Robert J. Toonen

Preservation of corals in salt-saturated DMSO buffer is superior to ethanol for PCR experiments

Specimen collection is time consuming and expensive, yet few laboratories test preservation methods before setting out on field expeditions. The most common preservation buffer used for coral specimens is >70% EtOH. However, alternatives exist that are less flammable, easier to ship, and are widely used in other taxa. Here, we compare the effects of salt-saturated DMSO (SSD) and EtOH preservation buffers on post-extraction DNA quantity and quality. We found that soft tissue integrity was better maintained and higher quantities of DNA were extracted from EtOH-preserved specimens; however, by all other measures, SSD was a superior preservative to EtOH. Extractions of SSD-preserved specimens resulted in higher molecular weight DNA, higher PCR success, and more efficient amplification than specimens preserved in EtOH. Our results show that SSD is generally a superior preservative to EtOH for specimens destined for PCR studies, but species-specific differences indicate that preservation comparisons should be undertaken before collection and storage of samples.

Coming out of the starting blocks: extended lag time rearranges genetic diversity in introduced marine fishes of Hawai‘i

Biological invasions with known histories are rare, especially in the sea, and empirical studies of the genetic consequences are even rarer. Fifty-five years ago, the state of Hawai‘i began a remarkable, if unintentional, ‘experiment’ with the introduction of three reef fishes, Lutjanus fulvus, Cephalopholis argus and Lutjanus kasmira. All have since expanded from the initial introduction of 2204 to 3163 individuals; however, historical records show that initially L. fulvus remained scarce, C. argus had modest population expansion and L. kasmira experienced rapid population growth. The consequences of differential population growth rates are apparent in F-statistics: Hawaiian L. fulvus demonstrate strong and significant haplotype frequency shifts from the founder location (FST = 0.449), C. argus shows low but significant differentiation (FST = 0.066) and L. kasmira is nearly identical to the founder location (FST = 0.008). All three species had higher mtDNA diversity in the introduced range, which can be explained by multiple sources for L. fulvus and L. kasmira, but not for C. argus. We conclude that lag time before population expansion, in conjunction with genetic drift, has defined the genetic architecture of these three species in the introduced range.

Cryptic species obscure introduction pathway of the blue Caribbean sponge (Haliclona (Soestella) caerulea), (order: Haplosclerida) to Palmyra Atoll, Central Pacific.

Cryptic species are widespread across the phylum Porifera making the identification of non-indigenous species difficult, an issue not easily resolved by the use of morphological characteristics. The widespread order Haplosclerida is a prime example due to limited and plastic morphological features. Here, we study the reported introduction of Haliclona (Soestella) caerulea from the Caribbean to Palmyra Atoll via Hawaiʻi using morphological characteristics and genetic analyses based on one nuclear (18s rDNA) and three mitochondrial (COI, the barcoding COI extension (COI ext.) and rnl rDNA) markers. Despite no clear division in lengths of the oxea spicules between the samples, both mtDNA and nDNA phylogenetic trees supported similar topologies resolving two distinct clades. Across the two clades, the concatenated mtDNA tree resolved twelve subclades, with the COI ext. yielding most of the variability between the samples. Low sequence divergence values (0.68%) between two of the subclades indicate that the same species is likely to occur at Palmyra, Hawaiʻi and the Caribbean, supporting the hypothesis that H. caerulea was introduced to Palmyra from the Caribbean, although whether species came directly from the Caribbean to Palmyra or from Hawaiʻi remains unresolved. Conversely, the pattern of highly divergent cryptic species supports the notion that traditionally used spicule measurements are taxonomically unreliable in this group. This study illustrates how understanding the scale of within- as opposed to between-species level genetic variation is critical for interpreting biogeographic patterns and inferring the origins of introduced organisms.

Isolation and characterization of polymorphic microsatellite and COI loci from the whelk Kelletia kelletii

There is considerable interest in the genetic structure of Kelletia kelletii because of its economic, ecological and scientific importance. To that end, we developed species‐specific primers which amplify mitochondrial cytochrome c oxidase subunit I as well as 13 hypervariable nuclear microsatellite loci. Using dye‐labelled primers, the microsatellite loci can be co‐amplified in two multiplex polymerase chain reactions and scored simultaneously on an automated sequencer.

New report of nudibranch predators of the invasive octocoral Carijoa riisei in the Main Hawaiian Islands

In 1972, an azooxanthellate octocoral never before seen in Hawaii (identified by F. M. Bayer as Telesto = Carijoa riisei) was discovered within the fouling community in Pearl Harbor. C. riisei was soon discovered on other islands, and was recently reported to have dramatically impacted the Hawaiian deep reef coral community below 60 m (Kahng and Grigg 2005). To date, studies on C. riisei and its associated microcommunity have failed to identify any predators in Hawaii (Thomas 1979). Here we report two nudibranch predators (Mollusca: Nudibranchia) of C. riisei recently found in Hawaii: the dendronotid nudibranch Tritoniopsis elegans (Fig. 1a) and the aeolid nudibranch Phyllodesmium poindimiei (Fig. 1b). Both have been observed apparently feeding on C. riisei colonies in the field, and these observations have been confirmed in laboratory feeding assays. These species are not reported in any previous marine invertebrate surveys from Hawaii (Eldredge and DeFelice 2002). Both were first collected from Hawaii in 1995 (C. Pittman, personal communication), and are now abundant within certain locations inhabited by C. riisei. Laboratory feeding trials with the native octocorals Sinularia densa and Sarcothelia edmondsoni in the presence and absence of C. riisei, demonstrated that P. poindimiei quickly starves in the absence of C. riisei as prey. A broad survey of other Hawaiian corals showed similar results, confirming that P. poindimiei is an obligate predator of Carijoa (Rudman 1991). In contrast, T. elegans appears to be a generalist octocoral predator which preys readily on C. riisei, but also feeds on S. densa, and S. edmondsoni when C. riisei is absent. Given the cryptic nature of these nudibranchs, it is quite possible that they were missed in previous surveys of Hawaiian marine fauna. However, the highly specialized feeding ecology of P. poindimiei suggests that it most likely followed C. riisei in colonizing Hawaii.

The implementation of rare events logistic regression to predict the distribution of mesophotic hard corals across the main Hawaiian Islands

Predictive habitat suitability models are powerful tools for cost-effective, statistically robust assessment of the environmental drivers of species distributions. The aim of this study was to develop predictive habitat suitability models for two genera of scleractinian corals (Leptoserisand Montipora) found within the mesophotic zone across the main Hawaiian Islands. The mesophotic zone (30–180 m) is challenging to reach, and therefore historically understudied, because it falls between the maximum limit of SCUBA divers and the minimum typical working depth of submersible vehicles. Here, we implement a logistic regression with rare events corrections to account for the scarcity of presence observations within the dataset. These corrections reduced the coefficient error and improved overall prediction success (73.6% and 74.3%) for both original regression models. The final models included depth, rugosity, slope, mean current velocity, and wave height as the best environmental covariates for predicting the occurrence of the two genera in the mesophotic zone. Using an objectively selected theta (“presence”) threshold, the predicted presence probability values (average of 0.051 for Leptoseris and 0.040 for Montipora) were translated to spatially-explicit habitat suitability maps of the main Hawaiian Islands at 25 m grid cell resolution. Our maps are the first of their kind to use extant presence and absence data to examine the habitat preferences of these two dominant mesophotic coral genera across Hawai‘i.

Geopolitical species revisited: genomic and morphological data indicate that the roundtail chub Gila robusta species complex (Teleostei, Cyprinidae) is a single species

The Gila robusta species complex in the Lower Colorado River Basin has a complicated taxonomic history. Recent authors have separated this group into three nominal taxa, G. robusta, G. intermedia, and G. nigra, however aside from location, no reliable method of distinguishing individuals of these species currently exists. To assess relationships within this group, we examined morphology of type specimens and fresh material, and used RADseq methods to assess phylogenetic relationship among these nominal species. Maximum likelihood and Bayesian inference tree building methods reveal high concordance between tree topologies based on the mitochondrial and nuclear datasets. Coalescent SNAPP analysis resolved a similar tree topology. Neither morphological nor molecular data reveal diagnostic differences between these species as currently defined. As such, G. intermedia and G. nigra should be considered synonyms of the senior G. robusta. We hypothesize that climate driven wet and dry cycles have led to periodic isolation of population subunits and subsequent local divergence followed by reestablished connectivity and mixing. Management plans should therefore focus on retaining genetic variability and viability of geographic populations to preserve adaptability to changing climate conditions.