Water‑soluble phosphorus in submerged macrophytes reflects interspecific differences and environmental responses

The shoot apical meristem (SAM) is the key organizing element in the plant body and is responsible for the core of plant body organization and shape. Surprisingly, there are almost no comparative data that would show links between parameters of the SAM and whole-plant traits as drivers of the plant's response to the environment. Interspecific differences in SAM anatomy were examined in 104 perennial herbaceous angiosperms. There were differences in SAM parameters among individual species, their phylogenetic patterns, and how their variation is linked to variation in plant above-ground organs and hence species' environmental niches. SAM parameters were correlated with the size-related traits of leaf area, seed mass and stem diameter. Of the two key SAM parameters (cell size and number), variation in all organ traits was linked more strongly to cell number, with cell size being important only for seed mass. Some of these correlations were due to shared phylogenetic history (e.g. SAM diameter versus stem diameter), whereas others were due to parallel evolution (e.g. SAM cell size and seed mass). These findings show that SAM parameters provide a functional link among sizes and numbers of plant organs, constituting species' environmental responses.

Here we focused on the co-occurrence pattern on regional and local scales, and on the niche differences of two species of congeneric beetles (Ochthebius quadricollis and O. lejolisii, Hydraenidae) exclusive of supratidal rockpools. Abundances of adults and larval stages from both species and environmental variables were obtained in 10 pools from 12 localities along the Iberian Mediterranean coast. To determine the local co-existence pattern, we monthly sampled two localities in an annual cycle. On regional and local scales, we found negative correlations between both species’ pool abundances, which suggest spatio-temporal segregation based on their different environmental responses. The OMI analysis detected interspecific niche differences, larger in larvae than adults. The best regression models obtained for O. quadricollis larvae included depth, conductivity, and fine sediments as the main explanatory variables with a positive effect, and distance to sea and CPOM with a negative effect. For O. lejolisii larvae, the best models included CPOM and periphyton with positive effects, while pool area, depth and conductivity negatively affected. Our results suggest that subtle interspecific differences in ecological niches, mainly those related to pool hydroperiod and salinity, could determine spatio-temporal storage effects as the principal mechanisms of co-existence on local and regional scales.

Viscous threads that form the prey capture spiral of araneoid orb-webs retain insects that strike the web, giving a spider more time to locate and subdue them. The viscoelastic glycoprotein glue responsible for this adhesion forms the core of regularly spaced aqueous droplets, which are supported by protein axial fibers. Glycoprotein extensibility both facilitates the recruitment of adhesion from multiple droplets and dissipates the energy generated by insects struggling to free themselves from the web. Compounds in the aqueous material make the droplets hygroscopic, causing an increase in both droplet volume and extensibility as humidity (RH) rises. We characterized these humidity-mediated responses at 20%, 37%, 55%, 72% and 90% RH in two large orb-weavers, Argiope aurantia, which is found in exposed habitats, and Neoscona crucifera, which occupies forests and forest edges. The volume-specific extension of A. aurantia glycoprotein reached a maximum value at 55% RH and then declined, whereas that of N. crucifera increased exponentially through the RH range. As RH increased, the relative stress on droplet filaments at maximum extension, as gauged by axial line deflection, decreased in a linear fashion in A. aurantia, but in N. crucifer increased logarithmically, indicating that N. crucifera threads are better equipped to dissipate energy through droplet elongation. The greater hygroscopicity of A. aurantia threads equips them to function in lower RH environments and during the afternoon when RH drops, but their performance is diminished during the high RH of the morning hours. In contrast, the lower hygroscopicity of N. crucifera threads optimizes their performance for intermediate and high RH environments and during the night and morning. These interspecific differences support the hypothesis that viscous capture threads are adapted to the humidity regime of an orb-weaver's habitat.

Trait-based ecology strives to better understand how species, through their bio-ecological traits, respond to environmental changes, and influence ecosystem functioning. Identifying which traits are most responsive to environmental changes can provide insight for understanding community structuring and developing sustainable management practices. However, misinterpretations are possible, because standard statistical methods (e.g., principal component analysis and linear regression) for identifying and ranking the responses of different traits to environmental changes ignore interspecific differences. Here, using both artificial data and real-world examples from marine fish communities, we show how considering species-specific responses can lead to drastically different results than standard community-level methods. By demonstrating the potential impacts of interspecific differences on trait dynamics, we illuminate a major, yet rarely discussed issue, highlighting how analytical misinterpretations can confound our basic understanding of trait responses, which could have important consequences for biodiversity conservation.