Large-scale Biogeographic Patterns Research Articles

Phylogenetics and phylogeography of Euphorbia canariensis reveal an extreme Canarian-Asian disjunction but limited inter-island colonization.

Euphorbia canariensis is an iconic endemic species representative of the lowland xerophytic communities of the Canary Islands. It is widely distributed in the archipelago despite having diasporas unspecialized for long-distance dispersal. Here, we reconstructed the evolutionary history of E. canariensis at two levels: a time-calibrated phylogenetic analysis aimed at clarifying interspecific relationships and large-scale biogeographic patterns; and a phylogeographic study focused on the history of colonization across the Canary Islands. For the phylogenetic study, we sequenced the ITS region for E. canariensis and related species of Euphorbia sect. Euphorbia. For the phylogeographic study, we sequenced two cpDNA regions for 28 populations representing the distribution range of E. canariensis. The number of inter-island colonization events was explored using PAICE, a recently developed method that includes a sample size correction. Additionally, we used species distribution modelling (SDM) to evaluate environmental suitability for E. canariensis through time. Phylogenetic results supported a close relationship between E. canariensis and certain Southeast Asian species (E. epiphylloides, E. lacei, E. sessiliflora). In the Canaries, E. canariensis displayed a west-to-east colonization pattern, not conforming to the "progression rule", i.e. the concordance between phylogeographic patterns and island emergence times. We estimated between 20 and 50 inter-island colonization events, all of them in the Quaternary, and SDM suggested a late Quaternary increase in environmental suitability for E. canariensis. The extreme biogeographic disjunction between Macaronesia and Southeast Asia (ca. 11,000 km) parallels that found in a few other genera (Pinus, Dracaena). We hypothesize that these disjunctions are better explained by extinction across north Africa and southwest Asia rather than long-distance dispersal. The relatively low number of inter-island colonization events across the Canaries is congruent with the low dispersal capabilities of E. canariensis.

Potential present and future distributions of the genus Atta of Mexico.

Temperature and precipitation influence insect distribution locally and drive large-scale biogeographical patterns. We used current and future climate data from the CHELSA database to create ensemble species distribution models for three Atta leaf-cutting ant species (Atta cephalotes, A. mexicana, and A. texana) found in Mexico. These models were used to estimate the potential impact of climate change on the distribution of these species in the future. Our results show that bioclimatic variables influence the distribution of each Atta species occupying a unique climatic niche: A. cephalotes is affected by temperature seasonality, A. mexicana by isothermality, and A. texana by the minimum temperature of the coldest month. Atta texana and A. mexicana are expected to decline their range by 80% and 60%, respectively, due to rising temperatures, decreased rainfall, and increased drought. Due to rising temperatures and increased humidity, Atta cephalotes is expected to expand its range by 30%. Since Atta species are important pests, our coexistence with them requires knowledge of their ecological functions and potential future distribution changes. In addition, these insects serve as bioindicators of habitat quality, and they can contribute to the local economy in rural areas since they are eaten as food for the nutritional value of the queens. In this sense, presenting a future perspective of these species' distribution is important for forest and crop management. Education programs also are necessary to raise awareness of the importance of these ants and the challenges they face because of climate change. Our results offer a perspective of climate change studies to define conservation and adaptation strategies for protecting vulnerable areas such as high-elevation remnant forests.

Resurgence of warmth-demanding tree species and a common pending thermophilization in subalpine and northern boreal Sweden-an ecological signal of post-Little Ice Age climate improvement

Largely consistent with general predictions and earlier empirical studies, it appears that post-Little Ice Age climate warming has started to affect large-scale biogeographic patterns in northern Sweden. Long-term monitoring in subalpine and adjacent regions reveals sparse spread of broadleaved thermophilic tree species. Saplings of Quercus robur, Ulmus glabra, Acer platanoides, Alnus glutinosa and Betula pendula have responded to recent climate warming by jump-dispersal in the order of 50-300 km northwards and 500-800 m upwards, relative to their natural range limits. Consistent with treeline rise by boreal tree species, the thermophilies have reinvaded regions where they grew during the warmest phase of the Holocene, 9500-8000 years ago, but were subsequently extirpated by the Neoglacial cooling. Confined to the past 20 years or so, the unique observations of recent termophilies comply with background climate data, i.e. warming of all seasons. These results may contribute to more realistic vegetation models by stressing that the distributions of certain plant species are able to track climate warming without substantial migrational lag. Hitherto, vegetation and climate evolution appear to be well within the frames of natural dynamics during the postglacial era, although mechanisms may differ.

Bioluminescence in cephalopods: biodiversity, biogeography and research trends

Numerous terrestrial and marine organisms, including cephalopods, are capable of light emission. In addition to communication, bioluminescence is used for attraction and defense mechanisms. The present review aims to: (i) present updated information on the taxonomic diversity of luminous cephalopods and morphological features, (ii) describe large-scale biogeographic patterns, and (iii) show the research trends over the last 50 years on cephalopod bioluminescence. According to our database (834 species), 32% of all known cephalopod species can emit light, including oegopsid and myopsid squids, sepiolids, octopuses, and representatives of several other smaller orders (bathyteuthids, and the monotypic vampire “squid”, Vampyroteuthis infernalis and ram’s horn “squid”, Spirula spirula). Most species have a combination of photophores present in different locations, of which light organs on the head region are dominant, followed by photophores associated with the arms and tentacles and internal photophores. Regarding the biogeographic patterns of cephalopod species with light organs, the most diverse ocean is the Pacific Ocean, followed by the Atlantic and Indian Oceans. The least diverse are the Southern and the Arctic Oceans. Regarding publication trends, our systematic review revealed that, between 1971 and 2020, 277 peer-reviewed studies were published on bioluminescent cephalopods. Most research has been done on a single species, the Hawaiian bobtail squid Euprymna scolopes. The interest in this species is mostly due to its species-specific symbiotic relationship with the bacterium Vibrio fischeri, which is used as a model for the study of Eukaryote–Prokaryote symbiosis. Because there are many knowledge gaps about the biology and biogeography of light-producing cephalopods, new state-of-the-art techniques (e.g., eDNA for diversity research and monitoring) can help achieve a finer resolution on species’ distributions. Moreover, knowledge on the effects of climate change stressors on the bioluminescent processes is nonexistent. Future studies are needed to assess such impacts at different levels of biological organization, to describe the potential broad-scale biogeographic changes, and understand the implications for food web dynamics.

Genetic Analysis of Golden Eagles (Aquila chrysaetos) from the Mongol-Altai: A Hotspot of Diversity and Implications for Global Phylogeography

ABSTRACT The Golden Eagle (Aquila chrysaetos) is widely distributed in the northern Hemisphere and is thus an ideal candidate to explore large-scale biogeographic patterns. In recent years, Golden Eagle population genetics has gained considerable attention. However, the Eastern Palearctic region, a numerical stronghold for the species, is one of the least genetically studied regions within its geographic range. In West Mongolia, the Altai (Altay) Kazakhs collect wild Golden Eagle nestlings from eyries or trap juveniles and subadults on passage during seasonal movement and migration for traditional hunting, providing easy access for researchers to sample falconry eagles for population genetic analyses. We analyzed a 402-bp fragment of the mitochondrial control region and 14 nuclear microsatellite loci in combination with previously published genetic data to assess phylogeographic patterns, levels of genetic diversity, and fine-scale structuring of the Golden Eagle population within the Mongol-Altai Mountains. Golden Eagles in the Mongol-Altai Mountains exhibited overall high levels of genetic diversity. Mitochondrial DNA data across the species' geographic range reveal various stages of differentiation within the Holarctic clade: whereas divergence between the Western and Eastern Palearctic is relatively shallow, the Eastern Palearctic and Nearctic show a deeper divergence, although these geographic regions have not yet reached reciprocal monophyly. These patterns might reflect past climatic oscillations: Northern Europe may have been recolonized by Golden Eagles from the Eastern Palearctic region, and continental populations might still be connected by long-distance dispersers, but the Eastern Palearctic and Nearctic were likely connected via Beringia during the Quaternary and are today largely isolated from each other.

Increased bivalve cosmopolitanism during the mid-Phanerozoic mass extinctions

The impact of mass extinctions on biogeographic patterns remains unclear. Analysis of large-scale biogeographic patterns can provide insights into macroevolutionary processes. Here, we aim to trace the biogeographic dynamics of bivalves from the Middle Permian to the Early Jurassic based on an updated dataset, including 25,891 bivalve occurrence data, by using biogeographic connectedness (BC) and multiple-site β-diversity measures. The results reveal a significant bivalve cosmopolitanism event following the Permian–Triassic mass extinction (PTME) and a possible cosmopolitanism event after the Triassic–Jurassic mass extinction (TJME). Analysis of the BC of survivors and newcomers in each event reveals that both potential cosmopolitanism events were related to the selective extinction of endemic taxa, suggesting that endemics are more vulnerable during mass extinctions. The geographic expansion of survivors also possibly contributed to the cosmopolitanism in the aftermath of the PTME, supporting the ecological release hypothesis following the PTME. Finally, we found that the spatial sampling heterogeneity can bias biogeographic patterns, for instance, bivalve cosmopolitanism after the TJME.

Pattern of β-Diversity and Plant Species Richness along Vertical Gradient in Northwest Himalaya, India.

Simple SummaryElevation has a significant impact on the distribution of plant species. However, the structure and distribution patterns of Himalayan vegetation are poorly explored, and research on species composition along an elevation gradient in these mountain ranges is still deficient. Plant species richness is supposed to diminish with altitude, although numerous scientists have found a peak in species richness at mid-elevation, yielding a humped relationship. Many studies along the Himalayan altitudinal gradients have been conducted in order to better understand large-scale biogeographical patterns as well as what drives them, but no clear pattern has emerged. In order to understand how elevation affects plant species, we focused on species diversity, species composition and β-diversity, which allow for the interpreting of different patterns along the elevations. It was found that all these components of diversity vary significantly with the change in altitude.The structure and distribution patterns of Himalayan vegetation are poorly explored, and research on species composition along the elevation gradient in these mountain ranges is still deficient. The current study was undertaken to analyze the variation and pattern of plant species composition along a vertical gradient in northwestern Himalaya, India. A total of 18 sites were selected along an elevation gradient ranging from 2200 to 3900 m asl positioned at an interval of 100 m. The Renyi diversity profile, non-metric multidimensional scaling based on the Bray–Curtis dissimilarity metric and beta diversity components among the elevation belts were calculated. Furthermore, to study the influence of altitude on species richness and diversity, a generalized additive model was created. Two hundred and ten plant species representing 66 families and 147 genera were recorded. The Renyi diversity profiles show that the lower and mid-altitudes had rich species diversity. The results of the non-metric multidimensional scaling analysis show a considerable variation in the total plant species composition among the studied elevation belts. The observed multiple-site Sorensen dissimilarity index across the studied elevation belts was very high. The contribution of species replacement or the turnover component to the observed dissimilarity was much higher than the nestedness component. Furthermore, the herbaceous and tree richness showed a significant decrease with increase in elevation; however, the richness of shrubs showed a bimodal pattern. The present study increases our understanding of the trends and patterns of species richness along the vertical gradient in the Himalayan region.

Contrasting assembly mechanisms explain the biogeographic patterns of benthic bacterial and fungal communities on the Tibetan Plateau

The Tibetan Plateau characterized by high altitude and low temperature, where a great number of lakes are located, is a hotspot of global biodiversity research. Both bacterial and fungal communities are vital participants of biogeochemical cycling in lake ecosystems. However, we know very little about the large-scale biogeographic patterns and the underlying assembly mechanisms of lake benthic microbial communities on the Tibetan Plateau. To investigate the biogeographic patterns and their underlying assembly mechanisms of benthic bacterial and fungal communities, we collected sediment samples from 11 lakes on the Tibetan Plateau (maximum geographic distance between lakes over 1100 km). Benthic community diversity and composition were determined using the high-throughput sequencing technique. Our results indicated that there were contrasting distance-decay relationships between benthic bacterial and fungal communities on a regional scale. Benthic bacterial communities showed a significant distance-decay relationship, whereas no significant relationship was observed for benthic fungal communities. Deterministic processes dominated the bacterial community assembly, whereas fungal community assembly was more stochastic. pH was a dominant factor in influencing the geographic distribution of benthic microbial communities. Co-occurrence network analysis revealed that bacterial communities showed higher complexity and greater stability than those of the fungal communities. Taken together, this study contributes to a novel understanding of the assembly mechanisms underlying the biogeographic distribution of plateau benthic bacterial and fungal communities at a large scale.

Global analysis of floral longevity reveals latitudinal gradients and biotic and abiotic correlates.

The length of time a flower remains open and functional - floral longevity - governs important reproductive processes influencing pollination and mating and varies considerably among angiosperm species. However, little is known about large-scale biogeographic patterns and the correlates of floral longevity. Using published data on floral longevity from 818 angiosperm species in 134 families and 472 locations world-wide, we present the first global quantification of the latitudinal pattern of floral longevity and the relationships between floral longevity and a range of biotic and abiotic factors. Floral longevity exhibited a significant phylogenetic signal and was longer at higher latitudes in both northern and southern hemispheres, even after accounting for elevation. This latitudinal variation was associated with several biotic and abiotic variables. The mean temperature of the flowering season had the highest predictive power for floral longevity, followed by pollen number per flower. Surprisingly, compatibility status, flower size, pollination mode, and growth form had no significant effects on flower longevity. Our results suggest that physiological processes associated with floral maintenance play a key role in explaining latitudinal variation in floral longevity across global ecosystems, with potential implications for floral longevity under global climate change and species distributions.

Phylogeography and Prevalence of Hemoparasites (Apicomplexa: Eucoccidiorida) in Galápagos Marine Iguanas, Amblyrhynchus cristatus (Reptilia: Iguanidae).

Simple SummaryIt is estimated that a vast diversity of parasites populate our planet, many of them still to be discovered. Blood parasites (hemoparasites) of the phylum Apicomplexa may infect both vertebrates and invertebrates. Here, we used molecular methods to characterize the diversity of hemoparasites in the emblematic Galápagos marine iguana. We examined major island populations of marine iguanas across the Galápagos archipelago, performing the largest biogeographical study on the topic in this species. In addition, ticks were collected from marine iguana’s body to screen for hemoparasites. Our genetic analysis revealed two distinct clusters of hemoparasites belonging to Hepatozoon and/or Hemolivia. The occurrence of hemoparasites differed dramatically across islands, indicating that some populations may have mechanisms to reduce infection rates. The infection status of ticks did not match with their marine iguana hosts, suggesting that this method cannot be used to reliably know whether or not marine iguanas are infected. Given that apicomplexan blood parasites may cause important zoonotic diseases, studies like this one focusing on the relationship between parasites, their hosts and transmitting vectors, may help to shed light on the underlying mechanisms that wild animals employ to cope with pathogen infection. Parasitism is among the most common forms of coexistence of organisms of different species. Hemoparasites live in the bloodstream of the host where they complete different life-cycle stages. Members of the phylum Apicomplexa constitute a large portion of all hemoparasites infecting reptiles and their parasite transmitting vectors, including arthropods. In this study, we carried out a survey and molecular identification of hemoparasites in blood samples of the iconic Galápagos marine iguana (Amblyrhynchus cristatus). Major island populations of marine iguanas were sampled to examine large-scale biogeographic patterns of parasite diversity and prevalence. Nested PCRs were used to amplify segments of the 18S rRNA-gene of hemoparasites. Furthermore, ticks attached to marine iguanas were collected and analyzed in the same way to assess their potential use as a non-invasive method for the detection of hemoparasites in vertebrate host species. PCR products were sequenced and a phylogenetic analysis was carried out showing the presence of two genetically distinct clusters of hemoparasites, one more commonly distributed than the other one, belonging to the genera Hepatozoon and/or Hemolivia (Apicomplexa: Eucoccidiorida). Overall, 25% of marine iguanas were infected by hemoparasites. However, infection rates varied strongly among particular island populations (from 3.45% to 50%). Although marine iguanas are an extremely mobile species that has colonized all islands in the Galápagos archipelago, parasite occurrence was not related to geographical distance, suggesting that dispersal behavior has a minor role in parasite transmission. On most islands, females tended to have higher infection rates than males, but this relationship was only significant on one island. Overall, ticks and marine iguanas had similar prevalence and diversity of parasites. However, the infection profiles of ticks and their corresponding hosts (marine iguanas) did not mirror one another, indicating that this method cannot be used reliably to assess marine iguana infection status. Interestingly, we found that hemoparasite prevalence in marine iguanas and ticks tended to be positively correlated across islands. Our results indicate that certain populations of marine iguanas may have special mechanisms and adaptations to cope with parasite infection. In addition, other factors such as vector density, anthropogenic-related activities or the immunological state of marine iguanas could potentially affect the striking variation in hemoparasite prevalence across island populations.

Large-scale biogeographic patterns are reflected in the genetic structure of a broadcast spawning stony coral

Countries in the Western Indian Ocean (WIO) and along the Red Sea are particularly vulnerable to coral reef degradation, and understanding the degree of connectivity among coral reefs is a first step toward efficient conservation. The aim of this study is to investigate the genetic diversity, population structure and connectivity patterns of the broadcast spawning coral Acropora tenuis, first at a large scale comparing the Red Sea and the WIO, and second at a smaller scale comparing sites within the WIO. In total 689 individual A. tenuis colonies were sampled on 28 locations in Saudi Arabia, Kenya, Tanzania, Mozambique and Madagascar and analysed with seven microsatellite markers. The sample site in the Red Sea was found to be differentiated from all other sites in the WIO, which confirms the hypothesised genetic break. High differentiation was found between the African mainland and Madagascar and within Madagascar. However, there is evidence for long-distance larval dispersal for A. tenuis in the North Mozambique Channel region, with exchange between northern Mozambique and northern Madagascar. The sites in the southwest of Madagascar show mixing with sites in northern Madagascar, as well as exchange with sites in northern Mozambique and Tanzania. Southern Mozambique forms a separate group in Bayesian clustering. High genetic connectivity was found for most sites along the East African mainland coast, with no indication for strict genetic barriers. These results support biophysical modelling studies, which propose Tanzania as a seeding source of larvae for downstream Kenya. These patterns of high genetic connectivity combined with contemporary dispersal barriers can be explained by the long larval duration of A. tenuis and the prevailing northbound East African Coast Current that facilitates higher genetic connectivity along the northern East African Coast, while eddies in the Mozambique Channel are causing larval retention in southern Mozambique and Madagascar.

Biogeography of soil protistan consumer and parasite is contrasting and linked to microbial nutrient mineralization in forest soils at a wide-scale

Despite their essential role in soil microbiome and the global ecological processes, large-scale biogeographical patterns and predictors of protists are poorly characterized. Investigating the diversity and distribution of protists is crucial for understanding their biogeographic patterns and underlying the drivers across phylogenetic, ecological, and functional scales. Here, we explored a wide-scale pattern of protistan communities, and linked it with soil functions, in 107 soil samples from nine forest sites along a large climatic gradient. Our results showed that the biogeography of protistan communities in forest soils generally fitted the temperature diversity gradients (TDG), metabolic niche theory (MNT) and distance-decay relationships (DDR). Strikingly, the dominant protistan phyla, Cercozoa (consumer) and Apicomplexa (parasite), followed highly different/contrasting biogeographic patterns along the climatic gradient, as a result of environmental selection and stochastic processes. Cercozoa were relatively more abundant in cold arid soils while Apicomplexa thrived in tropical wet sites. Homogenizing dispersal had a stronger effect on the distribution of the Cercozoa, while ecological drift controlled the distribution of the Apicomplexa. In addition, we found that protist network modularization explained 57.5% of the variation in soil nutrient mineralization, suggesting the critical roles of Cercozoa and Apicomplexa in nutrient cycling. Collectively, we showed the general applicability of TDG, MNT and DDR to the soil protistan communities and revealed contrasting biogeographic patterns of protistan consumer and parasite along climatic gradients. Our study highlights the crucial contribution of protistan communities to nutrient mineralization in forest soils.

Large-scale biogeographical patterns of antibiotic resistome in the forest soils across China

Soil is a reservoir of environmental resistomes. Information about their distribution, profiles, and driving forces in undisturbed environments is essential for understanding and managing modern antibiotic resistance genes (ARGs) in human disturbed environments. However, knowledge about the resistomes in pristine soils is limited, particularly at national scale. Here, we conducted a national-scale investigation of soil resistomes in pristine forests across China. Although the antibiotics content was low and ranged from below limit of detection (LOD) to 0.290 μg/kg, numerous detected ARGs conferring resistance to major classes of modern antibiotics were identified and indicated forest soils as a potential source of resistance traits. ARGs ranged from 6.20 × 10−7 to 2.52 × 10−3 copies/16S-rRNA and were predominated by those resisting aminoglycoside and encoding deactivation mechanisms. Low abundance of mobile genetic elements (MGEs) and its scarcely positive connections with ARGs suggest the low potential of horizontal gene transfer. The geographic patterns of ARGs and ARG-hosts in pristine forest soils were mainly driven by soil physiochemical variables and followed a distance–decay relationship. This work focusing on pristine soils can provide valuably new information for our understanding of the ARGs in human disturbed environments.

Temperature and salinity, not acidification, predict near-future larval growth and larval habitat suitability of Olympia oysters in the Salish Sea

Most invertebrates in the ocean begin their lives with planktonic larval phases that are critical for dispersal and distribution of these species. Larvae are particularly vulnerable to environmental change, so understanding interactive effects of environmental stressors on larval life is essential in predicting population persistence and vulnerability of species. Here, we use a novel experimental approach to rear larvae under interacting gradients of temperature, salinity, and ocean acidification, then model growth rate and duration of Olympia oyster larvae and predict the suitability of habitats for larval survival. We find that temperature and salinity are closely linked to larval growth and larval habitat suitability, but larvae are tolerant to acidification at this scale. We discover that present conditions in the Salish Sea are actually suboptimal for Olympia oyster larvae from populations in the region, and that larvae from these populations might actually benefit from some degree of global ocean change. Our models predict a vast decrease in mean pelagic larval duration by the year 2095, which has the potential to alter population dynamics for this species in future oceans. Additionally, we find that larval tolerance can explain large-scale biogeographic patterns for this species across its range.

A hairy situation: Plant species in warm, sunny places are more likely to have pubescent leaves

AbstractAimLeaf pubescence has several important roles, including regulating heat balance, reducing damage from UV radiation, minimizing water loss and reducing herbivory. Each of these functions could affect a plant's ability to tolerate the biotic and abiotic stresses encountered in different parts of the world. However, we know remarkably little about large scale biogeographic patterns in leaf pubescence. Our aims were: (a) to determine whether a higher proportion of species have pubescence at sites where it is hot, dry and solar radiation is high, and (b) to quantify the latitudinal gradient in pubescence.LocationAustralia.TaxonVascular land plants.MethodsWe compiled data on the presence/absence of pubescence on mature photosynthetic organs for 4,183 species, spanning 107 families. We combined these data with over 1.9 million species occurrence records from the Atlas of Living Australia to calculate the proportion of species with pubescence in 3,261 grid cells spanning the Australian continent.ResultsThe proportion of pubescent species was most closely related to solar radiation (R2 = 0.33), followed by maximum temperature in the warmest month (R2 = 0.30). Mean annual precipitation was very weakly related to pubescence (R2 = 0.01). We found a significant negative relationship between latitude and pubescence (R2 = 0.19), with the average percentage of species with pubescence dropping from 46% at 10° S to 35% at 44° S. This cross‐species relationship remained significant after accounting for phylogenetic relationships between species. We found that a quadratic model explained more variation in pubescence across latitudes than did a linear model. The quadratic model shows a peak in the proportion of pubescent species at 19° S (within the tropics).Main conclusionsOur findings are consistent with the idea that leaf pubescence may have a protective function in areas with high solar radiation and high temperatures. Our data are also consistent with the idea that species towards the tropics should be better defended than are species at higher latitudes.

Predation shapes invertebrate diversity in tropical but not temperate seagrass communities.

The hypothesis that biotic interactions are stronger at lower relative to higher latitudes has a rich history, drawing from ecological and evolutionary theory. While this hypothesis suggests that stronger interactions at lower latitudes may contribute to the maintenance of contemporary patterns of diversity, there remain few standardized biogeographic comparisons of community effects of species interactions. Using marine seagrasses as a focal ecosystem of conservation importance and sessile marine invertebrates as model prey, we tested the hypothesis that predation is stronger at lower latitudes and can shape contemporary patterns of prey diversity. To further advance understanding beyond prior studies, we also explored mechanisms that likely underlie a change in interaction outcomes with latitude. Multiple observational and experimental approaches were employed to test for effects of predators, and the mechanisms that may underlie these effects, in seagrass ecosystems of the western Atlantic Ocean spanning 30° of latitude from the temperate zone to the tropics. In predator exclusion experiments conducted in a temperate and a tropical region, predation decreased sessile invertebrate abundance, richness and diversity on both natural and standardized artificial seagrass at tropical but not temperate sites. Further, predation reduced invertebrate richness at both local and regional scales in the tropics. Additional experiments demonstrated that predation reduced invertebrate recruitment in the tropics but not the temperate zone. Finally, direct observations of predators showed higher but variable consumption rates on invertebrates at tropical relative to temperate latitudes. Together, these results demonstrate that strong predation in the tropics can have consequential impacts on prey communities through discrete effects on early life stages as well as longer-term cumulative effects on community structure and diversity. Our detailed experiments also provide some of the first data linking large-scale biogeographic patterns, community-scale interaction outcomes and direct observation of predators in the temperate zone and tropics. Therefore, our results support the hypothesis that predation is stronger in the tropics, but also elucidate some of the causes and consequences of this variation in shaping contemporary patterns of diversity.

Adaptation to the abiotic environment in insects: the influence of variability on ecophysiology and evolutionary genomics.

Advances in tools to gather environmental, phenotypic, and molecular data have accelerated our ability to detect abiotic drivers of variation across the genome-to-phenome spectrum in model and non-model insects. However, differences in the spatial and temporal resolution of these data sets may create gaps in our understanding of linkages between environment, genotype, and phenotype that yield missed or misleading results about adaptive variation. In this review we highlight sources of variability that might impact studies of phenotypic and 'omic environmental adaptation, challenges to collecting data at relevant scales, and possible solutions that link intensive fine-scale reductionist studies of mechanisms to large-scale biogeographic patterns.

Family-level leaf nitrogen and phosphorus stoichiometry of global terrestrial plants.

Leaf nitrogen (N) and phosphorus (P) concentrations are critical for photosynthesis, growth, reproduction and other ecological processes of plants. Previous studies on large-scale biogeographic patterns of leaf N and P stoichiometric relationships were mostly conducted using data pooled across taxa, while family/genus-level analyses are rarely reported. Here, we examined global patterns of family-specific leaf N and P stoichiometry using a global data set of 12,716 paired leaf N and P records which includes 204 families, 1,305 genera, and 3,420 species. After determining the minimum size of samples (i.e., 35 records), we analyzed leaf N and P concentrations, N:P ratios and N∼P scaling relationships of plants for 62 families with 11,440 records. The numeric values of leaf N and P stoichiometry varied significantly across families and showed diverse trends along gradients of mean annual temperature (MAT) and mean annual precipitation (MAP). The leaf N and P concentrations and N:P ratios of 62 families ranged from 6.11 to 30.30 mg g-1, 0.27 to 2.17 mg g-1, and 10.20 to 35.40, respectively. Approximately 1/3-1/2 of the families (22-35 of 62) showed a decrease in leaf N and P concentrations and N:P ratios with increasing MAT or MAP, while the remainder either did not show a significant trend or presented the opposite pattern. Family-specific leaf N∼P scaling exponents did not converge to a certain empirical value, with a range of 0.307-0.991 for 54 out of 62 families which indicated a significant N∼P scaling relationship. Our results for the first time revealed large variation in the family-level leaf N and P stoichiometry of global terrestrial plants and that the stoichiometric relationships for at least one-third of the families were not consistent with the global trends reported previously. The numeric values of the family-specific leaf N and P stoichiometry documented in the current study provide critical synthetic parameters for biogeographic modeling and for further studies on the physiological and ecological mechanisms underlying the nutrient use strategies of plants from different phylogenetic taxa.

The terrestrial invertebrate fauna of Edge\xf8ya, Svalbard: Arctic landscape community composition reflects biogeography patterns

Colonisation and immigration history is often neglected as a factor when investigating community or species distribution patterns. However, for dynamic systems that are still reacting to large-scale environmental change, such as the retreat of the ice since the last glacial maximum, colonisation history may explain a large amount of the variation between geographically distinct communities. The High Arctic archipelago of Svalbard presents an opportunity to test whether it is possible to observe the effects of large-scale biogeographical patterns on species distribution at landscape scales. Svalbard has one of the best described inventories of the invertebrate fauna in the Arctic. Nonetheless, the majority of the species records originate from the more accessible west coast and the invertebrate fauna of the whole eastern region, including Edgeøya, is virtually unknown. Edgeøya is located at the eastern fringe of the archipelago on the boundary between Palaearctic and Nearctic faunas. It was expected that post-colonisation dispersal within Edgeøya would conceal routes to the archipelago. Samples were obtained from six locations along the coast of Edgeøya between 2009 and 2010. 140 invertebrate species were identified belonging to 69 different genera of which 16 are new records for Svalbard. Most new species present an eastern Palaearctic distribution. Habitat variables (percentage cover of moss, lichen, vascular plant, or bare soil) fail to explain 35.5% of the differences among sites. However, cluster analysis reveals a clear east–west distribution pattern across the island suggesting that pan-Arctic dispersal routes can be identified even at relatively short geographical scales.

Distinct large-scale biogeographic patterns of fungal communities in bulk soil and soybean rhizosphere in China

Fungi play a crucial role in the agroecological system; however, little is known about their large-scale biogeographical patterns and how various ecological processes contribute to community assembly, especially in the crop rhizosphere. In this study, we investigated the spatial distribution and community assembly of fungi in the bulk soil and rhizosphere of soybean collected from 43 sites across China using high-throughput sequencing. The alpha diversity of the rhizosphere was lower than that of bulk soil. The fungal community structures of the two soil compartments were distinct. Fungal communities in the rhizosphere had a steeper distance-decay relationship slope between sampled sites than those in bulk soil, suggesting a greater influence of historical processes (geographical separation) in the rhizosphere. The relative importance of dispersal limitation and environmental filtering for the fungal community composition differed between bulk soil and rhizosphere. Sloan neutral model analysis suggested that niche-based processes dominated the assemblage of fungal communities in the two soil compartments, while neutral processes had a weaker influence in the rhizosphere than in bulk soil. Additionally, we analyzed the structures of abundant and rare fungal sub-communities in each soil compartment. Rare sub-communities were more strongly influenced by dispersal limitation than abundant sub-communities. These results expand the current understanding of root-associated fungal community biogeography in agricultural soils on a large scale.