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Efecto del cambio climtico en cuatro especies de Azteca en Monteverde, Puntarenas, Costa Rica
Effect of climate change on four species of Azteca in Monteverde, Puntarenas, Costa Rica
Digitized by MVI
There has been extensive, research in the Monteverde area that has shown that both the abundance and
range of lizards, amphibians, and birds have been affected global warming (Pounds (1999). Although
there have been studies showing changes in abundance of arctic and temperate invertebrates, there have
not been any studies that have shown invertebrate response to climate change in Monteverde. The four
species of Azteca ants (xanthochroa, constructor, coeruleipennis, and alfari) were collected along roads
in Monteverde and nearby Santa Elena and San Luis at elevations ranging from 700-1500m. The
altitudinal ranges from this study were compared to ranges obtained by Longino in 1985 to determine if
these four species have shifted upward in elevation (Longino 1989). A one way analysis of variance
compared the elevations of the four species to one another and found that all four were statistically
different in the elevations that they occupy except for A. xanthochroa and A. constructor which are both
high elevation species. This data agrees with previous research by Longino that has shown that these four
species occupy different altitudinal bands. A. coeruleipennis was shown to be a strictly low elevation
species and A. alfari occupies low to mid-elevations. When the mean values for elevation from this study
were compared with Longinos 1985 mean elevations using a one sample t-test A. xanthochroa and A.
constructor the results were significantly different (P = .0033 and P = .0342 respectively). The mean
values for A. alfari were not statistically significant (P = .1462) in the one sample t-test, but this is most
likely due to small size in comparison to Longinos findings. In conclusion three of the four species of
Azteca that were studied showed evidence of an upward shift in elevation. When interpreted in
conjunction with the previous studies on lizards, amphibians and birds, the upward shift in range of
Azteca spp. provides even more evidence that global warming is having a dramatic effect on altitudinal
distributions in Monteverde.
Ha habido una investigacin extensa en el rea de Monteverde que ha mostrado que la abundancia y gama de lagartijas, anfibios, y aves se han visto afectados por el calentamiento global (pounds 1999). Aunque se han realizado estudios que muestran los cambios en la abundancia de invertebrados rticos y templados, no se han realizado estudios que han demostrado la respuesta de los invertebrados al cambio climtico en Monteverde. Se recogieron las cuatro especies de hormigas Azteca (xanthochroa, constructor, coeruleipennis, y alfari) a lo largo de los caminos en Monteverde, cerca de Santa Elena y San Luis en altitudes que van desde los 700m-1500m. Los rangos de altitud de este estudio se compararon con los rangos obtenidos por Longino en 1985 para determinar si estas cuatro especies se han desplazado hacia arriba en elevacin (Longino 1989). Una forma de anlisis de variacin compar las elevaciones de las cuatro especies entre si y se encontr que los cuatro eran estadsticamente diferentes en las elevaciones que ellos ocupan aparte de A. xanthochroa y A. constructor que son ambas especies de alta elevacin. Estos datos concuerdan con investigaciones previas por Longino que han demostrado que estas cuatro especies ocupan diferentes bandas altitudinales. A. coeruleipennis ha demostrado ser una especie estrictamente de baja elevacin y A. alfari ocupa de bajas a medianas elevaciones. Cuando se compararon los valores medios de elevacin de este estudio con las elevaciones medias de Longino 1985 utilizando una muestra de una prueba t-test de A. xanthochroa y A. constructor, los resultados fueron significativamente diferentes (P = .0033 y P = .0342 respectivamente). Los valores medios de A. alfari no fueron estadsticamente significativas (P= .1462) en la muestra de t-test, pero esto es debido al pequeo tamao, lo ms probable en comparacin con los hallazgos de Longino. En conclusin, tres de las cuatro especies azteca que fueron estudiados mostraron evidencia de un desplazamiento hacia arriba en elevacin. Cuando se interpret en conjuncin con los estudios previos sobre lagartijas, anfibios y aves, del desplazamiento hacia arriba en el rango de azteca spp. ofrece an ms evidencia de que el calentamiento global est teniendo un efecto dramtico sobre las distribuciones altitudinales en Monteverde.
Text in English.
Climatic changes--Environmental aspects
Costa Rica--Puntarenas--Monteverde Zone--Monteverde
Cambios climticos--Aspectos ambientales
Costa Rica--Puntarenas--Zona de Monteverde--Monteverde
Tropical Ecology Fall 2003
Ecologa Tropical Otoo 2003
t Monteverde Institute : Tropical Ecology
Effect of climate change on four species of Azteca in Monteverde, Puntarenas, Costa Rica Paul Mazzei Department of Biology, Wofford College _____________________________________________________________________________________ Abstract There has been extensive, research in the Monteverde area that has shown that both the abundance and range of lizards, amphibians, and birds have been affected global warming (Pounds (1999). Although there have been studies showing changes in abundance of arcti c and temperate invertebrates, there have not been any studies that have shown invertebrate response to climate change in Monteverde. The four species of Azteca ants ( xanthochroa, constructor, coeruleipennis, and alfari ) were collected along roads in Monteverde and nearby Santa Elena and San Luis at elevations ranging from 700 1500m. The altitudinal ranges from this study were compared to ranges obtained by Longino in 1985 to determine if these four species have shifted u pward in elevation (Longino 1989). A one way analysis of variance compared the elevations of the four species to one another and found that all four were statistically different in the elevations that they occupy except for A. xanthochroa and A. constructo r which are both high elevation species. This data agrees with previous research by Longino that has shown that these four species occupy different altitudinal bands. A. coeruleipennis was shown to be a strictly low elevation species and A. alfari occupies low to mid elevations. When the mean values for elevation from this study test A. xanthochroa and A. constructor the results were significantly different (P = .0033 and P = .0342 respe ctively). The mean values for A. alfari were not statistically significant (P = .1462) in the one sample t test, but this is most Azteca that were stud ied showed evidence of an upward shift in elevation. When interpreted in conjunction with the previous studies on lizards, amphibians and birds, the upward shift in range of Azteca spp . provides even more evidence that global warming is having a dramatic e ffect on altitudinal distributions in Monteverde. Resumen Ha habido investigaciÃ³n extensa en el Ã¡rea de Monteverde que ha mostrado que la abundancia y gama de lagartos, los anfibios, y los pÃ¡jaros se han afectado warming global (pounds 1999). Aunque haya habido los estudios que muestran cambian de sobra de Ãrtico e invertebrados templados, no ha habido cualquiera estudia eso ha mostrado el invertebrado la respuesta al cambio del clima en Monteverde. La cuatro especies de hormigas de Azt eca ( xanthochroa, constructor , coeruleipennis, y alfari ) fueron reunidos por caminos en Monteverde y Santa Elena y en San Luis en las elevaciones que recorren de 700m 1500m. El altitudinal recorre de este estudio fueron comparados con las gamas obtenidas p or Longino en 1985 en determinar si estas cuatro especie ha cambiado hacia arriba en elevaciÃ³n (Longino 1989). Un anÃ¡lisis de la manera de variaciÃ³n comparÃ³ las elevaciones de la cuatro especie uno al otro y encontrÃ³ que todo cuatro eran estadÃsticamente d iferentes en las elevaciones que ellos ocupan aparte de A. xanthochroa y A. constructor que son ambos especie alta de elevaciÃ³n. Estos datos concuerdan con investigaciÃ³n previa por Longino que han mostrado que estas cuatro especies ocupa las bandas diferen tes de altitudinal. A. coeruleipennis se mostrÃ³ para ser una especie estrictamente baja de la elevaciÃ³n y A. alfari ocupa bajo a de elevaciones medias. Cuando los valores malos para la elevaciÃ³n de este estudio se compararon con
malas que utilizan una prueba de la muestra T. A. xanthochroa y A.constructor que los resultados eran apreciablemente diferentes (P = .0033 y P = .0342 respectivamente). Los valores malos para A. alfari no era estadÃsticamente significativo (P = .1462) en la una prueba de la muestra T, pero esto es muy probable debido a tamaÃ±o de la muestra pequeÃ±o en la comparaciÃ³n a Longino los hallazgos de s. En conclusiÃ³n tres de la cuatro especie de Azteca que se estudiaron la evidencia mostrada de un hacia arriba camb io en la elevaciÃ³n. Cuando interpreto en conjunciÃ³n con los estudios previos en lagartos, los anfibios y los pÃ¡jaros, el hacia arriba cambio en la gama de spp de Azteca. Proporciona aÃºn mÃ¡s evidencia que ese warming global tiene un efecto dramÃ¡ tico en dist ribuciones de altitudinal en Monteverde. Introduction While over the last 1000 years there has been a great deal of fluctuations in global Climate Change 2001). The temp erature of the earth has increased by 0.6Â°C in the last 100 years and this warming has clearly caused long term, large scale changes on populations of both plants and animals (Root et al. 2003). Very minute increases in temperature can have dramatic effect s, as seen when coral bleaching occurred because of 1.0Â°C increases in average summer temperatures (Walther et al. 2002). Climate changes can alter species interactions, reduce stability of communities and be the cause of shifts in biomes (Parmesan and Yoh e 2003). There have been numerous studies performed throughout the world that statistically correlate changes in climate with biological variation. The three major types of analysis of biological response to climate change are range shifts, phonological sh ifts, and distribution and abundance shifts (Parmesan and Yohe 2003). Being able to anticipate biological changes in response to warming is an important element in improving conservation management, and therefore the scientific community should increase it s understanding of the effects of global warming (Root invertebrates, lizards, amphibians, and birds. Invertebrate studies with butterflies in North America and Europe hav e shown upward shifts in range due to increased temperatures (Walther et al 2002). There have been studies that have shown increases in abundance of temperate species of aquatic invertebrates due to increases in temperature, while arctic species of aquatic invertebrates in the same area have shown decreases in abundance (Parmesan and Yohe 2003). Similar studies comparing lowland versus highland birds in the tropics have also shown variation in abundance (Parmesan and Yohe 2003). Specific examples of tropica l birds in the cloud forest of Monteverde that have shifted significantly upward in elevation include Golden crowned warblers, lesser greenlets and keel billed toucans (Pounds 1999). In addition to birds there has been extensive research proving that anole s and anurans have experienced decreases in abundance and variance in range implicating a broad response to climate change in Monteverde, Costa Rica (Pounds 1999). Despite the abundance of research on lizards, amphibians, and birds in response to global wa rming in Monteverde, there is virtually no information indicating if invertebrates have experienced any changes in range as a result of climate change. Monteverde is an ideal place to study the effects of global warming, especially range shifts because th ere is a high degree of altitudinal variance in a relatively small area. There are seven different live zones represented in Monteverde and its surrounding
areas according to Holdridge, which makes biological responses to climate changes readily apparent ( Nadkarni and Wheelwright 2000). A prime invertebrate candidate to be studied is ants in the subfamily Dolichoderinae, in particular Azteca spp (Holdobler and Wilson). The four species of Azteca in Monteverde have an obligate mutualism with two species of C ecropia obtusifolia and peltata (Longino 1997). However Azteca are habitat specific and do not have a pair wise relationship with Cecropia (Price 1991). Therefore a particular species of Azteca is not restricted to only one species of Cecropia . Because the obligate mutualism between Azteca and Cecropia is diffuse, the ants are not restricted to a certain elevation. Within Monteverde there are four species of Azteca found at different altitudinal bands (Longino 1989). In 1985, Azteca xanthochroa and Azteca constructor were high elevation species with mean ranges of 1180m and 1160m and Azteca coeruleipennis had a mean of 840m and is found at exclusively lower elevations. Azteca alfari had a mean of 910m and are considered a low to mid elevation sp ecies (Longino 1989). This is a study that compares the 1985 altitudinal trends in Monteverde to the present. This is an 18 year difference, thus there seems to a sufficient amount of time for these species to have responded to climate changes as found fo r similar amounts of time in Pounds 1999 studies on climate change. Because of an overall increase in temperature due to global warming, the altitudinal ranges of the four species of Azteca in Monteverde are shifting to higher elevations. Materials and Me thods Azteca ants were removed from Cecropia trees along roads in Monteverde, Puntarenas, Costa Rica and nearby Santa Elena and the San Luis Valley at an altitudinal range of 700 1500m from 21 October 2003 to 15 November 2003. The altitudes were found using Casio FTS 100 Forester altimeter. Workers were obtained by cutting leaves from the crown with a pole trimmer removing the ants from the leaf surface or the workers were taken directly the surface of the trunk. Saplings were destructively sampled usi ng a machete and in this case workers and queens were removed if they were present. Eighty total samples of ants were collected and in three of the trees two species of Azteca were found. Workers and queens were put into vials of alcohol after being remove d from the tree to be preserved for later identification. The specimens were then put on slides and in order to allow the alcohol to evaporate off so the ants would dry before being viewed under a dissecting scope. Drying was necessary because the presence of setae is important in the identification process, and these setae were more difficult to see while descriptions and photos of the four species on his website as well as the d escriptions Results Eighty Cecropia trees were sampled and 28 A. xanthochroa , 23 A. constructor , 19 A. coeruleipennis , and ten A. alfar i were found, in some cases finding two species in one tree. The maximum elevation for A. xanthochroa , A. constructor , A. coeruleipennis , and
A. alfari 1450m, 1430m, 980m, and 1310m respectively, and the minimum elevation were 1000m, 925m, 745m, and 780m (figure 1). A one way analysis of variance was performed comparing the elevations of each of the four species of ants to determine if they are found at A. xanthochroa and A. constructor were not statistically different (P = .4792, table 1). The comparisons of A. xanthochroa and A. alfari , A. xanthochroa and A. alfari , A. constructor and A. coeruleipennis , A. constructor and A. alfari , and A. coeruleipennis and A. alfari The mean values of elevation were also calculated in order to compare these valu test. The mean values and standard deviations in elevation for A. xanthochroa , A. constructor , A. coeruleipennis , and A. alfari were 1263m +/ 150m, 1235m +/ 167m, 840m +/ 65 m, and 997m +/ 168m respect ively (table 2). When the mean elevation of A. xanthochroa (1263m) from sample t test the result was statistically different (P = .0033). The results from the one sample t test comparing A. constructor the 2003 elevation (1235m) t o the 1985 elevation (1156m) were also statistically different (P = .0342). The mean values for elevation using a one sample t test comparing the mean A. coeruleipennis (836m in 1985 and 841m in 2003) and A. alfari (916m in 1985 and P = 1462 respectively). Discussion in a general sense. The altitudinal values indicate that A. xanthochroa and A. constructor are higher elevation species, A. alfari is a low mid elevation species, and A. coeruleipennis was found only at low elevations (fig. 1 and fig. 2). However the altitudinal trends from this study illustrate that the ranges Azteca spp , in Monteverde are moving up in elevation. A. xanthochroa , A. constructor , and A. alfari all appear to be shifting upward in elevation. The maximum and minimum values for these three species figure 1 and figure 2. The one sample t tests comparing the mean values in elevation between A. xanthochroa and A. constructor have moved up in elevation. The mean value for A. alfari was 992m in this study compared to 916m in the Longino results. While these values according to the one sample t test are not statistically different (P = .1462) this is most likely due to a smaller sample size of A. alfari in this study (n = 10, Mazzei compared to n = 27, Longino). Therefore it can be concluded that A. alfari is also showing evidence of an upward shift in range. Furthermore the minimum values increased by 30m, and the maximum values increased by 60m for A. alfari ( table 1). While only three of the four species studied showed signs of upward shifts in elevation, Parmesan and Gary Yohe (Parmesan and Yohe 2003). Instead, altitudinal r esponse to global warming looks to find a level of confidence by taking into account the general
trends that are seen (Parmesan and Yohe 2003). The evidence of an upward shift in Azteca spp . in Monteverde should be viewed in conjunction with the other evid ence of climate change as seen in anoles, amphibians and birds to show that climate change is affecting a wide range of biotic interactions in Monteverde. Another explanation as to why A. coeruleipennis did not show evidence of a global shift could be due to the specific altitudinal zone that it occupies. J. Alan Pounds (1999) found that variations in bird abundance related to climate change are dependent upon the life zones that the species occupy. These life zones are based on elevation, and therefore bi rds that occupy different altitudinal bands often exhibit different responses to climate change. Because A. coeruleipennis is a premontane moist forest species and the other three occupy the premontane wet forest life zones it is possible that there are di fferences in how each species responds to climate change (Nadkarni and Wheelwright 2000, Root 2003). The upward movement seen in Azteca ants in Monteverde is significant because it gives further supports the upward movements seen by birds in the area as r esult of increases in temperature (Pounds 1999). In addition this is the first example in Monteverde of climate change in a species with an obligate mutualism. Therefore it is possible that the upward movement of Azteca ants could be correlated to an altit udinal shift in Cecropia . Further studies could be done to determine if the change in range in Azteca is a result of an upward shift in its host plant. Although there has been extensive research in the Monteverde area correlating climate change with disruption of biological activity there is still more room for research on this theme. While there may be conflict across different species, taxon, or geograp hic region in regards to studies on climate, most contradicting data tend to diminish when higher numbers of species and systems are studied (Parmesan and Yohe 2003). Therefore more research should be done on different taxa regarding climate so that the co nclusions drawn can be more definitive. Furthermore while this study addressed the effect of global warming on invertebrates, it was only in relation to range shifts. There is still no research how phenology and species abundance in invertebrates in Montev erde are affected by changes in climate. By having a complete understanding of how global warming is influencing a wide array biotic interactions, conservation decisions can be made based upon evidence that is well supported instead of using the responses of a limited number of species or taxa. Acknowledgements I would like to thank Alan Masters for supporting me in this project and driving me into San Luis in search of the ever elusive Azteca . I also thank him for the use of his motorcycle even though I had a few brushes with death. I would like to thank Karen Masters for answering my questions even though she was not my advisor. Of course the always helpful and smart Alec Andrew Rodstrum and Matt Gasner who helped me out even when they did not want to. C what an amazing woman. I want to thank everyone on the CIEE staff who helped make this one the opportunity to come out here.
Literature cited Holdober, Bert, and Edward O. Wilson. 1990. The Ants . Harvard University Press, Cambridge. Intergovernmental Panel on Climate Change. 2001. Climate Change 2001: The Scientific Basis. Cambridge University Press. New York ( www.grida.no/climat/ipcc_tar ). Plant Mutualism: Azteca and Cecropia . Biotropica 21(2): 126 132. Longino, John 1997. www.evergreen.edu/Azteca . Masters, Karen, 2003, Tropical Diversity Reader and Lectures Outlines . (I could not find Original site in reader). Nadkarni, Nalini M. and N.T. Wheelwright. 2000. Monteverde: Ecology and Conservation of a Tropical Cloud Forest . Oxford University Press, New York. 42. l response to Climate Change on a Tropical Mountain. Nature 398 : 611 615. Nature 421 : 57 60. Walther, G ian Reto, Eric Post, Peter Convey, Annette Menzel, Camille Parmesan, Trevor J.C. Beebee, Jean Marc Fromentin, Ove Hoegh Guldberg and Franz Barlein. 2002. Nature 416: 389 395.