| 1. |
- Hobson, Keith A., et al.
(författare)
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A feather hydrogen isoscape for Mexico
- 2009
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Ingår i: Journal of Geochemical Exploration. - : Elsevier BV. - 0375-6742. ; 102:2, s. 63-70
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Tidskriftsartikel (refereegranskat)abstract
- Developing useful biological isoscapes for areas of the world is a priority. This is the case for Mexico that hosts a large percentage of North America's Neotropical migrant birds. Here we investigated the use of House Sparrow (Passer domesticus) feathers to create a spatially explicit feather deuterium isoscape for that country using samples (n=461) that were collected across Mexico. Considerable and useful spatial hydrogen isotopic structure was observed, suggesting that isotopes may be a potential forensic tool for evaluating origins of Mexican derived fauna and. ora. The most positive feather delta D values occurred in the northeast and most negative in the south-central part of the country, roughly matching delta D patterns observed in groundwater. A weak negative isotopic relationship was found with altitude in both the Pacific and Atlantic drainage systems. The most parsimonious model describing isotopic spatial variation in feathers between 300 and 3000 m a.s.l. included groundwater delta D (delta D-gw; precipitation proxy), sex, amount of precipitation, and the coefficient of variation in amount of precipitation. Overall, delta D-gw was a poor predictor of sparrow delta D-f values for all of Mexico. However, this relationship was considerably strengthened when we considered sex separately, removed the Baja peninsula from our sample, and considered the Atlantic and Pacific drainage basins separately. The strongest relationship between delta D-gw and delta D-f was found for female sparrows in the Atlantic drainage basin (r(2)=0.464). We recommend that researchers interested in inferring origins of migratory birds and other animals in Mexico create species specific isotopic basemaps that may be guided by the isotopic patterns we have observed for House Sparrows and groundwater. (C) 2009 Published by Elsevier B.V.
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| 2. |
- Hobson, Keith A., et al.
(författare)
-
A feather hydrogen isoscape for Mexico
- 2009
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Ingår i: Journal of Geochemical Exploration. - : Elsevier BV. - 0375-6742 .- 1879-1689. ; 102:3, s. 167-174
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Tidskriftsartikel (refereegranskat)abstract
- Developing useful biological isoscapes for areas of the world is a priority. This is the case for Mexico that hosts a large percentage of North America's Neotropical migrant birds. Here we investigated the use of House Sparrow (Passer domesticus) feathers to create a spatially explicit feather deuterium isoscape for that country using samples (n=461) that were collected across Mexico. Considerable and useful spatial hydrogen isotopic structure was observed, suggesting that isotopes may be a potential forensic tool for evaluating origins of Mexican derived fauna and flora. The most positive feather delta D values occurred in the northeast and most negative in the south-central part of the country, roughly matching delta D patterns observed in groundwater. A weak negative isotopic relationship was found with altitude in both the Pacific and Atlantic drainage systems. The most parsimonious model describing isotopic spatial variation in feathers between 300 and 3000 m a.s.l. included groundwater delta D (delta D-gw; precipitation proxy), sex, amount of precipitation, and the coefficient of variation in amount of precipitation. Overall, delta D-gw was a poor predictor of sparrow delta D-f values for all of Mexico. However, this relationship was considerably strengthened when we considered sex separately, removed the Baja peninsula from our sample, and considered the Atlantic and Pacific drainage basins separately. The strongest relationship between delta D-gw and delta D-f was found for female sparrows in the Atlantic drainage basin (r(2)=0.464). We recommend that researchers interested in inferring origins of migratory birds and other animals in Mexico create species specific isotopic basemaps that may be guided by the isotopic patterns we have observed for House Sparrows and groundwater. (C) 2009 Published by Elsevier B.V.
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| 3. |
- Wassenaar, Leonard I., et al.
(författare)
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A groundwater isoscape (δD, δ18O) for Mexico
- 2009
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Ingår i: Journal of Geochemical Exploration. - : Elsevier BV. - 0375-6742 .- 1879-1689. ; 102:3, s. 123-136
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Tidskriftsartikel (refereegranskat)abstract
- Numerous studies have shown that precipitation isocapes drive δD and δ18O patterns in surficial waters and in terrestrial food webs. While the GNIP (Global Network for Isotopes in Precipitation) dataset provided a key foundation for linking precipitation-terrestrial isoscapes globally, it has insufficient spatial coverage in many countries like Mexico. To overcome this limitation, we hypothesized that shallow phreatic groundwaters in Mexico could be used as an isotopic integrator of long-term seasonally weighted precipitation inputs to the landscape to aid in calibrating spatial H and O isotope datasets for terrestrial, biological and hydrological research. Groundwater was sampled from 234 sites in Mexico at ~ 50 km latitudinal spacing to obtain high spatial resolution and country-wide coverage for the construction of a groundwater isoscape. Our data revealed that shallow groundwater infiltration in Mexico appears largely unaffected by evaporation and reflects seasonally weighted precipitation inputs. These precipitation inputs are primarily biased to summertime when highest rainfall occurs, but a small degree of post-precipitation evaporation revealed a lower d-excess zone that corresponded to the interior semi-arid ecozone. We developed a predictive general linear model (GLM) for hydrogen and oxygen isotopic spatial patterns in Mexican groundwater and then compared the results to a validation subset of our field data, as well external data reported in the literature. The GLM used elevation, latitude, drainage basin (Atlantic vs. Pacific), and rainfall as the most relevant predictive variables. The GLM explained 81% of the overall isotopic variance observed in groundwater, 68% of the variance within our validation subset, and 77% of the variance in the external data set. Our predictive GLM is sufficiently accurate to allow for future ecological, hydrological and forensic isoscape applications in Mexico, and may be an approach that is applicable to other countries and regions where GNIP stations are lacking.
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| 4. |
- Brattström, Oskar, et al.
(författare)
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Placing butterflies on the map - testing regional geographical resolution of three stable isotopes in Sweden using the monophagus peacock Inachis io
- 2008
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 31:4, s. 490-498
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Tidskriftsartikel (refereegranskat)abstract
- Stable isotope analyses of tissues have been used to help delineate natal regions and routes of migratory animals. The foundations of such studies are isotopic gradients or differences representing geographic regions and habitat used by the organism that are retained in selected tissues. We sampled peacock butterflies Inachis io on a regional level in southern Sweden to study natural variation and the resolving power of the stable isotope method to delineate individuals from known areas on a smaller scale than has typically been used in previous studies. Hydrogen (delta D), carbon (delta C-13) and nitrogen (delta N-15) isotopes were obtained from butterflies at seven different locations in an area of 250x250 km over three years (2002-2004). We found sufficient isotopic differences on this regional scale to delineate approximate origins. Of the three isotopes, deuterium showed good discrimination between sites, carbon isotopes showed weaker differentiation, whereas nitrogen isotopes proved unsuitable for small scale studies in this region due to high and unpredictable variation. We found there was enough variation in delta D between years to prevent a general application of the technique to resolve sub-regional variation. Substantial part of this variation was probably caused by seasonal changes in delta D of precipitation. These differences produce significant variation in delta D between years in animals having short and variable tissue development times, and are difficult to estimate in natural situations. We conclude that stable isotopes are potentially powerful predictors for studies of migratory butterflies in Europe. However, without good knowledge about the sampled individuals' previous life-history, a lot of the natural environmental variation in tissue delta D cannot be controlled for. In the case of migratory species, this information is difficult to obtain, making the confidence intervals for prediction of natal areas fairly wide and probably only suitable for longer distance migration.
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