Correction: Spatial variation and antecedent sea surface temperature conditions influence Hawaiian intertidal community structure.

[This corrects the article DOI: 10.1371/journal.pone.0286136.].

Spatial variation and antecedent sea surface temperature conditions influence Hawaiian intertidal community structure.

Global sea surface temperatures (SSTs) are increasing, and in Hawai'i, rates of ocean warming are projected to double by the end of the 21st century. However, current nearshore warming trends and their possible impacts on intertidal communities are not well understood. This study represents the first investigation into the possible effects of rising SST on intertidal algal and invertebrate communities across the Main Hawaiian Islands (MHI). By utilizing citizen-science data coupled with high-resolution, daily SST satellite measurements from 12 intertidal sites across the MHI from 2004-2019, the response of intertidal algal and invertebrate abundance and community diversity to changes in SST was investigated across multiple spatial scales. Results show high rates of SST warming (0.40°C Decade-1) over this study's timeframe, similar to predicted rates of warming for Hawai'i by the end of the 21st century. Changes in abundance and diversity in response to SST were variable among intertidal sites, but differences in antecedent SST among intertidal sites were significantly associated with community dissimilarity. In addition, a statistically significant positive relationship was found between SST and Simpson's diversity index, and a significant relationship was also found between SST and the abundance of six dominant taxa. For five of these six dominant taxa, antecedent SSTs over the 6-12 months preceding sampling were the most influential for describing changes to abundance. The increase in community diversity in response to higher SSTs was best explained by temperatures in the 10 months preceding sampling, and the resultant decreased abundance of dominant turf algae. These results highlight rapidly warming nearshore SSTs in Hawai'i and the longer-term effects of antecedent SSTs as significant drivers of change within Hawaiian intertidal communities. Therefore, we suggest that future research and management should consider the possibility of lagging effects of antecedent SST on intertidal communities in Hawai'i and elsewhere.

Shallow water hydroids (Cnidaria, Hydrozoa) from the 2002 NOWRAMP cruise to the Northwestern Hawaiian Islands.

Forty-two species of hydroids, excluding stylasterids, are reported in the present collection from the Northwestern Hawaiian Islands. Of these, four are anthoathecates and 38 are leptothecates. Among the latter, Sertularella affinicostata and Monotheca gibbosa are described as new species. The binomen Halopteris longibrachia is proposed as a new replacement name for Plumularia polymorpha var. sibogae Billard, 1913, an invalid junior primary homonym of P. sibogae Billard, 1911. Based largely on evidence from earlier molecular phylogenies, the genus Disertasia Neppi, 1917 is resurrected to accommodate species including Dynamena crisioides Lamouroux, 1824, Sertularia disticha Bosc, 1802, and Sia. moluccana Pictet, 1893. Sertularella robusta Coughtrey, 1876 is an invalid junior primary homonym of Sla. gayi var. robusta Allman, 1874a, and has been replaced here by the binomen Sla. quasiplana Trebilcock, 1928, originally described as Sla. robusta var. quasiplana Trebilcock, 1928. Clytia hummelincki (Leloup, 1935) is referred to the synonymy of its senior subjective synonym, C. brevithecata (Thornely, 1900). Following Reversal of Precedence provisions in the International Code of Zoological Nomenclature to preserve prevailing usage of binomena, the familiar names Sia. disticha Bosc, 1802 (also known as Dynamena disticha) and Lytocarpia phyteuma (Stechow, 1919b) are designated nomena protecta and assigned precedence over their virtually unknown senior synonyms Hydra quinternana Bosc, 1797 and Aglaophenia clavicula Whitelegge, 1899, respectively, names now reduced to the status of nomena oblita. Twenty species are reported for the first time from Hawaii [Eudendrium merulum Watson, 1985, Phialellidae (undetermined), Hebella sp., Hebellopsis scandens (Bale, 1888), H. sibogae Billard, 1942, Clytia brevithecata, C. linearis (Thornely, 1900), C. cf. noliformis (McCrady, 1859), Halecium sp., Sla. affinicostata, Sla. angulosa Bale, 1894, Pasya heterodonta (Jarvis, 1922), Tridentata orthogonalis (Gibbons Ryland, 1989), Pycnotheca producta (Bale, 1881), Monotheca gibbosa, H. longibrachia, A. postdentata Billard, 1913, A. suensonii Jderholm, 1896, A. whiteleggei Bale, 1888, and L. flexuosa (Lamouroux, 1816)]. Sertularia orthogonalis, reported for only the third time worldwide, is assigned to the genus Tridentata Stechow, 1920. Hydroids of the NOWRAMP 2002 collection consisted largely of presumptive widespread species, with over 75% of them having been reported elsewhere in the tropical Indo-west Pacific region.

Species Radiations in the Sea: What the Flock?

Species flocks are proliferations of closely-related species, usually after colonization of depauperate habitat. These radiations are abundant on oceanic islands and in ancient freshwater lakes, but rare in marine habitats. This contrast is well documented in the Hawaiian Archipelago, where terrestrial examples include the speciose silverswords (sunflower family Asteraceae), Drosophila fruit flies, and honeycreepers (passerine birds), all derived from one or a few ancestral lineages. The marine fauna of Hawai'i is also the product of rare colonization events, but these colonizations usually yield only one species. Dispersal ability is key to understanding this evolutionary inequity. While terrestrial fauna rarely colonize between oceanic islands, marine fauna with pelagic larvae can make this leap in every generation. An informative exception is the marine fauna that lack a pelagic larval stage. These low-dispersal species emulate a "terrestrial" mode of reproduction (brooding, viviparity, crawl-away larvae), yielding marine species flocks in scattered locations around the world. Elsewhere, aquatic species flocks are concentrated in specific geographic settings, including the ancient lakes of Baikal (Siberia) and Tanganyika (eastern Africa), and Antarctica. These locations host multiple species flocks across a broad taxonomic spectrum, indicating a unifying evolutionary phenomenon. Hence marine species flocks can be singular cases that arise due to restricted dispersal or other intrinsic features, or they can be geographically clustered, promoted by extrinsic ecological circumstances. Here, we review and contrast intrinsic cases of species flocks in individual taxa, and extrinsic cases of geological/ecological opportunity, to elucidate the processes of species radiations.

Barcoding Techniques Help Tracking the Evolutionary History of the Introduced Species Pennaria disticha (Hydrozoa, Cnidaria).

The Christmas tree hydroid Pennaria disticha is listed as one of the most common introduced species in Hawaii. Firstly reported in Kaneohe Bay (Oahu) in 1928, it is now established throughout the entire archipelago, including the Northwestern Hawaiian Islands, a U.S. National Monument and World Heritage site. The Hawaiian population of P. disticha has also been reported as being the source of further introductions to Palmyra Atoll in the U.S. Line Islands. Using a phylogenetic hypothesis based on a 611 base pair fragment of the mitochondrial 16S barcoding gene, we demonstrate that P. disticha is a complex of cryptic species, rather than one species with cosmopolitan distribution. We also show that in Hawaii there are three species of Pennaria, rather than one introduced species. Two of these species share haplotypes with specimens from distant locations such as Florida and Panama and may have been introduced, possibly from the Atlantic Ocean. A third species could either represent a lineage with nearly cosmopolitan distribution, or another introduced species. Our dataset refutes the widely accepted idea that only one lineage of P. disticha is present in Hawaii. On the contrary, P. disticha in Hawaii may be the outcome of multiple independent introductions of several morphologically undistinguishable cryptic lineages. Our results uncover an unsuspected complexity within the very common hydroid P. disticha, and highlight the need for routine use of molecular tools, such as DNA barcoding, to improve the identification and recognition of non-indigenous species.

Speciation in the sea: overview of the symposium and discussion of future directions.

Speciation remains one of the most controversial and least understood topics in evolution. About 75% of the earth's surface is covered by oceans. However, most of what we currently know about speciation is strongly biased toward terrestrial and freshwater organisms. Here, we discuss some of the major advances of the past two decades in our understanding of speciation in the sea and outline promising future directions that were gathered during the 2011 SICB Symposium "Speciation in the Sea."

Defining Boundaries for Ecosystem-Based Management: A Multispecies Case Study of Marine Connectivity across the Hawaiian Archipelago.

Determining the geographic scale at which to apply ecosystem-based management (EBM) has proven to be an obstacle for many marine conservation programs. Generalizations based on geographic proximity, taxonomy, or life history characteristics provide little predictive power in determining overall patterns of connectivity, and therefore offer little in terms of delineating boundaries for marine spatial management areas. Here, we provide a case study of 27 taxonomically and ecologically diverse species (including reef fishes, marine mammals, gastropods, echinoderms, cnidarians, crustaceans, and an elasmobranch) that reveal four concordant barriers to dispersal within the Hawaiian Archipelago which are not detected in single-species exemplar studies. We contend that this multispecies approach to determine concordant patterns of connectivity is an objective and logical way in which to define the minimum number of management units and that EBM in the Hawaiian Archipelago requires at least five spatially managed regions.

Host shift and speciation in a coral-feeding nudibranch.

While the role of host preference in ecological speciation has been investigated extensively in terrestrial systems, very little is known in marine environments. Host preference combined with mate choice on the preferred host can lead to population subdivision and adaptation leading to host shifts. We use a phylogenetic approach based on two mitochondrial genetic markers to disentangle the taxonomic status and to investigate the role of host specificity in the speciation of the nudibranch genus Phestilla (Gastropoda, Opisthobranchia) from Guam, Palau and Hawaii. Species of the genus Phestilla complete their life cycle almost entirely on their specific host coral (species of Porites, Goniopora and Tubastrea). They reproduce on their host coral and their planktonic larvae require a host-specific chemical cue to metamorphose and settle onto their host. The phylogenetic trees of the combined cytochrome oxidase I and ribosomal 16S gene sequences clarify the relationship among species of Phestilla identifying most of the nominal species as monophyletic clades. We found a possible case of host shift from Porites to Goniopora and Tubastrea in sympatric Phestilla spp. This represents one of the first documented cases of host shift as a mechanism underlying speciation in a marine invertebrate. Furthermore, we found highly divergent clades within Phestilla sp. 1 and Phestilla minor (8.1-11.1%), suggesting cryptic speciation. The presence of a strong phylogenetic signal for the coral host confirms that the tight link between species of Phestilla and their host coral probably played an important role in speciation within this genus.