Reproductive seasonality in the tropical butterfly Hypolimnas bolina (Lepidoptera: Nymphalidae) in northern Australia

2001 ◽  
Vol 17 (4) ◽  
pp. 483-494 ◽  
Author(s):  
DARRELL J. KEMP
Keyword(s):  
Reproductive Activity ◽  
Dry Season ◽  
Northern Australia ◽  
Breeding Phenology ◽  
Reproductive Seasonality ◽  
Leaf Quality ◽  
Tropical Environments ◽  
Dry Tropics ◽  
Nymphalid Butterfly ◽  
The Tropics

Because seasonality in tropical environments is driven by variation in rainfall, phytophagous tropical organisms are expected to exhibit mechanisms of escape in space and time that allow them to synchronize their breeding efforts with suitably wet periods of the year. This hypothesis was addressed by studying the breeding phenology of the nymphalid butterfly Hypolimnas bolina (L.) in the Australian wet-dry tropics. This species favours small, herbaceous larval foodplants that either die off annually or exhibit marked declines in leaf quality during the dry season. As expected, reproductive activity in H. bolina was broadly correlated with both rainfall and humidity, with individuals spending part of the dry season (early April to late August) sheltering in overwintering sites in a state of reproductive diapause. The timing of the overwintering period was similar between the 2 years, which suggests that individuals respond to seasonally predictable cues such as photoperiod. At least in 1998, the exit of butterflies from overwintering sites was relatively sudden and coincided with the first spring rainfall event. These findings suggest that H. bolina copes with seasonal adversity in the tropics by means of a regularly timed diapause.

The influence of weather on the quality of tropical legume pasture during the dry season in northern Australia. III. Effects of digestibility and chemical composition

1989 ◽  
Vol 40 (3) ◽  
pp. 573 ◽  
Author(s):  
RL McCown ◽  
BH Wall
Keyword(s):  
Dry Matter ◽  
Mediterranean Climate ◽  
Dry Season ◽  
In Vitro Digestibility ◽  
Northern Australia ◽  
Pasture Legumes ◽  
Dry Matter Digestibility ◽  
Dry Tropics

In the semi-arid tropics, accumulated shed leaf of certain pasture legumes can provide highly nutritious feed for cattle in the dry season. Previous papers in this series have dealt with the fungal spoilage of leaf of Caribbean stylo in response to dew and unseasonal rainfall and the threat to acceptability by cattle. This paper focuses on the effects of varying degrees of moulding and leaching on dry matter digestibility of leaf of this legume. Uniform leaf material of high digestibility was exposed at six locations during the dry season and samples retrieved at 4-weekly intervals. From initial values of 75%. in vitro digestibility dropped to as low as 50%. Degree of moulding, as indicated by a quantitative index of discoloration, accounted for about 80�/o of loss. Moulding was much more important than leaching. This latter finding in the winter-dry tropics contrasts with previous findings in the summer-dry Mediterranean climate.

The influence of weather on the quality of tropical legume pasture during the dry season in Northern Australia. II. Moulding of standing hay in relation to rain and dew

1981 ◽  
Vol 32 (4) ◽  
pp. 589 ◽  
Author(s):  
RL McCown ◽  
BH Wall
Keyword(s):  
Relative Humidity ◽  
Leaf Litter ◽  
Bulk Sample ◽  
Dry Season ◽  
Northern Australia ◽  
Mould Growth ◽  
Tropical Legume ◽  
Dry Tropics

Naturally desiccated legume pasture is valuable forage in the dry season but is very vulnerable to moulding, which drastically reduces its acceptability to cattle. At a network of sites in the wet-dry tropics of Australia, trends in mouldiness of standard leaf 'litter' samples were monitored in relation to rain, dew, and rates of drying. Although heavy dews occurred frequently at some sites, only the immediate top layer of fallen leaf moulded. This had a very small effect on the mouldiness of the bulk sample. Appreciable moulding occurred only after at least 2 mm rain, but in some cases there was no mould growth after over 10 mm rain; the amount of rain accounted for only 23 % of the variation in mouldiness. The duration of wetness of the leaf litter, as indicated by the duration of 95 % relative humidity 10 cm above the ground after rain, accounted for 91 % of the variation in mouldiness. At the more humid sites, material which was exposed for several weeks before rain moulded more rapidly after rain than did recently exposed material, even though at the time of rain there were no visible differences. Differences in causation of moulding of conventional hay and of 'standing hay' are discussed.

scholarly journals Dry season aerosol iron solubility in tropical northern Australia

2016 ◽  
Vol 16 (19) ◽  
pp. 12829-12848 ◽  
Author(s):  
V. Holly L. Winton ◽  
Ross Edwards ◽  
Andrew R. Bowie ◽  
Melita Keywood ◽  
Alistair G. Williams ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Biomass Burning ◽  
Algal Blooms ◽  
Atmospheric Transport ◽  
Dry Season ◽  
Global Ocean ◽  
Future Research ◽  
Northern Australia ◽  
Tropical Waters ◽  
The Tropics

Abstract. Marine nitrogen fixation is co-limited by the supply of iron (Fe) and phosphorus in large regions of the global ocean. The deposition of soluble aerosol Fe can initiate nitrogen fixation and trigger toxic algal blooms in nitrate-poor tropical waters. We present dry season soluble Fe data from the Savannah Fires in the Early Dry Season (SAFIRED) campaign in northern Australia that reflects coincident dust and biomass burning sources of soluble aerosol Fe. The mean soluble and total aerosol Fe concentrations were 40 and 500 ng m−3 respectively. Our results show that while biomass burning species may not be a direct source of soluble Fe, biomass burning may substantially enhance the solubility of mineral dust. We observed fractional Fe solubility up to 12 % in mixed aerosols. Thus, Fe in dust may be more soluble in the tropics compared to higher latitudes due to higher concentrations of biomass-burning-derived reactive organic species in the atmosphere. In addition, biomass-burning-derived particles can act as a surface for aerosol Fe to bind during atmospheric transport and subsequently be released to the ocean upon deposition. As the aerosol loading is dominated by biomass burning emissions over the tropical waters in the dry season, additions of biomass-burning-derived soluble Fe could have harmful consequences for initiating nitrogen-fixing toxic algal blooms. Future research is required to quantify biomass-burning-derived particle sources of soluble Fe over tropical waters.

Limited impact of irrigation on the phenology of Brachychiton megaphyllus: a deciduous shrub that flowers while leafless during the tropical dry season

2015 ◽  
Vol 31 (5) ◽  
pp. 459-467 ◽  
Author(s):  
Patricia J. Bate ◽  
Donald C. Franklin
Keyword(s):  
Soil Moisture ◽  
Reproductive Activity ◽  
Dry Season ◽  
Reproductive Phenology ◽  
Wet Season ◽  
Canopy Development ◽  
Seasonally Dry ◽  
Dry Tropics ◽  
Tap Root ◽  
Leaf Flush

Abstract:A suite of woody plants inhabiting the seasonally dry tropics flower while leafless during the dry season, raising intriguing questions about the role of moisture limitation in shaping their phenology. Brachychiton megaphyllus is one such species, a shrub of open forests and savannas in northern Australia. We documented leaf and reproductive phenology of 14 shrubs, and irrigated a further 15, to determine if soil moisture affected leafiness and reproductive activity. Brachychiton megaphyllus showed first flower buds shortly after the cessation of wet-season rains, and budded and flowered throughout the dry season. In some plants, leaf flush occurred prior to the first rains. Rates of fruit set and maturity were very low. Irrigation did not significantly influence leaf shoot or subsequent canopy development. Contrary to expectation, irrigation decreased the production of buds and flowers though it had no impact on the production of fruit, a response for which we suggest a number of hypotheses. Phenological responses to irrigation may have been limited because B. megaphyllus responds primarily to cues other than soil moisture and is buffered against seasonal drought by a large tap root. This suggests mechanisms by which flowering while leafless may occur in a range of species.

Resource partitioning among five sympatric species of freshwater turtles from the wet–dry tropics of northern Australia

2017 ◽  
Vol 44 (3) ◽  
pp. 219 ◽  
Author(s):  
Michael A. Welsh ◽  
J. Sean Doody ◽  
Arthur Georges
Keyword(s):  
Resource Partitioning ◽  
Niche Overlap ◽  
Sympatric Species ◽  
Dry Season ◽  
Gut Contents ◽  
Microhabitat Use ◽  
Freshwater Turtles ◽  
Northern Australia ◽  
Dietary Shift ◽  
Dry Tropics

Context Resource partitioning of diet and microhabitat was examined for five sympatric species of freshwater turtles in the Daly River in the northern end of Northern Territory (Top End) in Australia. The Daly River supports a high diversity of freshwater turtles, making it the ideal place to study a freshwater turtle community. Aims To determine the dry-season diet and microhabitat use of Carettochelys insculpta, Elseya dentata, Chelodina oblonga, Emydura victoriae and Emydura subglobosa worrelli and examine intraspecific and interspecific niche overlap and ontogenetic dietary shift. Methods Gut contents were collected by stomach flushing, and microhabitat use was determined by recording where each turtle was first seen before capture. Diet and microhabitat use were compared using an index of relative importance. Niche overlap was measured with Horn’s overlap index. Key results Carettochelys insculpta is an opportunistic omnivore that feeds mostly on ribbonweed (Vallisneria spiralis) and aquatic snails. Elseya dentata is herbivorous, feeding primarily on aquatic algae. The diets of C. insculpta and E. dentata overlapped moderately, but the overall niche overlap was low because they occupied different microhabitats within the river. Chelodina oblonga fed very little, and may use the Daly River as a dry-season refuge. Emydura victoriae is molluscivorous, consuming more molluscs as it grows. This ontogenetic dietary shift was associated with megacephaly (extreme broadly expanded head that is too large to fit into the carapace) and expanded triturating surfaces. This specialisation allows adult E. victoriae to feed exclusively on molluscs and so their diet overlapped little with other species. Emydura subglobosa worrelli was omnivorous, consuming mostly freshwater sponge and apparently preferring more lentic water. Conclusions The freshwater turtles of the wet–dry tropics are usually reported as being heavily reliant on the seeds, fruits and leaves of riparian vegetation; however, the present study showed that the dry-season diet in perennial rivers is primarily of aquatic origin. Implications The study suggested that populations of C. insculpta, E. dentata and E. victoriae could be threatened by broad-scale development in northern Australia if there were substantive impacts on aquatic macrophytes and molluscs in the Daly River system.

Comparative Uranium-Thorium and Thermoluminescence Dating of Weathered Quaternary Alluvium in the Tropics of Northern Australia

1991 ◽  
Vol 35 (3-Part1) ◽  
pp. 347-366 ◽  
Author(s):  
Gerald C. Nanson ◽  
David M. Price ◽  
Stephen A. Short ◽  
Robert W. Young ◽  
Brian G. Jones
Keyword(s):  
Climatic Conditions ◽  
Northern Australia ◽  
Medium Sand ◽  
Secondary Minerals ◽  
Dry Tropics ◽  
Thermoluminescence Dating ◽  
Fan Delta ◽  
Sand Body ◽  
The Tropics ◽  
Age Determinations

AbstractThermoluminescence (TL) age determinations of alluvial sediments in the tropics are evaluated by comparison with U/Th age determinations of pedogenic accumulations in the alluvium of the lower Gilbert River, a large fan delta in the wet-dry tropics of northern Queensland, Australia. This study extends U/Th dating by applying it not only to calcretes, but also to Fe/Mn oxyhydroxide/oxide accumulations. While a direct correlation cannot be made between U/Th dates from secondary minerals and TL dates from the host sediments, both sets of data show broad consistency. In addition to providing a minima for acceptable TL ages, U/Th dates are useful for determining the chronology of pedogenesis/diagenesis. They show that calcretes and ferricretes have formed under similar climatic conditions in the wet-dry tropics of northern Australia during the late pleistocene. Beneath about 5–12 m the Gilbert fan delta consists of an extensive sand body older than 85,000 yr and probably about 120,000 yr in age, representative of a period of major fluvial activity not repeated since this time. Above are muds and fine sandy muds that extend uninterrupted to the present surface except in the downstream fan where they are bisected by a thin unit of medium sand that TL dates at 40,000–50,000 yr B.P. A system of sandy distributary channels over the fan surface represents an early Holocene fluvial phase probably more active than at present.

The use of regional and alluvial groundwater by riparian trees in the wet‐dry tropics of northern Australia.

2021 ◽  
Author(s):  
Caroline A. Canham ◽  
Clément Duvert ◽  
Leah S. Beesley ◽  
Michael M. Douglas ◽  
Samantha A. Setterfield ◽  
...  
Keyword(s):  
Northern Australia ◽  
Dry Tropics ◽  
Riparian Trees ◽  
Alluvial Groundwater

scholarly journals Seasonal changes in water quality and macrophytes and the impact of cattle on tropical floodplain waterholes

2012 ◽  
Vol 63 (9) ◽  
pp. 788 ◽  
Author(s):  
N. E. Pettit ◽  
T. D. Jardine ◽  
S. K. Hamilton ◽  
V. Sinnamon ◽  
D. Valdez ◽  
...  
Keyword(s):  
Water Quality ◽  
Seasonal Changes ◽  
Aquatic Macrophyte ◽  
Plant Cover ◽  
Critical Role ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Dry Tropics ◽  
The Impact

The present study indicates the critical role of hydrologic connectivity in floodplain waterholes in the wet–dry tropics of northern Australia. These waterbodies provide dry-season refugia for plants and animals, are a hotspot of productivity, and are a critical part in the subsistence economy of many remote Aboriginal communities. We examined seasonal changes in water quality and aquatic plant cover of floodplain waterholes, and related changes to variation of waterhole depth and visitation by livestock. The waterholes showed declining water quality through the dry season, which was exacerbated by more frequent cattle usage as conditions became progressively drier, which also increased turbidity and nutrient concentrations. Aquatic macrophyte biomass was highest in the early dry season, and declined as the dry season progressed. Remaining macrophytes were flushed out by the first wet-season flows, although they quickly re-establish later during the wet season. Waterholes of greater depth were more resistant to the effects of cattle disturbance, and seasonal flushing of the waterholes with wet-season flooding homogenised the water quality and increased plant cover of previously disparate waterholes. Therefore, maintaining high levels of connectivity between the river and its floodplain is vital for the persistence of these waterholes.

Irrigation and crop improvement in temperate and tropical environments

1986 ◽  
Vol 316 (1537) ◽  
pp. 319-330 ◽  
Keyword(s):  
Life Cycle ◽  
Low Temperatures ◽  
Energy Use ◽  
Crop Improvement ◽  
Yield Potential ◽  
Multiple Cropping ◽  
Tropical Environments ◽  
Physiological Processes ◽  
Seasonal Signals ◽  
The Tropics

There is a strong interaction between irrigation and crop improvement, irrigation creating new opportunities and challenges for plant breeders while depending on their progress for its full benefits to be realized. In temperate environments the primary emphasis is on raising yield potential, especially as irrigation enhances the use of agrichemical inputs. Efficiency of water and energy use through the modification of physiological processes and of sensitivity to stress at various stages of the life cycle is also sought. In tropical environments, breeding for greater yield potential and more comprehensive pest and disease resistance are still important. However, shortening the length of the life cycle, reducing its sensitivity to seasonal signals and increasing yield per day may be more important than raising yield per crop because of the scope for multiple cropping made possible by irrigation in the tropics in the absence of contraints by low temperatures.

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