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La riqueza de especies y abundancia de las libelulas (Odonata) en diferentes alturas de Monteverde, Costa Rica
Species richness and abundance of dragonflies and damselflies (Odonata) at different elevations in Monteverde, Costa Rica
Dragonflies and damselflies (Odonata) are very sensitive to differences in environmental conditions such as
temperature, oxygen levels and amount of forest cover (Ramrez 2000). This study focuses on Odonata
species in Monteverde, Costa Rica within the Lower Montane Wet habitat. I hypothesized that variations
in altitude would influence Odonata biodiversity, abundance and species richness. I used a butterfly net to
collect Odonata samples at five different elevations located at between altitudes of 1425 m and 1525 m.
There was no significant correlation between altitude and species richness (r^2=0.3331; p=0.450185), H
(r^2=0.03221; p=0.188120), evenness (r^2=0.03221; p=0.188120), Odonata abundance (r^2=0.03221;
p=0.188120) and Brechmorhoga rapax abundance (r^2=0.1099; p=0.872889). A significant positive
correlation was found, however, between the abundance of Cora chirripa and altitude (r^2=0.3809;
R=0.974679; N=5; p=0.004818). This may indicate that Cora chirripa is more sensitive to environmental
factors determined by altitude than other Odonata species.
Las liblulas (Odonata) son muy sensibles a las diferencias en las condiciones ambientales tales como la temperatura, los niveles de oxgeno y la cantidad de cubierta forestal (Ramrez 2000). Este estudio se centra en la especies Odonata en Monteverde, Costa Rica.
Text in English.
Dragonflies--Species diversity--Costa Rica--Puntarenas--Monteverde Zone
Damselflies--Species diversity--Costa Rica--Puntarenas--Monteverde Zone
Liblulas--Diversidad de especies--Costa Rica--Puntarenas--Zona de Monteverde
Tropical Ecology 2008
Ecologa Tropical 2008
t Monteverde Institute : Tropical Ecology
Species richness and abundance of dragonflies and damselflies Odonata at different elevations in Monteverde, Costa Rica Christy Conley Department of Biology ABSTRACT Dragonflies and damselflies Odonata are very sensitive to differences in environm ental conditions such as temperature, oxygen levels and amount of forest cover Ramirez 2000. This study focuses on Odonata species in Monteverde, Costa Rica within the Lower Montane Wet habitat. I hypothesized that variations in altitude would influenc e Odonata biodiversity, abundance and species richness. I used a butterfly net to collect Odonata samples at five different elevations located at between altitudes of 1425 m and 1525 m. There was no significant correlation between altitude and species rich ness r^ Ã°2 =0.3331; p=0.450185, H r^2=0.03221; p=0.188120, evenness r^2=0.03221; p=0.188120, Odonata abundance r^2=0.03221; p=0.188120 and Brechmorhoga rapax abundance r^2=0.1099; p=0.872889. A significant positive correlation was found, however, between the abundance of Cora chirripa and altitude r^2=0.3809; R=0.974679; N=5; p=0.004818. This may indicate that Cora chirripa is more sensitive to environmental factors determined by altitude than other Odonata species. Resumen Odonata son muy sens ibles a diferencias en el medio ambiente. Este estudio investiga especies de Odonata en Monteverde, Costa Rica. PresumÃ que la diversidad, abundancia y nÃºmero de especies de Odonata. Use un red de mariposas para obtener individuos del orden Odonata a ci nco altitudes entre 1425 m and 1525 m. No hubo una correlaciÃ³n significativa entre altitud y el numÃ©ro de especies r^ Ã°2 =0.3331; p=0.450185 , H r^2=0.03221; p=0.188120 , equidad r^2=0.03221; p=0.188120 , la abundancia de Odonata r^2=0.03221; p=0.188120 y la abundancia de Brechmorhoga rapax r^2=0.1099; p=0.872889 . Existe una correlaciÃ³n significativa entre altitud y la abundancia de Cora chirripa . Este puede ser un indicio que Cora chirripa es mÃ¡s sensible a cambios en altitud que otros especies de Odonata. INTRODUCTION The order Odonata includes dragonflies and damselflies, aquatic insects that can be found around freshwater habitats. Odonates tend to be specialists and generally have narrow distributional ranges Kalkman et al. 2007 Odonata l arvae require very specific environmental conditions to survive. For example, they have a narrow range for temperature, oxygen levels, amount of forest cover, types of vegetation and water pollution. Some require very specific microhabitats such as leave s in riffles Ramirez 2000. As a result, Odonata distribution is usually determined by the very specific conditions under which their larvae survive Calvert 1908. Altitude is an important factor when considering the ideal habitat for a given species. Increased altitude, for example, means decreased temperatures. This could affect odonates because, although some species of larger dragonflies and damselflies are able to thermoregulate to some extent, smaller odonates are unable to do so effectively. T his inability is due to higher rates of convective heat loss in smaller odonates, as shown
by May 1976 in a study on the suborder Anisoptera. Therefore, it might be harder for smaller odonates to maintain an effective body temperature at cooler temperatu res, decreasing their range. Due to cool temperatures and other factors associated with higher altitudes, many odonates could have trouble surviving in such a habitat. Because Odonata larvae have such narrow ranges, they are generally vulnerable to distur bance and require habitat preservation RamÃrez 2000. In order to protect Odonata biodiversity, therefore, it is important to understand the sorts of habitats in which a majority of Odonata species survive. Several studies have shown that Odonata divers ity is greater at lower elevations. However, little research has been done on the order Odonata in the tropics in spite of the fact that more than half of the 4500 known species of Odonata can be found in this region Hamilton et al. 1989 . In particular, little research has been done on the distribution of Odonata in Cloud Forests, and little research has been done concerning Odonata along forest streams in general Ramirez 2000. This study focuses on Odonata in the Monteverde Cloud Forest. More specifi cally, I observed the effect of altitude on species richness and abundance of Odonata in forested streams in the Lower Montane Wet Forest. I also looked specifically at the effect of altitude on the abundance of the common damselfly species Cora chirripa and common dragonfly species Brechmorhoga rapax . I hypothesized that Odonata biodiversity, species richness and abundance would be influenced by altitude. I predicted that Odonata would display a greater abundance, biodiversity and species richness at lo wer altitudes than at higher altitudes. METHODS Study Sites I conducted my study at the Quebrada MÃ¡quina , a freshwater stream located in the Lower Montane Wet region of Monteverde, Costa Rica. As measured at an attitude of 1460, this region receives 25 19 mm of precipitation annually and has an average temperature of 18.5 degrees Celsius Clark 2000. I used an altimeter to select five points along the river at which I collected Odonata samples. Sampling sites were at elevations of 1425 m, 1505 m, 1510 m, 1525 m and 1535 m. For each site selected, I used a tape measure to mark a 20 meter stretch of river between which samples were collected, and I used stakes to indicate the boundaries. Procedures During trial 1, I began sampling at the site of highes t elevation 1535 m at 9:30 am. Here, I spent 30 minutes collecting dragonflies and damselflies with a butterfly net on both banks of the river, and I placed them in plastic containers in order to prevent re collecting and re counting the same individual s. When the thirty minutes was up, I recorded the number of captured individuals of each species. After recording data, I moved down the river to the next site at 1525 m and repeated the process. The second session started exactly a half hour after the end of the first session to allow time for recording data and for switching locations. I continued to move down the river and repeated the process at all elevations.
I kept one individual of each morphospecies and preserved it in a freezer so that it coul d later be identified. I used laminates to identify each species. If I could not identify a morphospecies with the laminates, I sent it to Eladio Cruz. The remaining Odonata were released after data collection. Sampling occurred on July 27 th , July 29 th , July 30 th , July 31 st and August 2 nd . I completed five trials, each on a different day. Each trial started at 9:30 am, and each day I started at a different elevation. For example, the first day I started at the site of 1535 m of elevation, the second d ay I started at the site of 1510 m of elevation, the third day I started at the site of 1525 m of elevation and so on. I always worked down the river, and once I reached the lowest elevation of 1425 m, I returned to the site of highest elevation 1535 m and continued to work my way down until all five sites have been visited. As a result, each site was visited at 9:30, 10:30, 11:30, 12:30 and 1:30 over the course of the five days. This ensured that results were not affected by time of day. I first deter mined species richness, H , evenness and abundance at each altitude. Then I used a Non Parametric Spearman Correlation analysis to determine whether or not each of these variables had a relationship with altitude. I also determined the abundance of commo n damselfly species Cora chirripa and common dragonfly species Brechmorhoga rapax . I ran a Non Parametric Spearman Correlation to determine the correlation between altitude and the abundance of both Cora chirripa and Brechmorhoga rapax. RESULTS Species collected included Cora chirripa, Brechmorhoga rapax, Argia underwoodi, species 4, species 5, Hetaerina majuscala and Argia varaiabilis . Species richness, H , evenness and abundance of Odonata varied across different altitudes. Only two individuals and one species were found at 1425 m Table 1. There was a non significant positive correlation between altitude and species richness Fig 1 and H Fig 2. There was a non significant negative correlation between altitude and evenness Fig 3. Finally, t here was a non significant positive correlation between altitude and Odonata abundance Fig 4. The two most common Odonata species were Cora chirripa , with a total of 21 individuals sampled, and Brechmorhoga rapax, with a total of 14 individuals sampled Table 2. There was a significant positive correlation between altitude and abundance of C. chirripa Fig 5. There was a non significant positive correlation between altitude and abundance of B. rapax . DISCUSSION My results show no correlation between altitude and overall species richness, H , evenness or abundance. Also, I found no significant correlation between altitude and abundance of B. rapax . Such results do not support the hypothesis that species richness, biodiversity and abundance would be influenced by altitude. This could imply that the majority of Odonata species, including Brechmorhoga rapax, are not sensitive to small differences in altitude. Changes in temperature, dissolved oxygen content and any other environmental factor associate d with altitude were probably too small to have a
significant impact on odonate distribution. Therefore, future studies should test the effect of altitude over a larger range, as this might demonstrate a more significant correlation between altitude and s pecies richness, biodiversity and abundance. My results could also be due to a small sample size or collection period. Were this study to be repeated, a larger sample size or longer collection period should be used. The site at 1425 m showed unusually low abundance and species richness. This could be because it was located next to the Hotel Belmar, a source of disturbance. As Odonata do not respond well to disturbance Ramirez 2000, the additional factor of disturbance may have skewed results. In or der to control for additional factors such as disturbance, the same experiment should be conducted on a different river or at more sampling sites along the Quebrada MÃ¡quina . I did find that C. chirripa was more common at higher altitudes. Such results cou ld imply that C. chirripa is more sensitive to slight variations in altitude than other species of Odonata and tend to do better at higher elevations. For example, they could respond better to the higher oxygen levels found at the source of the river. As one study comparing abundance of Odonata in different rivers concluded, rivers with higher levels of dissolved oxygen tend to facilitate greater abundance of odonates than those with lower levels of dissolved oxygen Salmah et al. 2006. Cora Chirripa s greater abundance at higher altitudes, therefore, could be in response to higher oxygen levels found at river sources. In order to protect this species, therefore, measures should be made to protect source habitats. For example, the addition of phosphorus or nitrogen into a system can increase eutrophication, thereby depleting dissolved oxygen within a water system Carpenter et al. 1998. Such effects could be avoided by ensuring that increased soil or fertilizer runoff does not occur near the river sour ces. AKNOWLEDGEMENTS I would like to thank Tania ChavarrÃa for overseeing my research. I would like to thank Karen Masters, Alan Masters, Pablo Allen Monge and JosÃ© Carlos CalderÃ³n for additional assistance with my research. I would like to thank CIEE for providing me with the research materials. I would like to thank Eladio Cruz for helping me to identify Odonata species. Finally, I would like to thank the EstaciÃ³n BiolÃ³gica de Monteverde for allowing me to conduct research on their property. LITER ATURE CITED Carpenter, S.R., N.R. Caraco, D.L. Correll, R.W. Howarth, A.N. Sharpley and V.H. Smith. 1998. Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological Applications . 83: 559 568. Clark, K. L., R. O. Lawton and P. R . Butler. The Physical Environment In: Monteverde: Ecology and Conservation of a Tropical Cloud Forest , Nalini M. Nadkarni and Nathaniel T. Wheelwright, eds. Oxford University Press, New York, NY, pp 15 38.
Hamilton, L. D. and R. D. Montgomerie. 1989 . Population demography and sex ratio in a neotropical damselfly Odonata: Coenagrionidae in Costa Rica. Journal of Tropical Ecology . 5: 159 171. Kalkman, V, V. Clausnitzer, K. Dijkstra, A. Orr, D. Paulson and J. Tol. 2007. Global diversity of drago nflies Odonata in freshwater. Hydrobiologia . 595: 351 363. May, M. L. 1976. Thermoregulation and adaptation to temperature in dragonflies Odonata Anisoptera. Ecological Monographs . 46: 1 32. Calvert, P. P. 1908. The composition and ecological relations of the Odonate fauna of Mexico and Central America. Proceedings of the Academy of Natural Sciences of Philadelphia. 603: 460 491. RamÃrez, A. 2000. Dragonflies and Damselflies of Costa Rican Cloud Forests In: Monteverde: Ecology and Cons ervation of a Tropical Cloud Forest , Nalini M. Nadkarni and Nathaniel T. Wheelwright, eds. Oxford University Press, New York, NY, pp 97. Salmah, M.D., R. Che, S. W. Tribuana and A. A. Hassan. 2006. The population of Odonata dragonflies in small tropi cal rivers with reference to asynchronous growth patterns. Aquatic Insects . 28: 195 209.
Table 1. Species richness, H , evenness and abundance of Odonata varied with altitude. Site Altitude S H E # abundance 1 1425 1 0.25 1 2 2 1505 3 0.64 0.58 5 3 1510 6 1.7 0.95 23 4 1525 3 0.76 0.69 7 5 1535 3 0.58 0.53 17 Table 2. The abundance of Cora chirripa and Brechmorhoga rapax differed with altitude. Altitude 1505 1510 1525 1535 Species 1 0 3 4 14 Species 2 3 8 2 1 0 1 2 3 4 5 6 7 1400 1420 1440 1460 1480 1500 1520 1540 1560 Altitude Number of Species Fig ure 1. Relationship between Odonata species richness and altitude. I did not find a significant relationship r^ Ã°2 =0.3331; p=0.450185.
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 1400 1420 1440 1460 1480 1500 1520 1540 1560 Altitude H' Figure 2. Relationship between H and altitude. I did not find a significant relationship r^2=0.1841; p=0.62. 0 0.2 0.4 0.6 0.8 1 1.2 1400 1420 1440 1460 1480 1500 1520 1540 1560 Altitude Evenness Figure 3. Relationship between Odonata evenness and altitude. I did not find a significant relationship r^2=0.5153; p=0.188120.
0 5 10 15 20 25 1400 1420 1440 1460 1480 1500 1520 1540 1560 Altitude Number of Individuals Figure 4. Relationship between Odonata abundan ce and altitude. I did not find a significant relationship r^2=0.03221; p=0.188120.
-4 -2 0 2 4 6 8 10 12 14 16 1400 1420 1440 1460 1480 1500 1520 1540 1560 Altitude Number of Individuals Figure 5. Relationship between the abundance of Cora chirripa and altitude. I did find a significant relationship r^2=0.3 809; R=0.974679; N=5; p=0.004818. 0 1 2 3 4 5 6 7 8 9 1400 1420 1440 1460 1480 1500 1520 1540 1560 Altitude Number of Individuals Figure 6. Relationship between altitude and the abundance of Brechmorhoga rapax . I did not find a significant relationship r^2=0.1099; p=0.872889.