The shorebirds (Charadriiformes): traits vs molecules lead to taxon exclusion issues, again

Cerny and Natale 2021 sought to clarify
the ‘time tree’ of shorebirds (= Charadriiformes).

Unfortunately, severe taxon exclusion
(Fig. 2) and the use of genes (Fig. 1), rather than traits (Fig. 2), mars this bird study.

Figure 1. Cladogram from Cerny and Natale 2021 employing too many species and too few genera. See figure 2 for list of missing taxa.
Figure 2. Subset of the LRT focusing on water birds. Here many more genera are included, including hummingbirds, penguins and geese, all missing from the study by Cerny and Natale 2021 (colors match Fig. 1). Colored taxa found in Cerny and Natale are not all related to Charadrius (fourth from top) when based on traits. So genes produce a big mess.

From the abstract:
“Shorebirds (Charadriiformes) are a globally distributed clade of modern birds and, due to their ecological and morphological disparity, a frequent subject of comparative studies.”

Understatement. The large reptile tree (LRT, 1890+ taxa) indicates the morphological disparity of Charadrius relatives was MUCH greater (Fig. 3) than Cerny and Natale imagined.

Figure 2. Balearica compared to its sister in the LRT, Charadrius, the plover/kildeer.
Figure 3. Balearica compared to its close relative in the LRT, Charadrius, the plover/kildeer.

From the abstract:
“While molecular phylogenies have been instrumental to resolving the suprafamilial back bone of the charadriiform tree, several higher-level relationships, including the monophyly of plovers (Charadriidae) and the phylogenetic positions of several monotypic families have remained unclear.”

If you want to clarify relationships, don’t use molecules. Too often they deliver false positives in deep time studies. Cerny and Natale also used WAY too few taxa based on comparisons to the LRT, which employs a wider gamut of birds in order to minimize taxon exclusion.

“The timescale of shorebird evolution also remains uncertain as a result of extensive disagreements among the published divergence dating studies, stemming largely from different choices of fossil calibrations.”

Use traits. Not molecules.

“Here, we present the most comprehensive non-supertree phylogeny of shorebirds to date, based on a total-evidence dataset comprising 336 ingroup taxa (89% of all extant species), 24 loci (15 mitochondrial and 920 nuclear), and 69 morphological characters.”

That’s what they all say. If the Cerny and Natale study is “the most comprehensive” study, how did these authors manage to omit so many taxa published years earlier (Fig. 2)? They were blinkered (= having their blinders on).

“Our node-dating analyses consistently support a mid-Paleocene origin for the Charadriiformes and an early diversification for most major subclades.”

Probably earlier. We have Mid-Paleocene penguins, so penguin ancestors (Fig. 2) needed time to evolve from more primitive charadriformes.

Note
Charadrius (Fig. 2) is a phylogenetically miniaturized version of longer-legged ancestral taxa, like Balearica and Burhinus. Once again, this is neotony at work, creating new taxa, completely overlooked by Cerny and Natale who likely relied on textbooks to determine which birds were traditional charadriiformes and which were not.

Test your textbooks to make sure your textbooks are valid if they repeat results gained from gene studies. This is basic science, so you can find this out for yourself using your own observations. It doesn’t take a PhD or expensive equipment.

References
Černý D and Natale R 2021. Comprehensive taxon sampling and vetted fossils help clarify the time tree of shorebirds (Aves, Charadriiformes) bioRxiv 2021.07.15.452585; doi: https://doi.org/10.1101/2021.07.15.452585

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