climate
Snails and climate
30-10-2009 19:50
Earlier on, I reported
on a dispute in literature about snails in the
desert
near Antofagasta, Chile. Essentially, it was about the
influence of the climate on shell shape. Hyperarid
areas like the Atacama desert are a special
habitat for snails and if unusual shell shapes are
found it is very interesting.
Also in southern Peru snails may be found in the very arid coastal area.
This is a picture taken by Ralf Hesse near Nazca. A detailed shot reveals that here there are two forms present. The slender form resembles Bostryx hennahi (Gray, 1830), the stouter shells B. styliger (Beck, 1832).
It became interesting when I saw different photographs taken by him in the same area. These show that the latter species exhibits a transition to carinate forms; the latter resembles Bostryx reentsi (Philippi, 1851) known to occur slightly more southward near Chala.
This carination is hypothesized to be the result of ‘ecological stress’, in the case of the Chilean species by displacement through flooding or mud streams beyond the limits of their normal habitat. Indeed, there is reference in literature about climatic variability along the Chilean and southern Peruvian coast (Garreaud & Battisti, 1999; Vargas et al., 2006), due to the El Niño phenomenon.
Recently, studies have suggested that this mechanism also extended to the Nazca region during Pleistocene times (Eitel et al., 2005; Mächtle et al, in press). They hypothesize that a much more humid climate existed during the Pleistocene, with an increased aridification during the Holocene. Between 1000-1400 a semi-arid period would have occurred. The presence of loess in parts of the area on the flank of the Andes is an important argument in their papers. Radiocarbon dating of shells found amidst the loess dates this layer at ca. 10.000 yr BP. They postulate that the formation of the loess was influenced by monsoons crossing the Andes from Amazonia and leading to a higher precipitation.
Figure 3 from Mächtle et al. (in press), with the erroneous classification as Scutalus chiletensis granulatus Weyrauch; this is a species from N-Peru.
Hesse & Baade (2007) pointed out that an alternative explanation for the loess formation could be the fog vegetation occurring in coastal Peru and Chile (Garreaud et al., 2008). The occurrences of floods and debris flows has been recorded for the Ilo region in southern Peru (Keefer et al., 2003), but it may have also occurred in the Nazca region.
In conclusion, the occurrence of carinate shells with a transition to normal shell forms near Nazca is an interesting find. And although the evidence provided in literature points to floods and debris flows as a possible factor, more detailed research is needed to understand the mechanism of carination at play here.
References:
Eitel, B., Hecht, S., Mächtle, B., Schukraft, G., Kadereit, A., Wagner, G.A., Kromer, B., Unkel, I. & Rendel, M., 2005. Geoarchaeological evidence from desert loess in the Nazca-Palpa region, southern Peru: palaeoenvironmental changes and their impact on pre-Columbian cultures. - Archaeometry 47: 137-158.
Garreaud, R. & Battisti, D., 1999. Interannual (ENSO) and interdecadal (ENSO-like) variability in the Southern Hemisphere tropospheric circulation. - Journal of Climate 12: 2113-2123.
Garreaud, R., Barichivich, J, Christie, D.A. & Maldonado, A., 2008. Interannual variability of the coastal fog at Fray Jorge relict forests in semiarid Chile. - Journal of Geophysical Research 113: G04011.
Hesse, R. & Baade, J., 2007. Palaeoenvironmental changes in the Nazca-Palpa region, southern Peru--alternative interpretations of geoarchaeological evidence. - Archaeometry 49: 595-602.
Keefer, D.K., Moseley, M.E. & deFrance, S.D., 2003. A 38000-year record of floods and debris flows in the Ilo region of southern Peru and its relation to El Niño events and great earthquakes. - Palaeogeography, Palaeoclimatology, Palaeoecology 194: 41-77.
Mächtle, B., Unkel, I., Eitel, B., Kromer, B. & Schiegl, S., in press. Molluscs as evidence for a late Pleistocene and early Holocene humid period in the southern coastal desert of Peru (14.5⁰S) - Quartenary Research.
Vargas, G., Rutllant, J. & Ortlieb, L., 2006. ENSO tropical-extratropical climate teleconnections and mechanisms for Holocene debris flows along the hyperarid coast of western South America (17⁰-24⁰S). - Earth and Planetary Science Letters 249: 467-483.
Also in southern Peru snails may be found in the very arid coastal area.
This is a picture taken by Ralf Hesse near Nazca. A detailed shot reveals that here there are two forms present. The slender form resembles Bostryx hennahi (Gray, 1830), the stouter shells B. styliger (Beck, 1832).
It became interesting when I saw different photographs taken by him in the same area. These show that the latter species exhibits a transition to carinate forms; the latter resembles Bostryx reentsi (Philippi, 1851) known to occur slightly more southward near Chala.
This carination is hypothesized to be the result of ‘ecological stress’, in the case of the Chilean species by displacement through flooding or mud streams beyond the limits of their normal habitat. Indeed, there is reference in literature about climatic variability along the Chilean and southern Peruvian coast (Garreaud & Battisti, 1999; Vargas et al., 2006), due to the El Niño phenomenon.
Recently, studies have suggested that this mechanism also extended to the Nazca region during Pleistocene times (Eitel et al., 2005; Mächtle et al, in press). They hypothesize that a much more humid climate existed during the Pleistocene, with an increased aridification during the Holocene. Between 1000-1400 a semi-arid period would have occurred. The presence of loess in parts of the area on the flank of the Andes is an important argument in their papers. Radiocarbon dating of shells found amidst the loess dates this layer at ca. 10.000 yr BP. They postulate that the formation of the loess was influenced by monsoons crossing the Andes from Amazonia and leading to a higher precipitation.
Figure 3 from Mächtle et al. (in press), with the erroneous classification as Scutalus chiletensis granulatus Weyrauch; this is a species from N-Peru.
Hesse & Baade (2007) pointed out that an alternative explanation for the loess formation could be the fog vegetation occurring in coastal Peru and Chile (Garreaud et al., 2008). The occurrences of floods and debris flows has been recorded for the Ilo region in southern Peru (Keefer et al., 2003), but it may have also occurred in the Nazca region.
In conclusion, the occurrence of carinate shells with a transition to normal shell forms near Nazca is an interesting find. And although the evidence provided in literature points to floods and debris flows as a possible factor, more detailed research is needed to understand the mechanism of carination at play here.
References:
Eitel, B., Hecht, S., Mächtle, B., Schukraft, G., Kadereit, A., Wagner, G.A., Kromer, B., Unkel, I. & Rendel, M., 2005. Geoarchaeological evidence from desert loess in the Nazca-Palpa region, southern Peru: palaeoenvironmental changes and their impact on pre-Columbian cultures. - Archaeometry 47: 137-158.
Garreaud, R. & Battisti, D., 1999. Interannual (ENSO) and interdecadal (ENSO-like) variability in the Southern Hemisphere tropospheric circulation. - Journal of Climate 12: 2113-2123.
Garreaud, R., Barichivich, J, Christie, D.A. & Maldonado, A., 2008. Interannual variability of the coastal fog at Fray Jorge relict forests in semiarid Chile. - Journal of Geophysical Research 113: G04011.
Hesse, R. & Baade, J., 2007. Palaeoenvironmental changes in the Nazca-Palpa region, southern Peru--alternative interpretations of geoarchaeological evidence. - Archaeometry 49: 595-602.
Keefer, D.K., Moseley, M.E. & deFrance, S.D., 2003. A 38000-year record of floods and debris flows in the Ilo region of southern Peru and its relation to El Niño events and great earthquakes. - Palaeogeography, Palaeoclimatology, Palaeoecology 194: 41-77.
Mächtle, B., Unkel, I., Eitel, B., Kromer, B. & Schiegl, S., in press. Molluscs as evidence for a late Pleistocene and early Holocene humid period in the southern coastal desert of Peru (14.5⁰S) - Quartenary Research.
Vargas, G., Rutllant, J. & Ortlieb, L., 2006. ENSO tropical-extratropical climate teleconnections and mechanisms for Holocene debris flows along the hyperarid coast of western South America (17⁰-24⁰S). - Earth and Planetary Science Letters 249: 467-483.
Climate change and tepuis
29-06-2009 20:57
Conservationists may be alarmed (again), although it
doesn’t concern a charismatic or a flagship species.
It’s about the ecosystem of the
tepuis.
And, although the threat is not immediate, it is a
serious one.
Valentí Rull has written, alone or together with members of his research group, many papers of interest about the Guayana Shield (Pantepui). Recently, one more appeared dealing with the potential effects of climate change on the tepui ecosystem. By modeling the shift of the biotas due to temperature rises of 2 and 4 degrees, they calculated the effects on the vascular plants. Evidence is provided that up to 45% of Pantepui species may be endangered with extinction due to habitat loss before the end of the century, if the temperature rises with 4 degrees.
The bromeliads in which snails have been found are on the list of species involved. The ecological ties between plants and snails may turn out unfavorable for the snails, given the fact that they are only occurring on the upper part of the tepuis and these communities are bound to be affected. Due to the flatness of these mountaintops there will be no escape...
Reference:
Nogué, S., Rull, V. & Vegas-Vilarrúbia, T., 2009. Modeling biodiversity loss by global warming on Pantepui, northern South America: projecting upward migration and potential habitat loss. - Climatic Change 94: 77-85.
Valentí Rull has written, alone or together with members of his research group, many papers of interest about the Guayana Shield (Pantepui). Recently, one more appeared dealing with the potential effects of climate change on the tepui ecosystem. By modeling the shift of the biotas due to temperature rises of 2 and 4 degrees, they calculated the effects on the vascular plants. Evidence is provided that up to 45% of Pantepui species may be endangered with extinction due to habitat loss before the end of the century, if the temperature rises with 4 degrees.
The bromeliads in which snails have been found are on the list of species involved. The ecological ties between plants and snails may turn out unfavorable for the snails, given the fact that they are only occurring on the upper part of the tepuis and these communities are bound to be affected. Due to the flatness of these mountaintops there will be no escape...
Reference:
Nogué, S., Rull, V. & Vegas-Vilarrúbia, T., 2009. Modeling biodiversity loss by global warming on Pantepui, northern South America: projecting upward migration and potential habitat loss. - Climatic Change 94: 77-85.
Going North? At snail's pace
04-11-2008 20:50
Science journalists usually have a good sense of
appealing news. This week a brief article in my
newspaper draw my attention to an upcoming paper by
Devictor et al. in the Proceedings of the Royal
Society B, december 2008. The caption is: French
birds breed more northerly but the climate [change]
is faster.
We have read more often about the changes in the fauna and flora due to the warming of the climate of course. Some are good and (most) others are bad. So far I haven’t read much about snails; most is about plants, insects and birds. Anyone busy sorting out the effects on snails?
A quick search in Scholar shows that Devictor has a track record on the subject. Incidentally a precursor to the same paper can be found under the title “French birds lag behind climate warming”, already posted on 29 October 2007 in Nature Precedings. The basis of the paper is the Community Temperature Index, a measure calculated as the average of individual species temperature index (STI) per assemblage on a site. CTIs are then determined by the long term average temperature experienced by breeding birds over their (European) range. These can be calculated from the Worldclim database, taking the average temperature during the breeding season and coupling these data to spatial distribution data.
The effect of climate change on shifts in flora and fauna in the Neotropic/Nearctic region is not readily in the news here. But my guess would be that a similar phenomenon occurs in Mexico and the USA. Is this effect also noticeable in the ranges of land snails? Could it perhaps be measured analogous to the way briefly summarized for birds above?
Not sure if there any data exist on the occurrences of species assemblages of land snails in southern USA. I remember to have seen a map with grids somewhere, but don’t recall where. Anyway, if the snails go North they will surely lag behind the climate warming. At a snail’s pace...
We have read more often about the changes in the fauna and flora due to the warming of the climate of course. Some are good and (most) others are bad. So far I haven’t read much about snails; most is about plants, insects and birds. Anyone busy sorting out the effects on snails?
A quick search in Scholar shows that Devictor has a track record on the subject. Incidentally a precursor to the same paper can be found under the title “French birds lag behind climate warming”, already posted on 29 October 2007 in Nature Precedings. The basis of the paper is the Community Temperature Index, a measure calculated as the average of individual species temperature index (STI) per assemblage on a site. CTIs are then determined by the long term average temperature experienced by breeding birds over their (European) range. These can be calculated from the Worldclim database, taking the average temperature during the breeding season and coupling these data to spatial distribution data.
The effect of climate change on shifts in flora and fauna in the Neotropic/Nearctic region is not readily in the news here. But my guess would be that a similar phenomenon occurs in Mexico and the USA. Is this effect also noticeable in the ranges of land snails? Could it perhaps be measured analogous to the way briefly summarized for birds above?
Not sure if there any data exist on the occurrences of species assemblages of land snails in southern USA. I remember to have seen a map with grids somewhere, but don’t recall where. Anyway, if the snails go North they will surely lag behind the climate warming. At a snail’s pace...