Developmental costs of rapid growth in a damselfly

Abstract.  1. Developmental costs of rapid growth in terms of increased fluctuating asymmetry are expected to contribute to the widespread occurrence of growth rates below the physiological maximum, but have rarely been demonstrated. Here, these costs are studied for the first time in an invertebrate, the damselfly Lestes viridis , using a rearing experiment where early- and late-hatched larvae of both sexes were reared at decreasing or permanent water levels.
2. Late-hatched animals were more asymmetrical than early-hatched animals except for males in the drying treatment. Also, females were more asymmetrical than males except in early-hatched animals in the drying treatment.
3. The data presented suggest that in females but not in males treatment groups with higher growth rates have more asymmetrical wings. However, at the individual level no relationship between growth rate and asymmetry was present.
4. Possible reasons why the suggested trade-off between growth and developmental instability was not present at the individual level, and at the group level only in females, are discussed.     

Role of nurse plants in Araucaria Forest expansion over grassland in south Brazil

Abstract Araucaria Forest expansion over grassland takes place under wet climate conditions and low disturbance and it is hypothesized that isolated trees established on grassland facilitate the establishment of forest woody species beneath their canopies. Forest with Araucaria angustifolia is a particular type of Brazilian Atlantic Forest and the main forest type on the highland plateau in south Brazil, often forming mosaics with natural Campos grassland. The objectives of this paper were to evaluate the role of isolated shrubs and trees as colonization sites for seedlings of Araucaria Forest woody species on grassland, to determine which species function as preferential nurse plants in the process and the importance of vertebrate diaspore dispersal on the structure of seedling communities beneath nurse plants. The study was conducted in São Francisco de Paula, Rio Grande do Sul State, where we sampled isolated shrubs and trees in natural grassland near Araucaria Forest edges. Seedlings were counted and identified, and seedling diaspore dispersal syndromes, size and colour were registered. We detected 11 woody species with a potential role in nucleating grassland colonization by forest species. Beneath the canopies of nurse plants more forest species seedlings were found compared with open field grassland and the seedlings had diaspores mostly dispersed by vertebrates. Also, more seedlings were found under the canopy of A. angustifolia than beneath other nurse plant species. We conclude that A. angustifolia trees established on grassland act as nurse plants, by attracting disperser birds that promote colonization of the site by other forest species seedlings, and that under low level of grassland disturbance, conservation of frugivorous vertebrate assemblages may increase forest expansion over natural grassland and also facilitate the regeneration of degraded forest areas.     

Inter‐specific competition and competition‐free space in the tephritid parasitoids Utetes anastrephae and Doryctobracon areolatus (Hymenoptera: Braconidae: Opiinae)

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The Development of Fast-Start Performance in Fishes: Escape Kinematics of the Chinook Salmon (Oncorhynchus tshawytscha)

C-starts are high acceleration swimming movements critical forpredator avoidance by fishes. Since larval fishes are particularlyvulnerable to predation, C-start behavior is likely to be especiallyimportant during early life history stages. This paper examinesthe developmental changes in C-start performance with kinematicdata on immature chinook salmon (Oncorhynchus tshawytscha) (eleuthroembryostage, sensu Balon, 1975). The scaling of C-start kinematicsof immature fishes differs from that of adults. Adult C-startdurations increase with increasing body length while C-startdurations of immature fishes decrease (e.g., adult stage 1 duration[sec] = 0.0019.length [L] [cm] $ 0.026 [R² = 0.77] [Webb, 1978];eleuthroembryos stage 1 duration [sec] = –0.026L [cm]$ 0.100 [R² = 0.81]). Distance traveled during stage 2 alsodiffers between adult and immature fishes. Adult distance traveledscales directly with length (distance [cm] = 0.38L^1.01 [cm],R² = 0.96 [Webb, 1978]) while chinook eleuthroembryo distancetraveled is positively allometric with length (distance [cm]=0.37L¹³¹ [cm], R² = 0.83). There are similarities in the developmentof C-starts and burst swimming. For example, mean velocity scalessimilarly between the two locomotor modes (For burst swimming:U_mean [cm/sec] = 8.1 ± 1.1L [cm] $ 4.89 [R² = 0.86] [Webband Corolla, 1981]. For C-start stage 2: U_mean [cm/sec] = 10.96L[cm] - 14.09 [R² = 0.70]). This study demonstrates that C-startescape performance improves during early post-hatching development.Comparisons of immature chinook salmon fast-starts with dataon larval burst swimming and on adult C-starts suggest thatchanges specific to developing fish affect the scaling of kinematicparameters.