title: Robustness of trait distribution metrics for community assembly studies under the uncertainties of assembly processes.
abstract: Numerous studies have revealed the existence of nonrandom trait distribution patterns as a sign of environmental filtering and/or biotic interactions in a community assembly process. A number of metrics with various algorithms have been used to detect these patterns without any clear guidelines. Although some studies have compared their statistical powers, the differences in performance among the metrics under the conditions close to actual studies are not clear. Therefore, the performances of five metrics of convergence and 16 metrics of divergence under alternative conditions were comparatively analyzed using a suite of simulated communities. We focused particularly on the robustness of the performances to conditions that are often uncertain and uncontrollable in actual studies; e.g., atypical trait distribution patterns stemming from the operation of multiple assembly mechanisms, a scaling of trait-function relationships, and a sufficiency of analyzed traits. Most tested metrics, for either convergence or divergence, had sufficient statistical power to distinguish nonrandom trait distribution patterns without uncertainty. However, the performances of the metrics were considerably influenced by both atypical trait distribution patterns and other uncertainties. Influences from these uncertainties varied among the metrics of different algorithms and their performances were often complementary. Therefore, under the uncertainties of an assembly process, the selection of appropriate metrics and the combined use of complementary metrics are critically important to reliably distinguish nonrandom patterns in a trait distribution. We provide a tentative list of recommended metrics for future studies.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 9808578 Japan. mshiro5@gmail.com
authors.forename: Masahiro
authors.initials: M
authors.lastname: Aiba
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303 China.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Katabuchi
authors.affiliation: Tomakomai Research Station, Field Science Center for Northern Biosphere, Hokkaido University, Takaoka, Tomakomai 053 0035 Japan.
authors.forename: Hino
authors.initials: H
authors.lastname: Takafumi
authors.affiliation: Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 3058506 Japan.
authors.forename: Shin-Ichiro S
authors.initials: SS
authors.lastname: Matsuzaki
authors.affiliation: Graduate School of Life Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 9808578 Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: Tomakomai Research Station, Field Science Center for Northern Biosphere, Hokkaido University, Takaoka, Tomakomai 053 0035 Japan.
authors.forename: Tsutom
authors.initials: T
authors.lastname: Hiura
mesh_terms: D017753:Ecosystem; D008954:Models, Biological; D035501:Uncertainty