Three routes to crypsis: Stasis, convergence, and parallelism in the Mastigias species complex (Scyphozoa, Rhizostomeae).

Evolutionary inference can be complicated by morphological crypsis, particularly in open marine systems that may rapidly dissipate signals of evolutionary processes. These complications may be alleviated by studying systems with simpler histories and clearer boundaries, such as marine lakes-small bodies of seawater entirely surrounded by land. As an example, we consider the jellyfish Mastigias spp. which occurs in two ecotypes, one in marine lakes and one in coastal oceanic habitats, throughout the Indo-West Pacific (IWP). We tested three evolutionary hypotheses to explain the current distribution of the ecotypes: (H1) the ecotypes originated from an ancient divergence; (H2) the lake ecotype was derived recently from the ocean ecotype during a single divergence event; and (H3) the lake ecotype was derived from multiple, recent, independent, divergences. We collected specimens from 21 locations throughout the IWP, reconstructed multilocus phylogenetic and intraspecific relationships, and measured variation in up to 40 morphological characters. The species tree reveals three reciprocally monophyletic regional clades, two of which contain ocean and lake ecotypes, suggesting repeated, independent evolution of coastal ancestors into marine lake ecotypes, consistent with H3; hypothesis testing and an intraspecific haplotype network analysis of samples from Palau reaffirms this result. Phylogenetic character mapping strongly correlates morphology to environment rather than lineage (r=0.7512, p<0.00001). Considering also the deeper relationships among regional clades, morphological similarity in Mastigias spp. clearly results from three separate patterns of evolution: morphological stasis in ocean medusae, convergence of lake morphology across distinct species and parallelism between lake morphologies within species. That three evolutionary routes each result in crypsis illustrates the challenges of interpreting evolutionary processes from patterns of biogeography and diversity in the seas. Identifying cryptic species is only the first step in understanding these processes; an equally important second step is exploring and understanding the processes and patterns that create crypsis.

Comparative phylogeography of sympatric sister species, Clevelandia ios and Eucyclogobius newberryi (Teleostei, Gobiidae), across the California Transition Zone.

It is paradigmatic in marine species that greater dispersal ability often, but not always, results in greater gene flow and less population structure. Some of the exceptions may be attributable to studies confounded by comparison of species with dissimilar evolutionary histories, i.e. co-occurring species that are not closely related or species that are closely related but allopatric. Investigation of sympatric sister species, in contrast, should allow differences in phylogeographic structure to be attributed reliably to recently derived differences in dispersal ability. Here, using mitochondrial DNA control region sequence, we first confirm that Clevelandia ios and Eucyclogobius newberryi are sympatric sister taxa, then demonstrate considerably shallower phylogeographic structure in C. ios than in E. newberryi. This shallower phylogeographic structure is consistent with the higher dispersal ability of C. ios, which most likely results from the interaction of habitat and life-history differences between the species. We suggest that the paradigm will be investigated most rigorously by similar studies of other sympatric sister species, appended by thorough ecological studies, and by extending this sister-taxon approach to comparative phylogeographic studies of monophyletic clades of sympatric species.

Phylogeography of the tidewater goby, Eucyclogobius newberryi (Teleostei, Gobiidae), in coastal California.

The tidewater goby, Eucyclogobius newberryi, inhabits discrete, seasonally closed estuaries and lagoons along approximately 1500 km of California coastline. This species is euryhaline but has no explicit marine stage, yet population extirpation and recolonization data suggest tidewater gobies disperse intermittently via the sea. Analyses of mitochondrial control region and cytochrome b sequences demonstrate a deep evolutionary bifurcation in the vicinity of Los Angeles that separates southern California populations from all more northerly populations. Shallower phylogeographic breaks, in the vicinities of Seacliff, Point Buchon, Big Sur, and Point Arena segregate the northerly populations into five groups in three geographic clusters: the Point Conception and Ventura groups between Los Angeles and Point Buchon, a lone Estero Bay group from central California, and San Francisco and Cape Mendocino groups from northern California. The phylogenetic relationships between and patterns of molecular diversity within the six groups are consistent with repeated, and sometimes rapid, northward and southward range expansions out of central California caused by Quaternary climate change. Plio-Pleistocene tectonism, Quaternary coastal geography and hydrography, and historical human activities probably also influenced the modern geographic and genetic structure of E. newberryi. The phylogeography of E. newberryi is concordant with phylogeographic patterns in several other coastal California taxa, suggesting common extrinsic factors have had similar effects on different species. However, there is no evidence of a phylogeographic break coincident with a biogeographic boundary at Point Conception.

Field preservation of marine invertebrate tissue for DNA analyses.

Successful preservation of tissue samples is a prerequisite for long field studies in remote areas. However, there is little published information concerning field preservation of marine invertebrate tissues for DNA analyses. This omission is significant because marine biodiversity is centered in the Indo-Pacific, where immediate DNA analysis is often impossible. Consequently, we used an assay based on polymerase chain reaction (PCR) to examine the effect of five storage solutions and three temperature regimens on the degradation of DNA from four common classes of marine invertebrates (Anthozoa, Gastropoda, Polychaeta, and Scyphozoa). Control samples were cryopreserved. Storage solution and the type of tissue preserved were the best predictors of preservation success. The length of time in storage and the storage temperature also affected the preservation of DNA. A field test demonstrates that a solution of dimethylsulfoxide and sodium chloride (DMSO-NaCl) preserves a wide range of tissues for DNA analyses and is very simple to use in remote field locations.