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See detailFurther insight into the iterative ecological radiation of damselfishes (Pomacentridae)
Gajdzik, Laura ULiege; Lepoint, Gilles ULiege; Michel, Loïc ULiege et al

Conference (2017, October 05)

The evolutionary history of Pomacentridae (damselfishes) is a rare example of the occurrence of an iterative ecological radiation in the ocean. Damselfishes have experienced many repeated convergences ... [more ▼]

The evolutionary history of Pomacentridae (damselfishes) is a rare example of the occurrence of an iterative ecological radiation in the ocean. Damselfishes have experienced many repeated convergences wherein subclades radiated across similar trophic strategies (i.e. pelagic foragers, benthic feeders, and an intermediate group) and similar morphologies. The presence of evolutionary convergences in damselfishes was recently highlighted by the combination of ecological and morphological data, and the use of phylogenetic comparative methods. Nevertheless, many other aspects of these replicated sets of lineages remain unexplored. For example, little is known about the functional diversity of assemblages including convergent lineages that emerged from iterative processes of ecological radiation, or which of the niche-related processes and phylogenetic conservatism are the major factors shaping these assemblages. Here, we conducted a quantitative comparison of these processes in damselfish assemblages that belong to three distinct Indo-Pacific coral reefs differing in taxonomic composition, morphology and degree of human disturbance. Using various metrics, we compared the functional diversity (based on a dataset of eight functional traits) and the isotopic diversity (a proxy of trophic diversity) among assemblages, grasping many aspects of the eco-functional diversity of Pomacentridae. We also tested whether these eco-functional traits displayed some evolutionary conservatism. Our results demonstrate that the eco-functional diversity of damselfishes follows similar patterns among Indo-Pacific coral reefs. The trophic space remains equivalent despite gradient in species richness, whereas the number of functional entities occupied by taxa dictates the size of the functional space. In each assemblage, eco-functional niches are highly differentiated and evenly distributed in spaces of similar size. The inconsistent phylogenetic structure of eco-functional traits suggests that the similarity in the diversity of damselfish assemblages is mainly driven by niche-based processes and not by phylogenetic relatedness. We suggest that a broader application of our approach will help to uncover the mechanisms of reef fish community assembly over space and time. [less ▲]

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See detailAdaptive capacity assessment of damselfishes (Pomacentridae)
Gajdzik, Laura ULiege

Doctoral thesis (2017)

Assessing the multiple facets of adaptive capacity is a core issue as it reflects species' ability to cope with variations in environmental conditions. Within the threatened coral reefs, the Pomacentridae ... [more ▼]

Assessing the multiple facets of adaptive capacity is a core issue as it reflects species' ability to cope with variations in environmental conditions. Within the threatened coral reefs, the Pomacentridae (damselfishes) represent a very suitable model to undertake such issue. Damselfishes are one of the most ecologically dominant reef fish families whose lineages repeatedly radiated across convergent trophic strategies. These strategies comprise (1) pelagic feeders (mainly picking zooplankton in the water column), (2) benthic feeders (essentially feeding on algae and vagile invertebrates on the benthos) and (3) an intermediate group (foraging in the entire bentho–pelagic compartment). To date, most studies compared the degree of vulnerability between specialists and generalists because the first ones are thought to have a higher risk of extinction. The tripartite trophic guild system in Pomacentridae provides the opportunity to step out of the binary "specialist–generalist" classification and to robustly grasp the adaptive capacity by focusing on fundamental units in assemblages. In the present thesis, I estimated the ecology of damselfishes by quantifying their eco–functional diversity (including trophic, habitat and behavioural diversity and also the ecosystem functions they performed) and by gauging their abiotic (i.e. species–environment relationship) and biotic (i.e species–species relationship) interactions. Ecological results revealed (a) the systematic presence of the three main trophic guilds in each assemblage, and (b) a consistent pattern of species eco–functional niches that are highly differentiated and evenly distributed in eco–functional spaces of similar size, but they provided (c) limited support for any degree of trophic plasticity (i.e. little evidence for any geographic variation in the diet of widespread species). The trophic guilds were also functionally dissimilar and displayed different levels of functional diversity. The intermediate group was the least functionally diverse guild with the lowest functional redundancy, while opposite findings were found for the pelagic–feeding guild. Then, I quantified the genetic diversity, which varied among trophic guilds and was associated with variation in their trophic ecology and habitat–behavioural traits (e.g. pelagic feeders have the lowest genetic and ecological diversity). Using a phylogenetic framework, I found that functional traits were evolutionarily labile and accumulated at a similar rate within the three trophic guilds. Transition rates among guilds were also biased, suggesting differences in the evolvability. The evaluation of all of these components indicated that some processes occurring at an "ecological" timescale and others at an "evolutionary" timescale had concordant effects (e.g. the coupling between levels of genetic and ecological diversity supported by the evolvability result for the intermediate group), although sometimes one type of process had more important effects (e.g. the principle of competitive exclusion probably shaped the high functional diversity of pelagic feeders). Overall, I demonstrated that the adaptive capacity of Pomacentridae is bounded and that trophic guilds are not equal in the face of environmental changes. The case of pelagic feeders illustrates a scenario wherein evolution and the right environmental conditions led to the success of a given group, but their persistence may be jeopardized by a low genetic diversity. The two other guilds possess more intrinsic assets (e.g. less restricted habitat and dietary requirements) to adapt. Given the uncertainty regarding the pace at which evolutionary processes will occur and the potential imperilment of evolvability to act as a source of future diversity, the ability to diversify along many niche axes associated with broad intrinsic characteristics (i.e. higher genetic diversity) may help organisms to sustain themselves in a long–term perspective and to maintain more ecosystem functions. [less ▲]

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See detailEvolution and diversity of ram-suction feeding in damselfishes (Pomacentridae)
Olivier, Damien ULiege; Gajdzik, Laura ULiege; Parmentier, Eric ULiege et al

in Organisms Diversity and Evolution (2017), 17

The cerato-mandibular (c-md) ligament is a synapomorphy within Pomacentridae that creates a tight link between the lower jaws and the hyoid bars. However, this morphological trait has been secondarily ... [more ▼]

The cerato-mandibular (c-md) ligament is a synapomorphy within Pomacentridae that creates a tight link between the lower jaws and the hyoid bars. However, this morphological trait has been secondarily lost in multiple lineages during evolution. A previous study revealed that the loss of this trait acted as a release of evolutionary constraints, leading to a cascade of morphological changes such elongated buccal jaws and a slender body. Ecomorphological interpretations suggested the loss of the c-md ligament has ultimately led to a new adaptive peak in zooplanktivory through an optimization of the ram feeding mode associated with a specialization in pelagic feeding. Here, we tested these hypotheses by comparing functional and diet diversity between damselfish species with and without the c-md ligament. Although species lacking the c-md ligament presented a conserved kinematic pattern resulting from high ram and low suction performances, our results did not support an optimization of the ram feeding mode. Indeed, some species with the c-md ligament showed the same or exceeded the ram performance of species without the c-md ligament. The species with the c-md ligament had a more diverse kinematic pattern exploring the entire ram-suction functional range in damselfishes. Finally, our results did not show any diet variations associated with the loss of the c-md ligament. Our study furthers the understanding of how a morphological trait has shaped, by its presence or absence, the ecomorpho-functional diversification of Pomacentridae. [less ▲]

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See detailDon't judge a fish by its fins: species delineation of Congolese Labeo (Cyprinidae)
Van Steenberge, Maarten; Gajdzik, Laura ULiege; Chilala, Alex et al

in Zoologica Scripta (2016)

Conspicuous characters are often useful in species identification. Yet, identification and delineation are two different processes, and such characters do not necessarily provide the best basis on which ... [more ▼]

Conspicuous characters are often useful in species identification. Yet, identification and delineation are two different processes, and such characters do not necessarily provide the best basis on which species can be delineated. This is illustrated by the case of the Labeo with papillary lips from the Congo basin. Traditionally, species delineation in this group was based on a conspicuous trait: the shape of the dorsal fin, which shows a profound degree of differentiation. Morphometric analyses were performed on 185 specimens both with and without measurements taken on this fin. The groups obtained using these two approaches were compared with those obtained through DNA barcoding. For this, 24 sequences of the standard barcoding COI gene were obtained. Species delineations based on morphological and molecular results were in agreement when the shape of the dorsal fin was ignored. This suggested that of the five nominal species known from the Congo basin, L. altivelis, L. rosae, L. lineatus, L. weeksii and L. maleboensis, only the former three remain valid. Consequently, L. weeksii was synonymised with L. altivelis and L. maleboensis with L. lineatus. The sole Congo basin endemic is L. lineatus as L. altivelis and L. rosae also occur in more southern basins. The use of the shape of the dorsal fin in morphological studies has previously led to overestimates of species diversity in this group. This is due to the fact that L. altivelis shows a remarkable amount of geographical variation for this trait. The large amount of intra- and interspecific variation in this character was caused by differential allometric growth in different parts of the dorsal fin. [less ▲]

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See detailTrophic specializations of damselfishes are tightly associated with reef habitats and social behaviours
Gajdzik, Laura ULiege; Parmentier, Eric ULiege; Sturaro, Nicolas ULiege et al

in Marine Biology (2016), 163

Despite the increasing need to understand factors shaping community assembly, few studies have simultaneously explored the influence of niche-based and phylogenetic processes. Here, we investigate the ... [more ▼]

Despite the increasing need to understand factors shaping community assembly, few studies have simultaneously explored the influence of niche-based and phylogenetic processes. Here, we investigate the relationships between diet, habitat and social behaviour in damselfishes (Pomacentridae) collected in 2014 at Moorea Island (17°30′S, 149°50′W), French Polynesia. Isotope ratios of carbon and nitrogen, in association with stomach contents, delineate three trophic groups: pelagic feeders consuming zooplankton, benthic feeders mainly grazing on algae and an intermediate group feeding on prey from the whole bentho-pelagic compartment. Sulphur isotope ratios indicate segregation between species of the outer reef mostly depending on oceanic input of zooplankton and the lagoonal species relying on locally produced resources or even on terrestrial supply. We demonstrate a tight association between dietary specializations, habitat characteristics and social behaviours, and these correlations are further confirmed by integrating the phylogeny of Pomacentridae. We also provide evidence of phylogenetic conservatism for the stomach content and the habitat–behaviour characters. However, the isotopic trait is evolutionarily more labile probably because it thoroughly depicts the ecological niche of species. To summarize, pelagic feeders (mainly from the Chrominae) usually form shoals in areas close to the open ocean at a maximum depth of 20 m. Benthic feeders (well represented in the Stegastinae) are ubiquitous, solitary and mostly territorial species found at various depths. The intermediate group includes gregarious species from three subfamilies that forage in the lagoon usually above 12 m depth. Overall, we give insight into processes that have structured the damselfish community in Moorea. [less ▲]

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See detailTrophic Ecology of Damselfishes
Frederich, Bruno ULiege; Olivier, Damien ULiege; Gajdzik, Laura ULiege et al

in Frederich, Bruno; Parmentier, Eric (Eds.) Biology of Damselfishes (2016)

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See detailImpact of the trophic strategy on the eco-functional diversification of a coral reef fish family
Gajdzik, Laura ULiege; Aguilar-Medrano, Rosalia; Parmentier, Eric ULiege et al

Conference (2015, September)

The analyses of the role of trophic strategies as promoter or constraint on processes of diversification remain understudied, especially in fish. The Pomacentridae (damselfishes), a species-rich (394 ... [more ▼]

The analyses of the role of trophic strategies as promoter or constraint on processes of diversification remain understudied, especially in fish. The Pomacentridae (damselfishes), a species-rich (394 species) and worldwide distributed reef fish family, include three main trophic guilds: (1) pelagic zooplankton feeders, (2) benthic feeders grazing on turf algae or biting polyps and (3) an intermediate group feeding on zooplankton, small benthic invertebrates and algae. Our study aims to analyze the role of the trophic strategies in the eco-functional diversity of Pomacentridae. Due to its feeding versatility, we hypothesize that the intermediate trophic group is the most successful group in terms of eco-functional diversity through evolutionary time. To target our aim, we compiled detailed dietary, environmental and behavioral data for 201 pomacentrid species, and compared the eco-functional diversity among trophic guilds. Various metrics, such as functional entity (i.e. unique combinations of functional traits) and functional richness revealed that the intermediate trophic group exhibited the lowest diversity. Then, we used time-calibrated phylogenies and comparative methods to evaluate the impact of trophic strategies on the tempo of ecological diversification. Results were consistent and the lowest rate of diversification was found for the intermediate trophic group. Our study shows that a generalist trophic strategy does not promote ecological diversification but being specialized may increase the ability to evolve greater diversity. [less ▲]

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See detailComparison of isotopic turnover dynamics in two different muscles of a coral reef fish during the settlement phase
Gajdzik, Laura ULiege; Lepoint, Gilles ULiege; Lecchini, David et al

in Scientia Marina (2015), 79(3), 325-333

The temporal variation in carbon and nitrogen isotopic compositions (noted as δ13C and δ15N) was investigated in the convict surgeonfish (Acanthurus triostegus) at Moorea (French Polynesia). Over a period ... [more ▼]

The temporal variation in carbon and nitrogen isotopic compositions (noted as δ13C and δ15N) was investigated in the convict surgeonfish (Acanthurus triostegus) at Moorea (French Polynesia). Over a period of 24 days, juveniles were reared in aquaria and subjected to two different feeding treatments: granules or algae. The dynamics of δ13C and δ15N in two muscles (the adductor mandibulae complex and the epaxial musculature) having different functions were compared. At the end of experiments, a steady-state isotopic system in each muscle tissue was not reached. Especially for the algal treatment, we found different patterns of variation in isotopic compositions over time between the two muscles. The turnovers of δ13C showed opposite trends for each muscle but differences are mitigated by starvation and by the metamorphosis. Our study highlighted that the metabolism of coral reef fish may be subjected to catabolism or anabolism of non-protein precursors at settlement, inducing variation in isotopic compositions that are not linked to diet change. [less ▲]

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See detailEcological diversity of damselfishes (Pomacentridae) from Moorea
Gajdzik, Laura ULiege; Parmentier, Eric ULiege; Lepoint, Gilles ULiege et al

Poster (2014, December)

The Pomacentridae (damselfishes) represents the 3rd most species-rich coral reef fish family, including 394 species spread worldwide. Recent studies suggested that damselfishes iteratively evolve along ... [more ▼]

The Pomacentridae (damselfishes) represents the 3rd most species-rich coral reef fish family, including 394 species spread worldwide. Recent studies suggested that damselfishes iteratively evolve along three main trophic guilds: “the pelagic feeders” feeding mainly on zooplankton, “the benthic feeders” grazing filamentous algae or biting coral polyps, and an “intermediate” group with species feeding on zooplankton, small benthic invertebrates and algae in variable proportions. Comparing the ecological diversity of damselfish communities among various geographical regions could assess such an iterative radiation. Within this context, the present study is a first attempt exploring the trophic diversity of damselfish community at Moorea Island (French Polynesia). The relationship between the trophic guilds, their habitat diversity and their behavior is evaluated. Habitat and behaviour of 16 damselfish species were described during transects along which different kinds of data were collected. For examples, the location within the reef (e.g. fringing or barrier reef), the depth, the substrate over which fishes are living or the solitary/gregarious habits were recorded. Diet of individuals was investigated by means of stomach content and stable isotopes analyses. Correlations between the dietary preferences and ecological data (habitat and behaviour) are given and the ecological diversity among trophic groups is compared. [less ▲]

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See detailLabeo rosae (Cypriniformes: Cyprinidae) in the Congo basin: a relict distribution or a historical introduction?
Van Steenberge, Maarten; Gajdzik, Laura ULiege; Chilala, Alex et al

in Journal of Fish Biology (2014)

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See detailThe mangrove forests as nursery habitats for the ichthyofauna of Mida Creek (Kenya, East Africa)
Gajdzik, Laura ULiege; Vanreusel, Ann; Koedam, Nico et al

in Journal of the Marine Biological Association of the United Kingdom (2014), 94(5), 865-877

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See detailA re-evaluation of species diversity within the Labeo (Cypriniformes: Cyprinidae) with papillary lips from the Congo basin
Gajdzik, Laura ULiege; Van Steenberge, Maarten; Chilala, Alex et al

Poster (2013, September)

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See detailThe mangrove forest as a feeding ground and nursery habitat for the ichthyofauna: Mida Creek in Kenya
Gajdzik, Laura ULiege; Vanreusel, Ann; Koedeam, Nico et al

in Mees, J.; Seys, J. (Ed.) (2013). Book of abstracts – VLIZ Young Marine Scientists' Day. Brugge, Belgium, 15 February 2013. VLIZ Special Publication, 63. Vlaams Instituut voor de Zee (VLIZ): Oostende. xii, 168 pp. Part of: VLIZ Special Publication. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISSN 1377-0950 (2013, February 15)

Mangrove forests are among the most productive ecosystems, sustaining both terrestrial and aquatic fauna (Kathiresan, 2011). They are important to coastal fisheries by providing foraging and hiding places ... [more ▼]

Mangrove forests are among the most productive ecosystems, sustaining both terrestrial and aquatic fauna (Kathiresan, 2011). They are important to coastal fisheries by providing foraging and hiding places for commercially valuable fishes (Tomlinson, 1986; Rönnbäck 1999). This research investigated the fish assemblage of Mida Creek (Kenya, East Africa) as well as the presumed feeding and nursery functions of the area for the ichthyofauna present. This explorative study contributes to a Kenyan-Flemish project in which scientists aim to identify the impacts of human exploitation and management regimes of mangroves on biodiversity richness and abundance, including demersal fish. The species composition of the ichthyofauna of Mida and trophic interactions therein was studied for five representative sampling areas. These sites are located at various distances from local villages in order to include the effect of different degrees of human disturbance. Samples were collected during 5-6 consecutive days close to spring tide in mid July 2011. Fishes were caught using several types of passive fishing gears such as large and small fyke nets, gill nets and occasionally beach seine. Each individual was identified to species level, measured and weighed. We performed stomach content analysis to provide information about fish diet. Furthermore, stable isotope analysis was applied on most fishes in order to detect whether the source of primary production for the higher trophic levels is mangrove-related or not. A total of 29 fish species was found with a catch of 939 teleost specimens. Our analyses showed that a majority of fish belonged to the zoobenthivorous/omnivorous trophic mode, they were mainly feeding on invertebrates. Their diet was quite similar over different locations and life stages. Two species (Sphyraena barracuda and Synodus variegatus) exhibited a mixed diet with a piscivorous preference. Results concerning the population structure suggested that the fish community of Mida consisted of both transient and resident species. Juveniles were, however, numerically more abundant in the whole area than adult specimens. Based on our restricted sampling period and methodology, we were not able to accurately detect human impacts on fish stock and species composition between locations. Finally, our results confirm that Mida Creek mangrove is an important habitat for the ichthyofauna especially for juvenile fishes. Its role as feeding and nursery ground appears well established. [less ▲]

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