Abstract
The spatial scale at which demographic performance (e.g., net reproductive output) varies can profoundly influence landscape-level population growth and persistence, and many demographically pertinent processes such as species interactions and resource acquisition vary at fine scales. We compared the magnitude of demographic variation associated with fine-scale heterogeneity (<10m), with variation due to larger-scale (>1ha) fluctuations associated with fire disturbance. We used a spatially explicit model within an IPM modeling framework to evaluate the demographic importance of fine-scale variation. We used a measure of expected lifetime fruit production, EF , that is assumed to be proportional to lifetime fitness. Demographic differences and their effects on EF were assessed in a population of the herbaceous perennial Hypericum cumulicola (~2,600 individuals), within a patch of Florida rosemary scrub (400×80m). We compared demographic variation over fine spatial scales to demographic variation between years across 6 yr after a fire. Values of EF changed by orders of magnitude over<10m. This variation in fitness over fine spatial scales (<10m) is commensurate to postfire changes in fitness for this fire-adapted perennial. A life table response experiment indicated that fine-scale spatial variation in vital rates, especially survival, explains as much change in EF as demographic changes caused by time-since-fire, a key driver in this system. Our findings show that environmental changes over a few tens of meters can have ecologically meaningful implications for population growth and extinction.
Highlights
The spatial scales at which plant population performance is estimated, and the extent to which vital rates vary through space, have important ramifications for the robustness of demographic estimates (Gurevitch et al 2016)
Because 69% of the occupied gaps were larger than 10 m2 and 88% of the total plants occurred in gaps larger than 10 m2, the observed scale of spatial correlation indicates that vital rates can vary considerably within the sandy gaps in which H. cumulicola occurs (Fig. 3d–f)
We show that fine-scale spatial variation in vital rates leads to large variation in an integrative measure of reproductive success over small spatial scales
Summary
The spatial scales at which plant population performance is estimated, and the extent to which vital rates (survival, growth, reproduction) vary through space, have important ramifications for the robustness of demographic estimates (Gurevitch et al 2016). The aggregate behavior of collections of populations can vary widely from any individual population within that collection (Gurevitch et al 2016, Hui et al 2017), and the overall extinction risk may be much lower than that indicated by the average population performance (Abbott et al 2017, Hui et al 2017, Dibner et al 2019). Many drivers of plant demographic performance vary at fine scales. Neighboring associations affect the abundance and composition of seed predators, herbivores, and Article e03287; page 2
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
