Combining taxon-by-trait and taxon-by-site matrices for analysing trait patterns of macroinvertebrate communities: a rejoinder to Monaghan & Soares (2014)

In a recent paper, Heino, Schmera & Erős (2013) provided an overview of trait 58 patterns of stream communities from a macroecological perspective. In this paper , 59 reference was made to Gayraud et al . (2003) , who showed that abundance - weighted 60 traits were less powe rful than presence - absence weighted traits in discriminating 61 communities under different degrees of human impacts , and to Statzner & Beche 62 (2010) , who therefore advocated the use of the second type of weighting for practical 63 biomonitoring due to logis tic constrains ( e.g. sorting of qualitative samples makes 64 3 assessment program me s more cost effective) . H eino et al . (2013) pointed out that 65 t hese findings contradict the results of taxon - based analyses which suggest that , if 66 taxa are weighted by their abund ance , then communities are better separated in 67 relation to environmental variation than when taxa are weighted only by their 68 presence . Based on an overview of the literature, Heino et al . (2013) concluded that 69 results of presence - and abundance - based analy ses should be evaluated carefully 70 when examining traits of organisms, because differences among studies can reflect 71 both methodological (i.e. handling of data) and real ecological differences (see p. 72 1549 in H eino et al ., 2013 ) . More recently, Monaghan & S oares (2014 ) stated that (1) 73 H eino et al . (2013) identified the weak explanatory power of abundance data as a 74 major limitation of macroinvertebrat e trait analysis and that (2) the log - transformation 75 of abundance data may cause anomalies in trait - based anal yses. W e disagree with 76 both conclusions , because (1) H eino et al . (2013) did not actually state this (see 77 above) and because (2), in our view, log - transformation of abundance data in trait - 78 based analyses can also be meaningful . To reveal the causes of thes e differ ing views , 79 we go through the examples provided by M onaghan & Soares (2014) and examine 80 how traits can be weighted by the presence, abundance and log - transformed 81 abundance of the taxa . To do this, firs t we define the terminology used here , comment 82 o n the approach of M onaghan & Soares (2014) and show how this procedure should 83 be performed

Field experiment on the relationship between drift and benthic densities of aquatic insects in tropical streams (Ivory Coast) : 3 : Tricoptera

1) En se fondant sur des expériences #in situ en gouttières, la dérive des Tricoptères est reliée à leur densité benthique et à différents facteurs abiotiques des rivières de Côte d'Ivoire (Afrique de l'Ouest). Les représentants des familles #Hydropsychidae, Philopotamidae, Hydroptilidae et #Leptoceridae$ sont considérés en détail. 2) La dérive est maximale durant la nuit aussi bien chez les jeunes larves que les âgées. 3) La dérive d'un groupe larvaire (certains stades, certaines espèces ou certains taxons de rang supérieur) est plus souvent reliée à la densité des autres groupes larvaires qu'à sa propre densité benthique. 4) L'autorégulation des densités benthiques les plus grandes par émigration au moyen de la dérive n'est pas prouvée. 5) Il n'y a pas de relation entre la dérive et les facteurs abiotiques. 6) Les taux de dérive diffèrent aussi bien entre les taxons qu'entre les stades larvaires (classes de taille) à l'intérieur d'un taxon. Les larves nouvellement écloses ont un taux de dérive très élevé tandis que les derniers stades larvaires dérivent le moins

Persistence in the longitudinal distribution of lotic insects in a changing climate: a tale of two rivers

The longitudinal distribution of many taxa in rivers is influenced by temperature. Here we took advantage of two older datasets on net-spinning caddisflies (Hydropsychidae) from contrasting European rivers to assess changes in species occurrence and relative abundance along the river by resampling the same sites, postulating that an increase in river temperature over the intervening period should have resulted in cool-adapted species retreating into the headwaters and warm adapted species expanding upstream. Distributional changes in the Welsh Usk were slight between 1968/69 and 2010, one rare species appearing at a single headwater site and one warm-adapted species disappearing from the main river. Distributional changes in the French Loire, between 1989–93 and 2005, were similarly modest, with no consistent movement of species up- or downstream. We estimate that the decadal rate of increase in the mean summer daily maximum in the Usk was only 0.1 °C at one ‘summer cool’ headwater site, while a neighbouring ‘summer warm’ tributary increased by 0.16 °C per decade, and the main river by 0.22 °C. The Loire is warmer than the Usk and the mean decadal rates of increase, over the period 1989–2005, at three sites along the lower reaches were 0.39, 0.48 and 0.77 °C. Increases in stream and river temperature, therefore, were spatially variable and were not associated with consistent upstream movement of species in either of these (very different) rivers. We conclude that either the temperature increases have hitherto been insufficient to affect species distribution or, more speculatively, that it may not be possible for river organisms (that do not respond only to temperature) to move upstream because of a developing spatial mismatch between key habitat characteristics, some of them changing with the climate but others not

Habitat filtering determines spatial variation of macroinvertebrate community traits in northern headwater streams

Although our knowledge of the spatial distribution of stream organisms has been increasing rapidly in the last decades, there is still little consensus about trait-based variability of macroinvertebrate communities within and between catchments in near-pristine systems. Our aim was to examine the taxonomic and trait based stability vs. variability of stream macroinvertebrates in three high-latitude catchments in Finland. The collected taxa were assigned to unique trait combinations (UTCs) using biological traits. We found that only a single or a highly limited number of taxa formed a single UTC, suggesting a low degree of redundancy. Our analyses revealed significant differences in the environmental conditions of the streams among the three catchments. Linear models, rarefaction curves and beta-diversity measures showed that the catchments differed in both alpha and beta diversity. Taxon- and trait-based multivariate analyses also indicated that the three catchments were significantly different in terms of macroinvertebrate communities. All these findings suggest that habitat filtering, i.e., environmental differences among catchments, determines the variability of macroinvertebrate communities, thereby contributing to the significant biological differences among the catchments. The main implications of our study is that the sensitivity of trait-based analyses to natural environmental variation should be carefully incorporated in the assessment of environmental degradation, and that further studies are needed for a deeper understanding of trait-based community patterns across near-pristine streams

A cost-effective method to quantify biological surface sediment reworking

We propose a simple and inexpensive method to determine the rate and pattern of surface sediment reworking by benthic organisms. Unlike many existing methods commonly used in bioturbation studies, which usually require sediment sampling, our approach is fully non-destructive and is well suited for investigating non-cohesive fine sediments in streams and rivers. Optical tracer (e.g., luminophores or coloured sand) disappearance or appearance is assessed through time based on optical quantification of surfaces occupied by tracers. Data are used to calculate surface sediment reworking (SSR) coefficients depicting bioturbation intensities. Using this method, we evaluated reworking activity of stream organisms (three benthic invertebrates and a fish) in laboratory microcosms mimicking pool habitats or directly in the field within arenas set in depositional zones. Our method was sensitive enough to measure SSR as low as 0.2 cm2.d-1, such as triggered by intermediate density (774 m-2) of Gammarus fossarum (Amphipoda) in microcosms. In contrast, complex invertebrate community in the field and a fish (Barbatula barabatula) in laboratory microcosms were found to yield to excessively high SSR (>60 cm2.d-1). Lastly, we suggest that images acquired during experiments can be used for qualitative evaluation of species-specific effects on sediment distribution

The generality of changes in the trait composition of fish and invertebrate communities after flow restoration in a large river (French Rhône)

1. A multiple-trait-based approach can provide predictions and interpretations of the responses of freshwater communities to river restoration that apply in different taxonomic contexts. We compared the observed and predicted effects of restoration on sets of traits in fish and invertebrate communities in four reaches of the Rhône River. Restoration included minimum flow increases in three bypassed main channels and the reconnection of eight floodplain channels. 2. Predictions (described in detail in three other articles in this Special Issue) were based on habitat models that related the density of modelled taxa to their physical habitats. We used trait information extracted from the literature to translate predicted taxonomic changes into predicted changes in traits. Observed changes in traits calculated for modelled taxa and for all taxa in the community were both compared to predictions. 3. In 10 of 12 cases, observed changes in traits correlated with predicted ones. With few exceptions, the agreement was higher for fish and invertebrates in the main channels than for invertebrates in floodplain channels. Predictions translated to the trait category level improved those at the taxonomic level in 5/6 and 4/6 cases for modelled taxa and all taxa, respectively. However, the improvement was statistically significant according to a null model for 1/6 and 3/6 cases for modelled taxa and all taxa, respectively. 4. The validation of trait predictions suggested that traits related to locomotion and attachment, as well as general biology and physiology, were particularly suited to predicting and understanding the effects of physical restoration. For example, after restoration, clingers and passive filter feeders dominated invertebrate communities in the main channels, whereas invertebrate communities in the floodplain underwent a selection of traits frequent in running water (clingers, flattened shape and gill respiration). Within fish communities, the periodic life-history strategy that characterises fish species in downstream reaches (long life span, large body, late sexual maturity) increased with restoration, whereas the opportunistic strategy decreased. 5. Our results suggest that a better understanding of how hydraulics shapes traits in riverine systems is critically needed for assessing the effects of restoration measures impacting flow. In addition, existing trait databases (especially for fish) should be expanded to better reflect the energetic trade-offs that organisms must make in various flow contexts

Impact Factor: outdated artefact or stepping-stone to journal certification?

A review of Garfield's journal impact factor and its specific implementation as the Thomson Reuters Impact Factor reveals several weaknesses in this commonly-used indicator of journal standing. Key limitations include the mismatch between citing and cited documents, the deceptive display of three decimals that belies the real precision, and the absence of confidence intervals. These are minor issues that are easily amended and should be corrected, but more substantive improvements are needed. There are indications that the scientific community seeks and needs better certification of journal procedures to improve the quality of published science. Comprehensive certification of editorial and review procedures could help ensure adequate procedures to detect duplicate and fraudulent submissions.Comment: 25 pages, 12 figures, 6 table