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Research and regulatory interest into (Neo)tropical aquatic pesticide ecotoxicology has increased considerably over the past few years. However, pesticide effect assessment frameworks in (Neo)tropical areas remain largely undeveloped and as such not implemented. The present study provides an overview of studies into the comparison of pesticide sensitivity between (Neo)tropical and temperate aquatic taxa. Recommended assessment factors to be applied to temperate toxicity data for use in tropical effect assessments differ significantly between these studies. Shortcomings and bottlenecks of available pesticide sensitivity comparison studies based on results from bioassays, species sensitivity distributions, and model ecosystem studies are scrutinized. Current data lacks and (subsequent) indications for future research are also covered. Ultimately, implications for procedures aimed at the derivation of regulatory acceptable concentrations for pesticides in (Neo)tropical edge-of-field surface waters are discussed. Integr Environ Assess Manag 2022;00:1–10. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). publishersversion published

International audience; Crickets (Ensifera, Grylloidea) are not commonly used as ecological indicators in contrary to other Orthoptera (e.g., grasshoppers and katydids). However, they are sensitive to environmental changes and abundant in tropical regions. To evaluate whether crickets are relevant bioindicators of tropical ecosystems, we investigated cricket assemblages along a tropical ecological gradient. We collected crickets during both day and night in southern New Caledonia for three stages of ecological succession: open shrubland, preforest, and forest. Simultaneously, we measured several environmental variables, such as temperature and relative humidity, at each sampling site. Cricket species assemblages showed a clear response to ecological succession. The highest and lowest species richness and abundances of individuals were, respectively, found in forest and shrubland, with species specialized in each ecological stage revealing the conservation value of each of these stages. Similar results were found when considering only the part of cricket communities with the ability to acoustically communicate. This work is part of a larger research program about Neocaledonian crickets and contributes to support the use of acoustic approaches to monitor tropical environments. In conclusion, these findings highlight the potential value of crickets as an environmental indicator in tropical ecosystems. The results also contribute to the discussion of the intrinsic conservational value of shrublands in New Caledonia and similar ecotypes.; Bien que d’autres groupes d’orthoptères soient largement utilisés comme bioindicateur, les grillons sont peu considérés dans les études écologiques. Pourtant, les grillons sont à la fois sensibles aux changements environnementaux et très abondants dans les régions tropicales. Dans cette étude, nous avons décrit les assemblages de grillons le long d’un gradient écologique en milieu tropical. Nous avons collecté les individus en période nocturne et diurne, sur 12 sites, et dans trois formations végétales du Sud de la Nouvelle Calédonie : le maquis, le paraforestier et le forestier. Des variables environnementales comme la température et l’humidité relative ont été collectées simultanément aux relevés de grillons. Les assemblages de grillons montrent une réponse très claire à la succession environnementale, suivant le gradient écologique, avec une diversité d’espèce et une abondance d’individus plus élevées en milieu forestier qu’en milieu maquis. Chaque stade du gradient écologique montre un assemblage unique d’espèces. Des résultats similaires sont obtenus en ne considérant que la part de la communauté des grillons qui utilisent l’acoustique pour communiquer. Ces résultats, interprétés à la lumière de travaux complémentaires faisant parties du même programme de recherche sur les grillons de Nouvelle-Calédonie, supporte l’analyse de relevés acoustiques pour évaluer l’état des milieux. En conclusion, les résultats soutiennent l’intérêt des grillons comme indicateurs écologiques du milieu tropical. Ces résultats contribuent également à la reconnaissance de la valeur intrinsèque des maquis en terme de conservation de la biodiversité en Nouvelle-Calédonie et dans des écotypes similaires.

Climate change is a major threat to species worldwide, yet it remains uncertain whether tropical or temperate species are more vulnerable to changing temperatures. To further our understanding of this, we used a standardised field protocol to (1) study the buffering ability (ability to regulate body temperature relative to surrounding air temperature) of neotropical (Panama) and temperate (the United Kingdom, Czech Republic and Austria) butterflies at the assemblage and family level, (2) determine if any differences in buffering ability were driven by morphological characteristics and (3) used ecologically relevant temperature measurements to investigate how butterflies use microclimates and behaviour to thermoregulate. We hypothesised that temperate butterflies would be better at buffering than neotropical butterflies as temperate species naturally experience a wider range of temperatures than their tropical counterparts. Contrary to our hypothesis, at the assemblage level, neotropical species (especially Nymphalidae) were better at buffering than temperate species, driven primarily by neotropical individuals cooling themselves more at higher air temperatures. Morphology was the main driver of differences in buffering ability between neotropical and temperate species as opposed to the thermal environment butterflies experienced. Temperate butterflies used postural thermoregulation to raise their body temperature more than neotropical butterflies, probably as an adaptation to temperate climates, but the selection of microclimates did not differ between regions. Our findings demonstrate that butterfly species have unique thermoregulatory strategies driven by behaviour and morphology, and that neotropical species are not likely to be more inherently vulnerable to warming than temperate species.

Tropical forest and swidden agriculture are declining, while commercial plantation is continuously expanding. However, little is known about the mechanisms, processes and trends of the tropical forest-swidden-plantation (FSP) nexus. Global ongoing initiatives including the UN-REDD Programme, not only have repeatedly emphasized the significance of conserving forests, reforestation and afforestation, but re-pushed swidden agriculture to the forefront of a long-standing international debate of climate changes and biodiversity. Many facets limit our understanding of swidden agriculture. The lack of geographic and demographic data and their dynamics across the tropics undoubtedly further aggravate this situation since the first appeal of eradication of shifting cultivation by the FAO. Although recent studies have enriched significantly our knowledge of forest loss and plantation expansion, previous research has proceeded separately and has yet to be integrated under the umbrella of sustainable swidden agriculture. Efforts are needed to investigate the dynamics of the FSP nexus for sake of a synergetic goal of climate mitigation and poverty alleviation.

Florivory is an ancient interaction which has rarely been quantified due to a lack of standardized protocols, thus impairing biogeographical and phylogenetic comparisons. We created a global, continuously updated, open-access database comprising 180 species and 64 families to compare floral damage between tropical and temperate plants, to examine the effects of plant traits on floral damage, and to explore the eco-evolutionary dynamics of flower-florivore interactions. Flower damage is widespread across angiosperms, but was two-fold higher in tropical vs temperate species, suggesting stronger fitness impacts in the tropics. Flowers were mostly damaged by chewers, but neither flower color nor symmetry explained differences in florivory. Herbivory and florivory levels were positively correlated within species, even though the richness of the florivore community does not affect florivory levels. We show that florivory impacts plant fitness via multiple pathways and that ignoring this interaction makes it more difficult to obtain a broad understanding of the ecology and evolution of angiosperms. Finally, we propose a standardized protocol for florivory measurements, and identify key research avenues that will help fill persistent knowledge gaps. Florivory is expected to be a central research topic in an epoch characterized by widespread decreases in insect populations that comprise both pollinators and florivores.

Anthropogenic climate change is expected to have major impacts on domesticated livestock, including increased heat stress in animals in both intensive and extensive livestock systems. We estimate the changes in the number of extreme heat stress days per year for animals raised outdoors that can be expected in the major domesticated animal species (cattle, sheep, goats, poultry, and pigs) across the globe during this century. We used the temperature humidity index as a proxy for heat stress, calculated using temperature and relative humidity data collated from an ensemble of CMIP6 climate model output for mid and end century. We estimate changes in the proportions of different livestock species that may be at increased risk of extreme heat stress under two contrasting greenhouse gas emission scenarios. Results are discussed in relation to changes in the suitability of different climate conditions for domesticated livestock during the current century. We find that by end century, extreme heat stress risk is projected to increase for all livestock species in many parts of the tropics and some of the temperate zones, and to become climatically more widespread, compared to 2000. Although adaptation options exist for both intensive and extensive livestock production systems, the increasing pervasiveness of extreme heat stress risk in the future will seriously challenge the viability of outdoor livestock keeping, particularly in the lower latitudes in lower and middle-income countries where the costs of adaptation may be challenging to address.

Microeukaryotes play key ecological roles in the microbial web of aquatic ecosystems. However, large knowledge gaps urgently need to be filled regarding the biogeography with associated shaping mechanisms and co-occurrence patterns of microeukaryotes under freshwater-saltwater gradients, especially true in tropical regions. Here, we investigated microeukaryotes of six mixed freshwater-saltwater regions in the Pearl River Estuary and surrounding coasts in southern China, with salinity ranging 0.1-32.0% and distances spanned up to 500 km, using molecular ecological methods. Results indicate that the biogeography of abundant and rare microeukaryotic communities was similar, both their co-occurrence patterns and biogeographical patterns were driven by deterministic and stochastic processes. The environmental factors with higher selective pressure than dispersal limitation meant that the role of deterministic process in structuring communities was more significant than that of stochastic process, and salinity played important role in structuring both microeukaryotic communities and networks. The abundant communities had stronger influence on entire microeukaryotic communities and seemed to be more sensitive to environmental changes than their rare counterparts, while rare ones had stronger interspecific relationships. Finally, the geographic scale and environmental gradients of study regions should firstly be clarified in future research on the ecological processes of microeukaryotes before conclusions are drawn.

As extreme climate events are predicted to become more frequent because of global climate change, understanding their impacts on natural systems is crucial. Tropical forests are vulnerable to droughts associated with extreme El Niño events. However, little is known about how tropical seedling communities respond to El Niño-related droughts, even though patterns of seedling survival shape future forest structure and diversity. Using long-term data from eight tropical moist forests spanning a rainfall gradient in central Panama, we show that community-wide seedling mortality increased by 11% during the extreme 2015-16 El Niño, with mortality increasing most in drought-sensitive species and in wetter forests. These results indicate that severe El Niño-related droughts influence understory dynamics in tropical forests, with effects varying both within and across sites. Our findings suggest that predicted increases in the frequency of extreme El Niño events will alter tropical plant communities through their effects on early life stages.

Background Heat stress in tropics is generally associated with significant economic losses resulting from reduced performance, morbidity, and mortality of livestock. To avoid serious consequences of heat stress, it is imperative to better understand the physiological responses and biochemical changes under the state of altered body homeostasis during different seasons of the year. Objectives This study aimed to evaluate the seasonal dynamics of physiological, oxidative and metabolic responses of lactating Nili‐Ravi buffaloes to the tropical climate of South China. Methods Physiological responses including rectal temperature (RT), body surface temperature (BST) and respiratory rate (RR) along with serum biochemical and antioxidant parameters of 20 lactating Nili‐Ravi buffaloes were evaluated during different seasons of the year. Results Higher temperature‐humidity Index (THI) during the summer season (>80) resulted in a significant increases in RR and BST as compared to the winter season. Higher oxidative stress was observed in the summer season as revealed by significantly higher MDA while lower serum antioxidant enzyme (TAC, GSH‐Px, SOD and CAT) contents. Moreover, serum cortisol was also significantly higher in summer and autumn. The levels of growth hormone and ACTH were also significantly (P, Seasonal dynamics of physiological and metabolic responses of lactating Nili‐Ravi buffaloes was studied under the tropical climate of south china. Higher temperature humidity Index (THI) during the summer season (>80) resulted in a significant increase in RR and BST as compared to the winter season. High oxidative stress was observed in the summer season as revealed by significantly higher MDA and Cortisol while lower serum antioxidant enzymes (T‐AOC, GSH‐Px, SOD and CAT) and growth hormone contents as compared to other seasons.

Many species are responding to global warming by shifting their distributions upslope to higher elevations, but the observed rates of shifts vary considerably among studies. Here we test the hypothesis that this variation is in part explained by latitude, with tropical species being generally more responsive to warming temperatures than are temperate species. We find support for this hypothesis in each of two independent empirical datasets—shifts in species’ elevational ranges, and changes in composition of forest inventory tree plots. Tropical species are tracking rising temperatures 2.1–2.4 times (range shift dataset) and 10 times (tree plot dataset) better than their temperate counterparts. Models predict that for a 100 m upslope shift in temperature isotherm, species at the equator have shifted their elevational ranges 93–96 m upslope, while species at 45° latitude have shifted only 37–42 m upslope. For tree plots, models predict that a 1°C increase in temperature leads to an increase in community temperature index (CTI), a metric of the average temperature optima of tree species within a plot, of 0.56 °C at the equator but no change in CTI at 45° latitude (–0.033). This latitudinal gradient in temperature tracking suggests that tropical montane biotas may be on an “escalator to extinction” as global temperatures continue to rise.

International audience; Dams and other man-made barriers impair upstream fish migration and thus threaten fish populations that need access to upper river reaches to complete their life cycle. For many years, fishways have been used to mitigate this impact. Fishways around the globe are typically built based on recommendations made for northern hemisphere species, particularly salmonids. These recommendations do not consider the locomotor characteristics and skills of other species, especially those living in the tropics. Among tropical species, freshwater eels and gobies of the Sicydiinae subfamily are important cultural and economic species that are particularly sensitive to the impact of man-made barriers. Our experimental study aimed to test different substrates and slopes for ramp-like fishways adapted to tropical eels and sicydiines. Among the five substrates tested for 368 eels Anguilla marmorata, elastomer pins appeared to be the most efficient. Elastomer pins also appeared to be more efficient than the fine concrete which is currently used in fishways for sicydiines (Sicyopterus lagocephalus, N = 1797, and Cotylopus acutipinnis, N = 1303). The slope had a lesser effect on the climbing success of sicydiines compared to substrate type, except for gradients greater than 50° that induced a slight decrease in success. Our results indicated that ramp-like fishways fitted with 1.0 cm diameter elastomer pins, positioned in staggered rows with a diagonal spacing of 1.3 cm, wetted with low-flow and angled less than 50°, are well adapted to accommodate the different locomotor characteristics and skills of tropical eels and sicydiines.

Rainfall regimes in many parts of the world have become increasingly dominated by fewer, but more extreme, rainfall events. Understanding how tree growth responds to changes in the frequency and intensity of rain events is critical to predicting how climate change will impact on forests and woodlands in the future. In this study, we used five tree‐ring records of the native Australian conifer Callitris columellaris that span a large (> 20°) latitudinal and climatic gradient from the mesic (tropical) north to the xeric (semi‐arid) south of Australia to investigate how inter‐annual and spatial variation in the delivery of rainfall (the intensity and frequency of rain events) influences tree growth. In semi‐arid biomes (∼300–400 mm rainfall annually), tree growth is most strongly related to the amount of rainfall from heavy (> 75th percentile) rain days or the number of extreme (> 90th percentile) rain days, regardless of differences in the seasonal distribution and average intensity of rainfall among sites. Our findings also indicate that there is likely a minimum threshold amount of daily rainfall (∼5 mm) that is required to stimulate tree growth in the semi‐arid zone. In contrast, in the tropics (> 800 mm annual rainfall), inter‐annual variation in growth is best explained by total growing season rainfall or the number of rain days > ∼5 mm (∼50th percentile of rain days) rather than extreme rainfall. Our findings indicate that not all rain events are important for driving tree growth, which has important implications for interpreting climatic signals in tree rings. Our findings also indicate that projected increases in the intensity of extreme rain events are likely to have contrasting impacts on tree growth across biomes, with greater and positive impacts on growth in semi‐arid biomes and potentially negative impacts on growth in tropical biomes of Australia.

Tropical ectotherms are thought to be especially vulnerable to climate change because they are thermal specialists, having evolved in aseasonal thermal environments. However, even within the tropics, habitat structure can influence opportunities for behavioral thermoregulation. Open (and edge) habitats likely promote more effective thermoregulation due to the high spatial heterogeneity of the thermal landscape, while forests are thermally homogenous and may constrain opportunities for behavioral buffering of environmental temperatures. Nevertheless, the ways in which behavior and physiology interact at local scales to influence the response to climate change are rarely investigated. We examined the thermal ecology and physiology of two lizard species that occupy distinct environments in the tropics. The brown anole lizard (Anolis sagrei) lives along forest edges in The Bahamas, whereas the Panamanian slender anole (Anolis apletophallus) lives under the canopy of mature forests in Panama. We combined detailed estimates of environmental variation, thermoregulatory behavior, and physiology to model the vulnerability of each of these species. Our projections suggest that forest-dwelling slender anoles will experience severely reduced locomotor performance, activity time, and energy budgets as the climate warms over the coming century. Conversely, the forest-edge-dwelling brown anoles may use behavioral compensation in the face of warming, maintaining population viability for many decades. Our results indicate that local habitat variation, through its effects on behavior and physiology, is a major determinant of vulnerability to climate change. When attempting to predict the impacts of climate change on a given population, broad-scale characteristics such as latitude may have limited predictive power.

Modifications to vegetation and soil due to changes in land use have the potential to alter the soil microbiome, with consequences for carbon and nutrient cycling. Despite the important function of soil microorganisms, little is known about their response to land‐use change, especially in tropical regions where current rates of land conversion are greatest. The aim of this meta‐analysis was to examine how land‐use change influences soil microbial properties in tropical ecosystems and to identify current trends and knowledge gaps in the literature. We identified 83 published paired studies that reported data on microbial biomass, abundance, composition, and enzyme activity under representative land‐use changes in the tropics. We calculated response ratios for studies that compared the following: reference forests to (a) agriculture, (b) pastures, (c) plantations, and (d) secondary forests. Soil microbial biomass decreased with forest conversion to agriculture and plantations. Microbial biomass response to land‐use change depended on rainfall classes, although this was the only microbial variable which had sufficient data to test for a rainfall effect. Microbial abundance and enzyme activity showed variable results depending on the type of forest conversion. Microbial diversity and richness did not show any pattern with forest conversion or recovery to secondary forests. Published studies were not representative of the range of biophysical conditions observed in the tropics. Sites in moist regions in the American tropics were overrepresented. To better predict how land‐use change affects the soil microbiome and its contribution to nutrient cycling, research should reflect observed environmental variation in the tropics. Abstract in Spanish is available with online material.

AIM: Bergmann's rule is an ecogeographical rule that describes a negative relationship between body size and temperature. Here, we used a multivariate measure of skull size (centroid size) as a proxy for body size to test the influence of temperature, precipitation, elevation, human influence and competition on size in Dicotyles tajacu and Tayassu pecari. LOCATION: American tropics and sub‐tropics. TAXON: Tayassuidae. METHODS: Using geometric morphometric methods, we measured 426 adult skulls of both peccary species from 174 different localities south of the equator and 83 in the north. We explored the effects of temperature, precipitation, altitude and human influence, controlling for spatial autocorrelation, using ordinary least squares models and the Akaike information criterion. Size differences where the species occur allopatrically or sympatrically, where competition could be a factor, were investigated using ANCOVA models. RESULTS: We found that peccaries were larger in the tropics. Temperature and precipitation explained the size variation of both peccaries in the southern hemisphere, whereas human influence is a predictor of size only for T. pecari. Size variation of northern D. tajacu is mainly explained by elevation and temperature. Tayassu pecari is consistently larger than D. tajacu in both hemispheres. Peccaries did not exhibit significant shifts in either rate of change in size or size–latitude relationships between allopatric and sympatric areas. MAIN CONCLUSIONS: Geographical variation in size of these peccaries does not support Bergmann's rule. In the tropics, precipitation and human influence appear to exert strong selective pressures on body size of peccaries, whose resource utilization patterns are shaped by group living. Size differences of the two species across the continents may contribute to their stable coexistence via interference rather than exploitative competition.

Ecologically relevant traits of organisms in an assemblage determine an ecosystem's functional fingerprint (i.e., the shape, size, and position of multidimensional trait space). Quantifying changes in functional fingerprints can therefore provide information about the effects of diversity loss or gain through time on ecosystem condition and is a promising approach to monitoring ecological integrity. This, however, is seldom possible owing to limitations in historical surveys and a lack of data on organismal traits, particularly in diverse tropical regions. Using data from detailed bird surveys from 4 periods across more than a century, and morphological and ecological traits of 233 species, we quantified changes in the avian functional fingerprint of a tropical montane forest in the Andes of Colombia. We found that 78% of the variation in functional space, regardless of period, was described by 3 major axes summarizing body size, dispersal ability (indexed by wing shape), and habitat breadth. Changes in species composition significantly altered the functional fingerprint of the assemblage and functional richness and dispersion decreased 35-60%. Owing to species extirpations and to novel additions to the assemblage, functional space decreased over time, but at least 11% of its volume in the 2010s extended to areas of functional space that were unoccupied in the 1910s. The assemblage now includes fewer large-sized species, more species with greater dispersal ability, and fewer habitat specialists. Extirpated species had high functional uniqueness and distinctiveness, resulting in large reductions in functional richness and dispersion after their loss, which implies important consequences for ecosystem integrity. Conservation efforts aimed at maintaining ecosystem function must move beyond seeking to sustain species numbers to designing complementary strategies for the maintenance of ecological function by identifying and conserving species with traits conferring high vulnerability such as large body size, poor dispersal ability, and greater habitat specialization. Article impact statement: Changes in functional fingerprints provide a means to quantify the integrity of ecological assemblages affected by diversity loss or gain.Cambios en las Huellas Funcionales Aviarias en un Bosque Neotropical de Montaña durante Cien Años como Indicadores de la Integridad del Ecosistema Resumen Las características ecológicamente relevantes de los organismos que pertenecen a un ensamblaje determinan la huella funcional de un ecosistema (es decir, la forma, el tamaño y la posición del espacio multidimensional de la característica en cuestión). Por lo tanto, la cuantificación de los cambios en las huellas funcionales puede proporcionar información sobre los efectos que tiene la pérdida o ganancia de diversidad a lo largo del tiempo sobre las condiciones del ecosistema; por esto se le considera una estrategia prometedora para el monitoreo de la integridad ecológica. Sin embargo, lo anterior es pocas veces posible debido a las limitaciones de los censos históricos y a la falta de datos sobre las características del organismo, particularmente en las diversas regiones tropicales. Con datos detallados de censos realizados durante cuatro periodos en más de un siglo, y utilizando las características morfológicas y ecológicas de 233 especies, cuantificamos los cambios en la huella funcional aviaria de un bosque tropical de montaña en los Andes de Colombia. Encontramos que el 78% de la variación en el espacio funcional, sin importar el periodo, estuvo descrito por tres ejes principales que resumen el tamaño corporal, la habilidad de dispersión (indicada por la forma de las alas) y la amplitud del hábitat. Los cambios en la composición de especies alteraron significativamente la huella funcional del ensamblaje y la riqueza y dispersión funcional disminuyeron en 35-60%. Debido a la pérdida de especies y a la adición de especies nuevas al ensamblaje, el espacio funcional disminuyó con el tiempo, pero, durante la década de 2010, al menos el 11% de su volumen se extendió a áreas de espacio funcional que no estaban ocupadas cien años antes. El ensamblaje ahora incluye menos especies de gran tamaño, más especies con buena habilidad de dispersión y menos especialistas de hábitat. Las especies que se perdieron eran funcionalmente únicas, lo que resultó en reducciones importantes en la riqueza y en la dispersión funcional después de su pérdida, e implicó consecuencias importantes para la integridad del ecosistema. Los esfuerzos de conservación enfocados en mantener la función del ecosistema deben ir más allá de la búsqueda de la preservación del número de especies y enfocarse también en el diseño de estrategias complementarias para el mantenimiento de la función ecológica por medio de la identificación y conservación de especies con características que otorgan una vulnerabilidad alta, como lo son el tamaño corporal grande, una habilidad de dispersión pobre y una mayor especialización de hábitat.

Globally, collapse of ecosystems—potentially irreversible change to ecosystem structure, composition and function—imperils biodiversity, human health and well‐being. We examine the current state and recent trajectories of 19 ecosystems, spanning 58° of latitude across 7.7 M km2, from Australia's coral reefs to terrestrial Antarctica. Pressures from global climate change and regional human impacts, occurring as chronic ‘presses’ and/or acute ‘pulses’, drive ecosystem collapse. Ecosystem responses to 5–17 pressures were categorised as four collapse profiles—abrupt, smooth, stepped and fluctuating. The manifestation of widespread ecosystem collapse is a stark warning of the necessity to take action. We present a three‐step assessment and management framework (3As Pathway Awareness, Anticipation and Action) to aid strategic and effective mitigation to alleviate further degradation to help secure our future.

Nickel laterite ore deposits are becoming increasingly important sources of Ni for the global marketplace and are found mainly in tropical and subtropical regions, including Indonesia, the Philippines, Papua New Guinea, Cuba, and New Caledonia. There are few legislatively derived standards or guidelines for the protection of aquatic life for Ni in many of these tropical regions, and bioavailability‐based environmental risk assessment (ERA) approaches for metals have mainly been developed and tested in temperate regions, such as the United States and Europe. This paper reports on a multi‐institutional, 5‐y testing program to evaluate Ni exposure, effects, and risk characterization in the Southeast Asia and Melanesia (SEAM) region, which includes New Caledonia, Papua New Guinea, the Philippines, and Indonesia. Further, we have developed an approach to determine if the individual components of classical ERA, including effects assessments, exposure assessments, and risk characterization methodologies (which include bioavailability normalization), are applicable in this region. A main conclusion of this research program is that although ecosystems and exposures may be different in tropical systems, ERA paradigms are constant. A large chronic ecotoxicity data set for Ni is now available for tropical species, and the data developed suggest that tropical ecosystems are not uniquely sensitive to Ni exposure; hence, scientific support exists for combining tropical and temperate data sets to develop tropical environmental quality standards (EQSs). The generic tropical database and tropical exposure scenarios generated can be used as a starting point to examine the unique biotic and abiotic characteristics of specific tropical ecosystems in the SEAM region. Integr Environ Assess Manag 2021;17:802–813. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC), KEY POINTS An approach to determine if the individual components of classical environmental risk assessment (ERA) methodologies are applicable in the Southeast Asia and Melanesia (SEAM) region is presented. A main conclusion is that, although ecosystems and exposures may be different in tropical systems, ERA paradigms are constant. A large chronic ecotoxicity data set for Ni is now available for tropical species, and the data developed suggest that tropical ecosystems are not uniquely sensitive to Ni exposure. The generic tropical database and tropical exposure scenarios generated can be used as a starting point to examine the unique biotic and abiotic characteristics of specific tropical ecosystems in the SEAM region.

Aim: The evolutionary causes of the latitudinal diversity gradient are debated. Hypotheses have ultimately invoked either faster rates of diversification in the tropics, or more time for diversification due to the tropical origins of higher taxa. Here we perform the first test of the diversification rate and time hypotheses in freshwater ray-finned fishes, a group comprising nearly a quarter of all living vertebrates. Location: Global. Time period: 368-0 mya. Major taxa studied: Extant freshwater ray-finned fishes. Methods: Using a mega-phylogeny of actinopterygian fishes and a global database of occurrence records, we estimated net diversification rates, the number of colonizations and regional colonization times of co-occurring species in freshwater drainage basins. We used Generalized Additive Models to test whether these factors were related to latitude. We then compared the influence of diversification rates, colonization numbers, colonization times and surface area on species richness, and how these factors are related to each other. Results: While both diversification rates and time were related to richness, time had greater explanatory power and was more strongly related to latitude than diversification rates. Other factors (basin surface area, number of colonizations) also helped explain richness but were unrelated to latitude. The world9s most diverse freshwater basins (Amazon, Congo rivers) were dominated by lineages with Mesozoic origins. The temperate groups dominant today arrived near the K-Pg boundary, leaving comparatively less time to build richness. Diversification rates and colonization times were inversely related: recently colonized basins had the fastest rates, while ancient species-rich faunas had slower rates. Main conclusions: We concluded that time is the lead driver of latitudinal richness disparities in freshwater fish faunas. We suggest that the most likely path to building very high species richness is through diversification over long periods of time, rather than diversifying quickly.

The ubiquity of anthropogenic pressures in tropical regions is the primary threat to biodiversity, and one of the most significant challenges humanity is currently facing (Lewis et al., 2015). Hope is set on regrowing secondary forests, which may serve as habitat refugia for many species and play a central role in ecosystem functioning (Hethcoat et al., 2019). Secondary forests currently account for over half of the world's tropical forests, and their distribution is expanding as they gradually replace old-growth stands that have been clear-cut for productive use, but subsequently abandoned (Chazdon et al., 2016). Nowadays, however, the capacity of these regrowing stands to return to their original state is uncertain (Arroyo-Rodriguez et al., 2017) as they occur mostly as isolated, small patches embedded in matrices dominated by agricultural and pasture lands (Barlow et al., 2016). To further understand the potential role of successional forests as a buffer against biodiversity loss, we need to move the discussion from local to landscape scales and embrace the manifold forces driving succession (Arroyo-Rodriguez et al., 2017; van Breugel et al., 2019).

Pearl millet [Pennisetum glaucum (L.) R. Br.] is one of the world’s hardiest warmseason cereal crop and is cultivated mainly in the semi-arid tropics of Asia and Africa for food, feed, fodder, and brewing. It is mainly cultivated for its gluten-free grains with high content and better quality of nutrients. Pearl millet is a resilient crop that can produce grain and biomass under harsh conditions like low fertility, erratic rainfall, acidic and saline soils, and the hottest climates. However, biotic stresses such as downy mildew and blast diseases and abiotic stresses, especially drought and seedling- and flowering-stage heat stress, pose constant threat to the realization of yield potential of this crop. To make further improvement in threshold level of abiotic and biotic stress tolerance, breeders are looking for novel genes in diverse germplasm sources. Crop wild relatives (CWRs) could be a source of novel genes that are important for diversification of the genetic base of pearl millet. A stage-gate process is proposed for the efficient management of prebreeding programs using CWRs as a source of germplasm diversity and improvement. This article explains the various strategies for capturing and using alleles for climate resilience traits improvement. This article covers breeders’ perspectives on importance of using CWRs as germplasm source for crop improvement. This article also describes the availability of CWRs, characterization of new traits and the strategies to be applied for the identification and introduction of genes of interest in elite breeding lines and commercial varieties and hybrids of pearl millet.

AIM: Plants that host root‐symbiotic nitrogen‐fixing bacteria have an important role in driving terrestrial ecosystem processes, but N‐fixing ability is unequally distributed among plant taxa and ecosystems. Here we explore the large‐scale distribution of N‐fixing plant species worldwide. LOCATION: Global. TIME PERIOD: Present. MAJOR TAXA STUDIED: Vascular plants. METHODS: We estimated root‐symbiotic N‐fixing plant species diversity (as Shannon entropy) and relative richness (log‐ratio of N‐fixing to non‐fixing plant species) for c. 7,800 km² hexagonal grid cells using the NodDB and Global Biodiversity Information Facility (GBIF) databases. Additionally, we explored the distributions of plant species associated with rhizobia, actinobacteria or cyanobacteria (relative to other plant species), and the relative richness of N‐fixing trees (log‐ratio of N‐fixing to non‐fixing trees). We related N‐fixing plant species distribution to environmental (climate, soil) and biogeographical (biome, realm) variables using multiple linear regression. RESULTS: N‐fixing plant diversity and relative richness showed unimodal relationships with latitude. Diversity of N‐fixing plants was highest in warm and wet climates, but in dry biomes and in Australasia. The relative richness of N‐fixing plants was highest in warm and dry climates, in tropical and temperate grasslands and in Eurasia. Plants associated with cyanobacteria were more widely distributed near the equator, while those associated with rhizobia were more prevalent at the edge of the tropics, and those associated with actinobacteria at higher latitudes (especially in boreal forests). The relative richness of N‐fixing tree species was highest in cold and dry areas and in boreal forests, with contrasting peaks in the Northern and Southern Hemispheres. MAIN CONCLUSIONS: The distribution of N‐fixing plant species exhibits regional hotspots and coldspots related to both environmental conditions and biogeographical history. Global N‐fixing plant distributions are different for the key root‐symbiotic bacterial groups. Information about N‐fixing plant distribution can improve global models of ecosystem functions and contribute to understanding how plants respond to global change.