Regional and local factors interact to shape colonization and extinction dynamics of invasive Hydrilla verticillata in a patchy landscape

TL;DR

This study shows how landscape and local factors together influence the spread and disappearance of the invasive plant Hydrilla in river rock pools.

Contribution

The study demonstrates how the same disturbance (flooding) can have opposite effects on colonization and extinction depending on local conditions.

Findings

Larger, infrequently flooded pools near the river had higher colonization probabilities.

Smaller, frequently flooded pools near the river had higher extinction probabilities.

Colonization and extinction dynamics depend on both landscape and local patch characteristics.

Abstract

Understanding the response of species to global change requires disentangling the drivers of their distributions across landscapes. Colonization and extinction processes, shaped by the interplay of landscape‐level and local patch‐level factors, are key determinants of these distributions. However, disentangling the influence of these factors, when larger‐scale processes manifest at local scales, remains a challenge. We addressed this challenge by investigating the colonization and extinction dynamics of the aquatic plant, Hydrilla verticillata, in a complex riverine rock pool system. This system, with hundreds of rock pools experiencing varying flooding frequencies, provided a natural laboratory to examine how a single landscape‐level disturbance can differentially impact colonization and extinction depending on local patch characteristics to shape species distributions. Using 5 years of data across over 500 sites and more than 5000 surveys, we employed dynamic occupancy models to model colonization, extinction, and changes in Hydrilla patch occupancy while accounting for imperfect detection. Our results revealed that larger, infrequently flooded pools closer to the river were more likely to be colonized. In contrast, local extinction of Hydrilla was more likely in smaller pools closer to the river that flooded frequently. These findings underscore the importance of considering context‐dependence in species distribution models. The same landscape‐level disturbance (flooding) had opposing effects on colonization and extinction, with the direction and magnitude of these effects varying with local patch characteristics. Our study highlights the need for integrating local and landscape‐level factors, and considering how larger‐scale processes play out at the patch level, to understand the complex dynamics that shape species distributions.

Using dynamic occupancy modeling, we explored drivers of colonization and extinction dynamics of an invasive species, Hydrilla verticillata, within a novel complex landscape of 500+ riverine rock pools. We found that landscape and patch level characteristic, along with disturbance via flooding, influenced the probabilities of both colonization and extinction. Larger, less frequently flooded pools had high colonization probabilities, while smaller, more frequently flooded pools had higher extinction probabilities.

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