A century of invertebrate range extensions in the eastern North Pacific

Jordana K Sevigny, Bella G Lipsey, Theodore T Tran, Alexa Fredston 

Aim
Understanding the fundamental drivers of species’ range edges has been a core question in ecology and biogeography for centuries and has taken on new urgency in the Anthropocene. Yet range edges can rapidly shift over large distances, complicating long-term study of their dynamics. This is especially true in marine systems, where ranges may move hundreds of kilometers from one year to the next and where biodiversity monitoring programs are limited. To fill this gap, we synthesized nearly 120 years of records of marine invertebrate poleward range extensions in California to examine their prevalence/frequency and association with environmental variability on a year-to-year time horizon.

Location

Eastern North Pacific Ocean

Time Period

1903-2020

Major Taxa Studied

Marine invertebrates.

Methods
We collated a database of poleward range extensions of marine invertebrates through a systematic literature review of peer-reviewed literature and reports from California Cooperative Oceanic Fisheries Investigations. We then analyzed the frequency and geographic distance of range extensions across the species and time in association with the El Niño Southern Oscillation and the 2014-2016 marine heatwave.

Results
The final dataset comprises 63 species and 143 poleward range extensions. We found that the episodic range extension events are significantly associated with El Niño, and that further extensions occurred during stronger El Niño events. Twenty-two percent of the range extensions were during the 2014-2016 large marine heatwave—far more than in the years preceding or following it.

Main Conclusions
Our synthesis underscores that across many years and taxa, episodic poleward range extensions are not isolated curiosities but signals of how climate variability and warming can reshape coastal ecosystems. Gaining greater insight into short-term redistribution events and their interplay with long-term ecological change including range shifts is essential for forecasting long-term biogeographic change and for designing adaptive management strategies in a warming ocean.