Seasonal and spatial hydrological variability drives aquatic biodiversity in a flood‐pulsed,sub‐tropical wetland

1. Flood‐pulsed wetlands make vital contributions to local and global biodiversity. However, the patterns and controls of spatial and temporal variation in aquatic biodiversity in flood‐pulsed wetlands are not well understood. We analysed the relationship between variation in hydrological regime and the patterns of aquatic biodiversity in a large pristine flood‐pulsed wetland, the Okavango Delta, Botswana. 2. Surveys of water chemistry, diatoms and macroinvertebrates were conducted over the seasonal phases of the flood pulse. Hydrological variables of flood frequency and hydroperiod class were collated from 16 years of satellite images. Multivariate regression trees and generalised least squares regression were used to determine the chief controls of community composition and taxon richness. 3. Hydroperiod class, phase of the flood and conductivity explained 32% and 43% of the variation in diatom and invertebrate taxon richness, respectively. There was a negative relationship between hydroperiod class and invertebrate taxon richness on the rising, peak and receding flood, whereas at low flood there was no significant relationship. Multivariate regression tree analysis revealed hydroperiod class, phase of the flood and conductivity as the dominant forces shaping invertebrate and diatom community composition. 4. Seasonal and spatial variation in hydrological conditions are the principal drivers of variation in aquatic biodiversity in flood‐pulsed wetlands. In pristine flood‐pulsed wetlands, increased productivity caused by the arrival of the flood waters appears to override disturbance and connectivity in shaping taxon richness and community composition. Thus, these data suggest that the maintenance of a rich mosaic of habitats covering a broad range of hydroperiod is the key to preserving aquatic biodiversity and natural ecosystem function in flood‐pulsed wetlands.     

Ortholinea alata n. sp. (Myxosporea: Ortholineidae) in the Northern Butterfly Fish Chaetodon rainfordi

Ortholinea alata n. sp. is described from the northern butterfly fish, Chaetodon rainfordi collected at Heron Island, Great Barrier Reef, Australia. Spherical, disporous trophozoites (10–15 μ) and spores were observed in the lumina of kidney tubules and collecting ducts. Spores are broadly triangular with two short, broad processes that extend dorsoventrad from the posterior end of each of the two spore valves. Valves are bisected by a suture in the plane of the polar capsules. Spores are 12.6 μ (length) × 9.6 μ (width) × 9.9 μ (length), and at the anterior end contain two spherical, divergent polar capsules measuring 4.6 ( 4.1 –5.1) μ. Sporogenesis is similar to that of renal Sphaerospora spp.: the intraluminal trophozoites of O. alata n. sp. correspond to pseudoplasmodia described for Sphaerospora spp. and no large, multinucleate plasmodia are formed. No significant histopathological changes were observed in the kidneys of infected fish.     

Habitat Use of Sympatric Rattlesnake Species Within the Gulf Coastal Plain

Abstract: The eastern diamondback rattlesnake (Crotalus adamanteus) and timber rattlesnake (Crotalus horridus) are sympatric throughout most of southern Georgia, USA. We used rattlesnake sightings to quantify and compare habitat use by these 2 species in the Gulf Coastal Plain. At the largest scale examined, univariate statistics and logistic regression models indicated that eastern diamondback rattlesnakes were associated with roads but not with any of the specific habitat types we examined. In contrast, timber rattlesnakes were closely associated with hardwood habitat and riverine systems but not with roads and edges. To effectively conserve and manage both species in the Southeast, a habitat matrix of large intact patches of both hardwood and pine (Pinus spp.) forest may be necessary.     

Relationship between fire,climate oscillations,and drought in British Columbia,Canada, 1920–2000

Climate oscillations such as El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) are known to affect temperature and precipitation regimes and fire in different regions of the world. Understanding the relationships between climate oscillations, drought, and area burned in the past is required for anticipating potential impacts of regional climate change and for effective wildfire‐hazard management. These relationships have been investigated for British Columbia (BC), Canada, either as part of national studies with coarse spatial resolution or for single ecosystems. Because of BC's complex terrain and strong climatic gradients, an investigation with higher spatial resolution may allow for a spatially complete but differentiated picture. In this study, we analyzed the annual proportion burned–climate oscillation–drought relationships for the province's 16 Biogeoclimatic Ecosystem Classification (BEC) zones. Analyses are based on a digital, spatially explicit fire database, climate oscillation indices, and monthly precipitation and temperature data with a spatial resolution of 400 m for the period 1920–2000. Results show that (1) fire variability is better related to summer drought than to climate oscillations, and that (2) fire variability is most strongly related to both, climate oscillations and summer drought in southeastern BC. The relationship of area burned and summer drought is strong for lower elevations in western BC as well. The influence of climate oscillations on drought is strongest and most extensive in winter and spring, with higher indices being related to drier conditions. Winter and spring PDO and additive winter and spring PDO+ENSO indices show BC's most extensive significant relationship to fire variability. Western BC is too wet to show a moisture deficit in summer that would increase annual area burned due to teleconnections.     

Diet specificity is not associated with increased reproductive performance of Golden Eagles Aquila chrysaetos in Western Scotland

Amongst raptor species, individuals with specialized diets are commonly observed to have higher reproductive output than those with general diets. A suggested cause is that foraging efficiency benefits accrue to diet specialists. This diet specificity hypothesis thus predicts that diet breadth and reproductive success should be inversely related within species. We highlight, however, that a prey availability hypothesis also makes the same prediction in some circumstances. Hence, when high diet specificity results from high encounter rates with an abundant, preferred prey, then prey availability may affect reproductive success, with diet specialization as an incidental correlate. Using three insular study areas in western Scotland, we examine diet specificity and reproductive success in Golden Eagles Aquila chrysaetos. Diet breadth and breeding productivity were not negatively related in any of our study areas, even though birds with specific diets did tend to have a higher incidence of preferred prey (grouse and lagomorphs) in the diet. Indeed, in two study areas there was evidence that diet generalists had higher breeding productivity. Our results therefore failed to support the diet specificity hypothesis but were consistent with the prey availability hypothesis. We highlight that although many other studies are superficially consistent with the diet specificity hypothesis, our study is not alone in failing to provide support and that the hypothesis does not provide a generic explanation for all relevant results. Diet specificity in predators can be at least partially a response to prey diversity, availability and distribution, and benefits associated with different prey types, so that being a generalist is not necessarily intrinsically disadvantageous. We suggest that the available evidence is more consistent with variation in prey abundance and availability as a more influential factor explaining spatial and temporal variation in breeding productivity of ‘generalist’ species such as the Golden Eagle. Under this argument, prey abundance and availability are the main drivers of variation in reproductive output. Diet specificity is a consequence of variation in prey availability, rather than a substantial cause of variation in reproductive success.     

Value of long‐term ecological studies

Long‐term ecological studies are critical for providing key insights in ecology, environmental change, natural resource management and biodiversity conservation. In this paper, we briefly discuss five key values of such studies. These are: (1) quantifying ecological responses to drivers of ecosystem change; (2) understanding complex ecosystem processes that occur over prolonged periods; (3) providing core ecological data that may be used to develop theoretical ecological models and to parameterize and validate simulation models; (4) acting as platforms for collaborative studies, thus promoting multidisciplinary research; and (5) providing data and understanding at scales relevant to management, and hence critically supporting evidence‐based policy, decision making and the management of ecosystems. We suggest that the ecological research community needs to put higher priority on communicating the benefits of long‐term ecological studies to resource managers, policy makers and the general public. Long‐term research will be especially important for tackling large‐scale emerging problems confronting humanity such as resource management for a rapidly increasing human population, mass species extinction, and climate change detection, mitigation and adaptation. While some ecologically relevant, long‐term data sets are now becoming more generally available, these are exceptions. This deficiency occurs because ecological studies can be difficult to maintain for long periods as they exceed the length of government administrations and funding cycles. We argue that the ecological research community will need to coordinate ongoing efforts in an open and collaborative way, to ensure that discoverable long‐term ecological studies do not become a long‐term deficiency. It is important to maintain publishing outlets for empirical field‐based ecology, while simultaneously developing new systems of recognition that reward ecologists for the use and collaborative sharing of their long‐term data sets. Funding schemes must be re‐crafted to emphasize collaborative partnerships between field‐based ecologists, theoreticians and modellers, and to provide financial support that is committed over commensurate time frames.     

REPRODUCTION BY NORTHERN BOBWHITES IN WESTERN OKLAHOMA

Abstract: We studied northern bobwhites (Colinus virginianus) in western Oklahoma, USA, during the nesting seasons of 1992–2001. We obtained latitude-specific information on nesting biology and tested hypotheses on the cause of declines in clutch size with progression of the nesting season and on the phenological relation of first, second, and third nesting attempts. For pooled data on bobwhites alive during 15 April-15 September, 64 ± 6.5% of juvenile females (n = 56), 90 ± 10.0% of adult females (n = 9), 13 ± 4.1% of juveniles males (n = 68), and 41 ± 10.7% of adult males (n = 22) incubated ≥ 1 nest. Bobwhites that entered the reproduction period starting on 15 April (n = 229) accumulated 203 nesting attempts (male and female incubations), which translated to 1.7 attempts/hen for all hens that entered (n = 117) and 3.1 attempts/hen for hens that survived to 15 September (n = 65). Overall success for incubated nests (48 ± 2.8%, n = 331) was independent of sex-age class and nesting attempt (1, 2, 3), but it declined at a rate of 2.37%/year (95% CL = 1.10–3.64%/year) during the study. Clutch size declined by 1 egg for every 14–20 elapsed days in the nesting season and the rate of decline was independent of incubation attempt (1 or 2); this result suggests that lower clutch sizes later in the nest season were not necessarily a function of re-nesting. Ending of nest-incubation attempts (1, 2, 3) occurred within an 8-day period from 26 August-2 September. Our results implied that early-season nesting cover is a management concern and that high nest success is possible in the absence of nest predator suppression where abundant nest sites occur across the landscape.