Odonata of the Osa Peninsula - Frontier

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Seasonality Table 2: Total number of unique species found at the surveyed sites Over the course of this survey, the species richness per month stayed practically stable ranging starting from 26 species in January-February and ending with 23 species in May-June (Figure 6). A fairly similar number of new species was found each month which gives rise to the possibility that more species can be discovered in the following months. The stable species richness even with regular species discoveries is evidence of a clear seasonality pattern where some species disappear and new ones appear (see also Appendix II). Species richness 60 50 40 30 20 10 0 26 36 28 # of unique February March April May Month species Species richness by month 44 25 Percentage of total Swamp 14 73.7 Piro river 9 50.0 Ocelotte stream 2 20.0 OBC 1 16.7 Piro trail 0 0.0 Figure 6: Overall species richness and cumulative richness per months. 53 23 Species richness cumulative richness
Discussion 268 species of Odonata have been found in Costa Rica and at least 13 more species await formal description (Ramírez et al. 2000). The present survey yielded a total of 54 species, 20.2% of the species currently known to be present in Costa Rica. Thereby, at least two more species of the Aeshnidae family were seen but it was not possible to identify these individuals. Species accumulation curves and the fact that new species (i.e. species that are not included in the current species list) were still encountered on a regular basis towards the end of the surveying period suggest that more species await discovery. This can be contributed to species seasonality and the formation of new aquatic habitats in the wet season. For this survey I decided only to include individuals that were actually caught. Although this decision may have underestimated species richness and abundance in some instances, I felt that the advantages of this approach outweighed the disadvantages. For example, it reduced biasing this study towards species that are easily identified in the field and made identifying species that look very alike (especially in the Coenagrionidae family) easier. Thereby, it prevented learning over time which would have resulted in biased seasonality patterns. I made an exception for U. imbuta and U. fastigiata because these species were so abundant that not tallying them would severally underestimate their abundance. Even with this approach, it was not always possible to identify an individual to species or even genus level. In two cases it was not possible to identify the species based on pictures. Bill Haber suggested that Unknown species A could be an Erythrodiplax or Anatya species and Unknown species B a member of the Erythemis genus or possibly Erythrodiplax connata or Erythrodiplax kimminsi. The Psaironeura sp. is probably the more common P. remissa that can only be distinguished from P. selvatica from the morphology of their upper appendages. The Perissolestes sp. is either P. remotus or P. magdalenae that again, can only be distinguished from their cerci. When comparing this study to that of Ramírez et al. (2000), who looked at the dragonfly community of Costa Rica as a whole, it stands out that only a small percentage of the species found are endemic to Costa Rica or its bordering countries. In a way this is surprising since the Osa Pensinsula is often praised for its high number of endemic species. However, most studies on tropic insects show that species often have wide ranges and that high levels of endemism are the result of a sampling artifact (Gaston et al. 1996). Not a single member of the Gomphidae family was found even though this family is relatively species rich in Costa Rica (Ramírez et al. 2000). Gomphidae generally have cryptic coloration and emerge for only short periods of time and are therefore hard to find. The results of this project are a first step towards a possible monitoring program that can detect early changes in forest composition and water quality and the effects of management.
Page 1 and 2: Odonata of the Osa Peninsula Brenda
Page 3 and 4: Site description Even though Costa
Page 5 and 6: Methods To account for both seasona
Page 7 and 8: Species distribution patterns For t
Page 9: Abundance and Richness Comparisons
Page 13 and 14: Appendix I: Odonata Species checkli
Page 15 and 16: Appendix II: Phenology of Odonata o
Page 17 and 18: Appendix III: Odonata of the Osa Pe
Page 19 and 20: Leptobasis vacillans ♂ © W.A. Ha
Page 21 and 22: Protoneura sulfurata ♂ Protoneura
Page 23 and 24: Erythemis vesiculosa ♂ Erythemis
Page 25 and 26: Orthemis schmidti ♂ Unknown speci

Odonata of the Osa Peninsula - Frontier

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