Phylogeny and Jaw Ontogeny of Beloniform Fishes1

Integrative and Comparative Biology, Nov 2004 by Lovejoy, Nathan R, Iranpour, Mahmood, Collette, Bruce B

Phylogenetic analysis

All 2,516 characters (965 bp RAG2, 497 bp Tmo, 636 bp cyt b, and 415 bp 16S) were combined in a single matrix and the heuristic search algorithm of PAUP* (100 replicates of random taxon additions, TBR branch swapping) was used to search for most parsimonious trees. All characters were uniformly weighted. Oryzias (the ricefish representative) was used as an outgroup to root all trees. Nuclear, and mitochondrial datasets were also analyzed separately (using the same algorithm and settings) to investigate the contribution provided by each to the total molecular evidence hypothesis. For RAG2, sequence from the outgroup Oryzias was unobtainable due to PCR difficulties. To test the rooting of the tree, we conducted a separate RAG2 analysis with additional outgroups from Genbank, including Danio (NMLl31385), Taklfugu (AF 108420), Campylomormyrus (AF201622), Gnathonemus (AF201628), Chitala (AF201626), and Gymnarchus (AF201629). To test the root of the Tmo tree, we included Genbank sequences for labroids deposited by Streelman and Karl (1997). The two mitochondrial genes were analyzed together because it was assumed that the small size of each fragment would prevent effective phylogeny reconstruction. Decay indices for nodes were calculated using TreeRot (Sorenson, 1996), and bootstrap proportions were calculated using PAUP* (100 replicates with 50 random taxon additions per replicate).

The evolution of jaw characters was examined by optimizing juvenile and adult conditions on the total molecular evidence tree using MacClade (Maddison and Maddison, 1992). Jaw states were derived from the literature and from personal observations of specimens by the authors. We examined the effects of slight changes in tree topology by optimizing characters on alternative topologies.

RESULTS

Figure 1 shows the single most parsimonious tree derived from an unweighted parsimony analysis of the total molecular dataset. The tree is 5,670 steps long, with a consistency index (excluding uninformative characters) of 0.27, and a retention index of 0.58. In most respects, the tree is similar to the total evidence topology presented in Lovejoy (2000). Of the five currently recognized beloniform families, only two are monophyletic: the flyingfishes (Exocoetidae) and sauries (Scomberesocidae), whereas the needlefishes (Belonidae) and halfbeaks (Hemiramphidae) are paraphyletic. Only a single ricefish (Adrianichthyidae) was included as an outgroup, prohibiting tests of adrianichthyid monophyly.

The monophyletic sauries, which include the genera Scomberesox, Cololabis, and Ellasichthys, are deeply nested within needlefishes. The clade including sauries and the needlefish genera Belone and Petalichthys appears well-supported by decay indices and bootstrap scores.

The relationships of halfbeaks are more complex, with the included genera forming three clades. Zenarchopterus, Hemirhamphodon, Nomorhamphus, and Dermogenys, which all practice internal fertilization and are distributed in freshwater and estuaries of the Tndo-West Pacific, comprise a monophyletic group that is the sister clade to needlefishes/sauries. These halfbeak genera have been recognized as a separate family, Zenarchopteridae, based on evidence from the pharyngeal jaw apparatus (Tibbetts, 1992) and sperm ultrastructure (Jamieson and Grier, 1993). Meisner (2001) provides further anatomical evidence for the monophyly of this clade, with the addition of Tondanichthys (not included here). Based on the additional support of molecular data, we hereafter use the name Zenarchopteridae for this monophyletic group of halfbeaks.