Mean reef fish body size decreases towards warmer waters.

Aquatic ectotherms often attain smaller body sizes at higher temperatures. By analysing ~15,000 coastal-reef fish surveys across a 15°C spatial sea surface temperature (SST) gradient, we found that the mean length of fish in communities decreased by ~5% for each 1°C temperature increase across space, or 50% decrease in mean length from 14 to 29°C mean annual SST. Community mean body size change was driven by differential temperature responses within trophic groups and temperature-driven change in their relative abundance. Herbivores, invertivores and planktivores became smaller on average in warmer temperatures, but no trend was found in piscivores. Nearly 25% of the temperature-related community mean size trend was attributable to trophic composition at the warmest sites, but at colder temperatures, this was <1% due to trophic groups being similarly sized. Our findings suggest that small changes in temperature are associated with large changes in fish community composition and body sizes, with important ecological implications.

How many animal-pollinated angiosperms are nectar-producing?

The diversity of plant-pollinator interactions is grounded in floral resources, with nectar considered one of the main floral rewards plants produce for pollinators. However, a global evaluation of the number of animal-pollinated nectar-producing angiosperms and their distribution world-wide remains elusive. We compiled a thorough database encompassing 7621 plant species from 322 families to estimate the number and proportion of nectar-producing angiosperms reliant on animal pollination. Through extensive sampling of plant communities, we also explored the interplay between nectar production, floral resource diversity, latitudinal and elevational gradients, contemporary climate, and environmental characteristics. Roughly 223 308 animal-pollinated angiosperms are nectar-producing, accounting for 74.4% of biotic-pollinated species. Global distribution patterns of nectar-producing plants reveal a distinct trend along latitudinal and altitudinal gradients, with increased proportions of plants producing nectar in high latitudes and altitudes. Conversely, tropical communities in warm and moist climates exhibit greater floral resource diversity and a lower proportion of nectar-producing plants. These findings suggest that ecological trends driven by climate have fostered the diversification of floral resources in warmer and less seasonal climates, reducing the proportion of solely nectar-producing plants. Our study provides a baseline for understanding plant-pollinator relationships, plant diversification, and the distribution of plant traits.

The global distribution of angiosperm genome size is shaped by climate.

Angiosperms, which inhabit diverse environments across all continents, exhibit significant variation in genome sizes, making them an excellent model system for examining hypotheses about the global distribution of genome size. These include the previously proposed large genome constraint, mutational hazard, polyploidy-mediated, and climate-mediated hypotheses. We compiled the largest genome size dataset to date, encompassing 16 017 (> 5% of known) angiosperm species, and analyzed genome size distribution using a comprehensive geographic distribution dataset for all angiosperms. We observed that angiosperms with large range sizes generally had small genomes, supporting the large genome constraint hypothesis. Climate was shown to exert a strong influence on genome size distribution along the global latitudinal gradient, while the frequency of polyploidy and the type of growth form had negligible effects. In contrast to the unimodal patterns along the global latitudinal gradient shown by plant size traits and polyploid proportions, the increase in angiosperm genome size from the equator to 40-50°N/S is probably mediated by different (mostly climatic) mechanisms than the decrease in genome sizes observed from 40 to 50°N northward. Our analysis suggests that the global distribution of genome sizes in angiosperms is mainly shaped by climatically mediated purifying selection, genetic drift, relaxed selection, and environmental filtering.

Latitudinal trends in an invasive plant: genetic differentiation, phenotypic plasticity, and the effects of heavy metals and herbivores on growth, defence, and reproductive characteristics.

BACKGROUND AND AIMS: Invasive species usually demonstrate remarkable adaptability across diverse environments, successfully inhabiting a wide variety of regions. This adaptability often links to genetic differentiation and phenotypic plasticity, leading to latitudinal trends in phenotypic traits. In this study, we collected seeds of invasive plant Phytolacca americana from different latitudes and planted them in homogeneous gardens to investigate the latitudinal variation of P. americana phenotypic traits and to evaluate the effects of herbivory and heavy metals on plant growth, defence, and reproductive characteristics. METHODS: P. americana seeds from different latitudes were planted in a homogeneous garden. For the experimental treatment, the seeds were divided into four groups: a heavy metal treatment group and its corresponding control group, and a cover treatment group with its corresponding control group. After the fruits matured, their growth, reproduction, and defence indicators were measured. KEY RESULTS: Significant latitudinal trends were observed in P. americana's growth and defence characteristics, including changes in branch number, underground biomass, total biomass, and leaf tannin content. Compared to previous field surveys on P. americana, our study found that the latitude trends in growth structure and defence traits were consistent. But the latitudinal trend of reproductive structure is different. Moreover, heavy metals and herbivory substantially influenced the plant's growth, reproduction, and defence mechanisms, further shaping its latitudinal patterns. CONCLUSIONS: The observed phenotypic variations in P. americana across latitudes can be largely attributed to the synergistic effects of phenotypic plasticity and genetic variation. At a broader geographical scale, adaptations to heavy metal stress and herbivory pressure among different P. americana populations involve distinct trade-offs related to growth, reproduction, and defence strategies.

Investigating historical drivers of latitudinal gradients in polyploid plant biogeography: A multiclade perspective.

PREMISE: The proportion of polyploid plants in a community increases with latitude, and different hypotheses have been proposed about which factors drive this pattern. Here, we aimed to understand the historical causes of the latitudinal polyploidy gradient using a combination of ancestral state reconstruction methods. Specifically, we assessed whether (1) polyploidization enables movement to higher latitudes (i.e., polyploidization precedes occurrences in higher latitudes) or (2) higher latitudes facilitate polyploidization (i.e., occurrence in higher latitudes precedes polyploidization). METHODS: We reconstructed the ploidy states and ancestral niches of 1032 angiosperm species at four paleoclimatic time slices ranging from 3.3 million years ago to the present, comprising taxa from four well-represented clades: Onagraceae, Primulaceae, Solanum (Solanaceae), and Pooideae (Poaceae). We used ancestral niche reconstruction models alongside a customized discrete character evolution model to allow reconstruction of states at specific time slices. Patterns of latitudinal movement were reconstructed and compared in relation to inferred ploidy shifts. RESULTS: No single hypothesis applied equally well across all analyzed clades. While significant differences in median latitudinal occurrence were detected in the largest clade, Poaceae, no significant differences were detected in latitudinal movement in any clade. CONCLUSIONS: Our preliminary study is the first to attempt to connect ploidy changes to continuous latitudinal movement, but we cannot favor one hypothesis over another. Given that patterns seem to be clade-specific, more clades must be analyzed in future studies for generalities to be drawn.

Winter Tracking Data Suggest that Migratory Seabirds Transport Per- and Polyfluoroalkyl Substances to Their Arctic Nesting Site.

Seabirds are often considered sentinel species of marine ecosystems, and their blood and eggs utilized to monitor local environmental contaminations. Most seabirds breeding in the Arctic are migratory and thus are exposed to geographically distinct sources of contamination throughout the year, including per- and polyfluoroalkyl substances (PFAS). Despite the abundance and high toxicity of PFAS, little is known about whether blood concentrations at breeding sites reliably reflect local contamination or exposure in distant wintering areas. We tested this by combining movement tracking data and PFAS analysis (nine compounds) from the blood of prelaying black-legged kittiwakes (Rissa tridactyla) nesting in Arctic Norway (Svalbard). PFAS burden before egg laying varied with the latitude of the wintering area and was negatively associated with time upon return of individuals at the Arctic nesting site. Kittiwakes (n = 64) wintering farther south carried lighter burdens of shorter-chain perfluoroalkyl carboxylates (PFCAs, C9-C12) and heavier burdens of longer chain PFCAs (C13-C14) and perfluorooctanesulfonic acid compared to those wintering farther north. Thus, blood concentrations prior to egg laying still reflected the uptake during the previous wintering stage, suggesting that migratory seabirds can act as biovectors of PFAS to Arctic nesting sites.

Global warming is causing a more pronounced dip in marine species richness around the equator.

The latitudinal gradient in species richness, with more species in the tropics and richness declining with latitude, is widely known and has been assumed to be stable over recent centuries. We analyzed data on 48,661 marine animal species since 1955, accounting for sampling variation, to assess whether the global latitudinal gradient in species richness is being impacted by climate change. We confirm recent studies that show a slight dip in species richness at the equator. Moreover, richness across latitudinal bands was sensitive to temperature, reaching a plateau or declining above a mean annual sea surface temperature of 20 °C for most taxa. In response, since the 1970s, species richness has declined at the equator relative to an increase at midlatitudes and has shifted north in the northern hemisphere, particularly among pelagic species. This pattern is consistent with the hypothesis that climate change is impacting the latitudinal gradient in marine biodiversity at a global scale. The intensification of the dip in species richness at the equator, especially for pelagic species, suggests that it is already too warm there for some species to survive.

Intra and interspecific variation in thermal performance and critical limits in anurans from southern Chile.

The relationship between temperature and performance can be illustrated through a thermal performance curve (TPC), which has proven useful in describing various aspects of ectotherms' thermal ecology and evolution. The parameters of the TPC can vary geographically due to large-scale variations in environmental conditions. However, only some studies have attempted to quantify how thermal performance varies over relatively small spatial scales, even in the same location or consistently among individuals within a species. Here, we quantified individual and species variation in thermal sensitivity of locomotor performance in five amphibia Eupsophus species found in the temperate rainforests of southern Chile and compared their estimates against co-occurring species that exhibit a substantially more extensive distributional range. We measured critical thermal limits and jumping performance under five different temperatures. Our results suggest that thermal responses are relatively conserved along the phylogeny, as the locomotor performance and thermal windows for activity remained narrow in Eupsophus species when compared against results observed for Batrachyla taeniata and Rhinella spinulosa. Additionally, we found significant individual differences in locomotor performance within most species, with individual consistency in performance observed across varied temperatures. Further analyses explored the influence of body size on locomotor performance and critical thermal limits within and between species. Our results suggest a trade-off scenario between thermal tolerance breadth and locomotor performance, where species exhibiting broader thermal ranges might have compromised performance. Interestingly, these traits seem partly mediated by body size variations, raising questions about potential ecological implications.

Genetic control underlying the flowering-drought tolerance trade-off in the Antarctic plant Colobanthus quitensis.

Plants inhabiting environments with stressful conditions often exhibit a low number of flowers, which can be attributed to the energetic cost associated with reproduction. One of the most stressful environments for plants is the Antarctic continent, characterized by limited soil water availability and low temperatures. Induction of dehydrins like those from the COR gene family and auxin transcriptional response repressor genes (IAAs), which are involved in floral repression, has been described in response to water stress. Here, we investigated the relationship between the water deficit-induced stress response and the number of flowers in Colobanthus quitensis plants collected from populations along a latitudinal gradient. The expression levels of COR47 and IAA12 genes in response to water deficit were found to be associated with the number of flowers. The relationship was observed both in the field and growth chambers. Watering the plants in the growth chambers alleviated the stress and stimualted flowering, thereby eliminating the trade-off observed in the field. Our study provides a mechanistic understanding of the ecological constraints on plant reproduction along a water availability gradient. However, further experiments are needed to elucidate the primary role of water availability in regulating resource allocation to reproduction in plants inhibiting extreme environments.

Archaeal and Bacterial Diversity and Distribution Patterns in Mediterranean-Climate Vernal Pools of Mexico and the Western USA.

Biogeographic patterns in microorganisms are poorly understood, despite the importance of microbial communities for a range of ecosystem processes. Our knowledge of microbial ecology and biogeography is particularly deficient in rare and threatened ecosystems. We tested for three ecological patterns in microbial community composition within ephemeral wetlands-vernal pools-located across Baja California (Mexico) and California (USA): (1) habitat filtering; (2) a latitudinal diversity gradient; and (3) distance decay in community composition. Paired water and soil samples were collected along a latitudinal transect of vernal pools, and bacterial and archaeal communities were characterized using 16S rDNA sequencing. We identified two main microbial communities, with one community present in the soil matrix that included archaeal and bacterial soil taxa, and another community present in the overlying water that was dominated by common freshwater bacterial taxa. Aquatic microbial communities were more diverse in the north, and displayed a significant but inverted latitudinal diversity pattern. Aquatic communities also exhibited a significant distance-decay pattern, with geographic proximity, and precipitation explaining part of the community variation. Collectively these results indicate greater sensitivity to spatial and environmental variation in vernal pool aquatic microbial communities than in soil microbial communities. We conclude that vernal pool aquatic microbial communities can display distribution patterns similar to those exhibited by larger organisms, but differ in some key aspects, such as the latitudinal gradient in diversity.

Similar regional-scale survival of tropical and southern temperate birds from the New World.

The general assumption that the survival patterns of tropical and southern temperate birds are similar lacks empirical data from higher latitudes. Regional comparisons of New World species are rare, and this assumption has been based on data from African studies. Here, we estimate the survival rates of 88 tropical and southern temperate bird populations (69 species) from eight localities in South America to evaluate the hypothesis that the survival of these populations is homogeneous at the regional scale. We estimated survival based on the Cormack-Jolly-Seber model and compared values from different environments. The survival estimates ranged from 0.30 to 0.80 (0.56 ± 0.12). Apparent survival did not differ significantly between low-latitude tropical environments (03°S) and the other sites from high-latitudes (between 22° and 34°S). Despite a predicted positive trend, body size was not significantly related to survival among passerines. On the other hand, phylogenetic relationships explained more than a third of the variation in bird survival. Based on the largest available database on South American bird species, our findings support the hypothesis that bird survival is homogeneous, at the regional scale, along the southern hemisphere. In particular, we reinforce the hypothesis that climatic variation has a limited influence on bird survival in the southern hemisphere.

Geographic variation in the life history of lane snapper Lutjanus synagris, with new insights from the warm edge of its distribution.

Research on life-history variations in widely distributed fish species is needed to understand global warming impacts on populations and to improve fisheries management advice. The lane snapper Lutjanus synagris (Linnaeus, 1758) is commercially important to fisheries in the Western Central Atlantic, where spread information on its life-history traits is available. We studied growth, age, reproduction and mortality of lane snapper in the Guatemalan Caribbean, the warmest part of its distribution range, and collated the new information with published data in a latitudinal analysis extending between 18°S and 30°N. Longevity was estimated at 11 years, and von Bertalanffy growth parameters were asymptotic length (Linf) 45.6 and 42.2 cm for females and males, respectively, the growth coefficient (K) was 0.1 year-1 and the theoretical age at zero length (t0 ) was -4.4 years. Lane snapper grew slowest in April, prior to the rainy season, and at the onset of the reproductive season, which lasted from May to October. Fifty percent of female and male lane snappers matured at 23 and 17 cm, corresponding to 3.5 and 2.4 years of age respectively. A regional multivariate analysis found seawater temperature to be an important driver of life-history variation. Lane snapper lifespan was shorter at the warm edge of its distribution range, and maximum size and peak reproductive investment were negatively related to sea surface temperature. The trade-offs in lane snapper life-history traits and phenology likely enhance its fitness to differing environments. Interpolation from the present regional estimates to less-studied regions of the Caribbean is useful for preliminary understanding of reaction norms and harvest potentials.

The latitudinal gradient in plant community assembly processes: A meta-analysis.

Beta(ß)-diversity, or site-to-site variation in species composition, generally decreases with increasing latitude, and the underlying processes driving this pattern have been challenging to elucidate because the signals of community assembly processes are scale-dependent. In this meta-analysis, by synthesising the results of 103 studies that were distributed globally and conducted at various spatial scales, we revealed a latitudinal gradient in the detectable assembly processes of vascular plant communities. Variations in plant community composition at low and high latitudes were mainly explained by geographic variables, suggesting that distance decay and dispersal limitations causing spatial aggregation are influential in these regions. In contrast, variation in species composition correlated most strongly with environmental variables at mid-latitudes (20-30°), reflecting the importance of environmental filtering, although this unimodal pattern was not statistically significant. Importantly, our analysis revealed the effects of different spatial scales, such that the correlation with spatial variables was stronger at smaller sampling extents, and environmental variables were more influential at larger sampling extents. We concluded that plant communities are driven by different community assembly processes in distinct biogeographical regions, suggesting that the latitudinal gradient of biodiversity is created by a combination of multiple processes that vary with environmental and species size differences.

Dietary abundance distributions: Dominance and diversity in vertebrate diets.

Diet composition is among the most important yet least understood dimensions of animal ecology. Inspired by the study of species abundance distributions (SADs), we tested for generalities in the structure of vertebrate diets by characterising them as dietary abundance distributions (DADs). We compiled data on 1167 population-level diets, representing >500 species from six vertebrate classes, spanning all continents and oceans. DADs near-universally (92.5%) followed a hollow-curve shape, with scant support for other plausible rank-abundance-distribution shapes. This strong generality is inherently related to, yet incompletely explained by, the SADs of available food taxa. By quantifying dietary generalisation as the half-saturation point of the cumulative distribution of dietary abundance (sp50, minimum number of foods required to account for 50% of diet), we found that vertebrate populations are surprisingly specialised: in most populations, fewer than three foods accounted for at least half the diet. Variation in sp50 was strongly associated with consumer type, with carnivores being more specialised than herbivores or omnivores. Other methodological (sampling method and effort, taxonomic resolution), biological (body mass, frugivory) and biogeographic (latitude) factors influenced sp50 to varying degrees. Future challenges include identifying the mechanisms underpinning the hollow-curve DAD, its generality beyond vertebrates, and the biological determinants of dietary generalisation.

An ancient positively selected BMPRIB missense variant increases litter size of Mongolian sheep populations following latitudinal gradient.

New gene mutation origination is a driving force for the evolution of organisms. The effect of FecB mutation in BMPRIB gene on the litter size of sheep has been well known for a long time, each copy of the mutant allele increases litter size by 0.4-0.5. However, the origin and adaptive evolution mechanism of FecB mutation are still unclear. Here we carried on the thorough analysis on evolutionary features of BMPRIB gene and found that 150 species as a whole is under purifying selection while sheep lineage shows evidence of positive selection. The results of allele age estimation revealed that the FecB mutation in Mongolian sheep of China originated in Mongolian Plateau at about 5000 years ago. Due the two shape drops in temperature subsequently, Mongolian sheep migrated from north to south following the northern nomadic people. Accordingly, the FecB mutant allele frequency increased, with the lowest in sheep locating at Mongolian plateau (0.01) and the highest in sheep locating at Yangtze River valley (0.96). In conclusion, the FecB mutation in Mongolian sheep of China originated in Mongolian Plateau at about 5000 years ago, and the differentiated litter size of Mongolian sheep might be the result of adaptation to various environments during the migration following latitudinal gradient. This study may well exemplify selection on an ancient variation triggered by drastic ecological shifts, and is also helpful to analyze the adaptive evolution mechanism of economic traits of domestic animals and identify major genes and molecular markers.

The biogeography of community assembly: latitude and predation drive variation in community trait distribution in a guild of epifaunal crustaceans.

While considerable evidence exists of biogeographic patterns in the intensity of species interactions, the influence of these patterns on variation in community structure is less clear. Studying how the distributions of traits in communities vary along global gradients can inform how variation in interactions and other factors contribute to the process of community assembly. Using a model selection approach on measures of trait dispersion in crustaceans associated with eelgrass (Zostera marina) spanning 30° of latitude in two oceans, we found that dispersion strongly increased with increasing predation and decreasing latitude. Ocean and epiphyte load appeared as secondary predictors; Pacific communities were more overdispersed while Atlantic communities were more clustered, and increasing epiphytes were associated with increased clustering. By examining how species interactions and environmental filters influence community structure across biogeographic regions, we demonstrate how both latitudinal variation in species interactions and historical contingency shape these responses. Community trait distributions have implications for ecosystem stability and functioning, and integrating large-scale observations of environmental filters, species interactions and traits can help us predict how communities may respond to environmental change.

Decoding the dynamics of dental distributions: insights from shark demography and dispersal.

Shark teeth are one of the most abundant vertebrate fossils, and because tooth size generally correlates with body size, their accumulations document the size structure of populations. Understanding how ecological and environmental processes influence size structure, and how this extends to influence these dental distributions, may offer a window into the ecological and environmental dynamics of past and present shark populations. Here, we examine the dental distributions of sand tigers, including extant Carcharias taurus and extinct Striatolamia macrota, to reconstruct the size structure for a contemporary locality and four Eocene localities. We compare empirical distributions against expectations from a population simulation to gain insight into potential governing ecological processes. Specifically, we investigate the influence of dispersal flexibility to and from protected nurseries. We show that changing the flexibility of initial dispersal of juveniles from the nursery and annual migration of adults to the nursery explains a large amount of dental distribution variability. Our framework predicts dispersal strategies of an extant sand tiger population, and supports nurseries as important components of sand tiger life history in both extant and Eocene populations. These results suggest nursery protection may be vital for shark conservation with increasing anthropogenic impacts and climate change.

Influence of delayed density and ultraviolet radiation on caterpillar baculovirus infection and mortality.

Infectious disease is an important potential driver of population cycles but must occur through delayed density-dependent infection and resulting fitness effects. Delayed density-dependent infection by baculoviruses can be caused by environmental persistence of viral occlusion bodies (OBs), which can be influenced by environmental factors. Specifically, ultraviolet radiation is potentially important in reducing the environmental persistence of viruses by inactivating OBs. Delayed density-dependent viral infection has rarely been observed empirically at the population level although theory predicts that it is necessary for pathogens to drive population cycles. Similarly, field studies have not examined the effects of ultraviolet radiation on viral infection rates in natural animal populations. We tested if viral infection is delayed density-dependent with the potential to drive cyclic dynamics and if ultraviolet radiation influences viral infection levels. We censused 18 Ranchman's tiger moth (Arctia virginalis) populations across 9° of latitude over 2 years and quantified the effects of direct and delayed density and ultraviolet radiation on proportion infected by baculovirus, infection severity and survival to adulthood. Caterpillars were collected from field populations and reared in the laboratory. Baculovirus has not previously been described infecting A. virginalis, and we used genetic methods to confirm the identity of the virus. We found that proportion infected, infection severity and survival to adulthood exhibited delayed density dependence. Ultraviolet radiation in the previous summer decreased infection severity, which increased caterpillar survival probability. Structural equation modelling indicated that the effect of lagged density on caterpillar survival was mediated through proportion infected and infection severity and was 2.5-fold stronger than the indirect effect of ultraviolet. We successfully amplified polh, lef-8 and lef-9 viral genes from caterpillars, and BLAST results confirmed that the virus was a nucleopolyhedrovirus. Our findings provide clear evidence that delayed density-dependent mortality can arise through viral infection rate and severity in insects, which supports the role of viral disease as a mechanism, among others, that may drive insect population cycles. Furthermore, our findings support predictions that ultraviolet radiation can modify viral disease dynamics in insect populations, most likely through attenuating viral persistence in the environment.

Reduced pollinator service in small populations of Arabidopsis lyrata at its southern range limit.

Even though a high fraction of angiosperm plants depends on animal pollinators for sexual reproduction, little is known how pollinator service changes across the ranges of plant species and whether it may contribute to range limits. Here, we tested for variation in pollinator service in the North American Arabidopsis lyrata from its southern to northern range edge and evaluated the driving mechanisms. We monitored insect pollinators using time-lapse cameras in 13 populations over two years and spotted 67 pollinating insect taxa, indicating the generalist nature of this plant-pollinator system. Pollinator service was highest at intermediate local flower densities and higher in large compared to small plant populations. Southern populations had generally smaller population sizes, and visitation rate and pollination ratio decreased with latitude. We also found that pollinator visitation was positively correlated with the richness of other flowering plants. This study indicates that plant populations at southern range edges receive only marginal pollinator service if they are small, and the effect of lower pollination is also detectable within populations across the range when the local flower density is low. Results, therefore, suggest the potential for an Allee effect in pollination that manifests itself across spatial scales.

Latitudinal patterns of terrestrial phosphorus limitation over the globe.

Phosphorus limitation on terrestrial plant growth is being incorporated into Earth system models. The global pattern of terrestrial phosphorus limitation, however, remains unstudied. Here, we examined the global-scale latitudinal pattern of terrestrial phosphorus limitation by analysing a total of 1068 observations of aboveground plant production response to phosphorus additions at 351 forest, grassland or tundra sites that are distributed globally. The observed phosphorus-addition effect varied greatly (either positive or negative), depending significantly upon fertilisation regime and production measure, but did not change significantly with latitude. In contrast, phosphorus-addition effect standardised by fertilisation regime and production measure was consistently positive and decreased significantly with latitude. Latitudinal gradient in the standardised phosphorus-addition effect was explained by several mechanisms involving substrate age, climate, vegetation type, edaphic properties and biochemical machinery. This study suggests that latitudinal pattern of terrestrial phosphorus limitation is jointly shaped by macro-scale driving forces and the fundamental structure of life.