Geographic parthenogenesis in the Australian arid zone: I. A climatic analysis of the Heteronotia binoei complex (Gekkonidae)

Patterns of geographic parthenogenesis can provide insight into the ecological implications of the transition from sexual to parthenogenetic reproduction. We analysed quantitatively the environmental niches occupied by sexual and parthenogenetic geckos of the Heteronotia binoei complex in the Australian and zone. This complex consists of two independently derived maternal lineages of hybrid parthenogens, which, in turn, include two different triploid races that resulted from reciprocal backcrossing with the parental sexual taxa. The sexual progenitors are still extant and occupy very distinct environmental niches. The triploid parthenogenetic races are biased in their environmental niche towards those of the sexual races for which their genomes are biased and this dosage effect is apparent in both maternal lineages. Thus triploidy may have benefited the parthenogens through partial recovery of the parental niches. Although the parthenogens have a broader geographic distribution than their sexual progenitors, their environmental niche is narrower and biased towards one of the sexual races. In keeping with general patterns of geographic parthenogenesis. parthenogenetic H. binoei occupy a harsher environment than the sexual forms. occurring in regions of persistently low rainfall. Bioclimatic modelling suggests patterns of rainfall are important in limiting the distribution of sexual and parthenogenetic taxa. and extrapolation from the current bioclimatic profiles indicates potential for further eastward range expansion by the parthenogens.

Geographic parthenogenesis in the Australian arid zone: II. Climatic analysis of orthopteroid insects of the genera Warramaba and Sipyloidea

The Australian and zone harbours a surprising number of parthenogenetic organisms. including the well known case of the grasshopper Warramaba virgo. Less well known is the case of the stick insects of the Sipyloidea complex, which. despite its presence in the literature for over 15 years. has gone entirely unnoticed by workers in the field. We draw attention to the remarkable similarities between the evolution of parthenogenesis in Warramaba and Sipyloidea and analyse the geographic distributions of parthenogenetic and sexual forms with respect to six Climatic variables. We provide evidence that a combination of Climatic and vegetative barriers are responsible for the current distribution patterns in these taxa. Comparisons are also made with patterns of geographic parthenogenesis in lizards of the Heteronotia binoei complex. In general. there has been a strong tendency for parthenogenesis to originate via hybridization in the western part of the and zone with subsequent eastward spread throughout mulga woodlands and mallee shrublands where rainfall is both low and aseasonal. We propose that the hybridization events leading to parthenogenesis in these diverse taxa were driven by a common biogeographic process - that is, by range shifts associated with changes in aridity during the late Pleistocene.

Is the potential of Coccidoxenoides perminutus, a mealybug parasitoid, limited by climatic or nutritional factors?

The encyrtid Coccidoxenoides perminutus is a widely distributed parasitoid of citrus mealybug (Planococcus citri). Worldwide, it has been implicated in successful biocontrol in only a few widely separated localities. C perminutus contributes little to control P. citri in field situations in south-east Queensland, Australia, but invades insectary cultures and reduces mealybug populations considerably under these controlled conditions. This discrepancy between poor field performance and good performance under controlled conditions was investigated to establish whether climatic factors inhibit the field performance of this species in the biological control of P. citri. Subsequent laboratory examination of the influence of varied humidities and temperatures on the activity levels and survival of C perminutus revealed a low tolerance for high saturation deficits (i.e., low % RH at high T degreesC) with reduced reproductive output. The influence of different food sources on adult survival and reproduction was also quantified, to establish if the adverse effects of climate could be overcome by supplementing adult diet. Neither honeydew from their mealybug hosts nor nectar from Alphitonia flowers significantly enhanced parasitoid survival. A subsequent test of five nectar species revealed a significant difference in their influence on C. perminutus survival and reproduction, with only Alpinia zerumbet proving to be as suitable as honey. The floral species that proved suitable in the laboratory need to be checked for their attractiveness to C perminutus in the field and for their ability to enhance the survival and reproductive output of parasitoids. This information suggests that the prevailing dry conditions in south-east Queensland citrus-growing areas apparently impede successful biological control of P. citri by C perminutus, but possibilities are available for habitat manipulation (by providing suitable nectar sources for adult parasitoids) to conserve and enhance C perminutus activity in the field. (C) 2004 Elsevier Inc. All rights reserved.

High-frequency winter cooling and reef coral mortality during the Holocene climatic optimum

A detailed ecological, micro-structural and skeletal Sr/Ca study of a 3.42 m thick Goniopora reef profile from an emerged Holocene reef terrace at the northern South China Sea reveals at least nine abrupt massive Goniopora stress and mortality events occurred in winter during the 7.0-7.5 thousand calendar years before present (cal. ka BP) (within the Holocene climatic optimum). Whilst calculated Sr/Ca-SST (sea surface temperature) maxima during this period are comparable to those in the 1990s, Sr/Ca-SST minima are significantly lower, probably due to stronger winter monsoons. Such generally cooler winters, superimposed by further exceptional winter cooling on inter-annual to decadal scales, may have caused stress and mortality of the corals about every 50 years. Sea level rose by similar to 3.42 m during this period, with present sea-level reached at similar to 7.3 ka BP and a sea-level highstand of at least similar to 1.8 m occurred at similar to 7.0 ka. The results show that it took about 20-25 years for a killed Goniopora coral reef to recover. (C) 2004 Elsevier B.V. All rights reserved.

Differences in climatic factors between Ross River virus disease outbreak and nonoutbreak years

Ross River virus is a common mosquito-borne arbovirus responsible for outbreaks of polyarthritic disease throughout Australia. To better understand climatic factors preceding outbreaks, we compared seasonal and monthly rainfall and temperature trends in outbreak and nonoutbreak years at four epidemic-prone locations. Our analyses showed that rainfall in outbreak years tended to be above average and higher than rainfall in nonoutbreak years. Overall temperatures were warmer during outbreak years. However, there were a number of distinct deviations in temperature, which seem to play a role in either promoting or inhibiting outbreaks. These preliminary findings show that climatic differences occur between outbreak and nonoutbreak years; however, seasonal and monthly trends differed across geo-climatic regions of the country. More detailed research is imperative if we are to optimize the surveillance and control of epidemic polyarthritic disease in Australia.

Forecasting Helicoverpa populations in Australia: A comparison of regression based models and a bio-climatic based modeling approach

Long-term forecasts of pest pressure are central to the effective management of many agricultural insect pests. In the eastern cropping regions of Australia, serious infestations of Helicoverpa punctigera (Wallengren) and H. armigera (Hübner)(Lepidoptera: Noctuidae) are experienced annually. Regression analyses of a long series of light-trap catches of adult moths were used to describe the seasonal dynamics of both species. The size of the spring generation in eastern cropping zones could be related to rainfall in putative source areas in inland Australia. Subsequent generations could be related to the abundance of various crops in agricultural areas, rainfall and the magnitude of the spring population peak. As rainfall figured prominently as a predictor variable, and can itself be predicted using the Southern Oscillation Index (SOI), trap catches were also related to this variable. The geographic distribution of each species was modelled in relation to climate and CLIMEX was used to predict temporal variation in abundance at given putative source sites in inland Australia using historical meteorological data. These predictions were then correlated with subsequent pest abundance data in a major cropping region. The regression-based and bioclimatic-based approaches to predicting pest abundance are compared and their utility in predicting and interpreting pest dynamics are discussed.

Climatic variability in the southwest Pacific during the Last Termination (20-10 kyr BP)

The degree to which palaeoclimatic changes in the Southern Hemisphere co-varied with events in the high latitude Northern Hemisphere during the Last Termination is a contentious issue, with conflicting evidence for the degree of 'teleconnection' between different regions of the Southern Hemisphere. The available hypotheses are difficult to test robustly, however, because there are few detailed palaeoclimatic records in the Southern Hemisphere. Here we present climatic reconstructions from the southwestern Pacific, a key region in the Southern Hemisphere because of the potentially important role it plays in global climate change. The reconstructions for the period 20-10 kyr BP were obtained from five sites along a transect from southern New Zealand, through Australia to Indonesia, supported by 125 calibrated C-14 ages. Two periods of significant climatic change can be identified across the region at around 17 and 14.2 cal kyr BP, most probably associated with the onset of warming in the West Pacific Warm Pool and the collapse of Antarctic ice during Meltwater Pulse-1A, respectively. The severe geochronological constraints that inherently afflict age models based on radiocarbon dating and the lack of quantified climatic parameters make more detailed interpretations problematic, however. There is an urgent need to address the geochronological limitations, and to develop more precise and quantified estimates of the pronounced climate variations that clearly affected this region during the Last Termination. (c) 2005 Elsevier Ltd. All rights reserved.

Climatic regulation of seed dormancy and emergence of diverse Malva parviflora populations from a Mediterranean-type environment

Malva parviflora L. (Malvaceae) is rapidly becoming a serious weed of Australian farming systems. An understanding of the variability of its seed behaviour is required to enable the development of integrated weed management strategies. Mature M. parviflora seeds were collected from four diverse locations in the Mediterranean-type climatic agricultural region of Western Australia. All of the seeds exhibited physical dormancy at collection; manual scarification or a period of fluctuating summer temperatures (50/20 degrees C or natural) were required to release dormancy. When scarified and germinated soon (1 month) after collection, the majority of seeds were able to germinate over a wide range of temperatures (5-37 degrees C) and had no light requirement. Germination was slower for seeds stored for 2 months than seeds stored for 2 years, suggesting the presence of shallow physiological dormancy. Seed populations from regions with similar annual rainfall exhibited similar dormancy release patterns; seeds from areas of low rainfall (337-344mm) were more responsive to fluctuating temperatures, releasing physical dormancy earlier than those from areas of high rainfall (436-444mm). After 36 months, maximum seedling emergence from soil in the field was 60%, with buried seeds producing 13-34% greater emergence than seeds on the surface. Scanning electron microscopy of the seed coat revealed structural differences in the chalazal region of permeable and impermeable seeds, suggesting the importance of this region in physical dormancy breakdown of M. parviflora seeds. The influence of rainfall during plant growth in determining dormancy release, and hence, germination and emergence timing, must be considered when developing management strategies for M. parviflora.

Fossil trees in ancient fluvial channel deposits: evidence of seasonal and longer-term climatic variability

It has been established that large numbers of certain trees can survive in the beds of rivers of northeastern Australia where a strongly seasonal distribution of precipitation causes extreme variations in flow on both a yearly and longer-term basis. In these rivers, minimal flow occurs throughout much of any year and for periods of up to several years, allowing the trees to become established and to adapt their form in order to facilitate their survival in environments that experience periodic inundation by fast-flowing, debris-laden water. Such trees (notably paperbark trees of the angiosperm genus Melaleuca) adopt a reclined to prostrate, downstream-trailing habit, have a multiple-stemmed form, modified crown with weeping foliage, development of thick, spongy bark, anchoring of roots into firm to lithified substrates beneath the channel floor, root regeneration, and develop in flow-parallel, linear groves. Individuals from within flow-parallel, linear groves are preserved in situ within the alluvial deposit of the river following burial and death. Four examples of in situ tree fossils within alluvial channel deposits in the Permian of eastern Australia demonstrate that specialised riverbed plant communities also existed at times in the geological past. These examples, from the Lower Permian Carmila Beds, Upper Permian Moranbah Coal Measures and Baralaba Coal Measures of central Queensland and the Upper Permian Newcastle Coal Measures of central New South Wales, show several of the characteristics of trees described from modern rivers in northeastern Australia, including preservation in closely-spaced groups. These properties, together with independent sedimentological evidence, suggest that the Permian trees were adapted to an environment affected by highly variable runoff, albeit in a more temperate climatic situation than the modem Australian examples. It is proposed that occurrences of fossil trees preserved in situ within alluvial channel deposits may be diagnostic of environments controlled by seasonal and longer-term variability in fluvial runoff, and hence may have value in interpreting aspects of palaeoclimate from ancient alluvial successions. (C) 2001 Elsevier Science B.V. All rights reserved.