Suite Of Traits Research Articles

Comparing taxon- and trait-environment relationships in stream communities

Abstract Traits define how organisms interact with their surrounding environment and with other organisms. Thus, trait composition of biological communities is expected to change predictably along environmental gradients. Because organisms’ traits, but not taxonomic identity, determine their fitness, trait-environment relationships should provide a better way to elucidate how biodiversity respond to environmental change. Here, we used data on tropical streams embedded in a landscape of intensive agriculture to investigate trait-environment and taxon-environment relationships in a set of 91 mayfly communities from southeastern Brazil. We expected that trait-environment relationships would be stronger than taxon-environment relationships and that the linkage between traits and environmental variables would provide mechanistic insights on environmental filtering. We found that variation in both species composition and traits were correlated to salinity, highlighting the influence of water salinization on mayfly communities due to agricultural practices. Surprisingly, using analogous statistical methods, in general, we found that the strengths of trait-environment relationships were lower than that of taxon-environment relationships. Further, (1) species responses to gradients were not correlated to similarity in their traits and (2) some species with different trait composition responded similarly to environmental variation, indicating that different suite of traits can cope with similar environmental contexts. Besides some cautionary results about trait-based approaches, results from taxon-based approaches indicated that variation in composition was more related to spatial variables, suggesting that dispersal limitation undermine its use for large scale assessments. Our results suggest that both taxon- and trait-based approaches have weakness and strengths and deciding between them for biomonitoring purposes will depend on spatial scales, trait interrelationships, and analytical methods.

Behavioral constraints on local adaptation and counter-gradient variation: Implications for climate change.

Resource allocation to growth, reproduction, and body maintenance varies within species along latitudinal gradients. Two hypotheses explaining this variation are local adaptation and counter‐gradient variation. The local adaptation hypothesis proposes that populations are adapted to local environmental conditions and are therefore less adapted to environmental conditions at other locations. The counter‐gradient variation hypothesis proposes that one population out performs others across an environmental gradient because its source location has greater selective pressure than other locations. Our study had two goals. First, we tested the local adaptation and counter‐gradient variation hypotheses by measuring effects of environmental temperature on phenotypic expression of reproductive traits in the burying beetle, Nicrophorus orbicollis Say, from three populations along a latitudinal gradient in a common garden experimental design. Second, we compared patterns of variation to evaluate whether traits covary or whether local adaptation of traits precludes adaptive responses by others. Across a latitudinal range, N. orbicollis exhibits variation in initiating reproduction and brood sizes. Consistent with local adaptation: (a) beetles were less likely to initiate breeding at extreme temperatures, especially when that temperature represents their source range; (b) once beetles initiate reproduction, source populations produce relatively larger broods at temperatures consistent with their local environment. Consistent with counter‐gradient variation, lower latitude populations were more successful at producing offspring at lower temperatures. We found no evidence for adaptive variation in other adult or offspring performance traits. This suite of traits does not appear to coevolve along the latitudinal gradient. Rather, response to selection to breed within a narrow temperature range may preclude selection on other traits. Our study highlights that N. orbicollis uses temperature as an environmental cue to determine whether to initiate reproduction, providing insight into how behavior is modified to avoid costly reproductive attempts. Furthermore, our results suggest a temperature constraint that shapes reproductive behavior.

Rapid adaptive evolution of the diapause program during range expansion of an invasive mosquito.

In temperate climates, the recurring seasonal exigencies of winter represent a fundamental physiological challenge for a wide range of organisms. In response, many temperate insects enter diapause, an alternative developmental program, including developmental arrest, that allows organisms to synchronize their life cycle with seasonal environmental variation. Geographic variation in diapause phenology contributing to local climatic adaptation is well documented. However, few studies have examined how the rapid evolution of a suite of traits expressed across the diapause program may contribute to climatic adaptation on a contemporary timescale. Here, we investigate the evolution of the diapause program over the past 35 years by leveraging a “natural experiment” presented by the recent invasion of the Asian tiger mosquito, Aedes albopictus, across the eastern United States. We sampled populations from two distinct climatic regions separated by 6° of latitude (∼700 km). Using common‐garden experiments, we identified regional genetic divergence in diapause‐associated cold tolerance, diapause duration, and postdiapause starvation tolerance. We also found regional divergence in nondiapause thermal performance. In contrast, we observed minimal regional divergence in nondiapause larval growth traits and at neutral molecular marker loci. Our results demonstrate rapid evolution of the diapause program and imply strong selection caused by differences in winter conditions.

Floral Trait Evolution of Angiosperms on Pacific Islands.

Animals frequently evolve unique suites of traits on islands, but whether plants evolve comparable island syndromes remains unresolved. Here, we test the prediction on the basis of natural history observations that insect-pollinated plants evolve smaller flowers on islands than on mainland communities. We examined 556 plant species representing 136 phylogenetically independent contrasts between island and mainland sister taxa. We focused on endemic taxa originating from the Americas associated with seven tropical and subtropical islands of the Pacific Ocean. Contrary to conventional wisdom, flowers were not on average smaller on islands than on the mainland. On specific archipelagos (the Galápagos Islands and Revillagigedo Islands), however, island taxa did evolve smaller flowers. Divergence in flower size between island and mainland taxa also varied among taxonomic families, such that some plant families evolved smaller flowers on islands, other families evolved larger flowers on islands, and some families exhibited no divergence in flower size between island and mainland taxa. Overall, our results show that there is no general island syndrome for flower size, but instead that the evolution of floral morphology is complex and context dependent, depending on variation among islands and plant families. Our results also suggest that if island floras are typically dominated by small flowered species, as suggested by natural history observations, then ecological filtering is a more likely explanation of this pattern than evolutionary divergence postcolonization. We propose future studies that could disentangle the relative roles of ecological filtering and evolution in the distribution of floral traits on islands.

Explaining the exceptional 4270m high elevation limit of an evergreen oak in the south-eastern Himalayas.

Unlike the well-understood alpine treeline, the upper range limits of tree taxa that do not reach the alpine treeline are largely unexplained. In this study, we explored the causes of the exceptionally high elevation (4270m) occurrence of broad-leaved evergreen oaks (Quercus pannosa) in the south-eastern Himalayas. We assessed the course of freezing resistance of buds and leaves from winter to summer at the upper elevational limit of this oak species. Linked to leaf phenology, we analyzed freezing resistance and assessed minimum crown temperature for the past 65years. We also examined potential carbon limitation at the range limit of this species. Last season buds and leaves operated at a safety margin of 5.5 and 11K in mid-winter. Once fully dehardened early in July, last season foliage is damaged at -5.9 and new foliage at -4.6°C. Bud break is timed for late June to early July when low temperature extremes historically were never below -3.0°C. The monsoon regime ensures a long remaining season (149 days), thus compensating for the late onset of shoot growth. Compared with a site at 3450m, specific leaf area is reduced, foliar non-structural carbohydrate concentrations are similar and the δ13C signal is higher, jointly suggesting that carbon limitation is unlikely at the range limit of this species. We also show that these oaks enter the growing season with fully intact (not embolized) xylem. We conclude that the interaction between phenology and freezing tolerance results in safe flushing, while still facilitating shoot maturation before winter. These factors jointly determine the upper range limit of this oak species. Our study illuminates an exceptional case of broad-leaved evergreen tree performance near the treeline, and by exploring a suite of traits, we can underpin the central role of flushing phenology in such a stressful environment.

The evolution of extended parental care in glassfrogs: Do egg‐clutch phenotypes mediate coevolution between the sexes?

AbstractMany animals improve offspring survival through parental care. Research on coevolution between parents has provided key insight into the genesis and maintenance of biparental care. However, understanding family dynamics more broadly requires assessing potential male–female coevolutionary processes in the more widespread and common context of uniparental care. Here, we explore how pre‐zygotic maternal contributions, jelly coats and oviposition sites, influence offspring dependency and change with the evolution of male‐only care in glassfrogs. Egg care appears ubiquitous among glassfrogs, with repeated evolutionary transitions from brief female‐only to extended male‐only care. Glassfrogs also exhibit a diversity of sex‐specific parental traits involving maternal egg‐jelly contributions, oviposition‐site choice, and egg‐attendance behaviors. We hypothesize these form functionally interchangeable suites of traits that mediate embryos' susceptibility to environmental risk. First, using parent‐removal field experiments, egg‐hydration assays, and comparative analyses, we found no evidence that evolutionary transitions in caring sex or care duration alter the adaptive functions or overall benefits of care (across eight species). Rather, the jelly contributions and oviposition‐site use associated with brief care influence embryo susceptibility to the same risks that are reduced by prolonged care. Next, we examined the diversity and evolutionary history of pre‐ and post‐zygotic parental traits, applying phylogenetic comparative methods to literature records and our field observations of 40 species (71 total, ~ 47 % of the family). Because pre‐zygotic maternal contributions determine embryo requirements, the evolution of male care might enable and/or compensate for reduced maternal contributions. Supporting this hypothesis, we found that the repeated evolution of complex male care is always associated with reductions in egg‐jelly and changes in oviposition sites. This phylogenetic pattern suggests that clutch phenotype might provide a general mechanism for the coevolution of parental investment in species with uniparental care. If different combinations of egg phenotypes and post‐zygotic care are ecologically equivalent, their interchangeability could allow parental traits to coevolve between the sexes without compromising offspring survival. Male‐only care is widespread in oviparous metazoans, occurring among annelids, molluscs, arthropods, fishes, and amphibians. Investigations of egg and clutch phenotypes offer new prospects for broadening research on the coevolutionary dynamics of parental care.

The nitrogen economic spectrum of legume stoichiometry and fixation strategy.

Leaf nitrogen concentration often is higher in leguminous plants, which associate with dinitrogen-fixing bacteria, compared with nonlegume plants. However, the range of nitrogen concentrations in legumes is wide, likely related to the range of nitrogen fixation strategies. We evaluated how carbon and nitrogen allocation to roots, stems and leaves is influenced by the type of strategy of nitrogen fixation regulation. We grew herbaceous annual legumes (Medicago truncatula, Hymenocarpos circinnatus and Vicia palaestina) under two nitrogen availability treatments (none/sufficient), with and without bacterial inoculation. We found facultative downregulation of the rate of nitrogen fixation when nitrogen was available in H.circinnatus, and an obligate similar fixation rate in both nitrogen treatments in M.truncatula and V.palaestina. Uninoculated plants invested more biomass in roots and contained lower nitrogen concentrations. However, nitrogen concentration in the entire plant and in the leaves was lower and more plastic in the species with a facultative fixation strategy, whereas species with an obligate fixation strategy also maintained high nitrogen concentrations. Our results suggest a suite of functional traits associated with the strategies of allocation and symbiotic nitrogen fixation. This suite of traits probably shapes successional and functional niches of different leguminous species in specious plant communities.

Leaf toughness as a mechanism of defence against spruce budworm

Toughness of leaves is an important defence mechanism of plants against insect herbivores and is generally linked to leaf fibre content. We explored the anatomical basis and the ecological role of needle toughness as a mechanism of defence against feeding initiation by second-instar spruce budworm (Choristoneura fumiferana) emerging from diapause. We first aimed at determining relationships between needle physico-chemical traits and toughness [specific leaf area (SLA), nitrogen, carbon, fibre, and water content, and C/N ratio]. Second, we tested the hypothesis that differences in needle toughness between balsam fir (Abies balsamea) and black spruce (Picea mariana) explain differences in the ability of young budworm to mine into a needle, asking whether nitrogen content or toughness is a better predictor of budworm mining success. Our results show first that needle toughness correlates with high cellulose content and that SLA is a good proxy. Second, needle toughness is a stronger predictor of mining success (defined as the number of larvae that entered a needle) of young budworm than nitrogen content. Our results suggest that needle toughness can be an important defensive trait in conifers, as suggested by the low mining rate exhibited by second-instar spruce budworm larvae feeding on 1-year-old black spruce foliage. The foliage of this host is tougher and has higher fibre content than balsam fir foliage. Differences in needle toughness, and associated differences in resistance to folivores, might be an important component in adaptive suites of traits constituting the different life-history strategies of these two sympatric species.

Ontogenetic consistency in oak defence syndromes

Abstract Plant species allocate resources to multiple defensive traits simultaneously, often leading to so‐called defence syndromes (i.e. suites of traits that are co-expressed across several species). While reports of ontogenetic variation in plant defences are commonplace, no study to date has tested for ontogenetic shifts in defence syndromes, and we know little about the ecological and evolutionary drivers of variation in plant defence syndromes across ontogeny. We tested for ontogenetic variation in plant defence syndromes by measuring a suite of defensive and nutritional traits on saplings and adult trees of 29 oak (Quercus, Fagaceae) species distributed across Europe, North America, and Asia. In addition, we investigated if these syndromes exhibited a phylogenetic signal to elucidate the nature of their macro‐evolutionary variation, whether they were associated with levels of herbivore pressure and climatic conditions, and if any such evolutionary and ecological patterns were contingent on ontogeny. Our analyses revealed three distinct oak defence syndromes: the first included species with high defences, the second species with high defences and low nutrient levels, and the third species with high nutrients and thinner leaves. Interestingly, these defence syndromes remained virtually unchanged across the two ontogenetic stages sampled. In addition, our analyses indicated no evidence for a phylogenetic signal in oak syndromes, a result consistent across ontogenetic stages. Finally, with respect to ecological factors, we found no effect of climatic conditions on defences for either ontogenetic stage, whereas defence syndromes were associated with differing levels of herbivory in adults but not saplings suggesting an association between herbivore pressure and syndrome type that is contingent on ontogeny. Synthesis. Together, these findings indicate that defence syndromes remain remarkably consistent across oak ontogenetic stages, are evolutionarily labile, and while they appear unrelated to climate, they do appear to be associated with herbivory levels in an ontogenetic‐dependent manner. Overall, this study builds towards a better understanding of ecological and evolutionary factors underlying multivariate plant defensive phenotypes.

Drivers of plant traits that allow survival in wetlands

Abstract Plants have developed a suite of traits to survive the anaerobic and anoxic soil conditions in wetlands. Previous studies on wetland plant adaptive traits have focused mainly on physiological aspects under experimental conditions, or compared the trait expression of the local species pool. Thus, a comprehensive analysis of potential factors driving wetland plant adaptive traits under natural environmental conditions is still missing. In this study, we analysed three important wetland adaptive traits, that is root porosity, root/shoot ratio and underwater photosynthetic rate, to explore driving factors using a newly compiled dataset of wetland plants. Based on 21 studies at 38 sites across different biomes, we found that root porosity was affected by an interaction of temperature and hydrological regime; root:shoot ratio was affected by temperature, precipitation and habitat type; and underwater photosynthetic rate was affected by precipitation and life‐form. This suggests that a variety of driving mechanisms affect the expression of different adaptive traits. The quantitative relationships we observed between the adaptive traits and their driving factors will be a useful reference for future global methane and denitrification modelling studies. Our results also stress that besides the traditionally emphasized hydrological driving factors, other factors at several spatial scales should also be taken into consideration in the context of future functional wetland ecology. A free Plain Language Summary can be found within the Supporting Information of this article.

Phenotypic divergence among threespine stickleback that differ in nuptial coloration.

By studying systems in their earliest stages of differentiation, we can learn about the evolutionary forces acting within and among populations and how those forces could contribute to reproductive isolation. Such an understanding would help us to better discern and predict how selection leads to the maintenance of multiple morphs within a species, rather than speciation. The postglacial adaptive radiation of the threespine stickleback (Gasterosteus aculeatus) is one of the best‐studied cases of evolutionary diversification and rapid, repeated speciation. Following deglaciation, marine stickleback have continually invaded freshwater habitats across the northern hemisphere and established resident populations that diverged innumerable times from their oceanic ancestors. Independent freshwater colonization events have yielded broadly parallel patterns of morphological differences in freshwater and marine stickleback. However, there is also much phenotypic diversity within and among freshwater populations. We studied a lesser‐known freshwater “species pair” found in southwest Washington, where male stickleback in numerous locations have lost the ancestral red sexual signal and instead develop black nuptial coloration. We measured phenotypic variation in a suite of traits across sites where red and black stickleback do not overlap in distribution and at one site where they historically co‐occurred. We found substantial phenotypic divergence between red and black morphs in noncolor traits including shape and lateral plating, and additionally find evidence that supports the hypothesis of sensory drive as the mechanism responsible for the evolutionary switch in color from red to black. A newly described third “mixed” morph in Connor Creek, Washington, differs in head shape and size from the red and black morphs, and we suggest that their characteristics are most consistent with hybridization between anadromous and freshwater stickleback. These results lay the foundation for future investigation of the underlying genetic basis of this phenotypic divergence as well as the evolutionary processes that may drive, maintain, or limit divergence among morphs.

Field cricket genome reveals the footprint of recent, abrupt adaptation in the wild.

Evolutionary adaptation is generally thought to occur through incremental mutational steps, but large mutational leaps can occur during its early stages. These are challenging to study in nature due to the difficulty of observing new genetic variants as they arise and spread, but characterizing their genomic dynamics is important for understanding factors favoring rapid adaptation. Here, we report genomic consequences of recent, adaptive song loss in a Hawaiian population of field crickets (Teleogryllus oceanicus). A discrete genetic variant, flatwing, appeared and spread approximately 15 years ago. Flatwing erases sound‐producing veins on male wings. These silent flatwing males are protected from a lethal, eavesdropping parasitoid fly. We sequenced, assembled and annotated the cricket genome, produced a linkage map, and identified a flatwing quantitative trait locus covering a large region of the X chromosome. Gene expression profiling showed that flatwing is associated with extensive genome‐wide effects on embryonic gene expression. We found that flatwing male crickets express feminized chemical pheromones. This male feminizing effect, on a different sexual signaling modality, is genetically associated with the flatwing genotype. Our findings suggest that the early stages of evolutionary adaptation to extreme pressures can be accompanied by greater genomic and phenotypic disruption than previously appreciated, and highlight how abrupt adaptation might involve suites of traits that arise through pleiotropy or genomic hitchhiking.

Prosociality and a Sociosexual Hypothesis for the Evolution of Same-Sex Attraction in Humans.

Human same-sex sexual attraction (SSSA) has long been considered to be an evolutionary puzzle. The trait is clearly biological: it is widespread and has a strong additive genetic basis, but how SSSA has evolved remains a subject of debate. Of itself, homosexual sexual behavior will not yield offspring, and consequently individuals expressing strong SSSA that are mostly or exclusively homosexual are presumed to have lower fitness and reproductive success. How then did the trait evolve, and how is it maintained in populations? Here we develop a novel argument for the evolution of SSSA that focuses on the likely adaptive social consequences of SSSA. We argue that same sex sexual attraction evolved as just one of a suite of traits responding to strong selection for ease of social integration or prosocial behavior. A strong driver of recent human behavioral evolution has been selection for reduced reactive aggression, increased social affiliation, social communication, and ease of social integration. In many prosocial mammals sex has adopted new social functions in contexts of social bonding, social reinforcement, appeasement, and play. We argue that for humans the social functions and benefits of sex apply to same-sex sexual behavior as well as heterosexual behavior. As a consequence we propose a degree of SSSA, was selected for in recent human evolution for its non-conceptive social benefits. We discuss how this hypothesis provides a better explanation for human sexual attractions and behavior than theories that invoke sexual inversion or single-locus genetic models.

Fruit syndromes in Viburnum: correlated evolution of color, nutritional content, and morphology in bird-dispersed fleshy fruits

PremiseA key question in plant dispersal via animal vectors is where and why fruit colors vary between species and how color relates to other fruit traits. To better understand the factors shaping the evolution of fruit color diversity, we tested for the existence of syndromes of traits (color, morphology, and nutrition) in the fruits of Viburnum. We placed these results in a larger phylogenetic context and reconstructed ancestral states to assess how Viburnum fruit traits have evolved across the clade.ResultsWe find that blue Viburnum fruits are not very juicy, and have high lipid content and large, round endocarps surrounded by a small quantity of pulp. Red fruits display the opposite suite of traits: they are very juicy with low lipid content and smaller, flatter endocarps. The ancestral Viburnum fruit may have gone through a sequence of color changes before maturation (green to yellow to red to black), though our reconstructions are equivocal. In one major clade of Viburnum (Nectarotinus), fruits mature synchronously with reduced intermediate color stages. Most transitions between fruit colors occurred in this synchronously fruiting clade.ConclusionsIt is widely accepted that fruit trait diversity has primarily been driven by the differing perceptual abilities of bird versus mammal frugivores. Yet within a clade of largely bird-dispersed fruits, we find clear correlations between color, morphology, and nutrition. These correlations are likely driven by a shift from sequential to synchronous development, followed by diversification in color, nutrition, and morphology. A deeper understanding of fruit evolution within clades will elucidate the degree to which such syndromes structure extant fruit diversity.

Fungal Traits Important for Soil Aggregation.

Soil structure, the complex arrangement of soil into aggregates and pore spaces, is a key feature of soils and soil biota. Among them, filamentous saprobic fungi have well-documented effects on soil aggregation. However, it is unclear what properties, or traits, determine the overall positive effect of fungi on soil aggregation. To achieve progress, it would be helpful to systematically investigate a broad suite of fungal species for their trait expression and the relation of these traits to soil aggregation. Here, we apply a trait-based approach to a set of 15 traits measured under standardized conditions on 31 fungal strains including Ascomycota, Basidiomycota, and Mucoromycota, all isolated from the same soil. We find large differences among these fungi in their ability to aggregate soil, including neutral to positive effects, and we document large differences in trait expression among strains. We identify biomass density, i.e., the density with which a mycelium grows (positive effects), leucine aminopeptidase activity (negative effects) and phylogeny as important factors explaining differences in soil aggregate formation (SAF) among fungal strains; importantly, growth rate was not among the important traits. Our results point to a typical suite of traits characterizing fungi that are good soil aggregators, and our findings illustrate the power of employing a trait-based approach to unravel biological mechanisms underpinning soil aggregation. Such an approach could now be extended also to other soil biota groups. In an applied context of restoration and agriculture, such trait information can inform management, for example to prioritize practices that favor the expression of more desirable fungal traits.

Identification of suites of traits that explains drought resistance and phenological patterns of plants in a semi-arid grassland community

Grassland ecosystems are comprised of plants that occupy a wide array of phenological niches and vary considerably in their ability to resist the stress of seasonal soil-water deficits. Yet, the link between plant drought resistance and phenology remains unclear in perennial grassland ecosystems. To evaluate the role of soil water availability and plant drought tolerance in driving phenology, we measured leaf hydraulic conductance (Ksat), resistance to hydraulic failure (P50), leaf gas exchange, plant and soil water stable isotope ratios (δ18O), and several phenology metrics on ten perennial herbaceous species in mixed-grass prairie. The interaction between P50 and δ18O of xylem water explained 67% of differences in phenology, with lower P50 values associated with later season activity, but only among shallow-rooted species. In addition, stomatal control and high water-use efficiency also contributed to the late flowering and late senescence strategies of plants that had low P50 values and relied upon shallow soil water. Alternatively, plants with deeper roots did not possess drought-tolerant leaves, but had high hydraulic efficiency, contributing to their ability to efficiently move water longer distances while maintaining leaf water potential at relatively high values. The suites of traits that characterize these contrasting strategies provide a mechanistic link between phenology and plant-water relations; thus, these traits could help predict grassland community responses to changes in water availability, both temporally and vertically within the soil profile.

Functional Morphology and Morphological Diversification of Hind Limb Cross-Sectional Traits in Mustelid Mammals.

SynopsisLocomotor habits in mammals are strongly tied to limb bones’ lengths, diameters, and proportions. By comparison, fewer studies have examined how limb bone cross-sectional traits relate to locomotor habit. Here, we tested whether climbing, digging, and swimming locomotor habits reflect biomechanically meaningful differences in three cross-sectional traits rendered dimensionless— cross-sectional area (CSA), second moments of area (SMA), and section modulus (MOD)—using femora, tibiae, and fibulae of 28 species of mustelid. CSA and SMA represent resistance to axial compression and bending, respectively, whereas MOD represents structural strength. Given the need to counteract buoyancy in aquatic environments and soil’s high density, we predicted that natatorial and fossorial mustelids have higher values of cross-sectional traits. For all three traits, we found that natatorial mustelids have the highest values, followed by fossorial mustelids, with both of these groups significantly differing from scansorial mustelids. However, phylogenetic relatedness strongly influences diversity in cross-sectional morphology, as locomotor habit strongly correlates with phylogeny. Testing whether hind limb bone cross-sectional traits have evolved adaptively, we fit Ornstein–Uhlenbeck (OU) and Brownian motion (BM) models of trait diversification to cross-sectional traits. The cross-sectional traits of the femur, tibia, and fibula appear to have, respectively, diversified under a multi-rate BM model, a single rate BM model, and a multi-optima OU model. In light of recent studies on mustelid body size and elongation, our findings suggest that the mustelid body plan—and perhaps that of other mammals—is likely the sum of a suite of traits evolving under different models of trait diversification.

Fluctuating environments during early development can limit adult phenotypic flexibility: insights from an amphibious fish.

The interaction between developmental plasticity and the capacity for reversible acclimation (phenotypic flexibility) is poorly understood, particularly in organisms exposed to fluctuating environments. We used an amphibious killifish (Kryptolebias marmoratus) to test the hypotheses that organisms reared in fluctuating environments (i) will make no developmental changes to suit any one environment because fixing traits to suit one environment could be maladaptive for another, and (ii) will be highly phenotypically flexible as adults because their early life experiences predict high environmental variability in the future. We reared fish under constant (water) or fluctuating (water-air) environments until adulthood and assessed a suite of traits along the oxygen cascade (e.g. neuroepithelial cell density and size, cutaneous capillarity, gill morphology, ventricle size, red muscle morphometrics, terrestrial locomotor performance). To evaluate the capacity for phenotypic flexibility, a subset of adult fish from each rearing condition was then air-exposed for 14 days before the same traits were measured. In support of the developmental plasticity hypothesis, traits involved with O2 sensing and uptake were largely unaffected by water-air fluctuations during early life, but we found marked developmental changes in traits related to O2 transport, utilization and locomotor performance. In contrast, we found no evidence supporting the phenotypic flexibility hypothesis. Adult fish from both rearing conditions exhibited the same degree of phenotypic flexibility in various O2 sensing- and uptake-related traits. In other cases, water-air fluctuations attenuated adult phenotypic flexibility despite the fact that phenotypic flexibility is hypothesized to be favoured when environments fluctuate. Overall, we conclude that exposure to environmental fluctuations during development in K. marmoratus can dramatically alter the constitutive adult phenotype, as well as diminish the scope for phenotypic flexibility in later life.

Species traits predict stream‐fish invaders in an Appalachian (U.S.A.) river basin

Abstract We compared the influence of biological traits (morphology, physiology, reproduction, and life history), ecological traits (geographic distribution, habitat associations, food habits), and introduction attributes (propagule pressure, human use of a species, residence time) on invasion success of native and introduced stream fishes during the colonisation and spread stages in an Appalachian (U.S.A.) river basin. Colonisation success was positively related to residence time, benthic feeding, an equilibrium life‐history strategy, and nest spawning. Successful spread was associated with tolerance to increased temperature and an equilibrium life‐history strategy. The spread of introduced fishes was negatively related to gamefish status. No effect of propagule pressure was detected. Traits linked to invasion success were consistent with the hypothesis that human land‐use practices increase the invasibility of highland catchments by creating novel conditions better suited to lowland and equilibrium invaders. We found biological traits to be more useful than ecological traits in predicting invasion success and suggesting invasion mechanisms. Parental care and nest association can facilitate invasions over large spatial extents for both native and introduced fishes. Analyses of suites of traits can reveal mechanisms of invasions and tactics for controlling them; such mechanisms and tactics may be system‐specific and scale‐dependent.

Analysis of an invasion in the community context: a case study about differences and similarities between native and non-native shrubs

Although much effort has been devoted to identify plant traits related to invasiveness, the success of this approach remains elusive, likely because the relevance of particular traits for invasions is context-dependent. We studied plant invasions in the context of the recipient community in a mountain ecosystem of western Argentina by comparing traits between two non-native shrubs, Rosa canina and R. rubiginosa, and all native shrubs coexisting with them. We expected that both rose species differed from natives in traits related to an acquisitive strategy of resources. We grouped native shrubs into species with high (abundant) and low abundance (rare). We expected smaller differences between non-natives and abundant natives than between non-natives and rare natives, as shrub abundance may depend on possessing a particular suite of traits, independent of species origin. We found that both rose species were different from native shrubs when analyzing all traits in combination. Non-natives presented a strategy that may allow them to acquire resources and grow at faster rates than natives, offering support to our prediction. Yet, native and non-native shrub species overlapped in flower phenology. When comparing non-natives to abundant and rare natives, we found no support for our expectation, as non-natives did not show smaller differences with abundant natives, but shared similarities with rare natives. This pattern suggests successful coexistence via niche partitioning, but this possibility deserves future studies. Our work highlights the importance of considering non-native plant traits in a community context to further understand the invasion process.