Landscape genetics identifies streams and drainage infrastructure as dispersal corridors for an endangered wetland bird

Abstract

Anthropogenic alterations to landscape structure and composition can have significant impacts on biodiversity, potentially leading to species extinctions. Population‐level impacts of landscape change are mediated by animal behaviors, in particular dispersal behavior. Little is known about the dispersal habits of rails (Rallidae) due to their cryptic behavior and tendency to occupy densely vegetated habitats. The effects of landscape structure on the movement behavior of waterbirds in general are poorly studied due to their reputation for having high dispersal abilities. We used a landscape genetic approach to test hypotheses of landscape effects on dispersal behavior of the Hawaiian gallinule (Gallinula galeata sandvicensis), an endangered subspecies endemic to the Hawaiian Islands. We created a suite of alternative resistance surfaces representing biologically plausible a priori hypotheses of how gallinules might navigate the landscape matrix and ranked these surfaces by their ability to explain observed patterns in genetic distance among 12 populations on the island of O`ahu. We modeled effective distance among wetland locations on all surfaces using both cumulative least‐cost‐path and resistance‐distance approaches and evaluated relative model performance using Mantel tests, a causal modeling approach, and the mixed‐model maximum‐likelihood population‐effects framework. Across all genetic markers, simulation methods, and model comparison metrics, surfaces that treated linear water features like streams, ditches, and canals as corridors for gallinule movement outperformed all other models. This is the first landscape genetic study on the movement behavior of any waterbird species to our knowledge. Our results indicate that lotic water features, including drainage infrastructure previously thought to be of minimal habitat value, contribute to habitat connectivity in this listed subspecies.

Hawaiian waterbird movement across a developed landscape

“…Gallinules had the highest residency to a single wetland (0.93 average residency), although gaps in time when birds were not detected (range = 2–25 days) suggest occasional movement of birds outside of the monitored wetlands. The lack of detected movement found in our study are consistent with mark‐recapture studies on Hawaiian gallinules and population genetic studies that reported moderate to strong genetic structuring between wetlands, even between wetlands close to one another (Sonsthagen et al 2018, van Rees et al 2018 a , b , c ). On the other hand, large, continuous wetlands (e.g., Hamakua Marsh, James Campbell NWR) on Oʻahu had evidence of higher gene flow among sampled locations, indicating gallinules will move between wetlands if there is habitat connecting wetlands (van Rees et al 2018 c ).…”

“…On the other hand, large, continuous wetlands (e.g., Hamakua Marsh, James Campbell NWR) on Oʻahu had evidence of higher gene flow among sampled locations, indicating gallinules will move between wetlands if there is habitat connecting wetlands (van Rees et al 2018 c ). Indeed, at a landscape level, current genetic structuring of gallinules on Oʻahu is best explained by connectivity through waterways (e.g., streams, drainage ditches), which were abundant in the intervening matrix between wetlands (van Rees et al 2018 b ). In the closely related Mariana common moorhen ( Gallinula chloropus guami ), individual birds frequently moved among permanent and ephemeral wetlands between wet and dry seasons, and rapidly colonized a new island (≥70 km dispersal) when new habitat was created (Takano and Haig 2004).…”

The potential for nature-based solutions to combat the freshwater biodiversity crisis

“…Green stormwater infrastructure practices also create urban freshwater habitats that support local wildlife [91,92]. In Hawai'i, urban stormwater NBS like drainage swales and ditches provide not only habitat, but facilitate landscape-scale movements and enhanced population connectivity in an endangered waterbird [93]. Such contributions not only to total habitat but also landscape connectivity could support biodiversity in urban wetlands.…”

An evaluation of isolation by distance and isolation by resistance on genetic structure of the Persian squirrel (Sciurus anomalus) in the Zagros forests of Iran

“…The land cover map was converted to a binary surface with two classes: Forest and Non-Forest. In some cases, analysis of binary habitat-non habitat surfaces can provide complementary or novel insights compared with the analysis of multi-variable surfaces (van Rees et al, 2018;Van Strien et al, 2012).…”