Cryptic species in a Vulnerable seabird: shorttailed albatross consists of two species

M Eda,M Konno,N Tomita,H Izumi,T Yamasaki,F Sato,S Konno,H Murakami

doi:10.3354/esr01078

Abstract

The occurrence of cryptic species within a threatened taxon is rare, but where they do occur, understanding species boundaries is essential for planning an effective conservation strategy. The short-tailed albatrossPhoebastria albatrusis a Vulnerable seabird that mainly breeds on Torishima and the Senkaku Islands in the western North Pacific. Although it has been tacitly regarded as a single management unit with 2 breeding sites, the species is known to comprise 2 genetically separated populations (Senkaku-type and Torishima-type). However, morphological examination of birds from both populations has not been conducted owing to the difficulty in accessing the Senkaku Islands. In this study, we examined the morphological differences between immigrants from the Senkaku Islands to Torishima (Senkaku-type) and native birds on Torishima (Torishima-type) and found significant differences in morphological characteristics between the 2 bird types. In general, Torishima-type birds were larger than Senkaku-type birds, whereas Senkaku-type birds had relatively longer beaks. Based on the morphological differences found in this study as well as genetic and ecological differences revealed in previous studies, we believe that Senkaku- and Torishima-type birds should be classified as different cryptic species. To the best of our knowledge, this is the first case of cryptic species being identified in a threatened avian species.

Highlights

The term ‘cryptic species’ refers to 2 or more species that are classified, or have been classified, as a single nominal species because of their indistinguishable morphology (Bickford et al 2007)
Blood was collected from all captured birds, measurements were not completed for some birds because of the bird’s condition and some measurements were only taken at a later point in the study (Table 1)
The target mitochondrial DNA (mtDNA) CR2 sequence was determined for all bird blood samples, and 12 haplotypes were found

Summary

Introduction

The term ‘cryptic species’ refers to 2 or more species that are classified, or have been classified, as a single nominal species because of their (at least superficially) indistinguishable morphology (Bickford et al 2007). Artificial translocation of chicks from Torishima to Mukojima Island in the Bonin Islands during the 2008 and 2012 breeding seasons resulted in the establishment of a new colony in the Bonin Islands (Deguchi et al 2017). At the end of the 2013−2014 breeding season, the global population was estimated to be 4200 individuals, with 3540, 650, and 10 birds on Torishima, the Senkaku Islands, and the Bonin Islands, respectively (Deguchi et al 2017, BirdLife International 2018). Research on the Senakaku Islands has not been conducted since 2002, mainly because of the difficulty in accessing the islands due to political reasons

Methods

Results

Conclusion