Temporal Variation In Relative Abundance Research Articles

Indian monsoon variability in the last 2000 years as inferred from benthic foraminifera

The effect of ambient conditions on living (Rose-Bengal stained) benthic foraminifera has been studied from the shelf and slope of the central-western Bay of Bengal to assess the applicability of temporal changes in benthic foraminiferal morpho-groups (angular asymmetrical and rounded symmetrical) to reconstruct past monsoon changes. We report that the riverine influx and associated processes control the relative abundance of angular asymmetrical (AABF) and rounded symmetrical (RSBF) benthic foraminiferal morpho-groups in the central-western Bay of Bengal. Subsequently, temporal variations in relative abundance of AABF in a gravity core collected from outfall region of the Pennar River, are used to reconstruct decadal scale past monsoon variability during the last ∼1887 years. An increased monsoon discharge is observed during the Medieval Warm Period (MWP) and lower during the Little Ice Age (LIA). The periodic changes with a frequency of ∼123 and ∼238 years are also identified, indicating a close relationship between monsoon and solar activity.

Solar agreement targets Italians

The effect of ambient conditions on living (Rose-Bengal stained) benthic foraminifera has been studied from the shelf and slope of the central-western Bay of Bengal to assess the applicability of temporal changes in benthic foraminiferal morpho-groups (angular asymmetrical and rounded symmetrical) to reconstruct past monsoon changes. We report that the riverine influx and associated processes control the relative abundance of angular asymmetrical (AABF) and rounded symmetrical (RSBF) benthic foraminiferal morpho-groups in the central-western Bay of Bengal. Subsequently, temporal variations in relative abundance of AABF in a gravity core collected from outfall region of the Pennar River, are used to reconstruct decadal scale past monsoon variability during the last ∼1887 years. An increased monsoon discharge is observed during the Medieval Warm Period (MWP) and lower during the Little Ice Age (LIA). The periodic changes with a frequency of ∼123 and ∼238 years are also identified, indicating a close relationship between monsoon and solar activity.

Population Trends and Implications for Monitoring Cactus Ferruginous Pygmy Owls in Northern Mexico

Although once described as common in lowland central and southern Arizona (Bendire 1888, Fisher 1893, Breninger 1898, Gilman 1909, Bent 1938), cactus ferruginous pygmy owls (Glaucidium brasilianum cactorum; hereafter, pygmy owls) have been extirpated throughout much of their former range in Arizona. As a result, this northernmost subspecies of ferruginous pygmy owls (Van Rossem 1937, Johnsgard 1988) are now listed as endangered by the U.S. Fish and Wildlife Service (USFWS 1997, Hardy et al. 1999). Immediately south of Arizona in northern Sonora, Mexico, pygmy owls occur primarily in desert-scrub and grassland vegetation communities where woodlands are near stands of large saguaro cacti (Carnegia gigantea) (Flesch 2003a). Because pygmy owls are thought to be abundant in northern Sonora, these populations may prove critical for recovery in Arizona as well as for long-term persistence of pygmy owls in the Sonoran Desert. Natural or facilitated dispersal of pygmy owls from Sonora may augment populations in Arizona, especially when combined with habitat management (USFWS 2003). Numerous threats to pygmy-owl habitat exist in northern Sonora, however, including woodcutting, vegetation clearing for agriculture or buffelgrass (Pennisetum ciliare), and overgrazing, and there are few regulatory mechanisms in place to protect habitat. Despite the importance of pygmy-owl populations in northern Sonora, there are currently no data on population trends or on design parameters for population monitoring. Therefore, between 2000 and 2004 we monitored relative abundance of pygmy owls in northern Sonora, estimated temporal variation in relative abundance, and assessed the efficacy of different sampling designs for monitoring population trends. Our goals were to assess population trends, determine environmental factors that explained variation in trends, and evaluate the statistical power of our monitoring program for future monitoring efforts.

Geographical distributions, relative abundance and coexistence of Drosophila aldrichi and Drosophila buzzatii in Australia

Abstract Climatic data and collection records for the cactophilic Drosophila aldrichi and Drosophila buzzatii for 97 localities were used to examine the effects of geographical location, season, host plant species and climatic factors on their range and relative abundance. Temporal variation in relative abundance was assessed from monthly collections over 4 years at one locality. Effects of weather variables over the 28 days before each collection were examined. A generalized linear model of the spatial data showed significant geographical variation in relative abundance, and significant climatic effects, with the proportion of D. aldrichi higher in the warm season, and increasing as temperature variation decreased and moisture indices increased. The temporal data gave generally concordant results, as D. aldrichi proportion was higher in summer and autumn, and increased as maximum and minimum temperatures increased, and as variation in maximum temperature decreased. In a laboratory competition experiment, D. aldrichi eliminated D. buzzatii at 31°C, but was itself eliminated at 18°C and 25°C. The range of D. buzzatii is constrained only by availability of its host plant, Opuntia species, although its relative abundance is reduced in the northern part of its distribution. The range of D. aldrichi, from central Queensland to northern NSW, Australia, is entirely within that of D. buzzatii, and its relative abundance decreases from north to south. Both climate and weather, particularly temperature variability, have direct effects on the relative abundances of the two species, and both likely act indirectly by influencing the outcome of interspecific competition.

Seasonality of biogenic particle and planktonic foraminifera fluxes: response to hydrographic variability in the Kuroshio Extension, northwestern Pacific Ocean

In order to infer the relationship between the sinking biogenic particles as well as planktonic foraminiferal fluxes to local hydrography time-series sediment trap observations were conducted at two stations, Stations WCT-3 and -7, along the Kuroshio Extension (KE) in the northwestern Pacific. The sediment trap samples were collected from 29 August 1998 to 10 August 1999 at Station WCT-3 and from 19 August 1999 to 29 August 2000 at Station WCT-7. Large seasonal, spatial and depth variations were observed in the total mass flux and the biogenic particle fluxes at both stations. The annual mean mass flux in the deep trap is ∼3 times higher than that in the shallow trap at Station WCT-3 and around twice at Station WCT-7. No distinct seasonality of biogenic particles as well as planktonic foraminiferal fluxes was observed at WCT-3 except very high fluxes during summer both in shallow and deep traps. On the other hand, a distinct bi-modal distribution of all biogenic particle fluxes was observed over almost one year at Station WCT-7, with a comparatively low value in winter and high peak in summer in both shallow and deep traps. The concentration of calcium carbonate and the organic matter decreased with depth and those of biogenic opal increased with depth at both stations. The increased fluxes of all biogenic particles in the deep traps at both stations can be explained by lateral transport. The most abundant planktonic foraminiferal species at both stations are Neogloboquadrina pachyderma (dex. and sin.), Neogloboquadrina dutertrei, Globigerina bulloides, Globigerinoides ruber, Globigerinoides sacculifer, Globigerinoides tenellus, Globigerinella aequilateralis and Globigerinita glutinata. Despite some temporal variations in relative abundance, dominant planktonic foraminiferal species showed similar distribution pattern throughout the year at both stations. Seasonal variation in species dominance also occurs at both stations, changing from G. ruber, G. tenellus and G. sacculifer in September–November to Globorotalia truncatulinoides, Globorotalia inflata and G. glutinata in January–April, and to N. pachyderma, N. dutertrei and G. bulloides in May–July. The magnitude of test fluxes and species turnover showed strong seasonality in accordance with variations in the local hydrography, which is influenced by the shift of the meandering Kuroshio and by the interaction between the subarctic water mass (Oyashio) and KE waters. The influence of local hydrography on the foraminiferal fluxes is highlighted by the simultaneous increase in total foraminiferal flux with an increase in sea-surface temperature (SST) as well as a strengthening in the stratification of the water column.

Human onchocerciasis in the Amazonian area of southern Venezuela: spatial and temporal variations in biting and parity rates of black fly (Diptera: Simuliidae) vectors.

We investigated some entomological factors underlying altitudinal prevalence variation in the Venezuelan Amazonia human onchocerciasis focus. Spatial and temporal variation in relative abundance, daily biting rate, proportion of parous flies, and monthly parous biting rate were studied for the three main simuliid vectors (based on their vectorial competence: Simulium oyapockense s.l. Floch & Abonnenc approximately = S. incrustatum Lutz << S. guianense s.l. Wise). Yanomami villages were selected among sentinel communities of the ivermectin control program, representing hypo- to hyperendemicity conditions of infection. Spatial variation was explored via increasing village altitude on two river systems (A: Ocamo-Putaco and B: Orinoco-Orinoquito). Temporal variation was studied between 1995 and 1999 by sampling the biting population during dry and rainy mouths. Environmental variables included monthly rainfall and maximum river height. Simuliid species composition itself varied along the altitudinal and prevalence gradient. S. oyapockense s.l. prevailed below 150 m. Above this altitude and up to 240 m, S. incrustatum and S. guianense s.l. became more frequently and evenly collected along A but not along B, where S. incrustatum remained absent. The daily biting rate of S. oyapockense s.l. was higher during the dry season along A, whereas the converse took place along B. Daily biting rate of S. incrustatum was lowest during early rains. By contrast, the daily biting rate of S. guianense s.l. was highest during this period. There was a significant negative cross-correlation between proportion of parous of S. oyapockense s.l. and river height (2 and 3 mo lagged), whereas this variable (1 and 2 mo lagged) was positively correlated with the proportion of parous flies for S. incrustatum. Monthly parous biting rate values suggest that the months contributing most to onchocerciasis transmission in the area are likely to be the dry season and the transition periods between seasons.