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Understanding the demographic drivers of realized population growth rates
Author(s) -
Koons David N.,
Arnold Todd W.,
Schaub Michael
Publication year - 2017
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1002/eap.1594
Subject(s) - fecundity , vital rates , population growth , population , population model , ecology , biological dispersal , biology , density dependence , abundance (ecology) , population size , population dynamics , population ecology , demography , demographic analysis , population decline , statistics , mathematics , fertility , habitat , sociology
Identifying the demographic parameters (e.g., reproduction, survival, dispersal) that most influence population dynamics can increase conservation effectiveness and enhance ecological understanding. Life table response experiments ( LTRE ) aim to decompose the effects of change in parameters on past demographic outcomes (e.g., population growth rates). But the vast majority of LTRE s and other retrospective population analyses have focused on decomposing asymptotic population growth rates, which do not account for the dynamic interplay between population structure and vital rates that shape realized population growth rates ( λ t=N t + 1 / N t ) in time‐varying environments. We provide an empirical means to overcome these shortcomings by merging recently developed “transient life‐table response experiments” with integrated population models ( IPM s). IPM s allow for the estimation of latent population structure and other demographic parameters that are required for transient LTRE analysis, and Bayesian versions additionally allow for complete error propagation from the estimation of demographic parameters to derivations of realized population growth rates and perturbation analyses of growth rates. By integrating available monitoring data for Lesser Scaup over 60 yr, and conducting transient LTRE s on IPM estimates, we found that the contribution of juvenile female survival to long‐term variation in realized population growth rates was 1.6 and 3.7 times larger than that of adult female survival and fecundity, respectively. But a persistent long‐term decline in fecundity explained 92% of the decline in abundance between 1983 and 2006. In contrast, an improvement in adult female survival drove the modest recovery in Lesser Scaup abundance since 2006, indicating that the most important demographic drivers of Lesser Scaup population dynamics are temporally dynamic. In addition to resolving uncertainty about Lesser Scaup population dynamics, the merger of IPM s with transient LTRE s will strengthen our understanding of demography for many species as we aim to conserve biodiversity during an era of non‐stationary global change.