ZOBODAT - www.zobodat.at Zoologisch-Botanische Datenbank/Zoological-Botanical Database Digitale Literatur/Digital Literature Zeitschrift/Journal: Denisia Jahr/Year: 2002 Band/Volume: 0004 Autor(en)/Author(s): Biedermann Robert Artikel/Article: Leafhoppers (Hemiptera, Auchenorrhyncha) in fragmented habitats 523- 530 © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at Leafhoppers (Hemiptera, Auchenorrhyncha) in fragmented habitats R. BIEDERMANN Abstract The distribution of leafhoppers (inclu- patterns in the habitat patches, in most ding planthoppers, spittlebugs and tree- leafhopper species effects of area and iso- hoppers) largely depends on the distribu- lation on density and occupancy were tion of their host plants. Plants occur reported. Increasing patch area often more or less aggregated and frequently resulted in higher densities and higher form discrete patches. In natural as well as incidences. On the other hand, increasing in cultural landscapes these patches may isolation was found to reduce the inciden- be fragmented to some extent. A review of ce in the patches. The relevance of these existing studies on leafhopper populations results are discussed in the light of recent in fragmented landscapes summarises the metapopulation theory. current knowledge on the role of area and isolation on occurrence and density of Key words: Auchenorrhyncha, host leafhoppers. Whereas little information is plant, habitat fragmentation, area, isola- available on the dynamics of occupancy tion Denisia 04, zugleich Kataloge des OÖ. Landesmuseums, Neue Folge Nr. 176 (2002), 523-530 523 © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at Introduction The analysis of leafhopper communities may yield additional information on, for instance, The overall feature of leafhoppers (inclu- species richness or trophic interactions in rela- ding planthoppers, spittlebugs and treehop- tion to habitat configuration (e.g. DENNO & pers) is their close relation to plants. The host RODERICK 1991). plants provide nutrition (e.g. BACKUS 1985, There a two major theoretical concepts COBBEN 1988), shelter for eggs (e.g. CLARIDGE dealing with the explanation of animal distri- et al. 1977) and transmission channels for bio- butions on islands or habitat patches. The acoustic signals (e.g. MlCHELSEN et al. 1982). theory of island biogeography (MACARTHUR Accordingly, one major requisite of leafhopper & WILSON 1967) predicts species numbers on habitats is the presence of the host plants. In particular in host plant specialists among leaf- islands or habitat patches in relation to isola- hoppers the habitat is principally given by the tion and area. In leafhoppers, the theory of distribution of the host plants. island biogeography was studied, for instance, by NlEDRINGHAUS (1991) on dune islands in Plants frequently occur aggregated to some the North Sea. The application of island bio- extent and form discrete patches. The amount geography theory is confined to communities and physiology of the host plant may largely and seems not suitable for the analysis of determine the quality of such host plant pat- populations of single species (see HANSKI ches (e.g. PRESTIDGE 1982, MOON et al. 2000). 2001). Further, it assumes a mainland as a However, some leafhopper species exhibit source of colonising individuals. In fragmen- more complex habitat requirements. Additio- ted landscapes there is not necessarily a main- nal factors like host plant architecture, vege- land, but a situation with a large number of tation structure or microclimate may be rele- patches of similar area may occur. The corre- vant (e.g. CLARIDGE 1986, DENNO & RODE- sponding theory for populations on regional RICK 1991) and therefore the habitat may be scales is the metapopulation theory (HANSKI not primarily defined by the occurrence of the 1998). Recent metapopulation theory is a spa- host plants. In these species as well as in more tially explicit attempt to describe the dyna- generalist species with a broader range of host mics of a regional population with its members plants, the habitat patches may not be clearly distributed over a set of habitat patches. The delimited in the field. In contrast, in host main feature of metapopulation dynamics is plant specialists among the leafhoppers the the occurrence of extinction and colonisation survey of the distribution of the host plant was events in the habitat patches. found to be a very feasible way to determine all potential habitats of a certain species in a The objective of this review is to make a landscape (DENNO et al. 1981, BIEDERMANN survey on existing studies on leafhopper popu- 2000). lations in fragmented habitats and to discuss In natural as well as in cultural landscapes the results in regard to metapopulation theory. the habitats of leafhoppers are frequently frag- According to recent theory, the occurrence mented to some extent. In the recent two and density of leafhoppers in a particular habi- decades there is increasing concern about tat patch may depend on area, isolation, qua- ongoing habitat fragmentation by human lity and surrounding landscape structure of the activities, especially in cultural landscapes patch. The quality of a patch is the funda- (SETTELE et al. 1996). Fragmentation is sugge- mental factor for the survival and reproduc- sted to be one major cause of the extinction of tion of leafhoppers and is not a particular issue species and thereby declining biodiversity of fragmented habitats. The role of surroun- (MORRIS 1995). Looking at existing results on ding landscape structure on leafhopper distri- leafhoppers in fragmented habitats there are bution in habitat patches is largely unknown two levels of consideration, the population (but see JONSEN & FAHRIG 1997). Thus, in the level and the community level. At the popu- following the current knowledge on the role of lation level the occurrence, abundance and area and isolation on occurrence and density dynamics of particular species is of interest. of leafhoppers will be summarised. 524 © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at Habitat fragmentation and MANN 1997, BIEDERMANN 1998, ZABEL &. metapopulation theory TSCHARNTKE 1998, BIEDERMANN 2000, BLE- DERMANN unpubl. data). The main focus of Habitat fragmentation describes the these studies was on the dependency of the decrease in number and size of suitable habi- incidence (= probability of occurrence) and tats for species (e.g. HARRISON & BRUNA density of a particular species on area and iso- 1999, HUXEL &. HASTINGS 1999). The proces- lation of patches. In nearly all studies the first ses which lead to habitat fragmentation are step was a complete survey of the host plant decreasing area of patches up to their comple- patches in the study area providing the area te elimination and consequently increasing and isolation of the patches. This step was fol- isolation of patches. The term fragmentation lowed by a survey of the leafhopper occurren- describes both the processes and the outcome. ce or density in these patches. In order to It often implies a loss of habitat due to human quantify extinction or colonisation events in activities. As in natural landscapes suitable some studies the survey for the occurrence of habitat may be patchy without anthropogenic species has been repeated for several years or influence, here the term patchiness may be generations. more appropriate. However, in the following the term fragmentation will be used for both Incidence and area fragmented and patchy habitats. The first study on the relationship bet- Living in such a set of patches animals ween the occurrence of leafhoppers and the build up structured populations (HARRISON area of their habitats was performed by HALK- 1991), with its members distributed over a KA et al. (1971) on the spittlebug Philaenus number of habitats. In recent years the analy- spumarius (Aphrophoridae). They were analy- sis of spatial population structure has made a sing the distribution of Philaenus spumarius in rapid development, both in theoretical (e.g. island habitats in an archipelago of 135 islands HANSKI 2001) and empirical studies (e.g. in the Baltic Sea. GUTIERREZ et al. 2001). The results suggest A method to analyse the role of patch area that animals build up a wide continuous range on the occurrence of leafhoppers in host plant of spatial population structures from isolated patches is the use of incidence functions patches with virtually no immigration, over metapopulations with a limitation in the (ADLER & WILSON 1985, TAYLOR 1991). Incidence functions quantify the relationship dispersal between patches, up to patchy popu- between species presence and area in a set of lations with high colonisation and thus low patches of various area. In order to calculate extinction rates (HARRISON 1991, THOMAS & incidence functions, in each patch the presence KUNIN 1999). According to metapopulation or absence of the species is recorded. The theory (HANSKI 1998) the dynamics of the resulting occupancy patterns are related to occurrence of a species in its habitat patches is patch area using logistic regression (HOSMER determined by local extinction and colonisa- & LEMESHOW 2000). Logistic regression is a tion. The extinction rate is assumed to decrease statistical method which detects relationships with increasing patch area and the colonisa- between a dependent binary variable and one tion rate depends on the degree of isolation of or more independent variables. Here, the a patch. For the long-term