The spider family Dysderidae in the Balearic Islands.

The spider family Dysderidae in the Balearic Islands counts 6 species, which have all been revised. Dysdera arnedoi Lissner n. sp. and Parachtes riberai Bosmans n. sp. are newly described species from Majorca, where they seem to be confined. A neotype is designated for Dysdera balearica Thorell, 1873 and D. mordax L. Koch, 1882 is considered a junior synonym of the former. Dysdera lata Reuss, 1834 is cited for the first time in Majorca. Dysdera crocata C. L. Koch, 1838 and Harpactea dufouri (Thorell, 1873) occur on all the main Balearic Islands. Harpactea corticalis (Simon, 1882) and H. hombergi (Scopoli, 1763) were misidentified in the past and are deleted from the Balearic Islands list.

Nutrient and growth responses of cattail (Typha domingensis) to redox intensity and phosphate availability.

BACKGROUND AND AIMS: In the Florida Everglades, the expansion of cattail (Typha domingensis) into areas once dominated by sawgrass (Cladium jamaicense) has been attributed to altered hydrology and phosphorus (P) enrichment. The objective of this study was to quantify the interactive effects of P availability and soil redox potential (Eh) on the growth and nutrient responses of Typha, which may help to explain its expansion. METHODS: The study examined the growth and nutrient responses of Typha to the interactive effects of P availability (10, 80 and 500 microg P L(-1)) and Eh level (-150, +150 and +600 mV). Plants were grown hydroponically in a factorial experiment using titanium (Ti(3+)) citrate as a redox buffer. KEY RESULTS: Relative growth rate, elongation, root-supported tissue/root ratio, leaf length, lateral root length and biomass, as well as tissue nutrient concentrations, were all adversely affected by low Eh conditions. P availability compensated for the negative effect of low Eh for all these variables except that low P stimulated root length and nutrient use efficiency. The most growth-promoting treatment combination was 500 microg P L(-1)/ + 600 mV. CONCLUSIONS: These results, plus previous data on Cladium responses to P/Eh combinations, document that high P availability and low Eh should benefit Typha more than Cladium as the growth and tissue nutrients of the former species responded more to excess P, even under highly reduced conditions. Therefore, the interactive effects of P enrichment and Eh appear to be linked to the expansion of Typha in the Everglades Water Conservation Area 2A, where both low Eh and enhanced phosphate availability have co-occurred during recent decades.

Interactive effects of redox intensity and phosphate availability on growth and nutrient relations of Cladium jamaicense (Cyperaceae).

Expansion of Typha domingensis into areas previously dominated by Cladium jamaicense in the Florida Everglades has been linked to anthropogenic phosphorus (P) enrichment and increased hydroperiod. The principal stress factor for plants in flooded soils is biochemical reduction, the intensity of which is measured as redox potential (Eh). The objective of this study was to assess the growth response of C. jamaicense to Eh (-150, +150, and +600 mV) and P availability (10, 80, and 500 µg P/L). Plants were grown hydroponically in a factorial experiment using titanium (Ti(3+)) citrate as an Eh buffer. Treatment effects on growth, biomass partitioning, and tissue nutrients were recorded. Growth approximately doubled in response to a 50-fold increase in P availability. Low redox significantly reduced growth and tissue P concentration. While plant P concentrations increased 20-fold between the 10 and 500 µg P/L treatments, P concentrations were 50-100% higher at +600 mV than at -150 mV within each phosphate level. At high Eh, C. jamaicense appears well adapted to low nutrient environments because of its low P requirement and high retention of acquired P. However, at low Eh the ability to acquire or conserve acquired P decreases and as a consequence, higher phosphate levels are required to sustain growth. Findings of this study indicate that young C. jamaicense exhibits low tolerance to strongly reducing conditions when phosphate is scarce.