Pygmy Angelfishes Research Articles

Gut microbial communities of hybridising pygmy angelfishes reflect species boundaries

Hybridisation and introgression of eukaryotic genomes can generate new species or subsume existing ones, with direct and indirect consequences for biodiversity. An understudied component of these evolutionary forces is their potentially rapid effect on host gut microbiomes, and whether these pliable microcosms may serve as early biological indicators of speciation. We address this hypothesis in a field study of angelfishes (genus Centropyge), which have one of the highest prevalence of hybridisation within coral reef fish. In our study region of the Eastern Indian Ocean, the parent fish species and their hybrids cohabit and display no differences in their diet, behaviour, and reproduction, often interbreeding in mixed harems. Despite this ecological overlap, we show that microbiomes of the parent species are significantly different from each other in form and function based on total community composition, supporting the division of parents into distinct species, despite the confounding effects of introgression acting to homogenize parent species identity at other molecular markers. The microbiome of hybrid individuals, on the other hand, are not significantly different to each of the parents, instead harbouring an intermediate community composition. These findings suggest that shifts in gut microbiomes may be an early indicator of speciation in hybridising species.

Filling an empty role: first report of cleaning by pygmy angelfishes (<i>Centropyge</i>, Pomacanthidae)

Filling an empty role: first report of cleaning by pygmy angelfishes (<i>Centropyge</i>, Pomacanthidae)

Effect of temperature on hatching success of flameback pygmy angelfish Centropyge aurantonotus eggs

Aquaculture ResearchVolume 51, Issue 3 p. 1303-1306 SHORT COMMUNICATION Effect of temperature on hatching success of flameback pygmy angelfish Centropyge aurantonotus eggs Raoani C. Mendonça, Corresponding Author Raoani C. Mendonça raoani@hotmail.com orcid.org/0000-0001-6629-680X Laboratory of Marine Fishes and Ornamentals (LAPOM), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, Brazil Correspondence Raoani C. Mendonça, Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Rodovia Admar Gonzaga, 1346 Bairro Itacorubi, Florianópolis SC, CEP 88034-001, Brazil. Email: raoani@hotmail.comSearch for more papers by this authorSarah P. Ikebata, Sarah P. Ikebata Laboratory of Marine Fishes and Ornamentals (LAPOM), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, BrazilSearch for more papers by this authorSérgio L. Araújo-Silva, Sérgio L. Araújo-Silva Laboratory of Marine Fishes and Ornamentals (LAPOM), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, BrazilSearch for more papers by this authorJoão V. A. Manhães, João V. A. Manhães Laboratory of Marine Fishes (LAPMAR), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, BrazilSearch for more papers by this authorMônica Y. Tsuzuki, Mônica Y. Tsuzuki Laboratory of Marine Fishes and Ornamentals (LAPOM), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, BrazilSearch for more papers by this author Raoani C. Mendonça, Corresponding Author Raoani C. Mendonça raoani@hotmail.com orcid.org/0000-0001-6629-680X Laboratory of Marine Fishes and Ornamentals (LAPOM), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, Brazil Correspondence Raoani C. Mendonça, Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Rodovia Admar Gonzaga, 1346 Bairro Itacorubi, Florianópolis SC, CEP 88034-001, Brazil. Email: raoani@hotmail.comSearch for more papers by this authorSarah P. Ikebata, Sarah P. Ikebata Laboratory of Marine Fishes and Ornamentals (LAPOM), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, BrazilSearch for more papers by this authorSérgio L. Araújo-Silva, Sérgio L. Araújo-Silva Laboratory of Marine Fishes and Ornamentals (LAPOM), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, BrazilSearch for more papers by this authorJoão V. A. Manhães, João V. A. Manhães Laboratory of Marine Fishes (LAPMAR), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, BrazilSearch for more papers by this authorMônica Y. Tsuzuki, Mônica Y. Tsuzuki Laboratory of Marine Fishes and Ornamentals (LAPOM), Aquaculture Department, Agricultural Sciences Center (CCA), Federal University of Santa Catarina (UFSC), Florianópolis, BrazilSearch for more papers by this author First published: 19 December 2019 https://doi.org/10.1111/are.14443Citations: 2Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume51, Issue3March 2020Pages 1303-1306 RelatedInformation

Thermal influence on the embryonic development and hatching rate of the flameback pygmy angelfish Centropyge aurantonotus eggs.

The flameback pygmy angelfish Centropyge aurantonotus, highly appreciated and valued by the aquarium market, is heavily harvested and traded. Temperature is one of the abiotic factors that has the most influence on fish development, especially in the early stages of life. For captive production, it is essential to know the appropriate environmental parameters for each species. In this sense, this study aimed to evaluate the influence of temperature on the embryonic development and hatching rates of C. aurantonotus incubated at six different temperatures (20, 22, 24, 26, 28, 30°C). Embryonic development events were very similar in terms of morphological and chronological characteristics compared with other species of the genus Centropyge. Incubation time was inversely proportional to temperature. The treatment at 22°C required twice the time of that required by 30°C treatment for hatching to occur. The best incubation temperature range was 24-28°C. Values below 22°C and at 30°C showed lower hatching rates compared with other treatments. Based on these results, the recommended temperature at which to incubate C. aurantonotus eggs is between 24-28°C.

Do ecological traits of low abundance and niche overlap promote hybridisation among coral-reef angelfishes?

Hybridisation among species of coral-reef fish was previously considered to be rare. However, recent studies have revealed that hybridisation is prevalent in coral-reef fish, highlighting the need to understand the causes of this process. The angelfishes (family Pomacanthidae) have the greatest proportion (~ 30%) of hybridising species to date, with 26 species reported to hybridise. The aim of this study was to examine ecological factors (rarity of parent species and niche overlap) that promote hybridisation in terrestrial environments and to test these factors in the marine environment by examining hybridising angelfishes at Christmas Island (Indian Ocean). Three species of pygmy angelfish (Centropyge flavissima, C. eibli, and C. vrolikii) and their hybrids were investigated to address three objectives: (1) to determine temporal and spatial patterns in abundance and whether these patterns are linked to environmental factors; (2) to test for overlapping patterns in habitat use; and (3) to test for overlapping patterns in diet. Based on 14 yr of surveys, C. flavissima was abundant (4.53 individuals per 250 m2 ± 0.66), whereas C. eibli, C. vrolikii, and all hybrid combinations were consistently rare (average abundance < 0.3 per 250 m2 ± 0.03). Parent species and their hybrids were more abundant at 20 m depth compared to 5 m. All species and their hybrids had similar patterns of abundance around Christmas Island, with significantly high abundances evident at the most sheltered sites. Parent species and their hybrids also had similar diets that comprised a mix of green, red, and brown algae. The rarity of parent species, their niche overlap, and the haremic reproductive strategy likely promote hybridisation in angelfishes at Christmas Island. This study provides empirical evidence that hybridisation in reef fishes conforms to terrestrial-based hypothesis, and thus advances our understanding of the processes underlying hybridisation in coral-reef systems.

Whole-genome assembly of the coral reef Pearlscale Pygmy Angelfish (Centropyge vrolikii)

The diversity of DNA sequencing methods and algorithms for genome assemblies presents scientists with a bewildering array of choices. Here, we construct and compare eight candidate assemblies combining overlapping shotgun read data, mate-pair and Chicago libraries and four different genome assemblers to produce a high-quality draft genome of the iconic coral reef Pearlscale Pygmy Angelfish, Centropyge vrolikii (family Pomacanthidae). The best candidate assembly combined all four data types and had a scaffold N50 127.5 times higher than the candidate assembly obtained from shotgun data only. Our best candidate assembly had a scaffold N50 of 8.97 Mb, contig N50 of 189,827, and 97.4% complete for BUSCO v2 (Actinopterygii set) and 95.6% complete for CEGMA matches. These contiguity and accuracy scores are higher than those of any other fish assembly released to date that did not apply linkage map information, including those based on more expensive long-read sequencing data. Our analysis of how different data types improve assembly quality will help others choose the most appropriate de novo genome sequencing strategy based on resources and target applications. Furthermore, the draft genome of the Pearlscale Pygmy angelfish will play an important role in future studies of coral reef fish evolution, diversity and conservation.

Breakdown in assortative mating leads to hybrid swarm in pygmy angelfishes

Breakdown in assortative mating leads to hybrid swarm in pygmy angelfishes

Body shape convergence driven by small size optimum in marine angelfishes.

Convergent evolution of small body size occurs across many vertebrate clades and may reflect an evolutionary response to shared selective pressures. However it remains unclear if other aspects of phenotype undergo convergent evolution in miniaturized lineages. Here we present a comparative analysis of body size and shape evolution in marine angelfishes (Pomacanthidae), a reef fish family characterized by repeated transitions to small body size. We ask if lineages that evolve small sizes show convergent evolution in body shape. Our results reveal that angelfish lineages evolved three different stable size optima with one corresponding to the group of pygmy angelfishes (Centropyge). Then, we test if the observed shifts in body size are associated with changes to new adaptive peaks in shape. Our data suggest that independent evolution to small size optima have induced repeated convergence upon deeper body and steeper head profile in Centropyge These traits may favour manoeuvrability and visual awareness in these cryptic species living among corals, illustrating that functional demands on small size may be related to habitat specialization and predator avoidance. The absence of shape convergence in large marine angelfishes also suggests that more severe requirements exist for small than for large size optima.

Angelfishes, Paper Tigers, and the Devilish Taxonomy of the Centropyge flavissima Complex.

The pygmy angelfishes (genus Centropyge) provide numerous examples of discordance between color morphology, taxonomy, and evolutionary genetic lineages. This discordance is especially evident in the Centropyge flavissima complex, which includes three primary color morphs, three previously recognized species (C. flavissima, Centropyge eibli, and Centropyge vrolikii) and three distinct mitochondrial (mtDNA) lineages that do not align with species designations. Our previous research showed that the putative C. flavissima arose independently in the Indian and Pacific Oceans, and the three mtDNA lineages align with geography rather than species assignments. Here, we add 157 specimens to the previous dataset of 291 specimens, spread across a greater geographic range, to pinpoint the distribution of mtDNA lineages and color morphs. We found that the mtDNA lineages show remarkably strong geographic boundaries corresponding to the Indian Ocean, Central-West Pacific, and Central-South Pacific. We also test the validity of the "Black Tiger Centropyge" in the C. flavissima species complex, a taxonomic oddity that is restricted to shoals and atolls off the coast of northwestern Australia, and the newly named Centropyge cocosensis assigned to the C. flavissima lineage in the Indian Ocean. We conclude that the Black Tiger Centropyge is not a valid species but rather an intermediate between sympatric color morphs that correspond to the putative species C. eibli and C. vrolikii Our greater sampling efforts also do not support the genetic distinctiveness of C. cocosensis given shared mtDNA haplotypes with the sympatric C. eibli and C. vrolikii, but instead we find conflicting lines of evidence concerning the taxonomy of this group. We urge caution and taxonomic restraint until the true nature of this species complex can be revealed.

Lemonpeel (Centropyge flavissima) and yellow (C. heraldi) pygmy angelfishes each consist of two geographically isolated sibling species

Genetic variation was examined in two complex cases of Indo-Pacific pygmy angelfishes (genus Centropyge; Pomacanthidae). The lemonpeel pygmy angelfish C. flavissima (Cuvier and Valenciennes) has a geographically disjunct Indian vs. Pacific distribution and the individuals from these two regions differ by their colour patterns. Previous research on C. flavissima has shown mitochondrial introgression from two related species, C. eibli in the eastern Indian Ocean and C. vrolikii in the Pacific Ocean. Using the 16S rDNA and the CO1 gene as phylogeographic markers, we found no mitochondrial haplotypes in common between Indian Ocean C. flavissima and C. eibli, confirming partial genetic isolation, albeit recent. Also, we found substantial genetic differences between Indian and Pacific C. flavissima populations at the nuclear ETS-2 intron locus. The Indian Ocean form of C. flavissima, thus geographically isolated by >2000 km distance from its Pacific Ocean counterpart, is described as a new species, Centropyge cocosensis sp. nov. Centropyge cocosensis sp. nov. differs in appearance from C. flavissima in having a conspicuous blue iris and a fainter, bluish eye ring. We also found that the yellow pygmy angelfish C. heraldi Woods and Schultz consists of two genetically distinct entities, one distributed widely in the northern tropical Indo-West Pacific, the other distributed in the southern Pacific Ocean. The name originally given to the blackfin pygmy angelfish, C. woodheadi Kuiter, is here resurrected to designate the latter.

Complete mitogenomes of Whitetail angelfish (Centropyge flavicauda) and Orangeback angelfish (Centropyge acanthops) (Teleostei: Pomacanthidae)

Whitetail Angelfish (Centropyge flavicauda) and Orangeback Angelfish (Centropyge acanthops) are known as pygmy angelfish due to their small body size (usually less than two inches). In this study, we used the next-generation sequencing method to deduce two complete mitogenomes of C. flavicauda and C. acanthops for the first time. The assembled mitogenome, consisting of 16 747 bp and 16 748 bp, was showing 99.2% identity each other. Both mitogenome follow the typical vertebrate arrangement, including 13 protein coding genes, 22 transfer RNAs, two ribosomal RNAs genes and a non-coding control region of D-loop. D-loop contains 895 bp in C. flavicauda and 896 bp in C. acanthops and locates between tRNA-Pro and tRNA-Phe. The overall GC content is 46.4% for C. flavicauda and C. acanthops. Complete mitogenomes of C. flavicauda and C. acanthops provide essential and important DNA molecular data for phylogenetic and evolutionary analysis for marine angelfish.

Isolation and characterization of fifteen microsatellite loci in two-spined angelfish Centropyge bispinosa (family Pomacanthidae) with cross-amplification success in four Centropyge congeners

Centropyge bispinosa is one of the most frequently coral reef fish exported through the aquarium trade. We developed fifteen microsatellite markers to evaluate possible distinct breeding stocks throughout its Indo-Pacific distribution range. Number of alleles varied from 2 to 50 per locus, observed and expected heterozygosities ranged from 0.486 to 0.953 and 0.482 to 0.974 respectively. Significant deviations from HWE were detected in two loci. Cross-amplifications were tested in four congener species: C. loriculus, C. bicolor, C. flavissima and C. vroliki. The 15 new microsatellite loci will be helpful tools for the identification of breeding units, connectivity studies, as well as phylogenetic relationships among pygmy angelfishes.

Evolution of pygmy angelfishes: Recent divergences, introgression, and the usefulness of color in taxonomy

The pygmy angelfishes (genus Centropyge, family Pomacanthidae) are brightly colored species that occupy reef habitats in every tropical ocean. Some species are rarely observed because they occur below conventional scuba depths. Their striking coloration can command thousands of U.S. dollars in the aquarium trade, and closely related species are often distinguished only by coloration. These factors have impeded phylogenetic resolution, and every phylogeographic survey to date has reported discordance between coloration, taxonomy, and genetic partitions. Here we report a phylogenetic survey of 29 of the 34 recognized species (N=94 plus 23 outgroups), based on two mtDNA and three nuclear loci, totaling 2272bp. The resulting ML and Baysian trees are highly concordant and indicate that the genus Centropyge is paraphyletic, consistent with a previous analysis of the family Pomacanthidae. Two recognized genera (Apolemichthys and Genicanthus) nest within Centropyge, and two subgenera (Xiphypops and Paracentropyge) comprise monophyletic lineages that should be elevated to genus level. Based on an age estimate of 38Ma for the family Pomacanthidae, Centropyge diverged from the closest extant genus Pygoplites about 33Ma, three deep lineages within Centropyge diverged about 18–28Ma, and four species complexes diverged 3–12Ma. However, in 11 of 13 cases, putative species in these complexes are indistinguishable based on morphology and genetics, being defined solely by coloration. These cases indicate either emerging species or excessive taxonomic splitting based on brightly colored variants.

Twisted sister species of pygmy angelfishes: discordance between taxonomy, coloration, and phylogenetics

The delineation of reef fish species by coloration is problematic, particularly for the pygmy angelfishes (genus Centropyge), whose vivid colors are sometimes the only characters available for taxonomic classification. The Lemonpeel Angelfish (Centropyge flavissima) has Pacific and Indian Ocean forms separated by approximately 3,000 km and slight differences in coloration. These disjunct populations hybridize with Eibl’s Angelfish (Centropyge eibli) in the eastern Indian Ocean and the Pearl-Scaled Angelfish (Centropyge vrolikii) in the western Pacific. To resolve the evolutionary history of these species and color morphs, we employed mitochondrial DNA (mtDNA) cytochrome b and three nuclear introns (TMO, RAG2, and S7). Phylogenetic analyses reveal three deep mtDNA lineages (d = 7.0–8.3 %) that conform not to species designation or color morph but to geographic region: (1) most Pacific C. flavissima plus C. vrolikii, (2) C. flavissima from the Society Islands in French Polynesia, and (3) Indian Ocean C. flavissima plus C. eibli. In contrast, the nuclear introns each show a cluster of closely related alleles, with frequency differences between the three geographic groups. Hence, the mtDNA phylogeny reveals a period of isolation (ca. 3.5–4.2 million years) typical of congeneric species, whereas the within-lineage mtDNA ΦST values and the nuclear DNA data reveal recent or ongoing gene flow between species. We conclude that an ancient divergence of C. flavissima, recorded in the non-recombining mtDNA, was subsequently swamped by introgression and hybridization in two of the three regions, with only the Society Islands retaining the original C. flavissima haplotypes among our sample locations. Alternatively, the yellow color pattern of C. flavissima may have appeared independently in the central Pacific Ocean and eastern Indian Ocean. Regardless of how the pattern arose, C. flavissima seems to be retaining species identity where it interbreeds with C. vrolikii and C. eibli, and sexual or natural selection may help to maintain color differences despite apparent gene flow.

Evolution of high trophic diversity based on limited functional disparity in the feeding apparatus of marine angelfishes (f. Pomacanthidae).

The use of biting to obtain food items attached to the substratum is an ecologically widespread and important mode of feeding among aquatic vertebrates, which rarely has been studied. We did the first evolutionary analyses of morphology and motion kinematics of the feeding apparatus in Indo-Pacific members of an iconic family of biters, the marine angelfishes (f. Pomacanthidae). We found clear interspecific differences in gut morphology that clearly reflected a wide range of trophic niches. In contrast, feeding apparatus morphology appeared to be conserved. A few unusual structural innovations enabled angelfishes to protrude their jaws, close them in the protruded state, and tear food items from the substratum at a high velocity. Only one clade, the speciose pygmy angelfishes, showed functional departure from the generalized and clade-defining grab-and-tearing feeding pattern. By comparing the feeding kinematics of angelfishes with wrasses and parrotfishes (f. Labridae) we showed that grab-and-tearing is based on low kinematics disparity. Regardless of its restricted disparity, the grab-and-tearing feeding apparatus has enabled angelfishes to negotiate ecological thresholds: Given their widely different body sizes, angelfishes can access many structurally complex benthic surfaces that other biters likely are unable to exploit. From these surfaces, angelfishes can dislodge sturdy food items from their tough attachments. Angelfishes thus provide an intriguing example of a successful group that appears to have evolved considerable trophic diversity based on an unusual yet conserved feeding apparatus configuration that is characterized by limited functional disparity.

Captive hybridization of two geographically isolated pygmy angelfish species,Centropyge fisheriandCentropyge resplendens

This study documents the rearing of two pygmy angelfish species, Centropyge fisheri and Centropyge resplendens, and the early life history and reproduction of their hybrid offspring. A C. fisheri female, collected from Hawaii, and a C. resplendens male, captive-bred from parental stock collected from Ascension Island, were maintained at the hatchery facility for 7 months. Continuous spawning was achieved at a photoperiod cycle of 14L:10D and a water temperature of 26.5 degrees C, range +/-1 degrees C. Over the 110 day period, the C. fisheri female spawned 102 times, 57% of which resulted in embryos (fertilized eggs). The mean +/-s.d. fecundity per spawn was 730 +/- 459 eggs (range 52-1967). Fertility (% eggs that developed into embryos) of all eggs that were preserved was 22.4 +/- 25.6%. A total of 235 hybrid juveniles were raised through metamorphosis with an average larval survival of 16.4%. Eight F(1) hybrid juveniles isolated for further study began to display signs of reproductive behaviour c. 300 days post-hatch (dph). Spawn resulting in non-fertile eggs were first obtained 319 dph, and fertilized eggs developing into embryos were obtained after 411 dph from at least two female individuals. While no attempt was made at rearing the F(2) larvae, embryo and larval development were normal up to 8 dph. Reproduction and development observed for all hybrid generations in this study were normal, similar to other Centropyge species and indicates a very close phylogenetic relationship between what are currently considered distinct species, e.g. C. fisheri and C. resplendens.

Evidence of a geographically variable competitive mimicry relationship in coral reef fishes

AbstractIn Kimbe Bay, Papua New Guinea, juvenile surgeonfish Acanthurus pyroferus have been shown to gain access to food resources defended by the damselfish Plectroglyphidodon lacrymatus by mimicking a pygmy angelfish, Centropyge vrolikii, that does not compete with the damsel for food. I tested whether A. pyroferus juveniles gain the same competitive advantage from mimicking a different pygmy angelfish, Centropyge flavissima, in Moorea, French Polynesia. Through abundance and substrate surveys, behavioral observations and stomach content analyses, I demonstrate that in Moorea, mimicry of Ce. flavissima does not provide A. pyroferus with access to damselfish Stegastes nigricans territories; Ce. flavissima models are always attacked upon territory entry and A. pyroferus mimics avoid damsel territories. Damselfish aggression toward the model angelfish cannot be attributed to overabundance of the deceptive mimic; instead, aggression can best be explained by the fact that Ce. flavissima competes with damsels in Moorea by consuming their algal turfs, making them inappropriate models for competitive mimics. Juveniles of many Indo‐Pacific surgeonfishes appear to mimic pygmy angelfishes; I suggest that these mimics' success in gaining access to damselfish territories is geographically variable and may be determined by the extent to which mimics, models and receivers overlap in resource use at a given site. This mimicry complex may thus present an excellent illustration of the geographic mosaic model of coevolution.

Shallow mtDNA Coalescence in Atlantic Pygmy Angelfishes (Genus Centropyge) Indicates a Recent Invasion from the Indian Ocean

Pygmy angelfishes (genus Centropyge) are widespread and species-rich in the Indo-Pacific, but only three species are recognized in the Atlantic: Centropyge resplendens on the Mid-Atlantic Ridge, Centropyge argi in the Caribbean, and Centropyge aurantonotus in Brazil and the southern Caribbean. Atlantic species are distinguished only by color patterns and are very similar to Centropyge acanthops (Cac) in the western Indian Ocean, raising the possibility that pygmy angelfish recently invaded the Atlantic Ocean via southern Africa. To test this zoogeographic hypothesis, we compared a 454-bp segment of the mitochondrial DNA (mtDNA) control region among pygmy angelfishes of the subgenus Xiphypops, which includes the three Atlantic species, the Indian Ocean species, and an Indo-Pacific species [Centropyge fisheri (Cfi)]. The Indian Ocean species Cac is closest to the Atlantic species (d = 0.059) relative to Cfi (d = 0.077). The mtDNA genealogy indicates a colonization pathway from the Indian Ocean directly to the West Atlantic, followed by at least two waves of dispersal to the Mid-Atlantic Ridge. The gene tree for the three Atlantic species is polyphyletic, raising questions about taxonomic assignments based on color pattern. Mismatch distributions place Atlantic founder events and population expansions at about 250,000-500,000 years ago. Estimates of effective female population sizes from mismatch and coalescence analyses are consistent with founder events by tens of individuals in the western Atlantic, followed by expansions to several million individuals.

Mimicry in coral reef fishes: ecological and behavioural responses of a mimic to its model

AbstractMimicry is a widely documented phenomenon in coral reef fishes, but the underlying relationships between mimics and models are poorly understood. Juveniles of the surgeonfish Acanthurus pyroferus mimic the coloration of different pygmy angelfish Centropyge spp. at different locations throughout the geographic range of the surgeonfish, while adopting a common species‐specific coloration as adults. This study examines the ecological and behavioural relationships between A pyroferus and one of its models, Centropyge vroliki, in Papua New Guinea. Surgeonfish underwent a transition from the juvenile (mimetic) coloration to the adult (non‐mimetic) coloration when they reached the maximum size of the angelfish. As typical of mimic–model relationships, mimic surgeonfish were always less abundant than their model. Spatial variation in the abundance of mimics was correlated with models, while the abundance of adults was not. We show that juvenile surgeonfish gain a foraging advantage by mimicking the angelfish. Mimic surgeonfish were always found within 1–2 m of a similar‐sized individual of C. vroliki with which they spent c. 10% of their time in close association. When in association with angelfish, juvenile surgeonfish exhibited an increase of c. 10% in the amount of time spent feeding compared to when they were alone. This foraging benefit seems to be explained by reduced aggression by the territorial damselfish Plectroglyphidon lacrymatus, which dominates the reef crest habitat. While adult A. pyroferus and all other surgeonfish were aggressively displaced from damselfish territories, mimic surgeonfish and their models were attacked less frequently and were not always displaced. Stomach contents analysis showed that the diet of C. vroliki differed substantially from P. lacrymatus, while that of A. pyroferus was more similar to the damselfish. We hypothesize that mimics deceive damselfish as to their diet in order to gain access to food supplies in defended areas.

Evolution and biogeography of marine angelfishes (Pisces: Pomacanthidae)

Phylogenetic relationships among angelfishes (Pomacanthidae) and their putative sister taxon, the butterflyfishes (Chaetodontidae), were examined using 12S and 16S mitochondrial DNA sequences. ML and MP trees were highly congruent with good basal resolution. Monophyly of the two families was supported, although a clade comprising the Chaetodontidae and one of the outgroups, the Scatophagidae, formed the sister clade to the Pomacanthidae. All genera and subgenera within the Pomacanthidae were examined. The relationships among the 24 representative species were consistent with traditional generic boundaries, with the exception of the genus Centropyge, but differed from previous phylogenies. Estimated ages of divergence based on trans-isthmian pairs were compared with independent fossil evidence. Trans-isthmian estimates were highly conservative, while fossil-calibrated estimates were most consistent with available evidence. Fossil calibrated estimates suggest that the family has been impacted by both the Terminal Tethyan Event and the closure of the Isthmus of Panama. Within the family, ecological diversity and species-level diversification are restricted primarily to a single pygmy angelfish clade with an origin near the Oligocene–Miocene boundary.