2019 ScienceDirect

evo-devo nonsense?

Genomes vary significantly but the body plans do not of the Caenorhabditis family.
The embryogenesis of four species of the Caenorhabditis family are similar.
Patterns of cell migration, cell death and differentiation are nearly identical.
Mechanism of establishment of left-right axis is conserved during evolution.

the embryonic development of all four Caenorhabditis species are nearly identical, suggesting that an apparently optimal program to construct the body plan of nematodes has been conserved for at least 20 million years.

This contrasts the levels of divergence between the genomes and the protein orthologs of the Caenorhabditis species, which is comparable to the level of divergence between mouse and human.

This indicates an intricate relationship between the structure of genomes and the morphology of animals.

Definition of intricate by Merriam-Webster

1 : having many complexly interrelating parts or elements : complicated

2 : difficult to resolve or analyze

https://www.merriam-webster.com/dictionary/intricate

the general strategy to construct a nematode evolved considerably during evolution.
substantial genomic differences
yet the four species are highly similar in external morphology and, as far as known, in their habitat and ecological requirements
this pattern would suggest an origin by allopatric, non-adaptive speciation.

Definition of Allopatric by Merriam-Webster 

http://www.merriam-webster.com/dictionary/allopatric
Allopatric definition is – occurring in different geographic areas or in isolation

 

would also agree with an adaptive species formation under at least partly sympatric conditions, driven by a yet-to-be-discovered subtle adaptive (ecological) differentiation.
it appears to be most astonishing that these organisms are apparently characterized by a high substitution rate (Cutter, 2008), genome reductions related to different reproductive modes (Fierst et al., 2015) and a low protein level genomic identity