Ecology of the biting midge Leptoconops albiventris in French Polynesia. II. Location of breeding sites and larval microdistribution

Abstract. The habitat of the immature stages of Leptoconops albiventris de Meijere (Diptera: Ceratopogonidae) was found to be in beach sand located above the high tide level near creeping vegetation. The immatures were restricted to a narrow strip and most occurred in the upper 6 cm of sand. Within a given breeding site, larvae were aggregated in their distribution. Eggs were layed on the bare sand surface, from which the larvae apparently dispersed to the plant-covered sand and to deeper strata, before returning to the surface for pupation and emergence. The nature of these breeding sites suggests that it is possible to control L.albiventris populations. Recovery of immature stages from sand samples by a flotation method is described.     

Seawater temperature, Gambierdiscus spp. variability and incidence of ciguatera poisoning in French Polynesia

In the context of global warming and climate change, ciguatera disease is put forward as an indicator of environmental disturbance. However, to validate this indicator, some unknown parameters such as the delay between environmental perturbation and outbreaks of ciguatera need to be investigated. The main goal of this study was to investigate the temporal link between the growth of Gambierdiscus spp., and one of its influencing factors and the declared cases of ciguatera disease in humans. Algal cell density and seawater temperature (SWT) were recorded monthly from February 1993 to December 2001 on the Atimaono barrier reef of Tahiti Island. Reports of ciguatera cases were obtained from three community health clinics near the study sites. The autoregressive integrated moving average model (ARIMA) shows: (1) SWT were positively associated with Gambierdiscus spp. growth at a lagtime of 13 and 17 months (p < 0.001); (2) Gambierdiscus spp. growth measured at a given time is related to a peak number of cases of ciguatera recorded 3 months after peak densities of this dinoflagellate (p < 0.001). These results allow the construction of a predictive model of the temporal link between ciguatera disease in humans and its etiologic agent: Gambierdiscus spp. This model constructed by using 1993–1999 data, then validated by 2000–2001 data, demonstrates an appreciable ability to predict changes in the incidence of ciguatera disease following algae blooms.     

橘全爪螨春季高峰发生程度与气象因素的关系

本文探讨了橘全爪螨高峰发生程度与气象因素及天气过程的关系。结果表明：春季高峰由２次连续的高峰组成,且第二次高峰大于第一次高峰;第一次高峰发生在４月下旬到５月中旬,其发生程度主要受 ３月 ２０日～ ４月 ３０日气象因子和天气过程的影响,即日均温度≥ １２℃,降雨≤ ２ｍｍ、相对湿度（ＲＨ）≤８５％,持续时间越长发生程度越重;第二高峰发生在５月下旬至６月中旬,主要受５月１１日～６月 １０日气象因子和天气过程的影响,即日均温度 ２０～ ３０℃、降雨≤ １０ｍｍ的持续时间越长该螨的发生程度越严重。说明重庆地区橘全爪螨春季高峰严重发生的主要因素是在相应的时间内降雨少、气温变幅低,积温多和特定气象因子组合的天气持续过程。     

Ambient temperature effects on the extrinsic incubation period of Wuchereria bancrofti in Aedes polynesiensis: implications for filariasis transmission dynamics and distribution in French Polynesia.

Temperature effects on development of the human filarial parasite Wuchereria bancrofti (Cobbold) (Filaridea: Onchocercidae) in the main Pacific vector Aedes polynesiensis Marks (Diptera: Culicidae) are analysed in relation to ambient climatic conditions. A statistical model of the extrinsic cycle duration as a function of temperature is described and used to distinguish three patterns of W. bancrofti transmission dynamics: continuous, fluctuating and discontinuous, occurring from north to south geographically among French Polynesian archipelagos. In the northerly Marquesas Islands (8-11 degrees S) filariasis transmission is continuous and very active, facilitated by perennially high temperatures combined with constantly high rates of man-vector contact. In the southerly Australes Islands (21-28 degrees S) filariasis transmission is seasonally discontinuous and, during the cooler months (May-September), the model predicts virtually no transmission because the cycle duration exceeds the life expectancy of the vector. In the Society Islands (16-18 degrees S), between the Marquesas and Australes, transmission is predicted to be intermediate as expected from their latitude, with seasonally fluctuating transmission potential. In the Tuamotu Islands (also geographically intermediate: 14-23 degrees S), with theoretically perennial transmission potential, transmission occurs only intermittently, being limited by other human and environmental factors whereby man-vector contact is confined to seasonal agricultural situations. Generally, among French Polynesian archipelagos where Aedes polynesiensis is the vector, the transmission potential for W. bancrofti and resulting disease manifestations of lymphatic filariasis in humans are correlated with ambient temperature due to the degree of southern latitude.     

Large-scale synchrony and inter-annual variability in roach recruitment in the Rhône River: the relative role of climatic factors and density-dependent processes

1. We report patterns of temporal variation in the recruitment of roach ( Rutilus rutilus ). The data consist of the annual abundance of the first 2 year-classes, 0+ and 1+ fish, at four sites in the Rhône River (France) between 1987 and 1997. Over this 11-year period both 0+ and 1+ fish fluctuated strongly.
2. Cross-correlation indicated high spatial synchrony in 0+ dynamics, although correlations among sites in 1+ dynamics were weaker. No clear pattern was apparent in the relationship between the level of synchrony and distance between pairs of sites.
3. The spatial synchrony in 0+ fish could be attributable to large-scale variations in weather, influencing water temperature. Total body length of 0+ roach was correlated with water temperature (expressed in degree-days over 12 °C), and water temperature was the main factor explaining inter-annual variation in 0+ cohort size. Monthly variation in abiotic factors (measured by standard deviation in water temperature and discharge) did not influence 0+ fluctuations. Correlations with June water temperature suggest that year-class strength was mainly determined by abiotic factors during the first few months of life.
4. The absence of spatial synchrony in 1+ fluctuations suggests little correlation between survival and abiotic conditions during the first year of life, other factors influencing survival.
5. Survival in the first year was density-dependent. Intraspecific competition within the 0+ cohort could thus influence the fluctuations in recruitment to older age-classes.
6. The implications of age- or stage-dependent synchrony in temporal variation for species with complex life histories are discussed. Studying spatial synchrony for the different life history stages could enhance our understanding of the population dynamics of spatially structured species.     

Climate and vegetation in China V. Effect of climatic factors on the upper limit of distribution of evergreen broadleaf forest

In order to clarify correlations between the upper limit of distribution of evergreen broadleaf forest and climatic factors, 62 stands distributed at the upper limit of the forest were collected from various parts of China, and their thermal and precipitation factors were estimated. Among six thermal climatic indices, i.e., warmth index (WI), coldness index (CI) and annual mean (AMT), January mean (JMT), mean minimum (MMT) and minimum (MT) temperatures, the CI at the stands showed the smallest range of variance, and it was therefore considered to be the most significant for interpreting the upward distribution of the forest. However, the distribution of the forest in mountain areas in southwestern China could not be explained by lower temperatures in winter such as CI but by a cumulative temperature such as WI. The continentality and precipitation factors were also important for delimiting the distribution of the forest. In addition, the relation between the distribution of the forest and the MMT was noted, and it was concluded that the MMT was an effective thermal index for explaining the upper limit of distribution of evergreen broadleaf forest in China.     

Territorial behavior of the red admiral,Vanessa atalanta (Lepidoptera: Nymphalidae) I. The role of climatic factors and early interaction frequency on territorial start time

We examined the relative importance of climatic factors and population density to territorial start time ofVanessa atalanta males. Start time varies with solar altitude and therefore with seasons. We removed seasonal effects by converting start times to corresponding solar altitudes. Start time solar altitude correlates primarily with ambient temperature (T _a) and secondarily with substrate temperature (T _s), regardless of cloud cover. Overcast cloud cover resulted in later not earlier start times as expected from reduced solar radiation (R) levels. R may affect start time indirectly by affectingT _s and later start times under overcast skies may be a result ofT _s. Start times under solid overcast but not under broken overcast were different than under clear skies, suggesting thatV. atalanta males can use dim sun or blue patches in broken overcast as a start time cue. Early interaction frequency is correlated withT _a and wind direction, but not with start time itself, suggesting that male population density is unimportant compared with climatic factors. We conclude thatV. atalanta has a climate-dependent start time but, also, that maintaining a relatively fixed daily schedule is more important to males than is achieving an optimal body temperature while perching.