Subspecies in the Sarus Crane Antigone antigone revisited; with particular reference to the Australian population.

Boripat Siriaroonrat,Robert N Van Zalinge,George Archibald,Timothy D Nevard,Martin Haase,Michael Wink,Nuchjaree Purchkoon,Tin Nwe Latt,Si-Min Lin,Stephen T Garnett,Ian Leiper

doi:10.1371/journal.pone.0230150

Abstract

Subspecies are often less well-defined than species but have become one of the basic units for legal protection. Evidence for the erection or synonymy of subspecies therefore needs to be founded on the best science available. Here we show that there is clear genetic disjunction in the Sarus Crane Antigone antigone, where previously the variation had appeared to be clinal. Based on a total sample of 76 individuals, analysis of 10 microsatellite loci from 67 samples and 49 sequences from the mitochondrial control region, this research establishes that the Australian Sarus Crane A. a. gillae differs significantly from both A. a. antigone (South Asia) and A. a. sharpii (Myanmar and Indochina). A single sample from the extinct Philippine subspecies A. a luzonica clustered with A. a. gillae, hinting at the potential for a more recent separation between them than from A. a. antigone and A. a. sharpii, even though A. a. sharpii is closer geographically. The results demonstrate that failure to detect subspecies through initial genetic profiling does not mean discontinuities are absent and has significance for other cases where subspecies are dismissed based on partial genetic evidence. It could also be potentially important for sourcing birds for reintroduction to the Philippines.

Highlights

Species are defined along a continuum from emphasising phenotypic distinctiveness through to reproductive incompatibility [1] with over 30 definitions currently in use [2]
Deviations from the HardyWeinberg equilibrium at several loci in A. a. antigone and A. a. sharpii suggested that these subspecies are probably not panmictic, we cannot rule out effects of genetic drift or selection
We have shown that A. a. gillae differs significantly from the A. a. antigone and A. a. sharpii genetic cline described by others

Summary

Introduction

Species are defined along a continuum from emphasising phenotypic distinctiveness through to reproductive incompatibility [1] with over 30 definitions currently in use [2]. Subspecies are even less well defined and this is uneven amongst taxa. Subspecies represent geographically defined populations that are potentially incipient species, diagnosable by at least one heritable trait but still reproductively compatible [3]. To define subspecies statistically [4,5], debate continues [6,7] and the expectation that genetic analysis would resolve ambiguities has not eventuated. While cetacean biologists are content to define subspecies quantitatively on the basis of mitochondrial DNA control region sequence data alone [8], this approach has been rejected for birds [9]; not least because there is often discordance between mitochondrial and nuclear DNA [10]

Methods

Results

Discussion

Conclusion