Half-Saturation Constants in Functional Responses

TL;DR

This paper reviews and analyzes half-saturation constants across various species, examining their relationship with body size to improve ecological model parameterization.

Contribution

It provides a comprehensive overview of half-saturation constants in literature and explores their consistency with body size across taxa.

Findings

Half-saturation constants vary within one or two orders of magnitude across clades.

Allometric relationships help in consistent parameterization of ecological models.

Most data are from algae and invertebrates, with some from vertebrates.

Abstract

Our aim is to provide an overview of half-saturation constants reported in literature and to explore their consistency with body size. In many ecological models, intake of nutrients by plants and consumption of food by animals is considered to be a hyperbolic function of the nutrient concentration and the food density, respectively. However, data on the concentration (or density) at which half of the maximum intake rate is reached are scarce, limiting the applicability of the computational models. The meta-analysis was conducted on literature published worldwide. Most studies focused on algae and invertebrates, whereas some included fish, birds and mammals. The half-saturation constants obtained were linked to body size using ordinary regression analysis. The observed trends were compared to those noted in reviews on other density parameters. Half-saturation constants for different clades range within one or two orders of magnitude. Although these constants are inherently variable, exploring allometric relationships across different taxa helps to improve consistent parameterization of ecological models.