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2 Polish Journal of Ecology

2 2012

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Transgenerational effects on overall fitness : influence of larval feeding experience on the oviposition behaviour of seed beetle Acanthoscelides obtectus (Say)

Stojković B., Seslija Jovanović D., Tucić N.

Polish Journal of Ecology

2012

Vol. 60, nr 2

387-393

Oviposition behaviour is recognized as an ecologically significant trait in insects. Since herbivorous insect females have a potential to lay eggs on unsuitable host species, it is hypothesized that this behaviour may be the first step in host-range expansion. The most intriguing phenomenon, found in some insect species, is the ability of females to lay eggs on unsuitable places if hosts are unavailable; this behaviour is termed "egg-dumping". Egg-dumping can be adaptive plastic response in environments where hosts, either preferred or less suitable, may eventually become available. Transgenerational effects of this behaviour presume changes in larval feeding experience on different host species. Also, diverse larval experience may induce alterations in oviposition behaviour. To test whether egg laying behaviour of adult females can be modified by larval experience, we performed the experiment on two laboratory populations of Acanthoscelides obtectus (Say). First population (P) is housed in the laboratory on the common bean for 200 generations, whereas the second population (C) is derived from the first but has been raised for 197 generations on chickpea, a novel and less suitable host for larval development. In order to analyze differences between short-term and long-term effects of larval experience on eggdumping, both populations have been exposed to each host seed for one generation. The results of the study show that females from P population lay eggs more frequently in the absence of seeds when developed on chickpeas, compared with P females reared on beans. By contrast to P females, in C population, larval experience has no significant effects either on the number of dumped eggs or on the frequency of dumper females. These results demonstrate a significant inter-population diversification of phenotypic plasticity in egg-dumping behaviour depending on larval host experience. In other words, modification of oviposition behaviour, as a consequence of a long-term larval nutritional stress, can evoke previously unrecognized transgenerational effects.

Effect of vegetation and management on occurrence of larvae and adults of generalist Maniola jurtina L. (Lepidoptera) in meadow habitats

Kulfan J., Strbova E., Zach P.

Polish Journal of Ecology

2012

Vol. 60, nr 3

601-609

Larvae and adults of some generalist insect species co-occur in identical habitats whereas adults and larvae of other generalist species do not co-occur and occupy different habitats. The Meadow brown, Maniola jurtina (L.) (Lepidoptera: Nymphalidae), is common and widely distributed in Europe where it is considered a habitat generalist. As knowledge about the occurrence of the larvae of the Meadow brown is scarce (different and more difficult methods are needed to collect larvae compared to adults) a complex assessment of the life strategy of this generalist is limited. We addressed here the question as to whether the adults and larvae of the Meadow brown co-occurred in the same habitats and how they depended on the type of grassland vegetation and habitat management. We expected co-occurrence of adults and larvae and similar effects of habitat management on them. We selected four habitat types belonging to the alliance Arrhenatherion elatioris W. Koch 1926, which form mosaic patterns in the rural landscape of central Slovakia: (1) extensive meadows mown once a year, (2) extensive meadows mown twice a year, (3) abandoned meadows, and (4) ecotones between deciduous forests and meadows mown once a year. Adults were counted in each habitat on seven transects 50 m long (in seven replicates) during the summer of 2003, 2004 and 2005. Larvae were collected in each habitat on 10 transects 50 m long (ten replicates) by sweeping vegetation (60 sweepings per transect) at night in May 2005 and 2006. Both adults and larvae occurred in all the mentioned types of habitats. A high abundance of adults and larvae was recorded in extensive meadows mown once a year and in ecotones. The lowest abundance of adults and larvae was found in abandoned meadows. The differences between abandoned meadows and ecotones (in the case of adults) and between abandoned meadows and extensive meadows mown once a year (in the case of larvae) were significant in all study years (P <0.05; multiple comparisons, K-W ANOVA). In the abandoned meadows the number of adults and larvae (median) was approximately 2 to 5 and 5 to 25 times lower than in the preferred habitats, respectively. Maximum numbers of both adults and larvae per single recording/sampling date were obtained in extensive meadows mown once a year; that is 185 adults in a transect 350 m long and 4 m wide and 267 larvae in the transect 500 m long (600 sweepings). Hence, similar to adults, larvae tend to be habitat generalists. Our results have confirmed the "advantageous" life strategy of M. jurtina which enables the species to adapt to a wide range of habitats, including those under strong pressure from humans. Comparing management practices in the study habitats, meadows which are mowed once a year were the most appropriate alternative for this species.