Ecology aims to develop general rules to predict phenomena such as the evolution of senescence, extinctions, invasions, or resilience. All of these phenomena are demographic in essence, since they are controlled by rates of survival, growth, reproduction/establishment of individuals within populations. New databases are now allowing the re-evaluation of the classical tenets of ecology. In the case of demography, matrix population models (MPMs) have become the most prominent tool, resulting in MPM for over 1,500 animals and 1,300 plants world-wide. The recent launching of the COMPADRE Plant Matrix Database and COMADRE Animal Matrix Database (www.compadre-db.org) position this tool as an excellent candidate to revisit those tenets to examine global questions and highlight future opportunities.
We used COMPADRE and COMADRE to examine: (i) the main drivers of variation in plant and animal life history strategies, (ii) the sources of demographic variation in space and time, and (iii) the gaps of knowledge and future opportunities in demographic research. We first developed a phylogenetically-corrected multivariate analysis of key life history traits derived from over 800 animals and plants. Next, we examined the intra-specific variation of each species with information for > 4 years and >2 populations, decomposing their life history traits with mixed effect models as a function of time or space. Last, we contrasted the amount of demographic information currently archived in COMPADRE and COMADRE with the estimates of taxonomic diversity across the globe and tree of life (of plants and animals).
We found that both plants and animals show a consistent alignment of their life history strategies according longevity and iteroparity. However, this potential global validity of our findings is somewhat limited by the spatial replication of each of our 800 studies. Most demographic studies are done at only one site, and our patterns became less significant when including intra-species spatial variation. The temporal and spatial exploration of population dynamics in COMPADRE and COMADRE indicates over 60% of the variation was spatially intra-specific, and that the temporal correlation was more important in short-lived species both animals and plants. Despite the remarkable efforts in exploring species population dynamics worldwide, important biases exist towards charismatic animals (vertebrates) and plants (orchids, timber-producing trees and cacti), with little exploration in groups of great taxonomic diversity and economic value, such as corals or algae. Most field studies take place within developed countries, leaving untapped biodiversity hotspots like South Africa, Costa Rica or Polynesia.