I am a geologist, a paleontologist, and a network scientists. My research program is focused on understanding the interactions between plate tectonics, climate, and evolution of life as a complex system phenomenon. This interdisciplinary approach combines stratigraphy, paleobiology, and network science to address specific questions on spatiotemporal aspects of the fossil record. I am currently a postdoctoral fellow at the Integrated Science Lab (IceLab), a hub dedicated to cross-disciplinary research located at Umeå University in northern Sweden. IceLab research covers a wide range of scientific questions on the fossil record, social networks, phytoplankton, DNA folding, microbial economics, invasive species, and antibiotic resistance.

Geoscience education at all levels is an integral component of my research program and I use the physical and abstracted (digital) fossil records for teaching/learning geosciences in formal and informal learning settings. If you have any questions please don’t hesitate to contact me.

External Links:

Google Scholar || ORCID || ResearchGate || Linkedin || CvLAC || alexis.rojas-briceno@umu.se

Click here to visit selected field localities using Google TIME MACHINE


Date: Wednesday 24 March 2021

SPPAT: Spatial point pattern analysis of traces

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Trace fossils left by predators on skeletons of their prey, including drillholes, repair scars, fractures, and tooth marks, are the most powerful direct indicators on predator-prey interactions available in the fossil record. For instance, predatory drillholes can provide valuable behavioral information regarding selectivity of predatory attacks in terms of prey species, prey size, or drilling location on the prey skeleton (site-selectivity). Although predatory drillholes are spatially explicit traces that represent a uniform record of a single behavior and are frequent enough to make statistical analyses, current approaches used to evaluate site-selectivity ignore some spatial information.

The recognition that drillholes on prey skeletons are spatially explicit and can be mapped enables the development of a proxy for site-selectivity in drilling predation based on spatial point process modeling. In this paper, we introduce the spatial point pattern analysis of traces (SPPAT), an approach for visualizing and quantifying the distribution of predation traces on shelled invertebrate prey, which includes improved collection of spatial information inherent to drillhole location, improved visualization of spatial trends, and distance-based statistics for hypothesis testing.

Figure 1. Graphical output from the distance-based statistics estimated on modern beach-collected samples, and laboratory feeding trials.

Graphical output from the distance-based statistics estimated on the fossil samples, modern beach-collected samples, and laboratory feeding trials

We illustrate the SPPAT approach through case studies of fossil samples, modern beach samples, and modern experiments of gastropod predation on bivalve prey. SPPAT provides information on spatiotemporal changes in site-selectivity patterns of drilling predators, including variation in alternative shell-drilling behaviors, useful for understanding predator behavior and anti-predatory responses of prey. The SPPAT approach is transferrable to a wide spectrum of paleoecologic and taphonomic data such as encrustation and bioerosion, allowing for standardized investigation of a wide range of biotic interactions.

Date: Monday 8 March 2021

We re-examined the classic textbook model of ocean life published by Jack Sepkoski in 1981. Using a multilayer network representation of the fossil record, our research confirmed a gradual mid-Cretaceous mega-assemblage transition, comparable in magnitude to the Permian-Triassic transition, that could not be explained by a single catastrophic event. Our results suggest that gradual ecological changes, known as the Mesozoic Marine Revolution, triggered the rise to dominance of the Modern evolutionary fauna during the mid-Cretaceous.

Our paper in Communications Biolog provides an integrative framework of the metazoan macroevolution for future research.

Rojas, A., Calatayud, J., Kowalewski, M. et al. A multiscale view of the Phanerozoic fossil record reveals the three major biotic transitions. Commun Biol 4, 309 (2021). https://doi.org/10.1038/s42003-021-01805-y

Read the press release from our @CommsBio paper here

Date: Monday 8 February 2021

I am happy to collaborate in this amazing work by Joaquin Calatayud that provides the basis for a better understanding of climate-driven ecological and evolutionary processes, with implications for conservation strategies.

Calatayud, J., M., Neuman, M., Rojas, A., Rosvall, M. Regularities in species’ niches reveal the world’s climate regions. in press eLife (ref- 29-04-2020-ISRA-eLife-58397)

Date: Friday 2 August 2019