Phylogenetic Generalized Least Squares Research Articles

Phylogenetic conservation in plant phenological traits varies between temperate and subtropical climates in China

Phenological traits, such as leaf and flowering dates, are proven to be phylogenetically conserved. The relationship between phylogenetic conservation, plant phenology, and climatic factors remains unknown. Here, we assessed phenological features among flowering plants as evidence for phylogenetic conservatism, the tendency for closely related species to share similar ecological and biological attributes. We use spring phenological traits data from 1968-2018 of 65 trees and 49 shrubs in Xi’an (temperate climate) and Guiyang (subtropical climate) to understand plant phenological traits’ relationship with phylogeny. Molecular datasets are employed in evolutionary models to test the phylogenetic conservatism in spring phenological characteristics in response to climate-sensitive phenological features. Significant phylogenetic conservation was found in the Xi’an plant’s phenological traits, while there was a non-significant conservation in the Guiyang plant species. Phylogenetic generalized least squares (PGLS) models correlate with phenological features significantly in Xi’an while non-significantly in Guiyang. Based on the findings of molecular dating, it was suggested that the Guiyang species split off from their relatives around 46.0 mya during the middle Eocene of the Tertiary Cenozoic Era, while Xi’an species showed a long evolutionary history and diverged from their relatives around 95 mya during the late Cretaceous Mesozoic Era. First leaf dates (FLD) indicative of spring phenology, show that Xi’an adjourned the case later than Guiyang. Unlike FLD, first flower dates (FFD) yield different results as Guiyang flowers appear later than Xi’an’s. Our research revealed that various factors, including phylogeny, growth form, and functional features, influenced the diversity of flowering phenology within species in conjunction with local climate circumstances. These results are conducive to understanding evolutionary conservation mechanisms in plant phenology concerning evolutionary processes in different geographical and climate zones.

Revisiting niche divergence hypothesis in sexually dimorphic birds: Is diet overlap correlated with sexual size dimorphism?

The evolution of sexual size dimorphism (SSD) is a long-standing topic in evolutionary biology, but there is little agreement on the extent to which SSD is driven by the different selective forces. While sexual selection and fecundity selection have traditionally been proposed as the two leading hypotheses, SSD may also result from natural selection through mechanisms such as sexual niche divergence, which might have reduced resource competition between sexes. Here, we revisited the niche divergence hypothesis by testing the relationship between the sexual overlap in diet and SSD of 56 bird species using phylogenetic comparative analyses. We then assessed how SSD variation relates to the three main hypotheses: sexual selection, fecundity selection, and sexual niche divergence using phylogenetic generalized least squares (PGLS). Then, we compared sexual selection, fecundity selection and niche divergence selection as SSD drivers through phylogenetic confirmatory path analyses to disentangle the possible causal evolutionary relationships between SSD and the three hypotheses. Phylogenetic generalized least squares showed that SSD was negatively correlated with diet overlap, that is, the greater the difference in body size between males and females, the less diet overlap. As predicted by sexual selection theory, the difference in body size between sexes was higher in polygynous species. Confirmatory phylogenetic path analyses suggested that the most likely evolutionary path might include the mating system as a main driver in SSD and niche divergence as a result of SSD. We found no evidence of a role of fecundity selection in the evolution of female-biased SSD. Our study provides evidence that sexual selection has likely been the main cause of SSD and that dietary divergence is likely an indirect effect of SSD.

Phylogenetically conservative trait correlation: Quantification and interpretation

Abstract Correlation across species between two quantitative traits, or between a trait and a habitat property, can suggest that a trait value is effective in sustaining populations in some contexts but not others. It is widely held that such correlations should be controlled for phylogeny, via phylogenetically independent contrasts (PICs) or phylogenetic generalized least squares (PGLS). A weakness of this idea is that a clade's traits tend to confer success in particular habitats or ways of life, and those niches in turn tend to select for the same traits to continue in the clade. This feedback mechanism can bind phylogeny and niche together as a unified cause for present‐day trait configurations. Accordingly, the phylogenetically conservative share of a trait correlation ought not to be excluded from consideration as potentially ecologically functional. Another weakness is that PGLS does not yield a complete or accurate breakdown of covariation between traits A and B because it corresponds to a generating model where B predicts variation in A but not the reverse, and phylogenetic signal in B is not modelled. Multi‐response mixed models using phylogenetic covariance matrices can quantify conservative trait correlation (CTC), a share of A‐B covariation that is phylogenetically conservative. Because the evidence is from correlative data, it is not possible to split CTC into causation by phylogenetic history versus causation by continuing reciprocal selection between A and B. Moreover, it is quite likely biologically that the two influences have acted in concert, through phylogenetic niche conservatism. Synthesis: The CTC concept treats phylogenetic conservatism as a conjoint interpretation alongside ongoing influence of other traits. CTC can be quantified via multi‐response phylogenetic mixed models.

Updated imaging and phylogenetic comparative methods reassess relative temporal lobe size in anthropoids and modern humans.

Two decades ago, Rilling and Seligman, hereafter abbreviated to RAS Study, suggested modern humans had relatively larger temporal lobes for brain size compared to other anthropoids. Despite many subsequent studies drawing conclusions about the evolutionary implications for the emergence of unique cerebral specializations in Homo sapiens, no re-assessment has occurred using updated methodologies. We reassessed the association between right temporal lobe volume (TLV) and right hemisphere volume (HV) in the anthropoid brain. In a sample compiled de novo by us, T1-weighted in vivo Magnetic Resonance Imaging (MRI) scans of 11 extant anthropoid species were calculated by-voxel from the MRI and the raw data from RAS Study directly compared to our sample. Phylogenetic Generalized Least-Squares (PGLS) regression and trait-mapping using Blomberg's K (kappa) tested the correlation between HV and TLV accounting for anthropoid phylogeny, while bootstrapped PGLS regressions tested difference in slopes and intercepts between monkey and ape subsamples. PGLS regressions indicated statistically significant correlations (r2  < 0.99; p ≤ 0.0001) between TLV and HV with moderate influence from phylogeny (K ≤ 0.42). Bootstrapped PGLS regression did not show statistically significant differences in slopes between monkeys and apes but did for intercepts. In our sample, human TLV was not larger than expected for anthropoids. Updated imaging, increased sample size and advanced statistical analyses did not find statistically significant results that modern humans possessed a disproportionately large temporal lobe volume compared to the general anthropoid trend. This has important implications for human and non-human primate brain evolution.

Robustness of Bergmann’s and Rapoport’s rules to different geographical range estimates in New World pit vipers

AbstractAimBergmann's and Rapoport's rules are two ecogeographical patterns that predict an increase in species body size and range size, respectively, with increasing latitudes. Here, we evaluated whether using different geographical range estimates affects the assessment of Bergmann's and Rapoport's rules at the cross‐species and assemblage levels in New World pit vipers.LocationNew World.TaxonNew World pit vipers (Crotalinae).MethodsWe estimated geographical ranges for 135 (i.e. ≈93%) Crotalinae species using ecological niche modelling (ENM) and expert maps and assessed alternative hypotheses that could account for Bergmann's and Rapoport's rules. We evaluated both rules using ‘cross‐species’ (i.e. species as units of observation) and ‘assemblage’ (i.e. sites/grid cells as units of observation) approaches. We used phylogenetic generalized least squares (PGLS) analyses and generalized least squares (GLS) analyses to account for phylogenetic and spatial autocorrelation that could affect the evaluation of these rules at the cross‐species and assemblage levels, respectively.ResultsExpert maps differed significantly from ENM ranges. The cross‐species approach was robust to these different range estimates when Bergmann's and Rapoport's rules were evaluated. The assemblage analyses were more vulnerable to different range estimates, where contrasting results were observed in the assessment of Bergmann's rule but not in the evaluation of Rapoport's rule.Main ConclusionsDifferent geographical range estimates affected mainly the assessment of ecogeographical rules at the assemblage level, whereas the cross‐species analyses were more robust. However, this increased susceptibility of the assemblage approach to different range estimates was only observed when evaluating Bergmann's rule. Thus, our findings suggest that ecogeographical rules can have different levels of sensitivity to different range estimates, which can especially affect the assemblage‐level assessment of these ecogeographical patterns.

Chew on this: Oral jaw shape is not correlated with diet type in loricariid catfishes.

The correlation between form and function is influenced by biomechanical constraints, natural selection, and ecological interactions. In many species of suction-feeding fishes, jaw shape has shown to be closely associated with diet. However, these correlations have not been tested in fishes that have more complex jaw functions. For example, the neotropical loricariid catfishes possess a ventrally facing oral disk, which allows for the oral jaws to adhere to surfaces to conduct feeding. To determine if jaw shape is correlated to diet type, we assessed oral jaw shape across 36 species using CT scans. Shape was quantified with traditional and automated landmarking in 3DSlicer, and diet type correlation was calculated using the phylogenetic generalized least squares (PGLS) method. We found that traditional and automated processes captured shape effectively when all jaw components were combined. PGLS found that diet type did not correlate to jaw shape; however, there was a correlation between clades with diverse diets and fast evolutionary rates of shape. These results suggest that shape is not constrained to diet type, and that similarly shaped jaws coupled with different types of teeth could allow the fishes to feed on a wide range of materials.

Is Poaceae pollen size a useful proxy in palaeoecological studies? New insights from a Poaceae pollen morphological study in the Amazon

Poaceae (the grass family) is highly diverse, geographically widespread, and an important component of many terrestrial ecosystems. Poaceae pollen size has previously been suggested as a proxy to reconstruct the past vegetation and climates in the Amazon area, but it is still unclear if this variable can be used at broader spatial and deep-time scales. Here we set out to perform a comprehensive assessment and to test the robustness of this proxy. We generated pollen size data, as well as associated measurements of the pollen wall and pore, using 127 plant specimens from 58 species across the Poaceae phylogeny from the Amazon drainage basin (ADB). We tested the relationship between pollen size and a range of abiotic and biotic variables (vegetation type, soil composition, climate conditions, photosynthetic pathway and genome size), and fitted models using phylogenetic generalized least squares (P-GLS) and linear mixed models (LMM). Our measurement data shows that Poaceae pollen size presents a very wide range (18.77–71.62 μm), and varies not only among genera and species but also within species. There is no obvious relationship between pollen size and the explanatory variables considered here. We suggest that pollen size cannot be used as generally applicable proxy to reconstruct past vegetation and climate.

The evolutionary drivers of primate scleral coloration

The drivers of divergent scleral morphologies in primates are currently unclear, though white sclerae are often assumed to underlie human hyper-cooperative behaviours. Humans are unusual in possessing depigmented sclerae whereas many other extant primates, including the closely-related chimpanzee, possess dark scleral pigment. Here, we use phylogenetic generalized least squares (PGLS) analyses with previously generated species-level scores of proactive prosociality, social tolerance (both n = 15 primate species), and conspecific lethal aggression (n = 108 primate species) to provide the first quantitative, comparative test of three existing hypotheses. The ‘self-domestication’ and ‘cooperative eye’ explanations predict white sclerae to be associated with cooperative, rather than competitive, environments. The ‘gaze camouflage’ hypothesis predicts that dark scleral pigment functions as gaze direction camouflage in competitive social environments. Notably, the experimental evidence that non-human primates draw social information from conspecific eye movements is unclear, with the latter two hypotheses having recently been challenged. Here, we show that white sclerae in primates are associated with increased cooperative behaviours whereas dark sclerae are associated with reduced cooperative behaviours and increased conspecific lethal violence. These results are consistent with all three hypotheses of scleral evolution, suggesting that primate scleral morphologies evolve in relation to variation in social environment.

Glaucoma through Animal's Eyes: Insights from the Evolution of Intraocular Pressure in Mammals and Birds.

Glaucoma, an eye disorder caused by elevated intraocular pressure (IOP), is the leading cause of irreversible blindness in humans. Understanding how IOP levels have evolved across animal species could shed light on the nature of human vulnerability to glaucoma. Here, we studied the evolution of IOP in mammals and birds and explored its life history correlates. We conducted a systematic review, to create a dataset of species-specific IOP levels and reconstructed the ancestral states of IOP using three models of evolution (Brownian, Early burst, and Ornstein-Uhlenbeck (OU)) to understand the evolution of glaucoma. Furthermore, we tested the association between life history traits (e.g., body mass, blood pressure, diet, longevity, and habitat) and IOP using phylogenetic generalized least squares (PGLS). IOP in mammals and birds evolved under the OU model, suggesting stabilizing selection toward an optimal value. Larger mammals had higher IOPs and aquatic birds had higher IOPs; no other measured life history traits, the type of tonometer used, or whether the animal was sedated when measuring IOP explained the significant variation in IOP in this dataset. Elevated IOP, which could result from physiological and anatomical processes, evolved multiple times in mammals and birds. However, we do not understand how species with high IOP avoid glaucoma. While we found very few associations between life history traits and IOP, we suggest that more detailed studies may help identify mechanisms by which IOP is decoupled from glaucoma. Importantly, species with higher IOPs (cetaceans, pinnipeds, and rhinoceros) could be good model systems for studying glaucoma-resistant adaptations.

Comparative digestive morphology and physiology of five species of Peromyscus under controlled environment and diet

Digestive morphology and physiology differ across animal species, with many comparative studies uncovering relationships between animal ecology or diet, and the morphology and physiology of the gastrointestinal tract. However, many of these studies compare wild-caught animals feeding on uncontrolled diets and compare broadly related taxa. Thus, few studies have disentangled the phenotypic consequences of genetics from those potentially caused by the environment, especially across closely related species that occupy similar ecological niches. Here, we examined differences in digestive morphology and physiology of five closely related species of Peromyscus mice that were captive bred under identical environmental conditions and identical diets for multiple generations. Using phylogenetic generalized least squares (PGLS) of species means to control for body size, we identified a phylogenetic signal in the mass of the foregut and length of the small intestine across species. As proportions of total gut mass, we identified phylogenetic signals in relative foregut and small intestine masses, indicating that the sizes of these structures are more similar among closely related species. Finally, we detected differences in activities of the protease aminopeptidase-N enzyme across species. Overall, we demonstrate fine-scale differences in digestive morphology and physiology among closely related species. Our results suggest that Peromyscus could provide a system for future studies to explore the interplay between natural history, morphology, and physiology (e.g. ecomorphology and ecophysiology), and to investigate the genetic architecture that underlies gut anatomy.

Phylogenetic signal of sub‐arctic beetle communities

Postglacial dispersal and colonization processes have shaped community patterns in sub‐Arctic regions such as Churchill, Manitoba, and Canada. This study investigates evolutionary community structure within the beetle (Coleoptera) families of Churchill and tests whether biological traits have played a role in governing colonization patterns from refugial and southerly geographic regions. This study quantifies sub‐Arctic beetle phylogenetic community structure for each family using the net relatedness index (NRI) and nearest taxon index (NTI), calculated using publicly available data from the Barcode of Life Data Systems (BOLD); compares patterns across families with different traits (habitat, diet) using standard statistical analysis (ANOVA) as well as phylogenetic generalized least squares (PGLS) using a family‐level beetle phylogeny obtained from the literature; and compares community structure in Churchill with a region in southern Canada (Guelph, Ontario). These analyses were also repeated at a genus level. The dominant pattern detected in our study was that aquatic families were much better represented in Churchill compared to terrestrial families, when compared against richness sampled from across Canada and Alaska. Individually, most families showed significant phylogenetic clustering in Churchill, likely due to the strong environmental filtering present in Arctic environments. There was no significant difference in phylogenetic structure between Churchill and Guelph but with a trend toward stronger clustering in the North. Fungivores were significantly more overdispersed than other feeding modes, predators were significantly more clustered, and aquatic families showed significantly stronger clustering compared to terrestrial. This study contributes to our understanding of the traits and processes structuring insect biodiversity and macroecological trends in the sub‐Arctic.

横断山区龙蜥属(Diploderma)物种生境偏好和形态分化

PDF HTML阅读 XML下载 导出引用 引用提醒 横断山区龙蜥属(Diploderma)物种生境偏好和形态分化 DOI: 10.5846/stxb202104160986 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 生态环境部"生物多样性调查与评估"项目（2019HJ2096001006）；第二次青藏高原综合科学考察研究项目（2019QZKK04020202，2019QZKK050100503） Habitat preference and morphological differentiation of Diploderma in Hengduan Mountainous Region Author: Affiliation: Fund Project: The Biodiversity Survey and Assessment Project of the Ministry of Ecology and Environment, China (2019HJ2096001006) to Yin QI and Feng XIE. The Second Tibetan Plateau Scientific Expedition and Research Program (2019QZKK04020202, 2019QZKK050100503). 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:横断山区是全球25个生物多样性热点之一，其生态安全和生物多样性保护备受国内外关注。经济社会发展给横断山区特有龙蜥属动物带来许多新的挑战，大量原始生境被道路修建和水电工程彻底破坏，有些物种甚至在局部地区灭绝。因此及时开展龙蜥保护生态学相关研究，对准确制定保护行动计划非常关键。生境偏好与形态分化是保护生态学研究的重要内容。采用样线和样方法，对横断山区9个龙蜥属物种生境因子进行了测量。同时借助野外标本采集和标本馆标本测量，对19个龙蜥属物种进行了形态量化。采用广义线性混合模型（Generalized Linear Mixed Model，GLMM）和基于系统发育的广义最小二乘法（Phylogenetic Generalized Least-Squares，PGLS）对龙蜥生境偏好和形态学分化进行了分析。结果表明，来自不同生境的龙蜥对生境因子具有特殊的偏好。灌丛型龙蜥更偏好石块灌丛、阳坡、较陡、平均石块粒径较大、温度适中的生境，偏好生境中往往有两头毛（Incarvillea arguta）分布；林地型龙蜥偏好乔木、较陡的上坡位和植被覆盖率高的生境，偏好生境中往往有红花羊蹄甲（Bauhinia×blakeana）分布。从形态分化方面看，灌丛型和林地型龙蜥在体型大小和运动形态方面均发生了明显地分化，对雄性而言，林地型龙蜥尾长、鼻眼距、第4指长以及第4趾爪长大于灌丛型龙蜥，而灌丛型龙蜥吻长和胫骨长大于林地型龙蜥。对雌性而言，尾长、头长、吻长、鼻眼距、第4指长、第4趾长以及第4趾爪长均为林地型龙蜥大于灌丛型。研究为横断山区龙蜥生境偏好和形态分化提供了直接证据，有助于理解龙蜥对干热河谷生境的适应策略，同时为科学制定龙蜥保护计划提供重要支撑。 Abstract:Hengduan Mountainous Region (HMR) is one of the top 25th biodiversity hotspots in the world, and its ecological security and biodiversity conservation have increasingly attracted much attention from China and other countries. Economic and social development has brought many new challenges to the survival of Diploderma, the endemic species of the HMR. The original habitats of several Diploderma species have completely been destroyed because of road construction and hydropower projects, and what made us worrying was some species that have become extinct in local areas. Therefore, timely research on the conservation ecology of Diploderma is very important and urgent to the design of conservation plan. Habitat preference and morphological differentiation are important contents of conservation ecology research. In this study, the habitat factors including habitat type, vegetation coverage, vegetation height, stone size, distance road, interference factor, slope direction, slope position, gradient, temperature, and humidity of 9 Diploderma species in HMR were measured by line and square to transect. At the same time, the morphological characters of 19 Diploderma species were quantified using field sampling and herbarium specimen. Habitat preference and morphological differentiation were analyzed using Generalized Linear Mixed Model (GLMM) and Phylogenetic Generalized least-squares (PGLS). The results showed that Diploderma from different habitat types had special preferences for habitat factors. The species distributed in shrub preferred the habitats with stone, brush, steeper sunny slopes, large stone size, and suitable temperature (25-35℃), with Incarvillea arguta. The species distributed in forest preferred the habitats with big trees, steeper hill and high vegetation coverage, with Bauhinia×blakeana. Our results also showed much differentiation in body size and locomotion characters between shrub-type and forest-type lizard. For males, forest distributing species possessed large size in tail length, nose-eye distance, 4th finger length and claw length of the 4th toe compared with shrub distribution species, meanwhile snout length and shin length were just the opposite. While for females, forest distribution species possessed large size in tail length, head length, snout length, nose-eye distance, 4th finger length, 4th toe length and claw length of the 4th toe compared with shrub distribution species. Taken together, our study provides direct evidence for habitat preference and morphological differentiation of the endemic lizards' species in HMR, while it would greatly contribute to the understanding of adaptation tactics towards the dry-hot valley habitat in Diploderma, as well as provide important support for the design of conservation plan. 参考文献 相似文献 引证文献

Foraging strategies, craniodental traits, and interaction in the bite force of Neotropical frugivorous bats (Phyllostomidae: Stenodermatinae).

Bats in the family Phyllostomidae exhibit great diversity in skull size and morphology that reflects the degree of resource division and ecological overlap in the group. In particular, the subfamily Stenodermatinae has high morphological diversification associated with cranial and mandibular traits that are associated with the ability to consume the full range of available fruits (soft and hard).We analyzed craniodental traits and their relationship to the bite force in 343 specimens distributed in seven species of stenodermatine bats with two foraging strategies: nomadic and sedentary frugivory. We evaluated 19 traits related to feeding and bite force in live animals by correcting bite force with body size.We used a generalized linear model (GLM) and post hoc tests to determine possible relationships and differences between cranial traits, species, and sex. We also used Blomberg's K to measure the phylogenetic signal and phylogenetic generalized least‐squares (PGLS) to ensure the phylogenetic independence of the traits.We found that smaller nomadic species, A. anderseni and A. phaeotis , have a similar bite force to the large species A. planirostris and A. lituratus; furthermore, P. helleri registered a bite force similar to that of the sedentary bat, S. giannae. Our study determined that all the features of the mandible and most of the traits of the skull have a low phylogenetic signal. Through the PGLS, we found that the diet and several cranial features (mandibular toothrow length, dentary length, braincase breadth, mastoid breadth, greatest length of skull, condylo‐incisive length, and condylo‐canine length) determined bite force performance among Stenodermatiane.Our results reinforce that skull size is a determining factor in the bite force, but also emphasize the importance of its relationships with morphology, ecology, and phylogeny of the species, which gives us a better understanding of the evolutionary adaptions of this highly diverse Neotropical bat group.

Climatic-niche evolution with key morphological innovations across clades within Scutiger boulengeri (Anura: Megophryidae).

The studies of climatic‐niche shifts over evolutionary time accompanied by key morphological innovations have attracted the interest of many researchers recently. We applied ecological niche models (ENMs), ordination method (environment principal component analyses; PCA‐env), combined phylogenetic comparative methods (PCMs), and phylogenetic generalized least squares (PGLS) regression methods to analyze the realized niche dynamics and correspondingly key morphological innovations across clades within Scutiger boulengeri throughout their distributions in Qinghai–Tibet Plateau (QTP) margins of China. Our results show there are six clades in S. boulengeri and obvious niche divergences caused by niche expansion in three clades. Moreover, in our system, niche expansion is more popular than niche unfilling into novel environmental conditions. Annual mean temperature, annual precipitation, and precipitation of driest month may contribute to such a shift. In addition, we identified several key climatic factors and morphological traits that tend to be associated with niche expansion in S. boulengeri clades correspondingly. We found phenotypic plasticity [i.e., length of lower arm and hand (LAHL), hind‐limb length (HLL), and foot length (FL)] and evolutionary changes [i.e., snout–vent length (SVL)] may together contribute to niche expansion toward adapting novel niche, which provides us a potential pattern of how a colonizing toad might seed a novel habitat to begin the process of speciation and finally adaptive radiation. For these reasons, persistent phylogeographic divisions and accompanying divergences in niche occupancy and morphological adaption suggest that for future studies, distinct genetic structure and morphological changes corresponding to each genetic clade should be included in modeling niche evolution dynamics, but not just constructed at the species level.

Body size variation in polyplacophoran molluscs: Geographical clines and community structure along the south‐eastern Pacific

AbstractAimTo evaluate the latitudinal pattern of body size within and among chiton species employing phylogenetically structured analyses and examine the role ofgeographical variation in temperature, productivity and oxygen availability as potential environmental drivers.LocationCoastal habitats of the south‐eastern Pacific along a latitudinal range of nearly 6,000 km, from the equator to Patagonia (c. 2° to 56° S).Time periodPresent (2011–2017).Major taxa studiedThirty‐one species of polyplacophoran molluscs.MethodsWe measured the body length of 6,162 individuals collected in 62 sites, and reconstructed the phylogeny of this group based on two mitochondrial and one nuclear gene regions. We combined this information with data of sea surface temperature, chlorophyll‐a concentration—as a proxy of primary productivity—and dissolved oxygen, and assessed which variables best explain the variation in size both within and among species employing phylogenetic generalized least squares (PGLS) and a model comparison approach.Main conclusionsOur analyses show that body size increases consistently with latitude, both within and among species, following Bergmann’s rule. Variation in sea surface temperature along the latitudinal gradient provided a substantially better fit than chlorophyll‐a and dissolved oxygen. Our results support the temperature–size rule for this lineage and suggest that similar processes could underlie the emergence of intra‐ and interspecific gradients in body size of polyplacophorans. At the community level, chiton species richness was higher at intermediate latitudes and positively correlated with body size variation, suggesting that heterogeneity in size may reduce interspecific competition and contribute to species coexistence in this group. Overall, our study demonstrates that historical events, macroecological adaptive trends and local processes at the community level contribute to the distribution and size variation of polyplacophoran species throughout the south‐eastern Pacific.

Genomic insights into body size evolution in Carnivora support Peto\u2019s paradox

BackgroundThe range of body sizes in Carnivora is unparalleled in any other mammalian order—the heaviest species is 130,000 times heavier than the lightest and the longest species is 50 times longer than the shortest. However, the molecular mechanisms underlying these huge differences in body size have not been explored.ResultsHerein, we performed a comparative genomics analysis of 20 carnivores to explore the evolutionary basis of the order’s great variations in body size. Phylogenetic generalized least squares (PGLS) revealed that 337 genes were significantly related to both head body length and body mass; these genes were defined as body size associated genes (BSAGs). Fourteen positively-related BSAGs were found to be associated with obesity, and three of these were under rapid evolution in the extremely large carnivores, suggesting that these obesity-related BSAGs might have driven the body size expansion in carnivores. Interestingly, 100 BSAGs were statistically significantly enriched in cancer control in carnivores, and 15 of which were found to be under rapid evolution in extremely large carnivores. These results suggested that large carnivores might have evolved an effective mechanism to resist cancer, which could be regarded as molecular evidence to support Peto’s paradox. For small carnivores, we identified 15 rapidly evolving genes and found six genes with fixed amino acid changes that were reported to reduce body size.ConclusionsThis study brings new insights into the molecular mechanisms that drove the diversifying evolution of body size in carnivores, and provides new target genes for exploring the mysteries of body size evolution in mammals.

Morphological convergence and adaptation in cave and pelagic scale worms (Polynoidae, Annelida)

Across Annelida, accessing the water column drives morphological and lifestyle modifications—yet in the primarily “benthic” scale worms, the ecological significance of swimming has largely been ignored. We investigated genetic, morphological and behavioural adaptations associated with swimming across Polynoidae, using mitogenomics and comparative methods. Mitochondrial genomes from cave and pelagic polynoids were highly similar, with non-significant rearrangements only present in cave Gesiella. Gene orders of the new mitogenomes were highly similar to shallow water species, suggestive of an underlying polynoid ground pattern. Being the first phylogenetic analyses to include the holopelagic Drieschia, we recovered this species nested among shallow water terminals, suggesting a shallow water ancestry. Based on these results, our phylogenetic reconstructions showed that swimming evolved independently three times in Polynoidae, involving convergent adaptations in morphology and motility patterns across the deep sea (Branchipolynoe), midwater (Drieschia) and anchialine caves (Pelagomacellicephala and Gesiella). Phylogenetic generalized least-squares (PGLS) analyses showed that holopelagic and anchialine cave species exhibit hypertrophy of the dorsal cirri, yet, these morphological modifications are achieved along different evolutionary pathways, i.e., elongation of the cirrophore versus style. Together, these findings suggest that a water column lifestyle elicits similar morphological adaptations, favouring bodies designed for drifting and sensing.

Effects of succession stages and altitudinal gradient on leaf surface area and biomass allocation of typical plants in the subalpine of Eastern Tibetan Plateau

Leaves are the main organs of plants for photosynthesis. The scaling relationship between leaf mass (LM) and leaf area (LA) can reflect the capabilities of plants to capture light energy, obtain net carbon benefits, and adapt to environmental changes. The LA-LM relationship is intimately associated with the water and carbon economics of plants. The scaling relationship between LA and LM is important to reveal the strategies of plant biomass allocation with changes of environmental stresses. Previous studies primarily focused on relatively close plants within the same taxon (e.g., a family or a genus), different plants in different altitude gratient, or special groups such as epiphytes. However, it is still unknown about whether and how the scaling relationship between LM and LA varies across succession stages and altitudinal gratient. We measured LA, leaf fresh weight (LFW) and leaf dry weight (LDW) of 201 plant species with 603 individuals in nine plots in Zhouqu County of China to study the strategy of allometry relationships of LA and LM among different plant life forms, succession stages and altitudinal gratient. We found that the quotient of LDW and LFW for woody plants was significantly higher than that for herbaceous plants. In the process of adapting to changes of life forms, succession stages and altitudes, the scaling exponent of LFW vs. LA was more sensitive than that of LDW vs. LA. Most scaling relationships of LFW vs. LA conformed to the law of diminishing returns, but the scaling relationship between LDW and LA appeared more complicated. The scaling relationships between LDW and LFW mainly exhibited an increasing returns. Increasing returns were more obvious in life forms, middle altitude and mid-succession. In addition, no matter at which level, the coefficient of determination (i.e. R2) of LA vs. LFW was greater than that of LA vs. LDW. It might be more convincing to predict the relationship between LA and LM by using the data of LA vs. LFW. Most of (17 of 24, 70.83%) the R2 of PGLS (Phylogenetic Generalized Least Squares) regression were higher than those of SMA (Standardized Major Axis) regression, which showed that the influence of phylogeny should not be ignored in the study of multi-species traits relationships. In general, the trade off or allometry between LA and LM varied among plants life forms or environmental changes including succession stages and elevation variability. This pattern can be explained by different leaf strategies in response to environmental pressure and constrains.

Environmental drivers of plant distributions at global and regional scales

AbstractAimHow environmental factors drive plant distribution across the globe is one of the most fundamental questions in ecology. Nevertheless, the relative importance of different environmental factors in driving plant distributions across spatial scales and among plant groups is not clear. This study aims to disentangle how plant–environment relationships vary with latitude and among plant taxa.LocationGlobal.Time periodPresent day.Main taxaPlant taxa including angiosperms, gymnosperms, pteridophytes and bryophytes.MethodsWe obtained global distribution occurrence data of mass plant groups (625 families, 6,221 genera, and 54,101 species) from the Global Biodiversity Information Facility (GBIF) database. We used random forest method to quantify the relative effects of 15 environmental factors (including climate, soil and topography) on plant distributions at global and regional scales (divided into different latitude zones). We also used phylogenetic generalized least squares (PGLS) models to investigate the relationships between environmental variables and geographical range size, latitudinal range and limits of plants at the global scale.ResultsOur analyses revealed the primacy of the effects of climatic variability (temperature seasonality and isothermality) on plant distribution at the global scale. The relative contributions of temperature seasonality and isothermality peaked in tropical areas, whereas solar radiation and annual mean temperature had stronger influence in high‐latitude areas. Wide‐range plant groups tended to occur in areas with higher temperature variability (isothermality and temperature seasonality) and flatter terrain (low slope). Both climate variability and extreme influenced geographical range size, latitudinal range and limits of plants.Main conclusionsOur study highlights the significance of climate variability for global plant distributions. Environmental effects upon plant distributions vary across latitudes. The findings imply that environmental factors affecting plant distributions change with geographical scales, suggesting that different geographical and ecological processes should be integrated to explain multi‐scale distribution patterns.

The Elevation does not strongly influence interspecific variation in body size of small Tropical endotherms

Introduction: Body size is an essential trait for endotherms to face the physiological requirements of cold, so there is a tendency to large body size at high altitudes and latitudes, known as Bergmann's rule. However, the validity of this ecomorphological rule to small-bodied endotherms across altitudinal gradients is poorly known. Objective: To understand the effects of environmental variation on body size, we assessed whether interspecific variation in body size of small tropical endotherms follows Bergmann's rule along tropical altitudinal gradients. Methods: We compiled data on elevational ranges and body masses for 133 species of hummingbirds of Colombia. We then assessed the association between body mass and mid-point of the altitudinal distribution using phylogenetic generalized least squares (PGLS) analyses under different evolutionary models. Results: We found a decelerating rate of evolution for body size since the Early Burst model of evolution provided a better fit to body mass data. For elevational range, we found a slow and constant rate since Pagel's lambda model provided a better fit to the mid-point of the altitudinal distribution data. Besides, phylogenetic regression analysis indicated that body mass and the altitudinal range of hummingbirds are associated through the phylogeny, with a positive but slight association (R2= 0.036). Conclusions: We found that body mass and altitude of hummingbirds are positively related, which is in agreement with expectations under Bergmann's rule. However, this association was weaker than expected for small and non-passerine birds like hummingbirds. Thus, our results suggest that environmental changes across altitudinal gradients do not strongly influence body mass in small tropical endotherms as hummingbirds.