Introducing a New Field Technique: Finding Life Cycle Transition Ages (e.g., Juvenile-Adult)

Authors: Taly Drezner*, York University, Zvi Drezner, California State University, Fullerton, N Balakrishnan, McMaster University
Topics: Biogeography, Arid Regions, Field Methods
Keywords: biogeography, arid lands, field methods
Session Type: Poster
Day: 4/5/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

The objective of this study is to introduce a technique for estimating the mean age at which such transitions (e.g., juvenile to adult) occur. We present a new methodology that can be used for any species (though especially useful for long lived species) to quickly and accurately estimate transition age in a population including a spreadsheet that gives instant results ( To demonstrate the method, eight independent datasets for a long-lived species (Carnegiea gigantea, Cactaceae) are used for transition from non-reproductive juvenile to adult, and as a different example of a stage transition, four datasets are for the onset of branching (representing the last life stage with the greatest reproductive output in this species). We find that the oldest juveniles and youngest adults can be effectively and accurately used to estimate age (or other measure) of transition. The mean age of transition to reproductive adult in Carnegiea range from 52-106 years of age in the four populations, with SEs that are less than 1 year in all four populations. The ages for the transition to the branched form ranged from 78-139 years (SE <1 year in all four also). Differences in transition ages across populations can be explained by climate differences across sites. This technique is robust and reliable for estimating transition ages in any plant or animal population. The ages (or other measurement unit) associated with these stages are fundamentally important for understanding life cycle stages, their duration, and for quantifying reproduction and establishing baseline data in populations.

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