Phylogenetic relationships of crown conchs (Melongena spp.): the corona complex simplified


*Stephen A. Karl, Hawaii Institute of Marine Biology, University of Hawaii at Manoa, PO Box 1346, Kaneohe, HI 96744, USA.


Aim  The larval stages of marine taxa are often assumed to have an overriding influence on the phylogeographical structure of a species as well as on rates of speciation. Phylogeographical disjunctions in high-dispersal marine taxa are generally attributed to historical events or contemporary ecological factors. The lack of genetic structure in low-dispersal marine taxa is often ascribed to rafting by juveniles, yet few studies discuss the effects of historical conditions. Around peninsular Florida, there are three species of the crown conch, Melongena, which have direct-developing, crawl-away larvae. One of these species, M. corona, is subdivided into three subspecies. We refer to these five taxa as the corona complex. We assessed the validity of these taxa and tested for patterns of phylogeographical subdivision.

Location  Intertidal Florida and eastern Alabama, USA, Mexico and Panama.

Methods  The mitochondrial DNA cytochrome c oxidase subunit I, and ribosomal DNA 16S genes were sequenced from adult individuals representing all extant taxa of Melongena. Phylogenetic trees were constructed under maximum likelihood analysis (heuristic search with tree bisection–reconnection branch-swapping) using the program paup*.

Results  Sequence variability in the complex was low and suggested no systematic or phylogeographical partitioning in the corona complex. The species complex probably consists of a single lineage exhibiting no clear pattern of genetic partitioning over the entire range.

Main conclusions  The present study supports the designation of only four extant species within the genus: M. corona, M. patula, M. melongena and M. bispinosa. The subspecies M. corona corona, M. c. johnstonei and M. c. altispira, and the species M. sprucecreekensis and M. bicolor, should all be considered to be M. corona. Surprisingly, even with very low larval and adult vagility, no population subdivisions were noted in our genetic analyses. Our analyses also substantiate the paraphyletic status of the family Melongenidae.