# Ecological Niche Modeling of Hoplias malabaricus (Characiformes, Erythrinidae) Under Climate Change Scenarios

## TL;DR

This study uses climate models to predict how a South American freshwater fish's habitat may change due to climate change, highlighting risks to its survival.

## Contribution

The study applies ecological niche modeling to a genetically validated lineage of Hoplias malabaricus under climate change scenarios, revealing regional distribution shifts and isolation risks.

## Key findings

- Ecological niche models showed excellent performance (AUC > 0.9) in predicting habitat suitability for Hoplias malabaricus.
- Temperature seasonality and elevation were the most influential variables across all climate scenarios.
- Marajó Island experienced the highest loss of suitable habitat, increasing isolation risks under high-emission climate scenarios.

## Abstract

Freshwater fish are highly vulnerable to climate change because they are restricted to inland waters and cannot readily disperse across geographical barriers, making them particularly exposed to catastrophic habitat losses. Understanding how environmental changes may affect the distribution of widespread species is critical for anticipating biodiversity responses and informing conservation efforts. In this study, we employed ecological niche models (MaxEnt) to assess the current and future potential distribution of
Hoplias malabaricus
, a generalist freshwater predator of ecological and fisheries importance in South America. We focus on the Amazon, Tocantins–Araguaia, Guiana Shield, Brazilian Atlantic Coast, and Marajó Island basins, which encompass the current distribution of the species. We used bioclimatic variables derived from the global WorldClim v2.1 dataset under present‐day conditions and two future climate scenarios (SSP1–2.6, a low‐emission pathway, and SSP5–8.5, a high‐emission pathway) to project habitat suitability. The models demonstrated excellent predictive performance (AUC > 0.9), identifying temperature seasonality (BIO4) and elevation as the most influential variables across all scenarios. Results revealed contrasting trends among hydrographic regions. The species showed increasing association with more seasonal environments and highly suitable habitats contracted under the most extreme scenario. Marajó Island exhibited the highest loss of suitable area, highlighting increased isolation risks. Overall, our findings indicate that
H. malabaricus
may persist under climate change through niche shifts and partial range contractions. However, habitat loss, reduced connectivity, and regional genetic isolation may compromise long‐term viability, particularly under high‐emission scenarios.

This study employs ecological niche models (ENMs) to project current and future habitat suitability for a genetically validated lineage of
Hoplias malabaricus
, a widely distributed Neotropical freshwater predator.