Parallel assemblage structures in Mediterranean marine amphipods revealed by beta diversity partitioning

Relying on a purely taxonomic view of diversity may ignore the fact that ecological communities can be constituted of species having both distinct evolutionary histories and functional characteristics. Thus, considering how the multiple facets of diversity vary along environmental and geographic gradients may provide insights into the role of historic processes and current environmental changes in determining the divergence or convergence of lineages and functions, ultimately influencing the way species assemble across space. However, analyses can be somehow flawed by the choice of traits being analysed, as they should capture the whole functional variability of species in order to assess the relationship between phylogenetic and functional diversity along a gradient. When continuous measures of functional diversity based on a variety of different traits are absent, the use of functional traits known to show strong phylogenetic signal can help elucidating such relationship. By using distributional, traits and taxonomic-distance information, we explored how the taxon, functional and phylogenetic community composition (co)vary along spatial and environmental gradients in seagrass amphipod metacommunity within the Mediterranean Sea. We used beta diversity partitioning and null models to determine the role of deterministic and stochastic processes on the replacement and the net loss/gain of species, lineages and highly conserved β-niche traits. We showed that dispersal-based processes are the main determinants of the high taxonomic and phylogenetic beta diversity, while niche-based processes explain the low functional dissimilarity among assemblages. Moreover, phylogenetic and functional beta diversity showed contrasting patterns when controlling for the underlying taxonomic composition, with the former being not significantly different and the latter significantly lower than expected. Our results suggest the key role of historical and biogeographic processes in determining the present-day patterns of community assembly and species turnover, providing also evidence for parallel assemblage structures in Mediterranean seagrass amphipods.

Eukaryotic Communities in Bromeliad Phytotelmata: How Do They Respond to Altitudinal Differences?

Bromeliad phytotelmata are habitats for different organisms and models for ecological studies. Although poorly known, these environments are widely distributed in tropical ecosystems, harboring cosmopolitan and endemic species. Here, we investigated the diversity of the eukaryotic community in bromeliad phytotelmata considering the influence of altitude. We randomly sampled three bromeliad individuals (twice per season over one year) at four altitudinal strata (20 m, 400 m, 910 m, and 915 m) through a mountain range in southern Brazil. Species richness of phytotelmata community was higher at intermediate altitude while community-wide multivariate analyses revealed differences in phytotelmata communities at each height. Winter was the season with highest community richness, but a peak in summer was observed. Diversity partitioning in different spatial components showed that gamma diversity decreased linearly with altitude, whereas alpha diversity peaked at intermediate altitudes, and beta diversity decreased with height. The relative importance of the components of beta diversity showed different patterns according to the altitude: turnover was more important at intermediate and lower levels, while higher altitude communities were more nested. Our results indicate that differences in height affect diversity patterns of bromeliad phytotelmata communities, which were more diverse at lower altitudes in comparison with more homogeneous communities at higher levels.

Hantaviridae: Current Classification and Future Perspectives

In recent years, negative-sense RNA virus classification and taxon nomenclature have undergone considerable transformation. In 2016, the new order Bunyavirales was established, elevating the previous genus Hantavirus to family rank, thereby creating Hantaviridae. Here we summarize affirmed taxonomic modifications of this family from 2016 to 2019. Changes involve the admission of >30 new hantavirid species and the establishment of subfamilies and novel genera based on DivErsity pArtitioning by hieRarchical Clustering (DEmARC) analysis of genomic sequencing data. We outline an objective framework that can be used in future classification schemes when more hantavirids sequences will be available. Finally, we summarize current taxonomic proposals and problems in hantavirid taxonomy that will have to be addressed shortly.

Partitioning plant spectral diversity into alpha and beta components

ABSTRACTPlant spectral diversity — how plants differentially interact with solar radiation — is an integrator of plant chemical, structural, and taxonomic diversity that can be remotely sensed. We propose to measure spectral diversity as spectral variance, which allows the partitioning of the spectral diversity of a region, called spectral gamma (γ) diversity, into additive alpha (α; within communities) and beta (β; among communities) components. Our method calculates the contributions of individual bands or spectral features to spectral γ-, β-, and α-diversity, as well as the contributions of individual plant communities to spectral diversity. We present two case studies illustrating how our approach can identify “hotspots” of spectral α-diversity within a region, and discover spectrally unique areas that contribute strongly to β-diversity. Partitioning spectral diversity and mapping its spatial components has many applications for conservation since high local diversity and distinctiveness in composition are two key criteria used to determine the ecological value of ecosystems.

Beta Diversity Partitioning and Drivers of Variations in Fish Assemblages in a Headwater Stream: Lijiang River, China

Beta diversity partitioning has currently received much attention in research of fish assemblages. However, the main drivers, especially the contribution of spatial and hydrological variables for species composition and beta diversity of fish assemblages are less well studied. To link species composition to multiple abiotic variables (i.e., local environmental variables, hydrological variables, and spatial variables), the relative roles of abiotic variables in shaping fish species composition and beta diversity (i.e., overall turnover, replacement, and nestedness) were investigated in the upstream Lijiang River. Species composition showed significant correlations with environmental, hydrological, and spatial variables, and variation partitioning revealed that the local environmental and spatial variables outperformed hydrological variables, and especially abiotic variables explained a substantial part of the variation in the fish composition (43.2%). The overall species turnover was driven mostly by replacement (87.9% and 93.7% for Sørensen and Jaccard indices, respectively) rather than nestedness. Mantel tests indicated that the overall species turnover (ßSOR and ßJAC) and replacement (ßSIM and ßJTU) were significantly related to hydrological, environmental, and spatial heterogeneity, whereas nestedness (ßSNE or ßJNE) was insignificantly correlated with abiotic variables (P > 0.05). Moreover, the pure effect of spatial variables on overall species turnover (ßSOR and ßJAC) and replacement (ßSIM and ßJTU), and the pure effect of hydrological variables on replacement (ßSIM and ßJTU), were not important (P > 0.05). Our findings demonstrated the relative importance of interactions among environmental, hydrological, and spatial variables in structuring fish assemblages in headwater streams; these fish assemblages tend to be compositionally distinct, rather than nested derivatives of one another. Our results, therefore, indicate that maintaining natural flow dynamics and habitat continuity are of vital importance for conservation of fish assemblages and diversity in headwater streams.