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Native Congener (native + congener)
Selected AbstractsSpecies richness and parasitism in an assemblage of parasitoids attacking maize stem borers in coastal KenyaECOLOGICAL ENTOMOLOGY, Issue 1 2003Guofa Zhou Abstract. 1. Parasitoids were reared from four species of lepidopteran stem borer collected in maize in southern coastal Kenya from 1992 to 1999. The stem borers included three native species, Sesamia calamistis Hampson, Busseola fusca Fuller, and Chilo orichalcociliellus (Strand), and one exotic borer, Chilo partellus (Swinhoe). A total of 174 663 caterpillars was collected, of which 12 645 were parasitised. 2. Twenty-six primary parasitoid species were reared from the exotic borer, C. partellus, indicating a rapid accumulation of native parasitoids on the alien borer. 3. The three most abundant parasitoids were the larval parasitoids Cotesia sesamiae Cameron, Cotesia flavipes (Cameron), and the pupal parasitoid Pediobius furvus Gahan. The pupal parasitoid Dentichasmias busseolae Heinrich and the larval parasitoid Goniozus indicus Ashmead were also common. All used an ingress-and-sting method of attack. 4. Cotesia flavipes, introduced into Kenya in 1993, was found in all seasons from 1997 onwards, and has become the most abundant stem borer larval parasitoid in the area. A native congener, Cotesia sesamiae, appeared in all seasons from 1992 to 1999. Together, these two parasitoids accounted for 83.3% of the parasitised borers. 5. Thirty parasitoid species were recovered in Kilifi district, 27 in Kwale, and 15 in Taita Taveta. Parasitism was much greater in Taita Taveta district than in Kilifi or Kwale districts. [source] Can niche use in red and grey squirrels offer clues for their apparent coexistence?JOURNAL OF APPLIED ECOLOGY, Issue 6 2002Jenny Bryce Summary 1Introduced species are, world-wide, one of the most serious threats to biodiversity. Grey squirrels Sciurus carolinensis are one of many introduced species to have threatened a native congener; they are thought to have replaced red squirrels Sciurus vulgaris throughout much of the UK as a result of competition. The rate of competitive replacement may be influenced by habitat composition, with some red squirrel populations persisting for prolonged periods in the presence of greys in predominantly coniferous forest. 2Here the similarity of red and grey squirrels' pattern of habitat use was investigated in Craigvinean forest in Scotland, UK, a site that has experienced apparent coexistence for up to 30 years. Overlap was examined in several dimensions: spatial overlap of home ranges, dynamic association and niche overlap. Habitat selection was examined at three levels: selection of core home range areas, selection of tree species within the home range, and the characteristics of patches used intensively by each squirrel species in comparison with random locations within their home range. 3Although there was overlap between red and grey squirrel ranges, there were clear differences in the macrohabitats utilized, with red squirrels selecting areas of Norway spruce Picea abies and grey squirrels selecting riparian corridors of mixed woodland for their home ranges. Within their home ranges, habitat selection by individual red and grey squirrels was similar, but again with reds selecting Norway spruce and greys selecting patches of mixed conifers and broad-leaved trees. As no habitat variables consistently affected the microdistribution of red and grey squirrels within blocks or ,stands' of trees, stands that were used were thought to constitute good and relatively homogeneous habitats for squirrels of either species. 4There was no evidence to suggest that red and grey squirrels avoided using the same areas at the same time, and potential niche overlap was considerable (0·77). However, partitioning of habitats may have reduced competition between red and grey squirrels and hence have contributed to red squirrel persistence at this site. 5This work (i) reinforces earlier proposals that forest management offers a promising tool to assist the conservation of red squirrels; (ii) raises the issue of determining the spatial scale at which coexistence operates; and (iii) offers an illustration of how the management of invasive species can be mediated through the manipulation of niche availability. [source] Variations in parasitism in sympatric populations of three invasive leaf minersJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2007S. Girardoz Abstract:, Parasitism was investigated in sympatric populations of three invasive gracillariid leaf miners in Europe, Cameraria ohridella, Phyllonorycter robiniella and Phyllonorycter platani to test the hypotheses that C. ohridella is less heavily parasitized by native parasitoids and attacked by fewer species than the two other invasive species. In all regions investigated, C. ohridella showed a lower parasitism rate, and its parasitoid complex was poorer in species than those of either Phyllonorycter spp. Comparisons were made between sympatric populations of C. ohridella on its main host tree, Aesculus hippocastanum, and an occasional host, Acer pseudoplatanus. Parasitism rates were similarly low and composed of the same parasitoid species on both trees. In contrast, a sympatric population of Phyllonorycter geniculella, a native species mining A. pseudoplatanus, was heavily parasitized by a totally different parasitoid complex. These results suggest that the low parasitism in C. ohridella by native polyphagous leaf miner parasitoids is due neither to its host tree, nor to a problem of synchronization between the phenology of the pest and that of its parasitoids. Instead, it probably results from the inability of the native parasitoids to locate, attack, or develop on a new host that does not have any native congener in Europe. [source] Insect diversity and trophic structure differ on native and non-indigenous congeneric rushes in coastal salt marshesAUSTRAL ECOLOGY, Issue 5 2010KERINNE J. HARVEY Abstract Displacement of native plant species by non-indigenous congeners may affect associated faunal assemblages. In endangered salt marshes of south-east Australia, the non-indigenous rush Juncus acutus is currently displacing the native rush Juncus kraussii, which is a dominant habitat-forming species along the upper border of coastal salt marshes. We sampled insect assemblages on multiple plants of these congeneric rushes in coastal salt marshes in Sydney, New South Wales, Australia, and compared the abundance, richness, diversity, composition and trophic structure between: (i) J. acutus and J. kraussii at invaded locations; and (ii) J. kraussii at locations either invaded or not invaded by J. acutus. Although J. acutus supported a diverse suite of insects, species richness and diversity were significantly greater on the native J. kraussii. Moreover, insect assemblages associated with J. kraussii at sites invaded by J. acutus were significantly different from, and more variable than, those on J. kraussii at non-invaded sites. The trophic structure of the insect assemblages was also different, including the abundance and richness of predators and herbivores, suggesting that J. acutus may be altering consumer interactions, and may be spreading in part because of a reduction in herbivory. This strongly suggests that J. acutus is not playing a functionally similar role to J. kraussii with respect to the plant-associated insect species assemblages. Consequently, at sites where this non-indigenous species successfully displaces the native congener, this may have important ecological consequences for community composition and functioning of these endangered coastal salt marshes. [source] Diversity and abundance patterns of phytophagous insect communities on alien and native host plants in the BrassicaceaeECOGRAPHY, Issue 6 2003Mark Frenzel The herbivore load (abundance and species richness of herbivores) on alien plants is supposed to be one of the keys to understand the invasiveness of species. We investigate the phytophagous insect communities on cabbage plants (Brassicaceae) in Europe. We compare the communities of endophagous and ectophagous insects as well as of Coleoptera and Lepidoptera on native and alien cabbage plant species. Contrary to many other reports, we found no differences in the herbivore load between native and alien hosts. The majority of insect species attacked alien as well as native hosts. Across insect species, there was no difference in the patterns of host range on native and on alien hosts. Likewise the similarity of insect communities across pairs of host species was not different between natives and aliens. We conclude that the general similarity in the community patterns between native and alien cabbage plant species are due to the chemical characteristics of this plant family. All cabbage plants share glucosinolates. This may facilitate host switches from natives to aliens. Hence the presence of native congeners may influence invasiveness of alien plants. [source] | |||||||||||||||||||