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 the eastern North Pacific to examine their prevalence and association with interannual environmental variability.

Location: Eastern North Pacific Ocean: 23°N - 60°N

Time Period: 1903-2020

Major Taxa Studied: Marine invertebrates.

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

Result: The final dataset comprised 153 poleward range extensions from 68 species. We found that the episodic range extensions were 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 underscored that across many years and taxa, episodic range extensions were not isolated curiosities but signals of how climate variability and warming are continuously reshaping marine 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.