Effects of microclimate,litter type,and mesh size on leaf litter decomposition along an elevation gradient in the Wuyi Mountains,China

Litter decomposition is an important ecosystem process regulated by both biotic factors (e.g., decomposers and litter types) and abiotic factors (e.g., temperature and moisture). This study examined the regulatory effects of soil fauna and microclimate on decomposition of two substrates (Castanopsis carlesii and Pinus taiwanensis) along an elevation gradient in four ecosystems of zonal vegetation types in southeastern China: evergreen broadleaf forest (EVB), coniferous forest (COF), dwarf forest (DWF), and alpine meadow (ALM). Our objective was to identify the mechanisms by which microclimate, substrate, and fauna control litter decomposition, especially where variations in ecosystem structure and environment are markedly shown across an elevation gradient. The hypotheses were as follows: (1) litter decomposition within the same litter type would decrease across the elevation gradient, (2) litter decomposition would be lower in poorer nutrient quality substrate across the four sites, and (3) litter dynamics, influenced by strong interactions among ecosystem type, litter type, and decomposers, would vary by elevation gradient due to microclimate effects (i.e., temperature and moisture). The decomposition rates of C. carlesii were significantly higher than those of P. taiwanensis at EVB, COF, and DWF sites; however, they were not significantly different at the ALM site. Low elevation forests possessed a microclimate (warm and humid) that favors decomposer activities and also appeared to possess a decomposer community adapted to consuming large amounts of leaf litter, as indicated by the rapid leaf litter loss. Litter decomposition in micro-mesh bags proceeded more slowly compared to litter in meso-mesh and macro-mesh litterbags across the elevation gradient, indicating that restricting some detritivore access to litter reduced litter mass loss. We suggest that microclimate and faunal contributions to plant litter decomposition differ markedly across the ecosystems in the Wuyi Mountains.     

Performances of machine learning algorithms for mapping fractional cover of an invasive plant species in a dryland ecosystem

In recent years, an increasing number of distribution maps of invasive alien plant species (IAPS) have been published using different machine learning algorithms (MLAs). However, for designing spatially explicit management strategies, distribution maps should include information on the local cover/abundance of the IAPS. This study compares the performances of five MLAs: gradient boosting machine in two different implementations, random forest, support vector machine and deep learning neural network, one ensemble model and a generalized linear model; thereby identifying the best‐performing ones in mapping the fractional cover/abundance and distribution of IPAS, in this case called Prosopis juliflora (SW. DC.). Field level Prosopis cover and spatial datasets of seventeen biophysical and anthropogenic variables were collected, processed, and used to train and validate the algorithms so as to generate fractional cover maps of Prosopis in the dryland ecosystem of the Afar Region, Ethiopia. Out of the seven tested algorithms, random forest performed the best with an accuracy of 92% and sensitivity and specificity >0.89. The next best‐performing algorithms were the ensemble model and gradient boosting machine with an accuracy of 89% and 88%, respectively. The other tested algorithms achieved comparably low performances. The strong explanatory variables for Prosopis distributions in all models were NDVI, elevation, distance to villages and distance to rivers; rainfall, temperature, near‐infrared and red reflectance, whereas topographic variables, except for elevation, did not contribute much to the current distribution of Prosopis. According to the random forest model, a total of 1.173 million ha (12.33% of the study region) was found to be invaded by Prosopis to varying degrees of cover. Our findings demonstrate that MLAs can be successfully used to develop fractional cover maps of plant species, particularly IAPS so as to design targeted and spatially explicit management strategies.     

Assessing spatial and environmental drivers of phylogenetic structure in Brazilian Araucaria forests

Evidence of phylogenetic conservatism in plant ecological traits has accumulated over the past few years, suggesting an interplay between the distribution of phylogenetic clades and major environmental gradients. Nonetheless, determining what environmental factors underlie the distribution of phylogenetic lineages remains a challenge because environmental factors are correlated with spatial gradients where the latter might indicate some degree of dispersal limitation in phylogenetic pools. We analyzed the phylogenetic structure of plant assemblages across the Brazilian Araucaria forests and assessed how phylogenetic structure responds to environmental and spatial gradients. We compiled data on plant occurrence in 45 plots across the Araucaria forest biome. The phylogenetic structure of the plots was characterized using phylogenetic fuzzy‐weighting followed by principal coordinates of phylogenetic structure (PCPS). We used distance‐based redundancy analysis (db‐RDA) to analyze the relationships between phylogenetic clades and environmental and spatial factors. Variation partitioning showed that the phylogenetic structure of Brazilian Araucaria forests was better explained by environment factors (altitude and annual mean temperature) than by space. Yet, spatially‐structured environmental variation explained about one‐third of total variation in the phylogenetic structure. Thus, the influence of spatial filters on the phylogenetic structure was more related to environmental gradients across the Brazilian Araucaria forest biome than to dispersal limitation of phylogenetic lineages. Furthermore, the influence of explanatory factors on the phylogenetic structure was concentrated in few nodes, the one splitting tree ferns from seed plants, and a second splitting malvids from other eurosids. Assessing the functional links between species distribution patterns and environmental gradients is not an easy task when we have to deal with large species pools. Identifying major phylogenetic gradients across an environmental and/or geographical range of interest can represent a first step towards a better understanding of general assembly processes in ecological communities.     

Loss of forest cover and host functional diversity increases prevalence of avian malaria parasites in the Atlantic Forest

Host phylogenetic relatedness and ecological similarity are thought to contribute to parasite community assembly and infection rates. However, recent landscape level anthropogenic changes may disrupt host-parasite systems by impacting functional and phylogenetic diversity of host communities. We examined whether changes in host functional and phylogenetic diversity, forest cover, and minimum temperature influence the prevalence, diversity, and distributions of avian haemosporidian parasites (genera Haemoproteus and Plasmodium) across 18 avian communities in the Atlantic Forest. To explore spatial patterns in avian haemosporidian prevalence and taxonomic and phylogenetic diversity, we surveyed 2241 individuals belonging to 233 avian species across a deforestation gradient. Mean prevalence and parasite diversity varied considerably across avian communities and parasites responded differently to host attributes and anthropogenic changes. Avian malaria prevalence (termed herein as an infection caused by Plasmodium parasites) was higher in deforested sites, and both Plasmodium prevalence and taxonomic diversity were negatively related to host functional diversity. Increased diversity of avian hosts increased local taxonomic diversity of Plasmodium lineages but decreased phylogenetic diversity of this parasite genus. Temperature and host phylogenetic diversity did not influence prevalence and diversity of haemosporidian parasites. Variation in the diversity of avian host traits that promote parasite encounter and vector exposure (host functional diversity) partially explained the variation in avian malaria prevalence and diversity. Recent anthropogenic landscape transformation (reduced proportion of native forest cover) had a major influence on avian malaria occurrence across the Atlantic Forest. This suggests that, for Plasmodium, host phylogenetic diversity was not a biotic filter to parasite transmission as prevalence was largely explained by host ecological attributes and recent anthropogenic factors. Our results demonstrate that, similar to human malaria and other vector-transmitted pathogens, prevalence of avian malaria parasites will likely increase with deforestation.     

Deconstructing the dimensions of alpha diversity in squamate reptiles (Reptilia: Squamata) across the Americas

Aim

Our aim is to document the dimensions of current squamate reptile biodiversity in the Americas by integrating taxonomic, phylogenetic and functional data, and assessing how this may vary across phylogenetic scales. We also explore the potential underlying mechanisms that may be responsible for the observed geographical diversity patterns.

Location

The Americas.

Time period

Present.

Major taxa

Squamate reptiles.

Methods

We used published data on the distribution, phylogeny, and body size of squamate reptiles to document the current dimensions of their alpha diversity in the Americas. We overlapped species ranges to estimate taxonomic diversity (TD) and calculated phylogenetic diversity (PD) using mean pairwise phylogenetic distance (MPD), speciation rate (DivRate) and Faith's phylogenetic index (PD). We estimated functional diversity (FD) as trait dispersion in the multivariate space using body size and leg development data. We implemented a deconstructive macroecological approach to understand how spatial mismatches between the three facets of diversity vary across phylogenetic scales, and the potential eco-evolutionary mechanisms driving these patterns across space.

Results

We found a strong latitudinal gradient of TD with a large accumulation in tropical regions. PD and FD patterns were largely similar likely due to the high phylogenetic signal in the traits used, and higher values tended to be concentrated in harsh and/or heterogeneous environments. We found differences between major clades within Squamata that display contrasting geographical patterns. Several regions across the continent shared the same spatial mismatches between dimensions across clades, suggesting that similar eco-evolutionary processes are shaping these regional reptile assemblages. However, we also found evidence that non-mutually exclusive processes can operate differently across clades.

Main conclusions

The deconstructive approach implemented here is based on a solid macroecological framework. We can extend this to other taxonomic groups to establish whether there are particularities about how different eco-evolutionary mechanisms shape biodiversity facets in a spatially explicit context.     

Community assembly after long-term fragmentation: a case study of tropical rainforest in Xishuangbanna,south-west China

Background: Tropical rainforests represent the most species-rich and at the same time the most fragmented terrestrial biome on Earth. Fragmentation of tropical rainforests is having wide-ranging consequences for the maintenance of local species diversity and community assembly patterns.

Aims: To examine floristic changes and changes in community phylogenetic structure in the forest fragment over the past five decades.

Methods: A new taxonomic diversity algorithm (within-family diversity) was developed to assess floristic changes in the forest fragment. Community phylogenetic structure was then compared before and after fragmentation.

Results: Taxonomic diversity changed greatly among families, with changes occurring randomly across the phylogeny. The forest fragment had higher phylogenetic diversity, higher mean pair-wise phylogenetic distance, but lower mean nearest-neighbour distance. The community phylogenetic structure has changed significantly from clustering to dispersion.

Conclusions: High species turnover occurred in the forest fragment. While shade-tolerant species have been lost, and ruderal and alien species have been added, overall phylogenetic diversity has increased with species being more phylogenetically distant. Competitive exclusion, which was related to the relatively drier conditions in the forest after fragmentation, led the plant community phylogenetic structure to be more dispersed.     

Humans,fire and landscape pattern: understanding a maquis‐forest complex,Mont Do,New Caledonia,using a spatial ‘state‐and‐transition’ model

Abstract Aim The research explores how changes in disturbance regime resulting from human settlement may affect landscape structure. A spatially explicit grid‐based simulation model is used to explore the interplay between humans, fire regime and landscape composition. Location The study site for this research is the botanical reserve at Mont Do, New Caledonia. The endemic conifer Araucaria laubenfelsii (Araucariaceae) forms a key component of the landscape at Mont Do. This species is unusual in that it is found scattered as an emergent in maquis and as a canopy species in adjacent rain forest patches. Although now dominated by a low maquis, prior to human settlement of New Caledonia, montane landscapes such as Mont Do are likely to have been heavily forested. Methods A spatially explicit simulation model, based on field data and palaeoecological information, was used to explore interactions between disturbance regime and the landscape. The model is described briefly here and more fully in Perry & Enright (2002) Ecological Modelling, 152 , 279. Results The model suggests that human‐influenced changes to the fire regime at Mont Do have been important in generating the current landscape structure. The origin and maintenance of forest landscapes and maquis‐forest mosaic landscapes are considered in the context of alternative stable states. Strong feedback loops between fire size and landscape composition, mediated at the smaller scale by other similar mechanisms, are capable of driving landscape change. The utility of a spatial state and transition modelling approach is demonstrated. Main conclusions The current landscape pattern on Mont Do is likely the result of changes to the fire regime occurring since human settlement. The specific mechanisms for this change outlined here may occur in a number of other similar systems. Understanding the origin and persistence of these ‘fire landscapes’ in New Caledonia and in the south‐west Pacific in general is crucial for their effective management.     

Ecophysiological variation across a forest‐ecotone gradient produces divergent climate change vulnerability within species

Climate change related risks and impacts on ectotherms will be mediated by habitats and their influence on local thermal environments. While many studies have documented morphological and genetic aspects of niche divergence across habitats, few have examined thermal performance across such gradients and directly linked this variation to contemporary climate change impacts. In this study, we quantified variation in thermal performance across a gradient from forest to gallery forest‐savanna mosaic in Cameroon for a skink species (Trachylepis affinis) known to be diverging genetically and morphologically across that habitat gradient. Based on these results, we then applied a mechanistic modelling approach (NicheMapR) to project changes in potential activity, as constrained by thermal performance, in response to climate change. As a complimentary approach, we also compared mechanistic projections with climate‐driven changes in habitat suitability based on species distribution models of forest and ecotone skinks. We found that ecotone skinks may benefit from warming and experience increased activity while forest skinks will likely face a drastic decrease in thermal suitability across the forest zone. Species distribution models projected that thermal suitability for forest skinks in coastal forests would decline but in other parts of the forest zone skinks are projected to experience increased thermal suitability. The results here highlight the utility of mechanistic approaches in revealing and understanding patterns of climate change vulnerability which may not be detected with species distribution models alone. This study also emphasizes the importance of intra‐specific physiological variation, and habitat‐specific thermal performance relationships in particular, in determining warming responses.     

Genetic and phenotypic variation across a hybrid zone between ecologically divergent tree squirrels (Tamiasciurus)

A hybrid zone along an environmental gradient should contain a clinal pattern of genetic and phenotypic variation. This occurs because divergent selection in the two parental habitats is typically strong enough to overcome the homogenizing effects of gene flow across the environmental transition. We studied hybridization between two parapatric tree squirrels (Tamiasciurus spp.) across a forest gradient over which the two species vary in coloration, cranial morphology and body size. We sampled 397 individuals at 29 locations across a 600‐km transect to seek genetic evidence for hybridization; upon confirming hybridization, we examined levels of genetic admixture in relation to maintenance of phenotypic divergence despite potentially homogenizing gene flow. Applying population assignment analyses to microsatellite data, we found that Tamiasciurus douglasii and T. hudsonicus form two distinct genetic clusters but also hybridize, mostly within transitional forest habitat. Overall, based on this nuclear analysis, 48% of the specimens were characterized as T. douglasii, 9% as hybrids and 43% as T. hudsonicus. Hybrids appeared to be reproductively viable, as evidenced by the presence of later‐generation hybrid genotypes. Observed clines in ecologically important phenotypic traits—fur coloration and cranial morphology—were sharper than the cline of putatively neutral mtDNA, which suggests that divergent selection may maintain phenotypic distinctiveness. The relatively recent divergence of these two species (probably late Pleistocene), apparent lack of prezygotic isolating mechanisms and geographic coincidence of cline centres for both genetic and phenotypic variation suggest that environmental factors play a large role in maintaining the distinctiveness of these two species across the hybrid zone.     

Spread of an invasive grass in closed-canopy deciduous forests across local and regional environmental gradients

Establishment of Microstegium vimineum, an invasive exotic grass, in closed-canopy U.S. eastern forests was evaluated across a local (roadside to forest interior) and regional (across two geographic provinces) environmental gradient in West Virginia. The two geographic provinces were the Allegheny Plateau (more mesic) and the Ridge and Valley Province (more xeric). Biotic, abiotic, and disturbance variables were measured in (1) systematically located plots, starting from the roadside and extending 50 m into the forests, and (2) randomly selected, forest interior plots, with equal numbers of plots containing or not containing M. vimineum. Associations between the variables and the presence of M. vimineum at both scales were evaluated using generalized linear models. Relative importance of the variables related to M. vimineum establishment in the forest interior plots at the regional scale was determined using logistic regression. Results confirmed Microstegium vimineum’s reduced reproductive capacity in the forest interior compared to the roadside. Patches of M. vimineum in the forest interiors across the regional gradient were best defined by high native plant richness and diversity. Greater canopy opening, more moss, and shallower litter depths were also positively and significantly associated with M. vimineum presence, but only during the driest sample year.     

Seasonal elevational movements of Eastern Olive Sunbird Cyanomitra olivacea in the Uluguru Mountains,Tanzania

Little is known about the seasonal elevational movements for most tropical avifauna species. Seasonal elevational movements of the Eastern Olive Sunbird Cyanomitra olivacea were studied along an elevational gradient from 600 to 1 500?m above sea level in the Uluguru Mountains, Tanzania, between May 2005 and February 2006. The recapture of ringed individuals along an elevational gradient across seasons provided evidence for the seasonal elevational movement of the Eastern Olive Sunbird in the Uluguru Mountains and the first documented evidence for this species in the Eastern Arc Mountains as a whole. Due to forest fragmentation and lack of corridors connecting high- and low-altitude forests in the Uluguru Mountains, the results have implications for conservation of the forest along the entire elevational gradient as well as for other forest bird species that have been documented to make seasonal elevational movements in the Uluguru Mountains and the entire Eastern Arc Mountains.     

Scale-dependent mechanisms in the population dynamics of an insect herbivore

A multiscale approach has lead to significant advances in the understanding of species population dynamics. The scale-dependent nature of population processes has been particularly clearly illustrated for insect herbivores. However, one of the most well-studied insect herbivores, the galling sawfly Euura lasiolepis, has to date been examined almost exclusively at fine spatial scales. The preference-performance, plant vigour and larval survival hypotheses are well supported by this species. Here, we test these hypotheses at a spatial scale larger than that previously considered, i.e. across a landscape in northern Arizona represented by an altitudinal gradient encompassing a series of drainages. We also develop a qualitative model for understanding the population dynamics of E. lasiolepis based on patterns of survival and mortality found in this study and previous ones. Gall density was highly variable across the altitudinal gradient, not explained by host plant variables, and thus a poor surrogate fot population abundance. These findings for the first time fail to support the plant vigour and preference hierarchy hypotheses for E. lasiolepis. Dispersal limitation most likely explains the lack of support for these hypotheses at this scale. By contrast, sawfly survival, gall abortion, parasitism and larval mortality were well explained by host plant quality variables and altitude. The larval survival hypothesis was well supported and is thus comparatively scale-invariant. A qualitative model developed here highlighted the importance of both willow water status and disturbance in determining host plant quality, as well as an apparent trade off between shoot length and plant moisture status in determining vital rates across the altitudinal gradient. This study thus demonstrated for the first time the scale-dependent nature of mechanisms underlying the population dynamics E. lasiolepis, and identified the interaction between parasitism and altitude as a novel mechanism underlying spatial patterns in the survival and mortality patterns of this species.     

Long-term physiological and morphological acclimation by the evergreen shrub <Emphasis Type="Italic">Buxus sempervirens</Emphasis> L. to understory and canopy gap light intensities

Physiological and morphological plasticity are essential for growth and reproduction in contrasting light environments. In dry forest ecosystems, light generalists must also cope with the trade-offs involved in synchronous acclimation to light availability and drought. To understand how the broadleaf evergreen tree-shrub Buxus sempervirens L. (common box) inhabits both understory and successional terrain of Mediterranean forest, we measured photosynthesis–fluorescence light response, morphological traits and architectural characteristics across a light gradient. Our results show that B. sempervirens exhibits stress resistance syndrome, with little change in net photosynthesis rate across a light availability gradient, due to compensatory physiological and morphological acclimation. Light energy processing and dissipation potential were highest in leaves of well-illuminated plants, with higher electron transport rate, fraction of open photosystem II reaction centres, non-photochemical quenching, photorespiration and dark respiration. In contrast, traits reducing light capture efficiency were observed in high light shrubs, including higher leaf mass per unit area, leaf clumping, leaf inclination and branch inclination. We suggest that both physiological and morphological plasticity are required for B. sempervirens to survive across a light gradient in a dry forest ecosystem, while exhibiting homoeostasis in photosynthetic gas exchange. We further speculate that the low growth rate of B. sempervirens is effective in full sun only due to a lack of competition in low resource microsites.     

A tale of the nearly tail‐less: the effects of Plio‐Pleistocene climate change on the diversification of the African avian genus Sylvietta

Sylvietta is a broadly distributed group of African species inhabiting a wide range of habitats and presents an interesting opportunity to investigate the historic mechanisms that have impacted the biogeography of African avian species. We collected sequence data from 50 individuals and used model‐based phylogenetic methods, molecular divergence estimates and ancestral area estimates to construct a time‐calibrated phylogeny and estimation of biogeographic history. We estimate a southern African origin for Sylvietta, with an initial divergence splitting the genus into two clades. The first consists of arid‐adapted species, with a southern African origin and subsequent diversification north into Ethiopia–Somalia. The second clade is estimated as having a Congolian forest origin with an eastward pattern of colonization and diversification as a result of Plio‐Pleistocene forest dynamics. Additionally, two members of the genus Sylvietta display interesting patterns of intraspecific diversification. Sylvietta rufescens is an arid‐adapted species inhabiting southern Africa, and we recover two subclades with a divergence dating to the Pleistocene, a unique pattern for avian species which may be explained via isolation in arid habitat fragments in the early Pleistocene. Second, Sylvietta virens, a species endemic to Afro‐tropical forests, is recovered with geographically structured genetic diversification across its broad range, an interesting result given that recent investigations of several avian forest species have found similar and substantial geographically structured genetic diversity relating to Plio‐Pleistocene forest fragmentation. Overall, Plio‐Pleistocene habitat cycling played a significant role in driving diversification in Sylvietta, and this investigation highlights the substantial impact of climate‐driven habitat dynamics on the history of sub‐Saharan species.     

Optimal defense in plants: assessment of resource allocation costs

Genetic and environmental variation of functional traits within populations might be maintained by natural selection when resource allocation costs (RACs) balance trait benefits. Despite the intuitive appeal of optimization models, empirical tests have failed to support the importance of RACs for plant traits that confer resistance against pests. To address this discrepancy, we modified an early model by allowing the cost function to vary across a resource gradient as predicted for RACs and by assuming that the benefits depend on variation in the pest population for susceptibility. Instead of the intermediate defense optimum of the original model, defenses were predicted to be either high or absent, depending on resource availability and history. This result is not supported by empirical tests for ecological or evolutionary outcomes, including our own examination of glucosinolate toxins from sib-families of Boechera stricta (Brassicaceae) grown across an NPK fertilizer gradient. Although we detected an apparent cost of defense in the absence of herbivores, the cost did not increase as resources became more limiting. Also defense production did not vary across the resource gradient as predicted by the modified model. Thus, a model based on explicit expectations of RACs produced predictions that are not supported. Instead, other kinds of costs, such as ecological (indirect) costs may be more important. Alternatively, general conflicts in gene expression and antagonistic crosstalk among signaling pathways may underlie apparent costs.     

Estimating below‐canopy light regimes using airborne laser scanning: An application to plant community analysis

Light is a key driver of forest biodiversity and functioning. Light regimes beneath tree canopies are mainly driven by the solar angle, topography, and vegetation structure, whose three‐dimensional complexity creates heterogeneous light conditions that are challenging to quantify, especially across large areas. Remotely sensed canopy structure data from airborne laser scanning (ALS) provide outstanding opportunities for advancement in this respect. We used ALS point clouds and a digital terrain model to produce hemispherical photographs from which we derived indices of nondirectional diffuse skylight and direct sunlight reaching the understory. We validated our approach by comparing the performance of these indices, as well as canopy closure (CCl) and canopy cover (CCo), for explaining the light conditions experienced by forest plant communities, as indicated by the Landolt indicator values for light (L_light) from 43 vegetation surveys along an elevational gradient. We applied variation partitioning to analyze how the independent and joint statistical effects of light, macroclimate, and soil on the spatial variation in plant species composition (i.e., turnover, Simpson dissimilarity, β_SIM) depend on light approximation methodology. Diffuse light explained L_light best, followed by direct light, CCl and CCo (R² = .31, .23, .22, and .22, respectively). The combination of diffuse and direct light improved the model performance for β_SIM compared with CCl and CCo (R² = .30, .27 and .24, respectively). The independent effect of macroclimate on β_SIM dropped from an R² of .15 to .10 when diffuse light and direct light were included. The ALS methods presented here outperform conventional approximations of below‐canopy light conditions, which can now efficiently be quantified along entire horizontal and vertical forest gradients, even in topographically complex environments such as mountains. The effect of macroclimate on forest plant communities is prone to be overestimated if local light regimes and associated microclimates are not accurately accounted for.     

Intraspecific and interspecific adaptive latitudinal cline in Brassicaceae seed oil traits

Premise of the Study

Nearly all seed plants rely on stored seed reserves before photosynthesis can commence. Natural selection for seed oil traits must have occurred over 319 million years of evolution since the first seed plant ancestor. Accounting for the biogeographic distribution of seed oil traits is fundamental to understanding the mechanisms of adaptive evolution in seed plants. However, the evolution of seed oils is poorly understood. We provide evidence of the adaptive nature of seed oil traits at the intraspecific and interspecific levels in Brassicaceae—an oilseed‐rich and economically important plant family.

Methods

Univariate statistics, Pearson's correlation, multiple regression, generalized linear mixed model analysis, and phylogenetic autocorrelation tests on seed oil traits of 360 accessions of Arabidopsis thaliana and 216 Brassicaceae species helped provide evidence of the adaptive nature of seed oil traits.

Key Results

At higher latitudes, both seed oil content and unsaturated fatty acids have selective advantages in Arabidopsis thaliana (intraspecific‐level), while only unsaturated fatty acids have selective advantages across 216 Brassicaceae species (interspecific‐level). The seed oil patterns fit within the theoretical framework of the gradient model. Seed oil content increases significantly from temperate to subtropical to tropical regions in Brassicaceae herbs. Absence of phylogenetic signals for seed oil traits and high seed oil content in four tribes of Brassicaceae were observed.

Conclusions

Multiple seed oil traits are adaptive in nature and follow a gradient model. Consistent evolutionary patterns of seed oil traits were observed at the intraspecific and interspecific levels in Brassicaceae. Seed oil traits change with latitude and across biomes, suggesting selection. The absence of a phylogenetic signal for seed oil traits and the occurrence of high seed oil content in four Brassicaceae tribes provides evidence of the adaptive nature of seed oil traits in Brassicaceae.