Molecular phylogenetics of moray eels (Muraenidae) demonstrates multiple origins of a shell-crushing jaw (Gymnomuraena, Echidna) and multiple colonizations of the Atlantic Ocean

Abstract

Moray eels (Muraenidae) are apex predators on coral reefs around the world, but they are not well studied because their cryptic habitats and occasionally aggressive behaviors make them difficult to collect. We provide a molecular phylogeny of moray eels including 44 species representing two subfamilies, eight genera, and all tropical ocean basins. Phylogenetic relationships among these taxa are estimated from portions of mitochondrial loci cytochrome b (632bp) and cytochrome oxidase subunit 1 (596bp), and portions of the nuclear loci RAG-1 (421bp) and RAG-2 (754bp). We test four sets of contrasting phylogenetic hypotheses using Bayes Factors, Shimodaira–Hasegawa tests, and Templeton tests. First, our results support the subfamily-level taxonomic distinction between true morays (Muraeninae) and snakemorays (Uropterygiinae), statistically rejecting hypotheses of non-monophyly for each subfamily. Second, we reject a monophyletic grouping of the genera Gymnomuraena and Echidna, which share a durophagous (shell-crushing) cranial morphology and dentition, indicating that the durophagous characters are not homologous. Third, we demonstrate that durophagous feeding habits and associated morphological characters have evolved in parallel in an ancestor of Gymnomuraena and at least three additional times within the genus Echidna. Finally, the tree topology indicates multiple invasions of the Atlantic from the Indo-Pacific, one of these occurring immediately prior to formation of the Isthmus of Panama approximately 2.8MYA (million years ago) and one or two others occurring in the early to mid Miocene. Cladogenesis occurring within the Atlantic during the mid Miocene and Pliocene also contributed to moray species diversity. These data include a pair of sister species separated by the Isthmus of Panama, allowing a time-calibrated tree with an estimated crown age for Muraenidae at between 41 and 60MYA, consistent with fossil evidence. Most lineage accumulation within morays occurred from the late Oligocene (24–27MYA) through the Miocene (5–23MYA) to the late Pliocene (∼2.5MYA).