Biotic Sources Research Articles

Members of WRKY Group III Transcription Factors Are Important in Mite Infestation in Strawberry (Fragaria × ananassa Duch.)

Strawberry is frequently attacked by mites, which directly affects the yield and quality of this fruit species. The WRKY Group III transcription factors (TFs) play an important role in plant tolerance to biotic sources of stress, such as pathogens and insect pests. In this study, six Group III WRKY TFs (FaWRKY25, FaWRKY31, FaWRKY32, FaWRKY43, FaWRKY44, and FaWRKY45) were identified in strawberry. A phylogenetic analysis showed that the six WRKY III TFs were divided into two clades and all had a conserved WRKYGQK domain and the C-X7-C-X23-H-T-C zinc finger motif. An interaction network analysis revealed that FaWRKY44 was co-expressing with FaWRKY25 and FaWRKY45. The expression patterns showed that the WRKY Group III genes responded to plant hormones and mite infestation in strawberry. To further verify the role of FaWRKY25 in plant resistance to mites, we cloned the FaWRKY25 gene and overexpressed it in transgenic plants. An in vivo subcellular localization analysis indicated that the FaWRKY25 protein was localized in the nucleus. Fewer mites were also detected on the wild-type plants than on FaWRKY25-overexpressing transgenic plants, suggesting that FaWRKY25 negatively regulates the resistance of strawberry to mites. The present study advances our understanding on a potential target that mites use to manipulate host plant defenses.

Bacterial dynamics and biotic sources in the developing swimming crab embryos

The microbial community associated with aquatic animals begins to assemble from the embryonic stage and plays a vital role in their growth and survival. However, the microbial community of the swimming crab Portunus trituberculatus during its embryonic period has not yet been studied. In this study, we investigated the embryonic bacterial community (EBC) of this species across the developmental cycle to elucidate its longitudinal dynamics and biotic sources. The results showed that the diversity of the EBC decreased with host development. The composition of the EBC varied across embryonic development, with a high percent of persistent bacteria and the gradual replacement of γ-Proteobacteria (mainly Oceanospirillaceae and Colwelliaceae) by α-Proteobacteria (Rhodobacteraceae and Flavobacteriaceae) as the major signatures of the succession patterns. Moreover, the unique amplicon sequence variants (ASVs) exhibited the highest functional potentials at the cleavage stage, whereas the shared ASVs did so at the later stages. Furthermore, maternal tissue, mainly the ovary and abdominal setae, contributed the most to the EBC, while rearing water contributed minimally. Overall, our results reveal succession patterns and biotic sources of EBC during the developmental cycle, highlighting that the dominance of embryonic bacteria starts from the early stage of embryo and bacterial vertical transmission is of significance during embryonic development. We also suggest the necessity of microbial management from maternal crabs.

CRISPR/Cas9 opens new horizon of crop improvement under stress condition

Plants are exposed to a myriad of stresses, stemming from abiotic and biotic sources, significantly threatening agricultural productivity. The low crop yield, coupled with the global burden of population has resulted in the scarcity of quality food, exacerbating socio-economic issues like poverty, hunger, and malnutrition. Conventional breeding methods for the generation of stress-tolerant plants are time-consuming, limit genetic diversity, and are not sustainable for the consistent production of high-yielding crops. In recent years, the use of high-throughput, genome editing (GE) technique has revolutionized the crop-improvement paradigm, ushering greater prospects for agricultural progress. Among these tools, the Clustered regularly interspaced short palindromic repeat (CRISPR), and its associated nuclease protein Cas9, have appeared as a ground-breaking technology, allowing precise knockout (KO), upregulation, and downregulation of target gene expression. Apart from its high efficacy and speed, this programmable nuclease offers exceptional specificity with minimal off-target effects. Here in, we aim to review the latest findings on the application of the CRISPR/Cas9 genome editing tool for generating resilience in plants against environmental stresses.

The Arctic marine soundscape of the Amundsen Gulf, Western Canadian Arctic

The underwater soundscape, a habitat component for Arctic marine mammals, is shifting. We examined the drivers of the underwater soundscape at three sites in the Amundsen Gulf, Northwest Territories, Canada from 2018 to 2019 and estimated the contribution of abiotic and biotic sources between 20 Hz and 24 kHz. Higher wind speeds and the presence of bearded seal (Erignathus barbatus) vocalizations led to increased SPL (0.41 dB/km/h and 3.87 dB, respectively), while higher ice concentration and air temperature led to decreased SPL (−0.39 dB/% and − 0.096 dB/°C, respectively). Other marine mammals did not significantly impact the ambient soundscape. The presence of vessel traffic led to increased SPLs (12.37 dB) but was quieter at distances farther from the recorder (−2.57 dB/log m). The presence of high frequency and broadband signals produced by ice led to increased SPLs (7.60 dB and 10.16 dB, respectively).

Reassembly and biotic sources of carapace bacterial community of Portunus trituberculatus after host molting

Crustaceans molt repeatedly during their development, which leads to frequent reassembly of their associated microbial communities. However, the reassembly of the carapace bacterial community (CBC) and its sources remain largely unclear. Here, these concerns were explored by investigating the succession pattern, assembly processes, and biotic sources of CBC of the swimming crab Portunus trituberculatus after host molting. Rhodobacteraceae, significantly discarded with the molted hard shell, was recruited during the 72 h postmolt. The early colonists such as Pseudoalteromonadaceae and Oeanospirillaceae had the higher physiological functional potentials for colonization, mainly via homogeneous selection. By contrast, the late colonists such as Flavobacteriaceae and Pseudomonadaceae had higher metabolic potentials and their colonization was governed by drift first and dispersal limitation later. The CBC was primarily shaped by multiple colonist pools, especially preceding carapace bacteria. Seawater had a higher contribution for CBC at the early stage than the late stage via providing the key bacteria mainly Rhodobacteraceae. These findings advance our understanding of the CBC and its reassembly pattern and sources, highlighting the importance of seawater bacteria for the early colonists. We also suggest the possibility and potential timing of using probiotics in the rearing water for the management of carapace microbiota in the aquaculture practice.

Distribution of Acetogenic Naphthoquinones in Droseraceae and Their Chemotaxonomic Utility.

Chemotaxonomy is the link between the state of the art in analytical chemistry and the systematic classification and phylogenetic analysis of biota. Although the characteristic secondary metabolites from diverse biotic sources have been used in pharmacology and biological systematics since the dawn of mankind, only comparatively recently established reproducible methods have allowed the precise identification and distinction of structurally similar compounds. Reliable, rapid screening methods like TLC (Thin Layer Chromatography) can be used to investigate sufficiently large numbers of samples for chemotaxonomic purposes. Using distribution patterns of mutually exclusive naphthoquinones, it is demonstrated in this review how a simple set of chemical data from a representative sample of closely related species in the sundew family (Droseraceae, Nepenthales) provides taxonomically and phylogenetically informative signal within the investigated group and beyond.

Landscape as the Basic Potential of the Regional Development (Case Study: The Važec Village, Slovakia)

Abstract The development of each spatial unit is determined by the capital, whether natural or socioeconomic, which it possesses. Natural capital is determined by the properties of individual natural components of the landscape, both abiotic and biotic sources. Socioeconomic capital is linked to a socioeconomic activities in the landscape. Capital creates certain prerequisites for the development of individual socioeconomic activities. Society does not always optimally use the offered potential, which is connected with the manifestation of various environmental problems. The paper focuses on the presentation of the methodical procedure of natural capital evaluation on the example of the village of Važec. The methodological procedure is based on an integrated approach to the landscape. It focuses on the assessment of both natural capital and limiting factors resulting from the development of socioeconomic activities, namely: – positive arising from the needs of nature and landscape protection, as well as from the protection of natural resources, – negative (stress factors) linked to the contamination of environmental components, which in retrospect in relation to socioeconomic activities act as hygienic limits.

Exopolysaccharides Synthesized by Rhizospheric Bacteria: A Review Focused on Their Roles in Protecting Plants against Stress

Plants are constantly exposed to a wide range of environmental factors that cause different kinds of stress, such as drought, salinity, heat, frost, and low nutrient availability. There are also biotic sources of stress, which include pathogens (bacteria, viruses, pests), herbivores, and plant competitors. These various types of stress affect normal plant physiology and development, and may lead to significantly lower yields. However, certain microorganisms (MOs), known as plant growth-promoting rhizobacteria (PGPR), can interact with and benefit plants in stressful environments. They do so through a series of mechanisms which contribute to minimizing the negative effects of plants’ responses to stress. This review summarizes current knowledge about those mechanisms, with a focus on the production of exopolysaccharides (EPSs). These compounds can act as osmoprotectants, promote the production of phytohormones, prevent the entry of pathogens through roots, bioremediate metals, and improve soil structure and permeability, among many other beneficial effects. This makes them suitable alternatives to guarantee food security while reducing the excessive use of chemical agricultural inputs and their harmful consequences for the environment.

Spatial distribution, source apportionment, and assessment of marine water quality parameters in the Bohai Sea, China

A two–year (2020−2021) survey dataset of six water quality parameters (pH, dissolved oxygen (DO), chemical oxygen demand (COD), dissolved inorganic nitrogen (DIN), soluble reactive phosphate (SRP), and petroleum pollutants) was used to investigate their spatial distribution in the Bohai Sea and quantify their potential sources. There were significant differences in spatial distribution of the parameters. High concentrations of COD, DIN and SRP were found in three bays, with terrestrial input being the main pollution source. Phosphorus–limiting conditions were present in the Bohai Sea. High petroleum pollutant concentrations were identified in port areas, offshore oilfields, and adjacent areas. The pH was above the global oceanic average and there were no signs of acidification. The contribution of the mixed terrestrial inputs, maritime transportation, and offshore oil exploitation sources, oceanic and associated biotic sources, and seawater–atmosphere exchange and atmospheric deposition sources to water quality were 63.4 %, 8.0 %, and 28.6 %, respectively.

Zinc oxide nanoparticles prepared through microbial mediated synthesis for therapeutic applications: a possible alternative for plants.

Zinc oxide nanoparticles (ZnO-NPs) synthesized through biogenic methods have gained significant attention due to their unique properties and potential applications in various biological fields. Unlike chemical and physical approaches that may lead to environmental pollution, biogenic synthesis offers a greener alternative, minimizing hazardous environmental impacts. During biogenic synthesis, metabolites present in the biotic sources (like plants and microbes) serve as bio-reductants and bio-stabilizers. Among the biotic sources, microbes have emerged as a promising option for ZnO-NPs synthesis due to their numerous advantages, such as being environmentally friendly, non-toxic, biodegradable, and biocompatible. Various microbes like bacteria, actinomycetes, fungi, and yeast can be employed to synthesize ZnO-NPs. The synthesis can occur either intracellularly, within the microbial cells, or extracellularly, using proteins, enzymes, and other biomolecules secreted by the microbes. The main key advantage of biogenic synthesis is manipulating the reaction conditions to optimize the preferred shape and size of the ZnO-NPs. This control over the synthesis process allows tailoring the NPs for specific applications in various fields, including medicine, agriculture, environmental remediation, and more. Some potential applications include drug delivery systems, antibacterial agents, bioimaging, biosensors, and nano-fertilizers for improved crop growth. While the green synthesis of ZnO-NPs through microbes offers numerous benefits, it is essential to assess their toxicological effects, a critical aspect that requires thorough investigation to ensure their safe use in various applications. Overall, the presented review highlights the mechanism of biogenic synthesis of ZnO-NPs using microbes and their exploration of potential applications while emphasizing the importance of studying their toxicological effects to ensure a viable and environmentally friendly green strategy.

A new bioassessment multimetric index (BECOME) and diagnostic tool (BECOMEd) for small standing waters

Small shallow lakes and ponds (SSWs) have high conservation value and support numerous ecosystem services. However, these small ecosystems face many threats, including eutrophication and internal biotic pressures like Cyprinidae or exotic bioturbators crayfish, which tend to shift biodiverse SSWs to a turbid state dominated by phytoplankton unfitted to numerous usages, and compromise the effectiveness of their restoration. The ecological quality of SSWs and the efficiency of their management still remain poorly evaluated because of the lack of adapted tools. To fill this gap, we propose a new multimetric index (BECOME) and a diagnostic tool (BECOMEd) both based on macrophyte and invertebrate communities. BECOME exhibits a high sensitivity to the impact of surrounding crops, urbanization and fertilized meadows, morphological alterations, and various internal biotic sources of alterations, in a wide variety of geological and climatic contexts. BECOME is especially innovative, because taking into account internal biotic sources of pressures neglected by most of the existing biological WFD-compliant indices for European lakes and ponds, despite their importance in SSW threats. BECOMEd allows to identify the major alteration sources and estimates their relative contribution to SSW degradation, helping managers to prioritize actions or to evaluate their effectiveness. The statistical design applied for the index construction has been fitted to develop biological index for ecosystems influenced by a wide amplitude of numerous environmental conditions. This design could be easily applied elsewhere in the world, for SSWs but also for other types of ecosystems.

Observed electric charge of insect swarms and their contribution to atmospheric electricity

The atmosphere hosts multiple sources of electric charge that influence critical processes such as the aggregation of droplets and the removal of dust and aerosols. This is evident in the variability of the atmospheric electric field. Whereas these electric fields are known to respond to physical and geological processes, the effect of biotic sources of charge has not hitherto been considered. Here, we combine theoretical and empirical evidence to demonstrate that honeybee swarms directly contribute to atmospheric electricity, in proportion to the swarm density. We provide a quantitative assessment of this finding, by comparing the electrical contribution of various swarming insect species with common abiotic sources of charge. This reveals that the charge contribution of some insect swarms will be comparable with that of meteorologically induced variations. The observed transport of charge by insects therefore demonstrates an unexplored role of biogenic space charge for physical and ecological processes in the atmosphere.

Synbiotics and Their Antioxidant Properties, Mechanisms, and Benefits on Human and Animal Health: A Narrative Review.

Antioxidants are often associated with a variety of anti-aging compounds that can ensure human and animal health longevity. Foods and diet supplements from animals and plants are the common exogenous sources of antioxidants. However, microbial-based products, including probiotics and their derivatives, have been recognized for their antioxidant properties through numerous studies and clinical trials. While the number of publications on probiotic antioxidant capacities and action mechanisms is expanding, that of synbiotics combining probiotics with prebiotics is still emerging. Here, the antioxidant metabolites and properties of synbiotics, their modes of action, and their different effects on human and animal health are reviewed and discussed. Synbiotics can generate almost unlimited possibilities of antioxidant compounds, which may have superior performance compared to those of their components through additive or complementary effects, and especially by synergistic actions. Either combined with antioxidant prebiotics or not, probiotics can convert these substrates to generate antioxidant compounds with superior activities. Such synbiotic-based new routes for supplying natural antioxidants appear relevant and promising in human and animal health prevention and treatment. A better understanding of various component interactions within synbiotics is key to generating a higher quality, quantity, and bioavailability of antioxidants from these biotic sources.

Associated fungal pathogens and causes of postharvest losses in the avocado value chain in Hossana town market, Ethiopia

A significant proportion of post-harvest loss of agricultural produce is experienced in Ethiopia, especially in perishable horticultural commodities like fruits (mango, banana, papaya, avocado, sweet orange) and vegetables. Postharvest diseases derived from biotic sources such as microbial pathogens, or physiological disorders caused by abiotic sources contribute to shortening the postharvest life of the avocados, leading to loss in fruit quality. This study aimed to assess post-harvest losses and identify post-harvest pathogens associated with the decay of avocado fruits in Hossana town shops and a market which opens once a week. Random sampling method was used to select shops for survey and sample collection. Avocado fruits with different damage levels and disease symptoms were collected from 14 shops and the Hossana Market, packed using cartons then transported to the laboratory. A survey was conducted in selected shops and the market and identification of disease-causing pathogens was done through incubation of the samples taken from different parts of the fruits using potato dextrose agar (PDA) for seven days. Data was analyzed using SPSS, statistical software. Results from the survey revealed that postharvest loss of avocado varies across different post-harvest handling stages and the highest loss was recorded during storage (40%) followed by harvesting (26.7%). The most mechanical damage was observed in the MS shop (100%) followed by the HM (83.3%). This may be due to poor harvesting practices: unsuitable field or marketing containers and crates, which may have fractured wood, sharp edges, poor nailing or stapling. Disease incidence assessment showed that in three shops (AD2, MN2 and MS), 100% of fruits were infected. The highest disease severity index rated as 5 (>75%) was also observed in the same three shops (AD2, MN2 and MS) and the HM, followed by 3 shops (AD3, GM3 and NR) rated as 4 (51-75%). A total of 82 fungal colony growths were observed with Colletotrichum gloeosporioides being the most frequently isolated species (60 %) followed by Fusarium spp (26.67 %). Appropriate post-harvest handling technology and disease management strategy should be implemented from farm to fork to reduce post-harvest losses. Key words: Avocado, Colletotrichum gloeosporioides, Fungal Pathogens, Post-Harvest Loss, Public market, Ethiopia

Temporal variation of planetary iron as a driver of evolution

Iron is an irreplaceable component of proteins and enzyme systems required for life. This need for iron is a well-characterized evolutionary mechanism for genetic selection. However, there is limited consideration of how iron bioavailability, initially determined by planetary accretion but fluctuating considerably at global scale over geological time frames, has shaped the biosphere. We describe influences of iron on planetary habitability from formation events >4 Gya and initiation of biochemistry from geochemistry through oxygenation of the atmosphere to current host–pathogen dynamics. By determining the iron and transition element distribution within the terrestrial planets, planetary core formation is a constraint on both the crustal composition and the longevity of surface water, hence a planet’s habitability. As such, stellar compositions, combined with metallic core-mass fraction, may be an observable characteristic of exoplanets that relates to their ability to support life. On Earth, the stepwise rise of atmospheric oxygen effectively removed gigatons of soluble ferrous iron from habitats, generating evolutionary pressures. Phagocytic, infectious, and symbiotic behaviors, dating from around the Great Oxygenation Event, refocused iron acquisition onto biotic sources, while eukaryotic multicellularity allows iron recycling within an organism. These developments allow life to more efficiently utilize a scarce but vital nutrient. Initiation of terrestrial life benefitted from the biochemical properties of abundant mantle/crustal iron, but the subsequent loss of iron bioavailability may have been an equally important driver of compensatory diversity. This latter concept may have relevance for the predicted future increase in iron deficiency across the food chain caused by elevated atmospheric CO2.

Phyto-fabricated Nanoparticles and Their Anti-biofilm Activity: Progress and Current Status

Biofilm is the self-synthesized, mucus-like extracellular polymeric matrix that acts as a key virulence factor in various pathogenic microorganisms, thereby posing a serious threat to human health. It has been estimated that around 80% of hospital-acquired infections are associated with biofilms which are found to be present on both biotic and abiotic surfaces. Antibiotics, the current mainstream treatment strategy for biofilms are often found to be futile in the eradication of these complex structures, and to date, there is no effective therapeutic strategy established against biofilm infections. In this regard, nanotechnology can provide a potential platform for the alleviation of this problem owing to its unique size-dependent properties. Accordingly, various novel strategies are being developed for the synthesis of different types of nanoparticles. Bio-nanotechnology is a division of nanotechnology which is gaining significant attention due to its ability to synthesize nanoparticles of various compositions and sizes using biotic sources. It utilizes the rich biodiversity of various biological components which are biocompatible for the synthesis of nanoparticles. Additionally, the biogenic nanoparticles are eco-friendly, cost-effective, and relatively less toxic when compared to chemically or physically synthesized alternatives. Biogenic synthesis of nanoparticles is a bottom-top methodology in which the nanoparticles are formed due to the presence of biological components (plant extract and microbial enzymes) which act as stabilizing and reducing agents. These biosynthesized nanoparticles exhibit anti-biofilm activityviavarious mechanisms such as ROS production, inhibiting quorum sensing, inhibiting EPS production, etc. This review will provide an insight into the application of various biogenic sources for nanoparticle synthesis. Furthermore, we have highlighted the potential of phytosynthesized nanoparticles as a promising antibiofilm agent as well as elucidated their antibacterial and antibiofilm mechanism.

Succession, sources, and assembly of bacterial community in the developing crab larval microbiome

Molting to megalopa is a critical period that largely determines the success in culture of the swimming crab Portunus trituberculatus, an ecologically and economically important species throughout the temperate zone of the western Pacific Ocean. The microbiota may have a vital importance in the larval viability. However, the succession pattern, biotic sources, and assembly mechanism of crab larval bacterial community are still largely unknown. Here, we performed a temporal investigation of succession pattern, biotic sources, and assembly of the swimming crab larval bacterial community and its relationships with metabolites. Larval bacterial communities presented a dynamical change with crab development highlighted by the significantly decreased α-diversity and largely increased relative abundance of Rhodobacteraceae at the last zoeal stage. Although the indicator taxa showed comprehensive correlations with significantly changed cometabolites of larvae and their commensals, Rhodobacteraceae had less correlation with them. Furthermore, larval bacteria were distinct from rearing water bacterioplankton and primarily derived from internal sources mainly from larvae at the current stage via neutral processes including dispersal among individuals and ecological drift; notably, Rhodobacteraceae taxa were gained by the stochastic ecological processes. These results indicate that larval commensals especially Rhodobacteraceae is critical for the success of crab nursery and for microbial management in the cultivation of crab larvae.

Microbial effects on plant phenology and fitness.

Plant development and the timing of developmental events (phenology) are tightly coupled with plant fitness. A variety of internal and external factors determine the timing and fitness consequences of these life-history transitions. Microbes interact with plants throughout their life history and impact host phenology. This review summarizes current mechanistic and theoretical knowledge surrounding microbe-driven changes in plant phenology. Overall, there are examples of microbes impacting every phenological transition. While most studies have focused on flowering time, microbial effects remain important for host survival and fitness across all phenological phases. Microbe-mediated changes in nutrient acquisition and phytohormone signaling can release plants from stressful conditions and alter plant stress responses inducing shifts in developmental events. The frequency and direction of phenological effects appear to be partly determined by the lifestyle and the underlying nature of a plant-microbe interaction (i.e., mutualistic or pathogenic), in addition to the taxonomic group of the microbe (fungi vs. bacteria). Finally, we highlight biases, gaps in knowledge, and future directions. This biotic source of plasticity for plant adaptation will serve an important role in sustaining plant biodiversity and managing agriculture under the pressures of climate change.

Evolutionary rescue in host‐pathogen systems*

Natural populations encounter a variety of threats that can increase their risk of extinction. Populations can avoid extinction through evolutionary rescue (ER), which occurs when an adaptive, genetic response to selection allows a population to recover from an environmental change that would otherwise cause extinction. While the traditional framework for ER was developed with abiotic risk factors in mind, ER may also occur in response to a biotic source of demographic change, such as the introduction of a novel pathogen. We first describe how ER in response to a pathogen differs from the traditional ER framework; density-dependent transmission, pathogen evolution, and pathogen extinction can change the strength of selection imposed by a pathogen and make host population persistence more likely. We also discuss several variables that affect traditional ER (abundance, genetic diversity, population connectivity, and community composition) that also directly affect disease risk resulting in diverse outcomes for ER in host-pathogen systems. Thus, generalizations developed in studies of traditional ER may not be relevant for ER in response to the introduction of a pathogen. Incorporating pathogens into the framework of ER will lead to a better understanding of how and when populations can avoid extinction in response to novel pathogens.

Dancing in the Rain: How Do Abiotic Conditions Influence Sexually Selected Behaviors in the White-Ruffed Manakin?

Tropical animals respond to rainfall in population-specific ways. In extremely wet regions, endotherms experience heavy rains as stressors with consequences for behavior and demography. Ultimately, such stressors can affect the relative strength of abiotic selection, reducing the scope for sexual selection, and other biotic sources of selection. We studied population-level differences in the response to rainfall of White-ruffed manakins (Corapipo altera) on the Caribbean slope of Costa Rica, a species having a lek mating system subject to strong sexual selection. Between 2008 and 2013, we studied reproductive behavior in a population inhabiting an extremely wet site; estimates of apparent survival were low, and the turnover of display courts and dominant males was high. Males also engaged in coordinated display, and sub-adult males practiced in the presence of adults. Over three breeding seasons (2017-2019), we studied a population of the same species at a site only 110 km away, but in a location receiving roughly half as much rain. We tested behavioral predictions of three alternative mechanisms-indirect abiotic effects, direct mortality effects, and direct behavioral effects-linking rainfall to sexual selection in these two populations. Data derived from over 4300 h of observations at 105 display sites revealed high interannual variation in nearly all response variables, including turnover of display sites, retention of alpha status, male display behavior, and time females spent assessing male display. Additionally, we detected spatial differences in drivers of display site turnover. Notably, age distribution of males was skewed toward older individuals at the drier location. Based on these findings, we infer that indirect abiotic effects on forest structure leading to display site transience and direct effects of mortality increasing turnover in the male population likely underlie links between rain and the spatial and temporal differences we documented. Our results are consistent with rain constituting an important source of abiotic selection for tropical endotherms and modulating the scope for sexual selection near the extremes of a species' hygric niche.