Extending Grime's CSR model to predict plant demographic responses across resource availability gradients: evidence from the patagonian steppes

NASTA, LAUTARO L.; LEVA, PAULA E.; PREMOLI, ANDREA C.; AGUIAR, MARTIN R.

OIKOS

WILEY-BLACKWELL PUBLISHING, INC

Año: 2024

0030-1299

Sexual reproduction, growth, and survival are crucial demographic strategies for plantpopulation viability. Here, we propose a conceptual model predicting demographicresponses of species based on their ecological strategy and the heterogeneity of environmentalconditions within a biogeographical unit and then applied it to a case studyfrom a 5˚ latitudinal gradient in the Patagonian steppes. We also aim to disentanglegenetic from environmental effects on demographic responses. We performed in situand common garden experiments with two species from six local populations of theOccidental Phytogeographical District of the Patagonian steppes. Species differ in keyecological traits, and thus fit into Grime’s model for evolutionary strategies in plants:one as competitive species and the other as stress-tolerant species. We calculated populationgrowth rate (λ) and performed elasticity analyses to compare the contributionof each demographic strategy to population fitness between species and among localpopulations distributed along 600 km latitudinal gradient with differences in meanannual precipitation (MAP). We highlight four results. First, the competitive specieschange from sexual reproduction to growth as MAP increases. Second, the stress-tolerantspecies relied on growth and survival along the MAP gradient. Third, interannualvariation in resource availability modulated demographic responses for both strategies.Fourth, based on the comparison of the in situ and common garden experiments,we submit that demographic responses were genetically driven. Our study shows thatdemographic responses can be roughly predicted by the ecological strategy across environmentalgradients. We show that differences arise not only between species, but alsowere genetically driven differences within species among local populations. Scaling upplant-level responses to population-level dynamics allows for a process-based understandingof current and future biogeographical species organization. Furthermore,conservation and restoration efforts should be guided by demographic strategiesunderlying population viability.