion into western Puerto Rico, possibly resulting from climate change and anthropogenic influences. As predicted, regions with a large area of long‐term suitable climate were associated with higher genetic diversity in both species, suggesting larger and more stable populations. Finally, we discussed the implications of our findings for developing evidence‐based management decisions for E. portoricensis, a taxon of special concern. Our findings illustrate the role of persistent suitable climatic conditions in promoting the persistence and diversification of tropical island organisms.     

DNA barcoding and community assembly—A simple solution to a complex problem

Identifying the current and past processes driving community assembly is critical in the effort to understand the Earth's biodiversity and its response to future environmental change. But while studies on community assembly often emphasize the role of contemporary ecological drivers, it has been particularly challenging to account for the effects of past processes in shaping present‐day communities. In this issue of Molecular Ecology, Hao et al. (2020) provide a holistic analysis of factors driving the assembly of diverse communities of Lepidoptera in two mountain ranges in northeastern China. The authors use an impressively large data set and exceptionally comprehensive analyses to test how processes of range expansion and gene flow, speciation and extinction, dispersal limitation, environmental filtering and competition have led to present‐day diversity patterns. A key novelty of this work is the exhaustive use of DNA barcodes, relatively simple yet powerful molecular markers, to tackle complex biological questions. The authors elegantly show the utility of DNA barcoding data for research beyond simple taxonomic assignment. Their approach is remarkable as it manages to integrate population genetics, phylogenetic history, species diversity and ecology into a well‐rounded picture of community assembly. With this work, Hao et al. demonstrate the great promise of DNA barcoding for exhaustive community analysis of even highly diverse and complex systems, raising the bar for future research.     

Trends and scenarios of the carbon budget in postagricultural Puerto Rico (1936–2060)

Contrary to the general trend in the tropics, Puerto Rico underwent a process of agriculture abandonment during the second half of the 20th century as a consequence of socioeconomic changes toward urbanization and industrialization. Using data on land‐use change, biomass accumulation in secondary forests, and ratios between gross domestic product (GDP) and carbon emissions, we developed a model of the carbon budget for Puerto Rico between 1936 and 2060. As a consequence of land abandonment, forests have expanded rapidly since 1950, achieving the highest sequestration rates between 1980 and 1990. Regardless of future scenarios of demography and land use, sequestration rates will decrease in the future because biomass accumulation decreases with forest age and there is little agricultural land remaining to be abandoned. Due to high per‐capita consumption and population density, carbon emissions of Puerto Rico have increased dramatically and exceeded carbon sequestration during the second half of the 20th century. Although Puerto Rico had the highest percent of reforestation for a tropical country, emissions during the period 1950–2000 were approximately 3.5 times higher than sequestration, and current annual emission is almost nine times the rate of sequestration. Additionally, while sequestration will decrease over the next six decades, current socioeconomic trends suggest increasing emissions unless there are significant changes in energy technology or consumption patterns. In conclusion, socioeconomic changes leading to urbanization and industrialization in tropical countries may promote high rates of carbon sequestration during the decades following land abandonment. Initial high rates of carbon sequestration can balance emissions of developing countries with low emission/GDP ratio. In Puerto Rico, the socioeconomic changes that promoted reforestation also promoted high‐energy consumption, and resulted in a net increase in carbon emissions.     

A revision of the Puerto Rican species of lepanthes (Orchidaceae)

Six species of the orchid speciesLepanthes are described as new. A seventh species,L. sanguined, previously known only from Jamaica, is reported from Puerto Rico. The current misspelling ofL. selenitepala, the only species of the genus previously reported from Puerto Rico, is corrected. A key to the eight Puerto Rican species ofLepanthes is presented, and the value of several interesting taxonomic characters is discussed. The possibility of apogamy in this genus is raised, and detailed biosystematic investigations are indicated as necessary for a complete understanding of the group.     

Genetic diversity of naturalized cacao (<Emphasis Type="Italic">Theobroma cacao</Emphasis> L.) in Puerto Rico

Identification of genetically diverse cacao with disease resistance, high productivity, and desirable organoleptic traits is vitally important to the agricultural crop’s long-term sustainability. Environmental changes, pests, and diseases as well as nation’s sovereign property rights have led to a decrease in accessibility and exchange of germplasm of interest. Having been introduced during colonial times, naturalized cacao in Puerto Rico could serve as an unexplored source of genetic diversity in improvement programs. An island-wide survey was carried out to identify naturalized trees and to determine their genetic associations to reference cacao accessions. Samples were genotyped with Expressed Sequence Tag-derived single nucleotide polymorphism (SNP) markers. Principal coordinate, cluster, and population structure analysis using the genotype data for both local and reference samples assigned individuals into five distinct genetic backgrounds: Criollo, Trinitario, Amelonado, Upper Amazon Forastero (UAF), and Nacional. Puerto Rican cacao fit into four (Criollo, Trinitario, Amelonado and UAF) of the five genetic backgrounds, being mainly composed of individuals of Criollo ancestry. Based on historical evidence, cacao of Criollo background was probably brought to Puerto Rico from Venezuela and/or Central America during colonial times. Trinitario, Amelonado, and UAF genetic backgrounds are most likely products of more modern introductions. Genotyping cacao in Puerto Rico provides information on the history and possible origin of the naturalized trees on the island. In addition, the assessment has allowed the targeting of material for incorporation and long-term conservation filling gaps in the existing collection and providing new germplasm to be evaluated for agronomic performance.     

全球气候变化对农业生态系统的影响研究进展

全球大气中CO2浓度升高、气温升高及降水量的变化等是全球气候变化对农业生产和农业生态系统影响最为重要的几个生态因子,其影响主要表现在对农作物产量、生长发育、病虫害、农业水资源及农业生态系统结构和功能等方面.在过去的几十年,全球气候变化已对我国农业和农业生态系统,特别是我国北方旱区农业造成重大影响,其中不少影响是负面的或不利的.本文综述了全球气候变化对农业水资源、农田土壤养分变化、农作物生长发育、农作物病虫害与杂草、粮食安全及农业生态系统的结构和功能等方面的影响.针对21世纪全球气候变化对我国农业生产和农业生态系统带来的挑战,探讨了今后研究的重点和难点问题.     

农田景观格局对害虫天敌生态控害功能的调控作用

如何提升农田景观的生态服务功能是当前景观生态学和害虫防治学的前沿研究热点.基于区域农田景观格局可显著调节植物-植食性昆虫-天敌之间相互关系的理论基础,本文系统概括总结了农田景观格局及其变化对农田重要天敌多样性与生态控害功能的影响.从不同天敌类群的角度,分析了农田景观格局对捕食性天敌、寄生性天敌、有益微生物及其生态控害功能的调控作用.同时,对优化农田景观作物布局、采取合理的植被生境管理策略进行了展望.本文可为应用植被生境管理提升农田景观中天敌的生态系统服务功能提供参考,进一步促进区域生态农业响应"化学农药减量施用"的战略目标提供理论支撑.     

Altered climate leads to positive density‐dependent feedbacks in a tropical wet forest

Climate change is predicted to result in warmer and drier Neotropical forests relative to current conditions. Negative density‐dependent feedbacks, mediated by natural enemies, are key to maintaining the high diversity of tree species found in the tropics, yet we have little understanding of how projected changes in climate are likely to affect these critical controls. Over 3 years, we evaluated the effects of a natural drought and in situ experimental warming on density‐dependent feedbacks on seedling demography in a wet tropical forest in Puerto Rico. In the +4°C warming treatment, we found that seedling survival increased with increasing density of the same species (conspecific). These positive density‐dependent feedbacks were not associated with a decrease in aboveground natural enemy pressure. If positive density‐dependent feedbacks are not transient, the diversity of tropical wet forests, which may rely on negative density dependence to drive diversity, could decline in a future warmer, drier world.     

Strong founder effects and low genetic diversity in introduced populations of Coqui frogs

The success of non-native species may depend on the genetic resources maintained through the invasion process. The Coqui ( Eleutherodactylus coqui ), a frog endemic to Puerto Rico, was introduced to Hawaii in the late 1980s via the horticulture trade, and has become an aggressive invader. To explore whether genetic diversity and population structure changed with the introduction, we assessed individuals from 15 populations across the Hawaiian Islands and 13 populations across Puerto Rico using six to nine polymorphic microsatellite loci and five dorsolateral colour patterns. Allelic richness ( R _T) and gene diversity were significantly higher in Puerto Rico than in Hawaii populations. Hawaii also had fewer colour patterns (two versus three to five per population) than Puerto Rico. We found no isolation by distance in the introduced range, even though it exists in the native range. Results suggest extensive mixing among frog populations across Hawaii, and that their spread has been facilitated by humans. Like previous research, our results suggest that Hawaiian Coquis were founded by individuals from sites around San Juan, but unlike previous research the colour pattern and molecular genetic data (nuclear and mtDNA) support two separate introductions, one on the island of Hawaii and one on Maui. Coquis are successful invaders in Hawaii despite the loss of genetic variation. Future introductions may increase genetic variation and potentially its range.     

The present and future effects of land use on ecological assemblages in tropical grasslands and savannas in Africa

The world is currently experiencing a period of rapid, human‐driven biodiversity loss. Over the past decade, numerous metrics for biodiversity have been used to create indicators to track change in biodiversity. However, our ability to predict future changes has been limited. In this study, we use two very different models to predict the status and possible futures for the composition and diversity of ecological assemblages in African tropical grasslands and savannas under land‐use change. We show that ecological assemblages are affected more by land use in African grasslands and savannas than in other biomes. We estimate that average losses of assemblage composition and diversity are already between 9.7 and 42.0%, depending on the model and measure used. If current socio‐economic trajectories continue (‘business‐as‐usual’), the likely associated land‐use changes are predicted to lead to a further 5.6–12.3% loss of assemblage composition and diversity. In contrast, a scenario that assumes more efficient use of agricultural areas (thus requiring a smaller total area) could be associated with a partial reversal ? of as much as 3.2% ? of past losses. While the agriculture that causes the majority of land‐use change is an important source of economic growth, projections of the effects of land use on ecological assemblages can allow for more informed decisions.     

Using historical ecology to understand patterns of biodiversity in fragmented agricultural landscapes

Aim To enhance current attempts to understand biodiversity patterns by using an historical ecology approach to highlight the over‐riding influence of land‐use history in creating past, current and future patterns of biodiversity in fragmented agricultural landscapes. Methods We develop an integrative conceptual framework for understanding spatial and temporal variations in landscape patterns in fragmented agricultural landscapes by presenting five postulates (hypotheses) which highlight the important role of historical, anthropogenic disturbance regimes. We then illustrate each of these postulates with examples drawn from fragmented woodlands in agricultural areas of south‐eastern Australia, and discuss these findings in an international context. Location examples are drawn from agricultural areas in south‐eastern Australia. Results We conclude that there is limited potential to refine our understanding of patterns of biodiversity in human‐modified landscapes based on traditional concepts of island biogeography, or simple assumptions of ongoing destruction and degradation. Instead, we propose that in agricultural landscapes that were largely cleared over a century ago: (1) present‐day remnant vegetation patterns are not accidental, but are logically arrayed due to historic land‐use decisions, (2) historic anthropogenic disturbances have a major influence on current ecosystem conditions and diversity patterns, and (3) the condition of remnant ecosystems is not necessarily deteriorating rapidly. Main conclusions An historical ecology approach can enhance our understanding of why different species and ecosystem states occur where they do, and can explain internal variations in ecological conditions within remnant ecosystems, too often casually attributed to the ‘mess of history’. This framework emphasizes temporal changes (both past and future) in biotic patterns and processes in fragmented agricultural landscapes. Integration of spatially and temporally explicit historical land‐use information into ecological studies can prove extremely useful to test hypotheses of the effects of changes in landscape processes, and to enhance future research, restoration and conservation management activities.     

A numerical analysis of arborescent communities in the rain forest of the Luquillo mountains,Puerto Rico

Summary Cluster analysis and canonical ordination were used as complementary techniques to identify major associations in a lower montane rain forest in Puerto Rico. These techniques were applied to forestry inventories from both secondary and primary communities. Eight major forest types were identified from the analyses and were confirmed by field checks. Distribution of these types was strongly correlated with past land-use and topographic position.Comprehensive ecological surveys are rare in moist tropical forests; however, forestry inventories are common and the results of this study suggest that valuable ecological information can be obtained from these data sets as well.Scientific Journal Series No. 10793 of the Minnesota Agricultural Experimental Station. Plant nomenclature according to Little & Wadworth (1964) and Little, Woodbury & Wadsworth (1974).This research was conducted while the senior author was stationed at the Institute of Tropical Forestry, USDA Forest Service, Rio Piedras, Puerto Rico.     

A historical and comparative review of 50 years of root data collection in Puerto Rico

Fine roots play an important role in plant nutrition, as well as in carbon, water, and nutrient cycling. Fine roots account for a third of terrestrial net primary production (NPP), and inclusion of their structure and function in global carbon models should improve predictions of ecosystem responses to climate change. However, studies focusing on underground plant components are much less frequent than those on aboveground structure. This is more marked in the tropics, where one-third of the planet's terrestrial NPP is produced. Some tropical forests have been more represented in the literature than others, as demonstrated in the collective studies in Puerto Rico. This Caribbean island's biodiversity, frequency of natural disturbances, ease of access to forests, and long-term plots have created an ideal place for the study of tropical ecological processes. This literature review emphasizes 50 years of root research and patterns revealed around Puerto Rico. The data in this review were compiled from scientific publications, conference reports, symposiums, and raw data shared by some researches. Emergent patterns include the shallow distribution of fine roots, the great variation in root biomass among different forest types, little variation in root phosphorus concentrations, the slow recovery of root biomass after Hurricane Hugo, and the fact that most data on roots come from the wet tropical Luquillo Experimental Forest, causing other habitat types to be underrepresented. This review also shows the gaps in knowledge about fine roots in the island's ecosystems, which should be used to promote and guide future studies.     

Invasion origin,rapid population expansion,and the lack of genetic structure of cotton bollworm (Helicoverpa armigera) in the Americas

In 2013, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) was officially declared as present in Brazil and, after two years, the species was detected in the Caribbean and North America. Information on genetic features and accurate distribution of pests is the basis for agricultural protection policies. Furthermore, such knowledge is imperative to develop control strategies, understand the geographical range, and genetic patterns of this species in the Americas. Here, we carried out the widest sampling of H. armigera in the South American continent and Puerto Rico, after we estimated the diversity, demographic parameters, and genetic structure. The Internal Transcribed Spacer 1 (ITS1) nuclear marker was used to investigate the presence of putative hybrids between H. armigera and H. zea, and they were observed at a frequency of 1.5%. An ABC analysis, based in COI gene fragment, suggested Europe as the origin of South America specimens of H. armigeraand following a movement northward through the Caribbean. Three mtDNA genes and three nDNA markers revealed high genetic diversity distributed without the defined population structure of H. armigera in South America. Most of the genetic variation is within populations with a multidirectional expansion of H. armigera among morphoclimatic regions. High genetic diversity, rapid population expansion, and hybridization have implications for pest management since they suggest that adaptive alleles are spread through wide areas in South America that favor rapid local adaptation of H. armigera to new and disturbed environments (e.g., in agricultural areas).     

Threshold responses of riverine fish communities to land use conversion across regions of the world

The growing human enterprise has sparked greater interest in identifying ecological thresholds in land use conversion beyond which populations or communities demonstrate abrupt nonlinear or substantive change in species composition. Such knowledge remains fundamental to understanding ecosystem resilience to environmental degradation and informing land use planning into the future. Confronting this challenge has been largely limited to inferring thresholds in univariate metrics of species richness and indices of biotic integrity and has largely ignored how land use legacies of the past may shape community responses of today. By leveraging data for 13,069 riverine sites from temperate, subtropical, and boreal climate zones on four continents, we characterize patterns of community change along diverse gradients of urbanization and agricultural land use, and identity threshold values beyond which significant alterations in species composition exists. Our results demonstrate the apparent universality by which freshwater fish communities are sensitive to even low levels of watershed urbanization (range of threshold values: 1%–12%), but consistently higher (and more variable) levels of agricultural development (2%–37%). We demonstrated that fish community compositional thresholds occurred, in general, at lower levels of watershed urbanization and agriculture when compared to threshold responses in species richness. This supports the notion that aggregated taxon‐specific responses may better reflect the complexity of assemblage responses to land use development. We further revealed that the ghost of land use past plays an important role in moderating how current‐day fish communities respond to land use intensification. Subbasins of the United States experiencing greater rates of past land use change demonstrated higher current‐day thresholds. Threshold responses of community composition, such as those identified in our study, illustrate the need for globally coordinated efforts to prioritize country‐specific management and policy initiatives that ensure that freshwater fish diversity is not inevitably lost in the future.     

Riding the perennial gale: working-class Puerto Ricans and the involution of colonial capitalism

Hurricane María devastated Puerto Rico in September 2017, deepening an already dire economic situation and amplifying an ongoing wave of out-migration. In the age of permanent man-made climate change, hurricanes, like extended economic crises, are “big events” produced by the capitalist despoiling of nature and labor, further exposing the dispossessed and displaced to structural violence. A colony of the USA since 1898, perhaps Puerto Rico has now once again “changed forever,” as the popular belief goes in the wake of María. If so, these changes will continually be experienced and enacted differently by subjects unevenly positioned in terms of unequal relationships of power and privilege. I propose an empirically informed research orientation that examines the situation of contemporary working-class Puerto Ricans in terms of their strategic responses to the involution of colonial capitalism. As a dimension of social life, working-classness is not contracting but expanding, in the context of an ongoing “debt crisis” better understood in terms of the self-consumption, or involution, of the modality of colonial capitalism established in Puerto Rico in the 1940s. In this light, strategic actions of working-class Puerto Ricans such as migration, informal labor, and subsistence/domestic production are not evidence of alternate modes of being, but part of the very conditions of working-classness today. I conclude by briefly identifying three areas for future research to flesh out the proposed orientation, focusing in the immediate term on responses to María by working-class communities in the island and the diaspora, in interaction with local and US elites.     

Perspectives from Ten Years of Protist Studies by High‐Throughput Metabarcoding

During the last decade, high‐throughput metabarcoding became routine for analyzing protistan diversity and distributions in nature. Amid a multitude of exciting findings, scientists have also identified and addressed technical and biological limitations, although problems still exist for inference of meaningful taxonomic and ecological knowledge based on short DNA sequences. Given the extensive use of this approach, it is critical to settle our understanding on its strengths and weaknesses and to synthesize up‐to‐date methodological and conceptual trends. This article summarizes key scientific and technical findings, and identifies current and future directions in protist research that uses metabarcoding.     

Four New Ladybug Species Belonging to Decadiomus Chapin (Coleoptera: Coccinellidae) from Puerto Rico

While searching for native natural enemies attacking invasive insect pests in Puerto Rico, we found four undescribed ladybug species belonging to the Caribbean ladybug genus Decadiomus Chapin. In this article, we describe the following species from Puerto Rico: Decadiomus seini n. sp., Decadiomus ramosi n. sp., Decadiomus hayuyai n. sp., and Decadiomus martorelli n. sp. Illustrations of the dorsal habitus, shape of prosternal carinae, and drawings of male and female genitalia are presented. We also present a key for Diomini of Puerto Rico and discuss their importance as potential biocontrol agents.     

Production of a Pyrrole Antibiotic by a Marine Bacterium

Evidence is presented for the isolation and identification of bacteria able to synthesize an unusual antibiotic containing five bromine atoms per molecule. The identification and taxonomic position of these bacteria was made by use of a computer in conjunction with traditional methods. These microorganisms and closely related strains have been isolated on various occasions from tropical water in the vicinity of Puerto Rico. One bacterium, a pseudomonad, has been given the name Pseudomonas bromoutilis because of its distinctive capability. The antibiotic has been extracted, purified, and obtained in crystal form, and its structure has been determined. Although clinical tests of its properties were not encouraging, it may be of significant value and interest from an ecological standpoint.