Estimation of demographic parameters of some plant species accounting for imperfect detection probabilities

• Published in: Population ecology Vol. 66; no. 1; pp. 22 - 38
• Main Authors: Martínez‐Villegas, Jorge A., Pisanty, Irene, Martorell, Carlos, Hernández‐Apolinar, Mariana, Valverde, Teresa, Granados‐Hernández, Luisa A., Rodríguez‐Sánchez, Mariana, Zúñiga‐Vega, J. Jaime
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.01.2024; Blackwell Publishing Ltd
• Subjects: Bias; capture–mark–recapture methods; Data collection; Demographics; Demography; Detection; detection probability; Flowers & plants; Parameter identification; Parameters; percent relative bias; Plant population; Plant populations; Plant species; Plants; Population studies; Populations; Probability; Probability theory; Quantitative analysis; Seedlings; Species; state transition probability; Survival; Survival analysis
• ISSN: 1438-3896; 1438-390X
• DOI: 10.1002/1438-390X.12159

Detection probability (p) in plants is imperfect in natural conditions due to several factors. This imperfect detectability is rarely accounted for in the estimation of demographic parameters, such as survival probabilities (S) or transition rates between different life states or size classes (ψ), which may result in inaccurate quantitative information about plant populations. In this study, we used previously collected data of five plant species belonging to different families with contrasting life forms and habitats (Flaveria chlorifolia, Mammillaria hernandezii, Neobuxbaumia macrocephala, Govenia lagenophora, and Castilleja tenuiflora), data simulations, multi‐state models (a demographic tool that explicitly accounts for p), and direct estimation of survival and transition rates (i.e., assuming perfect detection) to identify in which species, states, or demographic parameters the bias caused by ignoring our imperfect detectability is more severe. Detection was imperfect (p < 1) for all our study species. In general, ignoring detection probabilities yielded underestimated survival and transition rates in all five species. Biases caused by assuming perfect detection were also large and significant, mainly in inconspicuous life states and size classes, such as seedlings and dry individuals. In contrast, considering detection probabilities resulted in fewer underestimated survival and transition rates, with smaller and mostly nonsignificant biases. Intriguingly, some transitions were overestimated even when accounting for detection probabilities. Our findings highlight the importance of considering that detection of most plant species is imperfect in the field, even in species that are apparently conspicuous, to avoid incorrect inferences about plant populations. Plants present detection probability lower than 1 (i.e., detection is imperfect), but this is rarely accounted for in plant demographic studies. We estimated survival and transition rates in five contrasting plant species through data simulations, multi‐state models (method that accounting for p), and direct counts (method that assumes perfect detection; i.e., p = 1) to identify in which species, states, or demographic parameters the bias caused by ignoring our imperfect detectability is more severe. Most of the estimated demographic rates turned out to be substantially underestimated and biased when detection probabilities are not accounted for, so inferences about population trends and conservation statuses of plant species are likely erroneous in studies that have ignored the imperfect detectability of plant species in the field.