Pool Margins Research Articles

Unsuccessful Breeding by Desert Toads (Bufo Punctatus) at the Limit of Their Ecological Tolerance

Survival and reproduction of a linear population of Bufo punctatus was studied during 1964 in an often waterless, mile—long section of a canyon of the Colorado Desert of California. Reproduction had been unsuccessful in earlier years of record because of little or no springflow and infrequency of summer flashfloods. In 1964, springflow began on March 23 and retreated rapidly in early May. There was one summer flashflood. Toads did not emerge from underground winter retreats until evening air temperature was around 18°C and did not breed until the weather was some 6 degrees warmer. The relatively few females who oviposited, mainly during April 9 to 6, produced and estimated 34,000 eggs. The lowest downcanyon site of oviposition in the spring was 5,370 ft above the lowest downcanyon site in 1962. Home range up and down the canyon during the breeding season was about 600 ft at the most for males and 1,500 ft more for females. Some trilling males went underground when the stream dried at their sites; others migrated upcreek as much as 2,000 ft to new trilling sites beside water. Many females did not migrate, while others showed a tendency to wander great distances (2,700 ft maximum record) towards or away from water. When the stream dried completely all toads disappeared but emerged after the one flashflood of summer in order to hydrate. Tracks then occurred 1,300 ft farther downcreek than any individual had been seen in spring. Very limited breeding was accomplished by individuals who were different from the spring breeders. Rate of larval development in spring (approximately 2 months to metamorphosis) was retarded by coolness of the water. There were four different stages of larval behavior: 1) egg—site aggregations, when tadpoles massed at sites of oviposition; 2) deepwater aggregations, when the mass moved to deepest available water; 3) feeding dispersal when tadpoles dispersed in search of food; and 4) thermal aggregations, when they congregated in warmest water at margins of pools by day and at bottoms by night. Nearly all tadpoles were killed by desiccation both in spring and summer. Since some toe—marked adults were captured after 4 years, longevity may be a reason for survival of populations in severe habitats where successful reproduction is rare.

On the Chemical Composition of Some Waters from the Moor House Nature Reserve

The analysis of bog waters has a two-fold value. Firstly, it is of some intrinsic interest to elucidate the chemical composition of waters isolated from the mineral soil by organic deposits, and deriving their entire mineral supply from atmospheric precipitation. Secondly, the poverty of raised and blanket bogs in mineral nutrients is undoubtedly an important factor in determining their floras; and vegetation patterns can often be associated in a general way with water composition. This paper records the amounts of eleven constituents in various natural waters from the new Pennine Nature Reserve at Moor House - chiefly from pools on the blanket peats at Bog Hill, now under intensive investigation by the Nature Conservancy. DESCRIPTION OF THE AREA Moor House lies at an altitude of about 1800 ft. (550 m.) in the northern Pennine uplands, with a rainfall of about 64 in. (162 cm.), an average annual temperature of 44? F. (6.7? C.) and an average relative humidity of 86 per cent (all data for 1953 only). It is surrounded by moorland and blanket bog vegetation, on peat overlying drift or carboniferous rock with limestone bands. Burning and grazing have affected the plant communities, which in general resemble those described by Pearsall (1941) from the Stainmore district a little to the south. Among the least disturbed areas is Bog Hill, a slight elevation blanketed by deep peat and bearing a community dominated by Sphagnum acutifolium (agg., including rubellum and nemoreum), Calluna vulgaris and Eriophorum vaginatum, with Trichophorum caespitosum locally abundant. The Sphagnum cover is fairly continuous, with several small pools dotted about its surface. These most frequently contain Sphagnum cuspidatum and Eriophorum angustifolium, with the alga Chlorobotrys sometimes forming a scum at the bottom. In certain pools Drepanocladus fluitans is quite plentiful, in others the liverwort Gymnocolea inflata. Sphagnum papillosum is often abundant at the pool margins. METHODS Water samples were obtained on two occasions in 1954, following a dry spell (May 18th) and during wet weather (August 2nd). The bog pools sampled ranged in size from about 1 to 15 ft. (0.3 m. to 4.5 m.) across, and up to about 18 in. (46 cm.) deep. Collections were made and stored in polythene bottles, the waters being filtered through Whatman 541 papers (washed with three volumes of distilled water and one volume of sample) within a day or two of collection. pH was determined by glass electrode, and specific conductivity by a bright platinum cell and Mullard bridge. Calcium and magnesium were estimated by versenate titration with ammonium purpurate and eriochrome black T as indicators; samples coloured by humus were evaporated to dryness with a few drops of hydrogen peroxide and taken up in dilute hydrochloric acid. Sodium and potassium were measured by EEL flame photometer,

Invalidation of the Genus Vaughaniella

AN examination of specimens of an alga at first assigned to Vaughaniella rupicola Boergs. has led to the conclusion that the genus Vaughaniella Boergs.1 represents the basal rhizomatous portion of the genus Padina Adans. In southern Queensland, these flattened rhizomes, often showing transition to fan-shaped thalli, are found at the base of plants of Padina commersonii Bory in both estuarine and exposed localities; but around the margins of shallow lower littoral pools, on exposed rock platforms, rhizome development may sometimes take place without any production of fan thalli.