Mediterranean Wrasse Research Articles

Multispecies colour polymorphisms associated with contrasting microhabitats in two Mediterranean wrasse radiations.

Intraspecific colour polymorphisms (CPs) present unique opportunities to study fundamental evolutionary questions, such as the link between ecology and phenotype, mechanisms maintaining genetic diversity and their putative role in speciation. Wrasses are highly diverse in ecology and morphology and harbour a variety of colour‐polymorphic species. In the Mediterranean Sea, wrasses of the tribe Labrini evolved two species radiations each harbouring several species with a brown and a green morph. The colour morphs occur in complete sympatry in mosaic habitats with rocky outcrops and Neptune grass patches. Morph‐specific differences had not been characterized yet and the evolutionary forces maintaining them remained unknown. With genome‐wide data for almost all Labrini species, we show that species with CPs are distributed across the phylogeny, but show evidence of hybridization. This suggests that the colour morphs are either ancient and have been lost repeatedly, that they have evolved repeatedly or have been shared via hybridization. Focusing on two polymorphic species, we find that each colour morph is more common in the microhabitat providing the best colour match and that the morphs exhibit additional behavioural and morphological differences further improving crypsis in their respective microhabitats. We find little evidence for genetic differentiation between the morphs in either species. Therefore, we propose that these colour morphs represent a multi‐niche polymorphism as an adaptation to the highly heterogeneous habitat. Our study highlights how colour polymorphism (CP) can be advantageous in mosaic habitats and that Mediterranean wrasses are an ideal system to study trans‐species polymorphisms, i.e. polymorphisms maintained across several species, in adaptive radiations.

Assessing anti-predatory chemical defences among ten eastern Mediterranean sponges

The palatability of organic chemical extracts from ten of the most abundant sponge species along the Israeli (shallow) coast, eastern Mediterranean Sea (Axinella sp., Axinella polypoides, Chondrilla nucula, Ircinia sp., Psammocinia sp. 1, Psammocinia sp. 2, Psammocinia sp. 3, Psammocinia sp. 4, Sarcotragus sp. and Tetilla sp.) was tested. To examine the generality of the phenomenon, it was evaluated with two types of potential predators, a fish and a gastropod. It was determined that the extracts of only two species (Psammocinia sp. 1 and Psammocinia sp. 3) deterred feeding of the omnivorous ornate Mediterranean wrasse Thalassoma pavo. On the other hand, extracts of five other sponges (Chondrilla nucula, Axinella sp., Ircinia sp., Sarcotragus sp. and Psammocinia sp. 2) were non-palatable to the omnivorous gastropod Strombus persicus (the extracts that deterred the fish did not deter the gastropod and vice versa). We also determined the capacity of extracts from six Red Sea sponges to deter T. pavo, and compared it with these extracts' effect on the Red Sea wrasse T. klunzingeri. All the extracts that deterred the Red Sea wrasse (from Amphimedon chloros, Crella cyatophora, Negombata magnifica and Theonella swinhoei) were also non-palatable to the Mediterranean wrasse. In addition to these four species, also Diacarnus erythraenus deterred Thalassoma pavo while being palatable to T. klunzingeri, whereas food pellets with extracts of Niphates rowi were eaten by both wrasse species.

Mating behaviour of the newly-established ornate wrasse Thalassomapavo (Osteichthyes: Labridae) in the Ligurian Sea (north-western Mediterranean)

Reproduction of newly established populations of the warm-water Atlantic Mediterranean wrasse Thalassoma pavo is here reported for the first time in the Ligurian Sea, and mating behaviour is described in detail. The reproductive season (May to October) may be divided in three stages: (1) pre-mating (mid-May to the end of June), during which terminal-phase (TP) males establish territories and start courting females; (2) mating (end of June to the end of August), with a mean frequency of up to one spawning event ind−1 h−1; and (3) post-mating (September to mid-October), when TP males remained inside territories but no spawning events were recorded. Mating followed two distinct modalities: pair spawning and group spawning, the latter replacing the former when population density exceeded 10 ind 100 m−2. Four phases have been distinguished in both modalities: (1) approach (pair) or gathering (group), to establish the contact between potential partners; (2) acceptance (pair) or priming (group), in which partners establish a common behavioural pattern; (3) ascent to near the sea surface; and (4) spawning. The saddled sea-bream Oblada melanura has been seen to predate intensively on the large cloud of sexual products released by groups.

Uncertainty in territory quality affects the benefits of usurpation in a Mediterranean wrasse

Individuals should defend sites when the expected benefits of the territory exceed the cost of defense. However, if territory qulaity is unpredictable or difficult to assess, the expected pattern of territorial behavior is less clear. In a Mediterranean wrasse, Symphodus ocellatus, mating success is skewed with 2% of nesting males getting more than 20% of the spawning success. Yet, variation in mating success is not explained by any known physical characteristic of males or their territories. Instead, females prefer nests with a recent history of mating success because males are less likely to desert the offspring she leaves behind. Thus, territory quality is transient and determined by interactions between the sexes. I measured the frequency of territorial takeovers and the uncertainty in mating success among days at a nest. Observations indicated that S. ocellatus males usurped their neighbor’s successful nests when males were unsuccessful and larger than their successful neighbor. Sites that achieved mating success had a significantly higher probability (0.84) of remaining sucessful between consecutive days than unsuccessful territories had of becoming successful (0.30). Unsuccessful males obtained higher and more certain fitness returns if they usurped a successful neighbor’s territory. Interactions within and between the sexes drive uncertainty in success, which influences territorial behavior in this species. Key words: territoriality, stochasticity, labridae, sexual conflict, assessment. [Behav Ecol 15:278–285 (2004)]

Allocation to Mate Guarding or Increased Sperm Production in a Mediterranean Wrasse.

An excellent body of literature exists that examines sperm expenditure when males allocate only to sperm production. However, in many species, males can also allocate energy to behaviors that influence sperm competition. We model whether males in sperm competition should allocate energy to mate guarding or additional sperm production. Mate guarding is predicted to lead to greater reproductive success than increased sperm output, and mate-guarding males are not predicted to alter their allocation to sperm production with increasing sperm competition. Only when mate guarding is ineffective or greatly reduces sperm production are males predicted to allocate to sperm production. In a Mediterranean wrasse Symphodus ocellatus, three male alternative reproductive behaviors coexist. While nesting males and satellites guard mates to decrease sperm competition, sneaker males only compete via sperm production. Sneakers produce four times as much sperm per spawn as either nesting males or satellites. As predicted by the model, mate guarding but not sperm production increased with increased risk of sperm competition in nesting males. We argue that this can be explained by nesting males allocating to mate guarding rather than sperm production. Considering allocation among behaviors that affect sperm competition enhances our ability to explain and to predict sperm allocation patterns.

Allocation to Mate Guarding or Increased Sperm Production in a Mediterranean Wrasse

Allocation to Mate Guarding or Increased Sperm Production in a Mediterranean Wrasse

Dynamic games and field experiments examining intra- and intersexual conflict: explaining counterintuitive mating behavior in a Mediterranean wrasse, Symphodus ocellatus

Dynamic games and field experiments examining intra- and intersexual conflict: explaining counterintuitive mating behavior in a Mediterranean wrasse, Symphodus ocellatus

A trade-off generated by sexual conflict: Mediterranean wrasse males refuse present mates to increase future success

A variety of mechanisms, including intrasexual competition, intersexual conflict, and physiological constraints, can explain patterns of reproduction and the adaptive value of specific behaviors. In a Mediterranean wrasse, Symphodus ocellatus (Labridae), large, nesting males occasionally refuse to spawn with willing females in the presence of small, sneaker males. We explored the possible adaptive significance of this behavior. Nesting males refuse females despite the fact that it reduces their immediate mating success. This nesting-male behavior also decreases female and sneaker mating success and occurs when sneaker males surround the nest. Experiments that decreased the number of sneakers around nests showed that nesting males respond immediately to mating opportunities when fewer sneakers are present, and thus they are not simply constrained by a lack of energy or lack of sperm. Experiments that increased the number of sneakers at the nest caused nesting males initially to refuse spawning opportunities, followed by a subsequent decrease in sneaker presence and an increase in mating rate. We propose that this behavior is the result of a trade-off between immediate mating success and future reproduction created by competition between males and conflict between the sexes. Males reduce their immediate mating success by reducing spawning at the nest; sneaker males subsequently leave, and this decreases mate competition for the nesting male. Unresponsiveness of nesting males also causes sexual conflict between females and nesting males over mating. We argue that this behavior and the existence of a trade-off can only be understood by examining intersexual conflict and intrasexual competition simultaneously. Key words: mating systems, Mediterranean wrasse, reproductive behavior, reproductive trade-off, sexual conflict, Symphodus ocellatus. [Behav Ecol 10:105‐111 (1999)]