Marcel Haesler - Academia.edu (original) (raw)

Papers by Marcel Haesler

Proceedings of the Royal Society B: Biological Sciences, 2005

Female mate choice has often been proposed to play an important role in cases of rapid speciation... more Female mate choice has often been proposed to play an important role in cases of rapid speciation, in particular in the explosively evolved haplochromine cichlid species flocks of the Great Lakes of East Africa. Little, if anything, is known in cichlid radiations about the heritability of female mating preferences. Entirely sympatric distribution, large ecological overlap and conspicuous differences in male nuptial coloration, and female preferences for these, make the sister species Pundamilia pundamilia and P. nyererei from Lake Victoria an ideally suited species pair to test assumptions on the genetics of mating preferences made in models of sympatric speciation. Female mate choice is necessary and sufficient to maintain reproductive isolation between these species, and it is perhaps not unlikely therefore, that female mate choice has been important during speciation. A prerequisite for this, which had remained untested in African cichlid fish, is that variation in female mating preferences is heritable. We investigated mating preferences of females of these sister species and their hybrids to test this assumption of most sympatric speciation models, and to further test the assumption of some models of sympatric speciation by sexual selection that female preference is a single-gene trait. We find that the differences in female mating preferences between the sister species are heritable, possibly with quite high heritabilities, and that few but probably more than one genetic loci contribute to this behavioural speciation trait with no apparent dominance. We discuss these results in the light of speciation models and the debate about the explosive radiation of cichlid fishes in Lake Victoria.

Molecular Ecology, 2010

Major environmental events that fragment populations among multiple island habitats have potentia... more Major environmental events that fragment populations among multiple island habitats have potential to drive large-scale episodes of speciation and adaptive radiation. A recent palaeolimnological study of sediment cores indicated that Lake Malawi underwent major climate-driven desiccation events 75,000-135,000 years ago that lowered the water level to at least 580 m below the present state and severely reduced surface area. After this period, lake levels rose and stabilized, creating multiple discontinuous littoral rocky habitats. Here, we present evidence supporting the hypothesis that establishment and expansion of isolated philopatric rock cichlid populations occurred after this rise and stabilization of lake level. We studied the Pseudotropheus (Maylandia) species complex, a group with both allopatric and sympatric populations that differ in male nuptial colour traits and tend to mate assortatively. Using coalescent analyses based on mitochondrial DNA, we found evidence that populations throughout the lake started to expand and accumulate genetic diversity after the lake level rise. Moreover, most haplotypes were geographically restricted, and the greatest genetic similarities were typically among sympatric or neighbouring populations. This is indicative of limited dispersal and establishment of assortative mating among populations following the lake level rise. Together, this evidence is compatible with a single large-scale environmental event being central to evolution of spatial patterns of genetic and species diversity in P. (Maylandia) and perhaps other Lake Malawi rock cichlids. Equivalent climate-driven pulses of habitat formation and fragmentation may similarly have contributed to observed rapid and punctuated cladogenesis in other adaptive radiations.

Journal of Heredity, 2012

Divergent lateral plate phenotypes in stickleback represent one of only a few cases known, where ... more Divergent lateral plate phenotypes in stickleback represent one of only a few cases known, where a single gene underlies the phenotype under divergent selection between different habitats. However, the selection pressures leading to the repeated loss of lateral plates in freshwater are still not well understood. By genotyping 838 individuals from 9 independently colonized lakes and 1 marine population in Iceland, we found 1) that only in some lakes are phenotypes associated with the expected genotype and 2) that the independent repeated occurrence of a rarely described plate phenotype is expressed in the absence of an allele that is usually associated with this phenotype. This suggests that either other genes such as modifiers might be under divergent selection between lakes or that lateral plate expression in these populations is restricted due to environmental constraints.

Journal of Fish Biology, 2010

The evolutionary origin of the only north-west Saharan haplochromine cichlid, Astatotilapia desfo... more The evolutionary origin of the only north-west Saharan haplochromine cichlid, Astatotilapia desfontainii, was explored using mitochondrial DNA sequences. Phylogenetic analyses revealed that this species belonged to the main East African-Nilotic haplochromine clade, but was a distinct lineage that diverged from modern haplochromines in the Pliocene. The results suggest that A. desfontainii is a relict haplochromine lineage that has endured major climate fluctuations in North Africa.

Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, 2006

In many haplochromine cichlid fish, male nuptial coloration is subject to female mate choice and ... more In many haplochromine cichlid fish, male nuptial coloration is subject to female mate choice and plays a central role in the evolution of reproductive isolation between incipient species. Intraspecific variation in male coloration may serve as a target for diversifying sexual selection and provide a starting point for species divergence. Here, we investigated a polychromatism in Neochromis omnicaeruleus, a haplochromine from Lake Victoria, East-Africa. In this species, male coloration ranges from skyblue to yellow-red and females are grey-blue to yellow. We found that both genetic and environmental factors influence the expression of these colours during individual development. In a natural population, we found that male colour was associated with size and sexual maturity: yellow males were smaller than blue males and tended to be sexually immature. In females, size and maturity did not differ between colour types. Laboratory crosses revealed that there is a heritable component to the observed colour variation: yellow parents produced more yellow offspring than blue parents. Together with repeated aquarium observations of yellow individuals that gradually become blue, these data suggest that yellow males change to blue as they approach sexual maturity, and that the occurrence and timing of this transition is influenced by both environmental and genetic effects. The significance of this mechanism of colour expression as a possible target for divergent selection remains to be evaluated.

Journal of Evolutionary Biology, 2008

Evolutionary Ecology, 2012

The repeated colonization of freshwater habitats by the ancestrally marine threespined sticklebac... more The repeated colonization of freshwater habitats by the ancestrally marine threespined stickleback Gasterosteus aculeatus has been associated with many instances of parallel reduction in armour traits, most notably number of lateral plates. The change in predation regime from marine systems, dominated by gape-limited predators such as piscivorous fishes, to freshwater habitats where grappling invertebrate predators such as insect larvae can dominate the predation regime, has been hypothesized as a driving force. Here we experimentally test the hypothesis that stickleback with reduced armour possess a selective advantage in the face of predation by invertebrates, using a natural population of stickleback that is highly polymorphic for armour traits and a common invertebrate predator from the same location. Our results provide no compelling evidence for selection in this particular predator-prey interaction. We suggest that the postulated selective advantage of low armour in the face of invertebrate predation may not be universal.

Evolution, 2010

In many animals, sexual selection on male traits results from female mate choice decisions made d... more In many animals, sexual selection on male traits results from female mate choice decisions made during a sequence of courtship behaviors. We use a bower-building cichlid fish, Nyassachromis cf. microcephalus, to show how applying standard selection analysis to data on sequential female assessment provides new insights into sexual selection by mate choice. We first show that the cumulative selection differentials confirm previous results suggesting female choice favors males holding large volcanoshaped sand bowers. The sequential assessment analysis reveals these cumulative differentials are the result of selection acting on different bower dimensions during the courtship sequence; females choose to follow males courting from tall bowers, but choose to engage in premating circling with males holding bowers with large diameter platforms. The approach we present extends standard selection analysis by partitioning the variances of increasingly accurate estimates of male reproductive fitness and is applicable to systems in which sequential female assessment drives sexual selection on male traits. K E Y W O R D S : Cichlids, extended phenotype, Lake Malawi, leks, mate choice, selection analysis.

Behavioral Ecology, 2005

Lekking males are thought to face strong directional selection on secondary sexual traits. How va... more Lekking males are thought to face strong directional selection on secondary sexual traits. How variation in male traits can persist under these conditions remains problematic (the lek paradox). Here, we present several game-theoretic models that show that avoidance of costly and mobile predators, sneakers, or brood parasites (enemies) leads to variation in female choice. This can result in maintenance of variation in male quality. ''Enemies'' will congregate around higher quality males. Females must then trade-off the benefits of mating with high-quality males against the increased risk of enemies. At equilibrium, the models predict a positive correlation between the quality of a male and the proportions of both enemies and females visiting him. In the first model, we use this framework to predict the lowest quality male on the lek that will receive any matings. In the second model, we examine the influence of this female-enemy game on the maintenance of variation in male quality. Low-quality males are likely to persist when enemies are costly to females or occur at high density, and when there is some spatial structure on the lek, so that neighboring males are typically of similar quality. If enemies are more costly to males than to females, high-quality males may benefit from receiving fewer female visits. In the third model, we consider the special case when enemies are male reproductive parasites. These models illustrate the importance of considering the simultaneous decisions of multiple players in mate choice games.

Behavioral Ecology, 2009

In many animals, males congregate in leks that females visit for the sole purpose of mating. We o... more In many animals, males congregate in leks that females visit for the sole purpose of mating. We observed male and female behavior on 3 different-sized leks of the bower-building cichlid fish Nyassachromis cf. microcephalus to test predictions of 3 prominent lek models: the ''hotshot,'' ''hot spot,'' and ''female preference'' models. In this system, we were able to refine these predictions by distinguishing between indirect mate choice, by which females restrict their set of potential mates in the absence of individual male assessment, and direct mate choice, by which females assess males and their territories through dyadic behavioral interactions. On no lek were males holding central territories favored by indirect or direct mate choice, contrary to the prediction of the hotshot model that leks form because inferior males establish territories surrounding hotshot males preferred by females. Average female encounter rate of males increased with lek size, a pattern typically interpreted as evidence that leks form through female preference for lekking males, rather than because males congregate in hot spots of high female density. Female propensity to engage in premating behavior once courted did not increase with lek size, suggesting female preference for males on larger leks operated through indirect choice rather than direct choice based on individual assessment. The frequency of male-male competitive interactions increased with lek size, whereas their foraging rate decreased, implying a cost to males maintaining territories on larger leks. Together these data most strongly support the female preference model, where females may benefit through indirect mate choice for males able to meet the competitive cost of occupying larger leks.

Behavioral Ecology, 2011

The fertilization mode determines which sex has greater control over the offspring's sires. With ... more The fertilization mode determines which sex has greater control over the offspring's sires. With internal fertilization, females can strongly influence the chances of different males' ejaculates to fertilize their eggs by the postmating sexual selection process referred to as cryptic female choice. In contrast, when fertilization is external and multiple males compete in this process, the outcome of pre-and postmating sexual selection is largely determined by the competitive quality of males and their sperm. Intermediate modes of fertilization as found in mouthbrooding fishes might allow for a greater maternal influence on her offspring's sire. Here, we show that in the maternal mouthbrooder Ophthalmotilapia ventralis, females collect sperm from different males in their mouth, and males can successfully fertilize eggs even if the female did not lay eggs with them. In the field, 25 of 30 clutches had multiple sires, and the fertilization success was significantly biased toward particular males in most clutches. A mate choice experiment revealed that females prefer to spawn with males possessing strongly elongated pelvic fins, a conspicuous secondary sexual character of males in this cichlid. Additionally, the body length of males partly explained their success in sperm competition within the females' mouth, a factor without apparent influence on female choice of partners with which to lay eggs. Hence, successful sires are determined by a 2-step process that is largely under female control; females select which males to spawn with and from which males they collect additional ejaculates for the subsequent sperm competition in their mouth.

Copeia, 2008

Haplochromine cichlid fish have radiated into hundreds of species in East-African lakes, possibly... more Haplochromine cichlid fish have radiated into hundreds of species in East-African lakes, possibly driven by divergent sexual selection on body coloration. We studied the color polymorphic Lake Victoria cichlid Neochromis omnicaeruleus, in which a presumably ancestral phenotype with blue males and brown females co-occurs with two distinct classes of blotched phenotypes in both sexes. Similar blotch polymorphisms occur in other haplochromine species, and in all studied cases blotched females are much more common than blotched males. In N. omnicaeruleus, the near absence of blotched males seems to be partly due to genetic linkage to a dominant female determiner that turns blotched males into females. However, laboratory breeding suggests that blotched males should be much more common than observed. Here we studied whether differential predation on blotched males contributes to their scarcity. First, in a predation experiment with wild birds, blotched fish indeed incurred more predator attacks. Second, underwater observations revealed behavioral differences between the sexes, consistent with an additional predation risk for males. These data suggest that differential predation with regard to color pattern and sex may be an important selective force in the evolution and maintenance of this color polymorphism. However, we also carried out a population census which revealed that blotched males were rare already as juveniles. To explain the scarcity of blotched males in nature, we therefore have to invoke either selection against blotched males early in life, or a more complex genetic model. These results emphasize the need for further research on the ecology and genetics of this widespread color polymorphism in cichlid fish.