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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 sens itive to differences in environmental conditions su ch as temperature, oxygen levels and amount of forest cov er (Ramrez 2000). This study focuses on Odonata species in Monteverde, Costa Rica within the Lower Montane Wet habitat. I hypothesized that variation s in altitude would influence Odonata biodiversity, a bundance and species richness. I used a butterfly n et to collect Odonata samples at five different elevation s located at between altitudes of 1425 m and 1525 m There was no significant correlation between altitu de 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 abundan ce of Cora chirripa and altitude (r^2=0.3809; R=0.974679; N=5; p=0.004818). This may indicate th at Cora chirripa is more sensitive to environmental factors determined by altitude than other Odonata s pecies. Resumen Odonata son muy sensibles a diferencias en el medio ambiente. Este estudio investiga especies de Odon ata en Monteverde, Costa Rica. Presum que la diversid ad, abundancia y nmero de especies de Odonata. Us e un red de mariposas para obtener individuos del ord en Odonata a cinco altitudes entre 1425 m and 1525 m. No hubo una correlacin significativa entre altitud y el numro de especies (r^ 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 correlacin significativa entre altitud y la abundancia de Cora chirripa Este puede ser un indcio que Cora chirripa es ms sensible a cambios en altitud que otros espe cies de Odonata. INTRODUCTION The order Odonata includes dragonflies and damselfl ies, aquatic insects that can be found around freshwater habitats. Odonates tend to be sp ecialists and generally have narrow distributional ranges (Kalkman et al. 2007) Odonata larvae 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 microhabitat s such as leaves in riffles (Ramrez 2000). As a result, Odonata distribution is usuall y determined by the very specific conditions under which their larvae survive (Calver t 1908). Altitude is an important factor when considering th e ideal habitat for a given species. Increased altitude, for example, means de creased temperatures. This could affect odonates because, although some species of l arger dragonflies and damselflies are able to thermoregulate to some extent, smaller odon ates are unable to do so effectively. This 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 temp erature at cooler temperatures, decreasing their range. Due to cool temperatures an d other factors associated with higher altitudes, many odonates could have trouble survivi ng in such a habitat. Because Odonata larvae have such narrow ranges, the y are generally vulnerable to disturbance and require habitat preservation (Ramr ez 2000). In order to protect Odonata biodiversity, therefore, it is important to underst and the sorts of habitats in which a majority of Odonata species survive. Several studi es have shown that Odonata diversity is greater at lower elevations. However, little re search has been done on the order Odonata in the tropics in spite of the fact that mo re 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 Clo ud Forests, and little research has been done concerning Odonata along forest streams i n general (Ramrez 2000). This study focuses on Odonata in the Monteverde Clo ud Forest. More specifically, I observed the effect of altitude on species richness and abundance of Odonata in forested streams in the Lower Montane We t Forest. I also looked specifically at the effect of altitude on the abundance of the c ommon 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, bio diversity and species richness at lower altitudes than at higher altitudes. METHODS Study Sites I conducted my study at the Quebrada Maquina, a fre shwater stream located in the Lower Montane Wet region of Monteverde, Costa Rica. As m easured at an attitude of 1460, this region receives 2519 mm of precipitation annually a nd 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 u sed stakes to indicate the boundaries. Procedures During trial 1, I began sampling at the site of hig hest 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 plast ic containers in order to prevent recollecting and re-counting the same individuals. W hen 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 o f the first session to allow time for recording data and for switching locations. I cont inued to move down the river and repeated the process at all elevations.
I kept one individual of each morphospecies and pre served it in a freezer so that it could later be identified. I used laminates to ide ntify each species. If I could not identify a morphospecies with the laminates, I sent it to El adio Cruz. The remaining Odonata were released after data collection. Sampling occurred on July 27th, July 29th, July 30th, July 31st and August 2nd. I completed five trials, each on a different day. Ea ch trial started at 9:30 am, and each day I started at a different elevation. For example, t he first day I started at the site of 1535 m of elevation, the second day 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 o n. I always worked down the river, and once I reached the lowest elevation of 1425 m, I re turned to the site of highest elevation (1535 m) and continued to work my way down until al l 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 affe cted by time of day. I first determined species richness, H, evenness a nd abundance at each altitude. Then I used a Non-Parametric Spearman Correlation a nalysis to determine whether or not each of these variables had a relationship with alt itude. I also determined the abundance of common damselfly species Cora chirripa and common dragonfly species Brechmorhoga rapax I ran a Non-Parametric Spearman Correlation to d etermine the correlation between altitude and the abundance of b oth 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 Odo nata varied across different altitudes. Only two individuals and one species we re 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 negati ve correlation between altitude and evenness (Fig 3). Finally, there was a non-signifi cant 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 correl ation between altitude and abundance of C. chirripa (Fig 5). There was a non-significant positive corr elation 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 significan t 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 a ltitude. This could imply that the majority of Odonata species, including Brechmorhoga rapax, are not sensitive to small differences in altitude. Changes in temperature, d issolved oxygen content and any other environmental factor associated with altitude were probably too small to have a
significant impact on odonate distribution. Theref ore, future studies should test the effect of altitude over a larger range, as this might demo nstrate a more significant correlation between altitude and species 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 shou ld be used. The site at 1425 m showed unusually low abundance a nd species richness. This could be because it was located next to the Hotel B elmar, a source of disturbance. As Odonata do not respond well to disturbance (Ramrez 2000), the additional factor of disturbance may have skewed results. In order to c ontrol for additional factors such as disturbance, the same experiment should be conducte d on a different river or at more sampling sites along the Quebrada Maquina. I did find that C. chirripa was more common at higher altitudes. Such results could 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 abun dance of odonates than those with lower levels of dissolved oxygen (Salmah et al. 200 6). 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, measur es should be made to protect source habitats. For example, the addition of phos phorus or nitrogen into a system can increase eutrophication, thereby depleting dissolve d oxygen within a water system (Carpenter et al. 1998). Such effects could be avo ided by ensuring that increased soil or fertilizer runoff does not occur near the river sou rces. AKNOWLEDGEMENTS I would like to thank Tania Chavarra for overseein g my research. I would like to thank Karen Masters, Alan Masters, Pablo Allen Monge and Jos Carlos Caldern for additional assistance with my research. I would li ke to thank CIEE for providing me with the research materials. I would like to thank Elad io Cruz for helping me to identify Odonata species. Finally, I would like to thank th e Estacin Biolgica de Monteverde for allowing me to conduct research on their property. LITERATURE CITED Carpenter, S.R., N.R. Caraco, D.L. Correll, R.W. Ho warth, A.N. Sharpley and V.H. Smith. 1998. Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological Applications 8(3): 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. Popul ation demography and sex ratio in a neotropical damselfly (Odonata: Coenagrionidae) i n 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 dragonflies (Odonata) in freshwater. Hydrobiologia 595: 351-363. May, M. L. 1976. Thermoregulation and adaptation t o temperature in dragonflies (Odonata Anisoptera). Ecological Monographs 46: 1-32. Calvert, P. P. 1908. The composition and ecologic al relations of the Odonate fauna of Mexico and Central America. Proceedings of the Aca demy of Natural Sciences of Philadelphia. 60(3): 460-491. Ramrez, A. 2000. Dragonflies and Damselflies of Costa Rican Cloud Forests 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 97. Salmah, M.D., R. Che, S. W. Tribuana and A. A. Hass an. 2006. The population of Odonata (dragonflies) in small tropical rivers with reference to asynchronous growth patterns. Aquatic Insects 28: 195-209.
Table 1. Species richness, H, evenness and abundance of Odo nata varied with altitude. n rr Table 2. The abundance of Cora chirripa and Brechmorhoga rapax differed with altitude. Figure 1. Relationship between Odonata species rich ness and altitude. I did not find a significant relationship (r^ 2 =0.3331; p=0.450185).
Figure 2. Relationship between H and altitude. I did not find a significant relationship (r^2=0.1841; p=0.62). Figure 3. Relationship between Odonata evenness and altitude. I did not find a significant relationship (r^2=0.5153; p=0.188120).
Figure 4. Relationship between Odonata abundance an d altitude. I did not find a significant relationship (r^2=0.03221; p=0.188120).
Figure 5. Relationship between the abundance of Cora chirripa and altitude. I did find a significant relationship (r^2=0.3809; R=0.974679; N =5; p=0.004818). Figure 6. Relationship between altitude and the ab undance of Brechmorhoga rapax I did not find a significant relationship (r^2=0.1099 ; p=0.872889).