Modelling suitable breeding habitat and GAP analysis for the endangered Scaly-sided Merganser Mergus squamatus: implications for conservation

Abstract

Summary The Scaly-sided Merganser Mergus squamatus is a globally ‘Endangered’ species breeding in north-east Asia. Limited by information on the geographic distribution of suitable habitat, the conservation management programme has not been comprehensive or spatially explicit for the breeding population. This study combines potentially important environmental variables with extensive data on species occurrence to create the first species distribution model for the breeding Scaly-sided Merganser, followed by a GAP analysis to highlight the unprotected areas containing suitable habitat. The predictive map showing the most suitable breeding habitat for the Scaly-sided Merganser covered broad-leaved deciduous forest distributed in six provincial regions in south-east Russia, north-east China, and North Korea. The conservation GAP, i.e. 90% (38,813 km2) of highly suitable habitat, is mainly concentrated in the Sikhote-Alin and Changbai mountain ranges. This study suggests that prioritizing conservation of unprotected broad-leaved deciduous riverine forests within the above two mountainous regions should be included in international conservation planning, and the remaining suitable patches need to be preserved to allow range expansion in future. This predictive map improves the expert global assessment of breeding Scaly-sided Merganser distribution and provides a basic reference for establishing conservation areas or implementing conservation actions for the breeding Scaly-sided Merganser in north-east Asia.

Genetic diversity and shallow genetic differentiation of the endangered scaly‐sided merganser Mergus squamatus

“…It is likely that the limited historical population and narrow range of breeding habitats constrained the genetic variability. Breeding SSME populations are confined to submountain rivers with clear water, wide, deep and sinuous channels, gravel/rocky substrates with large gravel bars and riparian old growth forests (IUCN, 2017 ; Xu, Wang, et al., 2021a ), the amounts of which are small within the already restricted distribution range (Xu, Solovyeva, et al., 2021b ). In particular, female SSMEs are among the largest cavity‐nesting bird species and are confined by the limited large cavities of older trees, as there may otherwise be a cost of looking for suitable cavities in unfamiliar habitats.…”

“…The absence of a bottleneck signal probably resulted from limited demographic changes and/or the original lack of genetic variation. Xu, Wang, et al, 2021a), the amounts of which are small within the already restricted distribution range (Xu, Solovyeva, et al, 2021b).…”

“…However, coinciding with economic development since the last century, the SSME has become less common in many of its previously established habitats (BirdLife International, 2001 ; Solovyeva et al., 2014 ). Extensive field surveys and breeding habitat modeling have suggested that the global breeding range of SSME has recently contracted into two main areas, that is, the Sikhote‐Alin Range of Russia and the Changbai Mountains of China (Xu, Solovyeva, et al., 2021b ). The Sikhote‐Alin population is estimated to include 1643 pairs after an abrupt decline during the 1960s–1970s (Solovyeva et al., 2014 ).…”

“…In contrast to glaciated territories of the Northern Europe and Arctic North America, the LGM and post‐LGM dynamics of climate and landscapes were not so dramatic in the South of Russian far East and in Northeast China Clime changes led to significant moving of the vegetation borders to the South (in LGM) and to the North (in mid‐Holocene and during climatic optimum), especially well pronounced between 38 and 54 N. Cooling during the LGM was accompanied by the reduction of yearly precipitation (Belyanin et al., 2019 ; Korotky et al., 2010 ; Zhao et al., 2003 ). Thus landscapes, preferred for the SSME breeding (Xu, Solovyeva, et al., 2021b ), shifted southward during the LGM and shifted northward in mid‐Holocene. This may determine breeding range dynamics, and thus driving population differentiation for this riverine forest species.…”