Critical Appraisal Fitness and body size in mature odonates
Natalia Sokolovska, Locke Rowe and Frank Johansson*
The relationship between body size and fitness components in odonates was examined using a meta-analysis of 33 published studies. There was a positive and significant overall effect of body size on mating rate and lifetime mating success among males. There was also a weaker but still significant positive effect of body size on survivorship of males. The relationship between body size, mating rate, longevity, and lifetime mating success differed significantly between males of territorial and nonterritorial species. The effect of body size was significant for all fitness components in territorial species but significant only for longevity and lifetime mating success in nonterritorial species. Effect sizes appeared to be strongest on longevity in both sexes, and on male mating rate in territorial species. Other effect sizes, even when significant, were small. Despite a much smaller data set, female fitness also increased significantly with body size. Both clutch size and longevity showed a significant positive relationship with body size. These results suggest that there is a general fitness benefit to large size in odonates. Nevertheless, significant heterogeneity is apparent in this effect, which can be attributed to sex, mating system, and fitness component. Finally, these analyses point to inadequacies in the current data that need further study before the potentially rich patterns in size effects on fitness can be explored more thoroughly.
Стрекозы: биоиндикация пестицидов.
Authors: Takamura-K Hatakeyama-S Shiraishi-H
Odonate Larvae as an Indicator of Pesticide Contamination
APPLIED ENTOMOLOGY AND ZOOLOGY 1991, Vol 26, Iss 3, pp 321-326
NATL-INST-ENVIRONM-STUDIES, 16-2 ONOGAWA, YATABE, IBARAKI 305, JAPAN
The abundance of odonate larvae was surveyed in a river
system at two upstream stations surrounded by rice fields
lacking aerial spraying of pesticides, two midstream stations
surrounded by rice fields with and without aerial spraying, and
four downstream stations surrounded by sprayed fields. Species
diversity and numbers of individuals were much lower at the
downstream stations. Pesticide contamination from ground
spraying occurred at one upstream station as well as one
midstream and all downstream stations. Damage to the odonate
larvae was not clearly evident except at one downstream station.
Damage by the aerially sprayed insecticides seemed appreciable
at the downstream stations. The distribution of odonate larvae
in a river may be restricted by pesticide contamination and thus
can indicate pesticide contamination.
Стрекозы: расселение имаго.
Kelvin F. Conrad, Karen H. Willson, Katherine Whitfield, Ian F. Harvey, Chris J. Thomas and Thomas N. Sherratt
Characteristics of dispersing Ischnura elegans and Coenagrion puella (Odonata): age, sex, size, morph and ectoparasitism
Ecography Volume 25 Issue 4 Page 439 - August 2002
In this study we assessed whether individuals of the damselfly species Ischnura elegans and Coenagrion puella that moved between ponds differed in their mean characteristics from individuals that did not move. Overall, the sex (female) and species (C. puella) that spent the most time away from the breeding site was more likely to move between ponds. Ischnura elegans males that dispersed had significantly longer forewings than males that did not, while male C. puella parasitised by water mites were more likely to disperse than unparasitised males. There was no evidence for differences in dispersal rates among the female colour forms of either I. elegans or C. puella. In general, the differences in dispersal characteristics between sexes and species could be explained by underlying variation in activity and mobility. The majority of dispersal between breeding sites by C. puella and I. elegans did not appear to be directed, but probably arose from chance movements occasionally taking individuals to a different pond from which they emerged.
Стрекозы. Распределение имаго.
Volume 25 Issue 4 Page 459 - August 2002
Distribution and habitat specialization of species affect local extinction
in dragonfly Odonata populations
Esa Korkeamaki and Jukka Suhonen
The object of our study was to determine the effect of distribution and habitat specialization of odonate species on local extinction in streams in central Finland. We studied the local extinction of the 20 most abundant dragonfly (Odonata) species in 34 small creeks and brooks in central Finland. The historical presence of each studied species in our research area was confirmed using existing records gathered between 1930 and 1975. A minimum of five records was available for each species. During the summers of 1995 and 1996, we investigated the current persistence of 219 separate populations with historical presence. In total, 98 historical populations were vanished. As predicted, we found that species with a narrow distribution were less persistent than species with a broad distribution. Therefore, the extinction risk of a species was inversely related to the width of its regional distribution. Using reference works, species were categorized into two main breeding habitat types: lotic species or lentic species. The species main habitat type was a significant predictor of local extinction risk after statistical removal of the effect of regional distribution on extinction risk. The lotic species had lower local extinction risk than other species. Altogether, the highest extinction risk was found in habitat-specialist species associated with peatlands, probably due to loss of natural breeding habitat. On the other hand, extinction risk was lower in widely distributed habitat generalist species than true lotic species. The local extinction within species was more common in small dynamic upstream than in larger stable downstream habitats. The results of this study are consistent with meta-population theory.