OBSERVATIONS ON THE BREEDING OF THE WOOLLYNECKED STORK

Scott, J. A. 1975. Observations on the breeding of the Woollynecked Stork. Ostrich 46: 201–207.

Little is known about the breeding of the Woollynecked Stork Ciconia episcopus in Africa. This paper discusses breeding, adult and nestling behaviour, nests and sites. Seasonal movements are discussed briefly. Eight nests were studied during 1970 to 1974. At one nest incubation was established at 30 to 31 days and the fledging period 55 to 65 days. No feeding of the young was observed at any time, though one eight hour observation period was undertaken. Few mating displays were seen and none away from the nest.     

白颈长尾雉与白鹇秋冬季空间生态位比较

2008年9月-2009年2月,在江西官山国家级自然保护区对白颈长尾雉(Syrmaticus ellioti)和白鹇(Lophura nycthemera)及其栖息地生态因子进行调查,通过8个资源轴分析了2个种的多维生态位宽度、重叠及种间竞争.结果表明,白鹇和白颈长尾雉综合空间生态位宽度分别仅为0.268和0.294;白鹇的海拔和坡度空间生态位大于白颈长尾雉.而白颈长尾雉的坡向生态位宽度大于白鹇,在其他资源轴上二者接近;白颈长尾雉和白鹇的栖息地生态位相似性为0.425,竞争系数为0.584,竞争比较激烈.应加强低海拔地区植被及水源的保护,减少人为干扰.     

Divergent echolocation call frequencies in insular rhinolophids (Chiroptera): a case of character displacement?

Aims Because rhinolophids have been hypothesized to use echolocation call frequency to recognize conspecifics, sympatric species calling at similar frequencies should be subject to acoustic character displacement, i.e. a drift in frequency values to minimize the risk of misidentification of conspecifics. However, it has been proposed that insufficient geographical separation between populations in sympatry and allopatry may counter the establishment of frequency differences by character displacement. Here we tested the hypothesis that insular populations should exhibit acoustic divergence, and this should be revealed by comparing call frequencies with those observed in mainland, allopatric populations of conspecifics. We also tested whether the evolutionary pressure towards acoustic divergence should be especially strong at sites where rhinolophid species emitting similar call frequencies roost together in order to minimize interspecific frequency overlap. Location Sardinia and southern Italy (Campania, Lazio, Abruzzo). Methods Time‐expanded echolocation calls and body size were recorded from Sardinian populations of Rhinolophus mehelyi Matschie, Rhinolophus hipposideros (Bechstein) and Rhinolophus euryale Blasius. Both call frequencies and forearm length of insular R. hipposideros and R. euryale were compared with those of populations from mainland areas of Italy where R. mehelyi is absent, to explore the hypothesis that the presence of the latter species (which calls at frequency values intermediate between the other two) may determine acoustic divergence in the other species. For Sardinian R. mehelyi and R. euryale, we also carried out intraspecific comparisons of call frequencies between bats from monospecific colonies and those from mixed colonies. Results As hypothesized, Sardinian R. hipposideros and R. euryale called at frequencies higher and lower, respectively, than in the peninsula. In this way, overlap with R. mehelyi is avoided. Body size showed no difference between insular and peninsular populations, i.e. frequency differences are not a by‐product of difference in body size determined by insularity. Frequency values in Sardinian R. euryale from monospecific colonies did not differ from those of bats roosting together with R. mehelyi. However, R. mehelyi showed frequency values significantly higher when associated with R. euryale, possibly to minimize the risk of species misrecognition. Main conclusions At least under geographical isolation, character displacement may be a causal mechanism for shifts in call frequency of sympatric rhinolophids. Species recognition and facilitation of intraspecific communication (with possible implications for mate recognition) constitute the best candidate factors for the phenomenon we observed.     

Resource use and co-existence: Experimental tests from a sequence of different-aged pastures

Summary Competitive relationships were estimated for plants from young and old pasture populations. Experimental treatments were conducted under both common garden field station conditions and actual grazed pasture conditions. The results suggest four conclusions. (1) Grazing and other pasture conditions did not prevent plant competition. (2) Interspecific competition appears to promote the use of different resources (niche divergence). (3) Intraspecific competition may lead to a broadening of resource use by a species and, thus, indirectly increase both niche overlap and interspecific competition. No evidence was found to support an alternative theory of co-existence in which interspecific competition is argued to promote a balancing of competitive abilities without changes to relative niche overlap. (4) Changes in resource use appears to occur within a few decades after pasture formation.     

Temperature influences on root growth for Encelia farinosa (Asteraceae), Pleuraphis rigida (Poaceae), and Agave deserti (Agavaceae) under current and doubled CO2 concentrations

To help evaluate root distribution patterns, elongation rates of individual roots were measured as a function of soil temperature for Encelia farinosa (a C₃ species), Pleuraphis rigida (C₄), and Agave deserti (CAM), sympatric codominants in the northwestern Sonoran Desert. Measurements were made at current and doubled CO₂ concentrations under winter and summer conditions of air temperature (day/night temperatures of 17 C/10 C and 33 C/22 C, respectively). The three species had different optimal temperatures for root elongation (T_opt) under winter conditions (25 C for E. farinosa, 35 C for P. rigida, and 30 C for A. deserti); T_opt increased by 2-3 C under summer conditions for all three species. The limiting temperatures for elongation also acclimated from winter to summer conditions. The rate of root elongation at T_opt was higher under summer than winter conditions for E. farinosa (9 vs. 6 mm d⁻¹) and P. rigida (20 vs. 14 mm d⁻¹), reflecting conditions for maximum photosynthesis; no difference occurred for A. deserti (9 vs. 10 mm d⁻¹). Decreased elongation rates at extreme temperatures were associated with less cell division and reduced cell extension. The doubled CO₂ concentration increased average daily root elongation rates for A. deserti under both winter (7%) and summer (12%) conditions, reflecting increased cell extension, but had no effect for the other two species. Simulations of root elongation as a function of soil temperatures showed that maximum elongation would occur at different depths (16-20 cm for E. farinosa, 4-8 cm for P. rigida, and 0-4 cm for A. deserti) and during different seasons (winter to spring for E. farinosa, spring to summer for P. rigida, and all year for A. deserti), contributing to their niche separation. Shading of the soil surface moderated daily variations in soil temperature, reducing seasonal root elongation for winter and spring and increasing elongation for summer. Shading also altered root distribution patterns, e.g., optimal rooting depth for A. deserti and especially P. rigida increased for a hot summer day.     

Effects of elevated CO2 on the interspecific competition between two sympatric species of Aphis gossypii and Bemisia tabaci fed on transgenic Bt cotton

Abstract Effects of elevated CO₂ (twice ambient vs. ambient) and Bt Cry1Ac transgene (Bt cotton cv. 33^B vs. its nontransgenic parental line cv. DP5415) on the interspecific competition between two ecologically similar species of cotton aphid Aphis gossypii and whitefly biotype‐Q Bemisia tabaci were studied in open‐top chambers. The results indicated that elevated CO₂ and Bt cotton both affected the population abundances of A. gossypii and biotype‐Q B. tabaci when introduced solely (i.e., without interspecific competition) or two species coexisted (i.e., with interspecific competition). Compared with ambient CO₂, elevated CO₂ increased the population abundances of A. gossypii and biotype‐Q B. tabaci as fed on Bt and nontransgenic cotton on 45 (i.e., seedling stage) and 60 (i.e., flowering stage) days after planting (DAP), but only significantly enhanced aphid abundance without interspecific competition on the 45‐DAP nontransgenic cotton and 60‐DAP Bt cotton, and significantly increased whitefly abundance with interspecific competition on the 45‐DAP Bt cotton and 60‐DAP nontransgenic cotton. In addition, compared with nontransgenic cotton at elevated CO₂, Bt cotton significantly reduced biotype‐Q B. tabaci abundances without and with interspecific competition during seedling and flowering stage, while only significantly decreasing A. gossypii abundances without interspecific competition during the seedling stage. When the two insect species coexisted, the proportions of biotype‐Q B. tabaci were significantly higher than those of A. gossypii on Bt and nontransgenic cotton at the same CO₂ levels, and elevated CO₂ only significantly increased the percentages of biotype‐Q B. tabaci and significantly reduced the proportions of A. gossypii on seedling and flowering nontransgenic cotton. Therefore, the effects of elevated CO₂ were favorable for biotype‐Q B. tabaci to out‐compete A. gossypii under the predicted global climate change.