Current Topics in Avian Conservation Genetics with Special Reference to the Southwestern Willow Flycatcher

Abstract

It is sometimes said that scientists are entitled to their own opinions but not their own set of facts. This suggests that application of the scientific method ought to lead to a single conclusion from a given set of data. However, sometimes scientists have conflicting opinions about which analytical methods are most appropriate or which subsets of existing data are most relevant, resulting in different conclusions. Thus, scientists might actually lay claim to different sets of facts. However, if a contrary conclusion is reached by selecting a subset of data, this conclusion should be carefully scrutinized to determine whether consideration of the full data set leads to different conclusions. This is important because conservation agencies are required to consider all of the best available data and make a decision based on them. Therefore, exploring reasons why different conclusions are reached from the same body of data has relevance for management of species. The purpose of this paper was to explore how two groups of researchers can examine the same data and reach opposite conclusions in the case of the taxonomy of the endangered subspecies Southwestern Willow Flycatcher (Empidonax traillii extimus). It was shown that use of subsets of data and characters rather than reliance on entire data sets can explain conflicting conclusions. It was recommend that agencies tasked with making conservation decisions rely on analyses that include all relevant molecular, ecological, behavioral, and morphological data, which in this case show that the subspecies is not valid, and hence its listing is likely not warranted.

The taxonomic basis of subspecies listed as threatened and endangered under the endangered species act

“…In the only authoritative statement on subspecies in North America, the American Ornithologists' Union (1957) Checklist, this subspecies was not accepted, although it had been described nine years earlier (Phillips, 1948). Data sets on mtDNA, amplified fragment length polymorphisms, niche modeling, and song vocalizations supported the AOU's decision to not designate E. t. extimus as a valid subspecies (Zink, 2015;Zink, 2016;see Theimer et al, 2016;Mahoney et al, 2020). Ruegg et al (2021) analyzed variation in 105,000 single nucleotide polymorphisms (SNPs) from 175 individuals and concluded that the subspecies was valid.…”

“…Its range includes the densely populated area of southern California from Palos Verde Peninsula south to the border with Baja California (and farther south to the end of Baja California Sur, where it becomes relatively common). The validity of the subspecies has been challenged (Zink et al, 2000;Zink et al, 2013;Zink et al, 2016) and defended (McCormack and Maley, 2015), and recent genomics data show that it is not evolutionarily distinct and hence not a valid subspecies (Vaźquez-Miranda et al, 2022). The USFWS has suggested that excluding this habitat has come at a cost of at least $1 billion (Gordon, 2018).…”