Summary 1.Intraspecific trait variability is a crucial, often neglected, component of functional diversity (FD) in ecological communities. In particular, uncertainty remains as to the importance of intraspecific variability in the quantification of FD. 2. To explore this uncertainty, we propose two methods addressing two critical and complementary, but largely unexplored, questions: (i) what is the extent of within-vs. between-species FD in different communities? and (ii) to what extent is the response of FD to environment because of compositional turnover vs. intraspecific trait variability across habitats? The methods proposed to address these questions are built on a variance partitioning approach and have the advantage of including species relative abundance, therefore taking into account species dominance and rarity. For each of the questions, we illustrate one dedicated case study in semi-natural grasslands with associated sampling strategies. 3. The decomposition of total community variance into within-vs. between-species effects can be implemented in a manner similar to the decomposition of quadratic entropy on pairwise individual dissimilarity. The approach can be applied with single and multiple traits, although it proves more informative for single traits. It can prove particularly useful when assessing the role of different sources of trait variability in the assembly of communities. 4. The assessment of the relative contribution of intraspecific trait variability and species turnover to the response of FD to environment is based on a variance partitioning comparing FD indices computed (i) either using individuals measured in a specific habitat alone (FDhabitat) or (ii) all individuals measured across different habitats (FDfixed). This approach provides a more complete understanding of the response of FD to environment. 5. We further propose a guide to apply these two methods and to choose the most suitable method for intraspecific trait measurements. Assessing the role of intraspecific trait variability should allow a more comprehensive understanding of the processes that link species and ecosystems.

I.Introduction: continuing to face up to root ecology's challenges 975 II.Semantics: defining concepts for better understanding and communication 977III. Species-level vs ecosystem-level measurements 978

Aim Temporal dynamics of biodiversity along tropical elevational gradients are unknown. We studied seasonal changes of Lepidoptera biodiversity along the only complete forest elevational gradient in the Afrotropics. We focused on shifts of species richness patterns, seasonal turnover of communities and seasonal shifts of species’ elevational ranges, the latter often serving as an indicator of the global change effects on mountain ecosystems. Location Mount Cameroon, Cameroon. Taxon Butterflies and moths (Lepidoptera). Methods We quantitatively sampled nine groups of Lepidoptera by bait‐trapping (16,800 trap‐days) and light‐catching (126 nights) at seven elevations evenly distributed along the elevational gradient from sea level (30 m a.s.l.) to timberline (2,200 m a.s.l.). Sampling was repeated in three seasons. Results Altogether, 42,936 specimens of 1,099 species were recorded. A mid‐elevation peak of species richness was detected for all groups but Eupterotidae. This peak shifted seasonally for five groups, most of them ascending during the dry season. Seasonal shifts of species’ elevational ranges were mostly responsible for these diversity pattern shifts along elevation: we found general upward shifts in fruit‐feeding butterflies, fruit‐feeding moths and Lymantriinae from beginning to end of the dry season. Contrarily, Arctiinae shifted upwards during the wet season. The average seasonal shifts of elevational ranges often exceeded 100 m and were even several times higher for numerous species. Main conclusions We report seasonal uphill and downhill shifts of several lepidopteran groups. The reported shifts can be driven by both delay in weather seasonality and shifts in resource availability, causing phenological delay of adult hatching and/or adult migrations. Such shifts may lead to misinterpretations of diversity patterns along elevation if seasonality is ignored. More importantly, considering the surprising extent of seasonal elevational shifts of species, we encourage taking account of such natural temporal dynamics while investigating the global climate change impact on communities of Lepidoptera in tropical mountains.

Phenotypes of plants, and thus their ecology and evolution, can be affected by the environmental conditions experienced by their parents, a phenomenon called parental effects or transgenerational plasticity. However, whether such effects are just passive responses or represent a special type of adaptive plasticity remains controversial because of a lack of solid tests of their adaptive significance. Here, we investigated transgenerational effects of different nutrient environments on the productivity, carbon storage and flowering phenology of the perennial plant Plantago lanceolata, and whether these effects are influenced by seasonal variation in the maternal environment. We found that maternal environments significantly affected the offspring phenotype, and that plants consistently produced more biomass and had greater root carbohydrate storage if grown under the same environmental conditions as experienced by their mothers. The observed transgenerational effects were independent of the season in which seeds had matured. We therefore conclude that transgenerational effects on biomass and carbon storage in P. lanceolata are adaptive regardless of the season of seed maturation.

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