Pair- Formation in Coral Reef Fishes

[ThRoewer]

Interesting article:
Pair- Formation in Coral Reef Fishes: An Ecological Perspective (Full text)

Pair- formation is a common social system among animals. However, the use of the term "˜pairformation'
is often ambiguous, and the assumed reproductive importance of pairing often supersedes
consideration of aspects that are more social or ecological. This review provides a new socialecological
definition of pair- formation, examines the prevalence of pair- formation among coral reef
fishes, and assesses the ecological and reproductive characteristics of pair- forming reef fishes. Of
1981 Indo- Pacific reef fish species examined in this review, 341 (17.2%) are reported to live in pairs.
Pair forming has been reported in 29 families, with 5 families (Malacanthidae, Chaetodontidae,
Siganidae, Syngnathidae, Ptereleotridae) having more than half of their species reported to form
pairs. Two traits appear to favour the formation of social, cooperative pairs: (1) foraging on small,
benthic, and relatively immobile prey; and (2) living in burrows. In contrast, there are limited
similarities among pair- forming species with regard to their mating system or spawning mode. It
appears that the basis of pair- formation in reef fishes is complex and may involve a range of ecological
factors related to food procurement and predation risk.

Though I'm not sure if I agree with them on the classification of most Anemonefish species as not pair forming on the basis that those species may tolerate "reservists" in their anemone.

 

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Morphology, sociality, and ecology: can morphology predict pairing behavior in coral reef fishes? (Full PDF)

Abstract

Morphology can contain valuable information about the ecological performance of reef fishes, but it has rarely been used in combination with social traits. Social behavior is known to influence the ecological role of fishes; however, the ecological basis for pairing in reef fishes is not well understood. Field observations of 2,753 individuals, in 47 species in six families of biting reef fishes (Acanthuridae, Chaetodontidae, Kyphosidae, Labridae, Pomacanthidae, Siganidae), were used in combination with six morphological measurements, to examine the morphology of fishes in different social systems. A principal components analysis of morphological traits segregated species with high proportions of pairing individuals from non-pairing species along principal component 1, explaining 40.8 % of the variation. Pairing species were characterized by large eyes, concave foreheads, pointed snouts, deep bodies, and small maximum sizes. There was a significant positive relationship between these morphological traits (i.e., scores on PC1) and the prevalence of pairing within the Chaetodontidae (r^2 = 0.59; P = 0.026), Siganidae (r^2 = 0.72; P = 0.004), and Acanthuridae (r^2 = 0.82; P < 0.001). This was consistent when traits were corrected for phylogenetic effects. No pattern was evident in the scarine Labridae (r^2 = 0.15; P = 0.17). The morphological characteristics found among pairing species suggest that pairing species share common ecological traits, including foraging for small prey items in micro-topographically complex environments such as reef crevices. These ecological traits may have played a role in the evolution of pairing behavior and subsequently led to the development of reproductive patterns based on monogamy.

Keywords

Pairing, Ecomorphology, Social system, Reef fish, Foraging ecology, Functional morphology

 

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Social Systems in Habitat-Specialist Reef Fishes: Key Concepts in Evolutionary Ecology (Full PDF)

Abstract

A major focus in evolutionary ecology lies in explaining the evolution and maintenance of social systems. Although most theoretical formulations of social system evolution were initially inspired by studies of birds, mammals, and insects, incorporating a wider taxonomic perspective is important for testing deeply entrenched theory. Here, we review the contribution of studies of habitat-specialist coral reef fishes to our understanding of the evolutionary ecology of animal social systems. These fishes are ecologically similar but display remarkable variation in mating systems, social organization, and sex allocation strategies. By reviewing recent research, we demonstrate their amenability for experimental testing of key concepts in social evolution and for generating novel insights, including the ultimate reasons for female reproductive suppression, group living, and bidirectional sex change. Habitat-specialist reef fishes are a tried and tested group of model organisms for advancing our understanding of the evolution and ecology of social systems in animals.

 

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Pair formation, home range, and spatial variation in density, size and social status in blotched foxface Siganus unimaculatus on an Okinawan coral reef (Full PDF)

Abstract

The present study examined pair formation, spatial pattern of home range and spatial variation in density, size and social status of blotched foxface
Siganus unimaculatus (family Siganidae) on an Okinawan coral reef. Of 32 pairs sampled for sexing, 31 (96.9%) were heterosexual and showed size-assortative pairing. Developed ovaries were found in April and July, whereas oocytes were immature in August, September and February. Heterosexual pairing was found in both reproductive and non-reproductive periods. Home range size tended to be positively related to fork length (FL). The degree of home range overlap for same size class pairs was smaller than that for different size class pairs. The intraspecific behavior when two pairs approached each other was categorized as "˜attack,' "˜agonistic display' and "˜no interactions,' and the frequency of agonistic behaviors ("œattack" or "œagonistic display") was significantly greater than "œno interactions." Underwater observations at a seagrass bed, a rocky reef flat and a sheltered reef slope revealed that the mean FL was significantly smaller at the sheltered reef slope (4"“13 cm) than at the rocky reef flat (>13 cm). No individuals were found in the seagrass bed. Most individuals less than 6 cm FL were solitary, whereas most individuals over 7 cm FL were paired. Density was significantly greater on the sheltered reef slope than on the rocky reef flat.

 

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Why pair? Evidence of aggregative mating in a socially monogamous marine fish (Siganus doliatus, Siganidae) (Full PDF)

Abstract

Many species live in stable pairs, usually to breed and raise offspring together, but this cannot be assumed. Establishing whether pairing is based on mating, or an alternative cooperative advantage, can be difficult, especially where species show no obvious sexual dimorphism and where the act of reproduction itself is difficult to observe. In the tropical marine fishes known as rabbitfish (Siganidae), half of extant species live in socially monogamous, territorial pairs. It has been assumed that partnerships are for mating, but the reproductive mode of pairing rabbitfish is currently unconfirmed. Using passive acoustic telemetry to track movements of fishes belonging to one such species (Siganus doliatus), we provide the first evidence that paired adult fish undertake highly synchronised migrations with multiple conspecifics on a monthly cycle. All tagged individuals migrated along the same route in three consecutive months and were absent from home territories for 2-3 days just after the new moon. The timing and directionality of migrations suggests that S. doliatus may form spawning aggregations, offering the potential for exposure to multiple reproductive partners. The finding raises fundamental questions about the basis of pairing, mate choice and partnership longevity in this family.

 

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Coordinated vigilance provides evidence for direct reciprocity in coral reef fishes (Full PDF)

Abstract

Reciprocity is frequently assumed to require complex cognitive abilities. Therefore, it has been argued that reciprocity may be restricted to animals that can meet these demands. Here, we provide evidence for the potential presence of direct reciprocity in teleost fishes. We demonstrate that in pairs of coral reef rabbitfishes (f. Siganidae), one fish frequently assumes an upright vigilance position in the water column, while the partner forages in small crevices in the reef substratum. Both behaviours are strongly coordinated and partners regularly alternate their positions, resulting in a balanced distribution of foraging activity. Compared to solitary individuals, fishes in pairs exhibit longer vigilance bouts, suggesting that the help provided to the partner is costly. In turn, fishes in pairs take more consecutive bites and penetrate deeper into crevices than solitary individuals, suggesting that the safety provided by a vigilant partner may outweigh initial costs by increasing foraging efficiency. Thus, the described system appears to meet all of the requirements for direct reciprocity. We argue that the nature of rabbitfish pairs provides favourable conditions for the establishment of direct reciprocity, as continuous interaction with the same partner, simultaneous needs, interdependence, and communication relax the cognitive demands of reciprocal cooperation.

 

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Fifty million years of herbivory on coral reefs: fossils, fish and functional innovations (Full PDF)

Abstract

The evolution of ecological processes on coral reefs was examined based on
Eocene fossil fishes from Monte Bolca, Italy and extant species from the
Great Barrier Reef, Australia. Using ecologically relevant morphological
metrics, we investigated the evolution of herbivory in surgeonfishes
(Acanthuridae) and rabbitfishes (Siganidae). Eocene and Recent surgeonfishes
showed remarkable similarities, with grazers, browsers and even specialized,
long-snouted forms having Eocene analogues. These long-snouted Eocene
species were probably pair-forming, crevice-feeding forms like their Recent
counterparts. Although Eocene surgeonfishes likely played a critical role as
herbivores during the origins of modern coral reefs, they lacked the novel morphologies
seen in modern Acanthurus and Siganus (including eyes positioned
high above their low-set mouths). Today, these forms dominate coral reefs in
both abundance and species richness and are associated with feeding on shallow,
exposed algal turfs. The radiation of these new forms, and their expansion
into new habitats in the Oligocene"“Miocene, reflects the second phase in the
development of fish herbivory on coral reefs that is closely associated with the
exploitation of highly productive short algal turfs.

Keywords:
coral reef, herbivory, surgeonfish, Acanthuridae, evolution, ecological processes

 

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The natural history of a monogamous coral-reef fish, Valenciennea strigata (Gobiidae): 1. abundance, growth, survival and predation

Abstract

The population dynamics of a monogamous coral-reef fish were examined to test hypotheses of recruitment limitation, predation, and postrecruitment processes, and to determine their affects on the mating system. Valenciennea strigata are monogamous gobies that live in sand and rubble zones throughout the Indo-Pacific. Seasonal abundance was recorded in the summer and winter over 2.5 years. A subset of this population was tagged (n = 256) and followed to determine mortality and mobility. Valenciennea strigata were more abundant in summer than in winter, suggesting that a pulse of recruitment in the spring set the maximum population density. Growth rates derived from tagged fish support the hypothesis that recruitment peaked in the spring. Tagged fish experienced 88% mortality within six months; the annual mortality rate approached 100%. Evidence of predation, antipredatory behavior and strong site fidelity implicate predation as the primary source of mortality. Competition for space was not observed between adults, but may affect settlement and recruitment. Despite the lack of adult competition for space, both sexes guarded their mates and courted individuals of the opposite sex. Thus, although population size appears to be determined by nonequilibrium processes, the mating system is affected by competition for mates. Successful mate guarding by both sexes enforced monogamy.

population ecology "“ equilibrium/nonequilibrium processes "“ recruitment "“ monogamy "“ mating system "“ mate guarding

 

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Is there a reproductive basis to solitary living versus pair-formation in coral reef fishes? (Full PDF)

Abstract

Many species of coral reef fishes form pairs.
While it is assumed that pairs represent the breeding unit of these species, the reproductive status of paired versus solitary individuals, and changes in status associated with pair-formation have seldom been investigated. In order to assess whether pairing is related to reproduction we examined whether the ontogenetic timing of pair formation coincided with the onset of maturation in four species of fishes: Chaetodon lunulatus and Chaetodon melannotus (family Chaetodontidae), and Valenciennea muralis and Valenciennea strigata (family Gobiidae). 65"“78% of all fishes occurred in pairs. In C. lunulatus and V. muralis, pair-formation coincided with maturation, suggesting that these species form pairs for breeding. Further, C. lunulatus and V. muralis exhibited significant positive size-assortative pairing, which is often associated with monogamous mating. In contrast, pair formation in C. melannotus and V. strigata did not coincide with maturation. In both these species many solitary individuals were reproductive, and same sex pairs were common. While reproduction may be the basis for pairing in some species, both solitary and paired individuals are capable of breeding in others. We propose that non-reproductive mechanisms, such as predator vigilance, may explain pair-formation in coral reef fishes with non-monogamous breeding systems.

Keywords:
Chaetodon - Monogamy - Maturation - Pair-formation - Valenciennea - Vigilance

 

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When biogeographical provinces collide: Hybridization of reef fishes at the crossroads of marine biogeographical provinces in the Arabian Sea (Full Article)

ABSTRACT

Aim Suture zones are areas where closely related species from different biogeo-graphical regions come into contact and interbreed. This concept originatedfrom the study of terrestrial ecosystems but it remains unclear whether a similar phenomenon occurs in the marine environment. Here we investigate a potential suture zone from a previously unknown hybrid hotspot at the Socotra Archipelago (Yemen), located in the Arabian Sea, where fauna from the Red Sea, Gulf of Aden, Arabian Sea, western Indian Ocean and greater Indo-Polynesian Province intersect.

Location Red Sea, Gulf of Aden, Arabian Sea and Indian Ocean.

Methods Putative hybrid reef fish were identified based on intermediate coloration and morphology. Underwater observations and collections were conducted to determine: (1) whether parent species form heterospecific social groups or breeding pairs; (2) the sex and reproductive status of morphologically intermediate individuals; and (3) whether parent species were forming mixed species associations owing to a dearth of conspecific partners. To support hybrid status, morphologically intermediate and parental individuals were genotyped using mitochondrial DNA cytochrome c oxidase subunit I (COI), nuclear recombination-activating gene 2 (RAG2) and the nuclear TMO-4C4 (TMO) gene.

Results We observed putative hybrids involving 14 species from four reef fish families at Socotra. Most cases involved a parental species with a restricted distribution (e.g. Red Sea or Arabian Sea) and a broadly distributed Indo-Pacific species. In most cases, at least one of the parent species was rare at Socotra. Hybrid gene flow was largely unidirectional, and although introgression was rare, we found evidence that some butterflyfish and surgeonfish hybrids were fertile and formed breeding groups with parental species.

Main conclusions The rate of hybrid discovery at Socotra is much greater than that recorded elsewhere in the marine environment and involved both allopatric and sympatric species. This study highlights the importance of biogeographical location, reef habitat, environmental conditions and abundance disparities at Socotra in potentially facilitating hybridization among reef fishes at the edge of their distribution.

Keywords
Coral reef fish, Gulf of Aden, hybrid hotspot, introgression, mitochondrial DNA, nuclear DNA, Socotra.

 

[ThRoewer]

I think this somewhat fits here too:

Hybridization of reef fishes at the Indo-Pacific biogeographic barrier: a case study (full article)

Abstract
Hybridization is recognized as an important source of genetic variation. In some reef fishes, including the Acanthuridae, hybridization has been detected due to intermediate colouration. This study used a molecular genetic approach to investigate hybridization in two Acanthurid species: Acanthurus leucosternon and Acanthurus nigricans, which have Indian and Pacific Ocean distributions respectively and are sympatric in the eastern Indian Ocean. In this area a putatitve hybrid, Acanthurus cf. leucosternon has been recognized based on intermediate colouration and restriction to the sympatric region of otherwise allopatric putative parental species. This study aimed to test this hypothesis using genetic tools. The three species were sampled from Cocos (Keeling) and Christmas Islands, the biogeographic boundary where many Indian and Pacific Ocean biota meet. Representatives from allopatric populations of both parental species and outgroups were also sampled. Mitochondrial COI and intron 1 of the nuclear ribosomal protein S7 were sequenced from 13 and 30 specimens respectively. Although sample sizes in this study are relatively small and more genetic data, including an extended phylogeographic sampling, is required to further evaluate these findings, the COI results support hybrid origins of Acanthurus cf. leucosternon, but S7 data are inconclusive due to the possibility of incomplete lineage sorting. The fourfold more abundant Acanthurus nigricans is most often the maternal parent. Inter-fertile hybrids apparently backcross with rare Acanthurus leucosternon males, transferring Acanthurus nigricans mitochondria to this species. These results suggest that Acanthurus leucosternon may eventually be lost from these islands, due to their relative rarity and introgressive hybridization.

Marine hybrid hotspot at Indo-Pacific biogeographic border (full article)

Abstract

Studying hybridization is crucial to understanding speciation and almost all our knowledge comes from terrestrial and freshwater environments. Marine hybrids are considered rare, particularly on species-rich coral reefs. Here, we report a significant marine hybrid zone at Christmas and Cocos Islands (eastern Indian Ocean) with 11 hybrid coral reef fishes (across six families); the most recorded hybrids of any marine location. In most cases, at least one of the parent species is rare (less than three individuals per 3000 m2), suggesting that hybridization has occurred because individuals of the rare species have mated with another species owing to a scarcity of conspecific partners. These islands also represent a marine suture zone where many of the hybrids have arisen through interbreeding between Indian and Pacific Ocean species. For these species, it appears that past climate changes allowed species to diverge in allopatry, while recent conditions have facilitated contact and subsequent hybridization at this Indo-Pacific biogeographic border. The discovery of the Christmas"“Cocos hybrid zone refutes the notion that hybridization is lacking on coral reefs and provides a natural laboratory for testing the generality of terrestrially derived hybridization theory in the marine environment.



Figure 1 (click to enlarge)
Christmas and Cocos Islands (represented by five-pointed stars) constitute a tropical marine suture zone located in the eastern Indian Ocean on the Indo-Pacific marine biogeographic border. At these islands, Indian (represented by lighter shaded area with dashed outline) and Pacific Ocean species (darker shaded area with solid outline) have come into contact and interbred.


Figure 2 (click to enlarge)
Christmas and Cocos Islands constitute a marine suture zone where (a) Indian Ocean (C. eibli) and (b) Pacific Ocean species (C. flavissima) come into contact and interbreed to produce (c) hybrids. (d) Heterospecific breeding pairs of Ch. guttatissimus (Indian Ocean: bottom) and Ch. punctatofasciatus (Pacific Ocean: top) produce (e) hybrids. (f) Heterospecific breeding pair of Indian (Ch. trifasciatus: bottom) and Pacific Ocean (Ch. lunulatus: top) butterflyfishes.

 

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Behavioural Sex Change in the Absence of Gonads in a Coral Reef Fish (Full PDF)

Abstract

It is an axiom of vertebrate behavioural endocrinology that full expression of a male behavioural phenotype depends on testicular influences during development, in adulthood, or both. Sex change in fishes challenges this necessity: behavioural changes are often rapid and greatly precede gonadal changes. However, steroid hormones can have fast actions on the nervous system, so gonadal influences on behavioural sex change cannot be excluded based solely on the speed of these changes. We report that surgical gonad removal does not prevent or discernibly alter female-to-male behavioural sex change in a protogynous coral reef fish. Male behaviour assumption is instead purely dependent on attaining social dominance. This is the first example of a vertebrate fully expressing a male behavioural phenotype without current or previous exposure to a functioning testis or testicular products.

Hypothalamic Arginine Vasotocin mRNA Abundance Variation Across Sexes and with Sex Change in a Coral Reef Fish (Full PDF)

Abstract

Gonadal hormones are important mediators of sexual and aggressive behavior in vertebrates. Recent evidence suggests that the peptide hormones arginine vasotocin (AVT) and its mammalian homologue arginine vasopressin (AVP) often critically mediate these gonadal hormone effects on behavior and have direct influences on behavioral variation. Behavioral differences between sexes, across reproductive states, and even among closely related species are correlated with differences in central AVT/AVP systems in many species. We report differences in hypothalamic AVT mRNA levels between distinct alternate male phenotypes and with female-to male sex change in the bluehead wrasse (Thalassoma bifasciatum), a teleost fish. The aggressively dominant and strongly courting male phenotype has greater numbers of AVT mRNA producing cells in the magnocellular preoptic area of the hypothalamus than females. Levels of AVT mRNA within these cells in dominant males are also approximately three times female levels whereas the non-aggressive male phenotype has AVT mRNA levels approximately twice female levels. Behavioral sex change is very rapid in this species and is not dependent on the presence of gonads. Conversely, rapid increases in sexual and aggressive behavior during sex change are closely paralleled by approximate fourfold increases in hypothalamic AVT-mRNA levels. The behavioral plasticity shown by bluehead wrasses in response to social environment might be mediated in part by a neuropeptide, AVT, with changes in the gonads and gonadal hormones as the result rather than the cause of behavioral dominance.

Sex change in coral reef fish (Full PDF)

Abstract

Gonadal differentiation can take many forms in fish, ranging from gonochorism, where individuals directly develop as male or female and finally possess only testis or ovaries at sexual maturation, to hermaphroditism where the same individuals can produce mature male and female gametes at some time in their lives. Hermaphrodite fish are, thus, an excellent model for studying the plasticity of sex determination and differentiation in vertebrates. We have shown that sex steroids play a principal role in sex differentiation and sex change in fish. Our laboratory implements several fish models that undergo sex change from female to male or male to female or in both directions. In this review, we will briefly discuss recent advances in our understanding of the mechanism of sex change in coral reef fish.


Keywords
Sex change "“ Estrogen "“ Tropical fish "“ Protogynous sex change "“ Protandrous sex change "“ Serial sex change

Diversity and flexibility of sex-change strategies in animals (Full PDF)

Here, we review recent empirical advances that have improved our understanding of why and when sex change occurs. We show that sex-changing animals use a greater diversity of strategies to increase their reproductive success than was previously recognized: some individuals change sex early, others change sex late, some individuals change sex more than once, and others do not change sex at all. These different strategies can be unified by the principle that individuals change sex when it increases their reproductive value. The breeding tactics (male, female or non-breeder) adopted by individuals often appear to be adaptive responses to their own social"“ecological context and variation in these conditions results in significant differences in the timing of sex change within and between species.

Sex Change and Sexual Selection (Full PDF)

Abstract

Uses research on the reproductive biology of bluehead wrasse (Thalassoma bifasciatum), a labrid fish, to present a unified mathematical theory, in terms of selection of individuals, of the circumstances favoring sex change. The disadvantage of changing sex, the conditions that reverse this disadvantage, and the optimum age of changing sex when one sex does gain fertility more rapidly than the other are examined. The phenomenon is also studied of male dimorphism, involving small nonterritorial males and large territorial ones, that arises when a runaway sexual selection among members of the transformed or older sex (usually male) permits a small difference in size or age to confer a disproportionate difference in fertility. Field observations are reported. The mathematics suggest that animals should change sex if one sex gains in fertility much more rapidly with age than the other, although the costs of changing the reproductive anatomy of animals which practice internal fertilization or whose females are viviparous or bear large eggs may be enormous. (24 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)

The role estrogens play in sex differentiation and sex changes of fish (Full Text)

Abstract
Using genetically controlled all-female and all-male tilapia (Oreochromis niloticus), the role steroid hormones play in the sex differentiation was analyzed histologically, ultrastructurally, immunohistichemically and experimenntally. The results strongly suggest that endogenous estrogen acts as an ovarian inducer, and that the lack of steroid hormone including androgen is important for testicular differentiation. Moreover, the roles of steroid hormones in protogynous sex change of three-spotted wrasse (Halicho eres trimaculatus) and saddleback wrasse (Tharassoma duperrey) were examined. The results strongly support the hypothesis that the endogenous estrogen plays an important role in protogynous sex change.

Reversed Sex‐Change in the Protogynous Reef Fish Labroides dimidiatus

Abstract

Protogynous hermaphroditism, or female-to-male sex change, is known for many reef fishes including wrasses (family Labridae) in which large males monopolize mating. When the dominant male disappears from a polygynous group, the largest female may change sex within a few weeks. Such social control of sex change was first documented in harems of the cleaner wrasse Labroides dimidiatus almost 30 yr ago. To examine whether change of social status would induce males of L. dimidiatus to perform reversed sex-change, we conducted experiments: (i) releasing single males near lone males whose mates have been removed in the field; and (ii) keeping two males in a tank. Smaller males changed back to females when they became subordinate: it took 53"“77 d (n=3) for them to complete gonadal sex change and release eggs in the aquarium. The male"“male pairs performed spawning behavior, with the smaller male in the female role already 5"“58 d before completion of gonadal sex change. This is the first report of reversed sex-change among protogynous wrasses. Moreover, we conducted another experiment, keeping a pair of a male and a larger female in a tank (n=1). We found sex change by both mates, which has not been reported from any fishes. Thus, the sex of L. dimidiatus is strictly determined by social status whenever it changes after mate loss.

 

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Hybridization of reef fishes at the Indo-Pacific biogeographic barrier: a case study (Full PDF)

Abstract
Hybridization is recognized as an important source of genetic variation. In some reef fishes, including the Acanthuridae, hybridization has been detected due to intermediate colouration. This study used a molecular genetic approach to investigate hybridization in two Acanthurid species: Acanthurus leucosternon and Acanthurus nigricans, which have Indian and Pacific Ocean distributions respectively and are sympatric in the eastern Indian Ocean. In this area a putatitve hybrid, Acanthurus cf. leucosternon has been recognized based on intermediate colouration and restriction to the sympatric region of otherwise allopatric putative parental species. This study aimed to test this hypothesis using genetic tools. The three species were sampled from Cocos (Keeling) and Christmas Islands, the biogeographic boundary where many Indian and Pacific Ocean biota meet. Representatives from allopatric populations of both parental species and outgroups were also sampled. Mitochondrial COI and intron 1 of the nuclear ribosomal protein S7 were sequenced from 13 and 30 specimens respectively. Although sample sizes in this study are relatively small and more genetic data, including an extended phylogeographic sampling, is required to further evaluate these Wndings, the COI results support hybrid origins of Acanthurus cf. leucosternon, but S7 data are inconclusive due to the possibility of incomplete lineage sorting.
The fourfold more abundant Acanthurus nigricans is most often the maternal parent. Inter-fertile hybrids apparently backcross with rare Acanthurus leucosternon males, transferring Acanthurus nigricans mitochondria to this species. These results suggest that Acanthurus leucosternon may eventually be lost from these islands, due to their relative rarity and introgressive hybridization.
Keywords
Acanthuridae · Hybridization · Introgression · COI and S7 intron 1 · Biogeography · Mating behaviour