Standard metabolic rate models for Carmine Shiner (Notropis percobromus) and Common Shiner (Luxilus cornutus) across different temperature regimes

Standard metabolic rates (SMR) were measured empirically for carmine shiner Notropis percobromus and common shiner Luxilus cornutus to develop SMR models that predict metabolic responses of each species under thermal conditions observed in the wild. SMR increased significantly with body mass and rising water temperature, ranging from 0.05 mg O₂ h⁻¹ at 10°C to 0.89 mg O₂ h⁻¹ at 20°C for N. percobromus weighing 0.6–2.5 g and from 0.11 mg O₂ h⁻¹ at 10°C to 0.98 mg O₂ h⁻¹ at 20°C for L. cornutus weighing 0.8–6.6 g. SMR models significantly differed between sympatric species on account of differences in model intercepts (RA) and temperature coefficients (RQ), however, the allometric relationships between mass and SMR did not significantly differ between species. Known distribution of N. percobromus and L. cornutus includes the Birch River located in Manitoba, Canada, where N. percobromus is listed as Endangered. Little is known about the physiology of N. percobromus or the species' ability to acclimate or adapt to different environmental conditions. While size differences between species contributed, in part, to differences in SMR predictions for Birch River populations, SMR trends (< 2 mg O₂ h⁻¹) for individuals weighing 1 g were similar for both species across daily temperatures. Respirometry experiments contributed to developing species-specific SMR models and inform on the effect of natural and anthropogenic stressors, namely water temperature, on the conservation of N. percobromus in this ecosystem.     

Diversity patterns from sequentially restored grasslands support the ‘environmental heterogeneity hypothesis’

The ‘environmental heterogeneity hypothesis’ (EHH) has been proposed as a mechanism that enables species coexistence through resource partitioning. In accordance with this hypothesis, plant diversity is predicted to increase with variability in resources, but there has been weak support for this hypothesis from experimental studies. The objectives of this research were to 1) characterize how resource availability and heterogeneity (coefficient of variation) change as plant communities develop using sequentially restored grasslands, 2) determine if resource heterogeneity relates to plant diversity (effective number of species, richness and evenness) and 3) reveal if the strength of resource heterogeneity–diversity relationships is different among levels of resource availability. We quantified means and coefficients of variation in soil nitrate and light availability in grasslands established on former agricultural lands for different times and their relationship to plant diversity using a geostatistically‐informed design. Nitrate availability decreased exponentially with restoration age, but no directional change in nitrate heterogeneity across the chronosequence occurred due to high resource variability in some restorations. Light availability also decreased exponentially across the chronosequence, but there was no directional change in light heterogeneity. Nitrate heterogeneity was positively correlated with both plant richness and plant effective number of species at high levels of nitrate availability. However, no nitrate heterogeneity correlation was detected at low levels of nitrate availability. Light heterogeneity was positively correlated with plant effective number of species at low levels of light availability. However, no light heterogeneity correlation was detected at high levels of light availability. Plant evenness was not correlated with resource heterogeneity at any resource availability level. These results support the positive heterogeneity–diversity relationship predicted by EHH, and uniquely that this relationship develops within a decade of plant community development, but can be obscured by resource availability.     

Exogenous and endogenous nitrogen differentially affect the decomposition of fine roots of different diameter classes of Mongolian pine in semi-arid northeast China

Plant and Soil - Nitrogen (N) addition could affect litter decomposition through its direct effects on soil N availability and indirect effects on initial litter chemistry. The aim of this study...     

Four new monorchiids from the golden trevally,Gnathanodon speciosus (Forsskål) (Perciformes: Carangidae), in Moreton Bay,Australia

Systematic Parasitology - Four new monorchiid trematodes are reported from Moreton Bay, Australia; three new species of Provitellus Dove &amp; Cribb, 1998 and one species of Ovipusillus Dove...     

A new species of Eimeria Schneider, 1885 (Apicomplexa: Eimeriidae) from the eastern gray squirrel,Sciurus carolinensis (Rodentia: Sciuridae: Sciurinae: Sciurini) from Oklahoma,USA

Systematic Parasitology - A new species of Eimeria Schneider, 1885 is described from an eastern gray squirrel (Sciurus carolinensis) from McCurtain County, Oklahoma, USA. Oöcysts of Eimeria...