Intraspecific Functional Variability Research Articles

Intraspecific Functional Variability and Functional Changes Along Environmental Gradients Associated to Mangrove Forest Zonation in West-Central Mexico

Intraspecific Functional Variability and Functional Changes Along Environmental Gradients Associated to Mangrove Forest Zonation in West-Central Mexico

The Role of Inter- and Intraspecific Variations in Grassland Plant Functional Traits along an Elevational Gradient in a Mediterranean Mountain Area.

Elevational gradients offer special opportunities to investigate the relative role of intraspecific and interspecific trait variations in relation to stress gradients. We used an altitudinal gradient in the Mediterranean (Mt Velino, Central Italy) to study (1) how community-weighted means (CWM) and nonweighted means (CM) vary with elevation for plant height, specific leaf area, and seed mass; and (2) how variation patterns differ for inter- and intraspecific functional variability. We tested (1) if elevation influences community functional composition on the basis of the adaptive value of plant traits and (2) if the latter shows intraspecific variations according to the species’ ability to cope with local conditions. We found that different traits showed different patterns, which can be linked to the function they express. Differences between communities were influenced more by differences between their traits (CM) than by the relative species coverage (CWM). Both highest and lowest elevations were the most selective due to their particularly severe climatic conditions. Intermediate elevations were the most favorable thanks to less constraining climatic conditions. Interspecific trait variability was the most relevant component, indicating a low plant ability to cope with environmental variations through phenotypic plasticity.

Inter- and intraspecific functional variability of aquatic fungal decomposers and freshwater ecosystem processes

Although considerable intraspecific trait variation is common, research dedicated to ecosystem functioning has focused mainly on species diversity. Organic matter breakdown, a key ecosystem-level process in woodland streams is mainly driven by aquatic hyphomycetes. These aquatic fungal decomposers constitute a critical link between plant litter and invertebrate detritivores in detritus-based food webs in streams. In this study, we evaluated the functional variability across a set of ten isolates each belonging to five widespread aquatic hyphomycete species, namely Articulospora tetracladia, Anguillospora crassa, Lemonniera terrestris, Neonectria lugdunensis and Tetracladium marchalianum. All the isolates originated from undisturbed streams. We estimated inter- and intraspecific variability on growth rates, litter decomposition and sporulation rates of the isolates. In addition, we also assessed the invertebrate consumption rates on leaves colonized by different isolates. Significant differences were observed within the fungal species in growth rates (A. crassa, L. terrestris, N. lugdunensis and T. marchalianum), leaf litter decomposition (A. tetracladia, L. terrestris and N. lugdunensis) and sporulation rates (A. crassa, A. tetracladia, L. terrestris and N. lugdunensis). The relative consumption rates of the shredder Schizopelex festiva significantly differed when fed with leaves colonized by isolates of L. terrestris and N. lugdunensis, however differences were not seen when fed with leaves conditioned by different species. Overall, results indicate substantial intraspecific functional variability among the isolates of aquatic hyphomycetes. Besides, our study also provides a novel insight that intraspecific functional variability is a natural phenomenon exhibited by isolates not only from polluted but also from undisturbed streams. Here the isolates demonstrated marked inter- and intraspecific functional variability, calling for a greater understanding of the functional role of aquatic hyphomycetes and its ability to influence higher trophic levels.

Accounting for intraspecific diversity when examining relationships between non-native species and functional diversity.

Quantifying changes in functional diversity, the facet of biodiversity accounting for the biological features of organisms, has been advocated as one of the most integrative ways to unravel how communities are affected by human-induced perturbations. The present study assessed how functional diversity patterns varied among communities that differed in the degree to which non-native species dominated the community in temperate lake fish communities and whether accounting for intraspecific functional variability could provide a better understanding of the variation of functional diversity across communities. Four functional diversity indices were computed for 18 temperate lake fish communities along a gradient of non-native fish dominance using morphological functional traits assessed for each life-stage within each species. First, we showed that intraspecific variability in functional traits was high and comparable to interspecific variability. Second, we found that non-native fish were functionally distinct from native fish. Finally, we demonstrated that there was a significant relationship between functional diversity and the degree to which non-native fish currently dominated the community and that this association could be better detected when accounting for intraspecific functional variability. These findings highlighted the importance of incorporating intraspecific variability to better quantify the variation of functional diversity patterns in communities facing human-induced perturbations.

Biological invasions undermine the functional diversity of fish community in a large subtropical river

Biological invasions are considered to be one of the main threats to biodiversity. Invasions lead to a loss of native species, changes to species composition, and a shift in the functioning and stability of ecosystems. In this study, derived from nine consecutive years of monitoring data and based on morphological functional trait values measured at the individual-level, we quantified the functional differences between native and non-native fish species and further assessed how biological invasions impact on species richness and functional diversity in the large subtropical Pearl River in southern China. Specifically, we differentiated intraspecific functional variability by separating individuals of a species according to their different life stages. Our results provided strong evidence that native and non-native fish were significantly different in their functional attributes. Invasion caused no obvious change in species richness; however, the yearly increase in non-native populations was accompanied by a significant decrease in functional niches of native species and change in several aspects of functional diversity in the fish community. Decreasing functional richness, and increasing functional divergence and specialization, indicated that most native species had been replaced by non-native species with different specific functional traits, which may affect ecosystem stability. Notably, this study provided empirical evidence that functional diversity was more sensitive to biological invasions than species richness. Our results show that control of non-native aquatic species is both necessary and urgent in the Pearl River. An understanding of the processes described in this study can form the basis of conservation in fish community, which is critical to sustainable and successful fisheries.

Drought stress inducing intraspecific variability in Potentilla tabernaemontani (Rosaceae), a calcareous grassland species

Background and aims – Calcareous grasslands are among the most species-rich habitats in Western Europe. Populations of plant species characterizing these ecosystems are naturally submitted to high variability in environmental conditions at the very local scale, resulting in pronounced variation in functional traits. Individuals located on xeric parts of calcareous grasslands are characterized by plant traits that potentially ensure more successful performance under stressful conditions. In the context of increased frequency of summer heat waves based on climate change, our aim was to determine a possible intraspecific variability in drought response among individuals of one calcareous grassland plant species.Methods – A greenhouse experiment was set up to follow survival of Potentilla tabernaemontani Asch. individuals according to their habitat of origin (xeric or mesic parts of Belgian calcareous grasslands) and the treatment applied (low or high drought stress).Key results – The results demonstrated that individuals originating from xeric parts survived drought stress better than individuals from mesic parts of calcareous grasslands. Specific leaf area (SLA) of all individuals was very low in the experiment, allowing them to decrease water loss during drought stress. Leaf production was lower for individuals exposed to high drought stress while flower production was higher. That potentially expressed a trade-off between tolerance to water stress, individual growth and reproduction. Conclusions – Local scale environmental heterogeneity deserves to be considered in conservation and restoration plans as it induces intraspecific functional variability between individuals and impacts individuals’ ability to survive drought stress.

Patterns and origin of intraspecific functional variability in a tropical alpine species along an altitudinal gradient

Background : Intraspecific functional variability (IFV) along altitudinal gradients is a powerful proxy to infer the responses of plants to abrupt environmental changes. We envisage that IFV shows distinctive patterns in tropical and extratropical alpine regions. Aims : To characterise the patterns and explore the origin of IFV in a tropical alpine species in a context of upward range extension. Methods : We examined variations in a series of plant functional traits in Lasiocephalus ovatus, inside and outside a nurse plant along a 600 m altitudinal gradient in the Ecuadorian Andes, and we studied its genetic variability. Results : More conservative traits were developed at higher elevation, in contrast to extratropical alpine plants, which commonly develop opportunistic traits in response to late snowmelt close to their upper altitudinal limit. The presence of nurse cushions did not alter this trend. Increasing genetic distance along the gradient suggested that IFV might be partly genetically induced. Conclusions : Our data combined with existing literature in tropical alpine environments lead the way to a stimulating scientific challenge: determining if patterns of plant altitudinal distribution in tropical alpine areas in response to climate change are predictable from patterns described in extratropical alpine areas.

A multi‐trait approach reveals the structure and the relative importance of intra‐ vs. interspecific variability in plant traits

Summary 1. Functional traits have been extensively used to describe, group and rank species according to their functions. There is now growing evidence that intraspecific functional variability, as well as interspecific variability, can have significant effects on community dynamics and ecosystem functioning. A core hypothesis for the use of functional traits expressed as species means, that their intraspecific variability is negligible compared with their interspecific variability, has however been too rarely tested empirically. We then addressed four questions: Is intraspecific functional variability across species ranges negligible compared with interspecific variability? Are the major resource economics trade‐off and functional strategies robust to individual trait variability? Are species rankings or ordination robust across species ranges once considering intraspecific variability? Can species be discriminated by their leaf traits? 2. Using an environmentally stratified sampling design within an alpine catchment, we collected five functional traits for 13 common plant species with contrasting life histories and traits. Several populations from a range of environmental conditions were then sampled for each species across their ranges. 3. With an original combination of single‐trait and multi‐trait analyses, we highlighted a non‐negligible contribution of intraspecific variability to overall functional trait variability (∼30%). Although not affecting general and well‐known functional trade‐offs and strategies, intraspecific functional variability had the potential to alter species ordination and produced a functional continuum rather than a clear‐cut species classification. 4. Deciding whether intraspecific functional variability can be considered as negligible – species being represented by mean trait values –, or not – species being represented by multivariate trait distributions –, is an essential question for multiple ecological issues. However, this decision cannot be generic, but will depend on the studied system and selected traits and species, as well as on study objectives.

Intraspecific functional variability: extent, structure and sources of variation

Summary 1. Functional traits are increasingly used to investigate community structure, ecosystem functioning or to classify species into functional groups. These functional traits are expected to be variable between and within species. Intraspecific functional variability is supposed to influence and modulate species responses to environmental changes and their effects on their environment. However, this hypothesis remains poorly tested and species are mostly described by mean trait values without any consideration of variability in individual trait values. 2. In this study, we quantify the extent of intraspecific plant functional trait variability, its spatial structure and its response to environmental factors. Using a sampling design structured along two direct and orthogonal climatic gradients in an alpine valley, we quantified and analysed the intraspecific variability for three functional traits (height, leaf dry matter content and leaf nitrogen content) measured on sixteen plant species with contrasting life histories. 3. Results showed a large variability of traits within species with large discrepancies between functional traits and species. This variability did not appear to be structured within populations. Between populations, the overall variability was partly explained by the selected gradients. Despite the strong effects of temperature and radiation on trait intraspecific variability, the response curves of traits along gradients were partly idiosyncratic. 4. Synthesis. Giving a comprehensive quantification of intraspecific functional variability through the analysis of an original data set, we report new evidence that using a single trait value to describe a given species can hide large functional variation for this species along environmental gradients. These findings suggest that intraspecific functional variability should be a concern for ecologists and its recognition opens new opportunities to better understand and predict ecological patterns in a changing environment. Further analyses are, however, required to compare inter‐ and intraspecific variability.