A 2013 paper by Michael Ghedotti and Matthew Davis reexamines the phylogeny of Fundulus killifishes using both genetic and morphological characters, and the evolution of salinity adaptation among this group. Some of their interesting phylogeny conclusions are:
The Diamond Killifish (Adinia xenica) is most closely related to the Spotfin Killifish (Fundulus luciae); so the genus Adinia is synonymized back into Fundulus (F. xenicus). The sister group to the Luciae + Diamond pair is … you guessed it …. F. chrysotus! (That wasn’t your guess? Me neither).
The other species that look and behave more like chrysotus (rubrifrons, cingulatus, sciadicus) are on the “Zygonectes branch” containing the five “Starhead group” species and three “Notatus group” species. The Diamond/ luciae +Chrysotus branch joins the tree just below the Starhead +Notatus branch.
The two west coast Fundulus (F. lima and parvipinnis) are related to F. zebrinus + kansae. The branch supporting those two groups is basal to the Zygonectes branch.
On the other side of the phylogentic tree, basal to those two groups, are all the remaining Fundulus: the studfish and most of the marine/brackish species (other than luciae, xenicus, lima, parvipinnis). There are some phylogenetic surprises on that side too:
The Speckled Killifish (F. rathbuni), traditionally grouped with studfish in a subgenus “Xenisma” is placed on the branch with the Banded Killifish (F. diaphanus) and its cousins in Lake Waccamaw and Lake Phelps. The rest of the Studfishes join below that branch.
The Banded group + Studfish group branch is a sister group to the Mummichogs and Marsh killies (grandis, heteroclitus, confluentus and kin), and below that fork they join with the final branch containing majalis, similis, and seminolis.
The proposed new phylogenetic tree of Fundulus is on page 44 of the Ghedotti and Davis paper. This link below requires a Bioone subscription -- not a free download.
Fieldiana Life and Earth Sciences Number 7 :1-65. 2013
Phylogeny, Classification, and Evolution of Salinity Tolerance of the North American Topminnows and Killifishes, Family Fundulidae (Teleostei: Cyprinodontiformes) -- Michael J. Ghedotti and Matthew P. Davis (2013)