xml version 1.0 encoding UTF-8 standalone no
record xmlns http:www.loc.govMARC21slim xmlns:xlink http:www.w3.org1999xlink xmlns:xsi http:www.w3.org2001XMLSchema-instance
leader 00000nas 2200000Ka 4500
controlfield tag 008 000000c19749999pautr p s 0 0eng d
datafield ind1 8 ind2 024
subfield code a M39-00031
Cambio de rango en Cecropia y azteca: los efectos del cambio climtico sobre los socios mutualistas en Monteverde, Costa Rica
Range change in Cecropia and Azteca: the effects of climate change on mutualistic partners in Monteverde, Costa Rica
The effects of climate change on the fauna of the Monteverde area has been well documented for vertebrate taxa such as birds, anurans, Norops spp, (Pounds 1999) and bats (LaVal 2004), but like the rest of the world little work has been done on the effects of climate change on invertebrates. This study examines the altitudinal ranges of the four species of Azteca and the three species of Cecropia living between 1500 and 700m in an area from Monteverde-Cerro Plano to San Luis. The current ranges of species are compared to elevations from a 1985 survey by John Longino (Longino 1989) and a 2003 survey by Mazzei (2003). In the last 23 years two species, A. xanthochroa, and A. alfari, are shown to have moved significantly up slope with a change in mean elevation of 103m, and 100m (P= .0018, and .0348). A. constructor shows no evidence for upslope movement but it increased its relative population size threefold over that reported by Longino (1989). The lowermost Azteca, A. coeruleipennis, has not shifted with climate change but its distribution may be restricted by the range of C. peltata. The two ant-housing Cecropia species did not have significant changes in means, but the upper of the two, C.obtusifolia, did show an extension of its range upslope as well as an increase in hybrids between it and the uppermost non-ant-housing species C. angustifolia. These data are unique in showing the effect of climate change on invertebrate populations. Although the impact of climate change on invertebrates throughout the world has been poorly studied, this study suggests that they can be heavily impacted by climate change.
Existen documentos sobre los efectos del cambio climtico en los animales de la zona de Monteverde especialmente los vertebrados como las aves, las ranas, Norops spp, (Pounds 1999) y los murcilagos (LaVal 2004), pero al igual que el resto del mundo hay pocos trabajos que se han hecho sobre los efectos del cambio climtico en los invertebrados. Este estudio examina la distribucin altitudinal de las cuatro especies de azteca y las tres especies de Cecropia que viven entre los 1500 y 700 metros en una area desde Monteverde-Cerro Plano hasta San Luis.
Text in English.
Plant species diversity--Costa Rica--Puntarenas--Monteverde Zone
Species diversity--Costa Rica--Puntarenas--Monteverde Zone
Azteca (Insects)--Climatic factors
Cloud forest ecology--Costa Rica
Diversidad de especies de plantas--Costa Rica--Puntarenas--Zona de Monteverde
Diversidad de especies--Costa Rica--Puntarenas--Zona de Monteverde
Ecologa del bosque nuboso--Costa Rica
Tropical Ecology 2008
Ecologa Tropical 2008
t Monteverde Institute : Tropical Ecology
1 Range change in Cecropia and Azteca : the effects of climate change on mutualistic partners in Monteverde, Costa Rica Garrison Loope Department of Geology, Oberlin College Abstract The effects of climate change on the fauna of the Monteverde area has been well documented for vertebrate taxa such as birds, anurans, Norops spp, Pounds 1999 and bats LaVal 2004, but like the rest of the world little work has been done on the effects of climate change on invertebrates. This study examines the altitudinal ranges of the four species of Azteca and the three species of Cecropia living between 1500 and 700m in an area from Monteverde Cerro Plano to San Luis. The current ranges of species are compared to elevations from a 1985 survey by John Longino Longino 1989 and a 2003 survey by Mazzei 2003. In the last 23 years two species, A. xanthochroa, and A. alfari, are shown to have moved significantly up slope with a change in mean elevatio n of 103m, and 100m P = .0018, and .0348. A. constructor shows no evidence for upslope movement but it increased its relative population size threefold over that reported by Longino 1989. The lowermost Azteca , A. coeruleipennis , has not shifted with climate change but its distribution may be restricted by the range of C. peltata. The two ant housing Cecropia species did not have significant changes in means, but the upper of the two, C. obtusifolia, did show an extension of its range upslope as well as an increase in hybrids between it and the uppermost non ant housing species C. angustifolia. These data are unique in showing the effect of climate change on invertebrate populations. Although the impact of climate change on inve rtebrates throughout the world has been poorly studied, this study suggests that they can be heavily impacted by climate change. Resumen Los efectos del cambio climÃ¡tico en los animal e s de la regiÃ³n de Monteverde estÃ¡ bien estudiado para los vertebrado s como aves, ranas, Norops spp, Pounds 1999 y mu rciÃ©lagos LaVal 2004, pero como en todo el mundo hay pocos trabajos sobre los efectos del cambio climÃ¡tico en invertebrados. Este estudio busca los alcances de altitud de cuatro especies de Azteca y tres espec i es de Cecropia que viven entre 1500 y 700m en un Ã¡rea de Monteverde Cerro Plano a San Luis. Comparo los alcanc es actuales de las especies a la s altitudes con una inspecciÃ³n por John Longino en 1985 Longino 1989 y un a inspecciÃ³n por Mazzei 2003. En los veintitrÃ©s aÃ±os pasados dos especies , A. xanthochroa y A. alfari , se movieron hacia arriba con cambios en altitud de 103m y 100m P=.0018, y .0348. A. constructor no se moviÃ³ hacia arriba pero hubo un aumento relativo en la poblaciÃ³n de t res veces desde el reportaje de Longino 1989. El Azteca de mÃ¡s baja distribuciÃ³n , A. coeruleipennis, no he cambiado su alcance pero es posible que haya una conexiÃ³n con el alcance de C. peltata que restringe el alcance de A. coeruleipennis . La s dos esp ec i es de Cecropia que tienen hormigas no cambiaron sus altitudes medias, pero la especie mÃ¡s alta de los dos, C. obtusifolia , aumentÃ³ su lÃmite superior, tambiÃ©n hubo mÃ¡s hÃbridos entre este y C. angustifolia, un Ã¡rbol que no contiene hormigas. Esta infor maciÃ³n es Ãºnica por quÃ© es evidencia de un efecto del cambio climÃ¡tico en poblaciones de invertebrados . Aunque no hay mucha informaciÃ³n sobre el impacto del cambio climÃ¡tico en invertebrados, este estudio sugiere que el cambio climÃ¡tico tiene mucho impact o en los invertebrados.
2 Introduction It is now well established that the average global temperature has been increasing over the last 100 years IPCC 4 th Assessment Report, 2007. Global temperatures raised an average of 0.74Âº C in the last century, which makes the last 50 years the warmest 50 year period since 1300. There has been heterogeneity in climate change, in that some areas have been impacted more than others. The areas with the most warming tend to be polar and temperate IPCC, 2007. The tropics have experienced relatively little warming, but high levels of climatic specificity in tropical species Ghalambor et al. 2006 may make them more vulnerable to climate change. Recent climate change has been shown to have far reaching biological effects including shifts in ranges upslope or to higher latitudes, destabilization of ecosystems, and changes in phenology, such as the timing of migrations, breeding, flowering, and length of the growing season Walther et al. 2002. Pounds et al. 1999 linked elevated sea surface temperatures to drying in the cloud forest at Monteverde, Costa Rica by showing that the zone with temperatures critical for cloud formation raises with rising sea surface temperatures. Monteverde is an ideal place to study shifts in range because it has experienced perceived drying as well as increased seasonality and includes seven Holdridge Life Zones in a relatively small area Pounds et al. 199 9. In Monteverde climate change has been implicated in population declines in Norops spp and anurans as well as the up slope migration of many avian species Pounds et al. 1999 as well as several species of bats LaVal 2004. While many of these specie s are important pollinators and dispersers, little work has been done on the impact of climate change on interspecies relationships. The relationship between Azteca and Cecropia is the most conspicuous ant plant relationship in the Neotropics Longino 1989 , 1991a and b. Cecropia spp are pioneer trees common in pastures and along roads throughout the neotropics. Janzen 1969 showed that the relationship was mutualistic; Cecropia provide domatia in their hollow internodes and carbohydrates in their MÃ¼ller ian bodies, while Azteca protect Cecropia from herbivery and remove climbers Longino 1991a. In the Monteverde area there are three species of Cecropia and four species of Azteca , all restricted to narrow altitudinal bands Longino 1989. Although all f our species of Azteca are obligate Cecropia ants, one species of Cecropia never have ant partners and the other two are facultative ant partners but almost always contain colonies of Azteca Longino 1989. Although the altitudinal distribution between indi vidual species of Azteca and Cecropia are correlated, none have species specific partners and all species of Azteca were able to inhabit all species of ant Cecropia in controlled experiments Longino 1989. Past studies on Cecropia and Azteca in Monteve rde suggest that climate change is having a complex effect on both genera. Mazzei 2003 showed that three of the four species of Azteca in Monteverde had moved up slope since 1985. Cernac 2005 found that since 1985 the average range of C. obtusifolia moved up 73.8m into the range of C. angustifolia formerly C. polyphlebia enlarging the zone of hybridization between the species. This report examines Cecropia and Azteca along an altitudinal and moisture gradient from 700 1500m. I compare my data to h istoric ranges from 1985 Longino 1989 on both Azteca and Cecropia and 2003 Mazzei on Azteca . My time span of 23 years is comparable to studies done by Pounds 1999 and should be sufficient for fast
3 growing pioneer species and their mutualistic partne rs to show adjustment in range to a change in climate. Materials and Methods I collected samples of Azteca and Cecropia over an approximately 9km transect from 720 1610m along roads and trails from La EstaciÃ³n BiolÃ³gica de Monteverde through the Monteverde Cerro Plano area, down through the San Luis Valley, ending just below the town of San Luis. I attempted to collect sam ples from at least 15 trees in each 100m segment of my range in order to keep an even distribution. This study covers the same area sampled by Longino 1989 and Mazzei 2003 which should facilitate comparisons. I collected Azteca by using a long tree t rimmer to cut leaves . I collected four to 8 ants from leaves or trunks using an aspirator and placed them in vials with alcohol for later identification under a microscope. For identification I used photos and descriptions found on John Longino s website http://academic.evergreen.edu/ projects/ants/ and in Longino 1991a and b. Ants were identified using characteristics such as placement and length of setae, color, and shape and height of petiole. I sampled every tree that I could reach with the tree trimmer except for trees less than 2m tall because I found that they only rarely contained ants. I counted the secondary veins on the longest lobe of four leaves from each Cecropia sp in order to identify the species. I considered Cecropia with a mean nu mber of secondary veins less than 25 and short inflorescences as C. peltata , trees with between 25 and 35 secondary veins, long inflorescences, and ants as C. obtusifolia , trees with over 35 secondary veins, short inflorescences, and no ants as C. angustif olia , and trees displaying some characters of both C. obtusifolia and C. angustifolia as hybrids. This system was developed using information from Longino s website. For each tree in the field I recorded the number of secondary veins, sample number for an t vial, diameter at breast height, and elevation using a Casio Protrek Twin Sensor Altimeter. Results I sampled a total of 138 Cecropia trees. Of the trees sampled a total of 114 had Azteca and two trees had two species of Azteca . C. peltata were common in the lower elevations up to 900m, C. obtusifolia was present throughout the transect but was most common from 1000 to 1400m, C. angustifolia was common above 1350m although occasionally present at lower elevations, and hybrids were scattered between 900 and 1610m but were most common above 1350m figure 1. A. xanthochroa was found to be a high elevation species common from 1050 to 1450m, A. constructor was the most common and widespread species representing 44.8% of total Azteca population sampled Tab le 1 and was most common from 950 to 1350m, A. alfari was the least common species and occurred scattered across a range from 1280m all the way to the lower limit of the study, and A. coeruleipennis was the lowest species and was common up to 900m but qui ckly disappeared above 900m figure 1. Figure 2 shows the changes in mean elevation from 1985 Longino 1989 to 2003 Mazzei to 2008. It shows that i n 23 years two species, A. xanthochroa, and A. alfari, moved significantly up slope with a change in mean elevation of 103m, and 100m one -
4 variable t test, P = .0018, and .035. A. constructor, C. obtusifolia, and C. angustifolia have not moved significantly with only a change in means of 9m, 39m and 25m P= 0.738, 0.190, 0.264 and A. coeruleipennis has moved down significantly with a change in mean of 43m since 1985 P= .033. Each species of Azteca occupied every species of Cecropia in its range except C. angustifolia , a non ant species, and Chi 2 goo dness of fit tests showed that no species of ant had a preference for a specific species of tree in its range X 2 , P; A. coeruleipennis = 0.561, 0.454, A. alfari = .018, 0.892, A. constructor = 0.385, 0.535. It was also noted that A. constructor increased greatly in its relative abundance from 15.1% in 1989 to 28.8% in 2003 to 44.8% in 2008 table 1. Species Ranges 2008 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 A. alfari A. coeruleipennis A. constructor A. xanthochroa C. peltata C. obtusifolia Hybrid Elevation m Figure 1. shows the 2008 distribution of the four species of Azteca and the two species of ant housing Cecropia in the Monteverde area. Mean, standard deviation and range are shown for each species. For A. coeruleipennis and C. peltata the lowest samples are less than one standard deviation from the mean because only the upper part of the ranges are in the study area .
5 Species Mean Elevation Comparisons 700 800 900 1000 1100 1200 1300 1400 A. xanthochroa A. constrctor A. coeruleipennis A. alfari C. obtusifolia C. peltata Elevation m 1985 2003 2008 Figure 2. compares the mean elevations for all species over 23 years using data from this study, Longino 1989, and Mazzei 2003. Table 1. Elevation data from 2008 Loope, 2003 Mazzei, and 1985 Longino 1989 for all species of Azteca and ant housing Cecropia in the Monteverde area. Loope 2008 Mean Max Min n % total A. xanthochroa 1275 1450 950 27 23.3 A. constrctor 1147 1450 815 52 44.8 A. coeruleipennis 793 975 720 22 19.0 A. alfari 1016 1280 725 15 12.9 C. obtusifolia 1179 1450 725 60 C. peltata 835 1135 720 31 Mazzei 2003 Mean Max Min n % total A. xanthochroa 1263 1450 1000 28 35.0 A. constrctor 1235 1430 925 23 28.8 A. coeruleipennis 840 980 745 10 12.5 A. alfari 997 1310 780 19 23.8 Longino 1985 Mean Max Min n % total A. xanthochroa 1172 1380 860 32 34.4 A. constrctor 1156 1400 860 14 15.1 A. coeruleipennis 836 940 730 20 21.5 A. alfari 916 1240 750 27 29.0 C. obtusifolia 1140 1400 770 57 C. peltata 860 1250 730 40
6 Discussion Azteca and Cecropia spp. in my survey follow the same general pattern of relative altitudinal preferences as in the past Longino, 1989; Mazzei, 2003. A. xanthochroa and A. constructor are still largely high elevation species, A. coeruleipennis is still strictly low eleva tion and A. alfari is still a low to mid elevation species. C. peltata still is found in the lowest driest areas and C . angustifolia still dominates in the highest elevations, and grades continuously into C. obtusifolia , which is nearly ubiquitous across the study area. In comparison with 1985 I found that A. xanthochroa and A. alfari had shifted their altitudinal distribution up slope significantly. This agrees with Mazzei 2003 although he could not statistically show that A. alfari had moved up bec ause of his small sample size n= 10. A constructor did not show an upslope shift, however. The failure of A. constructor to shift upslope with perceived drying can be explained by its broad tolerance for climate. Of all the Azteca present in the stud y area A. constructor is the only one that is know to thrive in both dry and wet forests Longino 1991b. Also, although its mean elevation has not changed, A. constructor has become much more widespread and has increased its relative abundance by nearly three times in 23 years Table 1. This could represent selection for generalist species in response to a more variable and more seasonal climate. Mazzei found that A. constructor had moved up significantly which is in direct opposition to my data. It i s not that Mazzei found more A. constructor at higher elevations but that he did not find it commonly between 850 and 1100m. It is possible that this is due to Mazzei s smaller sample size, but also he does not report the evenness of his sampling. It is possible that because of the particular geographical layout of the study area Mazzei collected more samples from 1200 1400m than from 900 1100m thus skewing his results. Access to areas from 1300 to 1400m is very easy because of the large relatively flat area at this altitude. From 1200 to 900m the slopes are steep so the sampling area is likely smaller and the roads fewer. This study showed that A. coeruleipennis actually moved down slope since 1985 but this is most likely an artifact of my sampling o f lower elevations. I sampled six trees with A. coeruleipennis below Longino s lowest site 730m. Because A. coeruleipennis is found down to the coast, more samples at lower elevations would decrease species mean elevation. Mazzei 2003 agrees that A. c oeruleipennis has not moved up in elevation since 1985 and his lowest sample was even higher than Longino s. A. coeruleipennis like its cousins A. xanthochroa and A. alfari is a climate specialist so it would be expected to be affected by climate change. It is also possible that climate change is having different effects at different altitudes. The higher area where the upper three species live has experienced a reduction of the windy misty season due to a decreased frequency of days cool enough to cond ense moisture into mist Pounds 1999. This increase in seasonality and consecutive dry days has been implicated in many range shifts in the Monteverde area. The lower premontane moist forest that A. coeruleipennis inhabits never experienced seasonal mist inputs so is unlikely to feel the effect of Pound s rising cloudbank hypothesis. It is also possible that A. coeruleipennis is not only a dry forest specialist, but also a Cecropia specialist. Its range nearly always mirrors the range of C. peltata . Although it is known to inhabit other species of Cecropia, it nearly always nests in C. peltata Longino 1991b. This study shows that A. coeruleipennis has no preference for C.
7 peltata but even if they do not preferentially select C. peltata , species specific adaptations could allow A. coeruliepennis to out compete other species of Azteca in forests dominated by C. peltata. Even though C peltata is present up to 1100m it is only dominant up to about 900m, which is the upper limit of the range of A. c oeruleipennis . If indeed A. coeruleipennis is linked with C. peltata then because C. peltata shows no sign of moving upslope A. coeruleipennis is restricted to the lower elevations. Neither species of ant housing Cecropia have showed significant shifts in mean ranges, possibly because they have longer generation times or are less well dispersed than ants. However, C. obtusifolia is expanding its range upslope into the range of C. angustifolia, which is creating a larger hybrid zone. This is happening f aster than the lower part of range is retreating upslope, which leaves little change in the mean elevation. This could be due to a lag created by long lived individuals in the lower part of the range. The mutualism between Azteca and Cecropia causes a ch ange in one partner to affect the other. The range changes, population expansions, and increases in hybrids are likely to have complex affects on the fitness of Azteca and Cecropia . For instance Scalley 1993 showed that C. angustifolia produces more to xic secondary compounds to deter herbivores. This means that the hybrid zone has a mix of different herbivore defenses. Expansion of the hybridization zone is likely to have a detrimental effect on the plants ability to deter herbivores. Ants that start to colonize these upper hybrids will be exposed to different selection pressures than their lower relatives which may produce divergence. Also, the four species of Azteca have different levels of aggression Longino 1991a. If A. alfari increases its ra nge it could increase herbivery on the trees it inhabits because it is much less aggressive than the ants it would replace. More research is needed find the true effects of climate change on this interesting ant plant mutualism. In conclusion it appears that climate change is having a complex affect on Azteca and Cecropia populations in the Monteverde area. Azteca seem to be more affected than Cecropia possibly because they have shorter generations, are better dispersed, or are more sensitive than their hosts. Climate change appears to be affecting ranges of Azteca and Cecropia separately with the possible exception of the A. coeruleipennis C. peltata interaction. These results along with Mazzei 2003 support the findings of Pounds 1999 and add art hropods, whose responses to climate change have long been neglected, to the growing list of taxa known to be affected by climate change in the Monteverde area. If climate change has an effect on arthropods in Monteverde, it is likely that arthropods are b eing affected throughout the world. More work on climate change and arthropods is clearly needed as they are the most species rich taxon on the planet, and a threat to them is an assault on biodiversity itself. Acknowledgments I would like to thank Alan and Karen Masters for answering my questions at any time of day, as well as all the kind citizens of the San Luis Valley for letting me collect ants on their property and giving me rides up the hill when they thought I was going to die on the road.
8 Literature Cited Cernac, Joy. 2005. Altitudinal Range Change in a Pacific Cecropia Azteca Mutualism CIEE Fall. Monteverde, Costa Rica. Ghalambor, C.K., Huey, R.B., Martin, P.R., Tewksbury, J.J., and Wang, G. 2006. Are mountain passes higher in the tropics? Janzen s hypothesis revisited Integr. Comp. Biol. 46, 5 17. Intergovernmental Panel on Climate Change. 2007. Climate Change Assessment Report 2007: the scientific basis Janzen, D. H. 1969. Alleopathy by Myrmecophytes: the ant Azteca as an alleopathic agent of Cecropia Ecology 50: 147 150. LaVal, Richard. 2004. Impact of Global Warming and Locally Changing Climate on Tropical Cloud Forest Bats Journal of Mammalogy 852: 237 244. Longino, John. 1989. Geographical Variation and Community Structure in an Ant Plant Mutualism: Azteca and Cecropia in Costa Rica Biotropica 212: 126 132. Longino, John. 1991a. Azteca ants in Cecropia Trees: Taxonomy, Colony Structure, and Behaviour Pages 271 288 in C. Huxley and D. Cutler, editors. Ant plant interactions. Oxford University Press, Oxford, U.K. Longino, John. 1991b. Taxonomy of Cecropia inhabiting Azteca ants Journal of Natural History 25, 1571 1602. Longino, John. 2000. Myrmecoph ytes in N. M. Nadkarni and N. T. Wheelwright Editors. Monteverde: ecology and conservation of a tropical cloud forest. 291 293. Oxford University Press, New York, New York. Longino, John. 2007. http://academic.evergreen.edu/projects/ants/ Mazzei, Paul. 2003. Effect of Climate Change on Four Species of Azteca in Monteverde, Puntarenas, Costa Rica CIEE Fall. Monteverde, Costa Rica. Pounds, J.A., M. P. L. Fogden, and J. H. Campbell. 1999. Biological Responces to Climate Change on a Tropica l Mountain Nature 398 : 611 615. Scalley, Michelle. 2003. Defence Tradeoffs and its effects on herbivores in two species of Cecropia EAP Fall. Monteverde, Costa Rica. Walther, G., E. Post, A. Menzel, C. Parmesan, T. J. C. Beebee, J. Fromentin, O. Hoe gh Guldberg, and F. Bairlein. 2002. Ecological Responses to Recent Climate Change Nature 416: 389 395.