Learning to Be an Anthropologist and Remaining "Native."

Learning to Be an Anthropologist and Remaining "Native." Beatrice Medicine with Sue-Ellen Jacobs, ed. Champaign: University of Illinois Press, 2001. 371 pp.     

Detrimental effects of recent ocean surface warming on growth condition of Atlantic salmon

Ocean climate impacts on survivorship and growth of Atlantic salmon are complex, but still poorly understood. Stock abundances have declined over the past three decades and 1992–2006 has seen widespread sea surface temperature (SST) warming of the NE Atlantic, including the foraging areas exploited by salmon of southern European origin. Salmon cease feeding on return migration, and here we express the final growth condition of year‐classes of one‐sea winter adults at, or just before, freshwater re‐entry as the predicted weight at standard length. Two independent 14‐year time series for a single river stock and for mixed, multiple stocks revealed almost identical temporal patterns in growth condition variation, and an overall trend decrease of 11–14% over the past decade. Growth condition has fallen as SST anomaly has risen, and for each year‐class the midwinter (January) SST anomalies they experienced at sea correlated negatively with their final condition on migratory return during the subsequent summer months. Stored lipids are crucial for survival and for the prespawning provisioning of eggs in freshwater, and we show that under‐weight individuals have disproportionately low reserves. The poorest condition fish (～30% under‐weight) returned with lipid stores reduced by ～80%. This study concurs with previous analyses of other North Atlantic top consumers (e.g. somatic condition of tuna, reproductive failure of seabirds) showing evidence of major, recent climate‐driven changes in the eastern North Atlantic pelagic ecosystem, and the likely importance of bottom‐up control processes. Because salmon abundances presently remain at historical lows, fecundity of recent year‐classes will have been increasingly compromised. Measures of year‐class growth condition should therefore be incorporated in the analysis and setting of numerical spawning escapements for threatened stocks, and conservation limits should be revised upwards conservatively during periods of excessive ocean climate warming.     

Climate change induced hybridization in flying squirrels

There is now unequivocal evidence for global climate change; however, its potential impacts on evolutionary processes remain unclear. Many species have responded to contemporary climate change through shifts in their geographic range. This could lead to increased sympatry between recently diverged species; likely increasing the potential for hybridization. Recently, following a series of warm winters, southern flying squirrels ( Glaucomys volans ) in Ontario, Canada rapidly expanded their northern range limit resulting in increased sympatry with the closely related northern flying squirrel ( Glaucomys sabrinus ). This provided the opportunity to test the prediction that contemporary climate change can act as a catalyst creating conditions for the formation of hybrid zones. Following extensive sampling and molecular analyses (nuclear and mitochondrial DNA), we identified the occurrence of hybridization between sympatric G. sabrinus and G. volans . There was evidence of backcrossing but not of extensive introgession, consistent with the hypothesis of recent rather than historic hybridization. To our knowledge, this is the first report of hybrid zone formation following a range expansion induced by contemporary climate change. This is also the first report of hybridization between North American flying squirrel species.     

Resolving the population status of Ascension Frigatebird Fregata aquila using a 'virtual ecologist' model

The Ascension Frigatebird is an island endemic whose conservation status was subject to confusion owing to difficulties in counting and misinterpretation of data. Accurate nest counts for this species are problematic owing to their extremely prolonged breeding seasons, high nest failure rates, turnover of individuals at nest-sites, replacement laying and biennial breeding. We conducted repeated complete censuses of Ascension Frigatebird eggs at the species' sole colony of Boatswainbird Island, and collected data on laying phenology and nest survival rates within sample quadrats, throughout the 2001 and 2002 breeding seasons. We used these data to develop an individual-based model that predicted the number of Frigatebird nests present on each day an actual census occurred assuming an arbitrary 1000 breeding females bred there. We then divided the number of nests counted in these virtual censuses by 1000 to quantify bias, and used this figure to correct real census totals. The model revealed that the population numbered c. 6250 breeding females and c . 9350 mature females in 2001–2, and that numbers have not changed significantly since the late 1950s. Productivity, at 0.34 chicks/pair, was high compared to previous studies of Ascension Frigatebirds and most of those of congeners elsewhere.     

Effects of soil characteristics and human disturbance on tiger beetle oviposition

Abstract 1. Understanding species‐specific habitat requirements is important in insect ecology. Co‐occurrence of closely related species can provide insight into microhabitat segregation. Tiger beetles are well suited for such studies, as they occur in multi‐species assemblages, exhibit species‐specific habitat requirements, and are sensitive to anthropogenic modifications of the environment. 2. This study investigated ovipositional microhabitat choice of two sympatric tiger beetles at Point Reyes National Seashore, California, U.S.A., and evaluates how human activity affects that choice. Cicindela oregona is widespread and common whereas C. hirticollis, an undescribed subspecies, is locally threatened. Laboratory experiments tested oviposition‐site selection of the two species in response to variations in moisture, pH, salinity, and grain size. Field experiments tested larval burrow location in response to experimental shading and experimental human disturbance. 3. Laboratory results indicated that while C. hirticollis females preferred a narrow range of moisture levels and fine sands, C. oregona females had more specific pH and salinity requirements and preferred coarser sands. They also differed in timing of activity. Preferences are probably related to prevention of fungal or bacterial infection and avoidance of desiccation and immersion. 4. In the field, significantly more larval burrows were found under experimental shading for both species. In addition, repeated human compaction of the sand significantly decreased the number of larval burrows. 5. Results suggest that protection of microhabitat, restoration of native plants, and limitation of human traffic are vital in the conservation management of tiger beetles.     

印度查谟地区甜橙上柑桔潜叶蛾为害动态及其与重要气候因子的关系(英文)

本研究旨在揭示印度查谟柑桔潜叶蛾Phyllocnistis citrella Stainton为害甜橙Citrus sinensis的季节性变化,以及降雨量、相对湿度和温度等重要的气候因子对其种群的影响。本文对不同季节印度查谟的一个甜橙园里的柑桔潜叶蛾丰度进行了调查, 从2005年3月到2008年2月每两周调查一次。柑桔潜叶蛾在一年内有3个为害高峰,分别是4月中旬、7月中旬和9月中旬,这与甜橙新营养梢的生长期相吻合。相关分析表明,上午和下午的相对湿度和平均相对湿度与柑桔潜叶蛾的数量呈负相关;然而,平均降雨量、最高气温、最低气温和平均气温与柑桔潜叶蛾的数量呈正相关。降雨量和温度与柑桔潜叶蛾为害程度呈显著正相关。总之,柑桔潜叶蛾的数量不能简单地通过观察某一特殊地区的相对湿度来预测,而降雨量和温度在影响虫害方面均起着重要的作用。     

Decreased precipitation exacerbates the effects of sea level on coastal dune ecosystems in open ocean islands

The alteration of fresh and marine water cycling is likely to occur in coastal ecosystems as climate change causes the global redistribution of precipitation while simultaneously driving sea‐level rise at a rate of 2–3 mm yr^?1. Here, we examined how precipitation alters the ecological effects of ocean water intrusion to coastal dunes on two oceanic carbonate islands in the Bahamas. The approach was to compare sites that receive high and low annual rainfall and are also characterized by seasonal distribution (wet and dry season) of precipitation. The spatial and temporal variations in precipitation serve as a proxy for conditions of altered precipitation which may occur via climate change. We used the natural abundances of stable isotopes to identify water sources (e.g., precipitation, groundwater and ocean water) in the soil–plant continuum and modeled the depth of plant water uptake. Results indicated that decreased rainfall caused the shallow freshwater table on the dune ecosystem to sink and contract towards the inland, the lower freshwater head allowed ocean water to penetrate into the deeper soils, while shallow soils became exceedingly dry. Plants at the drier site that lived nearest to the ocean responded by taking up water from the deeper and consistently moist soil layers where ocean water intruded. Towards the inland, decreased rainfall caused the water table to sink to a depth that precluded both recharge to the upper soil layers and access by plants. Consequently, plants captured water in more shallow soils recharged by infrequent rainfall events. The results demonstrate dune ecosystems on oceanic islands are more susceptible to ocean water intrusion when annual precipitation decreases. Periods of diminished precipitation caused drought conditions, increased exposure to saline marine water and altered water‐harvesting strategies. Quantifying species tolerances to ocean water intrusion and drought are necessary to determine a threshold of community sustainability.