Introducing the bipartite Package: Analysing Ecological Networks

摘要: Interactions among species in ecological communities have long fascinated ecologists. Prominent recent examples include pollination webs (Memmott et al., 2004), species-rich predator-prey systems (Tylianakis 2007) and seed dispersal mutualisms (all reviewed Bluthgen 2007). Many of the topological descriptors used food since 1960s limited meaning when only two trophic levels are investigated (for example chain length: Pimm, 1982/2002; Montoya 2006). Here, network becomes bipartite, i.e. every member one level is connected to members other level: direct interactions within regarded as unimportant. For bipartite networks very many, more or less different, indices been proposed capture important features species. example, degrees (number target linked to) strength (sum dependencies on target) supposed quantify importance a web. The new R-package introduced here, provides functions viualise calculate series commonly describe pattern webs. It focusses consisting levels, e.g. predator-prey-webs. We had three types mind writing this package: seed-disperser, plant-pollinator predatorprey systems. Bipartite networks, analysed plotted package can be represented by matrix, which, our definition, columns represent higher level, rows lower level. Entries matrix observed links, either quantitatively (with many per link) qualitatively (binary). Usually such matrices sparse, marginal sums (i.e. abundance distributions) highly skewed average number link low (around 2: With presented we wanted overcome main deficiencies field: 1. Lack software various networks. And 2. No convenient plotting tool for This article aims briefly present visualisation (plotweb visweb), then an output from calculation network-level (using function networklevel) finally address some miscellaneous issues do with fitting degree distributions, secondary extinction slopes null models Along several also 19 data sets pollinator taken National Center Ecological Analysis Synthesis webpage devoted topic (www.nceas.ucsb. edu/interactionweb). There at repository, quantitative