title: Estimating species - area relationships by modeling abundance and frequency subject to incomplete sampling.
abstract: Models and data used to describe species-area relationships confound sampling with ecological process as they fail to acknowledge that estimates of species richness arise due to sampling. This compromises our ability to make ecological inferences from and about species-area relationships. We develop and illustrate hierarchical community models of abundance and frequency to estimate species richness. The models we propose separate sampling from ecological processes by explicitly accounting for the fact that sampled patches are seldom completely covered by sampling plots and that individuals present in the sampling plots are imperfectly detected. We propose a multispecies abundance model in which community assembly is treated as the summation of an ensemble of species-level Poisson processes and estimate patch-level species richness as a derived parameter. We use sampling process models appropriate for specific survey methods. We propose a multispecies frequency model that treats the number of plots in which a species occurs as a binomial process. We illustrate these models using data collected in surveys of early-successional bird species and plants in young forest plantation patches. Results indicate that only mature forest plant species deviated from the constant density hypothesis, but the null model suggested that the deviations were too small to alter the form of species-area relationships. Nevertheless, results from simulations clearly show that the aggregate pattern of individual species density-area relationships and occurrence probability-area relationships can alter the form of species-area relationships. The plant community model estimated that only half of the species present in the regional species pool were encountered during the survey. The modeling framework we propose explicitly accounts for sampling processes so that ecological processes can be examined free of sampling artefacts. Our modeling approach is extensible and could be applied to a variety of study designs and allows the inclusion of additional environmental covariates.
authors.affiliation: Graduate School of Agriculture Hokkaido University Nishi 9, Kita 9 Kitaku Sapporo Hokkaido 060-8589 Japan; Department of Forest Vegetation Forestry and Forest Products Research Institute 1 Matsunosato Tsukuba Ibaraki 305-8687 Japan.
authors.forename: Yuichi
authors.identifier: 0000-0001-9355-4413
authors.initials: Y
authors.lastname: Yamaura
authors.affiliation: Department of Biology San Francisco State University 1600 Holloway Avenue San Francisco California 94132.
authors.forename: Edward F
authors.initials: EF
authors.lastname: Connor
authors.affiliation: Patuxent Wildlife Research Center U. S. Geological Survey Laurel Maryland 20708.
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Royle
authors.affiliation: Itoh Research of Applied Plant Studies Katsura-machi 560-114 Satsunai Makubetsu Nakagawa County Hokkaido 089-0545 Japan.
authors.forename: Katsuo
authors.initials: K
authors.lastname: Itoh
authors.affiliation: Itoh Research of Applied Plant Studies Katsura-machi 560-114 Satsunai Makubetsu Nakagawa County Hokkaido 089-0545 Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Sato
authors.affiliation: Department of Forest Entomology Forestry and Forest Products Research Institute 1 Matsunosato Tsukuba Ibaraki 305-8687 Japan.
authors.forename: Hisatomo
authors.initials: H
authors.lastname: Taki
authors.affiliation: Graduate School of Agriculture Hokkaido University Nishi 9, Kita 9 Kitaku Sapporo Hokkaido 060-8589 Japan; National Institute for Environmental Studies 16-2 Onogawa Tsukuba Ibaraki 305-8506 Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Mishima
keywords: Species‐area relationship; density–area relationship; imperfect detection; incomplete spatial coverage; null model; random placement model; species richness estimator