Colour variation is incongruent with mitochondrial lineages: cryptic speciation and subsequent diversification in a Gulf of California reef fish (Teleostei: Blennioidei)

Abstract

The Gulf of California endemic reef fish, Acanthemblemaria crockeri (Blennioidei, Chaenopsidae), reportedly has two colour morphs, one with melanic lateral spots ('Gulf' morph) and one with orange spots ('Cape' morph). In this study, we recorded colour morph in both males and females and collected mitochondrial DNA sequence data for cytochrome c oxidase I (COI) and tRNA-Pro/D-loop of specimens from throughout the Gulf to explore the genetic basis of the colour morphs. Two highly divergent (HKY + I distance = 11.9% for COI), reciprocally monophyletic lineages were identified, consistent with the presence of two parapatric species. A 30-km gap between the distributions of mitochondrial lineages roughly corresponds to a hypothesized former seaway across the Baja California peninsula north of La Paz, although the estimated divergence time (1.84 million years ago) is more recent than the hypothetical seaway (3-4 million years ago). Surprisingly, the distribution of mitochondrial species is not congruent with the distribution of either male or female colour morphs. Our analysis also revealed significant population differentiation within both species and no shared haplotypes among populations. The northern Gulf species includes four populations (NB, CB, NM and CM) corresponding to northern and central Baja and northern and central mainland sites, while the Cape species includes two populations (SB and SM) corresponding to the Baja and mainland sides of the southern Gulf. The NB/CB division corresponds to a hypothesized Plio-Pleistocene mid-peninsular seaway. The level of genetic divergence documented in this lineage is extraordinary for a marine fish with a pelagic larval stage within a semi-enclosed basin.

Polymorphism in a common Atlantic reef coral (Montastraea cavernosa) and its long-term evolutionary implications

“…Cheetham (1990, 1999) were among the first to test this correspondence, and demonstrate concordance between morphospecies and genetically delineated ones, clearly showing punctuated speciation and stasis in bryozoans and supporting the theory of punctuated equilibrium (Eldredge and Gould 1972). Combined analyses of morphological, genetic, and reproductive data have also been applied to various marine organisms on modern coral reefs, revealing large numbers of previously undiscovered cryptic species (Knowlton 1993(Knowlton , 2000Knowlton and Jackson 1994;Klautau et al 1999;Lee and Foighil 2005;Mathews 2006;Calvo et al 2009;Lin et al 2009; Barroso et al 2010) and underscoring the fact that current understanding of the speciation process in these organisms is inadequate. Here we examine the relationship between population size, geographic distribution, speciation rate, and species duration in a common reef coral, in an effort to better predict how this currently endangered group of organisms (Carpenter et al 2008) will respond to the many environmental factors, ranging from local to global in scale, which are increasingly threatening coral reefs.…”

Genetic and morphological evidence for cryptic diversity in the Careproctus rastrinus species complex (Liparidae) of the North Pacific

“…In marine fishes, molecular techniques have revealed many cryptic species that are difficult or impossible to distinguish based on morphological characters alone (e.g., Miya and Nishida 1997;Kon et al 2007;Hyde et al 2008;Lin et al 2009). However, no molecular studies of liparid fishes have been conducted, except for the generic-level phylogenetic study conducted by Knudsen et al (2007).…”

Ontogeny of microhabitat use and two-step recruitment in a specialist reef fish, the Browncheek Blenny (Chaenopsidae)

“…Sex was determined using lateral body coloration. Female Browncheek Blennies have a series of mid-lateral blotches, while males have several rows of light spots on a dark background (Stephens 1963;Lindquist 1985;Lin et al 2009); the anterior portion of the body bearing blotches in females was visible on all focal individuals included in this study. Most individuals \20 mm SL typically do not express sex-specific coloration, so all ''small'' individuals were classified as ''juveniles.''…”

“…These shelters serve as refuges from predators (Hastings 1991) and as egg-deposition sites (Hastings 1986). The Browncheek Blenny is endemic to the Gulf of California (Stephens 1963;Lin et al 2009), and its early life history is similar to that of most other small benthic reef fishes (Thresher 1984;Miller 1984;Munday and Jones 1998;Depczynski and Bellwood 2006), i.e., eggs deposited on the substrate (in this case inside shelters) are guarded by the resident male until hatching (Hastings 1988), when the larvae enter the plankton to later settle on hard substrates. In the central Gulf, Browncheek Blennies breed from early spring through at least May (Hastings 1988) and grow to at least 50.5 mm SL (Stephens 1963).…”

“…In the central Gulf, Browncheek Blennies breed from early spring through at least May (Hastings 1988) and grow to at least 50.5 mm SL (Stephens 1963). Recent genetic studies have shown that two cryptic species of Browncheek Blennies occur within the Gulf; the population studied here is the ''Gulf form'' (Lin et al 2009). …”